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MSE 313 Spring 2011 University of Washington Materials Science and Engineering MSE-‐313 (2011) Integrated Junior Lab 3 (2 credits) Instructor: Fumio S. Ohuchi, #312 Roberts, 685-‐8272, [email protected] Catalog description: Mechanical properties related laboratory experiments, including stress-‐strain behavior of materials and elastic modulus of materials, effect of work hardening on stress strain behavior, and effect of surface condition of the strength of glass. Electrical properties of materials. Screen printing techniques and Impedance spectroscopy Offered: Sp. Instructor’s Description: This course is designed to introduce the student to the basic hands-‐ on skills of laboratory experimentation and techniques used in evaluating the physical properties of the three major classes of materials (metals, ceramics, and polymers) and help the student to develop good report writing skills and Lab notebook maintenance. This course addresses the use and instruction of shop and analytical equipment, library resources for reference and literature searches, laboratory report writing, laboratory notebook recording, and data analysis. Class Schedule: Two-‐three hours laboratory sessions weekly. 2011 Spring: Tuesday and Thursday Session A 9:30-‐12:30 and Session B 2:30-‐5:30 See attached schedule TA’s: Aaron Lichtner Evan Uchaker Matthew Leung Kwangsuk Park Lab Manager Tuesday Kuykendall MUE 156 221-‐2678 Prerequisites: None Textbook and Other Required Materials: 1. Laboratory & Course Handouts, MSE 313 Course Packet, University of Washington, Seattle 2. William D. Callister, Jr., Materials Science and Engineering an Introduction, 6th Edition. 1 MSE 313 Topics Covered: Spring 2011 See lab content described in separate sheet (attached) Information Page: Prof. Ohuchi 425-‐941-‐6865 (Cell) 206-‐685-‐8272 (office) Aaron Lichtner Evan Uchaker Matthew Leung Kwangsuk Park Tuesday Kuykendall 425-‐773-‐2825 [email protected] [email protected] [email protected] [email protected] [email protected] [email protected] MSE Main Office 206-‐549-‐2600 MSE FAX 206-‐543-‐3100 MSE Dept. Address: Roberts Hall 302 Box 352120 Seattle, WA 98195 MSE Web Page: http://depts.washington.edu/mse/ Mechanical Engineering Student Machine Shop: Kevin Soderlund (Lead) [email protected] Eamon McQuaide (technician) [email protected] Mechanical Engineering Main Office 206-‐543-‐5090 2 MSE 313 Spring 2011 Course Objectives (Student outcomes) At the end of this course, the students will be able to: • Students will become familiar with the uses and capabilities of standard shop and laboratory analytical equipment and understand the safety requirements in these environments. • Students will learn the essential skills of good report writing and proper laboratory notebook documentation • Students will be able to efficiently search the library resources for handbook and process information as well as bibliographic references. • Making students aware of the resources available at the Engineering Writing Center to enhance the student’s ability to write quality laboratory reports. • Students will learn and gain the skills of sample preparation, from basic cutting, grinding, mounting, and polishing to more advanced acid/thermal etching and sputter coating. • Students will be able to make precise temperature measurement utilizing thermocouple technology for process control. • Students will be able to identify the trends in density, hardness, and thermal conductivity for metals, ceramics, and polymeric materials. • Students will learn the use and function of a standard X-‐ray diffractometer and proper powdered XRD sample preparation and be able to analyze single and multi-‐ component materials. • Students will be able to grow single crystals from saturated solution method, and be able to control the growth process. • Students will be able to use the standard optical microscope for analyzing grain size in metals and ceramics through digital image capture and analysis. • Students will be able to apply the knowledge and hands on skills in this laboratory coursework to advanced processing and characterization techniques in MSE 313 and 313 as well as senior research projects. Evaluation: Grade will be based on two full lab reports, project updates, project report and project presentation. Feedback: Anonymous student evaluations (College of Engineering) Individual evaluation of items described in course objectives. 3 MSE 313 Spring 2011 MSE Laboratory Policies 1. The use of cellular phones, pagers, and other communication devices is prohibited. 2. Laboratory sessions are mandatory; otherwise the student will get a zero grade for the lab report. Makeup labs will be given only for pre-‐arranged, excused absences. Students must contact the instructor before the absence. The only exception to the rule is absence due to illness. 3. If a student is unexpectedly detained and unable to make arrangements, she/he should make every attempt to notify the TA via phone or email. Students are expected to be on time for laboratory sessions. For every 10 minutes a student is late 10% of the lab grade will be deducted. If a student fails to show up after 30 minutes they will be issued a zero grade at the discretion of the instructor. Students are expected to be on time for laboratory sessions. Any student more than 15 minutes late without notice (phone, e-‐mail, and any other means) will have seriously deducted from the grade of their laboratory report for that rotation. Try to avoid this situation. 4. The checking of email or surfing the web in the computer lab is not permitted during the laboratory session unless instructed to do so for lab information. Doing so could result in a grade reduction. 5. Given the quantity of students in each lab section, students are not permitted to attend a morning lab section if they are enrolled in an afternoon lab section or vice versa. 6. Safety glasses are required for all laboratory experiments so do not show up without them. 7. Lab coats are required at all times in MUE 165, 166, and 167. They can be purchased at the bookstore. Students are responsible for their cleaning and maintenance. 8. All laboratory reports shall be type written, there are no exceptions. 9. Cheating (e.g. the unauthorized copying of another persons’ laboratory write-‐up, un-‐ cited material from the internet or other sources) will be referred to the Dept. Chair for further action. 10. Absolutely no food or drink in the laboratory at all times. 11. Laboratory reports are due at the beginning of class at 9:30 AM for the morning lab section and 2:30 PM for the afternoon lab section. No late assignments will be accepted unless prearranged through the instructor. 4 MSE 313 Spring 2011 Detailed Guidelines for Formatting a Laboratory Report • Cover page (see next page) • Margins: Left, right, top and bottom: 1 inch • Text: Justified on both sides • Spacing: 1.5 • Figures and tables: Left aligned along with the figure captions and table headings Figure 1: Figure titles go below the figure Table 1: Table titles go above the table • All pages should be numbered sequentially starting from cover page. All footnotes should be numbered sequentially • Hindu-‐Arabic numerals (1, 2, 3) should be used for numbering of tables. • No color text, graphs should be drawn with black color on white, background. The only exception is color pictures or figures from lab handout. • 12 point Arial or Times New Roman font should be used for text as well as for Figure captions and table headings. • The title should be in 14 point bold • All section and sub-‐section headings should be in bold. • All sections should be numbered starting from Introduction: 1. Introduction If there are sub-‐sections, 1.1, 1.2, etc. Further sub-‐sections, .............................. 1.1.1,1.1.2, ... and 1.2.1,1.2.2, , etc 2. Experimental procedure For sub-‐sections, follow the same format as introduction section 3. Results and Discussion For sub-‐sections, follow the same format as introduction section 4. 4. Conclusions and recommendations 5. References 6. Appendices 5 MSE 313 • Spring 2011 Appendix-‐A, Appendix-‐B, Appendix-‐C, etc. The arrangement of various sections in the lab report should be as follows: Cover page with abstract Introduction Experimental procedure Results and Discussion (includes graphs and tables) Conclusions and Recommendations References Appendices (if there are any) Answers to questions • • Suggestions for improvement Page breaks: after cover page, after experimental procedure, and before Appendices. Expected length of the report: Min. 10 pages, buy not exceeding 15 pages. 6 MSE 313 Spring 2011 MSE-‐311 Integrated Junior Lab Laboratory Report Laboratory-‐ Rotation # Name Student # Group-‐ Members: TA Date Abstract 7 MSE 313 Spring 2011 MSE 311 Lab Report Grading Criteria MSE 313 Lab-III Report Grading Criteria Cover Page (Use Cover Page template) Abstract 5 ____ • Purpose: Brief introduction to the problem • Scope: Identifies experimental approach (materials, variables, equip., etc.) • Experimental results are given (numeric when possible) • Significant conclusions are reported Introduction 5 ____ • Introductory statement: General statement of the problem • Technical background: Summary or discussion of historical and/or technical background as a foundation for present test • Purpose(s) of the present test and the report (different from the Abstract) Experimental Procedure 5 ____ • Schematic or diagram of experimental setup • Describe the procedure used for conducting tests or experiments • Various characterization methods used • Variables effecting the measurement and their ranges (capacities, sizes, etc.) Results and Discussion 40 ____ • Order of presentation is logical • Computations are complete and correct (sample calculations cited) • Data reduction is presented in tabular or graphical form (% difference, % error, etc.) Same data do not appear in both tables and graphs (unless in Appendix) • Data is interpreted correctly, is validated and compared to published work • Good comprehension is shown of the relative meaning and importance of the results (trends are cited, averages, extremes, %change, etc.) • Discussion should concentrate on test results and correlation with analysis; no comments on test technique, lost data, etc. • Error analysis is performed, deviation from expected results is discuss Conclusions and Recommendations 5 ____ • Conclusions are presented in a numbered list • Most important conclusions are given first • Conclusions are drawn only from the body of the report • Recommendations for future studies based on conclusions Graphs. Tables. and Figures (should be a part of results and discussion) 5 ____ • Choice of information to be graphed tabulated, or illustrated is relevant and logically 8 MSE 313 • • • • Spring 2011 presented Cited and clearly explained in the appropriate sections Data are correctly transcribed into tables from data sheets Graphs are labeled, have proper scaling, and error bars (when applicable) Format is correct and appropriate: Graphs and Figures captioned (example, Figure 2, Average grain size in…), tables are titled (Table IV... Green densities of) References 5 ____ • References are cited in the text (superscript # or [#] end of sentence) • References are presented in a numbered list in the order of citation • Proper format is used for each reference Answers to Questions in the Lab and Suggestions for Improvement 5 ____ • Answers to questions should be included in this section not in the body of the lab unless otherwise indicated • Suggestions on how to improve the laboratory next time through focusing on any problems that were encountered in the lab • Should be different from Recommendations Appendices 5 ____ • • • • Arranged in order of citation in the text (A, B, C, etc.) Raw data sheets from the tests are presented Sample calculations and data reductions are included Should begin on a separate page Overall arrangement and coordination • General arrangement of ideas is logical, clear and consistent • Grammar, sentence, and paragraph structure are good • Spelling errors are absent, paper has been proof-‐read • Page composition is appropriate, neat and pleasing • Units defined for sample calculations, tables, graphs, etc. 20 ____ Total 100 ____ 9 MSE 313 Spring 2011 How to use this manual: Reading the lab manual before lab is required. Some labs may include a pre-‐lab quiz so it pays to be prepared. The manual is arranged by labs with a brief overview in the introduction. There is a page that has important contact information. Use the information if you cannot make it to lab for any reason. Important terms throughout the document are in italic. If any term (in italics or not), is new to you, you are responsible for looking it up. There are a number of references to ASTM standards throughout the manual. You are responsible for looking up the standard at the library. In the introduction next, there are brief descriptions of each lab followed by a list of information that should be included in your lab write-‐up. A number of the sections in this lab manual are excerpted from a variety of sources and are cited where relevant. Students are encouraged to look up these sources to gain more in-‐depth understanding of the subjects presented. Whenever possible electronic copies of sources are included in a folder on the desktops of the Jr. lab computers. To the best of the knowledge of the editors of this manual, no copyrighted materials are used without permission. 10 MSE 313 Spring 2011 MSE 313 Integrated Junior Laboratory (2011 Spring) Lab-‐I. Mechanical Properties of Materials: Part 1A: Tensile Testing of Metals, Composites and Plastics The purpose of this laboratory is to determine tensile strength, elastic modulus, fracture strength, ductility and energy to fracture of metals, composites, and plastics in tension using a mechanical testing apparatus (Instron corporation, model no: 5500R). Part 1B: Compression Testing and Elastic modulus measurement The purpose of this laboratory is to measure yield strength, yield point, compressive strength and elastic modulus under compressive loading, and also to measure the elastic modulus by impulse excitation technique. Part 1C: Fracture Toughness Testing of Metallic Materials The purpose of this laboratory experiment is to determine fracture toughness of a material defined as a measure of the material’s resistance to crack propagation. Part 2: Ductile to Brittle Transition of Metals The purpose of this laboratory experiment is to demonstrate the effect of temperature on the fracture behavior of materials using the impact tester and Charpy impact specimens. Part 3: Fractography (SEM ) The purpose of fractography is to analyze fracture surfaces by SEM, and to relate the fracture surface features to the cause(s) and basic mechanisms of fracture. Lab-‐II. Electrical Properties of Materials: Part 1: Electrical Resistivity of Metal Material : The purpose of this laboratory is to measure the electrical conductivity (resistivity) of selected conductors, insulators and semiconductors. This lab is designed to help the student understand how the electrical conductivity is related to temperature, alloying, permanent deformation and impurities. Part 2: Energy Gap in Semiconductors: The purpose of this lab is to measure temperature dependence of the electrical conductivity in a semiconductor sample. The energy gap will be calculated from data taken in an intrinsic region, and the temperature dependence of the majority carrier mobility will be deduced from measurements taken in the extrinsic region. 11 MSE 313 Spring 2011 Part 3: Terminal Device Characteristics and Diode Characterization: The objectives of this experiment are to learn methods for characterizing 2-‐ terminal devices, such as diodes, observe some fundamental trends in the characteristics of various diode types, and to gain some familiarity with standard test bench instrumentation. Lab-‐III. Screen Printing of Thick Film Materials and Impedance Spectroscopy: Part 1: Print/Dry/Fire Conductor The purpose of this laboratory is to screen print, dry and fire thick film circuits made of conductive ink. This lab is designed to introduce students to the technology of printing thick film and hybrid circuit using a screen printing machine. The fundamentals of the equipment, inks, and thick film materials processing will be explored. Part 2: Print/Dry Resistor The purpose of this laboratory is to screen print and dry thick film resistors. This lab is designed to allow practice screen and stage alignment to obtain patterns at precise locations on the substrates. Part 3: Firing Profiles/ Resistance Measurements / Pattern Design Principles The purpose of this laboratory is to fire thick film resistors. This lab is designed to obtain and study different firing cycles of the resistors and to determine the effect of firing temperatures on the resistors’ performance. Students will also study aspects of thick film design and layout. The students will examine the patterns of printed/fired thick film circuits obtained from Part 1 and 2. Factors such as geometry, sheet resistance, print thickness and electrical performance will be studied and students will compare calculated theoretical results with the experimental data. Jr. Lab Project The purpose of the Jr. Lab Projects will be to expose students to the various challenges involved in laboratory experimentation Each group will be expected to design, set-‐up, and implement a lab project. Six full lab sessions will be available. 12 MSE 313 Spring 2011 MSE 313 2011 Schedule Mon Tue Wed Thu Fri Mar 28 29: All Attend: Orientation 30 31 Rotation 1 Day 1 Apr 1 4 5 Rotation 1 Day 2 6 7 Rotation 1 Day 3 8 11 12 Rotation 2 Day 1 13 14 Rotation 2 Day 2 15 18 19: Rotation 2 Day 3 20 21: COE Discovery Days Prep 22: COE DD 25 26 Rotation 3 Day 1 27 28 Rotation 3 Day 2 29 May 2 3 Rotation 3 Day 3 4 5 Rotation 4 Day 1 6 9 10 Rotation 4 Day 2 11 12 Rotation 4 Day 3 13 16 17 Rotation 5 Day 1 18 19 Rotation 5 Day 2 20 23 24 Rotation 5 Day 3 25 26 Open for project prep 27 30 31: Project Presentations June 2: Project Presentations 1 3 Finals Week Finals Week 13 MSE 313 Spring 2011 Lab 1: Mechanical Properties Lab 2: Screen Printing Lab 3: Electrical Properties Lab 4: Project Lab 5: Project Groups R1 R2 R3 R4 R5 1 & 2 Lab 1 Project Lab 2 Lab 3 Project 3 & 4 Lab 2 Project Lab 3 Project Lab 1 5 & 6 Lab 3 Lab 1 Project Lab 2 Project 7 & 8 Project Lab 2 Project Lab 1 Lab 3 9 & 10 Project Lab 3 Lab 1 Project Lab 2 14 MSE 313 Spring 2011 Blank Page 15 MSE 313 Spring 2011 MSE 313 Integrated Junior Laboratory -‐I Mechanical Properties of Materials Part 1A: Tensile Testing of Metals, Composites and Plastics The purpose of this laboratory is to determine tensile strength, elastic modulus, fracture strength, ductility and energy to fracture of metals, composites, and plastics in tension using a mechanical testing apparatus (Instron corporation, model no: 5500R). Part 1B: Compression Testing and Elastic modulus measurement The purpose of this laboratory is to measure yield strength, yield point, compressive strength and elastic modulus under compressive loading, and also to measure the elastic modulus by impulse excitation technique. Part 1C: Fracture Toughness Testing of Metallic Materials The purpose of this laboratory experiment is to determine fracture toughness of a material defined as a measure of the material’s resistance to crack propagation. Part 2: Ductile to Brittle Transition of Metals The purpose of this laboratory experiment is to demonstrate the effect of temperature on the fracture behavior of materials using the impact tester and Charpy impact specimens. Part 3: Fractography (SEM training) The purpose of Fractography is to analyze fracture surfaces by SEM, and to relate the fracture surface features to the cause(s) and basic mechanisms of fracture. 16 MSE 313 Spring 2011 Part 1A: Tensile Testing of Metals, Composites and Plastics: Objectives: The purpose of this laboratory is to determine the mechanical properties such as tensile strength, elastic modulus, fracture strength, ductility and the energy to fracture of metals, composites, and plastics in tension using a mechanical testing apparatus (Instron corporation, model no: 5500R). READ ASTM E8 AND D638 STANDARDS BEFORE THE LAB Introduction: The Tensile Test is a common standard test which is simple to conduct and is a valuable method of determining important mechanical properties of engineering materials. A thorough understanding of a material's properties is required by the engineer if failures are to be avoided. The procedural details of the test vary for different material types, but tensile tests are generally conducted at room temperature at relatively slow loading rates although various temperatures and loading rates may be required for the determination of material behavior under specific conditions. The output of a standard tensile test is load versus displacement data. Since load-‐ displacement characteristics are dependent on specimen size, for example, it will require twice the load to produce the same elongation if the cross-‐sectional area of the specimen is doubled, load-‐displacement data is routinely converted to engineering stress-‐strain data. For axial loading, engineering stress, σ, is defined by the well known relationship, σ = P/Ao Equation 1Ai Where P is the instantaneous load applied perpendicular to the specimen cross-‐section, in Newton’s (N), and Ao is the original cross-‐sectional area of the specimen before any load is applied (m2). The units of stress are generally mega Pascal’s (MPa). Engineering strain, ε, along the loading axis of an uniaxial loaded sample is defined as, ε = ΔL/L Equation 1Aii Where engineering strain, ε (mm/mm), is determined by dividing the change in gauge length, ΔL (mm), by the original length of the specimen, L (mm). Engineering strain is unit less, but inches per inch or meters per meter are often used; the value of strain is clearly independent of the units system applied! Strain may also be expressed as a percentage, in which case the strain value is multiplied by 100. In Tensile Testing, the test specimen is deformed, usually until complete fracture occurs, with a gradually applied increasing tensile load that is applied uniaxially along the long axis of the specimen. When a specimen is loaded beyond its' ultimate strength 17 MSE 313 Spring 2011 the cross-‐sectional area begins to decrease in a localized region instead of decreasing over its entire length creating a so called "neck.” Normally the test specimen is circular, but rectangular specimens can also be used. Each specimen is of a specific shape and the dimensions should be in accordance with ASTM (American Society for Testing and Materials) specifications for standardization. During testing, deformation is confined to the narrow center region, which has a uniform cross section along its length as shown in Fig. 1Ai. Figure 1Ai: Dog bone tensile testing specimens: (a) aluminum, (b) polymer, and (c) composite. By analyzing the stress-‐strain curve of a specific material that has been tested in tension, a number of mechanical properties of the material can be determined. The list of properties that can be determined from the stress-‐strain curves is given below. • Yield Strength (σys) -‐ Yield Strength is defined as the stress required to produce a specified amount of plastic deformation or permanent set (strain) in a material. Below the elastic limit, the stress-‐strain relationship in loading and unloading are identical for practical purposes. Therefore, it is not necessary to unload a specimen in order to determine the yield strength. Rather, a line parallel to the initial straight line portion of the curve is constructed. The parallel line is displaced from the origin of the curve by an amount equal to the specified permanent set. The stress at the intersection of the parallel line with the stress-‐strain curve is called as the yield strength. The offset most commonly used is 0.2% strain or 0.002 in/in or mm/mm. The yield strength is a practical measure of the limit of elastic action of a material. It is always greater than the elastic limit and is sensitive to measurement instrument precision. • Ultimate or Tensile Strength (σul) -‐ The Ultimate Strength, also referred to as the Tensile Strength, is calculated by dividing the maximum load sustained by the specimen by the original cross-‐sectional area of the specimen. • Fracture or Rupture Strength (σru) -‐ The Rupture Strength, also referred to as the Fracture Strength, is determined by dividing the load sustained at rupture by the 18 MSE 313 Spring 2011 original cross-‐sectional area of the specimen. This load will be less than the maximum load because the cross-‐sectional area of the specimen is reduced drastically after the maximum load is reached. The reduced cross-‐section has an "Hour-‐Glass" shape and the phenomenon of reduction in cross-‐section is called as Necking or Necking Down. • Modulus of Elasticity (E) -‐ The Modulus of Elasticity is a measure of material stiffness and is termed Young's Modulus for tensile loading. The Modulus of Elasticity, E, is the constant of proportionality between stress, σ, and strain, ε, at stresses below the proportional limit. The Modulus of Elasticity is found by measuring the slope of the straight-‐line portion of the stress-‐strain curve. • Toughness (UT) -‐ The toughness of a material refers to the ability of the material to absorb energy up to the point of rupture. The Modulus of toughness is determined by measuring the area under the stress-‐strain curve. This is not an exact indication of toughness because the specimen does not strain uniformly over its length, and hence does not absorb energy uniformly throughout its volume. The units of toughness are determined by multiplying stress with strain. • Percent Elongation (% EL) -‐ The Percent Elongation refers to the elongation at rupture and can be expressed as: % EL = 100 (ΔLT)/Lo where ΔLT represents total elongation; ΔLT = final length – original length (Lf -‐ Lo) • Percent Reduction in Area (% RA) -‐ The Reduction in Area refers to the reduction in cross-‐sectional area at rupture and can be expressed as: % RA =100 (ΔAT)/Ao where ΔAT represents total reduction in area; ΔAT = original cross-‐sectional area-‐ final cross-‐sectional area (Ao -‐ Af) • True Strain (εΤ)-‐ The True Strain is the change in length divided by the instantaneous length and can be simply determined as: εT= ln (ε + 1) • True Stress (σT) -‐ The True Stress is the applied load divided by the Instantaneous cross-‐sectional Area and can be simply determined as: σT = σ (ε + 1) For some materials (e.g., concrete, gray cast iron) the initial elastic portion of the stress-‐ strain curve is non-‐linear where it is impractical to determine a standard modulus of elasticity. Furthermore, the modulus of elasticity is restricted to the initial linear portion of a standard stress-‐strain diagram and is invalid beyond this region. For non-‐ linear behavior, either the Tangent or Secant Modulus is generally utilized. 19 MSE 313 Spring 2011 Experimental Procedure: • Samples of 6061 (T6 condition) aluminum alloy, carbon fiber composites and high-‐density polyethylene (HDPE) will be used for testing (Fig. 1A ii). • 6061 Al-‐alloy contains Mg and Si as major alloying elements and also contains Fe, Cu, Mn, Zn, Cr and Ti. T6 condition implies that the alloy has been solution heat treated and artificially aged. • One sample of each kind will be provided to each group. The elongation of the specimen will be obtained from two sources: crosshead displacement and extensometer (more accurate). • The TA(s) will explain about the procedure and precautions to be followed while loading and testing the samples. Each student will get a chance to involve himself/herself in loading the samples, setting up the software program for testing, and testing the samples. • The load vs. displacement data of the materials will be obtained as .TXT files and these files will be distributed to the students for analysis. Figure 1Aii: Tensile Instron set-‐up 20 MSE 313 Spring 2011 Things to be done before and after testing the samples: • Measure dimensions of the test specimen(s) [note; accurate and precise measurement of specimen dimensions is important] • For circular cross-‐section specimens: Gage length before and after testing, diameter before and after testing. • For rectangular cross-‐section specimens: Gage length before and after testing, width and thickness before and after testing. • It is always good to measure diameter, width and thickness at different locations along the gage length as they can be used for finding out the error bars while reporting the data. Part 1A References 1. G.E. Dieter, Mechanical Metallurgy, McGraw-‐Hill Inc., New York, 1986. 2. F.A. McClintock and A.S. Argon, Mechanical Behavior of Materials, Addison-‐ Wesley Inc., Reading, Mass., 1966. 3. Annual Book of ASTM Standards, Vol. 3.01, Standard E8, ASTM, Philadelphia, Pa. 2002. 4. Annual Book of ASTM Standards, Vol. 8.01, Standard D638, ASTM, Philadelphia, Pa. 2002. 21 MSE 313 Spring 2011 Part 1B : Compression Testing and Elastic modulus measurement: Objective: To measure the mechanical properties such as yield strength, yield point, compressive strength and elastic modulus under compressive loading Introduction: Mechanical property evaluation of materials under compressive loading is important in order to understand the performance of materials subjected to compressive loads. In some metal forming processes such as rolling and forging, materials undergo large plastic strains and there is a need to determine the yield stress of the materials under these severe conditions rather than those usually encountered in a normal stress-‐strain test. In a tensile test the sample starts necking at about a strain of 0.1(10%). However, in a metal working operation such as rolling, a material undergoes plastic strain of 2 (200%) to 4(400%). Determining the yield stress (the stress at which the material starts flowing plastically) over such a large range of strain is not feasible in the case of tension test. On the other hand, compression test does not suffer from necking problem and the test can be carried out to a strain in excess of 2 (200%) in the case of ductile materials. Materials and Equipment: 6061 Al-‐alloy solid cylinders Instron machine. Experimental Procedure: • ASTM standard E9 describes about compression testing of metallic materials. • Measure the sample diameter and mark the gage length by leaving about one diameter equivalent of length on each side of the sample. • Align the specimen properly so that the load line goes through the axis of the cylinder. The rate at which a sample is loaded is taken care by the pre-‐set program in the Instron machine. • The load versus displacement (contraction of the sample) data is displayed on the monitor and data file is stored in the computer attached to the Instron. • The change in shape of a compression test sample is shown in fig.1. The sample bulges outwards at the sides due to the friction between the sample and the platens of the Instron. The friction at the interface between the machine platens and the sample top and bottom surfaces make the material at these regions difficult to flow plastically whereas the material at the sides is not constrained. As a result, an initial cylinder becomes a barrel shaped object at the end of testing. Moreover, there are triangular regions (see 22 MSE 313 Spring 2011 Fig.1Bi) at the top and the bottom where the material does not deform due to friction. Precisely for this reason, a length equivalent to the diameter of the sample is left on each end. As a result, the deformation in the center most portion of the sample is uniform as it is not affected by the friction. Fig.1Bi: Schematic of compression test sample before (broken lines) and after the test. The shaded triangular regions at the top and the bottom are un-‐deformed regions due to friction. Smaller the sample (right side figure) greater the difficulty to deform as the un-‐deformed regions extend all the way into the center of the sample and almost touch each other (Ref.: George E. Dieter, Mechanical Metallurgy). Fig. 1Bii. Compression Instron set-‐up 23 MSE 313 Spring 2011 Part 1C: Fracture Toughness Testing of Metallic Materials Introduction Fracture toughness of a material is defined as a measure of the material’s resistance to crack propagation. The concept of fracture toughness or resistance to crack propagation has origins in linear elastic fracture mechanics. Cracks or flaws in a material concentrate (see Fig.1Ci) the applied stress and lead to the failure or fracture of the components and structures at much lower stresses than the design stress. If one intensifies the stress locally the stress intensification depends on the size of the crack and radius of curvature of the crack tip. The larger the crack length the higher the stress concentration (if design assumes that no flaws are present in the material). Fig. 1Ci: Elliptical hole in infinitely large panel produces stress concentration of 1+2a/b (Source: Reference 3) σmax/σa = (1+2 (sqrt(a/ρ)) Equation 1Ci where σmax= maximum stress at the end of major axis, σa = applied stress normal to the major axis, a= half major axis and ρ= radius of curvature (b2/a) Fracture can occur in three different modes as shown in Fig. 1Cii: Opening or tensile (Mode I), sliding or in-‐plane (Mode II) and tearing or out of plane mode (Mode III) depending on the way the cracked surface is displaced. 24 MSE 313 Spring 2011 Fig.1Cii: Basic modes of loading involving different crack surface displacements (Source: reference 3) The crack-‐tip stress field (based on elastic stress analysis) for each of the fracture modes is given by the following equations. Fig.1Ciii: Distribution of stresses in vicinity of crack tip (source: reference 3) K # # 3# cos (1+sin sin ) 2 2 2 2" r K # # 3# ! x= cos (1!sin sin ) 2 2 2 2" r K # # 3# $ xy= (sin cos cos ) 2 2 2 2" r ! y= As shown in the Fig.1Ciii, the above equations give the values of stress field ahead of the crack tip. As r approaches zero, the local stresses could rise to extremely high values. However, this situation is avoided by the plastic deformation of material at the crack tip 25 MSE 313 Spring 2011 when the stress at the crack tip exceeds the yield stress of the material (there will always be a region of plastic zone at the crack tip). K in the above equations is called stress intensity factor and is a measure of the magnitude of the crack-‐tip stress field. K = f(σ, a) Equation 1Cii The above equation states that K depends on the geometry of the cracked component and the manner in which the loads are applied to the component. The main difference between stress concentration and stress intensity factors is that the former takes into account the effect of crack size and crack-‐tip radius whereas stress intensity factor takes into account both the geometrical terms (crack length appears in the expression whereas the crack-‐tip radius is assumed to be sharp) and the stress level. Ideally, the crack should be atomically sharp. When the stress intensity factor exceeds a critical value called KIC, the crack propagation takes place. This critical value of stress intensity, which is a material property, is called fracture toughness. There are two scenarios that merit attention with regard to what happens to the plastic zone at the crack tip as a function of plate size. On one extreme, when the plate is too thin, the material at the crack tip is subjected to plane stress conditions and as a result the plastic zone size is larger than the thickness of the sample. Under these conditions, the fracture toughness of a material is dependent on the sample dimensions. On the other extreme, when the plate is too thick, plane strain conditions prevail and as a result the plastic zone size is relatively smaller and it is possible to reduce the plastic zone to be smaller than the smallest dimension of a fracture specimen by choosing a sample with larger dimensions. Therefore, by a proper choice of sample dimensions, it is possible to determine the fracture toughness of a metal under plane strain conditions which is independent of sample thickness and can be considered as material property. In this lab, plane strain fracture toughness testing of plain carbon steel and high speed tool steel samples will be carried out. ASTM standard E399-‐90 describes about various specimen geometries and pre-‐cracking procedures employed in plane strain fracture toughness testing of metallic materials. Three point bend test will be used to determine the fracture toughness of the samples in this lab. A schematic of three point bend test is shown in Fig.3. The pre-‐crack in the specimen is introduced by notching the sample and subjecting it to fatigue loading. In general, the stress level during fatigue loading (10 to 20% of the final stress level) is such that minimal damage of the microstructure takes place during pre-‐cracking. However, in the present lab, we will be using a notch without any pre-‐crack. The notch itself acts as a crack. The fracture toughness can be calculated using the following equation: KQ = ( PQ L hW )f( 3/ 2 d ) W Equation 1Ciii 26 MSE 313 Spring 2011 where, d d2 (2.15 ! 3.93( ) + 2.7( 2 )) d d 1/ 2 d d W W }] f ( ) = 3( ) [1.99 ! ( )(1 ! ){ d d W W W W 2(1 + 2( ))(1 ! ) 3 / 2 W W P W d P/ 2 L/ 2 L/ 2 P/ 2 d= W/2 Fig.1Civ: Schematic of single edge notched beam three-‐point bend test used for fracture toughness determination. Figure 1Cv: Three-‐point bend equipment for Instron 27 MSE 313 Spring 2011 Materials & Equipment: Plain carbon steel and high speed tool steel bars Instron machine Three point bend fixtures For the present lab, f(d/W)= 2.66 since d/W= 0.50 PQ = load (kN) h = Specimen thickness (cm) L = Span (cm) W = specimen depth (cm) d = crack or notch length (cm) The procedure followed in determining the load, PQ, will be described in the class. For more details on this topic, see calculations and interpretation of results section in ASTM standard E399. See AppendixA Part 2 References: (1) ASM handbook on metals, “Fractography”, 1986. (2) Annual Book of ASTM Standards, Vol 3.01, Standard E399-‐90, ASTM, Philadelphia, PA. 2002. (3) Richard W. Hertzberg, “Deformation and fracture of engineering materials”, 4th edition, John Wiley & Sons, Inc., 1996. 28 MSE 313 Spring 2011 Part 2: Ductile to Brittle Transition of Metals: Lab provided by Mechanical Engineering: Written by Paul Labossiere Read ASTM E-‐23 before the lab begins Appendix ME 354 MECHANICS OF MATERIALS LABORATORY NAME DATE MECHANICAL PROPERTIES AND PERFORMANCE OF MATERIALS: Part a) Charpy V-Notch Impact February 2004 PEL PURPOSE The purpose of this exercise is to obtain a number of experimental results important for the characterization of the mechanical behavior of materials. The Charpy V-notch impact is a mechanical test for determining qualitative results for material properties and performance which are useful in engineering design, analysis of structures, and materials development. EQUIPMENT • Charpy V-notch test specimens of 6061-T6 aluminum and 1018 (hot rolled) or A36 steel • Charpy testing machine with 800-mm long pendulum arm and 22.6-kg impact head • Type K thermocouple and digital readout unit • Beakers of room-temperature water, warm water and boiling water • Beakers of plain iced water • Cryo-beakers of salted iced water and super cold liquids PROCEDURE CAUTION: When using the Charpy testing machine, stand well clear of the swinging area of the pendulum both when the arm is cocked and for some time after the arm is released for a test while it is still swinging. Serious injury will result from a swinging pendulum arm. For each material repeat the following steps • Designate a person as the "operator" of the Charpy test machine: all other persons must stand clear during testing • Designate a person as the "monitor and recorder" of temperatures and impact energies • Designate a person as the "test specimen loader" who will remove test specimens from the liquid bath, quickly placing them on the test fixture of the Charpy testing machine • Designate a person as the "test specimen retriever" who will retrieve the broken halves of the test specimens, will bind the halves together and will mark the test temperature on each pair of specimen halves for later examination and inspection. Use the following procedure to conduct tests in the order shown after exposure to the preconditions to give the approximate test temperatures indicated: Room temperature water (20 to 25°C) Warm water (50-60 °C) Boiling water (95-100°C) Ice water (0 to 4°C) Salted ice water (-15 to -18°C) Acetone with some dry ice (-50 to -57°C) Acetone with much dry ice (-80 to -85°C) • Place the thermocouple probe in the appropriate liquid being sure to allow both the test specimens and the thermocouple to equilibrate for at least five minutes prior to testing. • Record the indicated temperature 29 MSE 313 Spring 2011 • "Cock" the pendulum by activating the "raise" mechanism and stand clear while the pendulum is held in the "cocked" position. • Using the tongs, quickly remove the test specimen from the bath and place it on the test fixture with the notch opening facing away from the direction of the cocked pendulum • Stand clear • Release the pendulum • Secure the pendulum in its rest position (i.e., hanging vertically) and retrieve the fractured specimen halves. • Record the impact energy (read directly from the dial on the Charpy testing machine) • Repeat these steps for the each temperature and each material. BACKGROUND AND ANALYSIS Static or quasi-static properties and performance of materials are very much a function of the processing of the material (heat treatments, cold working, etc.) in addition to design and service factors such as stress raisers and cracks. The behaviour of materials is also dependent on the rate at which the force is applied. For example, a polycarbonate tensile specimen which might show a relatively low yield point but up to 200% elongation at a low loading rate may show a much greater yield point but at only 5% elongation at an order of magnitude faster loading rate. Low carbon steels, such as 1018, may show considerable increases in yield strength and work hardening at high strain rates. In quasi-static tests, the amount of energy required to deform a material is determined from the area under the tensile stress-strain curve and is know as the modulus of toughness. Under dynamic loading, stress-strain response is typically not recorded. Instead, the transfer of energy from a device such as a drop weight or a swinging specimen to the deforming or breaking specimen is equated to the "impact energy." The Charpy impact test uses a standard Charpy impact machine to evaluate this impact energy. The machine consists of a rigid specimen holder and a swinging pendulum hammer for striking the impact blow to a v-notched specimen as shown in Figs. 1 and 2. Unfortunately, while the test, including machine and specimen geometry, has been standardized, the test results do not provide definitive information about material properties and thus are not directly applicable to design (as for example might be a yield strength); however, the test is useful for comparing variations in the metallurgical structure of materials and in determining environmental effects, such as temperature on the dynamic response of the material. One of the most dramatic results of Charpy impact tests is in the form of plots of impact energy versus temperature in which sigmoidally-shaped curves (see Fig. 3) show substantial decreases in some materials' abilities to absorb energy below a certain transition temperature. This ductile to brittle transition is most apparent in materials with BCC and HCP crystalline structures as for example in steels and titanium. A classic and dramatic example of this ductile to brittle behaviour is the low carbon steel Victory ships of WWII cracking in half under even the mild conditions of sitting at anchor in a harbor. Materials with FCC structures (e.g., aluminum and copper) have many slip systems and are more resistant to brittle fracture at low temperatures. In this laboratory exercise the primary outcome will be plots of impact energy versus temperature for two materials (FCC-606-T6 aluminum and BCC-1018 steel). Note the effects of temperature and material type on the levels and shapes of the curves. Examine the fracture surfaces of specimens and compare the type and degree of deformation to the impact energy and the corresponding temperature. Consider not only the type of material, but also the effect of notches and temperature in making design decisions. 30 MSE 313 Spring 2011 REFERENCE: Annual Book or ASTM Standards, American Society for Testing and Materials, Vol. 3.01 E23 Standard Test Methods for Notched Bar Impact Testing of Metallic Materials Figure 1. Schematic of Charpy Impact Testing and Izod and Charpy V-notch specimens Figure 2 Charpy V-notch specimen used in this laboratory showing dimensions Figure 3. Schematic of plot of impact energy versus temperature showing sigmoidal curve 31 MSE 313 Spring 2011 32 MSE 313 Spring 2011 Part 3: Fractography Objective The purpose of Fractography is to analyze fracture surfaces and to relate the fracture surface features to the cause(s) and basic mechanisms of fracture. Introduction Both visual examination and microscopic examination is used extensively to characterize the fracture surface features. Fractography is a valuable tool in identifying the mechanisms and causes of fracture of engineering components. Fracture of any material can be broadly classified into two main categories: ductile and brittle. Any material which fails after experiencing significant plastic deformation is called ductile whereas any material failing without appreciable plastic deformation is called brittle. In addition to these two broad classifications, a range of intermediate fracture modes are possible between ductile and brittle fracture behavior. In this lab we will be analyzing the fracture surface topography of the metallic and polymeric samples tested in the previous labs, using optical and scanning electron microscopes in addition to visual examination. We will also examine how scanning electron microscope has become an indispensable instrument in understanding the causes and mechanisms of failure of engineering components. Materials and Equipment: SEM Metallic and polymeric fracture samples from tension, MOR, Charpy and fracture toughness labs will be examined with the department SEM. Part 3 References: (1) ASM handbook on metals, “Fractography”, 1986. (2) Annual Book of ASTM Standards, Vol 3.01, Standard E399-‐90, ASTM, Philadelphia, PA. 2002. (3) Richard W. Hertzberg, “Deformation and fracture of engineering materials”, 4th edition, John Wiley & Sons, Inc., 1996. 33 MSE 313 Spring 2011 Lab 1 Questions and Discussion: (Note: Don’t forget to include questions, data, discussion from part 2) • Prepare plots of Load vs. Displacement, Engineering Stress vs. Engineering Strain, and True Stress vs. True strain for each of the specimens provided. • Determine the following for the samples tested in a comparative chart: 0.2% offset Yield Strength, Ultimate Strength, Rupture Strength, Modulus of Elasticity, Modulus of Toughness, Percent Elongation, and Percent Area Reduction. Also include available literature values and compare your data with literature values. Your results must be presented in SI units. • Why are ceramics not tested in a manner similar to metals? • Find out the fracture toughness of both the samples and compare them. • Include the load versus displacement curves of both the samples and describe about the determination of load PQ. • Describe the appearance of each fracture surface. • For each fracture surface identify what type of fracture took place. • Locate and describe the indications for this type of fracture (justify your answer to #2). • How are metal failures different from polymeric failures? 34 MSE 313 Spring 2011 Blank Page 35 MSE 313 Spring 2011 MSE 313 Integrated Junior Laboratory -‐ II Electrical Properties of Materials Part 1: Electrical Resistivity of Metal Material The purpose of this laboratory is to measure the electrical conductivity (resistivity) of selected conductors, insulators and semiconductors. This lab is designed to help the student understand how the electrical conductivity is related to temperature, alloying, permanent deformation and impurities. Part 2: Energy Gap in Semiconductors The purpose of this lab is to measure temperature dependence of the electrical conductivity in a semiconductor sample. The energy gap will be calculated from data taken in an intrinsic region, and the temperature dependence of the majority carrier mobility will be deduced from measurements taken in the extrinsic region. Part 3: Terminal Device Characteristics and Diode Characterization The objectives of this experiment are to learn methods for characterizing 2-‐terminal devices, such as diodes, observe some fundamental trends in the characteristics of various diode types, and to gain some familiarity with standard test bench instrumentation. 36 MSE 313 Spring 2011 Part 1: Electrical Resistivity of Metal Material Objectives: The purpose of this laboratory is to measure the electrical conductivity (resistivity) of selected conductors, insulators and semiconductors. This lab is designed to help the student understand how electrical conductivity is related to temperature, alloying, permanent deformation, and impurities. Equipment: Kelvin 4 wire multimeter setup Liquid nitrogen Small furnace/cartridge heater Thermocouple LabVIEW station Materials: Chromel wire (nickel with ~10% chromium) Alumel (nickel with ~5% aluminum, manganese and silicon) Stainless steel 304 wire (Iron alloyed with chromium and nickel) Introduction and Background: 1. Electrical Resistance and Resistivity: Engineering materials are classified into three main categories: conductors, insulators and semiconductors. This classification is based on the ease with which these materials conduct electric current when an electric field (voltage) is applied. Students should review their MSE 351 notes for each of these three general material types. The electrical resistance (R) of a material through which an electric current is passing is given by Ohm’s law: Equation 1i Equation 1ii where V is the applied voltage (Volts), I is the current through the material (Amperes). Equation (1) can be rewritten as: 37 MSE 313 Spring 2011 where L is the length of the material, such that V/L is the strength of the electric field, and A Is the cross-‐sectional area of the material, making I/A the current density. ρ is a material property termed electrical resistivity and is the inverse of the electrical conductivity σ of the material. The difference between resistance and resistivity is that resistance is dependent upon the geometry of the sample, whereas resistivity is a property of the material and is independent of the geometry of the sample. Therefore, it is important to calculate the electrical resistivity, so that it can be used as a design parameter. In order to convert the measured resistance to resistivity in this experiment, you must measure the diameter of the wire and the length of the wire between the contact points. 2. Electrical resistivity of conductors: In order to determine the resistivity, ρ, of a material, the electrical resistance, R, is measured. Samples of metals are provided in wire form. Because of the low value of the electrical resistivity of metallic materials, the connecting leads of the measuring instrument and the contacts between the probes and the sample can cause significant errors. To avoid these problems, a Kelvin (4 wire) resistance measurement is used. This method is described in detail in the website: http://www.allaboutcircuits.com/vol_1/chpt_8.html. The procedure is summarized and schematics are pasted where relevant. This resource is available in its entirety in the resource folder on the Jr. lab computer desktops. 2.1 Kelvin (4-‐wire) resistance measurement: Suppose we measure the resistance of some component whose resistance (Rsubject) is similar to that of the wire resistance (Rwire). Although the wire resistance is very small (only a few ohms per hundreds of feet, depending primarily on the gauge, or size, of the wire), the measurement error introduced by wire resistance will be substantial in this case. A method of accurately measuring the subject resistance in a situation like this involves the use of both an ammeter and a voltmeter. From 38 MSE 313 Spring 2011 Ohm's Law (R = V/I), the resistance of the subject component can be measured from the voltage dropped across it: Because this is a series loop, current is the same at all points in the circuit. Since we are only measuring the voltage dropped across the subject resistance (and not the wire’s resistances), the calculated resistance is indicative of the subject component's resistance (Rsubject) alone. Our goal is to measure this subject resistance, but we still need to use a fairly large length of wire to make contact to our experiment. See the situation below: At first it appears that we have lost any advantage of measuring resistance this way, because the voltmeter now has to measure voltage through a long pair of (resistive) wires, introducing stray resistance back into the measuring circuit. However, upon closer inspection, it is seen that nothing is lost at all, because the voltmeter's wires carry miniscule current. Thus, those long lengths of wire connecting the voltmeter across the subject resistance will drop insignificant amounts of voltage, resulting in a voltmeter indication that is very nearly the same as if it were connected directly across the subject resistance: 39 MSE 313 Spring 2011 Any voltage dropped across the main current-‐carrying wires will not be measured by the voltmeter, and so do not factor into the resistance calculation at all. Measurement accuracy may be improved even further by keeping the voltmeter's current at a minimum, either by using a high-‐ quality (low full-‐scale current) movement and/or a potentiometric (null-‐ balance) system. This method of measurement, which avoids errors caused by wire resistance, is called the Kelvin (4-‐wire) method. Special connecting clips, called Kelvin clips, are made to facilitate this kind of connection across a subject resistance: In regular, "alligator" style clips, both halves of the jaw are electrically common to each other, usually joined at the hinge point. In Kelvin clips, the jaw halves are insulated from each other at the hinge point, only contacting at the tips where they clasp the wire or terminal of the subject being measured. Thus, current through the "C" ("current") jaw halves does not go through the "P" ("potential," or voltage) jaw halves, and will not create any error-‐inducing voltage drop along their length: 40 MSE 313 Spring 2011 2.2 Electrical resistivity of conductors: Most conductors are metals (all metals are conductors, a few ceramics and polymers are conductors). For metals the number of free electrons in the material is large. In addition, a pure metal has a crystalline structure with few impurities, which results in high electron mobility. The electrical conductivity of metals is on the order of 5 x 107 [Ohm-‐m]-‐1. See attached table. 1i The electrical resistivity of metals is influenced by temperature, alloying, and plastic (permanent) deformation. Increasing the temperature decreases conductivity (increases resistivity) because there is more electron scattering from thermal vibrations. The resistivity of metals increases due to the presence of “impurities” (often due to alloying) and defects (such as vacancies and dislocations) because they serve as scattering centers for the conducting electrons; effectively decreasing the mobility of these electrons with increasing impurity or defect concentration. 2.3 Electrical Resistivity and Temperature in Metals: One may think of the thermal component of electrical resistivity as arising from the interaction between moving electrons and atomic vibrations. Since the amplitude of atomic vibration increases with temperature and since the probability that an electron collides with a given atom depends directly on the area swept out by the vibratory motion, it can be argued that the mean free path between collisions decreases as the temperature is raised. In metals, the charge carrier density is high, even at low temperatures. The change of conductivity with temperature is mainly affected by the change of mobility with temperature. The relationship between resistivity and temperature in metals is approximately linear except at very low temperatures, ρT = aT +ρ0, where a and ρo are constants that depend on the type of metal and the imperfections in the metal (impurity atoms, dislocations, etc.) When the electrical resistivity of a metal or alloy is known at two different temperatures, the electrical resistivity at a third temperature may be obtained by linear extrapolation. The total resistivity of a conductor is given by the sum of the “thermal” component (ρth) and the “residual” component (ρr) in an equation known as Matthiessen’s Rule, ρ = ρth + ρr Equation 1iii 41 MSE 313 Spring 2011 Figure 1i: Cartoon depiction of Matthiessen’s Rule and graphical relationship between temperature and resistivity of a metal. Table 1i: R vs T of various metals. 42 MSE 313 Spring 2011 Experimental Procedure: Experiment 1.1: The first experiment is to measure the resistance of conducting wires using the Kelvin 4-‐wire probe procedure. (Fig. 1ii) Figure 1ii: Arrangement of wires • Precisely measure the length of the conducting wires (pure nickel, Chromel, Alumel, copper, and brass wires). • Measure the diameter of both wires. • Remember that you are only concerned with the length of the wire between the points where you will be making contact. • Make a loop with diameter around 2”, so that the loop of wire can be easily dipped into a liquid N2 bath. • Using the handheld meter, measure the resistance of the wires directly when the wires are subjected to various temperatures, such as room temperature (RT), furnace, liquid N2, etc. • Log the measured values for each wire, and then compute the resistivity of the wires for each temperature. • Plot the resistivity versus temperature, and discuss the behavior; (to be included in the lab report) Experiment 1.2: This experiment will be performed using LabVIEW to control the multimeter performing the Kelvin probe measurement of resistance of the wires. The output of the multimeter is fed into the computer through GPIB interface. This time, temperature is 43 MSE 313 Spring 2011 monitored by a thermocouple, and the output of which is fed into the computer through a NI-‐DAQ device. • As in Experiment 1.2, , measure the resistance of each of the wires using LabVIEW for temperatures ranging from RT to a heated furnace and RT to liquid N2. • Compute the resistivity of the wires for each temperature and plot the resistivity versus temperature. • Discuss the behavior (to be included in report). Figure 1iii: Lab Set-up. Experiment 1.3: Mark out 1 ft. of each of the wires to measure their resistance as a function of temperature as described above after mechanical deformation. • To induce the mechanical deformation, wrap the ends of the wire around two rods so that the wire will not slip when pulled. The length of the wire between the rods should be 1 ft. • Pull the wire apart slowly, and the wire should extend by 20-‐30 %. You should feel an increase in the force required to elongate the wire. • Carefully measure the new length and diameter of the wire. • If the Instron is available, put the wire in the tensile apparatus taking care to ensure that the gage length is at least the area of interest. Test rate should not exceed 1.2 mm/min. Continue test until material is in the plastic region, then stop, remove the wire. • Measure the resistance of all wires after deformation at all temperatures described above. • Calculate the resistivity and conductivity. • Plot the resistivity data as a function of temperature and determine ρr from the deformed specimens. 44 MSE 313 Spring 2011 Part 2: Energy Gap in Semiconductors Objective: This lab is to measure the temperature dependence of electrical conductivity in a semiconductor sample. Energy gap will be calculated from the data taken in an intrinsic region, and the temperature dependence of the majority carrier mobility can be deduced from measurements taken in the extrinsic region. Theory: Semiconductors in the pure state are called intrinsic semiconductors. If impurities are added to the material the electrical characteristics change and the semiconductors are called extrinsic semiconductors. In either type of semiconductor there are two types of carriers: electrons, and holes. When an electron becomes free, it leaves behind a positively charged hole. Both the hole and the electron carry charge. Therefore, the conductivity is equal to the sum of the contributions of each. Equation 2i where n is the number of electrons, p is the number of holes, q is the charge of the carrier (hole or electron), and m is the mobility of the carrier. In an intrinsic semiconductor, the number of electrons is equal to the number of holes, which simplifies the expression for conductivity. Equation 2ii In extrinsic semiconductors, the semiconductor is doped with a Group IIIA element (B, Al) or a Group VA element (P, As). The Group IIIA elements need an electron to complete their outer shell and thus “steal” it from a silicon atom, leaving behind a hole, creating p type carriers. These are called p-‐type semiconductors. In a p-‐type semiconductor the number of holes due to doping is far greater than the number of electrons and only the second term of equation (5) is important. Equation 2iii The number of carriers, p, is simply equal to the number of impurity atoms. The group VA elements have an extra electron, which is donated to the silicon adding n type carriers. These are called n-‐type semiconductors. In this case, when an electron becomes free, a hole is not left behind and the number of electron carriers is far greater than the number of holes. 45 MSE 313 Spring 2011 Equation 2iv Again, the number of carriers is equal to the number of electrons donated by the impurity atoms. A doped semiconductor exhibits extrinsic behavior when the dopant concentration Nd is much larger than the concentration of the electron-‐hole pairs ni generated by thermal excitations. In this case, provided the temperature is not too low, the "free charge" concentration n = ni+Nd ≈ Nd is temperature independent, and the charge transfer is essentially due to the majority carriers (holes in p-‐doped, or electrons in n-‐doped samples). At even lower temperature the semiconductor enters the so called "freeze-‐out region" and the impurity carrier concentration decreases exponentially as exp(-εd/2kT), where εd is the impurity ionization energy (εd≈10 meV in Ge and εd≈40 meV in Si) and k is the Boltzmann constant. In the extrinsic region the current density can be simply written J = e n vD = q n µ E Equation 2v σ = q(nµn+pµp) = (1+b) niµn Equation 2vi where vD is the drift velocity, m the mobility, and e is the elementary charge. The electrical conductivity is proportional to the charge carriers concentration and to the mobility: σ = q n µ. Therefore in the extrinsic region, since n ≈ constant, the temperature dependence of the conductivity and mobility are identical. Theoretical calculations, accounting for lattice scattering of the charge carriers and neglecting contributions due to scattering with impurities, give a mobility µ ∝ T-α, with α = 3/2. The experimentally observed α value, however, is usually larger than the predicted value 3/2, ranging from 1.6 to 2.5. The thermal generation of the electron-‐hole pairs grows exponentially with temperature, and when the temperature is high enough the sample enters the intrinsic region where Nd becomes negligible with respect to the concentration of thermally generated electrons (ni) and holes (pi=ni). In the intrinsic region we must use the ambipolar conduction formula where the mobility ratio b = µn/µp is nearly temperature independent. We have ni = pi ∝ T3/2 exp[-Eg(T)/2kT] Equation 2vii where Eg(T) = Eg(0)-γT is the temperature dependent energy gap that separates the conduction band from the valence band. Here the temperature dependence of the 46 MSE 313 Spring 2011 conductivity is largely dominated by the exponential dependence of the carrier concentration, so that a semi-‐logarithmic plot of σ versus 1/T yields a straight line with slope Eg(0)/2KB. Experimental Setup: The experiment can be performed using a constant current generator, a voltmeter with high input resistance, a thermometer, and a device for changing the sample temperature at a small rate. Figure 2i: Typical set-‐up for this experiment The experimental apparatus will consist of a liquid nitrogen bath with a large thermally conductive mass in it, upon which will sit the copper block containing both a cartridge heater and the samples. The semiconductor sample will be affixed to the copper heating block, and temperature measurements will be taken from the built-‐in thermocouple (inside of the cartridge heater). In this experiment, we will use a “unijunction transistor” as a Si sample (Texas Instruments 2N2160 (metal case)). The unijunction transistor is made of a bar of n-‐type Si material with a p-‐type junction near the center, as seen in Figure 2ii below. 47 MSE 313 Spring 2011 Figure 2ii: Unijunction transistor Since this device has the base pins 1 and 2 connected with ohmic contacts to the semiconductor substrate, we will only use the connection between base 1 and base 2 so that the unijunction transistor is nothing more than a n-‐type Si specimen. The emitter pin is disregarded in this case. A typical run should be performed within less than 2 hours, with the temperature changing at a rate ∂T/∂t ≈ 5×10-‐2 Ks-‐1. Using a liquid nitrogen bath the temperature can be varied in the range 80 K < T < 430 K. The upper limit is imposed by the melting of the junction contacts on the sample to T ≈ 520 K. The smaller the temperature slope ∂T/∂t is, the smaller the thermal gradient ∂T/∂x will be within the sample. Experimental results obtained in two typical runs are shown in Figure 3, for a germanium sample (n-‐doped, ρ ≈ 14 Ω cm) and for a unijunction transistor, respectively. Here T is the temperature in Kelvin and t is the temperature in Celsius (t = T – 273.15). Figure 2iii: The voltage drop measured across the semiconductor samples in the whole temperature range. The Germanium sample is a 2x2x10 mm bar, n-‐doped. The Silicon sample is the base, n-‐doped, of a 2N2160 unijunction transistor. 48 MSE 313 Spring 2011 Figure 2iv (a) shows the Ge resistance in the intrinsic region plotted versus the reciprocal absolute temperature 1/T in a semi-‐log plot. The slope of the linear fit for 58°C < t < 143°C gives Eg(0)=0.79±0.02 eV. The same plot for the Si sample is shown in figure 2iv (b). The best fit in the temperature range 185°C <t<255°C gives Eg(0)=1.18± 0.02eV. In figure 2iv (c) the log10R for the germanium sample is plotted versus log10T and the slope of the fitting line for -‐160°C <t<-‐10°C gives α=1.65±0.02. The extrinsic region for the unijunction transistor (figure 2iv d) spans the temperature range -‐100°C < t < +100°C and the exponent in the power law µ ∝ T-‐α is α=2.30± 0.03 . The slight deviation from linearity at the lowest temperatures indicates the beginning of the "freeze-‐out region". Figure 2iv: (a) and (b): the linear fit in the intrinsic region (high temperature); (c) and (d): linear fit in the extrinsic region (low temperature) Experimental Procedure: A unijunction transistor consists of three wires, two of which are directly connected to the n-‐type Si bar through ohmic contact and one of which is connected to the p-‐type region of the bar, as in figure 2v below. Since there is no indication on the transistor as to which lead is which, the student will need to test the transistor to identify all the pins. 49 MSE 313 Spring 2011 Figure 2v: Interpretation of the internal arrangement of a unijunction transistor. • Using the knowledge gained from MSE 351, first identify which two leads are connected to the n-‐type region of the bar, and finally which one is connected to the p-‐type region. • Once the two leads connected to the n-‐type Si bar have been identified, connect these two leads to a constant current source. • Set the constant current source to generate 0.2 mA and measure the voltage across the unijunction transistor as a function of temperature using LabVIEW. • Generate a logR vs. 1000/T plot for intrinsic temperature region and a logR vs. logT plot for the extrinsic temperature region. • If necessary, the Fluke Digital Voltmeter can be used, the specifications for this instrument in Resistance mode is described in the Appendix. 50 MSE 313 Spring 2011 Part 3: Terminal Device Characteristics and Diode Characterization NOTE: This lab has been modified from an EE331 written by R.B. Darling lab with permission. Objective The objectives of this experiment are to learn methods for characterizing 2-‐terminal devices, such as diodes, observe some fundamental trends in the characteristics of various diode types, and to gain some familiarity with standard test bench instrumentation. Precautions: None of the devices used in this set of procedures are particularly static sensitive; nevertheless, you should pay close attention to the circuit connections and to the polarity of the power supplies, diodes, and oscilloscope inputs. Experiment #1: I-‐V characteristics of diode with forward bias Set-‐Up We will use two commercially available p-‐n junction diode, 1N34 and 1N4004. 1N34 is a germanium based p-‐n junction diode, whereas 1N4004 is silicon based. We start with the forward bias condition to measure the I-‐V characteristics of the diode. Pre-‐experiment: Verify which side of the diode is p or n using an ohm meter. Based on your knowledge learned in MSE 351, think about how to do this task. For this lab you will be using a Breadboard, which is typically a piece of white plastic with many small holes as shown below. Some of the holes are already electrically connected with each other, allowing you to insert leads from devices (such as resistors or diodes) as well as wires to create basic circuits without the need to solder or wire wrap. The holes are 0.1 inch apart, which is the standard spacing for leads on integrated circuit dual in-‐line packages. You will test the connections in this lab. 51 MSE 313 Spring 2011 Note that each set of 5 horizontally oriented holes constitutes a tie point. The vertical columns of holes are all internally connected into a single tie point; these are normally used for power supply distribution. To attach test leads to the breadboard, you can use either the exposed end of a component lead, or you can insert a small pin into the appropriate tie point and connect the squeeze hook or oscilloscope probe to the pin. Using the breadboard, set up the following circuit. DMM1 (+) R 1 VSS DMM1 (-) DC DMM2 (+) SUPPLY D 1TEST DIODE DMM2 ( ) Here, DMM refers to terminals that are to be connected to a Digital Multi Meter (DMM). You will need two DMMs to measure the voltage drop across (1) the resistor R1 and (2) the diode D1, as shown above. Create such a circuit for each of the following six resistors: R1 = 100 Ω, 1.0 kΩ, 10 kΩ, 100 kΩ, 1.0 MΩ, or 10 MΩ, 1% 1/4W To speed up this process, you may wish to insert all six resistors and the two diodes into the breadboard at once so that one end of each resistor connects to the anode of each diode. The long, horizontal tie point strips on the solderless breadboard are quite convenient for this. The proper resistor and diode can then be quickly selected by simply moving the power supply leads. Use the bench DMM to measure the DC voltage across either the resistor or diode. Measurement: For each of the diodes (1N34A and 1N4004), use the following procedure. • First, adjust the DC power supply VSS to produce +10.0 Volts across R1 and monitor the voltage on DMM1. • Measure the forward turn-‐on voltage of the diode with DMM2. If two DMMs are not available at your lab bench, you may have to switch back and forth between the two terminals at DMM1 and DMM2. • Record the diode's current and voltage in a table in your notebook. The diode current can be calculated using Ohm’s Law (I = V / R), which is equal to 10.0 V / R1. 52 MSE 313 • • Spring 2011 Change the resistor to the next value and repeat. Measure the six different (I, V) pairs for each diode. Experiment #2: I-‐V characteristics of diode with reverse bias: Set-Up : Configure a DC power supply to produce an output voltage of VSS = +10.0 Volts. If the DC power supply has a current limiting ability, configure the power supply to limit the current to 100 mA. Route the output of the DC power supply to your breadboard using two squeeze hook test leads. Note: Diodes are direction dependent. If you are unsure about any set up, have your TA look it over BEROFE turning on power. In this section, you will measure the leakage current of the same diodes used in the experiment #1. Each diode should be connected as shown in the figure below. Use the following parts: R = 1.0 MΩ 1% 1/4 W DMM (+) D1 = same as #1 R = 1M VSS DMM (-) DC SUPPLY D1 TEST DIODE Connect only one diode at a time in the circuit (above), noting that the banded end is the cathode, which corresponds to the bar on the circuit symbol. Connect the DC power supply across both R and D1 and then connect the DMM across only R using two pairs of squeeze hook test leads as shown above. The DMM should read less than +10.0 V. Measurement: Measure the reverse leakage current for each of the same diodes in Experiment #1. Do this by using the DMM to measure the voltage across R, after which divide this voltage by the resistor value (e.g., R = 1.0 MΩ) to obtain the current through R, and therefore the current through D1. Record your measurements and calculations in a table in your notebook. 53 MSE 313 Spring 2011 Experiment #3: Measurement of diode I-‐V characteristics using the oscilloscope Set-Up: In this procedure, you will use an oscilloscope and the laboratory variable transformer to display the current-‐voltage (I-‐V) characteristics of a diode. This procedure relies entirely upon the ability to float the transformer output at a potential that is different from the ground of the oscilloscope. (All oscilloscopes have each channel grounded to the 120 VAC safety or chassis ground, so an oscilloscope can only be made to float by the use of an additional isolation transformer.) This procedure can also be performed using a signal generator that produces a floating output; however, the following procedures assume that you are using the laboratory transformer. BEFORE turning on the power, have your TA verify your set-‐up. Set up and connect the circuit shown below using the following components: R1 = 1.0 kΩ 1% 1/4 W D1 = 1N34A and 1N4004 SCOPE CHANNEL-1 BLAC (X-INPUT) K D1 V SCOPE GROUND 1 LAB XFMR R1 1.0 k Ω SCOPE CHANNEL-2 WHITE (Y-INPUT) BREADBOARD Plug the laboratory transformer into a 120 VAC receptacle, and turn its power switch OFF. Connect one lead from the black banana jack output of the lab transformer to the diode on the breadboard, and then connect another lead from the red banana jack output of the lab transformer to the resistor R1 on the breadboard. This will establish a 60 Hz sinusoidal input to the circuit. You may set your variable transformer to around a 10V peak-‐to-‐peak signal. More Set-‐Up: Next, configure an oscilloscope to display the I-‐V characteristics as follows: Attach an oscilloscope probe to Ch-‐1, connect the probe to the diode (the same connection point as the black output of the lab transformer), and connect its ground lead to the junction 54 MSE 313 Spring 2011 between the diode and the resistor. Attach a second oscilloscope probe to Ch-‐2, connect the probe to the resistor (the same connection point as the red output of the lab transformer), and connect its ground lead to the junction between the diode and the resistor. Configure the oscilloscope to produce an X-‐Y display, using Ch-‐1 as the X-‐axis and Ch-‐2 as the Y-‐axis. Set Ch-‐2 to invert the incoming signal. Turn ON the power switch on the lab transformer to energize the circuit. At this point you should have something on the screen which resembles the I-‐V characteristics of a diode. Adjust the position controls to center and calibrate the curve to the center point of the screen as follows: Switch both Ch-‐1 and Ch-‐2 input couplings to GND. Adjust the vertical position control for Ch-‐2 and the horizontal position control to move the dot to the exact center of the oscilloscope screen. After having done so, return both the Ch-‐1 and Ch-‐2 input couplings to DC. You may need to decrease the intensity of the trace to remove any halo from around the dot. Also adjust the scaling on both the x and y axis such that you can take readings off the curve. The oscilloscope should now be displaying a graph of the current-‐voltage (I-‐V) characteristics of the device. The vertical axis or y-‐input is proportional to the current through the diode, since it measures the voltage across R1. The voltage across R1 is proportional to the current flowing through it, and this same current flows through the diode. The horizontal axis or x-‐input is proportional to the voltage across the diode. Thus, this circuit produces a simple, but effective and accurate curve tracer. Note that the Ch-‐2 input to the oscilloscope must be inverted in order to account for the polarity of the voltage drop produced across R1. This then keeps the I-‐V characteristics of a passive device within quadrants 1 and 3 of the I and V axes, as they are normally drawn. Almost all commercial curve tracers, such as the Tek-‐576, perform their voltage sweep at a 60 Hz rate. This is usually derived directly from the AC line frequency. This feature has the advantage of making the sweep synchronous with the AC power line and therefore somewhat more robust to AC power line interference. At a different sweep frequency, the I-‐V characteristics would otherwise flutter around as a result of beating with fluorescent light and other stray pick-‐up coupling which might be oscillating at 60 Hz. Measurement: • Sketch the I-‐V characteristics of each diode in your notebook (they should look like the oscilloscope trace) on the same set of axes. • Using the scaling factors from the oscilloscope, scale the x and y axes of your sketch with tick marks for current and voltage. • Graph paper is handy for this and makes the following analysis easier. • You may wish to keep the lab transformer and the oscilloscope in their present set-‐ up configuration, since they will be used again to measure additional I-‐V characteristics in Procedure 4. 55 MSE 313 Spring 2011 Experiment #4: Measurement of diode I-‐V characteristics using LabVIEW Computer-‐controlled automatic measurements are commonly used to gather data for the purpose of characterizing or testing a device or system. In this experiment, a LabVIEW curve tracer will be used to capture the characteristic I-‐V curve for a pn-‐ junction diode. This procedure will also use the data acquisition (DAQ) card in the computer to both create the excitation voltages and to measure the resulting test voltage responses. No other external bench instruments are needed other than the computer, the DAQ card, its cable, and the BNC-‐2120 connector block. Software Set-‐Up: First, log on to the computer and launch LabVIEW. From File > Open … , open the VI named “DiodeCurveTracer.vi.” For this VI to open correctly, two sub-‐VIs named “VoutArray.vi” and “IODriver3.vi” must also exist in the same directory as “DiodeCurveTracer.vi”. Theory of Operation: The front panel window has been designed to show roughly how this diode curve tracer operates. First, the six controls inside the Scan Range box are used to set up the sequence of voltages which will be applied to the resistor and diode series combination. The forward and reverse parts of the scan are independently set up according to their starting value, their ending value, and the number of points used for each. When the START SCAN button is clicked, this sequence of voltages is passed to the power supply which first steps upward in the forward direction, then back down, then steps downward in the reverse direction, and then back up, making one complete cycle through the applied bias range for which the diode is to be tested. The cathode end of the diode (end with the bar) is grounded, and the voltage at the node between the diode and the resistor is measured, along with the voltage that is applied to the other end of the resistor by the power supply. The voltage across the diode is used to create the x-‐ values for the I-‐V curves, and the y-‐values of diode current are obtained by subtracting the voltages at the two ends of the resistor and then dividing by the value of the resistor. This is typically how one accomplishes current sampling with a data acquisition system. The value of the current sampling resistor is input using the control located to the right of the resistor symbol. The diode voltage and current are then plotted as (x,y) pairs in the chart. After the scan is complete, the SAVE DATA button can be clicked to write the data to a spreadsheet file. Hardware Set-‐Up: The power supply output and the two measured voltages are implemented through channels on the data acquisition (DAQ) card. Analog Output channel # 0 (AO-‐0) is used to create the power supply output voltage. The voltage from the power supply is 56 MSE 313 Spring 2011 measured by Analog Input channel # 0 (AI-‐0), and the voltage across the diode is measured by Analog Input channel # 1 (AI-‐1). The hardware is set up by connecting the diode being tested and the current sampling resistor to the proper terminals of the BNC-‐2120 connector block. Connect a 5.1 kΩ resistor between the center pins of the BNC connectors for AI-‐0 and AI-‐1. Then connect a jumper wire between the center pins of the BNC connectors for AO-‐0 and AI-‐0. Finally, connect a diode between the center pin of the BNC connector for AI-‐1 and its ground shield, with the bar end of the diode (its cathode end) connected to the ground shield. Also make sure that the slide switches for AI-‐0 and AI-‐1 are both set to BNC inputs and that the slide switches for AI-‐0 and AI-‐1 are each set for grounded source measurements (the GS position). This will connect each of the BNC outer shields to the internal analog ground with a built-‐in 4.99 kΩ resistor. However, to make the diode curve tracer work properly, each of the analog input BNC outer shields (their (−) inputs) must be shorted to ground. The outer shield of the BNC connector and the analog outputs are true analog grounds. Thus, connect the BNC outer shields of AI-‐0 and AI-‐1 to the BNC outer shield of AO-‐0 to establish a proper ground system on the BNC-‐2120. The BNC-‐2120 connector block has far more BNC connectors than the number of BNC connector cables that a student group would normally have. To get around this, much of the wiring can be accomplished by simply inserting component or jumper wire leads into the center pins of the BNC connectors. If you choose to do this, be very careful not to damage the center pins of the BNC connectors. Most component leads by themselves are too narrow to fit securely in the BNC center pin hole. However, if you insert a pair of component leads, or a pair of #22 AWG jumper leads, this will usually provide a sufficiently tight connection that will not damage the BNC center pins. Interconnecting the BNC outer shields can be done using squeeze hook jumper leads. From the description of Hardware Set-‐Up, schematically draw the electrical wiring diagram. By doing so, you will have a better understanding of what you are going to do. First try by yourself, then ask TA for help. Measurement: • From the front panel window, click on the ‘run’ button to start the diode curve tracer VI. • Keep the default settings for the forward and reverse bias scan ranges: forward bias: 10 steps from 0.0 Volts to +5.0 Volts, and reverse bias: 10 steps from 0.0 Volts to −5.0 Volts. • After rechecking all of the connections, click on the START SCAN button, which should start the measurement sequence and then display the resulting diode I-‐V characteristics on the x-‐y chart. 57 MSE 313 Spring 2011 • • • • • Once you are happy with the measurement, click on the SAVE DATA button to save the measured diode I-‐V characteristic data in an Excel spreadsheet format. A Save As … dialog window will open, and you can type in the name of the file that you want the data written to, for example, “Experiment1Procedure4.xls.” Click on OK to write the file. Once you have saved the data, click on the STOP button to halt the measurement VI. You should open this newly created file with Excel to verify that the data was properly written to the file. If everything was working properly, the diode voltage values (in units of Volts) should appear in the first column, and the diode current values (in units of milliamperes) should appear in the second column. It is generally a good idea to halt any running VI when you are done with it. If you wish to use other Windows programs, such as Excel, or Internet Explorer, or Windows Explorer, you will find that these programs will run rather slowly while any VIs are running at the same time. Experiment #5: Measurement of a zener diode Set-‐Up: Replace the diode used in the Experiment #4 with a 1N4732 zener diode, keeping the banded end (the cathode) connected to the ground shield of AI-‐1. Change the Scan Range Box settings to scan upwards from 0.0 V to +10.0 V in 20 steps, and then downwards from 0.0 V to −10.0 V in 20 steps. Just clicking on the up/down buttons is the easy way to accomplish this. You will also need to rescale the displayed I-‐V graph by clicking on the graph and then right-‐clicking on Properties. Go to the Scales tab and first select the X-‐Axis from the drop-‐down list. Change the minimum and maximum to −10 V and +10 V. Similarly, select the Y-‐Axis from the drop-‐down list and change the minimum and maximum to −0.5 and +0.5 (mA). Measurement: • Press the START SCAN button to begin the measurement, after which, the resulting I-‐V characteristics of the zener diode should appear in the displayed graph. • Once you are happy with the measurement, click on the SAVE DATA button to save the measured diode I-‐V characteristic data in an Excel spreadsheet format. • A Save As … dialog window will open, and you can type in the name of the file that you want the data written to, for example, “Experiment1Procedure5.xls.” Click on OK to write the file. • Once you have saved the data, click on the STOP button to halt the measurement VI. 58 MSE 313 • • Spring 2011 As a double check of the data, reverse the polarity of the zener diode, connecting its non-‐banded end (its anode) to the shield of AI-‐1. Press the START SCAN button again, and you should see the same characteristics as before, but now inverted about the origin of the graph (i.e. switching quadrants 1 and 3). Experiment #6: Characterization of a light-‐emitting diode (LED) Circular LED's, as well as other small panel lamps, come in several standard sizes. A T-‐1 size is 3 mm in diameter, and a T-‐1 3/4 size is 5 mm dia. There are several ways of identifying which terminal is which on an LED. If the leads have not been cut, the anode or (+) lead will be the longer of the two. (This also holds true for parallel lead electrolytic capacitors.) If the leads have been cut, you will have to use the next method. Look straight down on the hemispherical dome of the LED (so that the LED would be shining toward you) and you should notice that the small lip at the bottom of the plastic has a flat side on it. The lead that is closest to this flat side is the cathode or (−) lead. Set-‐Up: Locate a T-‐1 red LED and replace it for the diode in the LabVIEW curve tracer of Procedure 5 or 6. Start the DiodeCurveTracer.vi by pressing the Run button on the toolbar, and set the Scan Range Box settings to scan upward from 0.0 V to 10.0 V in 20 steps, and then downward from 0.0 V to −10.0 V in 20 steps. Make certain that at least a 1 kΩ resistor is used in the circuit, to limit the current in either direction to no more than 10 mA. Measurement: • Press the START SCAN button to initiate the measurement process. • You may notice that the LED will briefly glow as the curve tracer increases the sweep voltage. The resulting I-‐V characteristics for the LED should appear on the displayed graph. • Once you are content with the measurement, click on the SAVE DATA button to save the measured diode I-‐V characteristic data in an Excel spreadsheet format. • A Save As … dialog window will open, and you can type in the name of the file that you want the data written to, for example, “Experiment1Procedure6.xls.” Click on OK to write the file. • Once you have saved the data, click on the STOP button to halt the measurement VI. 59 MSE 313 Spring 2011 Lab 2 Questions and Discussion: • Does the relation ρT = aT +ρ0 still hold for these materials at all temperatures examined? • Given what you know of transistors, why was a unijunction transistor used instead of any other type? • Create a semi-‐log plot of I versus V, where I is on a log scale and V is on a linear scale. • For each decade of increase in the diode current, by how much does the diode turn-‐on voltage increase? • Identify current ranges on your graphs that correspond ideally to diode factors of 1 and 2. Identify any other obvious trends. • Which diode of the two you tested would be the most suitable for charging up a capacitor using a peak rectifier circuit and allowing the capacitor to keep its charge for the longest period of time (keeping in mind that you would prefer to minimize the voltage dropped across the diode and that you would want the minimal amount of energy to leak back out once the capacitor was charged)? • If the polarity of the diode was reversed (connecting its cathode to the current sampling resistor and AI-‐1 and connecting its anode to the analog ground), what would be the expected I-‐V curve? • If the diode was replaced by another 5.1 kΩ resistor, what would be the expected I-‐V curve? To what would the slope of the resulting I-‐V curve correspond? • From your sketch, extract the forward-‐bias turn-‐on voltage (Von) for each diode. Compare your answers to the results of the previous DMM readings. • Using the data that was collected in the spreadsheet file, compute a value for the zener resistance rz of the diode in its breakdown region. Similarly, compute a value for the forward (on) resistance rf of the diode. The easiest way to do this for both regions is to identify two strategic (I,V) points which define the best fit lines in these regions and then compute the inverse slopes of these lines. • The power rating of the 1N4732 zener diode is quoted at 1.0 Watt. Calculate the maximum current that the diode can handle in the forward (on) direction and then in the reverse (zener) direction and not exceed the 1.0 Watt limit. 60 MSE 313 Spring 2011 • Insert the 1N4732 zener diode into the curve tracer made from the lab transformer and the oscilloscope. Compare the resulting I-‐V characteristics with those obtained from the LabVIEW curve tracer. • Discuss why the turn-‐on voltage of the LED is significantly higher than that of a typical silicon switching or rectifier diode. • References: Kasap, S.O., “Principles of Electronic Materials and Devices” 3rd edition. McGraw Hill, 2006. Kuphaldt, Tony, “All About Circuits Vol. 1 DC”. On-‐line resource: <http://www.allaboutcircuits.com/vol_1/chpt_8.html. >. Date accessed: March 18, 2011. Darling, R.B., “EE-‐331 Laboratory Handbook; 2-‐Terminal Device Characteristics and Diode Characterization”. Date not provided. 61 MSE 313 Spring 2011 Blank Page 62 MSE 313 Spring 2011 MSE 313 Integrated Junior Laboratory-‐III Screen Printing of Thick Film Materials: Acknowledgement: This lab was written in part by Monika Marciniak as part of her Senior Project in 2008. Part 1: Print/ Dry/Fire Resistor Circuits The purpose of this laboratory is to screen print, dry and fire thick film circuits made of conductive ink. This lab is designed to introduce students to the technology of printing thick film and hybrid circuit using a screen-‐printing machine. The fundamentals of the equipment, inks, and thick film materials processing will be explored. students will practice screen and stage alignment to obtain patterns at precise locations on the substrates. Part 2: Firing Profiles/Resistance Measurements / Pattern Design Principles: The purpose of this laboratory is to fire thick film resistors. This lab is designed to obtain and study different firing cycles of the resistors and to determine the effect of firing temperatures on the resistors’ performance. Students will also study aspects of thick film design and layout. The students will examine the patterns of printed/fired thick film circuits obtained from Part 1. Factors such as geometry, sheet resistance, print thickness and electrical performance will be studied and students will compare calculated theoretical results with the experimental data Part 3: Characterization: The purpose of this lab is to characterize the final printed resistor circuits using Fluke multi-‐meter data acquisition and gain thickness measurements with a profilometer. 63 MSE 313 Spring 2011 Screen Printing Fundamentals: Background: Screen printing is a process whereby functional material is deposited in a controlled manner onto a substrate. It can be a simple, hydraulic style device or a complicated computer control system. But the same basic principles apply. Thick film screen-‐ printing has been used in the electronics manufacturing industry since the 1940’s when it was first introduced during World War II as an alternative method to conductive wiring in circuits. It is still used today for preparing conductive pathways, resisters, and other passive components in the semiconductor industry. And, as we shall see, for manufacturing sensing components, i.e., tin-‐dioxide sensing materials. Screen Printing Basics: There are a number of factors to consider when utilizing screen printing for circuit design and manufacturing. Choosing the type of paste for the functional components and for the conductive and resistive components is one important design consideration. One must also determine the parameters of the screen to be used. What kind of screen material, what kind of emulsion material, what mesh size, all must be considered and decisions made concerning before moving on to printing the devices. We have already done the decision making for the pastes, next we need to determine the screen design and type. There are two primary materials used in screen making. Stainless steel and nylon or polyester. Stainless steel is used in our labs for the obvious reason that it is much more durable. Nylon is used primarily when irregular surfaces are to be printed. However, Nylon tends to absorb water and because of its properties some kinds of paste will stick to the screen during snap-‐off reducing the quality of the finished component. Stainless steel is durable and doesn’t absorb water. However, it can easily be damaged by being stretched out, bent, or broken, so regardless of the screen material care must always be used. The second consideration when designing/choosing a screen is the emulsion. The emulsion is a material that is photosensitive which is deposited on the back of the screen mesh. A pattern is ‘printed’ on the emulsion and then the screen is developed. UV light is generally used. After the development step is completed, the screen has the pattern exposed. The thickness of the emulsion and the screen will help to determine the minimum thickness of the components printed. And finally, the mesh size should be considered. The mesh count/opening as well as the weave will effect the thickness and line resolution of the final print. The thickness and rheology of the inks being used will drive the decisions about the screen mesh and visa versa. There are a number of materials used as substrates. Most common are Al2O3, Si, and Kapton, a polymer. The substrate is chosen to best fit the system overall but two 64 MSE 313 Spring 2011 important considerations will be firing temperatures required for the pastes and adhesion properties. The substrates we are using are Al2O3. These substrates are robust and fit into the screen printer well. Because of the temperatures required to fire the various pastes we are using, the alumina is the best choice. Theory: Screen-‐printing technology is based on the formation of patterns through the use of a woven cloth ‘screens’ and viscous pastes. Some of the openings of the screen are blocked with filler and, when the paste is forced through those remaining onto the substrate, a replica of the pattern on the screen is obtained. Virtually any material that can be formulated into a viscous paste may be used, including most liquids and solids. There are many variables that may affect the quality of prints produced by the thick film process. These variables are categorized into the following main groups, and subgroups: Ink properties (viscosity, surface tension, ink composition) Screen variables (stencil, mesh, frames, emulsion) Machine variables (squeegee, snap-‐off, flood blade) Deposition, drying and firing procedures. Description of some of these screen-‐printing factors is provided below. Deposition, drying and firing are explored in experimental procedures. Ink/Paste Rheology: The flow behavior of thick film inks is controlled by the viscosity and surface tension of the ink and by the dependence of these properties on shear rate and time. Both of these properties are related to interatomic forces within the body of the fluid, viscosity being regarded as the resistance to motion of one layer of fluid over another, whereas the surface tension arises from the imbalance of forces at an interface between two different materials. Thick films are classified as non-‐Newtonian pseudo-‐plastic fluids, which means that they show decreasing resistance to flow with increasing shear stress. In other words, as the squeegee speed is increased, the ink becomes more fluid. That characteristic is very desirable, because as the squeegee shears the ink, the ink passes easily through the openings of the screen, wets the substrate, and releases cleanly from the screen a the screen peels away from the substrate. As soon as the shearing force is removed, the ink quickly recovers to nearly the original viscosity. The ink remains fluid long enough to flow over the mesh marks but not long enough to flow beyond the area where it was deposited. Paste Preparation: The constituents of a paste require careful selection and processing. Figure 1 shows an idealized paste production sequence for a thick film resistor. The general principle is common to all pastes. 65 MSE 313 Spring 2011 (a) (b) Figure 1: Fabrication of an idealized thick film resistor paste: (a) raw material preparation, (b) formation of paste. The Screen: Screen is the most important part of the screen-‐printing equipment. It is composed of three sections -‐ a stencil that defines the pattern to be printed and its thickness, a mesh, which supports the stencil, and a frame, which supports the mesh. Frames Screen frames for thick films are mostly made of metal, usually of aluminum alloy (see Figure 2). The load supported by each side of even a small screen frame when mesh is attached to it is in the order of 50 kg; therefore the strength and stability of metal are necessary. Figure 2: MSE metal screen frames with stencils Mesh: NOTE: See Appendix A for the dimensional characteristics of typical stainless steel meshes. There is three types of mesh material that are commonly available and they are: nylon, polyester, and stainless steel. Characteristics of the three materials are explained in Table 1. Table 1: Characteristics of mesh materials. 66 MSE 313 Material Nylon Polyester Stainless steel Spring 2011 Advantages Monofilament is strong and resilient and can be used thoroughly. It has ability to stretch, which makes it possible to print on irregular surfaces. Very stable, resilient and flexible enough to conform to the normal irregularities found on the surface of thick film circuits. Stronger and more stable than nylon and polyester. It has higher modulus of elasticity. It is less susceptible to wear, so it can last longer. Disadvantages It is not stable because it can absorb water and is affected by changes in humidity. It is also affected by changes in temperature. Low elastic limit. It has lower elastic limit, so it can be easily damaged by accidental denting or coining. There are two main rules that help choose a mesh: 1. The minimum line width which can be printed with a given mesh is 3 times the mesh thread diameter. This means that narrow lines cannot be printed with large thread diameter mesh. 2. The mesh opening should be at least 3 times the particle size of the paste being printed. In normal thick film applications, the paste particles are unlikely to be more than 5 to 20 mm in size, so the finest meshes can be used. However, solder paste has particles typically in the range of 25-‐70 mm and this clearly restricts the choice of mesh. The open area of the mesh has a great effect on the passage of paste through the screen. For ease of passage, meshes having the greatest percentage area should be selected. Open area is calculated as: Equation 1 Apart from material, the mesh is specified by mesh count (number of threads per inch), thread diameter, and the type of weave. Printing screens are made from square weave mesh and several types are available, some of which are illustrated in Figure 3. Of these, the most widely used is the plain weave type. 67 MSE 313 Spring 2011 (a) (b) (c) Figure 3: Some common weaves for wire mesh: (a) plain, (b) twill, (c) Hollander. Screen tension is the tension necessary to stretch the mesh sufficiently to cause the screen to peel away from the substrate after printing but not to be stretched so much to cause the damage. Figure 5 shows force vs. elongation curve for stainless steel mesh. Figure 4: Mesh elongation vs. tension The elastic limit is at 1% elongation, so if a stainless steel wire is stretched by less than 1% and released, it will return to its original length. If it is stretched by more than 1% and released, it will remain somewhat stretched. If the mesh is elongated by 0.9% there is still 0.1% in reserve before elastic limit is reached. If it is elongated by 0.5%, there is still 0.5% in reserve. The advantage of using the higher of the recommended tensions is that smaller gap must be used between the screen ad the substrate. The high tension causes the screen to peel readily from the substrate even at small gaps. The disadvantage of using high tension is that the screen works at the point of being overstretched and the slightest carelessness by the operator can destroy the screen. Stencils: In classic screen-‐printing, the stencil’s role is to define the shape of the pattern to be printed on the substrate. In thick film applications the stencil also has a secondary role of having a major influence on the print thickness. Thicker stencil results in a thicker print. Stencils can be made with metal masks, plastic sheets or photo-‐emulsions. 68 MSE 313 Spring 2011 Emulsion: The emulsions are water-‐soluble polymers based on polyvinyl alcohol (PVA) and a sensitizer, which, when exposed to ultra-‐violet (UV) radiation, become insoluble. Hence, if a photo-‐positive is placed on the photo-‐emulsion and exposed to UV, the areas that are exposed will become insoluble while areas shadowed by the photo-‐positive’s opaque areas will remain soluble. Washing with water reveals the desired pattern created in the stencil (Figure 6). Figure 5: A calendared mesh with emulsion imaged with (a) 50 μm lines at 100x, and (b) 40 μm lines & 100 μm vias at 220x. (Images from Sefar Printing Solutions, Ref. 8) Once the screen has been coated with the emulsion and dried, the positive is centered with its emulsion in contact on the screen (Figure 7). frame emulsio n stencil, mesh (a) (b) Figure 6: (a) Back and (b) front of the screen with the exposed emulsion and revealed stencil pattern. Photo-‐emulsions come in two different forms, either as a liquid (known as direct emulsion), or as a dry film coated onto a plastic backing sheet (known as indirect emulsion). Direct emulsions are applied in liquid form directly to the screen wires. Indirect emulsions are usually on a sheet of Mylar, or other type of release paper, and are applied by moistening the release paper with either direct emulsion or with water, and then applied to the wires. When dry, the release backing is peeled away. 69 MSE 313 Spring 2011 Squeegees: Squeegee is a rubber blade that performs the following three tasks: pressing the screen into line contact with the substrate; pushing paste down into the stencil and on to the substrate; cutting the paste level with the top of the screen. Angle of Attack: Most printers use squeegee blades with a Shore Durometer hardness in the range 45-‐ 90. In order to push the paste into the stencil and to shear it at the screen’s top surface, an angle of attack at the squeegee tip of around 45° is used. Much steeper angles give insufficient filling of the stencil, while much shallower angles give erratic shearing and hence poor thickness control. As the angle of attack becomes shallower, hydro-‐dynamic pressure increases and causes an increase in print thickness. The high pressure in the fluid causes it to flow back past the squeegee, thus increasing print thickness (Figure 8). Figure 7: High squeegee pressure causing the paste to flow back under squeegee edge, increasing print thickness. The commonly used squeegee shapes include a knife-‐edge section, the diamond section and the blade or trailing edge section (Figure 8). (a) (b) (c) Figure 8: Squeegee shapes: (a) knife-‐edge, (b) diamond, (c) trailing edge. 70 MSE 313 Spring 2011 Part 1a: Print/ Dry/Fire Resistor Circuits Objective: The purpose of this laboratory is to screen print, dry and fire thick film circuits made of conductive ink. This lab is designed to introduce students to the technology of printing thick film and hybrid circuit using a screen printing machine. The fundamentals of the equipment, inks, and thick film materials processing will be explored. Introduction: Thick Film Conductor: Besides providing low resistance connections between circuit elements, thick film conductors can perform functions such as: providing device mounting pads for bonding, forming terminations for printed resistors, acting as pads for lead frame attachment or as printed capacitor electrodes. Thick film conductor compositions consist of three components: finely divided metals powder, small quantity of glass frits, and an organic vehicle which carries the glass material until the firing stage of thick film. The properties of an organic vehicle, when processed correctly, do not affect the properties of the fired track. It is the permanent constituents of the ink, namely, the metal, bonding oxides, and the glass frit, that play the key role in the final properties of a thick film. Microstructure of a fired conductor, shown on Figure 11 (a-‐b) reveals a continuous array of metal particles, through which runs a secondary network of glass frit. The concentration of glass frit tends to increase near the substrate and sometimes forms a continuous layer at the interface. (a) (b) Figure 9: (a) Microstructure of a fired conductor, (b) a simplified structure of a thick film conductor. This glass reacts with the substrate materials and bonds the sintered metal particles to it, mainly by mechanical keying into the metal. The glass is therefore the main factor controlling the adhesion strength of the sintered composite. The metal, on the other hand, is responsible for electrical and metallurgical properties, whereas combination of both, the metal and the frit, controls compatibility, solderability, and bondability. 71 MSE 313 Spring 2011 Frit Material: Glass softening point: Frit materials used in thick film inks are low softening temperature glasses. Glasses do not have an ordered atomic structure, but retain, even as solid, an interatomic structure similar to that of a liquid. Consequently, the do not exhibit a definite melting point, as would a crystalline material, but soften gradually with increasing temperature until a point is reached where there is detectable flow and the glass have melted. This point is the glass softening point or its working temperature. Frit reactivity: The frit must be sufficiently reactive to form a strong chemical bond with the substrate material; however, it should have limited reactivity towards the metallic components of the ink, as modification of the surface structure of the powder particles could affect their sintering behavior and properties of the fired composite. Wetting: To keep the powder particles in place during the sintering process, it is desirable to maintain a certain amount of wetting of the metal by the molten glass. The degree of wetting and the quantity of frit should not result in complete glass coverage of the metal surfaces, as this would prevent metal-‐to-‐metal contact and result in a highly resistive material. Frit % content: Typical conductor composition contains up to 10% by weight of frit material, which slightly reduces the conductivity of the sintered metal compact by reducing the effective cross-‐section of the fired track. Glass content approaching 50%, results in formation of a matrix of the composite and rapid increase in resistivity. Frit compatibility: The glass should be chemically compatible with other thick film materials such as resistors, and its thermal expansion should match that of the substrate or dielectric in the temperature range from setting point of the glass (usually about 500°C) down to the lowest temperature, at which completed circuit operates. Thermal expansion mismatch would result in a highly stressed system, with poor adhesion and poor resistance to thermal shock and thermal cycling. In worst cases, cracking or peeling of the conductor track would occur. Conductive Material: The metals used in thick film conductors are normally selected on the basis of conductivity and compatibility with the process. They must be able to sinter properly at normal thick film firing temperatures in air and in the presence of molten oxide glasses. They also must not react with the frit so that glass maintains its ability to form a strong bond to the substrate. In practice, for air firing, only noble metals such as sliver (Ag), gold (Au), palladium (Pd), and platinum (Pt) are used. 72 MSE 313 Spring 2011 Deposition of the conductor paste: Printing of thick film conductors is usually less difficult than that of resistors or dielectrics. The main challenge lies in the design of stencils and control of ink rheology to avoid loss of pattern definition and bridging of narrow gaps between conductors. Print quality can be controlled by several factors. For example, speeding up the squeegee traverse speed increases deposit thickness and improves print definition, whereas reduction of squeegee print pressure also increases deposit thickness. Screen printing of conductors below 100μm (~5mils) line width and space can be problematic; however, lower limit of 50μm (~2mils) can be achieved with extremely well controlled procedures. Drying and firing of thick film conductor: Firing reactions can be divided into three groups: (a) removal of the organic printing vehicle; (b) melting of frit and development of the bond with the substrate; and (c) alloying and sintering of the conductive metal particles. The removal of the organic binder takes place early in the firing cycle, and is followed by the frit, oxide and metal reactions which occur simultaneously in the high temperature of the process, normally at 850°C. This is shown in Figure 10. Figure 10: Thick film firing cycle showing the various stages of film formation as a function of temperature. Organic Vehicle Removal: Most of the volatile (solvent) components of the vehicle are normally removed by low temperature drying at temperatures in the range 125-‐150°C, but a large amount of organic (resin) material remains in the printed deposit. This must be removed at relatively low temperatures to avoid excessive carbonization and retention of carbon until high temperatures. The early part of the firing cycle must, therefore, provide adequate time at low temperatures to ensure complete burn-‐off of the organics. No organic burn-‐out product s should remain at temperatures >500°C. Ideally, 3, 4-‐zone belt furnace should be used in firing of thick film, as shown in Figure 11. 73 MSE 313 Spring 2011 Figure 11: Arrangement of air flow though belt furnace to ensure full burn-‐out of organic constituents. Bonding Reactions during Firing: Frit reactions: At the optimum firing temperature, the frit should melt and react with the substrate to form a strong chemical bond, and it should form a semi-‐continuous network within the glass/metal composite. Under-‐firing may result in loss of adhesion due to incomplete bonding with the substrate and over-‐firing may cause excessive removal of glass from the metal. To avoid reactions between the frit and organic binders, the furnace should be set to the upper limit of 500°C, above which the air in the furnace is free from burn-‐ out contamination. Any carbon, retained due to improper firing, can cause reduction of the frit components and production of carbon monoxide or carbon dioxide gas, which may cause pinholes or bubbling in the composite. Metal Reactions during Firing: There are two major metallic reactions that occur during firing: (1) sintering of the individual particles to form continuous metal conduction path through the glass/metal composite, and (2) alloying of mixed metal powders. Both processes have an effect on the metallurgical and electrical properties of the conductor. These temperature-‐ dependent reactions require the transport of materials in the solid state. The driving force is the lowering of the total energy of the system and in sintering this is mainly achieved by reduction of the surface area of the metal particles. Initially, the particles are only in point contact, but as temperature increases, the particles join together, forming necks at these points. As the necks develop, the composite shrinks and the bulk density of the material increases. As temperature increases, vacancy diffusion predominates, which is caused by the greater disorder of the crystal lattice at higher temperatures, and by the decrease in the number of grain boundaries due to grain growth. Measurements of these self-‐diffusion rates for pure silver have shown that the change occurs at ~750°C. Reactions during Cooling: The final stage of the firing process involves cooling from the firing temperature back to the ambient one. Cooling rates should not exceed 100°C/min. as higher rates can cause thermal shock damage to the substrate or to the substrate/frit bond. 74 MSE 313 Spring 2011 Experiment: Print Conductor: NOTE: use conductive paste and the screen with the conductor pattern. Set up for Printing: • Turn main air on and check pressure regulator (should read between 60-‐70 PSI). The printer carriage will slowly lift, as the pressure reaches the desired level. See figure 18 below for details. • Place the squeegee carriage onto bearing block and tighten the thumb screws (the squeegee carriage has two acceptance holes which should align with the “O” rings in the right-‐hand bearing block; the squeegee blade itself will be mounted to the squeegee blade holder prior to the experiment). • Assemble screen to the screen box by attaching the four screen clamp assemblies to the print head side rails. Position the screen over the two dowel pins in the bottom of the print box and tighten the clamps securely. • Turn the vacuum pump on to approximately 1.2 SCFM vacuum at 17-‐20”/Hg (lower value is acceptable). Place a substrate in position on the substrate plate; align it with two pins. Vacuum should keep the substrate in place (Figure 12). Figure 12: MSE Screen Printer. Vacuum attached to the substrate stage to keep the substrate in place during screen printing. 75 MSE 313 • • Spring 2011 Loosen the locking levers and adjust the snap-‐off distance (see locations of the appropriate adjustment knobs and levers on figure 20). To obtain exact snap-‐off, the screen should be brought down to contact the substrate. Then move the bezel on the dial micrometer to read zero. Move screen upwards until dial micrometer reads exact snap-‐off required. Align substrate with the screen image by using X, Y, and φ adjustment on the stage (Figure 20). NOTE: Never move any of the adjustments with the stage locked as this could result in irreversible damage to the X-‐Y stage. The Printer is now ready to test print. Test Printing: • Using spatula, deposit ink (approx. 1 tsp. amount) onto the screen (NOT on the pattern itself). • Press the foot pedal. The printer head will come down when the pedal is pressed, and the squeegee will deposit the ink by pressing the screen and moving across the substrate. When the front stop is reached, release the pedal. The printer head will rise simultaneously with the flood blade going back. • Check the quality of the print on the substrate. It the film is too thin or too thick, remove the substrate from stage (vacuum may be turned off for that purpose) and wipe off the paste using wipes and cleaning alcohol. Put the substrate back on the stage and turn the vacuum back on. Remove the remaining paste from the screen and place it into the ink jar. Clean the screen with wipes and alcohol by pressing gently onto the screen from both sides (follow TA’s instructions to clean the screen properly). • NOTE: The first few test prints will have to be rejected since the screen will not be thoroughly wetted and thixotropic inks will not have attained a stable viscosity. • After making test print substrate, minor additional adjustments may be required. Adjustments may include: registration of the print, proper ink deposition, print speed, stage settings (X, Y, φ), snap-‐off distance, and squeegee level. Repeat Steps 7 through 10 until satisfactory print is received (Figure 15). • Figure 12: Example of a satisfactory print of silver conductor. 76 MSE 313 Spring 2011 • • • One person from the group should proceed to Step 11, while others move on to Experiment 1.2. Remove squeegee holder from the printer head and recover as much ink as possible (Figure 22 a-‐c). Recover paste from the screen. Clean the screen and squeegee thoroughly with alcohol. NOTE: Cleaning of the screen is important, as any remaining ink can affect the edge definition and surface of patterns printed the next time. (a) (b) (c) Figure 13: Removal of squeegee holder (a, b), and ink recovery (c). Experiment: Settle & Dry Conductor: • Place the substrate on a flat, dust-‐free surface (Figure 23a) and allow the ink to level for 5-‐10 minutes. • Using thermocouple set the temperature of a hot plate to 125°C-‐150° (Figure 23b). Allow 10 minutes for the hotplate to reach the desired temperature. Place the substrate on a hot plate or in the drying oven. and allow the ink to dry for 10-‐ 15 minutes. (a) (b) Figure 14: (a) Leveling of the wet ink. (b) Setup for drying the paste. 77 MSE 313 Spring 2011 Part 1b: Print/ Dry Resistor: Objective: The purpose of this laboratory is to screen print and dry thick film resistors. This lab is designed to allow students practice screen and stage alignment to obtain patterns at precise locations on the substrates. Introduction: Thick Film Resistor: Three most important properties of thick film resistors are: (a) sheet resistance, Rs (b) temperature coefficient of resistance, TCR, and (c) drift, the percentage change in value with time under specific conditions. Sheet resistance is the resistance of one square of material of known thickness. It equals bulk resistivity/film thickness (ρ/t=Rs) and has units of ohms, but for clarity, it is referred to as ohms/square to avoid confusion with ordinary resistance. Temperature coefficient of resistance is the slope of the line showing resistance as a function of temperature (R vs. T) over a specified range, T1 to T2. If the values are R1 at T1 and R2 at T2, then, measured in parts per million per degree Celsius: TCR = (R2-‐R1)*106 / R1(T2-‐T1) ppm/°C Equation 2 Drift is defined as (ΔR/Ro)% under stated conditions after a specified time, where Ro is the starting value. Almost all commercially used thick film resistor systems have contained one of the three precious metal oxides or their derivatives. These are palladium oxide (PdO), ruthenium dioxide (RuO2), and iridium dioxide (IrO2), with the second one used the most in present days. All conducting phases are degenerate semiconductors with resistivity higher than that of most metals, but a similar positive TCR. All three react with or wet suitable glasses to form the necessary reactive cermet. The glass constituents usually include silica (SiO2), boron oxide (BO), manganese dioxide (MnO2), zinc oxide (ZnO) and trace amounts of copper oxide (CuO). Deposition of the resistive paste: During the printing process in the production of thick film resistors, the aim is to deposit on the substrate a uniform layer of resistor material of the correct thickness and dimensions. Uniformity and reproducibility are very important, thus screen and stencil materials need to be chosen carefully. Stainless steels screens are used most commonly because they provide good dimensional stability. For printing resistors, screens of mesh 200, 250 and 325 are used. To print especially thick layers, coarser screens, 165 mesh, are sometimes used. Using finer screens, for example 400 mesh, provides a very good edge and shape definition. The final results of resistor printing depend on the processing are and the environmental conditions, and they should be done in the rooms at temperatures 20-‐24°C, and humidity of 40 to 60%. 78 MSE 313 Spring 2011 Settling and Drying: Just after printing, the resistor is in the form of a matrix of small dots which flow together in a few seconds to form a uniform print. In order for this flow to complete successfully, the prints should be allowed to settle for 5-‐10 minutes before drying. This can be done by placing the substrate lying flat in a cool, dust-‐free place. At this stage, solvents contained in an organic vehicle are no longer needed. They are removed by drying of the print. Drying is usually done in an oven under an infra-‐red dryer with a substrate temperature between 100 and 200°C for 15 minutes. Experiment: Print Resistor: • NOTE: use resistive paste and the screen with the resistor pattern. • Same as in Part 1. Additionally, make sure that the pattern of the resistor is aligned with the pattern of the conductor. (a) (b) Figure 15: (a) Removing the resistor ink from its container; (b) Reapplying the paste onto a wet screen. • Same as in Part 1. Printing of the resistor layer (or any layer that is deposited as the second one) can be more challenging, because the pattern needs to be correctly aligned with the first layer of conductor tracks. Therefore, it is a good practice to examine the final layout of the circuit beforehand. • If the obtained print is unsuccessful, wipe the wet resistor ink off with alcohol and wipes (Figure 27a, b). This step is allowed because the conductor tracks have been fired, and thus, they stay intact with the substrate. 79 MSE 313 Spring 2011 (a) (b) Figure 16: (a), (b) Cleaning the substrate after an unsuccessfully printed resistor. Figure 17: Example of a satisfactory print of resistor. Experiment: Settle & Dry Resistor: To level and dry resistor paste, follow Step 12-‐13 in Part 1 Part 3a: Fire Resistor/Firing Profiles: Objective: The purpose of this laboratory is to fire thick film resistors. This lab is designed to obtain and study different firing cycles of the resistors and to determine the effect of firing temperatures on the resistors’ performance. Introduction: Firing of thick film resistor: NOTE: Measure the overall dimensions of the components after they have completely dried, but before firing to determine the % shrinkage. After printing, settling and drying, thick film resistors are fired to completely form a resistor. At the first stage of firing, the remaining vehicle components are evaporated and burn out. As the temperature reaches 500°C, the glass softens and melts, and the sintering process begins. The assistance of the melted glass is very important especially in the case of resistors with the active phase, such as ruthenium dioxide or ruthenates, which have high melting point and are resistant to sintering. The liquid phase of glass allows for sintering of that active phase. This process is responsible for creating the 80 MSE 313 Spring 2011 micro contacts between the grains and it affects final property a typical firing profile of the resistive layer. Figure 21 shows schematically a typical firing profile for resistors with peak temperature 850°C and overall firing time 60 minutes. Commonly, the heating rate is about 50°C per minute, time at peak 10 minutes, and cooling rate about 50°C per minute. Figure 18: Schematic of firing profile for resistors Experiment : Fire Resistor: Place the substrate in the furnace and run the appropriate program to fire thick film. Use Table 3 for guidelines on programming a furnace in order to match a particular firing profile. Ideally, firing of thick films should be done using a conveyor belt furnace, in which a substrate can be fired and cooled at much higher rates than in the box furnace. Using box furnace may cause delays in ramping segments. Table 2: Guidelines to program a furnace to match thick film firing profile. Segment No. 1 Duration (minutes) 1 Temperature range (°C) 0-‐25 Ramp Rate (°C/min.) 10 2 5 at 25 0 Recommended Programming Step Raise temperature to ambient 25°C Hold for 5 minutes at 25°C 3 13 25-‐850 63.5 Raise temperature to 850°C 4 10 at 850 0 5 6 13 18 850-‐125 125-‐100 55 1.4 -‐-‐-‐ Total: 60 minutes -‐-‐-‐ -‐-‐-‐ Hold for 10 minutes at 850°C Cool down to 125°C Reset to ambient temperature -‐-‐-‐ 81 MSE 313 Spring 2011 Once the cooling stage initiates, apply air connected through the vent on the back of the furnace. Slightly open the door of the furnace, allowing air and other remaining residues to escape . Remove the substrate from the furnace after the full firing cycle is complete. (a) (b) (c) (d) Figure 19: Four different thick film design layouts to be printed and tested. Resistors are located in the mid-‐section of each pattern. 82 MSE 313 Spring 2011 Part 2: Resistance Measurements of Thick Film Patterns / Thick Film Pattern Design and Analysis: Objective: The purpose of this laboratory is to study aspects of thick film design and layout. The students will examine the patterns of printed/fired thick film circuits obtained from Part 1. Factors such as geometry, sheet resistance, print thickness and electrical performance will be studied and students will compare calculated theoretical results with the experimental data. Introduction: Design and layout of hybrid circuits include making preliminary decisions before a detailed design is started, which are then followed by the actual layout procedures. Motivation for Use of Hybrids: A system designer who chooses to include hybrids in part of the design considers the aspects of thick film hybrids such as reduction in size and weight, uniformity of assembly, increase in reliability, choice of materials that enhance resistance to thermal, mechanical and chemical stresses, ability to make easily non-‐standard assemblies, possibility of cost reduction, ease of addition of specialist components and other. General Layout Principles: Design of the thick film layouts may begin with the discussion from the viewpoint of the pattern production, rather than from the electrical design demands. All tracks should be laid out orthogonally and should be as short as it makes them practical. Track widths and separations should be chosen to be compatible with the screens being used. Coarser screens result in printing more paste in a thicker layer, and if the wrong combination is used, the slump may affect the yield during leveling. Using very fine screens, on the other hand, produces accurate patterns which are thinner, but they may become subject to resistive losses. Layout Procedure, Track Layout: The main objective in any layout is to turn the circuit diagram into a viable 2-‐ dimensional representation of it with as few crossovers as possible. In the manual design, one first draws by hand non-‐dimensional patterns to get a sense of the viable layout. From there, an accurate layout can be done using graph paper. In the other, more common approach, all manually-‐made layers of the layout are translated into an engineering CAD program such as Autocad. Some of the layout design principles include: Confirm shape and size of the substrate. Choose type of connection (e.g. solder, wire bonding). 83 MSE 313 Spring 2011 Recalculate and decide on final resistor design (target value in ohms; list possible values for sheet resistance, length, and width). Assign layers for the substrate (the Real appearance in the product and Virtual look are part of the design procedure and are not actually fabricated). The number of resistor layers may range from 0 to 3. Crossovers may require 2 conductors and a dielectric. Additional conductors of a different metal may be needed for soldering and bonding. Master Patterns: The outcome for all real layers is the life-‐size photopositives of final patterns that are to be screen printed. In manual approach, a two-‐layer material is used. Its soft red layer is accurately scribed and peeled to make a master pattern at 10x magnification. This is then reduced photographically to 1x on either a high resolution film or a glass positive. In the CAD approach, the print is made on a film using photo-‐plotter either directly at life size or by the method described above, depending on the required accuracy. Thick Film Components: Conductors: General design rules for thick film conductors are not summarized here . Dimensions of conductor tracks depend on the material used. For low-‐cost applications 0.5 mm line and space is typical. Resistors: Resistors tend to be subject to dimensional problems. Their thickness tends to be greater near contacts and the effective value of sheet resistance may depend on the track length. For conventional resistors, the value of resistance is determined by three factors – the effective sheet resistance (usually determined by the ink manufacturer), length, and width. Sheet resistance is the resistance of one square of a material, regardless of the actual side dimensions. It is derived from the volume resistivity and is equivalent to ρ/t (see Part 1, Exp. Procedure 2), where t is the thickness of the conducting material. Thus, resistance R is defined as: R = (ρ/t) * (L/W) = Rs * (L/W) Equation 3 where ρ is material’s bulk resistivity, L is length, W is width, L/W is the aspect ratio, expressed in units of squares ( ’s) and Rs is the sheet resistance, expressed in units of ohm/square (Ω/ ). In Figure 30, the aspect ratio is approximately 1.5:1 for the over square and 1:3 for under square resistors, respectively. If the fired sheet resistance is 1000 Ω/ , then the R values become 1500 Ω and 333 Ω, respectively. 84 MSE 313 Spring 2011 Figure 20: Over square and under square thick film resistors. Resistors have a maximum film temperature for operation and this is related to the power density. The traditional value is ‘40W/square inch of track’, which is equivalent to 64mW/mm-‐2. To avoid taking too much space, the range of aspect ratio in a printed resistor before trim is limited to approximately 0.2-‐5.0. This range results in about 5 mm maximum length or width of the resistor. To make a feasible print, the number of different sheet resistances used on one substrate should not exceed three. Design rules for thick film resistors include the following factors: L = Length W = Width A = Printed area = L x W P = Designer’s power dissipation (mW) R = Target resistor value (Ω) RD = Design value of resistor (e.g., 0.75 x R) N = Aspect ratio printed (L/W) RS = Chosen sheet resistance The following rules apply to the resistor design: RD = 0.75 x Target RD = RS x (L/W) A = L x W P/A = 32 mW mm-‐2 L ≥ 1 mm W ≥ 1 mm ND = range approx. 0.2-‐5.0 RS = Range from 10, 100, 1000, 10000, 100000, 1000000 Ω/ . The design shape of the resistor is calculated from Equations (4) and (5), below. W = √{(P * RS) / (32 * RD)} Equation 4 L = √{(P * RD) / (32 * RS)} Equation 5 No resistor should be located closer to the substrate edge than 1 mm. There should be at least 1.5 mm between individual resistor stripes, and no conductor track should approach the stripe closer than 1 mm. In practice, a series of resistor test patterns is prepared and screen printed (Figure 25) in order to determine the resistor optimum dimensions for the particular resistive inks. 85 MSE 313 Spring 2011 Figure 21: Selection of typical resistor test patterns. Resistors of same width, varying length and resistors of same length, varying width. Standard resistors for loading tests. Resistors of same aspect ratio, varying area, enabling effects of resistor position on substrate to be investigated. As (b) but with conductor stripe in the center overlaid with resistor material to explore interactions. Resistors of same length but widely varying widths for detailed examination of width effects. Small resistors. 86 MSE 313 Spring 2011 Part 3: Characterization. In this lab students will test the various resistors made previously using LabVIEW and standard data acquisition apparatus as well as determine thickness with a profilometer. These measurements will be demonstrated by the lab instructor. Analysis part 1: • Take the fired circuits to the profilometer to gain thickness measurements. • From this determine the cross-‐sectional area of each resistor. Do not include areas where resistor is overlapping conductive material. Analysis Part 2: Use Fluke Meter • Carefully snap the substrate along the inscribed lines and obtain four separate substrates with various screen printed thick film circuits (Figure 26 a-‐d). • Examine all four substrates using the following guidelines: • Substrate (a): -‐ Determine aspect ratio of each of the five circuits and calculate their theoretical resistance values (to obtain sheet resistance, Rs use the vendor’s Data Sheet for the resistor paste used). -‐ Using ohmmeter, measure the actual resistance values of each of the five circuits. • Note: In order to correctly measure resistor dimensions, do NOT include the area where resistor is printed over another ink. • Substrate (b): • Repeat the calculations and measurements, as for Substrate (a). • Substrate (c) – Parallel Resistors: -‐ Using approach above, calculate total resistance of printed thick film parallel resistor. -‐ Using ohmmeter, measure the actual resistance of the circuit. • Substrate (d) – Resistors in Series: -‐ Using approach above, calculate total resistance of printed thick film resistor in series. -‐ Using ohmmeter, measure the actual resistance of the circuit. Analysis Part 3: Temperature dependence: For this section, follow the basic principles outlined in Analysis Part 2 above, but choose at least five temperatures at which to conduct the measurements. From this data calculate the TCR of the resistor. Next prepare an Arrhenius plot to find the activation energy. Analysis Part 4: Conductor/Resistor interface resistance: 1. Draw a diagram of your circuit . 2. Create a circuit diagram of the resistances 87 MSE 313 Spring 2011 3. Consider what assumptions are necessary to determine the resistance of the interface vs. the resistance of the resistor only. Consider what is measured and what must be computed. 4. Find the resistance of each part. (remember ohms law!) Questions: 1. Discuss any problems encountered during print, for example, cleaning the screens, aligning the screen with the substrate, etc. 2. How did the thickness and room temperature resistivity measurements between the fired samples compare with the measurements at other temperatures? 3. By how much did the patterns shrink after firing? 4. Note any defects of unusual morphology of the fired sensors. Was there any cracking? Discoloration? , Etc Instead of a lab report students will put together a poster that lays out the principles of the lab and the results. Include information obtained from independent research regarding screen printing in the electronics industry and advances that have been made. Include a summary of all results. References: • • • • • • • • • • • • Marciniak, M., “Screen Printing of Thick Film Materials” Senior Project Report, March 2008. Kasap, S.O., “Principles of Electronic Materials and Devices” 3rd edition. McGraw Hill, 2006. ESL ElectroScience, Thick Film Materials & Ceramic Tapes, <http://www.electroscience.com/index.html>. Date accessed: July 20th, 2007. Holmes, P. J., Loasby, R. G., Handbook of Thick Film Technology, 1st ed. Electrochemical PublicationsLimited, 1976. Jones, D., Roydn, Hybrid Circuit Design and Manufacture, International Society for Hybrid Microelectronics, 1982. Koartan, Microelectronic Interconnect Materials, < http://www.koartan.com/>. Date accessed: July 20th, 2007. Missele, Carl. Screen Printing Primer, Microcircuit Products, Motorola Inc., Reprinted from Hybrid Circuit Technology, 1987. Pitt, Keith, Handbook of Thick Film Technology, 2nd ed. Electrochemical Publications Limited, 2005. Screen Printer Operation Manual for de Haart SP-‐SA-‐5/6 Screen Printers, 1978. Seafar Printing Solutions, Inc., <http://www.sefar-‐screens.com/>. Date accessed: September, 2007. 88 MSE 313 Spring 2011 Blank Page 89 MSE 313 Spring 2011 Junior Lab Project: The Jr. Lab Project will be covered in the first session of MSE 313. See Appendix for relevant forms on following pages. Un-‐numbered Appendix follows. 90 MSE 313 Team Project Assignments Section Morning Afternoon TA Aaron Lichtner Evan Uchaker Email [email protected] [email protected] Requirements – sent to respective TAs unless otherwise stated. 1. Project Milestones 2. Weekly Progress Reports Milestones: Week 1 Redefine Project and Budget Week 2 Weeks 3-‐4 Project Plan Week 5 Intro and Background Due Weeks 6-‐8 Week 9 Final Papers Due Week 10 Project Presentations Week 1 (Due Tuesday 3/29): • Submit altered project summary (max 1 page) • Requisition of Supplies (form) o Use proper requisition form o Send to Tuesday • Materials needed (max 1 page) o To be sent to Tuesday and your respective TAs. Make sure to use ACCURATE values for all requested purchases. Week 2 (Due Tuesday 4/5): • Detailed Project Plan o Include breakdown of work o Project timeline, milestones Week 5 (Due Tuesday 5/3): • First Draft of Project Introduction and Background to be used for final paper o Include cited sources Week 9 (Due Friday 5/27): • Submit Final Paper Week 10: • Project Presentations Weekly Progress Reports Due Weekly: Max 1-‐2 pages Each team must complete a weekly progress report to be turned into their respective TA. Progress report authors will rotate weekly so that every team member does at least one report. Progress reports must include: 1. Work accomplished that week broken down into individual team member tasks 2. Work planned for the following week (general team) 3. Potential roadblocks that will hold up your research or progress. Examples are lead time on equipment, need for training, scheduling conflicts… 4. Summarized piece of literature found that week including cited source OR data taken that week properly formatted, captioned, and explained o Once data is being generated you must present data Suggested Progress Report Layout Date Team Member Project Work Completed: Work Planned: Potential Roadblocks: Literature or Data Review: MSE 313 2011 SUPPLY & SERVICES REQUISITION (Please fill in blanks) Requested by: Authorized by: Project Title: Date: X Group & No.: X Group Group Group Group Group Quantity Requisition #: 1 2 3 4 5 Page #: Item (please be specific) Vendor* & Catalog Number Price Each Print and fill out this form to request supplies or services. For estimates of cost of services please use the MSE User facility. For supplies please investigate costs online, you can get this information from web pages like McMaster Carr, VWR, Lab Safety Supply, and Alfa Aeser. Some suppliers require an account to get pricing information so assign one person in your group to do so. Any supplies requested that the department has on hand can be provided, but cost assesment is still required. Designation: E399 – 09´2 Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness KIc of Metallic Materials1 This standard is issued under the fixed designation E399; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. ´1 NOTE—Eq A3.4, Eq A4.4, Eq A5.4, and Eq A6.11 were editorially corrected in May 2010. ´2 NOTE—11.2 and 11.4 were editorially corrected in December 2010. 1. Scope 1.1 This test method covers the determination of fracture toughness (KIc) of metallic materials under predominantly linear-elastic, plane-strain conditions using fatigue precracked specimens having a thickness of 1.6 mm (0.063 in.) or greater2 subjected to slowly, or in special (elective) cases rapidly, increasing crack-displacement force. Details of test apparatus, specimen configuration, and experimental procedure are given in the Annexes. NOTE 1—Plane-strain fracture toughness tests of thinner materials that are sufficiently brittle (see 7.1) can be made using other types of specimens (1).3 There is no standard test method for such thin materials. 1.2 This test method is divided into two parts. The first part gives general recommendations and requirements for KIc testing. The second part consists of Annexes that give specific information on displacement gage and loading fixture design, special requirements for individual specimen configurations, and detailed procedures for fatigue precracking. Additional annexes are provided that give specific procedures for beryllium and rapid-force testing. 1.3 General information and requirements common to all specimen configurations: Referenced Documents Terminology Stress-Intensity Factor Plane-Strain Fracture Toughness Crack Plane Orientation Section 2 3 3.1.1 3.1.2 3.1.3 1 This test method is under the jurisdiction of ASTM Committee E08 on Fatigue and Fracture and is the direct responsibility of Subcommittee E08.07 on Fracture Mechanics. Current edition approved July 1, 2009. Published August 2009. Originally approved in 1970. Last previous edition approved in 2008 as E399 – 08. DOI: 10.1520/E0399-09E02. 2 For additional information relating to the fracture toughness testing of alumi– inum alloys, see Practice B645. 3 The boldface numbers in parentheses refer to the list of references at the end of this standard. Summary of Test Method Significance and Use Significance Precautions Practical Applications Apparatus (see also 1.4) Tension Machine Fatigue Machine Loading Fixtures Displacement Gage, Measurement Specimen Size, Configurations, and Preparation (see also 1.5) Specimen Size Estimates Standard and Alternative Specimen Configurations Fatigue Crack Starter Notches Fatigue Precracking (see also 1.6) Crack Extension Beyond Starter Notch General Procedure Specimen Measurements Thickness Width Crack Size Crack Plane Angle Specimen Testing Loading Rate Test Record Calculation and Interpretation of Results Test Record Analysis Pmax/PQ Validity Requirement Specimen Size Validity Requirements Reporting Precision and Bias Section 4 5 5.1 5.1.1-5.1.5 5.2 6 6.1 6.2 6.3 6.4 7 7.1 7.2 7.3.1 7.3.2 7.3.2.2 8 8.2.1 8.2.2 8.2.3 8.2.4 8.3 8.4 9 9.1 9.1.3 9.1.4 10 11 1.4 Specific requirements related to test apparatus: Double-Cantilever Displacement Gage Testing Fixtures Bend Specimen Loading Fixture Compact Specimen Loading Clevis Annex A1 Annex A2 Annex A2.1 Annex A2.2 1.5 Specific requirements related to individual specimen configurations: Bend Specimen SE(B) Compact Specimen C(T) Disk-Shaped Compact Specimen DC(T) Arc-Shaped Tension Specimen A(T) Arc-Shaped Bend Specimen A(B) Copyright. © ASTM International. 100 Barr Harbour Drive PO box C700, West Conshohocken, Pennsylvania 19428-2959, United States Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 1 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. Annex A3 Annex A4 Annex A5 Annex A6 Annex A7 E399 – 09´2 1.6 Specific requirements related to special test procedures: Fatigue Precracking KIc Specimens Hot-Pressed Beryllium Testing Rapid-Force Testing Annex A8 Annex A9 Annex A10 1.7 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. Referenced Documents 2.1 ASTM Standards:4 B909 Guide for Plane Strain Fracture Toughness Testing of Non-Stress Relieved Aluminum Products B645 Practice for Linear-Elastic Plane−Strain Fracture Toughness Testing of Aluminum Alloys E4 Practices for Force Verification of Testing Machines E8/E8M Test Methods for Tension Testing of Metallic Materials E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods E337 Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures) E456 Terminology Relating to Quality and Statistics E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method E1820 Test Method for Measurement of Fracture Toughness E1823 Terminology Relating to Fatigue and Fracture Testing E1921 Test Method for Determination of Reference Temperature, To, for Ferritic Steels in the Transition Range 3. Terminology 3.1 Definitions:Terminology E1823 is applicable to this test method: 3.1.1 stress-intensity factor, K, KI, KII, KIII [FL−3/2]— magnitude of the ideal-crack-tip stress field (a stress-field singularity), for a particular mode of crack displacement, in a homogeneous, linear-elastic body. 3.1.1.1 K is a function of applied force and test specimen size, geometry, and crack size, and has the dimensions of force times length-3/2. 3.1.1.2 Values of K for modes I, II, and III are given as: KI 5 lim @syy~2pr!1/2# r→0 (1) KII 5 lim @txy~2pr!1/2# r→0 (2) 4 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [email protected]. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website. KIII 5 lim @tyz~2pr!1/2# r→0 (3) where r is the distance directly forward from the crack tip to the location where the significant stress is calculated. 3.1.2 plane-strain fracture toughness, KIc [FL-3/2] —the crack-extension resistance under conditions of crack-tip plane strain in Mode I for slow rates of loading under predominantly linear-elastic conditions and negligible plastic-zone adjustment. The stress intensity factor, KIc, is measured using the operational procedure (and satisfying all of the validity requirements) specified in Test Method E399, that provides for the measurement of crack-extension resistance at the onset (2% or less) of crack extension and provides operational definitions of crack-tip sharpness, onset of crack extension, and crack-tip plane strain. 3.1.2.1 See also definitions of crack-extension resistance, crack-tip plane strain, and mode in Terminology E1823. 3.1.3 crack plane orientation—identification of the plane and direction of crack extension in relation to the characteristic directions of the product. A hyphenated code defined in Terminology E1823 is used wherein the letter(s) preceding the hyphen represents the direction normal to the crack plane and the letter(s) following the hyphen represents the anticipated direction of crack extension (see Fig. 1). 3.1.3.1 Wrought Products—the fracture toughness of wrought material depends on, among other factors, the orientation and propagation direction of the crack in relation to the material’s anisotropy, which depends, in turn, on the principal directions of mechanical working and grain flow. Orientation of the crack plane shall be identified wherever possible. In addition, product form shall be identified (for example, straight-rolled plate, cross-rolled plate, pancake forging, and so forth) along with material condition (for example, annealed, solution treated plus aged, and so forth). The user shall be referred to product specifications for detailed processing information. 3.1.3.2 For rectangular sections, the reference directions are identified as in Fig. 1(a) and Fig. 1(b), which give examples for rolled plate. The same system is used for sheet, extrusions, and forgings with nonsymmetrical grain flow. L = direction of principal deformation (maximum grain flow) T = direction of least deformation S = third orthogonal direction 3.1.3.3 Using the two-letter code, the first letter designates the direction normal to the crack plane, and the second letter the expected direction of crack propagation. For example, in Fig. 1(a), the T-L specimen fracture plane normal is in the width direction of a plate and the expected direction of crack propagation is coincident with the direction of maximum grain flow (or longitudinal) direction of the plate. 3.1.3.4 For specimens tilted in respect to two of the reference axes as in Fig. 1(b), crack plane orientation is identified by a three-letter code. The designation L-TS, for example, indicates the crack plane to be perpendicular to the principal deformation (L) direction, and the expected fracture direction to be intermediate between T and S. The designation TS-L means that the crack plane is perpendicular to a direction Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 2 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 (a) Rectangular Sections—Specimens Aligned with Reference Directions (b) Rectangular Sections—Specimens Not Aligned with Reference Directions (c) Cylindrical Bars and Tubes L = direction of maximum grain flow R = radial direction C = circumferential or tangential direction FIG. 1 Crack Plane Identification Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 3 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 intermediate between T and S, and the expected fracture direction is in the L direction. 3.1.3.5 For cylindrical sections, where grain flow can be in the longitudinal, radial or circumferential direction, specimen location and crack plane orientation shall reference original cylindrical section geometry such that the L direction is always the axial direction for the L-R-C system, as indicated in Fig. 1(c), regardless of the maximum grain flow. Note that this is a geometry based system. As such, the direction of maximum grain flow shall be reported when the direction is known. NOTE 2—The same system is useful for extruded or forged parts having circular cross section. In most cases the L direction corresponds to the direction of maximum grain flow, but some products such as pancake, disk, or ring forgings can have the R or C directions correspond to the direction of maximum grain flow, depending on the manufacturing method. L = axial direction R = radial direction C = circumferential or tangential direction 3.1.3.6 In the case of complex structural shapes, where the grain flow is not uniform, specimen location and crack plane orientation shall reference host product form geometry and be noted on component drawings. 3.1.3.7 Non-Wrought Products—for non-wrought products, specimen location and crack plane orientation shall be defined on the part drawing. The result of a fracture toughness test from a non-wrought product shall not carry an orientation designation. 3.1.3.8 Discussion—when products are to be compared on the basis of fracture toughness, it is essential that specimen location and orientation with respect to product characteristic directions be comparable and that the results not be generalized beyond these limits. 3.2 Definitions of Terms Specific to This Standard: 3.2.1 crack mouth opening displacement (CMOD), Vm [L]—component of clip gage displacement taken at the crack starter-notch mouth. · 3.2.2 stress-intensity factor rate, K (FL-3/2t-1)—change in stress-intensity factor, K, per unit time. 4. Summary of Test Method 4.1 This test method covers the determination of the planestrain fracture toughness (KIc) of metallic materials by increasing-force tests of fatigue precracked specimens. Force is applied either in tension or three-point bending. Details of the test specimens and experimental procedures are given in the Annexes. Force versus crack-mouth opening displacement (CMOD) is recorded either autographically or digitally. The force at a 5 % secant offset from the initial slope (corresponding to about 2.0 % apparent crack extension) is established by a specified deviation from the linear portion of the record (1). The value of KIc is calculated from this force using equations that have been established by elastic stress analysis of the specimen configurations specified in this test method. The validity of the KIc value determined by this test method depends upon the establishment of a sharp-crack condition at the tip of the fatigue crack in a specimen having a size adequate to ensure predominantly linear-elastic, plane-strain conditions. To establish the suitable crack-tip condition, the stress- intensity factor level at which specimen fatigue precracking is conducted is limited to a relatively low value. 4.2 The specimen size required for test validity increases as the square of the material’s toughness-to-yield strength ratio. Therefore a range of proportional specimens is provided. 5. Significance and Use 5.1 The property KIc determined by this test method characterizes the resistance of a material to fracture in a neutral environment in the presence of a sharp crack under essentially linear-elastic stress and severe tensile constraint, such that (1) the state of stress near the crack front approaches tritensile plane strain, and (2) the crack-tip plastic zone is small compared to the crack size, specimen thickness, and ligament ahead of the crack. 5.1.1 Variation in the value of KIc can be expected within the allowable range of specimen proportions, a/W and W/B. KIc may also be expected to rise with increasing ligament size. Notwithstanding these variations, however, KIc is believed to represent a lower limiting value of fracture toughness (for 2 % apparent crack extension) in the environment and at the speed and temperature of the test. 5.1.2 Lower values of KIc can be obtained for materials that fail by cleavage fracture; for example, ferritic steels in the ductile-to-brittle transition region or below, where the crack front length affects the measurement in a stochastic manner independent of crack front constraint. The present test method does not apply to such materials and the user is referred to Test Method E1921 and E1820. Likewise this test method does not apply to high toughness or high tearing-resistance materials whose failure is accompanied by appreciable amounts of plasticity. Guidance on testing elastic-plastic materials is given in Test Method E1820. 5.1.3 The value of KIc obtained by this test method may be used to estimate the relation between failure stress and crack size for a material in service wherein the conditions of high constraint described above would be expected. Background information concerning the basis for development of this test method in terms of linear elastic fracture mechanics may be found in Refs (1) and (3). 5.1.4 Cyclic forces can cause crack extension at KI values less than KIc. Crack extension under cyclic or sustained forces (as by stress corrosion cracking or creep crack growth) can be influenced by temperature and environment. Therefore, when KIc is applied to the design of service components, differences between laboratory test and field conditions shall be considered. 5.1.5 Plane-strain fracture toughness testing is unusual in that there can be no advance assurance that a valid KIc will be determined in a particular test. Therefore, compliance with the specified validity criteria of this test method is essential. 5.1.6 Residual stresses can adversely affect the indicated KQ and KIc values. The effect can be especially significant for specimens removed from as-heat treated or otherwise nonstress relieved stock, from weldments, from complex wrought parts, or from parts with intentionally induced residual stresses. Indications of residual stress include distortion during specimen machining, results that are specimen configuration dependent, and irregular fatigue precrack growth (either excessive Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 4 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 crack front curvature or out-of-plane growth). Guide B909 provides supplementary guidelines for plane strain fracture toughness testing of aluminum alloy products for which complete stress relief is not practicable. Guide B909 includes additional guidelines for recognizing when residual stresses may be significantly biasing test results, methods for minimizing the effects of residual stress during testing, and guidelines for correction and interpretation of data. 5.2 This test method can serve the following purposes: 5.2.1 In research and development, to establish in quantitative terms significant to service performance, the effects of metallurgical variables such as composition or heat treatment, or of fabricating operations such as welding or forming, on the fracture toughness of new or existing materials. 5.2.2 In service evaluation, to establish the suitability of a material for a specific application for which the stress conditions are prescribed and for which maximum flaw sizes can be established with confidence. 5.2.3 For specifications of acceptance and manufacturing quality control, but only when there is a sound basis for specifying minimum KIc values, and then only if the dimensions of the product are sufficient to provide specimens of the size required for valid KIc determination. The specification of KIc values in relation to a particular application should signify that a fracture control study has been conducted for the component in relation to the expected loading and environment, and in relation to the sensitivity and reliability of the crack detection procedures that are to be applied prior to service and subsequently during the anticipated life. 6. Apparatus 6.1 Testing Machine and Force Measurement—The calibration of the testing machine shall be verified in accordance with Practices E4. The test machine shall have provisions for autographic recording of the force applied to the specimen; or, alternatively, a computer data acquisition system that may be used to record force and CMOD for subsequent analysis. 6.2 Fatigue Precracking Machine—When possible, the calibration of the fatigue machine and force-indicating device shall be verified statically in accordance with Practices E4. If the machine cannot be calibrated and verified statically, the applied force shall otherwise be known to 62.5 %. Careful alignment of the specimen and fixturing is necessary to encourage straight fatigue cracks. The fixturing shall be such that the stress distribution is uniform across the specimen thickness and symmetrical about the plane of the prospective crack. 6.3 Loading Fixtures—Fixtures suitable for loading the specified specimen configurations are shown in the Annexes. The fixtures are designed to minimize friction contributions to the measured force. 6.4 Displacement Gage—The displacement gage electrical output represents relative displacement (V) of two precisely located gage positions spanning the crack starter notch mouth. Exact and positive positioning of the gage on the specimen is essential, yet the gage must be released without damage when the specimen breaks. Displacement gage and knife-edge designs shall provide for free rotation of the points of contact between the gage and the specimen. A recommended design for a self-supporting, releasable displacement gage is shown in FIG. 2 Double–Cantilever Clip-In Displacement Gage Showing Mounting by Means of Integral Knife Edges (Gage Design Details are Given in Annex A1) Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 5 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 Fig. 2 and described in Annex A1. The gage’s strain gage bridge arrangement is also shown in Fig. 2. 6.4.1 The specimen shall be provided with a pair of accurately machined knife edges to support the gage arms and serve as displacement reference points. The knife edges may be machined integral with the specimen as shown in Figs. 2 and 3, or they may be separate pieces affixed to the specimen. A suggested design for attachable knife edges is shown in Fig. 4. This design features a knife edge spacing of 5 mm (0.2 in.). The effective gage length is established by the points of contact between the screw and the hole threads. For the design shown, the major diameter of the screw is used in setting this gage length. A No. 2 screw will permit the use of attachable knife edges for specimens having W > 25 mm (1.0 in.). 6.4.2 Each gage shall be verified for linearity using an extensometer calibrator or other suitable device. The resolution of the calibrator at each displacement interval shall be within 0.00051 mm (0.000020 in.). Readings shall be taken at ten equally spaced intervals over the working range of the gage (see Annex A1). The verification procedure shall be performed three times, removing and reinstalling the gage in the calibration fixture after each run. The required linearity shall correspond to a maximum deviation of 0.003 mm (0.0001 in.) of the individual displacement readings from a least-squares-best-fit straight line through the data. The absolute accuracy, as such, is not important in this application, since the test method is concerned with relative changes in displacement rather than absolute values (see 9.1). Verification of gage calibration shall be performed at the temperature of test 65.6°C (10°F). The gage shall be verified during the time the gage is in use at time intervals defined by established quality assurance practices. Commercial gages are typically verified annually. 6.4.3 It is not the intent of this test method to exclude the use of other types of gages or gage-fixing devices provided the NOTE 1—Dimensions in mm. NOTE 2— Gage length shown corresponds to clip gage spacer block dimensions shown in Annex A1, but other gage lengths may be used provided they are appropriate to the specimen (see 6.4.3). NOTE 3—For starter notch configurations see Fig. 5. NOTE 1—Dimensions are in mm. NOTE 2—Effective gage length = 2C + Screw Thread Diameter # W/2. (This will always be greater than the gage length specified in A1.1.) NOTE 3—Dimension shown corresponds to clip gage spacer block dimension in Annex A1. Inch-Pound Units Equvalients mm in. 0.81 0.032 1.3 0.050 1.5 0.060 5.08 0.200 FIG. 3 Example of Integral Knife Edge Design 6.35 0.250 1.8 0.070 2.54 0.100 3.18 0.125 FIG. 4 Example of Attachable Knife Edge Design gage used meets the requirements listed above and provided the gage length does not exceed those limits given in the Annex appropriate to the specimen being tested. 7. Specimen Size, Configurations, and Preparation 7.1 Specimen Size: 7.1.1 In order for a result to be considered valid according to this test method (see also 3.1.2.1), the specimen ligament size (W – a) must be not less than 2.5(KIc/sYS)2, where sYS is the 0.2 % offset yield strength of the material in the environment and orientation, and at the temperature and loading rate of the test (1, 4, 5). For testing at rates other than quasi-static see Annex A10, Rapid Force Testing. The specimen must also be of sufficient thickness, B, to satisfy the specimen proportions in 7.2.1 or 7.2.1.1 and meet the Pmax/PQ requirement in 9.1.3. Meeting the ligament size and Pmax/PQ requirements cannot be assured in advance. Thus, specimen dimensions shall be conservatively selected for the first test in a series. If the form of the material available is such that it is not possible to obtain a test specimen with ligament size equal to or greater than 2.5(KIc/sYS)2, then it is not possible to make a valid KIc measurement according to this test method. 7.1.2 The initial selection of specimen size for a valid KIc measurement is often based on an estimated value of KIc for the material. 7.1.3 Alternatively, the ratio of yield strength to elastic modulus may be used for selecting a specimen size that will be adequate for all but the toughest materials: sYS/E Inch-Pound Units Equivalents mm in. 1.5 0.060 0.0050 to 0.0057 0.0057 to 0.0062 0.0062 to 0.0065 Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 6 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. Minimum Recommended Ligament Size mm in. 76 64 51 3 21⁄2 2 E399 – 09´2 0.0065 to 0.0068 0.0068 to 0.0071 0.0071 to 0.0075 0.0075 to 0.0080 0.0080 to 0.0085 0.0085 to 0.0100 0.0100 or greater 44 38 32 25 19 13 6.4 13⁄4 11⁄2 11⁄4 1 3⁄ 4 1⁄ 2 1⁄ 4 When it has been established that 2.5(KIc/sYS)2 is substantially less than the minimum recommended ligament size given in the preceding table, then a correspondingly smaller specimen can be used. 7.2 Specimen Configurations—Recommended specimen configurations are shown in Figs. A3.1-A6.1 and Fig. A7.1. 7.2.1 Specimen Proportions—Crack size, a, is nominally between 0.45 and 0.55 times the width, W. Bend specimens can have a width to thickness, W/B, ratio of 1 # W/B # 4. Tension specimen configurations can be 2 # W/B # 4. 7.2.1.1 Recommended Proportions—It is recommended that the thickness, B, is nominally one-half the specimen width, W (that is, W/B = 2). Likewise, the crack size, a, should be nominally equal to one-half the width, W (that is a/W = 1/2). NOTE 3—Alternative W/B ratios different from the recommended ratio in 7.2.1.1 but still meeting the requirements in 7.2.1 are sometimes useful, especially for quality control or lot releases purposes, because they allow a continuous range of product thicknesses to be tested using a discrete number of specimen widths while still maintaining specimens of full product thickness. However, because specimen width influences the amount of crack extension corresponding to the 95 % slope, KIc obtained with alternative W/B ratios may not agree with those obtained using the recommended W/B ratio, particularly in products exhibiting a Type I force-CMOD record (6). As an example, a specimen with the recommended proportion W/B = 2 would tend to yield a lower KIc than a specimen with an alternative proportion W/B = 4. Also, because a shorter ligament length may hinder resistance curve development, an alternative specimen with W/B < 2 (allowed only for bend specimens) may pass the Pmax/PQ requirement, while a specimen with the recommended W/B ratio would fail. Conversely, an alternative specimen with W/B >2 (allowed in both tension and bend specimens) may fail the Pmax/PQ requirement, while a specimen with the recommended W/B would pass. 7.2.2 Alternative Specimens—In certain cases it may be necessary or desirable to use specimens having W/B ratios other than that specified in 7.2.1. Alternative W/B ratios and side-grooved specimens are allowed as specified in 7.2.1.1 and 7.2.2.1. These alternative specimens shall have the same crack length-to-specimen width ratio as the standard specimen. (a) Starter Notches and Fatigue Cracks Note 1—For a chevron crack starter notch the fatigue crack shall emerge on both surfaces of the specimen. Note 2—Fatigue crack extension on each surface of the specimen containing a straight-through notch shall be at least 0.025 W or 1.3 mm (0.050 in.), whichever is larger. Note 3—Fatigue crack extension on each surface of the specimen from the stress raiser tipping the hole shall be at least 0.5 D or 1.3 mm (0.050 in.), whichever is larger. Note 4—Crack starter notch shall be perpendicular to the specimen surfaces and to the intended direction of crack propagation within 62°. Note 5—Notch width N need not be less than 1.6 mm (1⁄16 in.). Note 6—From notched edge or centerline of loading holes, as appropriate. (b) Detail of Chevron Notch Note 1—A = C within 0.010 W. Note 2—Cutter tip angle 90° max. Note 3—Radius at chevron notch bottom 0.25 mm (0.010 in.) max. FIG. 5 Crack Starter Notch and Fatigue Crack Configurations Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 7 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 7.2.2.1 Alternative Side-Grooved Specimens—For the compact C(T) and the bend SE(B) specimen configurations sidegrooving is allowed as an alternative to plain-sided specimens. The total thickness reduction shall not exceed 0.25 B. A total reduction of 0.20 B has been found to work well (7) for many materials and is recommended (10% per side). Any included angle less than 90° is allowed. The root radius shall be 0.5 6 0.2 mm (0.02 6 0.01 in.). Precracking prior to the sidegrooving operation is recommended to produce nearly straight fatigue precrack fronts. BN is the minimum thickness measured at the roots of the side grooves. The root of the side groove shall be located along the specimen centerline. Fig. 6 is a schematic showing an example cross section of an alternative side grooved specimen. NOTE 4— Side-grooves increase the level of constraint with respect to the recommended specimen. The increased constraint promotes a more uniform stress state along the crack front and inhibits shear lip development. As a result, the KIcvalue from a side-grooved specimen is expected to be lower than the KIc obtained from the recommended specimen, particularly for thin products or products exhibiting Type I behavior. The value of KIc from a side-grooved specimen may better represent the fracture toughness of the material in structural situations where plasticity is more highly constrained by the crack front geometry such as may be the case for a surface or corner crack, or by structural details such as keyways, radii, notches, etc. The value of KIc from the recommended specimen may better represent the fracture toughness of the material in structural situations where surface plasticity and shear lip development is not constrained such as a through crack in a region of uniform thickness. Side-grooving increases the likelihood of meeting the Pmax/PQ requirement, enabling a valid KIc to be obtained in products for which it would not be possible using the recommended specimen. Side grooving after precracking beneficially removes a portion of the non-linear crack front at the ends of the crack front, thus increasing the likelihood of meeting crack front straightness requirements. However, side grooving may also remove material that influences service performance. This is often true for cast parts and those for which thermo-mechanical working is part of the heat treating cycle. The increased constraint also can lead to increased likelihood of material delamination, for instance, in the plane of the specimen, which could lead to test results different from those obtained from plane-sided specimens. NOTE 5—No interlaboratory ‘round robin’ test program has yet been conducted to compare the performance of plain-sided and side-grooved specimens. However, the results of several studies (7) indicate that KIc from side-grooved specimens is zero to 10 % less than that of plain-sided specimens, the difference increasing with increasing material toughness. The within-laboratory repeatability was determined according to the conditions in Terminology E456 and the results are presented in 11.3. 7.2.2.2 For lot acceptance testing, side-grooved specimens shall not be used unless specifically allowed by the product specification or by agreement between producer and user. 7.3 Specimen Preparation—All specimens shall be tested in the finally heat-treated, mechanically-worked, and environmentally-conditioned state. Specimens shall normally be machined in this final state. However, for material that cannot be machined in the final condition, the final treatment may be carried out after machining provided that the required dimensions and tolerances on specimen size, shape, and overall finish are met (see specimen drawings of Figs. A3.1-A6.1 and Fig. A7.1), and that full account is taken of the effects of specimen size on metallurgical condition induced by certain heat treatment procedures; for example, water quenching of steels. 7.3.1 Fatigue Crack Starter Notch—Three fatigue crack starter notch configurations are shown in Fig. 5. To facilitate fatigue precracking at low stress intensity levels, the suggested root radius for a straight-through slot terminating in a V-notch is 0.08 mm (0.003 in.) or less. For the chevron form of notch, the suggested root radius is 0.25 mm (0.010 in.) or less. For the slot ending in a drilled hole, it is necessary to provide a sharp stress raiser at the end of the hole. Care shall be taken to ensure that this stress raiser is so located that the crack plane orientation requirements of 8.2.4 can be met. 7.3.2 Fatigue Precracking—Fatigue precracking procedures are described in Annex A8. Fatigue cycling is continued until a crack is produced that satisfies the requirements of 7.3.2.1 and 7.3.2.2 that follow. 7.3.2.1 Crack size (total size of crack starter plus fatigue crack) shall be between 0.45W and 0.55W. 7.3.2.2 The size of the fatigue crack on each face of the specimen shall not be less than the larger of 0.025W or 1.3 mm (0.050 in.) for the straight-through crack starter configuration, not less than the larger of 0.5D or 1.3 mm (0.050 in.) for the slot ending in a hole (of diameter D < W/10), and need only emerge from the chevron starter configuration. 8. General Procedure 8.1 Number of Tests—It is recommended that triplicate tests, minimum, be made for each material condition. 8.2 Specimen Measurement—Specimen dimensions shall conform to the drawings of Figs. A3.1-A6.1 and Fig. A7.1. Measurements essential to the calculation of KIc are specimen FIG. 6 Schematic of Side Groove Configration Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 8 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 thickness, B (and in the case of side-grooved alternative specimens, BN), crack size, a, and width, W. 8.2.1 Specimen thickness, B (and in the case of sidegrooved alternative specimens, BN), shall be measured before testing to the nearest 0.03 mm (0.001 in.) or to 0.1 %, whichever is larger. For plain-sided specimens, B shall be measured adjacent the notch. For side-grooved specimens, BN shall be measured at the root of the notch and B adjacent the notch. NOTE 6—For plane-sided specimens the value of BN is equal to the thickness B. 8.2.2 Specimen width, W, shall be measured, in conformance with the procedure of the annex appropriate to the specimen configuration, to the nearest 0.03 mm (0.001 in.) or 0.1 %, whichever is larger, at not less than three positions near the notch location, and the average value recorded. 8.2.3 Specimen crack size, a, shall be measured after fracture to the nearest 0.5 % at mid-thickness and the two quarter-thickness points (based on B for plain-sided specimens and BN for side-grooved specimens). The average of these three measurements shall be taken as the crack size, a. The difference between any two of the three crack size measurements shall not exceed 10 % of the average. The crack size shall be measured also at each surface. For the straight-through notch starter configuration, no part of the crack front shall be closer to the machined starter notch than 0.025W or 1.3 mm (0.050 in.), whichever is larger; furthermore, neither surface crack size measurement shall differ from the average crack size by more than 15 % and their difference shall not exceed 10 % of the average crack size. For the chevron notch starter configuration, the fatigue crack shall emerge from the chevron on both surfaces; furthermore, neither surface crack size measurement shall differ from the average crack size by more than 15 %, and their difference shall not exceed 10 % of the average crack size. 8.2.4 The plane of the fatigue precrack and subsequent 2 % crack extension (in the central flat fracture area; that is, excluding surface shear lips) shall be parallel to the plane of the starter notch to 610°. For side-grooved specimens, the plane of the fatigue precrack and subsequent 2% crack extension shall be within the root of the side-groove. 8.2.5 There shall be no evidence of multiple cracking (that is, more than one crack) (8). 8.3 Loading Rate—For conventional (quasi-static) tests, the specimen shall be loaded such that the rate of increase of stress-intensity factor is between 0.55 and 2.75 MPa=m/s (30 and 150 ksi=in./min) during the initial elastic displacement. Loading rates corresponding to these stress-intensity factor rates are given in the Annex appropriate to the specimen being tested. For rapid-force tests, loading rates are to be as specified in Annex A10. 8.4 Test Record—A record shall be made of the output of the force-sensing transducer versus the output of the displacement gage. The data acquisition system shall be set such that not less than 50 % of full range is used for the test record. If an autographic recorder is used, it shall be adjusted such that the slope of the initial portion of the force-CMOD record is between 0.7 and 1.5. Alternatively, if a computer data acqui- sition system is used, it shall be programmed to capture enough data to permit the calculations of Section 9. 8.4.1 The test shall be continued until the specimen can sustain no further increase in applied force. The maximum force (Pmax) shall be noted and recorded. 9. Calculation and Interpretation of Results 9.1 Interpretation of Test Record and Calculation of KIc—In order to substantiate the validity of a KIc determination, it is first necessary to calculate a conditional result, KQ, which involves a construction on the test record, and then to determine whether this result is consistent with the size and yield strength of the specimen according to 7.1. The procedure is as follows: 9.1.1 When an autographic recorder is used, the conditional value PQ is determined by drawing the secant line OP5, (see Fig. 7) through the origin (point O) of the test record with slope (P/V)5 equal to 0.95(P/V)o, where (P/V)o is the slope of the tangent OA to the initial linear portion of the record (Note 7). The force PQ is then defined as follows: if the force at every point on the record which precedes P5 is lower than P5 (Fig. 7, Type I), then P5 is PQ; if, however, there is a maximum force preceding P5 which exceeds it (Fig. 7, Types II and III), then this maximum force is PQ. NOTE 7—Slight initial nonlinearity of the test record is frequently observed, and is to be ignored. However, it is important to establish the initial slope of the record with high precision. Therefore it is advisable to minimize this nonlinearity by preliminarily loading the specimen to a maximum force corresponding to a stress-intensity factor level not exceeding that used in the final stage of fatigue cracking, then unloading. NOTE 8—Residual stresses can adversely affect the indicated KQ and KIc values. The applied loading is superimposed on the residual stresses, resulting in a total crack tip stress-intensity different from that based solely on the externally applied forces. In addition, residual stresses will likely redistribute during machining when the specimen is extracted from the host material. Hence, the magnitude of their influence on KQ and KIc in the test specimen may be quite different from that in the original or finish machined product (see also 5.1.6.) 9.1.2 When a computer data acquisition system is used, the data reduction program shall determine the same forces (PQ and Pmax) as above. The algorithms for doing this are discretionary. 9.1.3 The ratio Pmax/PQ, where Pmax is the maximum force the specimen was able to sustain (see 8.4.1), shall be calculated. If this ratio does not exceed 1.10, proceed to calculate KQ as described in the Annex appropriate to the specimen configuration. If Pmax/PQ does exceed 1.10, then the test is not a valid KIc test and the user is referred to Test Method E1820 on elastic-plastic fracture toughness. 9.1.4 The value 2.5(KQ/sYS)2, where sYS is the 0.2 % offset yield strength in tension (see Test Methods E8/E8M), shall be calculated. If this quantity is less than the specimen ligament size, W–a then KQ is equal to KIc. Otherwise, the test is not a valid KIc test. Expressions for calculating KQ are given in the Annexes for each specified specimen configuration. 9.1.5 If the test result fails to meet the requirements of 9.1.3 or 9.1.4, or both, it will be necessary to use a larger specimen to determine KIc. Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 9 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 FIG. 7 Principal Types of Force-Displacement (CMOD) Records 10. Report 10.1 The specimen configuration code shown on the specimen drawing (in the appropriate Annex) shall be reported. This code shall be followed with the loading code (T for tension, B for bending) and the code for crack plane orientation (see 3.1.3). The latter two codes shall appear in separate parentheses. As an example, a test result obtained using the compact specimen (see Annex A4) might be designated as follows: C(T)(S-T). The first letter (C) indicates the specimen to be a compact configuration. The second letter (T) denotes the loading as tension. The first of the two letters in the last bracket (S) indicates the normal to the crack plane to be normal to the direction of principal deformation. The second of these letters (T) indicates the intended direction of crack extension to be parallel with the direction of least deformation. For cylindrical sections, where grain flow can be in the longitudinal, radial or circumferential direction, the direction of maximum grain flow shall be reported when the direction is known (see 3.1.3). 10.2 The following information shall be additionally reported for each specimen tested: 10.2.1 Characterization of the material (alloy code or chemistry and metallurgical condition) and product form (sheet, plate, bar, forging, casting, and so forth) tested. 10.2.2 Specimen thickness, B, for plain-sided configurations. For side-grooved specimens, B, BN and (B· BN)1/2. 10.2.3 Specimen width (depth), W. 10.2.3.1 Loading hole offset, X, for the arc-shaped tension specimen. 10.2.3.2 Outer and inner radii, r2 and r1, for arc-shaped specimens. 10.2.4 Fatigue precracking conditions, specifically the maximum stress-intensity factor, Kmax, stress-intensity factor range, DKI, and number of cycles for the final 2.5 % of the overall crack size, a (size of notch plus fatigue crack extension). 10.2.5 Crack size measurements, after fracture, at midthickness and the two quarter-thickness positions on the crack front, as well as at the intersection of the crack front with the specimen surface. 10.2.6 Test temperature. 10.2.7 Relative humidity as determined by Test Method E337. · 10.2.8 Loading rate in terms of KI (change in stressintensity factor per unit time) (3). 10.2.9 Force-versus-crack mouth opening displacement (CMOD) record and associated calculations. 10.2.10 Yield strength as determined by Test Methods E8/E8M. 10.2.11 KIc (or, KQ followed by the parenthetical statement “invalid according to Sections(s) _____ of Test Method E399”). 10.2.12 Pmax/PQ. 10.3 Fig. 8 is a convenient format for tabulating the information required in 10.1 and 10.2. 11. Precision and Bias 11.1 The precision of KIc measurements has been examined in several interlaboratory round-robin studies. Selected aluminum alloys and high-strength steels were tested using standard bend SE(B) (9), compact C(T) (10), and arc-shaped tension A(T) (11) specimen configurations. The results are summarized in 11.3 (Precision) and 11.5 (Bias) that follow. Not all of the results reported satisfied all of the validity requirements of this test method. Statistical analysis (10, 11, 12) was used to Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 10 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 FIG. 8 Suggested Form of Table for Reporting Information Listed in 10.1 and 10.2 exclude data that were likely influenced by deviations from the validity requirements. No round-robin program has been conducted for the disk-shaped compact DC(T) specimen configuration, but limited data for that specimen configuration are compared with data for other specimen configurations in Annex A5. Round-robin studies specific to the quasi-static testing of beryllium and the dynamic testing of a strain-rate sensitive steel, and which involved special testing procedures, are presented in Annex A9 and Annex A10. 11.2 It should be emphasized that the measures of precision given in Table 1, Table 2, and Table 3 apply to alloys that essentially exhibited no transitional fracture behavior with temperature or strain rate under the specific test conditions of the interlaboratory studies. 11.3 Precision—The precision of KIc determination is affected by errors in the measurement of test force and specimen dimensions, especially the crack size. This test method specifies a precision for each measured quantity and, based on these specifications and the round-robin results, a theoretical precision is rendered (13). Analysis of the method’s specifications suggests that precision decreases with increasing relative crack size, more for the bend than for the compact configuration. In practice, the precision of KIc measurement may depend to an unknown extent on the characteristics of the test record and TABLE 1 Precision Using SE(B) Specimens (Nominal Crack Size-to-Specimen Width Ratio a/W =0.5) Parameter KIc (MPa=m) Material and Yield Strength Average Repeatability Standard Deviation Reproducibility Standard Deviation Repeatability Limit Reproducibility Limit 2219–T851 (353 MPa) Maraging 18Ni (1903 MPa) 4340–500 F (1641 MPa) 4340–800 F (1420 MPa) 35.94 2.27 2.54 6.37 7.11 57.02 2.15 4.03 6.03 11.27 48.55 1.86 2.17 5.20 6.07 87.76 3.03 4.13 8.49 11.56 Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 11 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 TABLE 2 Precision Using C(T) Specimens (Nominal Crack Size-to-Specimen Width Ratio a/W = 0.5) Parameter KIc (MPa=m) Material and Yield Strength Average Repeatability Standard Deviation Reproducibility Standard Deviation Repeatability Limit Reproducibility Limit 2219–T851 (353 MPa) Maraging 18Ni (1903 MPa) 4340–500 F (1641 MPa) 4340–800 F (1420 MPa) 35.61 1.91 2.17 5.36 6.07 59.06 2.14 2.65 5.98 7.41 50.38 2.12 2.87 5.95 8.04 87.83 2.21 3.14 6.19 8.80 TABLE 3 Precision Precision for A(T) Specimens (Nominal Crack Size-to-Specimen Width Ratio a/W = 0.5) Parameter Specimen Type Average Repeatability Standard Deviation Reproducibility Standard Deviation Repeatability Limit Reproducibility Limit KIc (MPa=m) X/W = 0 X/W = 0.05 102.3 101.6 4.69 2.33 7.16 4.81 13.13 6.53 20.05 13.47 analysis skills of the laboratory personnel. It is possible to derive useful information concerning the precision of KIc measurement from three round-robin programs (10, 11, 12) as described below. Results for bend, compact, and arc-shaped specimen configurations were obtained for several aluminum alloys and high strength steels. The materials were chosen for their reproducible, uniform composition and microstructure. Thereby the contribution of material variability to the measurement of KIc was minimized. 11.3.1 An interlaboratory study (9) for the measurement of plane strain fracture toughness, KIc on metallic materials, using SE(B) specimens, was conducted among nine laboratories using four metallic materials (one aluminum alloy and three high-strength steels). 180 specimens were tested (5 per laboratory and material). Analyses were undertaken in accordance with Practice E691, see ASTM Research Report No. E0810045 and Table 1. 11.3.2 A second interlaboratory study (10) for the measurement of plane strain fracture toughness, KIc on metallic materials, using C(T) specimens, was conducted among nine laboratories using the same four metallic materials (one aluminum alloy and three high-strength steels). 216 specimens were tested (6 per laboratory and material). Analyses were undertaken in accordance with Practice E691, see ASTM Research Report No. E08-10056 and Table 2. 11.3.3 A third interlaboratory study (11) for the measurement of plane strain fracture toughness, KIc, using arc-shaped A(T) specimens, with two different loading hole configurations (X/W = 0 and X/W = 0.5), was conducted among eight laboratories using one high strength steel (Ni-Cr-Mo-V vacuum-degassed steel, yield strength sYS= 1324 MPa). 48 5 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report: RR:E08-1004. 6 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report: RR:E08-1005. specimens were tested (from 3 to 5 per laboratory). Analyses were undertaken in accordance with Practice E691, see ASTM Research Report No.E08-10067 and Table 3. 11.3.4 The terms repeatability limit and reproducibility limit are used as specified in Practice E177. 11.3.5 The results presented in Table 1, Table 2, and Table 3 shall not be transferred to materials or KIc levels other than those relevant to the specific interlaboratory studies (9, 10, 11). 11.4 Alternative side-grooved specimens were tested to determine within-laboratory limit and repeatability according to the conditions in Terminology E456. The testing was performed on aluminum alloy 7055–T7951 using C(T) specimens having a nominal dimensions W=50.8 (2.0 in), B =25.4 mm (1.0 in.) BN= 20.3 mm (0.80 in.) notch root angle = 45° and notch root radius = 0.5mm (0.02 in.). The results are given in Table 4 along with results obtained from plain-sided specimens from manufactured the same lot of material, tested at the same time, and under the same test conditions The repeatability standard deviation for this test series 0.22 MP=m (0.20 ksi=in.) for side-grooved specimens and 0.33 MPa=m (0.30 ksi=in.) for the plane-sided specimens. 11.5 Bias—There is no accepted standard value for the plane-strain fracture toughness of any material. In the absence of such a true value, any statement concerning bias is not meaningful. 7 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report: RR:E08-1006. TABLE 4 Repeatability Results for Side-Grooved and PlaneSided C(T) Specimens 7055–T7951 Parameter Specimen Type No. of Average Repeatability Repeatability Specimens Standard Limit Deviation Side-Grooved 11 KIc (MPa=m) Plane-Sided 11 Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 12 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. 26.9 27.9 0.22 0.33 0.49 0.74 E399 – 09´2 ANNEXES (Mandatory Information) A1. DOUBLE-CANTILEVER DISPLACEMENT GAGE A1.1 The displacement gage consists of two cantilever beams and a spacer block clamped together with a single bolt and nut (Fig. 2). Electrical-resistance strain gages are adhesively bonded to the tension and compression surfaces of each beam, and are connected as a Wheatstone bridge incorporating a suitable balancing resistor. The beams are made of material with a high ratio of yield strength-to-elastic modulus. One such material is solution treated Ti-13V-11Cr-3Al titanium alloy. For material of different modulus, the spring constant of the assembly is correspondingly different, but other characteristics are unaffected. Detailed dimensions for the beams and spacer block are given in Figs. A1.1 and A1.2. Those particular values provide a linear (working) range from 3.8 to 7.6 mm (0.15 to 0.30 in.) and a gage length of 5.1 to 6.4 mm (0.20 to 0.25 in.). The gage length can be adjusted by substituting a differently sized spacer block. The gage’s required precision is stated as a maximum deviation of 60.003 mm (0.0001 in.) from a least-squares-best-fit straight line through its displacement calibration data (see 6.4.2). Additional details concerning design, construction and use of the gage are given in (14). NOTE—Dimensions are in mm. Inch-Pound Units Equivalents mm in. mm in. 0.10 0.15 0.25 0.48 0.51 0.53 0.64 0.76 0.99 1.04 0.004 0.006 0.010 0.019 0.020 0.021 0.025 0.030 0.039 0.041 1.52 1.65 3.6 4.72 4.78 9.40 9.47 9.52 41.15 41.28 0.060 0.065 9⁄64 0.186 0.188 0.370 0.373 0.375 1.620 1.625 FIG. A1.1 Beams for Double-Cantilever Displacement Gage Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 13 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 NOTE 1—2-mm diameter holes are for strain gage leads. NOTE 2—Dimensions are in mm. Inch-Pound Units Equivalents mm in. mm in. 0.80 1.14 1.27 2.00 2.21 2.36 3.18 3.60 4.72 4.78 4.83 ⁄ 0.045 0.050 5⁄64 0.087 0.093 0.125 9⁄64 0.186 0.188 0.190 4.95 5.21 9.47 9.52 9.55 9.60 10.16 10.21 12.45 12.70 12.70 0.195 0.205 0.373 0.375 0.376 0.378 0.400 0.402 0.490 1 ⁄2 0.500 1 32 FIG. A1.2 Aluminum-Alloy Spacer Block for Double-Cantilever Displacement Gage A2. TESTING FIXTURES A2.1 Bend Specimen Loading Fixture A2.1.1 The bend test is performed using fixtures designed to minimize friction effects by allowing the support rollers to rotate and translate slightly as the specimen is loaded, thereby achieving rolling contact. A design suitable for testing standard bend (SE(B)) and arc-shaped bend (A(B)) specimens is shown in Fig. A2.1. While free to roll and translate during test, the rollers are initially positioned against stops that set the span length and are held in place by low-tension springs (such as rubber bands). A2.1.2 The bend fixture is aligned such that the line of action of the applied force passes midway between the support rollers to 61.0 % of the span, S, and is perpendicular to the roller axes to 62° (15). The span is to be measured to 60.5 %. A2.2 Compact Specimen Loading Clevis A2.2.1 A loading clevis suitable for testing standard compact (C(T)), arc-shaped tension (A(T)), and disk-shaped compact (DC(T) specimens is shown in Fig. A2.2. Both ends of the specimen are held in the clevis and loaded through pins in order to allow rotation of the specimen during testing. The clevis holes are provided with small flats on the loading surfaces to provide rolling contact, thereby minimizing friction effects (16). A2.2.2 The size, proportions, and tolerances for the clevis shown in Fig. A2.2 are all scaled to specimens with W/B = 2 for B $ 13 mm (0.5 in.), and W/B = 4 for B # 13 mm (0.5 in.). Clevis and pins made from 1930 MPa (280 ksi) yield strength maraging steel are suitable for testing specimens of the sizes Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 14 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 and sys/E ratios of 7.1.3. For lower-strength clevis material or substantially larger specimens at a given sys/E ratio, larger clevises are required. As indicated in Fig. A2.2, the clevis corners may be trimmed sufficiently to accommodate seating of the displacement gage in specimens less than 9.53 mm (0.375 in.) thick. A2.2.3 To minimize eccentricity in the load train, the loading rods shall be aligned to 60.8 mm (0.03 in.) and the specimen centered in the clevis slot to 60.8 mm (0.03 in.). NOTE 1—Dimensions in mm, except surface finishes in µm. NOTE 2—Support rollers and specimen contact surface of loading ram shall be parallel to each other within 0.002 W. NOTE 3—2.54 mm = 0.100 in., 3.81 mm = 0.150 in, 1.6 µ-m = 63 µ-in. FIG. A2.1 Loading Fixture for Standard SE(B) (shown) and Arc-Shaped A(B) (not shown) Bend Specimens Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 15 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 NOTE 1—Surface finishes in µm. NOTE 2—Pin diameter = 0.24 W (+0.000 W/–0.005 W). For specimens with sys > 1379 ksi (200 ksi), the holes in the specimen and in the clevis may be 0.30 W (+0.005 W/–0.000 W) and the pin diameter 0.288 W (+0.000W/–0.005 W). NOTE 3—Corners of the clevis may be removed if necessary to accommodate the clip gage. NOTE 4—1.6 µm = 63 µin., 3.2 µm = 125 µin. NOTE 5—Accumulated experience indicates that subtle deviation from the recommended configuration can lead to complications. For instance, undersized loading pins can lead to inelastic load transfer from clevis to specimen. Poorly machined flats can also cause difficulties. FIG. A2.2 Loading Clevis for Compact C(T), Arc-Shaped A(T) and Disk-Shaped DC(T) Tension Specimens A3. SPECIAL REQUIREMENTS FOR TESTING BEND SPECIMENS A3.1 Specimen A3.1.1 The standard bend specimen configuration is a single- edge-notched and fatigue precracked beam loaded in three-point bending. The support span, S, is nominally equal to four times the specimen width, W. The general proportions of the standard configuration are shown in Fig. A3.1. A3.1.2 Alternative configurations may have 1 # W/B # 4; however, these specimens shall also have a nominal support span equal to 4W. A3.2 Specimen Preparation A3.2.1 Generally applicable specifications regarding specimen size, configuration and preparation are given in Section 7. A3.2.2 In the interest of K-calibration accuracy, it is desirable to fatigue precrack bend specimens using the same loading fixture to be used in subsequent testing. A3.2.3 Bend specimens are occasionally precracked in cantilever bending, especially for reversed force cycling (see A9.2.3.2). If the three-point bending K-calibration is used for cantilever bending, the cantilever bending moment for a given K value will be underestimated (8). The crack tip stress field in cantilever bending can be distorted by excessive clamping forces, thereby affecting fatigue crack planarity. A3.3 Apparatus A3.3.1 Bend Test Fixture—The loading fixture for bend testing is illustrated in Fig. A2.1 and discussed in A2.1. The fixture is designed to minimize friction effects by allowing the rollers to rotate and translate slightly as the specimen is loaded, thus providing rolling contact. A3.3.2 Displacement Gage—Details regarding displacement gage design, calibration, and use are given in 6.4. For the Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 16 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 bend specimen, displacements are essentially independent of gage length up to W/2. W a A3.4 Procedure A3.4.1 Measurement—Specimen width (depth), W, is measured from the notched edge of the specimen to the opposite edge. Crack size a, is measured from the notched edge to the crack front. A3.4.1.1 General requirements concerning specimen measurement are given in 8.2. A3.4.2 Bend Specimen Testing—General principles concerning the loading fixture and its setup appear in A2.1. A3.4.2.1 Locate the specimen with the crack tip midway between the rolls to within 1 % of the span, and square to the roll axes within 2°. The displacement gage is seated on the knife edges such as to maintain registry between knife edges and gage grooves. In the case of attachable knife edges, the gage is seated before the knife edge positioning screws are tightened. A3.4.2.2 The specified rate of increase of the stressintensity factor (see 8.3) ranges from 0.55 and 2.75 MPa=m/s (30 and 150 ksi=in./min) and corresponds to a loading rate for a standard (W/B = 2) 25.4 mm (1 in.) thick specimen between 0.30 to 1.5 kN/s (4.0 and 20 klbf/min). A3.4.2.3 Details concerning recording of the test record are given in 8.4. A3.5 Calculations A3.5.1 Interpretation of Test Record—General requirements and procedures for interpreting the test record are given in 9.1. A3.5.2 Validity Requirements—Validity requirements in terms of limitation on Pmax/PQ and mandatory specimen size are given in 9.1.3 through 9.1.4. A3.5.3 Calculation of KQ—Bend specimen KQ is calculated in SI or inch-pound units of Pa=m (psi=in.) as follows (see Note A3.2): KQ 5 = specimen width (depth) as determined in A3.4.1, m (in.), and = crack size as determined in 8.2.3, m (in.). NOTE A3.1—Example: for a/W = 0.500, ƒ(a/W) = 2.66. NOTE A3.2—This expression for a/W is considered to be accurate within 1 % over the range 0.2 # a/W # 1 for S/W = 4 (17). A3.5.4 Calculation of Crack Mouth Opening Compliance Using Crack Size Measurements—Bend specimen crack mouth opening compliance, Vm/P, is calculated in units of m/N (in./lb) as follows (see Note A3.4): SD Vm a S P 5 E’ BeW · q W where: S DF a 6 W S DS DF S DS 2 SD a 2 2.04 W 3 S a 1 0.66/ 1 2 W DG 2 NOTE A3.3—Example: for a/W = 0.500, q(a/W) = 8.92. NOTE A3.4—This expression is considered to be accurate within 1.0 % over the entire range 0 # a/W # 1 for S/W = 4 (19). It is valid only for crack mouth opening displacement measured at the location of the integral knife edges shown in Fig. 3. Attachable knife edges must be reversed or inset to effect the same measurement points. A3.5.5 Calculation of Crack Size Using Crack Mouth Opening Compliance Measurements—Bend specimen normalized crack size is calculated as follows (see Note A3.5): a W5 (A3.5) 1.00023.950 · U12.982 · U223.214 · U3151.516 · U42113.031 · U5 (A3.1) U5 11 SD Œ for PQ B BN a a 0.76 2 2.28W 1 3.87 W (A3.4) for which: E’ = elastic constraint modulus (E for plane stress; E/(1 − n2) for plane strain), Pa (psi), n = Poisson’s Ratio, Be = B – (B– BN)2/B, and S, B, BN, W, and a are defined in A3.5.3. where: a ƒ W 53 SD SD a q W 5 where: SD a PQS ·ƒ W =BBN W3/2 a a 1.99 2 W W· (A3.3) S DG a 2 a 2.15 2 3.93 W 1 2.7 W a a 3/2 2 1 1 2w 12W (A3.2) a 12W D which: = force as determined in 9.1.1, N (lbf), = specimen thickness as determined in 8.2.1, m (in.), = specimen thickness between the roots of the side grooves, as determined in 8.2.1, m (in.), S = span as determined in A3.4.2 (see also A2.1), m (in.), ŒS 1 E’ BeVm P DS D 4W S (A3.6) for which: Vm = crack mouth opening displacement, m (in.), P = applied force, N (lbf), and Be = B – (B– BN)2/B, and E’ is defined in A3.5.4 and S, B, BN, W and a are defined in A3.5.3. NOTE A3.5—This expression fits the equation in A3.5.4 within 0.05 % of W in the range 0.3 # a/W # 0.9 for S/W = 4 (20). It is valid only for crack mouth opening displacement measured at the location of the integral knife edges shown in Fig. 3. Attachable knife edges must be reversed or inset to effect the same measurement points. Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 17 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 NOTE NOTE NOTE NOTE NOTE NOTE 1—Surface finishes in µm. 2—A surfaces shall be perpendicular and parallel as applicable within 0.001 W TIR. 3—Crack starter notch shall be perpendicular to specimen surfaces within 2°. 4—Integral or attachable knife edges for clip gage attachment may be used (see Figs. 3 and 4) 5—For starter notch and fatigue crack configuration see Fig. 5. 6—1.6 µm = 63 µin., 3.2 µm = 125 µin. FIG. A3.1 Bend SE(B) Specimen—Standard Proportions and Tolerances A4. SPECIAL REQUIREMENTS FOR TESTING COMPACT SPECIMENS A4.1 Specimen A4.1.1 The standard compact specimen configuration is a single-edge-notched and fatigue precracked plate loaded in tension. The general proportions of the standard configuration are shown in Fig. A4.1. A4.1.2 Alternative configurations may have 2 # W/B # 4, but with other proportions unchanged. A4.2 Specimen Preparation A4.2.1 Generally applicable specifications regarding specimen size, configuration and preparation are given in Section 7. A4.3 Apparatus A4.3.1 Tension Testing Clevis—A loading clevis suitable for testing compact specimens is shown in Fig. A2.2 and discussed in A2.2. The clevis is designed to minimize friction effects by providing for rolling contact of the loading pins and rotation of the specimen during specimen loading. A4.3.2 Displacement Gage—Details regarding displacement gage design, calibration, and use are given in 6.4. For the compact specimen, displacements are essentially independent of gage length up to 1.2W. A4.4 Procedure A4.4.1 Measurement—Specimen width, W, and crack size, a, are measured from the plane of the centerline of the loading holes. The notched edge may be used as a convenient reference line, taking into account (that is, subtracting) the distance from the centerline of the holes to the notched edge to arrive at W and a. A4.4.1.1 General requirements concerning specimen measurement are given in 8.2. A4.4.2 Compact Specimen Testing—General principles concerning the loading clevis and its setup appear in A2.2. When assembling the loading train (clevises and their attachments to the tensile machine), care shall be taken to minimize eccentricity of loading due to misalignments external to the clevises. A4.4.2.1 The displacement gage is seated on the knife edges such as to maintain registry between knife edges and gage grooves. In the case of attachable knife edges, the gage is seated before the knife edge positioning screws are tightened. A4.4.2.2 The specified rate of increase of the stressintensity factor is within the range 0.55 and 2.75 MPa=m/s (30 and 150 ksi=in./min) corresponding to a loading rate for a standard (W/B = 2) 25 mm (1.0 in.) thick specimen between 0.33 and 1.67 kN/s (4.5 to 22.5 klbf/min). A4.4.2.3 Details concerning recording of the test record are given in 8.4. A4.5 Calculations A4.5.1 General requirements and procedures for interpreting the test record are given in 9.1. A4.5.2 Validity Requirements—Validity requirements in terms of limitation on Pmax/PQ and mandatory specimen size are given in 9.1.3 through 9.1.4. A4.5.3 Calculation of KQ—Compact specimen KQ is calculated in SI or inch-pound units of Pa=m (psi=in.) as follows (see Note A4.2): KQ 5 SD a PQ ·ƒ W =BBN=W (A4.1) where: SD SD S D a ƒ W 5 S a 21W for PQ B BN DF (A4.2) SD a 2 a a 0.886 1 4.64W 2 13.32 W 1 14.72 W a 3/2 12W 3 S DG a 2 5.6 W 4 which: = force as determined in 9.1.1, N (lbf), = specimen thickness as determined in 8.2.1, m (in.), = specimen thickness between the roots of the side grooves, as determined in 8.2.1, m (in.), Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 18 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 W a = specimen width (depth) as determined in A3.4.1, m (in.), and = crack size as determined in 8.2.3 and A4.4.1, m (in.). NOTE A4.1—Example: for a/W = 0.500, ƒ(a/W) = 9.66. NOTE A4.2—This expression for a/W is considered to be accurate within 0.5 % over the range 0.2 # a/W # 1 (18, 21). A4.5.4 Calculation of Crack Mouth Opening Compliance Using Crack Size Measurements—Compact specimen crack mouth opening compliance, Vm/P, is calculated in units of m/N (in./lb) as follows (see Note A4.4): SD Vm a 1 P 5 E’ Be · q W (A4.3) NOTE A4.4—This expression is considered to be accurate to within 1.0 % for a/W $ 0.2 (22). This expression is valid only for crack mouth opening displacement measured at the location of the integral knife edges shown in Fig. 3. Attachable knife edges must be reversed or inset to effect the same measurement points. A4.5.5 Calculation of Crack Size Using Crack Mouth Opening Compliance Measurements—Compact specimen normalized crack size is calculated as follows (see Note A4.5): a W5 1.00024.500·U113.157·U22172.551·U31879.944·U421514.671·U5 where: where: SD SD U5 a q W 5 S 19.75 a 12W D 2 F a a 0.5 1 0.192W 1 1.385 W 2 11 (A4.4) SD a 2 2.919 W 3 S DG a 1 1.842 W 4 for which: E’ = elastic constraint modulus(E for plane stress, Pa (psi); E/(1 − n2) for plane strain, Pa (psi), n = Poisson’s Ratio, Be = B – (B– BN)2/B, and B, BN, W and a are defined in A4.5.3. NOTE A4.3—Example: for a/W = 0.500, q(a/W) = 54.71. (A4.5) 1 E’ BeVm P Œ (A4.6) for which: Vm = crack mouth opening displacement, m (in.), P = applied force, N (lbf), and Be = B – (B– BN)2/B, and E’ is defined in A4.5.4 and B, BN, W and a are defined in A4.5.3. NOTE A4.5—This expression fits the equation in A4.5.4 within 0.01 % of W for 0.2 # a/W # 0.8 (22). It is valid only for crack mouth opening displacement measured at the location of the integral knife edges shown in Fig. 3. Attachable knife edges must be reversed or inset to effect the same measurement points. Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 19 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 NOTE 1—Surface finishes in µm. NOTE 2—A surfaces shall be perpendicular and parallel to within 0.002 W TIR. NOTE 3—The intersection of the crack starter notch tips with the two specimen surfaces shall be equally distant from the top and bottom edges of the specimen within 0.005 W. NOTE 4—Integral or attachable knife edges for clip gage attachment to the crack mouth may be used (see Figs. 3 and 4). NOTE 5—For starter notch and fatigue crack configuration see Fig. 5. NOTE 6—1.6 µm = 63 µin., 3.2 µm = 125 µin. FIG. A4.1 Compact C(T) Specimen—Standard Proportions and Tolerances A5. SPECIAL REQUIREMENTS FOR TESTING DISK-SHAPED COMPACT SPECIMENS A5.1 Specimen A5.1.1 The standard disk-shaped compact specimen configuration is a single-edge-notched and fatigue precracked disk segment loaded in tension (23). The general proportions of the standard configuration are shown in Fig. A5.1. A5.1.2 Alternative configurations may have 2 # W/B # 4, but with other proportions unchanged. A5.2 Specimen Preparation A5.2.1 Generally applicable specifications regarding specimen size, configuration and preparation are given in Section 7. A5.3 Apparatus A5.3.1 Tension Testing Clevis—A loading clevis suitable for testing disk-shaped compact specimens is shown in Fig. A2.2 and discussed in A2.2. The clevis is designed to minimize friction effects by providing for rolling contact of the loading pins and rotation of the specimen during specimen loading. A5.3.2 Displacement Gage—Details regarding displacement gage design, calibration, and use are given in 6.4. For the disk-shaped compact specimen, displacements are essentially independent of gage length up to 0.55W. A5.4 Procedure A5.4.1 Measurement—Analyses of this specimen assume it is machined from a circular blank and therefore measurements of circularity as well as width, W, and crack size, a, must be made. A5.4.1.1 The specimen blank shall be checked for circularity before specimen machining. The radius shall be measured at eight equally spaced points around the circumference, and one of these points shall lie in the intended crack plane. The average of these readings is taken as the radius, r. If any measurement differs from r by more than 5.0 %, the blank is to be machined to the required circularity. Otherwise, D = 2r = 1.35W. A5.4.1.2 Specimen width, W, and crack size, a, are measured from the plane of the centerline of the loading holes. The notched edge may be used as a convenient reference line taking into account (that is, subtracting) the distance from the centerline of the holes to the notched edge to arrive at W and a. A5.4.1.3 General requirements concerning specimen measurement are given in 8.2. A5.4.2 Disk-Shaped Compact Specimen Testing—General principles concerning the loading clevis and its setup appear in Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 20 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 NOTE 1—Surface finishes in µm. NOTE 2—A surfaces shall be perpendicular and parallel to within 0.002 W TIR. NOTE 3—The intersection of the crack starter notch tips with the two specimen surfaces shall be equally distant from the top and bottom edges of the specimen within 0.005 W. NOTE 4—Integral or attachable knife edges for clip gage attachment to the crack mouth nay be used (see Figs. 3 and 4). NOTE 5—For starter notch and fatigue crack configuration see Fig. 5. NOTE 6—1.6 µm = 63 µin, 3.2 µm = 125 µin. FIG. A5.1 Disk-Shaped Compact DC(T) Specimen—Standard Proportions and Tolerances TABLE A5.1 Results of KIc Tests on Disk-Shaped Compact DC(T), Compact C(T), Arc-Shaped A(T) Tension Specimens Laboratory 1 Ni-Cr-Mo Steel sys = 1324 MPa (192 ksi) DiskShaped Compact, DC(T) ArcShaped Tension, A(T) Laboratory 2 Ni-Cr-Mo Steel sys = 1289 MPa (187 ksi) DiskShaped Compact, DC(T) Standard Compact, A(T) Mean, X̄ 109.4 (99.5) 109.2 (99.4) 114.7 (104.4) 116.4 (105.9) Standard Deviation, S 4.38 (3.99) 3.76 (3.42) 1.86 (1.69) 3.56 (3.24) A5.5 Calculations A5.5.1 General requirements and procedures for interpreting the test record are given in 9.1. A5.5.2 Validity Requirements—Validity requirements in terms of limitation on Pmax/PQ and mandatory specimen size requirements are given in 9.1.3 through 9.1.4. A5.5.3 Calculation of KQ—Disk-shaped compact specimen KQ is calculated in SI or inch-pound units of Pa=m (psi=in.) as follows (see Note A5.2): KQ 5 NOTE—Units of mean and standard deviation are MPa=m (ksi=in.). SD a PQ ·ƒ W B=W (A5.1) where: A2.2. When assembling the loading train (clevises and their attachments to the tension machine), care shall be taken to minimize eccentricity of loading due to misalignments external to the clevises. A5.4.2.1 The displacement gage is seated on the knife edges such as to maintain registry between knife edges and gage grooves. In the case of attachable knife edges, the gage is seated before the knife edge positioning screws are tightened. A5.4.2.2 The specified rate of increase of the stressintensity factor is within the range 0.55 and 2.75 MPa=m/s (30 and 150 ksi=in./min) corresponding to a loading rate for a standard (W/B = 2) 25 mm (1.0 in.) thick specimen between 0.33 and 1.67 kN/s (4.5 to 22.5 klbf/min). A5.4.2.3 Details concerning recording of the test record are given in 8.4. SD SD S D a ƒ W 5 S a 21W DF a a 0.76 1 4.8W 2 11.58 W a 12W 2 (A5.2) SD a 1 11.43 W 3 S DG a 2 4.08 W 4 3/2 for PQ B W which: = force as determined in 9.1.1, N (lbf), = specimen thickness as determined in 8.2.1, m (in.), = specimen width (depth) as determined in A5.4.1, m (in.), and a = crack size as determined in 8.2.3 and A5.4.1, m (in.). NOTE A5.1—Example: for a/W = 0.500, ƒ(a/W) = 10.17. NOTE A5.2—This expression for a/W is considered to be accurate Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 21 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 within 0.3 % over the range 0.2 # a/W # 1 (24). 1.00024.459 · U12.066 · U2213.041 · U31167.627 · U42481.4 · U5 A5.5.4 Calculation of Crack Mouth Opening Compliance Using Crack Size Measurements—Disk-shaped compact specimen crack mouth opening compliance, Vm/P, is calculated in units of m/N (in./ lb) as follows (see Note A5.4): SD Vm a 1 P 5 E’ B · q W (A5.3) where: SD SD a q W 5 19.75 a 12W S D 2 F (A5.4) SD S DG a 2 a 3 a a 0.46920.056W11.86 W 22.06 W 10.789 W 4 for which: E’ = elastic constraint modulus (E for plane stress, Pa (psi); E/(1 − n2) for plane strain, Pa (psi), n = Poisson’s Ratio, and B, W and a are defined in A5.5.3. NOTE A5.3—Example: for a/W = 0.500, q(a/W) = 55.1. NOTE A5.4—This expression is considered to be accurate to within 1.0 % for a/W $ 0.2 (22). This expression is valid only for crack mouth opening displacement measured at the location of the integral knife edges shown in Fig. 3. Attachable knife edges must be reversed or inset to effect the same measurement points. A5.5.5 Calculation of Crack Size Using Crack Mouth Opening Compliance Measurements—Disk-shaped compact specimen normalized crack size is calculated as follows (see Note A5.5): a W5 (A5.5) where: U5 11 1 E’ BVm P Œ (A5.6) for which: Vm = crack mouth opening displacement, m (in.), P = applied force, N (lbf), and E’ is defined in A5.5.4 and B, W and a are defined in A5.5.3. NOTE A5.5—This expression fits the equation in A5.5.4 within 0.01 % of W for 0.2 # a/W # 0.8 (22). This expression is valid only for crack mouth opening displacement measured at the location of the integral knife edges shown in Fig. 3. Attachable knife edges must be reversed or inset to effect the same measurement points. A5.6 Precision and Bias (see also Section 11) A5.6.1 There has been no round-robin test program for the disk-shaped compact specimen. However, the results of two testing programs (23) designed to compare the results of the disk-shaped compact DC(T) specimen with those of the compact C(T) and arc-shaped tension A(T) specimens are summarized in Table A5.1. Based on the results in Table A5.1 and the geometric similarity of the specimens, there is no reason to suspect that the precision for the disk-shaped compact specimen would differ from that for the standard compact specimen. The arc-tension specimen has been shown (11) to have essentially the same grand mean and standard deviation as the standard compact specimen. A6. SPECIAL REQUIREMENTS FOR TESTING ARC-SHAPED TENSION SPECIMENS A6.1 Specimen A6.1.1 The standard arc-shaped tension specimen configuration is a single-edge-notched and fatigue precracked ring segment loaded in tension. The general proportions of (two variants of) the standard configuration are shown in Fig. A6.1. The value of the radius ratio r1/r2 is unspecified, so specimens may be taken from any cylindrical geometry. It should be noted, however, that specimens with r1/r2 = 0 (that is, from a solid cylinder) do not make efficient use of test material, because W for the arc-shaped tension specimen applies to hollow cylinders. The disk-shaped specimen shall be used for tests of solid cylinders (see Annex A5). A6.1.2 The arc-shaped tension specimen measures toughness only for a crack whose normal is circumferential and propagation direction is radial, designated C-R (see 3.1.3). For other crack plane orientations and propagation directions the bend (Annex A3) or compact (Annex A4) specimen are to be used. A6.1.3 The specimen depicted in Fig. A6.1(a) with X/W = 0.5 represents a half-ring segment. The specimen with X/W = 0 (Fig. A6.1(b)) is the smallest specimen of this configuration that can be cut from a ring. A6.1.4 Alternative configurations may have 2 # W/B # 4, but with other proportions unchanged. The use of alternative specimen proportions is advantageous when a specimen can be extracted from a ring segments without machining the inner and outer radii; that is, with no change in W. A6.2 Specimen Preparation A6.2.1 Generally applicable specifications regarding specimen size, configuration and preparation are given in Section 7. A6.3 Apparatus A6.3.1 Tension Testing Clevis—A loading clevis suitable for testing arc-shaped tension specimens is shown in Fig. A2.2 and discussed in A2.2. The clevis is designed to minimize friction effects by providing for rolling contact of the loading pins and rotation of the specimen during specimen loading. A6.3.2 Displacement Gage—Details regarding displacement gage design, calibration, and use are given in 6.4. For the arc-shaped tension specimen, displacements are essentially independent of gage length up to W/2. A6.3.2.1 An alternative means for measuring displacement is permitted for the specimen with X/W = 0.5. Conical Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 22 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 NOTE 1—Surface finishes in µm. NOTE 2—For starter notch and fatigue crack configurations see Fig. 5. NOTE 3—Alternative displacement gage reference points (see A6.4.1.1 for calculation of (a)). NOTE 4—Axis of holes to be tangent to inner radius within 0.005 W. NOTE 5—A surfaces to be perpendicular parallel as applicable within 0.002 W TIR. D surfaces to be perpendicular or parallel as applicable to A surfaces within 0.02 W TIR (see A6.4.1). NOTE 6—1.6 µm = 63 µin, 3.2 µm = 125 µin. FIG. A6.1 Arc-Shaped Tension A(T) Specimen Designs—Standard Proportions and Tolerances center-punch-type indentations are provided on the inner surface of the specimen at mid-thickness and in the plane of the centerline of the loading holes as shown in Fig. A6.1(a). Load-point displacement is measured at these points using a displacement gage fitted with points and meeting the requirements of 6.4. A6.4 Procedure A6.4.1 Measurement—Before testing, (r2 − r1) is measured to the nearest 0.03 mm (0.001 in.) or to 0.1 %, whichever is greater, at mid-thickness positions on both sides of, and immediately adjacent to, the crack starter notch mouth. The average of these two readings is taken as W. Measurement of (r2 − r1) is also made at four additional positions, two as close as possible to the loading holes and two at approximately one-half the circumferential distance between the loading holes and the crack plane. If any of these four measurements differ from W by more than 10 %, the specimen shall be discarded or reworked. The distance between the loading-hole centers and the outside surface of the specimen at the notch plane is measured to the nearest 0.03 mm (0.001 in.) or to 0.1 %, whichever is greater. This measurement is made on both sides of the specimen by referencing the loading holes. Specimen width is subtracted from the average of these two measurements and the difference recorded as the quantity X. The distance g between the crack mouth opening displacement measurement reference points is measured to within 5.0 %. [It should be recognized that g may be equal to the crack slot width, N, (for example, g = 6.4 mm (0.25 in.) in Fig. 3) or larger than N if machined knife edges are used.] The outer radius r2 is measured, if possible, to within 5.0 %. If not possible, then an average value of r2 is be calculated (see Note A6.1) from the measured (within 5.0 %) length, L, of the chord of the outer surface, which chord passes through the loading hole centers (see Fig. A6.2), using the following relationship: r2 5 L2 W1X 1 2 8~W 1 X! (A6.1) then: FIG. A6.2 Measurement of Outer Radius (r2) and Crack Size for the Arc-Shaped Tension A(T) Specimen (see A6.4.1) Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 23 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 r1 W r2 5 1 2 r2 (A6.2) NOTE A6.1—A10 % variation in the ratio r1/r2 will affect the value of stress-intensity factor by 1.0 % or less, providing that the relative crack size a/W is not less than 0.3. This, however, is based on the assumption that specimens are cut from stock of uniform, axisymmetric cross section. If inspection shows that the stock deviates from axisymmetry by more than 10 %, it should be reworked to within this tolerance. A6.4.1.1 Post-test crack size measurement (in accordance with 8.2.3) involves a special procedure due to the specimen’s curvature. A size measurement, m, is made from a reference point on the curved inner surface, adjacent to the crack mouth, to a point on the crack front. That size is greater than the corresponding distance from the virtual point of intersection between the crack plane and the inside circumference of the specimen (see Fig. A6.2). Error, e, is computed from the following expression: e 5 r1 2 Œ g2 r21 2 4 (A6.3) where g is the distance between the crack mouth opening displacement measurement reference points. If the relative error e/m < 0.01, then m is taken as the crack size; otherwise e is subtracted from m and the result recorded as the crack size. A6.4.2 Arc-Shaped Tension Specimen Testing—General principles concerning the loading clevis and its setup appear in A2.2. When assembling the load train (clevises and their attachments to the tension machine), care shall be taken to minimize eccentricity of loading due to misalignments external to the clevises. A6.4.2.1 The displacement gage is seated on the knife edges such as to maintain registry between knife edges and gage grooves. In the case of attachable knife edges, the gage is seated before the knife edge positioning screws are tightened. A6.4.2.2 The specified rate of increase of the stressintensity factor is within the range 0.55 and 2.75 MPa=m/s (30 and 150 ksi=in./min) corresponding to a loading rate between 0.21 and 1.04 kN/s (2.8 to 14.0 klbf/min) for a standard (W/B = 2) 25 mm (1.0 in.) thick specimen with X/W = 0.5, and between 0.33 and 1.67 kN/s (4.5 to 22.5 klbf/min) for a standard (W/B = 2) 1 in. thick specimen with X/W = 0. A6.4.2.3 Details concerning recording of the test record are given in 8.4. A6.5 Calculations A6.5.1 Interpretation of Test Record—General requirements and procedures for interpreting the test record are given in 9.1. A6.5.2 Validity Requirements—Validity requirements in terms of limitation on Pmax/PQ and mandatory specimen size are given in 9.1.3 through 9.1.4. A6.5.3 Calculation of KQ—Arc-shaped tension specimen KQ is calculated in SI or inch-pound units of Pa=m (psi=in.) as follows (see Note A6.3): KQ 5 S X a P 3 1 1.9 1 1.1W B=W W where: DF (A6.4) S a 1 1 0.25 1 2 W DS 2 r1 12r 2 DG S D a ·ƒ W S D SŒD F a ƒ W 5 a W a 12W 3/2 SD a a 3.74 2 6.30W 1 6.32 W 2 S DG a 2 2.43 W 3 (A6.5) for which: PQ = force as determined in 9.1.1, N (lbf), B = specimen thickness as determined in 8.2.1, m (in.), X = loading hole offset as determined in A6.4.1, m (in.), W = specimen width (depth) as determined in A6.4.1, m (in.), a = crack size as determined in 8.2.3 and A6.4.1.1, m (in.), and r1/r2 = ratio of inner-to-outer radii as determined in A6.4.1. NOTE A6.2—Example: for a/W = 0.500, ƒ(a/W) = 3.73. NOTE A6.3—The accuracy of this expression for a/W for all values of r1/r2 is considered to be as follows: (1) within 1.0 % for 0.45 # a/W # 0.55 and X/W of 0 or 0.5, (2) within 1.5 % for 0.2 # a/W # 1 and X/W of 0 or 0.5, and (3) within 3.0 % for 0.2 # a/W # 1 and 0 # X/W # 1 (25). A6.5.4 Calculation of Crack Mouth Opening Compliance Using Crack Size Measurements—Arc-shaped tension specimen crack mouth opening compliance, Vm/P, is calculated in units of m/N (in./lb) as follows (see Note A6.5): for the specimen with X/W = 0: SDF S a Vm P 1 W a r1 P 5 E’ B · 0.43 1 2 r2 1 q1 W D S DG (A6.6) where: SD S a P1 W 5 a 11W a 12W D (A6.7) 2 and: SD SD a a a q1 W 5 0.542 1 13.137W 2 12.316 W 2 SD a 1 6.576 W 3 (A6.8) or, for the specimen with X/W = 0.5: SDF S a Vm P 2 W a r1 P 5 E’ B · 0.45 1 2 r2 1 q2 W D S DG (A6.9) where: SD S a P2 W 5 a 21W a 12W D (A6.10) 2 and: SD SD a a a q2 W 5 0.399 1 12.63W 2 9.838 W 2 SD a 1 4.66 W 3 (A6.11) for which: E’ = elastic constraint modulus (E for plane stress, Pa (psi); E/(1 − n2) for plane strain, Pa (psi)), n = Poisson’s Ratio, and X, B, W, a, and (r1/r2) are defined in A6.5.3. NOTE A6.4—Example: for a/W = 0.500, p1(a/W) = 6.00, q1(a/W) = Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 24 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 4.85, p2(a/W) = 10.00, and q2(a/W) = 4.84. NOTE A6.5—These expressions are considered to be accurate within 1.4 % (X/W = 0) or 1.6 % (X/W = 0.5) for 0.2 # a/W # 0.8 and (r1/r2) $ 0.4 (22). These expressions are valid only for crack mouth opening displacement measured at the location of integral knife edges comparable to that shown in Fig. 3. Attachable knife edges must be reversed or inset to effect the same measurement points. A6.5.5 Calculation of Crack Size Using Crack Mouth Opening Compliance Measurements—Arc-shaped tension specimen normalized crack size is calculated as follows (see Note A6.6): for the specimen with X/W = 0: a W5 (A6.12) 0.98923.463 · U20.171 · U2124.354 · U3272.805 · U4184.375 · U5 where: U5 11 1 E’ BVm r1 1 1 0.101 1 2 r P 2 Œ F S DG (A6.13) or, for the specimen with X/W = 0.5: a W5 (A6.14) 0.98624.082 · U25.065 · U2186.819 · U32313.338 · U41429.101 · U5 where: U5 11 1 E’ BVm r1 1 1 0.108 1 2 r P 2 Œ F S DG (A6.15) for which: Vm = crack mouth opening displacement, m (in.), P = applied force, N (lbf), and E’ is defined in A6.5.4 and B, W, a and (r1/r2) are defined in A6.5.3. NOTE A6.6—This expression fits the equations in A6.5.4 within 0.003W for 0.2 # a/W # 0.8, (r1/r2) $ 0.4, and X/W = 0 or 0.5 (21). This expression is valid only for crack mouth opening displacement measured at the location of the integral knife edges comparable to that shown in Fig. 3. Attachable knife edges must be reversed or inset to effect the same measurement points. A7. SPECIAL REQUIREMENTS FOR TESTING ARC-SHAPED BEND SPECIMENS A7.1 Specimen A7.1.1 The standard arc-shaped bend specimen configuration (26) is a single-edge-notched and fatigue precracked ring segment loaded in bending. The general proportions of the standard configuration are shown in Fig. A7.1. The value of the radius ratio r1/r2 is limited to the range 0.6 to 1.0 when the span-to-width ratio S/W is 4, and from 0.4 to 1.0 when S/W is 3. For cylinders with radius ratios less than these limits, the arc-shaped tension-loaded specimen or the disk-shaped specimen shall be used. A7.1.2 The arc-shaped bend specimen measures toughness only for a crack whose normal is circumferential and propa- NOTE NOTE NOTE NOTE NOTE NOTE gation direction is radial, designated C-R (see 3.1.3). For other crack plane orientations and propagation directions the bend (Annex A3) or compact (Annex A4) specimen are to be used. A7.1.3 Alternative configurations may have 2 # W/B # 4, but with other proportions unchanged. The use of alternative specimen proportions is advantageous when a specimen can be extracted from a ring segment without machining the inner and outer radii. A7.2 Specimen Preparation A7.2.1 Generally applicable specifications regarding specimen size, configuration and preparation are given in Section 7. 1—Surface finishes in µm. 2—A surfaces shall be perpendicular and parallel as applicable within 0.0001 W TIR. 3—Crack starter notch shall be perpendicular to specimen surfaces within 6 2° 4—Integral or attachable knife edges for clip gage attachment (see Figs. 3 and 4) shall be provided for displacement gage attachment. 5—For starter notch and fatigue crack configuration, see Fig. 5. 6—1.6 µm = 63 µin., 3.2 µm = 125 µin. FIG. A7.1 Arc-Shaped Bend A(B) Specimen—Standard Proportions and Tolerances Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 25 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 reworked. The distance in the crack plane between the chord that connects the two machined flat surfaces and the outer radius is measured to the nearest 0.03 mm (0.001 in.) or to 0.1 %, whichever is greater. This measurement is made on both sides of the specimen referencing each machined flat surface. Specimen width W is subtracted from the average of these two measurements and the difference recorded as the quantity Z. The distance g between the crack mouth opening displacement measurement reference points is measured to within 5.0 %. [It should be recognized that g may be equal to the crack slot width, N, (for example, g = 6.4 mm (0.25 in.) in Fig. 3) or larger than N if machined knife edges are used.] The outer radius r2 is measured, if possible, to within 5.0 %. If not possible, then an average value of r2 is calculated (see Note A6.1) from the measured (within 5.0 %) length, L, of the chord of the outer surface (that is, the chord established by the machined flat surfaces (see Fig. A7.2)) using the following relationship: r2 5 L2 W1Z 1 2 8~W 1 Z! (A7.1) then: r1 W r2 5 1 2 r2 FIG. A7.2 Measurement of Outer Radius (r2) and Crack Size for the Arc-Shaped Bend A(B) Specimen (see A7.4.1.1) A7.3 Apparatus A7.3.1 Bend Test Fixture—The loading fixture for standard bend specimen testing in Annex A3 is equally suitable for the arc-shaped bend specimen. The fixture is designed to minimize friction effects by allowing the rollers to rotate and translate slightly as the specimen is loaded, thus providing rolling contact. A7.3.2 Displacement Gage—Details regarding displacement gage design, calibration, and use are given in 6.4. For the standard bend specimen, displacements are essentially independent of gage length up to W/2. It is presumed that for the cylindrical bend specimen, displacements are essentially independent of gage length up to W/2 as well. A7.4 Procedure A7.4.1 Measurement—Before testing, (r2 − r1) is measured to the nearest 0.03 mm (0.001 in.) or to 0.1 %, whichever is greater, at mid-thickness positions on both sides of, and immediately adjacent to, the crack starter notch mouth. The average of these two readings is taken as W. Measurement of (r2 − r1) is made also at four additional positions, two as close as possible to the intersection of the inside radius with the machined flat surfaces, and two at approximately one-half the circumferential distance between the machined flat surfaces and the crack plane. If any of these four measurements differ from W by more than 10 %, the specimen shall be discarded or (A7.2) NOTE A7.1—A10 % variation in the ratio r1/r2 will affect the value of the stress-intensity factor by 1.2 % or less, providing that the relative crack length a/W is not less than 0.3. This, however, is based on the assumption that the specimen is cut from stock of uniform, axisymmetric cross section. If inspection shows that the stock deviates from axisymmetry by more than 10 %, it should be reworked to within this tolerance. A7.4.1.1 Post-test crack size measurement (in accordance with 8.2.3) involves a special procedure due to the specimen’s curvature. A size measurement, m, is made from a reference point on the curved inner surface, adjacent to the crack mouth, to a point on the crack front. That size is greater than the corresponding distance from the virtual point of intersection between the crack plane and the inside circumference of the specimen (see Fig. A7.2). Error, e, is computed from the following expression: e 5 r1 2 Œ g2 r21 2 4 (A7.3) where g is the separation of the crack mouth opening displacement measurement reference points. If the relative error e/m < 0.01, then m is taken as the crack size; otherwise e is subtracted from m and the result recorded as the crack size. A7.4.2 Arc-Shaped Bend Specimen Testing—General principles concerning the loading fixture and its setup appear in A2.1. A7.4.2.1 The displacement gage is seated on the knife edges such as to maintain registry between knife edges and gage grooves. In the case of attachable knife edges, the gage is seated before the knife edge positioning screws are tightened. A7.4.2.2 The specified rate of increase of the stressintensity factor (see 8.3) ranges from 0.55 to 2.75 MPa=m/s (30 to 150 ksi=in./min) and corresponds to a loading rate between 0.33 and 2.37 kN/s (4.5 to 32.0 klbf/min) for the standard (W/B = 2) 25 mm (1.0 in.) thick specimen with S = Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 26 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 3W, and between 0.24 and 1.71 kN/s (3.2 to 23.0 klbf/min) for the standard (W/B = 2) 25 mm (1.0 in.) thick specimen with S = 4W. A7.4.2.3 Details concerning recording of the test record are given in 8.4. A7.5 Calculations A7.5.1 Interpretation of Test Record—General requirements and procedures for interpreting the test record are given in 9.1. A7.5.2 Validity Requirements—Validity requirements in terms of limitation on Pmax/PQ and mandatory specimen size are given in 9.1.3 through 9.1.4. A7.5.3 Calculation of KQ—Arc-shaped bend specimen KQ is calculated in SI or inch-pound units of Pa=m (psi=in.) as follows (see Note A7.3): For S = 4W: KQ 5 F S D S DG S D a PQS r1 · h1 W 3/2 1 1 1 2 r BW 2 a · ƒ1 W (A7.4) where: SD SD a a a h1 W 5 0.29 2 0.66W 1 0.37 W 2 (A7.5) and: SD F SD S D S DG a 2 a a 0.677 1 1.078W 2 1.43 W 1 0.669 W a ƒ1 W 5 a 3/2 12W 3 (A7.6) for S = 3W: KQ 5 F S D S DG S D a PQS r1 · h2 W 3/2 1 1 1 2 r BW 2 a · ƒ2 W (A7.7) where: SD SD a a a h2 W 5 0.20 2 0.32W 1 0.12 W 2 (A7.8) and: F SD S D S DG a 2 a a 0.644 1 1.11W 2 1.49 W 1 0.73 W a ƒ2 W 5 a 3/2 12W SD 3 (A7.9) for PQ B S W a r1 r2 which: = force as determined in 9.1.1, N (lbf), = specimen thickness as determined in 8.2.1, m (in.), = span as determined in A7.4.2 and A2.1, m (in.), = specimen width as determined in A7.4.1, m (in.), = crack size as determined in 8.2.3 and A7.4.1.1, m (in.), = inner radius as determined in A7.4.1, m (in.), and = outer radius as determined in A7.4.1, m (in.). NOTE A7.2—Example: for a/W = 0.500, h1(a/W) = 0.0525, f1(a/W) = 2.66, h2(a/W) = 0.0700, and f2(a/W) = 2.60. NOTE A7.3—These expressions are considered to be accurate to within 1.0 % for 0.2 # a/W # 1.0, 0.6 # r1/r2 # 1.0, and S = 4W; and 1.5 % for 0.2 # a/W # 1.0, 0.4 # r1/r2 # 1.0, and S = 3 (26). A8. FATIGUE PRECRACKING KIc FRACTURE TOUGHNESS SPECIMENS A8.1 Introduction A8.1.1 Experience has shown that even the narrowest practical machined notch cannot simulate a natural crack well enough to provide a satisfactory measurement of KIc. Recourse is made to an artifice consisting of a narrow notch from which extends a comparatively short fatigue crack, called the precrack. The dimensions of the notch and the precrack, and the sharpness of the precrack, must meet certain conditions which can be readily met with most engineering materials. There are, however, some materials that are too brittle to be fatigue cracked; they fracture at the onset of fatigue crack initiation. These are outside the scope of this test method. An exception is beryllium, which requires special fatigue precracking procedures that are described in Annex A9. A8.1.2 The objective of fatigue precracking is to produce a sharp crack which is unaffected by the precracking procedure. In what follows, guidance is offered on the production of satisfactory fatigue precracks. Associated requirements to ensure a valid KIc test are also given. A8.1.3 A fatigue precrack is produced by cyclically loading the notched specimen at a ratio of minimum-to-maximum stress between −1 and +0.1 for a number of cycles, usually between about 104 and 106 depending on specimen size, notch preparation, and cyclic stress- intensity factor level. The maximum stress-intensity factor, Kmax, during any stage of fatigue crack growth shall not exceed 80 % of the KQ value determined in the subsequent test if KQ is to qualify as a valid KIc result. For the terminal stage of fatigue precracking (2.5 % of crack size a), Kmax shall not exceed 60 % of KQ. Some fraction of the total number of cycles required to produce the fatigue precrack is consumed in the initiation of the crack at the notch root; the remainder represents growth of the crack to the specified size. If the total number of cycles is excessive, the cause is usually an excessive number of cycles required for initiation rather than subsequent crack growth. Crack initiation can be hastened by: (1) increasing the acuity of the notch tip; (2) using a chevron starter notch (see Fig. 5) in place of a straight-through starter notch; (3) applying a static preload to the specimen such that the notch tip is compressed in a direction normal to the intended crack plane, but without allowing the nominal compressive stress to exceed the compressive yield strength of the material; and (4) using a negative fatigue stress ratio. A8.2 Equipment A8.2.1 The fixtures recommended for fracture testing are also suitable for fatigue precracking at positive stress intensity ratios. K-calibration for the specimen using the fixtures shall be known with an error not exceeding 5.0 %. K-calibration is the relation between the stress- intensity factor K and either the force or some prescribed displacement and the specimen Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 27 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 dimensions (1). If different fixtures are used, the appropriate K calibration shall be determined experimentally with those fixtures (8). The advantage of experimental K calibration, compared to numerical methods of analysis, is that accurate modeling of the boundary conditions with the actual fixtures is assured. It is important to bear in mind that if the fatigue cycle involves reversal of force, the K calibration can be very sensitive to the distribution of clamping forces necessary to grip the specimen. A8.2.2 The fatigue cracking setup shall be such that the stress distribution is uniform through the specimen thickness; otherwise the crack will not grow uniformly. The stress distribution shall also be symmetrical about the plane of the prospective crack; otherwise the crack will deviate unduly from that plane and the test result will be significantly affected, possibly invalidated (8). A single obvious exception to these requirements is that of cantilever bending used only for fatigue precracking beryllium (see A3.2.3 and A9.2.3.2). A8.3 Specimen Requirements A8.3.1 Fatigue precracking shall be done with the specimen in the finally heat-treated, mechanically-worked, or environmentally-conditioned state in which it is to be tested. A8.3.2 The combination of starter notch and fatigue precrack shall conform to the requirements of Fig. 5. The standard specified crack size ranges from 0.45W to 0.55W and is the total size of the starter notch slot plus fatigue crack. To facilitate fatigue precracking at a low level of stress intensity, the notch root radius of a straight-across notch should be no more than 0.08 mm (0.003 in.). The chevron notch (see Fig. 5) root radius can be as much as 0.25 mm (0.010 in.) because of the compound stress intensification at the point of the chevron. Crack initiation in either specimen variety can be accelerated by precompressing the notch tip region, as stated in A8.1.3. A8.3.3 It is suggested that two pencil lines be marked on each side of the specimen normal to the anticipated crack-path surface traces. The line most distant from the notch tip shall indicate the minimum required size of fatigue crack; the other (at a lesser distance) the terminal part of that size equal to not less than 2.5 % of the overall crack size of notch plus fatigue crack; that is, 0.0125W. During the final stage of fatigue crack extension, for at least this distance, the ratio of maximum stress-intensity factor of the fatigue cycle to the Young’s modulus of the material, Kmax/E, shall not exceed 0.0003 =m (0.002 =in.). Furthermore, Kmax must not exceed 60 % of the KQ value determined in the subsequent test if KQ is to qualify as a valid KIc result. A8.4 Precracking Procedure A8.4.1 Fatigue precracking normally shall be done at room temperature with the specimen in the finally heat-treated, mechanically-worked, or environmentally-conditioned state in which it is to be tested. Different fatigue precracking temperatures and intermediate thermal/mechanical/environmental treatments between fatigue precracking and testing shall be used only when such treatments are necessary to simulate the conditions for a specific structural application and required dimensions and tolerances on specimen size and shape can be maintained. A8.4.2 Fatigue precracking may be conducted under either force control or displacement control provided that the appropriate K-calibration is known with requisite accuracy for the specimen and fixture (see A8.2.1). If the force range is maintained constant, Kmax and the K range (DK) will increase with crack size; if the displacement range is maintained constant, the opposite will happen. The initial value of the maximum fatigue force or displacement shall be calculated from the K calibration and the specimen and notch dimensions. It is suggested that this force be selected such that the maximum stress-intensity factor in the initial portion of the fatigue cycle does not exceed 80 % of the estimated KIc value of the material. Higher Kmax values may result in undesirably high crack growth rates. The minimum is then selected so that the stress ratio is between −1 and +0.1. The more negative the stress ratio, the faster the fatigue precrack will be completed, but this advantage is offset by the need for more elaborate fixtures than are required when the stress ratio is positive. A8.4.3 The specimen shall be accurately located in the loading fixture and secured as required so that the boundary conditions correspond to the applicable K calibration. Fatigue cycling is then begun, usually with a sinusoidal waveform and near to the highest practical frequency. There is no known marked frequency effect on fatigue precrack formation up to at least 100 Hz in the absence of adverse environments. The specimen shall be carefully monitored until crack initiation is observed on one side. If crack initiation is not observed on the other side before appreciable growth is observed on the first, then fatigue cycling should be stopped to try to determine the cause and remedy for the unsymmetrical behavior. Sometimes, simply turning the specimen end for end in relation to the fixture will solve the problem. When the most advanced crack trace has almost reached the first scribed line corresponding to 97.5 % of the final crack size, the maximum force or displacement, as appropriate, shall be reduced so that the terminal value of Kmax is unlikely to exceed 60 % of the estimated minimum value of KIc of the material, and also that the terminal value of Kmax/E will not exceed 0.0003 =m (0.002 =in.). The minimum setting is then adjusted so that the stress ratio is between −1 and +0.1. Fatigue cycling is then continued until the surface traces on both sides of the specimen indicate that the overall size of notch plus crack will meet the requirements of 7.3.2.1 and 7.3.2.2, and Fig. 5 of this test method. A8.4.4 When fatigue cracking is conducted at temperature T1 and testing at different temperature T2, Kmax(T1) shall not exceed 0.6[(sys (T1)/sys (T2)] [KQ(T2) = KIc(T2)], where sys (T1) and sys (T2) are the yield strengths at the respective temperatures T1 and T2. Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 28 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 A9. SPECIAL REQUIREMENTS FOR TESTING HOT-PRESSED BERYLLIUM A9.1 Scope A9.1.1 This Annex describes special requirements for determining the plane-strain fracture toughness of hot pressed beryllium. With only few exceptions, the provisions of Test Method E399 are applicable to the fracture toughness testing of beryllium. However, certain modifications to specimen preparation and record analysis, as described in this Annex, arise because of beryllium’s potential toxicity, inherent brittleness associated with cleavage fracture, high elastic modulus, nonlinear-elastic behavior, and very high fatigue crack growth rates (27, 28). bending is used as a conservative approximation of Kmax for cantilever bending (substituting, of course, maximum fatigue force for PQ). An approximation (32) obtained by curve-fitting the compliance calibration data of (8) for a cantilever bend specimen with L/W = 2, is (see Note A9.3) (in units of Pa=m (psi=in.): NOTE A9.1—Inhalation of dust or fumes from metallic beryllium, beryllium oxide, or soluble beryllium compounds can result in systemic disease. Machining and testing of beryllium require special precautions and an industrial hygienist familiar with OSHA Standards should be consulted before a beryllium test program is started. (A9.2) A9.2 Specimen Size, Configuration and Preparation A9.2.1 Specimen Size—The thickness of hot-pressed beryllium specimens shall be 13 mm (0.50 in.) or greater to avoid excessive nonlinearity in the elastic portion of the forceCMOD record. A9.2.2 Specimen Configuration—Standard bend SE(B) or compact C(T) specimens may be used. A straight-through notch (see Fig. 5) shall be used to provide sufficient fatigue crack extension in the required reversed loading. A9.2.3 Specimen Preparation: A9.2.3.1 Machining—Beryllium is easy to machine. Nonetheless, machining damage is frequently encountered and tensile test specimens are therefore etched to remove the damaged layer. Experience has shown, however, that such is not required in the preparation of beryllium fracture toughness specimens (29). A9.2.3.2 Fatigue Cracking—Fatigue cracking is done in reverse loading, with the compression cycle 2 to 3 times that of the tension cycle (−3 < R < −2). Under such loading, the fatigue crack growth rate decreases with crack extension, and it is necessary to gradually increase the tension cycle level to develop sufficiently long cracks. Generally, for the final 2.5 % of crack growth, tension force exceeding 60 % of the anticipated KIc value will be required. To prevent the specimen from breaking, values of Kmax greater than 80 % of the anticipated KIc shall be avoided. As a guideline, KIc at room temperature and in normal laboratory environments may be assumed to be between 10 and 11 MPa=m (9 and 10 ksi=in.). Fatigue crack progress is to be observed on both sides of the specimen. It has proven helpful to use a dye solution (such as those used for penetrant inspection) to delineate the crack since crack opening is relatively small due to the high elastic modulus of this metal. Fatigue cracking of compact specimens in tension-compression loading is especially difficult. A special gripping arrangement is described in (30). Fatigue cracking SE(B) specimens has been successfully accomplished in cantilever bending (27, 31). The expression in A3.5.3 for KQ applicable to three-point Kmax 5 SD a PL ƒ BW3/2 W (A9.1) where: SD SD a a a ƒ W 5 0.326 1 30.318W 2 59.905 W 2 SD a 1 68.889 W 3 for which: P = maximum cyclic force, N (lbf), L = S/2 = one-half span, m (in.), and S, B, W, and a are as defined in A3.5.3 or A4.5.3. NOTE A9.2—Example: for a/W = 0.500, ƒ(a/W) = 9.12. NOTE A9.3—This expression is considered to be accurate within 5.0 % for a/W # 0.6 (8). A9.2.3.3 When using cantilever bending, excessive clamping forces will produce cracks at the specimen edges that will invalidate the test. A9.3 Testing and Record Analyses A9.3.1 Forces and displacements will be relatively low, and the production of a satisfactory test record will require high gain in the clip gage circuit. It is advantageous to use a relatively slow loading rate corresponding to about 0.18 MPa=m/s (10 ksi=in./min) in order to provide sufficient time to unload the specimen if the recording gain controls require adjustment to achieve the slope range specified by this test method. When the elastic portion of the force-versus-CMOD record is nonlinear, an initial slope is determined by drawing a straight line between two points on the force-CMOD record; one point at 20 % of maximum force, the other at 80 % of maximum force. A9.4 Precision and Bias (see also Section 11) A9.4.1 Hot pressed beryllium from two suppliers was tested in six laboratories in accordance with the procedures of this Annex with the following results: sys – Grand Mean, X Standard Deviation, S Batch 1 236 MPa (34.3 ksi) 10.7 (9.72) Batch 2 197 MPa (28.6 ksi) 10.4 (9.50) 0.93 (0.85) 0.78 (0.71) NOTE A9.4—Units of grand mean and standard deviation are MPa=m (ksi=in.). A9.4.2 The tensile elongation of beryllium depends on temperature and strain rate, but the magnitude of such variability on KIc is not known. However, the results of an interlaboratory program (29) did not appear influenced by loading rates which varied from 0.20 to 2.62 MPa=m/s (11 to 143 ksi=in./min). Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 29 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 A10. SPECIAL REQUIREMENTS FOR RAPID-FORCE, PLANE-STRAIN FRACTURE TOUGHNESS KIc (t) TESTING A10.1 Scope A10.1.1 This Annex specifies the method for determining plane-strain fracture toughness (KIc) of metallic materials at loading rates exceeding those for conventional (quasi-static) testing [that is, rates exceeding 2.75 MPa=m/s (150 ksi=in./ min)]. A10.2 Summary of Requirements A10.2.1 The special requirements described in this Annex for plane-strain fracture toughness testing at loading rates exceeding those for conventional (quasi-static) plane-strain fracture toughness tests do not apply to impact or quasi-impact testing (free-falling or swinging masses). They apply only to rapid loading of conventional fracture toughness specimens to the measurement point in not less than one millisecond. Force versus time, crack mouth opening displacement (CMOD) versus time, and force versus CMOD curves are recorded. The initial linear portion of the force versus CMOD record must define PQ unambiguously. The test time and an optionally · calculated average stress-intensity factor rate K characterize the rapid-force load test. The yield strength used in analysis of the test data can be measured directly or estimated for the loading time of the fracture test. All criteria for quasi-static KIc determination apply equally to the rapid-force test. The rapidforce, plane-strain fracture toughness property is denoted by KIc( ), where the time to reach the force corresponding to KQ is indicated in milliseconds within the brackets ( ). A10.3 Significance and Use A10.3.1 The significance of conventional (quasi-static) KIc applies also to rapid-force KIc (t). The plane-strain fracture toughness of certain materials may be sensitive to the loading rate and decreased toughness may be noted as the loading rate increases. A10.4 Terminology A10.4.1 Definitions: A10.4.1.1 The definitions given in Terminology E1823 and Section 3 apply to this Annex. · A10.4.1.2 stress-intensity factor rate, K (FL-3/2 t-1)—change in stress-intensity factor, K, per unit time. A10.4.2 Description of Terms Specific to This Annex: A10.4.2.1 rapid force—any force in fracture testing that results in an average stress-intensity factor rate in excess of 2.75 MPa=m/s (150 ksi=in./min). A10.4.2.2 rapid-force plane-strain fracture toughness, KIc (t) (FL-3/2)—the crack extension resistance under conditions of crack-tip plane strain at average loading rates exceeding 2.75 MPa=m/s (150 ksi=in./min). The time, t, in milliseconds to reach PQ is indicated in the brackets ( ) following KIc. A10.5 Apparatus A10.5.1 Loading—Hydraulic machines with rapid-acting servo-controlled valves are generally used. Depending on the compliance of the loading system and the pump capacity, an accumulator may be required. A10.5.2 Fixtures—Fixtures used for quasi-static, planestrain fracture toughness tests are generally suitable for rapidforce tests, except rapid-force fixtures are to be fabricated from materials unaffected by rapid loading. A10.5.3 Force and Displacement Transducers—The transducers used for quasi-static, plane-strain fracture toughness tests are generally suitable for rapid-force tests. However, these transducers must have response characteristics without inertial effects that could contaminate the force and displacement signals. NOTE A10.1—While not required, the resonant frequencies of these transducers may be determined by suitably exciting them and observing the wave characteristic on an oscilloscope. If ringing (high frequency oscillation) is observed within the time period required to reach force PQ, the stiffness of the transducers is to be increased or the mass reduced. Force transducers are usually stiff and are unlikely to be problematical at the loading time minimum of 1 ms. On the other hand, the displacement transducer might be cause for concern depending on its design. The cantilever beam displacement gage described in Annex A1 has been used successfully at loading times slightly lower than 1 ms (33). The resonant frequency of the gage when mounted on a specimen in a conventional manner and excited by tapping is about 3300 Hz. The free-arm resonant frequency is about 750 Hz. Other gages of the same type, but having different dimensions, should operate satisfactorily if their free arm resonance is at least 750 Hz. The following equation may be used to estimate the free-arm resonant frequency of such gages: ƒ 5 C~0.162! Œ b2 Eg rl4 (A10.1) where: ƒ = resonant frequency, Hz, C = dimensional constant, 0.319 for SI and 1.0 for inchpound, b = arm thickness, m (in.), E = elastic modulus of the arms, Pa (psi), g = gravitational acceleration, 9.807 m/s2 (386 in./s2), r = density of the arm material in, kg/m3 (lbm/in.3), and l = length of the uniform-thickness section of the arm, m (in.). A10.5.4 Signal Conditioners—Amplification or filtering of the transducer signals may be necessary. Such signal conditioning devices are to have frequency response from dc to at least 20t-1 (kHz) where t is the test time in ms as defined in A10.7.2. Conventional mechanical recording devices may not have sufficient frequency response to permit direct plotting of the force versus time and the displacement versus time signals. A10.6 Procedure A10.6.1 Loading Rate—The rate of loading is discretionary, but the time to reach the force corresponding to KQ shall be not less than 1 ms. A preload is permitted to eliminate ringing in the force or displacement transducers associated with the closing of clearances in the load train at the start of rapid loading. Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 30 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 A10.6.2 For every test, force versus time, crack mouth opening displacment (CMOD) versus time, and force versus CMOD records shall be obtained. The time scale of the records shall be accurately determined, as the time is used to characterize the test. The time-dependent records are to be examined for the presence of ringing before reaching the PQ force. Ringing can result from the inertial effects described in Note A10.1. The special record analysis procedure described in A10.7.2 may be helpful in assessing the magnitude of such effects. NOTE A10.2—It should be recognized that some materials may exhibit a burst of crack extension at forces less than PQ, sufficiently abrupt to produce ringing in the displacement transducer signal. Such an abrupt advance of the crack may be associated with material inhomogeneities local to the fatigue crack tip. If the ringing is severe, it may not be possible to unambiguously determine PQ. The presence of such bursts of crack extension should be recorded for those tests having analyzable force versus CMOD records. NOTE A10.3—Test data may be directly recorded if the recording device has sufficient frequency response. Generally, it is advantageous to use a storage device that will capture the data and permit playing it out at a sufficiently slow speed that a pen recorder can be used to produce the required record. Such storage devices are commonly available in the form of digital storage oscilloscopes having pen recorder outputs. Separate storage instruments are also available. In general, these digital storage devices have performance characteristics that are more than adequate to capture, store, and replay the transducer signals from a 1 ms test. Calculations show, for example, that for a typical fracture test as described in (33), the crack mouth opening displacement (CMOD) resolution would be approximately 0.76 µm/sample (0.030 mils/sample) and the force resolution would be approximately 712 N/sample (160 lbf/sample). It should be possible to obtain at least 1000 simultaneous samples of force and CMOD during such a test. A digital storage scope capable of at least this performance would have the following characteristics: maximum digitizing rate 1 MHz, maximum sensitivity 6 100 mV, resolution 0.025 %, and memory of 4096 words by 12 bits. It may be necessary to amplify the output of the clip gage moderately, and possibly that of the force transducer depending on its capacity in terms of the range required. FIG. A10.1 Special Requirements for Analysis of ForceDisplacement Records (5 % Secant Line Not Shown) The above values of resolution are based on a total noise figure of approximately 50 µV. A10.7 Calculation and Interpretation of Results A10.7.1 Special requirements are placed on the analysis of the rapid-force versus CMOD record, because experience (33) has shown these records to be frequently not as smooth in the linear range as those obtained from quasi-static tests. The special requirements of this annex are designed to ensure that an unambiguous value of PQ can be determined. A10.7.1.1 The rapid-force versus CMOD record is illustrated in Fig. A10.1. It is analyzed as follows: Straight line OA is constructed to best represent the initial portion of the test record, which ideally should be linear but may not be smooth. Line OP5 is then constructed as described in 9.1.1 (see Fig. 7) to determine PQ. A vertical line is drawn at nP passing through PQ. Pn is defined at the point of intersection of this line with the line OA. Lines BC and DE are drawn parallel to OA, with BC passing through (Pn + 0.05Pn), and DE passing through PQ (Pn − 0.05Pn). A horizontal line is drawn at P = 0.5PQ. For the test to be valid, the rapid-force versus CMOD curve up to PQ must lie within the envelope described by these parallel lines for that portion of the record with P $ 0.5PQ. A10.7.2 Test time t in milliseconds is determined from the record of force versus time shown schematically in Fig. A10.2. The best straight line OA is drawn through the most nearly linear portion of the record. Time t is represented as the span from the intersection of this line with the time axis, to the intersection with the time axis of a vertical line from PQ. This time t is reported in the brackets ( ) following the KIc value. An · average stress intensity rate K is calculated by dividing KQ or KIc by t, the result being expressed in MPa=m/s or ksi=in./s. Minor errors in determining the loading time are not important because significant changes in toughness require several orders of magnitude change in loading rate. A10.7.3 The 0.2 % offset tensile yield strength sys is used in determining satisfaction of the specimen size requirements FIG. A10.2 Determination of Test Time from Force-Time Record Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 31 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 described in 9.1.4 for test validity. If the rapid-force KQ is valid as KIc using a quasi-static yield strength value determined at a temperature at or above that of the rapid-force test, no further yield strength considerations is necessary. A10.7.3.1 If the test is invalid using the quasi-static yield strength, it will be necessary to conduct a supplementary tension test on the test material at the temperature and loading time of the rapid-force toughness test, with the time to reach the yield force in the tension test approximately equal to the time t defined in A10.7.2. A10.7.3.2 In the absence of rapid-force load sys values as defined in A10.7.3.1, the dynamic yield strength sYD of certain steels may be estimated using the following equation (34, 35): sYD 5 sYS 1 A 2B Tx · Log~2 · 107t! (A10.2) where: sYS = 0.2 % offset room temperature quasi-static yield strength, t = loading time in ms (see A10.7.2), and = temperature of rapid-force toughness test. Tx Units: For sYS in MPa, A = 1 198 860 and B = 187 MPa For sYS in ksi, A = 174 000 and B = 27.2 ksi For T in °F, Tx = (T + 460) For T in °K, Tx = 1.8(T) NOTE A10.4—The equation in A10.7.3.2 has been found useful only in estimating the low temperature dynamic yield strength of constructional steels having room temperature yield strengths below 483 MPa (70 ksi). A10.8 Report A10.8.1 The test report shall include the following additional information: A10.8.1.1 Test time (in milliseconds) written in ( ) after KQ or KIc. A10.8.1.2 Method by which sYD of A10.7.3 was determined. A10.8.1.3 Indications of ringing, before PQ is reached, in the force versus time or displacement versus time record. A10.9 Precision and Bias A10.9.1 Precision—Eighteen valid values of KIc (t) at −51°C (−60°F) have been reported (33), with sYD determined by extrapolation of dynamic tensile yield strength values obtained at strain rates from 0.01 s-1 to 1.0 s-1 at temperatures from room to −40°C (−40°F). No statistical analysis of the dynamic tensile yield strength data was made. The rapid-force, plane-strain fracture toughness tests represented standard bend SE(B) and compact C(T) specimens tested in three thicknesses by seven laboratories. Not all laboratories tested all thicknesses. Statistical tests for outliers and for the differences between means indicated that the data should be pooled. Considering all the valid data, the grand mean X = 61.14 MPa=m (55.64 ksi=in.), the standard deviation S = 8.68 MPa=m (7.90 ksi=in.) and the coefficient of variation = 14 % of the average. A10.9.2 Bias—There is no accepted “standard” value for the plane-strain fracture toughness of any material. In the absence of such a true value, any statement concerning bias is meaningless. REFERENCES (1) Brown, W. F., Jr., and Srawley, J. E., “Plane Strain Crack Toughness Testing of High Strength Metallic Materials,” ASTM STP 410, 1966. (2) Merkle, J. G., Wallin, K., and McCabe, D. E., “Technical Basis for an ASTM Standard on Determining the Reference Temperature To for Ferritic Steels in the Transition Range,” NUREG/CR-5504 (ORNL/ TM-13631), November 1998. (3) Srawley, J. E.. “Plane Strain Fracture Toughness,” Fracture, Vol 4, Ch. 2, p. 45–68. (4) Wessel, E. T., “State of the Art of the WOL Specimen for KIc Fracture Toughness Testing,” Engineering Fracture Mechanics, Vol 1, No. 1, January 1968. (5) Srawley, J. E., Jones, M. H., and Brown, W. F., Jr., “Determination of Plane Strain Fracture Toughness,” Materials Research and Standards, ASTM, Vol 7, No. 6, June 1967, p. 262. (6) Jones, M. H., and Brown, W. F., Jr. “The Influence of Crack Length and Thickness in Plane Strain Fracture Toughness Tests,” ASTM STP 463, 1970, p. 63. (7) Bray, G. H., “Literature Review on Use of Side Grooves in LinearElastic Fracture Toughness Testing: Supporting Document for E08.07 Ballot Item 6 (April 2006) Detailed references added Jan. 2007”. Contact Dr. Mark James. [email protected] (8) Fisher, D. M., and Repko, A. J., “Note on Inclination of Fatigue Cracks in Plane Strain Fracture Toughness Test Specimens,” Materials Research and Standards, ASTM, Vol 9, No. 4, April 1969. (9) Heyer, R. H., and McCabe, D. E., “Evaluation of a Test Method for Plane-Strain Fracture Toughness Using a Bend Specimen,” ASTM STP 463, 1970, p. 22. (10) McCabe, D. E., “Evaluation of the Compact Tension Specimen for Determining Plane-Strain Fracture Toughness of High Strength Materials,” Journal of Materials, Vol 7, No. 4, December 1972, p. 449. (11) Underwood, J. H., and Kendall, D. P., “Cooperative Plane Strain Fracture Toughness Tests with C-Shaped Specimens,” Journal of Testing and Evaluation, Vol 6, No. 5, September 1978, p. 296. (12) McCabe, D. E., “Evaluation of the Compact Tension Specimen for Plane Strain Fracture Toughness of High Strength Materials,” Journal of Materials, Vol 7, No. 4, December 1972, p. 449. (13) Orange, T. W., “Some Effects of Experimental Error in Fracture Testing,” Fracture Analysis, ASTM STP 560, 1974, pp. 122–133. (14) Fisher, D. M., Bubsey, R. T., and Srawley, J. E., “Design and Use of a Displacement Gage for Crack Extension Measurements,” NASA TN-D-3724, Nat. Aeronautics and Space Administration, 1966. (15) Baratta, F. I. and Fett, T., “The Effect of Load and Crack Misalignment on Stress Intensity Factors for Bend Type Fracture Toughness Specimens,” Journal of Testing and Evaluation, Vol 28, No. 2, March 2000, pp. 96-102. (16) Jones, M. H., Bubsey, R. T., and Brown, W. F., Jr., “Clevis Design for Compact Tension Specimens Used in KIc Testing,” Materials Research and Standards, ASTM, Vol 9, No. 5, May 1969. (17) Freese, C. E. and Baratta, F. I., “Single Edge-Crack Stress Intensity Factor Solutions,” Engineering Fracture Mechanics, Vol 73, 2006, pp. 616-625. Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 32 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E399 – 09´2 (18) Srawley, J. E., “Wide Range Stress Intensity Factor Expressions for ASTM E399 Standard Fracture Toughness Specimens,” International Journal of Fracture, Vol 12, June 1976, p. 475. (19) Tada, H., Paris, P. C., and Irwin, G. R., “ The Stress Analysis of Cracks Handbook,” Del Research Corporation, Hellertown, PA, 1973. (20) Wu, S. X., “Crack Length Calculation Formula for Three-Point Bend Specimens,” International Journal of Fracture, Vol 24, 1984, pp. R33–R35. (21) Newman, J. C., “Stress Analysis of Compact Specimens Including the Effects of Pin Loading,” ASTM STP 560, 1974, p. 105. (22) Kapp, J. A., “Improved Wide Range Expressions for Displacements and Inverse Displacements for Standard Fracture Mechanics Specimens,” Journal of Testing and Evaluation, JTEVA, Vol 19, No. 1, January 1991, pp. 45–54. (23) Underwood, J. H., Newman, J. C., Jr., and Seeley, R. R., “A Proposed Standard Round Compact Specimen for Plane Strain Fracture Toughness Testing,” Journal of Testing and Evaluation, Vol 8, No. 6, November 1980, p. 308–313. (24) Newman, J. C., Jr., “Stress Intensity Factors and Crack Opening Displacements for Round Compact Specimens,” International Journal of Fracture, Vol 17, No. 6, December 1981, pp. 567–578. (25) Kapp, J. A., Newman, J. C., Jr., and Underwood, J. H., “A Wide Range Stress Intensity Factor Expression for the C-Shaped Specimen,” Journal of Testing and Evaluation, Vol 8, No. 6, November 1980, pp. 314–317. (26) Underwood, J. H., “Proposed Standard Arc-Bend Chord-Support Fracture Toughness Specimens and K Expressions,” Journal of Testing and Evaluation, JTEVA, Vol 17, No. 4, July 1989, pp. 230–233. (27) Jones, M. H., Bubsey, R. T., and Brown, W. F. Jr., “Crack Toughness Evaluation of Hot Pressed and Forged Beryllium,” Journal of Testing and Evaluation, JTEVA, Vol 1, No. 2, March 1973, pp. 100–109. (28) Lemon, D. D., and Brown, W. F., Jr., “Fracture Toughness of Hot Pressed Be,” Journal of Testing and Evaluation, JTEVA, Vol 13, No. 2, March 1985, p. 152. (29) Conrad, H., and Sargent, G. A., “To Establish a Standard ASTM Method for Fracture Toughness Testing of Beryllium,” NASA Grant NSG3013, Oct. 1977, ASTM Research Report No. RR:E24-1005. (30) Shabbits, W. O., and Logsdon, W. A., “S-200 Grade Beryllium Fracture Toughness Properties,” Journal of Testing and Evaluation, JTEVA, Vol 1, No. 2, March 1973, pp. 110–118. (31) Conrad, H., Sargent, G. A., and Brown, W. F., Jr., “A Joint Fracture Toughness Evaluation of Hot Pressed Beryllium,” Beryllium Conference, The Royal Society, London, 1977, Paper 21. (32) Baratta, F. I., Private Communication, 21 Nov 1989. ASTM Research Report RR:E24-1015. (33) Shoemaker, A. K., and Seeley, R. R., “Summary Report of RoundRobin Testing by the ASTM Task Group E24.01.06 on Rapid Loading Plane-Strain Fracture Toughness KIc Testing,” Journal of Testing and Evaluation, JTEVA Vol 11, No. 4, July 1983 pp. 261–272. (34) Madison, R. B., and Irwin, G. R., “Dynamic Kc Testing of Structural Steel, ” Journal of the Structural Division, ASCE, Vol 100, No. ST 7, Proceedings paper 10653, July 1974, p. 1331. (35) Irwin, G. R., Krafft, J. M., Paris, P., and Wells, A. A., “Basic Aspects of Crack Growth and Fracture,” NRL Report 6598, Naval Research Laboratory, November 1967. (36) Petti, J. and Dodds, R. H., “Input on Side-Grooved Specimen Discussion for E399” Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign, Oct. 24, 2003. Contact Dr. Mark James. [email protected] ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below. This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585 (phone), 610-832-9555 (fax), or [email protected] (e-mail); or through the ASTM website (www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/ COPYRIGHT/). Copyright by ASTM Int'l (all rights reserved); Mon Mar 21 14:01:38 EDT 2011 33 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. Designation: E2248 – 09 Standard Test Method for Impact Testing of Miniaturized Charpy V-Notch Specimens1 This standard is issued under the fixed designation E2248; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval. 1. Scope 1.1 This test method describes notched-bar impact testing of metallic materials using Miniaturized Charpy V-Notch (MCVN) specimens and test apparatus. It provides: (a) a description of the apparatus, (b) requirements for inspection and calibration, (c) safety precautions, (d) sampling, (e) dimensions and preparation of specimens, (f) testing procedures, and (g) precision and bias. 1.2 This standard concerns Miniaturized Charpy V-Notch specimens, for which all linear dimensions, including length and notch depth, are reduced with respect to a type A standard impact test specimen in accordance with Test Methods E23. These are not the same as sub-size specimens, described in Annex A3 of Test Methods E23, for which length, notch angle and notch depth are the same as for the standard type A Charpy specimen. See also 1.5 below. 1.3 Comparison of the MCVN data with conventional Charpy V-Notch (CVN) data or application of the MCVN data, or both, to the evaluation of ferritic material behavior is the responsibility of the user of this test method and is not explicitly covered by this test method. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 This standard does not address testing of sub-size specimens as discussed in Test Methods E23. The reader should understand the distinction between miniature and subsize. Miniature specimens are shorter that sub-size specimens so that more tests can be conducted per unit volume of material. Moreover, miniature specimens are designed so that the stress fields which control fracture are similar to those of conventional Test Methods E23 specimens. 1.6 The MCVN test may be performed using a typical Test Methods E23 test machine with suitably modified anvils and striker or using a smaller capacity machine. 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro1 This test method is under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.07 on Impact Testing. Current edition approved April 1, 2009. Published April 2009. DOI: 10.1520/ E2248-09. priate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. Referenced Documents 2.1 ASTM Standards:2 A370 Test Methods and Definitions for Mechanical Testing of Steel Products E23 Test Methods for Notched Bar Impact Testing of Metallic Materials E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method E2298 Test Method for Instrumented Impact Testing of Metallic Materials 2.2 ISO Standards:3 ISO 148 Metallic materials -- Charpy pendulum impact test -- Part 1: Test method ISO 14556 Steel -- Charpy V-notch pendulum impact test -Instrumented test method 3. Summary of Test Method 3.1 The essential features of the MCVN impact test are: (a) a suitable miniature three point bend specimen, (b) anvils and supports on which the test specimen is placed to receive the blow of the moving mass, (c) a moving mass (striker) that has been released from a sufficient height to cause the mass to break the specimen placed in its path, (d) a device for determining the energy absorbed by the broken specimen, and optionally (e) instrumentation for measuring applied force as a function of time during specimen loading (refer to Test Method E2298). 3.2 The test consists of breaking the miniaturized specimen, notched in the middle, and supported at each end, with one blow from a swinging pendulum under conditions defined hereafter. 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [email protected]. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website. 3 Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:// www.iso.org. Copyright (C) ASTM International. 100 Barr Harbor Drive P.O. Box C-700 West Conshohocken, Pennsylvania 19428-2959, United States Copyright by ASTM Int'l (all rights reserved); Tue Mar 22 16:46:00 EDT 2011 1 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E2248 – 09 4. Significance and Use 4.1 There are cases where it is impractical or impossible to prepare conventional CVN specimens. MCVN specimens are an alternative approach for characterizing notched specimen impact behavior. Typical applications include MCVN specimens prepared from the broken halves of previously tested specimens, from thin product form material, or from material cut from in-service components. 4.2 This standard establishes the requirements for performing impact tests on MCVN specimens fabricated from metallic materials. Minimum requirements are given for measurement and recording equipment such that similar sensitivity and comparable measurements, as compared to conventional CVN tests, are achieved. The user should be aware that the transition region temperature dependence data obtained from MCVN specimens are not directly comparable to those obtained from full-size standard Charpy-V specimens and suitable correlation procedures have to be employed to obtain ductile-to-brittle transition temperature (DBTT) data equivalent to those obtained using CVN specimens. In all instances, correlations will have to be developed to relate upper shelf energy (USE) data from MCVN test to CVN comparable energy levels. Application of MCVN test data to the evaluation of ferritic material behavior is the responsibility of the user of this test method. MCVN test data should not be used directly to determine the lowest allowable operating temperature for an in-service material. The data must be interpreted within the framework of a fracture mechanics assessment. 4.3 While this Test Method treats the use of an instrumented striker as an option, the use of instrumentation in the impact test is recommended and is fully described in Test Method E2298. In order to establish the force-displacement diagram, it is necessary to measure the impact force as a function of time during contact of the striker with the specimen. The area under the force-displacement curve is a measure of absorbed energy. As an alternative, absorbed energy may be evaluated directly from machine dial reading. Whenever possible, an optical encoder shall be used in place of the machine dial because an encoder has better resolution than a dial. 5. Test Machine 5.1 The test shall be carried out with a pendulum-type impact testing machine which is (optionally) instrumented to determine force-time curves. The test machine shall have sufficient capacity to break the specimen in one blow while losing not more than 80 % of the initial potential energy. Provided energy measurements can be obtained with a resolution better than or equal to 0.1 J, the same test machine used for CVN testing may be used to test MCVN specimens. 5.2 The MCVN specimen has to be suitably supported so that the centerline of the specimen coincides with the center of strike of the pendulum. If the same machine used for CVN testing is used for MCVN specimens, refer to Appendix X3 of E23 for changing the specimen support height by manufacturing new supports or adding shims. 5.3 The impact velocity (tangential velocity) of the pendulum at the center of the strike shall not be less than 1 nor more than 6 m/s. NOTE 1—Impact velocities above 4 m/s are not advisable for instrumented MCVN tests, since excessive oscillations are then superimposed on the initial portion of the test diagram and errors in the evaluation of the force-displacement trace may occur. For the same reason (ease of interpretation of the instrumented curve), lower velocities are allowed for MCVN tests than required by E23 (not less than 3 m/s). 5.4 It is recommended that the scalability of the stress fields is maintained. This is accomplished by scaling the striker FIG. 1 Scaled 8 mm and 2 mm Strikers for Use in Miniaturized Charpy Impact Test Copyright by ASTM Int'l (all rights reserved); Tue Mar 22 16:46:00 EDT 2011 2 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E2248 – 09 radius, anvil radii, and the span of the anvils with respect to a specimen size that is proportional to the CVN specimen. Fig. 1 shows the dimensions of 8 and 2 mm strikers (3.86 mm and 0.96 mm) scaled for use with the nominal 1⁄2-scale MCVN (4.83 by 4.83 by 24.13 mm) specimen shown in Fig. 2. For both of these scaled strikers, the anvil radius is scaled to 0.48 6 0.025 mm, and the span is 19.3 6 0.025 mm. 5.5 A non-scaled 2 mm striker can be used to test the 4 by 3 by 27 mm MCVN specimen described in Annex D of ISO 14556. The anvil radius and span, in this case are 1 0+0.50 mm and 220+0.10 mm respectively. NOTE 2—This particular test is allowed because a substantial amount of data exists for this specimen and test geometry. This MCVN specimen is not proportional to the CVN specimen, so scaling is not appropriate. 5.6 The testing machine shall be a pendulum type of rigid construction. All general requirements for apparatus and calibration specified in Test Methods E23 shall be satisfied. 5.7 For instrumented force measurements using optional force measuring instrumentation, the requirements given in Test Method E2298 regarding striker instrumentation, data acquisition, and data analysis shall be satisfied. 6. Hazards 6.1 Safety precautions should be taken to protect personnel from electric shock, the swinging pendulum, flying broken specimens, and hazards associated with specimen warming and cooling media. See also 1.6. 7. Test Specimens 7.1 The recommended proportional specimen configuration is the square cross section notched bar shown in Fig. 2. The cross sectional dimension is slightly under 5 mm to enable machining from a previously tested CVN. Information on additional specimen geometries that have been successfully used is provided in Appendix X1. NOTE 3—In case MCVN specimens are extracted from broken CVN specimens of highly ductile materials, the user should ensure that the severe plastic deformation occurred during fracture of the CVN specimens does not affect the impact behavior of the miniaturized samples. 7.2 Microstructural considerations dictate that only V-notch specimens with cross sectional dimensions sufficient to ensure a representative volume of material is tested may be used. In order to satisfy this requirement, the size scale and mean separation distance of inhomogeneities that exist in the material must be known. The cross sectional dimension must be at least five times greater than the largest inhomogeneity. Posttest metallography may be performed in order to confirm that the requirement has been met. 7.3 Stress field similitude dictates that if the miniaturized specimens (such as the one shown in Fig. 2) do not satisfy the microstructural considerations, specimens with a larger cross section may be used. For the square cross section specimen in Fig. 2, all the remaining specimen dimensions (length, notch depth, etc.) shall be scaled by appropriate ratio with the conventional CVN dimensions. This has the advantage of standardization of approach and scalability of previously calculated finite element solutions. 7.4 Side grooving of the MCVN specimens (see also Appendix X2) is optional. Investigations (1) have shown that the use of side grooves on MCVN specimens provides a larger volume of material which is sampled at plane strain conditions. This results in less downward shift in temperature due to loss of constraint caused by miniaturization, and thereby reduces the need for correction factors to simulate CVN transitional fracture temperature dependence. 7.5 The choice of specimen depends on the application. NOTE 1—The notch root radius shall be 0.13 mm. NOTE 2—Permissible variations shall be as follows: notch length to edge radius of notch adjacent sides at notch depth cross section dimensions finish requirements 90° 6 2° 60.025 mm 90° 6 10 min 60.025 mm 60.025 mm 2 [im notched surface/opposite 4 \im other surfaces +0, −0.12 mm 60.12 mm 61° length of specimen centering of notch angle of notch FIG. 2 Miniaturized Charpy Impact Specimen Copyright by ASTM Int'l (all rights reserved); Tue Mar 22 16:46:00 EDT 2011 3 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E2248 – 09 NOTE 4—Although this test method specifically addresses impact tests performed on notched specimens, the use of unnotched samples may be advantageous when testing refractory metals or materials produced by powder metallurgy methods. For such materials, machining an accurate notch without producing significant damage is extremely difficult. The use of unnotched specimens, however, is outside the scope of this test method. 8. Test Procedure 8.1 The test procedure may be summarized as follows: the test specimen is heated/cooled in situ (that is, at the impact location) or it is removed from its cooling (or heating) medium, and positioned on the specimen supports; the pendulum is released with minimum vibration; and the absorbed energy is recorded from the machine dial or, preferably, from the optical encoder. For instrumented tests, the force-time curve is measured and evaluated to give the total absorbed energy. 8.2 The temperature of the specimen at impact must be within 62°C of the nominal test temperature. Due to the small size of the specimen, in tests below or above room temperature (RT), special attention must be devoted to temperature control within the above mentioned tolerance. It is recommended that in-situ heating/cooling be used. If a bath transfer system is used, it will be necessary to transfer the specimen to the supports and strike the specimen within a very short period of time (~ 1 s or less). If a thermal bath transfer system is not used, dummy specimens (with internal thermocouples) or test specimens (with surface thermocouples) shall be used to demonstrate that the 62°C requirement has been met. If in-situ heating/cooling is used, dummy specimens (with internal thermocouples) or test specimens (with surface thermocouples) shall be used to calibrate the system and to demonstrate that the 62°C requirement has been met. 8.3 The specimen shall be placed on the supports against the anvils to ensure that the notch is centered to within 0.25 mm. 9. Lateral Expansion and Percent Shear Determination 9.1 The measurement of lateral expansion shall satisfy the requirements of Test Methods E23. The uncertainty of the measurement shall be determined by using precision machined reference blocks. 9.2 The fracture appearance, characterized as percent shear area, may be measured directly or determined using a correlation of characteristic values (see 9.2.2). 9.2.1 Direct measurement of fracture appearance shall satisfy the requirements of Test Methods E23. 9.2.2 Fracture Appearance Correlation—The equations described in Test Method E2298 may be used to estimate the shear fracture area. These equations relate characteristic force measurements with the percentage of shear fracture area. The applicability and accuracy of the correlation for a particular material shall be demonstrated. 10. Inspection, Verification, and Preparation of Apparatus 10.1 Machine inspection and verification shall be performed in accordance with the requirements of this test method, Test Methods E23, and Test Method E2298 as appropriate. 10.2 In cases where the MCVN specimens are tested on a large capacity Test Methods E23 test machine, the test machine shall be indirectly verified using CVN verification specimens in accordance with the requirements of Test Methods E23. In particular, the anvils and striker for CVN specimens shall be used to verify the test machine. MCVN anvils and striker shall then be put on the machine and the machine shall be further checked by testing MCVN specimens which are prepared from a material with a microstructure that produces small scatter in the fracture test results and/or for which a large experimental database is available (such as round-robin results, see for example references (1, 2, 3)). 10.3 MCVN test machines of small capacity, which are not capable of testing CVN verification specimens, shall be checked by testing MCVN specimens which are prepared from a material with a microstructure that produces small scatter in the fracture test results and/or for which a large experimental database is available (such as round-robin results, see for example references (1, 2, 3)). In the case of materials with a microstructure that produces small scatter in the fracture test results, it is not possible to compare MVCN results with known certified values. In such cases, it is recommended that a large batch of test specimens be prepared and used to establish the mean and standard deviation at various energy levels. The batch of test specimens can be used in the future to perform yearly test machine verification and to verify the performance of other MCVN test machines. 10.4 Prior to testing a group of specimens, and before a specimen is placed in position to be tested, check the machine by a free swing of the pendulum. With the dial indicator (if used) at the maximum energy position, a free swing of the pendulum shall indicate zero energy within at least 0.1 J on machines reading directly in energy, and which are compensated for frictional losses. On machines using optical encoders, the indicated values, when converted to energy, shall be compensated for frictional losses and the free swing of the pendulum shall indicate zero energy within 60.1 J. 10.5 For instrumented testing, the calibration and verification procedures of Test Method E2298 shall be satisfied. 11. Report 11.1 For all tests, report the following information: 11.1.1 Specimen type and dimensions, 11.1.2 Test machine characteristics including anvil spacing, anvil radius, span, and striker geometry, 11.1.3 Test temperature of specimen and method of heating or cooling, and 11.1.4 Energy absorbed as measured by dial or optical encoder. 11.2 Optional variables which may be reported include: 11.2.1 Lateral expansion, 11.2.2 Fracture appearance (shear), 11.2.3 Specimen orientation, and 11.2.4 Specimen location within the plate or weld. 11.3 For instrumented tests, additional information in accordance with Test Method E2298 shall be reported. 12. Precision and Bias 12.1 Precision—MCVN impact data from two interlaboratory studies have been analyzed in accordance with Practice E691 in order to establish the precision of this Test Method. Copyright by ASTM Int'l (all rights reserved); Tue Mar 22 16:46:00 EDT 2011 4 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E2248 – 09 The terms repeatability limit and reproducibility limit are used as specified in Practice E177. 12.1.1 An interlaboratory study (1) was conducted using miniaturized Charpy V-notch specimens with square cross section (Fig. 2) of A533B Cl.1 (tested at room temperature and 150°C) and of two reference materials produced by the National Institute of Standards and Technology, Boulder CO (low energy and high energy). The ILS was conducted in accordance with Practice E691 in six laboratories, each one obtaining up to six test results for the absorbed energy measured by the machine dial or encoder (Table 1). See ASTM Research Report No.E28-1039.4 12.1.2 Another interlaboratory study (2, 3) of characteristic instrumented impact forces, displacements an d energies was conducted using KLST miniaturized Charpy V-notch speci4 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:E28-1039. TABLE 1 Absorbed energy (J) from MCVN specimens (2) Material Average A553B RT A533B 150°C 4340 (low en) 4340 (high en) 11.09 10.94 10.92 10.93 Repeatability Reproducibility Repeatability Reproducibility Standard Standard Limit Limit Deviation Deviation 0.40 0.36 0.36 0.23 0.40 0.40 0.38 0.34 1.13 1.00 1.00 0.64 1.13 1.11 1.07 0.95 mens with 334mm rectangular cross section (see Appendix X1) of A533B Cl.1. The ILS was conducted in accordance with Practice E691 in thirteen laboratories with fourteen test machines, each one obtaining up to five test results for the absorbed energy (Table 2). See ASTM Research Report No. E28-1037.5 12.2 Bias—Bias cannot be defined for MCVN absorbed energy. The physical simplicity of the pendulum design is complicated by complex energy loss mechanisms within the machine and the specimen. Therefore, there is no absolute standard to which the measured values can be compared. 13. Keywords 13.1 fracture appearance; impact test; instrumented impact test; lateral expansion; miniaturized Charpy test; notched specimens; pendulum machine 5 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:E28-1037. TABLE 2 Absorbed energy (J) from MCVN specimens of A533B cl. 1 (2, 3) Average Repeatability Standard Deviation Reproducibility Standard Deviation Repeatability Limit Reproducibility Limit 8.22 0.43 0.71 1.19 1.98 APPENDIXES (Nonmandatory Information) X1. ALTERNATIVE MCVN SPECIMEN CONFIGURATIONS X1.1 MCVN specimen described in Annex D of ISO 14556—This 4 3 3 3 27 mm3 specimen has been used extensively in Europe (2, 3). We refer the user to Annex D of ISO 14556 for details of the specimen geometry. X2. SIDE GROOVED MINIATURE CHARPY V-NOTCH SPECIMENS X2.1 Side Grooved Miniature Charpy V-notch Specimens: X2.1.1 This test method recommends the use of a proportional specimen with a square cross section, like that shown in Fig. 2. A square cross section side grooved specimen can also be used. X2.1.2 The use of the side grooves on MCVN specimens will provide a larger volume of material which is sampled in plane strain conditions. This results in less downward shift in temperature due to loss of constraint as a result of miniaturization, and thereby reduces the need for correction factors to simulate CVN transitional fracture temperature dependence. The choice of specimen depends on the application and it is important to note that some side grooved specimens and test procedures associated with them are patented technologies (4). Copyright by ASTM Int'l (all rights reserved); Tue Mar 22 16:46:00 EDT 2011 5 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. E2248 – 09 REFERENCES (1) Manahan, M. P., Sr., Martin F. J., and Stonesifer, R. B., “Results of the ASTM Instrumented/Miniaturized Round Robin Test Program”, Pendulum Impact Testing: A Century of Progress, ASTM STP 1380, T. A. Siewert and M. P. Manahan, Sr.,Eds., American Society for Testing and Materials, West Conshohocken, PA, 1999. (2) Lucon, E., 9Round-Robin on Instrumented Impact Testing of Sub Size Charpy-V Specimens: Results of Phase 19, ESIS TC5, Final Report, 2 April 1998. (3) Lucon, E., 9European Activity on Instrumented Impact Testing of Subsize Charpy V-Notch Specimens (ESIS TC5)9, Pendulum Impact Testing: A Century of Progress, ASTM STP 1380, T. A. Siewert, and M. P. Manahan, Sr., Eds., American Society for Testing and Materials, West Conshohocken, PA, 1999, p. 242-252. (4) United States Patent numbers 4,864,867 and 5,165,287, M.P. Manahan inventor Battelle Development Corporation assignee, filed 1988. ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below. This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at 610-832-9585 (phone), 610-832-9555 (fax), or [email protected] (e-mail); or through the ASTM website (www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/ COPYRIGHT/). Copyright by ASTM Int'l (all rights reserved); Tue Mar 22 16:46:00 EDT 2011 6 Downloaded/printed by University of Washington pursuant to License Agreement. No further reproductions authorized. 8842A Instruction Manual 3. Allow the displayed reading to settle. 4. Press the OFFSET button. 5. Remove the resistor. 6. Proceed with the desired measurement. Example: Measure a 1.5V source with 1 M! source impedance, correcting for input bias current. 1. Connect a 1 M! resistor between the INPUT HI and INPUT LO terminals. 2. Select the VDC function and the 2V range. 3. Allow the display to settle. 4. Press OFFSET. (This zeroes the input bias current error.) 5. Remove the 1 M! resistor. 6. Measure the voltage of the circuit under test. Note that this procedure does not correct for circuit loading error. Also note that if input bias current error is not corrected for, it may be added to the circuit loading error. 4-5. RESISTANCE MEASUREMENT The 8842A allows you to measure resistance in both 2-wire and 4-wire configurations. Each has its benefits. 4-6. 2-Wire Ohms Two-Wire ohms measurements are simple to set up and yield good results for most measurement conditions. Measurements are made as shown in Figure 4-3. An internal current source (the "ohms current source") passes a known test current (Itest) through the resistance being tested (Runknown). The 8842A measures the voltage drop across Runknown, calculates Runknown using Ohm’s law (Runknown = Vtest/Itest), and displays the result. f4-03.wmf Figure 4-3. Wire Ohms Measurement 4-4 Measurement Tutorial RESISTANCE MEASUREMENT 4 The test current and full-scale voltage for each resistance range are shown in Table 4-1. Since the HI INPUT test lead is positive with respect to the LO INPUT lead, these test leads are not interchangeable when a semiconductor device is being measured. 4-7. Correcting for Test Lead Resistance in 2-Wire Ohms In 2-wire ohms, the resistance of the test leads can introduce error when measuring low resistances. Typical test leads may add as much as 0.5Q to 2-wire ohms readings. With the 8842A, it is easy to correct for this error using the OFFSET button: 1. Select the 2-wire ohms function. 2. Touch the test leads together. The 8842A should indicate the resistance of the test leads. 3. With the test leads still touching, press the OFFSET button.The 8842A should read 0!. 4-8. 4-Wire Ohms Four-Wire ohms measurements provide the highest accuracy for low resistance measurements. The 4-wire configuration automatically corrects for both test lead resistance and contact resistance. Contact resistance (the resistance between the test probe tips and the circuit being tested) is unpredictable, and therefore cannot be reliably corrected with a fixed offset. Four-Wire ohms measurements are especially important when using long test leads. In a typical automated test system, for example, the test leads could be connected through four or five switching relays, each with 2! of resistance! NOTE Instability of the test lead’s resistance can cause significant error on low ohms ranges, particularly on the 20! and 200! ranges. Therefore, only 4wire ohms measurement is permitted in the 20! range. The 8842A makes 4-wire ohms measurements as shown in Figure 4-4. The HI and LO INPUT leads apply a known, internal current source to the unknown resistance, just as in 2-wire ohms. (See Table 4-1.) However, the voltage drop across the unknown resistance is measured with the SENSE leads rather than the INPUT leads. Since the current flow in the SENSE leads is negligible, the error caused by the voltage drop across the leads is also negligible. 4-5 8842A Instruction Manual f4-04.wmf Figure 4-4. Wire Ohms Measurement Table 4-1. Ohms Test Current 4-6 RANGE TEST CURRENT FULL SCALE VOLTAGE 20! 1 mA 0.02V 200! 1 mA 0.2V 2 k! 1 mA 2.0V 20 k! 100 µA 2.0V 200 k! 10 µA 2.0V 2000 k! 5 µA 10.0V 20 M! 500 nA 10.0V Measurement Tutorial RESISTANCE MEASUREMENT 4 NOTE ! and 20 M ! ranges of 4-wire ohms, the voltage across the In the 2 M unknown resistance is sensed between the HI SENSE and LO INPUT terminals. Accuracy is not affected as long as the resistance of the LO INPUT lead is less than 10! in the 2 M! range, and less than 100! in the 20 M! range. 4-9. Applications of the Ohms Functions The 2-wire and 4-wire ohms functions can be used for a variety of purposes in addition to measuring resistance, as the following applications show. 4-10. TESTING DIODES The 2-wire ohms function can also be used to test diodes. 1. Select the 2-wire ohms function and the 2 k! range. 2. Measure the resistance of the diode. If the diode is good, when forward-biased it will measure about 0.6 k! to 0.7 k! for silicon (0.25 k! to 0.3 k! for germanium), and when reverse-biased it will cause the 8842A to indicate overrange. (The forwardbiased reading depends upon the range used.) The 2 k! range is used because its 1 mA test current provides a typical operating point, and its 2V full-scale voltage is sufficient to turn on most diodes (even two diodes in series). 4-11. TESTING ELECTROLYTIC CAPACITORS The 2-wire ohms function can also give a rough test of an electrolytic capacitor’s leakage and dielectric absorption. This test works well for capacitors 0.5 µF and larger. 1. Select the 2-wire ohms function, the 2 k! range, and the medium reading rate. 2. Connect the test leads to the capacitor (with the INPUT HI lead to the + lead and the INPUT LO lead to the - lead). The 8842A attempts to charge it to the open-circuit voltage of the 2 k! range (about 6V). 3. Disconnect the + test lead. 4. To test for leakage, select the VDC function and the 20V range (leave the 8842A in the medium reading rate), and measure the voltage that was stored on the capacitor during step 2. a. If the capacitor is good, the voltage across the capacitor will be about 6V, and will be relatively stable. b. If the capacitor is leaky, the voltage across the capacitor will be much less than 6V, and the voltage will be decreasing. The rate of change depends on how leaky the capacitor is. c. With some electrolytic capacitors, the reading will increase. This usually indicates the capacitor is defective. 5. To test the capacitor’s dielectric absorption, briefly short the capacitor’s leads together and then measure the voltage across the capacitor. a. If the dielectric is good (i.e., has low dielectric absorption), the voltage across the capacitor will be nearly zero volts. b. If the dielectric is poor (i.e., has high dielectric absorption), the voltage across the capacitor will be significantly above zero. 4-7 8842A Instruction Manual 4-12. A PRECISION CURRENT SOURCE The ohms current source (the internal current source used in the ohms functions) makes a useful troubleshooting tool in itself. It has excellent linearity and temperature stability. Its compliance voltage is typically 5V in the lower five ohms ranges, and 12V in the upper two ohms ranges. The inputs are protected against accidental applications of voltage up to 300V rms. To use the ohms current source, connect the test leads to the HI and LO INPUTS, and select either the 2-wire or 4-wire ohms function. Press the range buttons to select any of the current levels shown in Table 4-1. The ohms current source can be used to troubleshoot circuits by injecting current into selected nodes, forcing the circuits to be in a specific test state. For example, the ohms current source can be used to set or modify the bias of amplifier circuits. The current level can be changed simply by changing range. The ohms current source can also be used to test mA or µA panel meters. The accuracy of the current source is more than enough to verify panel meters, whose accuracy is typically 1% to 5%. To test an analog panel meter, simply connect the current source across the meter movement (as though measuring its resistance). A 1 mA meter should show full scale when the ohms function is set on the 2 k! range. The same technique also works with digital panel meters. 4-13. DC CURRENT MEASUREMENT To get the best accuracy using the mA DC function, it is important to understand the concept of burden voltage error. When a meter is placed in series with a circuit to measure current, error can be caused by the small voltage drop across the meter (in this case, across the protective fuses and current shunt). This voltage drop is called the burden voltage, and it is highest for fullscale measurements. The full-scale burden voltage for the 8842A is typically less than 1V. The burden voltage can present a significant error if the current source being measured is unregulated (i.e., not a true current source) and if the resistance of the fuse and shunt is a significant part of the source resistance. If burden voltage does present a significant error, the percentage of error can be calculated and corrected for using the formulas in Figure 45. 4-8 MSDS # 09912K REV..# 0811-B Replaces 10/27/2005 MATERIAL SAFETY DATA SHEET Page 1 I. PRODUCT IDENTIFICATION TRADE NAME: 9912K EMERGENCY PHONE NUMBER : "FOR CHEMICAL EMERGENCY" Silver paste MANUFACTURER: ElectroScience Laboratories, Inc. BY: John Moore 416 E. Church Road , King of Prussia, PA 19406 Phone: (610) 2728000 DATE PREPARED: Nov 18, 2008 TYPE: Spill, Leak, Fire,Exposure or Accident Call CHEMTREC R Day or Night (800)4249300 International (call collect):7035273887 II. HAZARDOUS INGREDIENTS CHEMICAL NAMES CAS NUMBERS EXPOSURE LIMITS IN AIR ACGIH OSHA PEL Silver 7440-22-04 0.1 MG/M3 3-hydroxy-2,2,4-trimethylpentyl Isobutyrate 25265-77-4 NONE ESTABLISHED 0.01 OTHER (SPECIFY) The specific chemical identity is withheld as a Trade Secret. III. PHYSICAL PROPERTIES * Physical Properties for primary solvent only.if present. * VAPOR DENSITY (air=1): 7.45 MELTING POINT OR RANGE, °C: N/A * SPECIFIC GRAVITY: 0.95 * BOILING POINT OR RANGE, °C: 255 * EVAPORATION RATE (Butyl Acetate=1): * SOLUBILITY IN WATER: Insoluble * VAPOR PRESSURE, mm Hg: 0.002 Metallic colored paste with a mild odor. APPEARANCE AND ODOR: 1 @ 87C IV. FIRE AND EXPLOSION * FLASH POINT, °C: 120 * FLAMMABLE LIMITS IN AIR, VOLUME % * AUTOIGNITION TEMPERATURE, °C: 393 LOWER (LEL): 0.52 @149C UPPER (LEL): 4.24 @201C Foam, CO2, Dry Chemical. FIRE EXTINGUISHING MATERIALS: Wear selfcontained breathing apparatus and protective clothing to prevent contact with skin and eyes. Do not use water to extinguish flame. None known to ESL. SPECIAL FIREFIGHTING PROCEDURE: UNUSUAL FIRE AND EXPLOSION HAZARDS: V. HEALTH HAZARD INFORMATION SYMPTOMS OF OVEREXPOSURE: INHALED: H.M.I.S. Flammability 1 Health 2 Reactivity 1 Headache. CONTACT WITH SKIN OR EYES: ABSORBED THROUGH SKIN: SWALLOWED: May cause irritation to eyes, skin & mucous membranes. None known to ESL. May cause nausea and vomiting, diarrhea, spasms, abdominal pain, toxic, see below HEALTH EFFECTS OR RISKS May cause headache, nausea, vomiting & irritation to eyes, skin and mucous membranes. ACUTE: CHRONIC: Personal Protection May cause eczema, gastroenteritis. FIRST AID EMERGENCY PROCEDURES: Immediately flush with water for 15 minutes; call physician. EYE CONTACT: SKIN CONTACT: Wash thoroughly with soap and large amounts of water. Remove from exposure, treat symptomatically. INHALED: SWALLOWED: Induce vomiting; call physician. G MATERIAL SAFETY DATA SHEET MSDS # 09912K SUSPECTED CANCER AGENT? NO YES Page 2 This product's ingredients are not found in the lists below. FEDERAL OSHA MEDICAL CONDITIONS AGGRAVATED BY EXPOSURE: NTP IARC Allergies and Asthma. VI. REACTIVITY DATA STABLE STABILITY: UNSTABLE Contact with eyes, skin and clothing. CONDITIONS TO AVOID: None foreseeable for normal use. INCOMPATABILITY: Carbon Monoxide, Carbon Dioxide, smokes when burned. HAZARDOUS DECOMPOSITION PRODUCTS (including combustion products): Will not occur. HAZARDOUS POLMERIZATION: VII. SPILL, LEAK AND DISPOSAL PROCEDURES Avoid prolonged contact with skin and prolonged breathing of vapors. Collect spills with absorbent materials. Residue may be washed with soap and water. Prevent runoff from entering drains. PREPARING WASTES FOR DISPOSAL: Disposal method must comply with federal, state and local regulations. SPILL RESPONSE PROCEDURES: VIII. SPECIAL HANDLING INFORMATION VENTILATION AND ENGINEERING CONTROLS: Good general ventilation. 10 air changes per hour. When used with adequate ventilation, none should be needed. RESPIRATORY PROTECTION: EYE PROTECTION: NIOSH approved safety glasses. GLOVES: Rubber or Latex. OTHER CLOTHING AND EQUIPMENT: All equipment should be well vented to prevent decomposition products and vapors from accumulating. WORK PRACTICES, HYGENIC Good industrial hygiene practices should be followed to prevent skin and eye contact and PRACTICES: inhalation of vapors. Wash hands thoroughly after handling and before eating and smoking. Keep away from heat, sparks and open flames. OTHER HANDLING AND STORAGE REQUIREMENTS: PROTECTIVE MEASURES DURING MAINTENANCE: All of the above. IX. OTHER REGULATORY INFORMATION This product contains the following chemicals subject to the reporting requirements of Section 313 of the Emergency Planning and Community RightToKnow Act of 1986 ( 40 CFR 372). TOXIC CHEMICAL Silver Transportation non-regulated CAS NUMBERS % CONCENTRATION (Upper Limit) 90 74402204 Volatile Organic Content TSCA Inventory and Canadian DSL: All ingredients listed unless exempt. ? g/l NOTICE FROM ESL, INC. The information contained in this MSDS is believed to be accurate and represents the best information currently available to ESL. The data in this MSDS relates only to the specific product(s) designed herein and does not relate to its use in combination with any other material or process. MSDS # 09912K FL REV..# 0706-NEW Replaces MATERIAL SAFETY DATA SHEET Page 1 I. PRODUCT IDENTIFICATION TRADE NAME: 9912K FL EMERGENCY PHONE NUMBER : "FOR CHEMICAL EMERGENCY" TYPE: ElectroScience Laboratories, Inc. 416 E. Church Road , King of Prussia, PA 19406 Phone: (610) 2728000 DATE PREPARED: Jun 7, 2007 Spill, Leak, Fire,Exposure or Accident Call CHEMTREC R Day or Night (800)4249300 International (call collect):7035273887 II. HAZARDOUS INGREDIENTS MANUFACTURER: BY: John Moore CHEMICAL NAMES CAS NUMBERS EXPOSURE LIMITS IN AIR ACGIH OSHA PEL Silver 7440-22-04 0.1 MG/M3 0.01 Terpineol 8000-41-7 None Established OTHER (SPECIFY) The specific chemical identity is withheld as a Trade Secret. III. PHYSICAL PROPERTIES * Physical Properties for primary solvent only.if present. * VAPOR DENSITY (air=1): 6.5 MELTING POINT OR RANGE, °C: 10 * SPECIFIC GRAVITY: 0.94 * BOILING POINT OR RANGE, °C: 214 255 * EVAPORATION RATE (Butyl Acetate=1): * SOLUBILITY IN WATER: @ 20ÝC Negligible * VAPOR PRESSURE, mm Hg: APPEARANCE AND ODOR: < 1 * FLASH POINT, °C: 88 Cleveland Open Cup * AUTOIGNITION TEMPERATURE, °C: 1.0 Metallic colored paste with a mild odor. IV. FIRE AND EXPLOSION * FLAMMABLE LIMITS IN AIR, VOLUME % Not determined LOWER (LEL): UPPER (LEL): N/A N/A Water Spray, Foam, CO2, Dry Chemical. FIRE EXTINGUISHING MATERIALS: Wear selfcontained breathing apparatus and protective clothing to prevent contact with skin and eyes. May selfignite at upper explosion limit conditions. SPECIAL FIREFIGHTING PROCEDURE: UNUSUAL FIRE AND EXPLOSION HAZARDS: V. HEALTH HAZARD INFORMATION SYMPTOMS OF OVEREXPOSURE: INHALED: H.M.I.S. Flammability 2 Health 1 Reactivity 1 Personal Protection Headache, coughing CONTACT WITH SKIN OR EYES: ABSORBED THROUGH SKIN: May cause irritation to eyes, skin & mucous membranes. Low hazard per usual industrial handling. May cause severe gastrointestinal tract irritation. Aspiration may cause pulmonary edema ad chemical pneumonitis. HEALTH EFFECTS OR RISKS May cause headache, nausea, vomiting & irritation to eyes, skin and mucous membranes. ACUTE: SWALLOWED: CHRONIC: May cause eczema, gastroenteritis. FIRST AID EMERGENCY PROCEDURES: Immediately flush with water for 15 minutes; call physician. EYE CONTACT: SKIN CONTACT: Wash thoroughly with soap and large amounts of water. Move to fresh air immediately. INHALED: SWALLOWED: Do NOT induce vomiting! Call a physician; give lots of water. G MATERIAL SAFETY DATA SHEET MSDS # 09912K FL SUSPECTED CANCER AGENT? NO YES Page 2 This product's ingredients are not found in the lists below. FEDERAL OSHA MEDICAL CONDITIONS AGGRAVATED BY EXPOSURE: NTP IARC Allergies and Asthma. VI. REACTIVITY DATA STABLE STABILITY: UNSTABLE Contact with eyes, skin and clothing. CONDITIONS TO AVOID: None foreseeable for normal use. INCOMPATABILITY: Carbon Monoxide, Carbon Dioxide, smokes when burned. HAZARDOUS DECOMPOSITION PRODUCTS (including combustion products): Will not occur. HAZARDOUS POLMERIZATION: VII. SPILL, LEAK AND DISPOSAL PROCEDURES Avoid prolonged contact with skin and prolonged breathing of vapors. Collect spills with absorbent materials. Residue may be washed with soap and water. Prevent runoff from entering drains. PREPARING WASTES FOR DISPOSAL: Disposal method must comply with federal, state and local regulations. SPILL RESPONSE PROCEDURES: VIII. SPECIAL HANDLING INFORMATION VENTILATION AND ENGINEERING CONTROLS: Good general ventilation. 10 air changes per hour. When used with adequate ventilation, none should be needed. RESPIRATORY PROTECTION: EYE PROTECTION: NIOSH approved safety glasses. GLOVES: Rubber or Latex. OTHER CLOTHING AND EQUIPMENT: All equipment should be well vented to prevent decomposition products and vapors from accumulating. WORK PRACTICES, HYGENIC Good industrial hygiene practices should be followed to prevent skin and eye contact and PRACTICES: inhalation of vapors. Wash hands thoroughly after handling and before eating and smoking. Keep away from heat, sparks and open flames. OTHER HANDLING AND STORAGE REQUIREMENTS: PROTECTIVE MEASURES DURING MAINTENANCE: All of the above. IX. OTHER REGULATORY INFORMATION This product contains the following chemicals subject to the reporting requirements of Section 313 of the Emergency Planning and Community RightToKnow Act of 1986 ( 40 CFR 372). TOXIC CHEMICAL Silver Transportation non-regulated CAS NUMBERS % CONCENTRATION (Upper Limit) 90 74402204 Volatile Organic Content TSCA Inventory and Canadian DSL: All ingredients listed unless exempt. ? g/l NOTICE FROM ESL, INC. The information contained in this MSDS is believed to be accurate and represents the best information currently available to ESL. The data in this MSDS relates only to the specific product(s) designed herein and does not relate to its use in combination with any other material or process. MSDS # 02602-310A REV..# 0510-A Replaces 9/25/2003 MATERIAL SAFETY DATA SHEET Page 1 I. PRODUCT IDENTIFICATION TRADE NAME: R-310-A, R-311-A, R-312-A EMERGENCY PHONE NUMBER : "FOR CHEMICAL EMERGENCY" Resistor TYPE: Electro-Science Laboratories, Inc. 416 E. Church Road , King of Prussia, PA 19406 Phone: (610) 272-8000 DATE PREPARED: 10/27/05 Spill, Leak, Fire,Exposure or Accident Call CHEMTREC R - Day or Night (800)-424-9300 International (call collect):703-527-3887 II. HAZARDOUS INGREDIENTS MANUFACTURER: BY: Robert Fox CHEMICAL NAMES CAS NUMBERS EXPOSURE LIMITS IN AIR ACGIH OSHA PEL Glass containing lead 7439-92-1 0.05 MG/M3 0.05 Silver 7440-22-04 0.1 MG/M3 0.01 Cadmium compound in glass 7440-43-9 0.05 MG/M3 0.005 3-hydroxy-2,2,4-trimethylpentyl Isobutyrate 25265-77-4 NONE ESTABLISHED OTHER (SPECIFY) - The specific chemical identity is withheld as a Trade Secret. III. PHYSICAL PROPERTIES * Physical Properties for primary solvent only.if present. * VAPOR DENSITY (air=1): * SPECIFIC GRAVITY: 7.45 0.95 N/A * BOILING POINT OR RANGE, °C: 255 * EVAPORATION RATE (Butyl Acetate=1): * SOLUBILITY IN WATER: Insoluble * VAPOR PRESSURE, mm Hg: MELTING POINT OR RANGE, °C: 0.002 Paste with a mild odor. APPEARANCE AND ODOR: 1 @ 87C IV. FIRE AND EXPLOSION * FLASH POINT, °C: 120 * FLAMMABLE LIMITS IN AIR, VOLUME % * AUTOIGNITION TEMPERATURE, °C: 393 LOWER (LEL): 0.52 @149C UPPER (LEL): 4.24 @201C Foam, CO2, Dry Chemical. FIRE EXTINGUISHING MATERIALS: SPECIAL FIREFIGHTING PROCEDURE: UNUSUAL FIRE AND EXPLOSION HAZARDS: Wear self-contained breathing apparatus and protective clothing to prevent contact with skin and eyes. Do not use water to extinguish flame. None known to ESL. V. HEALTH HAZARD INFORMATION SYMPTOMS OF OVEREXPOSURE: INHALED: Flammability 1 Health 2 Reactivity 1 Personal Protection G Headache and irritation. CONTACT WITH SKIN OR EYES: ABSORBED THROUGH SKIN: SWALLOWED: H.M.I.S. May cause irritation and discoloration of eyes, skin & mucous membranes. None known to ESL. May cause nausea and vomiting, diarrhea, spasms, abdominal pain, toxic, see below HEALTH EFFECTS OR RISKS May cause headache, nausea, vomiting & irritation to eyes, skin and mucous membranes. ACUTE: May cause eczema, gastroenteritis. Lead may damage liver, kidney, blood, nervous and reproductive systems and is a suspected carcinogen. FIRST AID EMERGENCY PROCEDURES: Immediately flush with water for 15 minutes; call physician. EYE CONTACT: SKIN CONTACT: Wash thoroughly with soap and large amounts of water. Move to fresh air immediately. INHALED: SWALLOWED: Induce vomiting; call physician. CHRONIC: MATERIAL SAFETY DATA SHEET MSDS # 02602-310A SUSPECTED CANCER AGENT? NO YES Page 2 This product's ingredients are not found in the lists below. FEDERAL OSHA MEDICAL CONDITIONS AGGRAVATED BY EXPOSURE: NTP IARC Allergies and Asthma. VI. REACTIVITY DATA STABLE STABILITY: UNSTABLE Contact with eyes, skin and clothing. CONDITIONS TO AVOID: None foreseeable for normal use. INCOMPATABILITY: Carbon Monoxide, Carbon Dioxide, smokes when burned. HAZARDOUS DECOMPOSITION PRODUCTS (including combustion products): Will not occur. HAZARDOUS POLMERIZATION: VII. SPILL, LEAK AND DISPOSAL PROCEDURES Avoid prolonged contact with skin and prolonged breathing of vapors. Collect spills with absorbent materials. Residue may be washed with soap and water. Prevent run-off from entering drains. PREPARING WASTES FOR DISPOSAL: Disposal method must comply with federal, state and local regulations. SPILL RESPONSE PROCEDURES: VIII. SPECIAL HANDLING INFORMATION VENTILATION AND ENGINEERING CONTROLS: Good general ventilation. 10 air changes per hour. When used with adequate ventilation, none should be needed. RESPIRATORY PROTECTION: EYE PROTECTION: NIOSH approved safety glasses. GLOVES: Rubber or Latex. OTHER CLOTHING AND EQUIPMENT: All equipment should be well vented to prevent decomposition products and vapors from accumulating. WORK PRACTICES, HYGENIC Good industrial hygiene practices should be followed to prevent skin and eye contact and PRACTICES: inhalation of vapors. Wash hands thoroughly after handling and before eating and smoking. Keep away from heat, sparks and open flames. OTHER HANDLING AND STORAGE REQUIREMENTS: PROTECTIVE MEASURES DURING MAINTENANCE: All of the above. IX. OTHER REGULATORY INFORMATION This product contains the following chemicals subject to the reporting requirements of Section 313 of the Emergency Planning and Community Right-To-Know Act of 1986 ( 40 CFR 372). TOXIC CHEMICAL Glass containing Lead Transition metal compounds silver Cadmium compound Transportation non-regulated CAS NUMBERS % CONCENTRATION (Upper Limit) 35 10 35 2 7440-22-04 Volatile Organic Content TSCA Inventory and Canadian DSL: All ingredients listed unless exempt. ? g/l NOTICE FROM ESL, INC. The information contained in this MSDS is believed to be accurate and represents the best information currently available to ESL. The data in this MSDS relates only to the specific product(s) designed herein and does not relate to its use in combination with any other material or process. ESL ELECTROSCIENCE CERAMIC TAPES & THICK-FILM MATERIALS 416 EAST CHURCH ROAD KING OF PRUSSIA, PA 19406-2625, U.S.A T: 610-272-8000 F: 610-272-6759 www.electroscience.com 9912-K CERMET SILVER CONDUCTOR Lead, Cadmium and Nickel-Free* ESL 9912-K is a silver conductor having a wide range of applications, for example chip resistors, consumer hybrids, potentiometers and heaters. Due to the wide firing temperature range, this conductor may be processed onto a variety of substrates including glass, Porcelain Enamelled Steel (PES), alumina and special ceramics. Additionally, 9912-K also exhibits excellent gold wire bondability. PASTE DATA Rheology: Thixotropic, screen-printable paste Viscosity: (Brookfield RVT, 10rpm, ABZ Spindle, 25.5 ± 0.5 °C) 200 ± 25 Pa.s Bonding Mechanism: Mixed-bonded Shelf Life (20 - 25 °C): 6 months PROCESSING Screen Mesh, Emulsion: 325 S/S, 25 µm Levelling Time (at 20°C): 5 - 10 min Drying Time (at 125°C): Firing Temperature Range: 10 - 15 min On alumina/beryllia/ceramics: 850 On Porcelain Enamelled Steel (PES): Optimum (alumina): Optimum (beryllia): Time at peak: 930°C in air 625°C in air 850°C in air 930°C in air 10 min Total Firing Cycle: 1 hour Substrate for Calibration: 96% alumina Thinner: ESL 401 (Note: furnace air must be clean, dry and oil-free) ESL Europe 9912-K 0601-E ESL Affiliates ESL Europe (Agmet Ltd) • 8 Commercial Road • Reading • Berkshire • England • RG2 0QZ • Tel: +44 (0) 118 918 2400 • Fax: +44 (0) 118 986 7331 • [email protected] th ESL Nippon • Sukegawa Bldg. • 6 floor • 3-4 Yanagibashi 1-chome • Taito-ku • Tokyo 111, Japan • Tel: +81-3-3864-8521 • Fax: +81-3-3864-9270 • [email protected] ESL China • Room #1707, Tower A, City Center of Shanghai • 100 Zunyi Road • Shanghai, China 200051 • Tel: +86-21-6237-0336 and 0337 • Fax: +86-21-6237-0338 [email protected] See Caution and Disclaimer on other side. TYPICAL PROPERTIES (measurement on alumina after firing at 850°C) Fired Thickness: (measured on a 2 mm x 2 mm pad on 96% alumina) Approximate Coverage: Resistivity: (measured on a 100 mm x 0.25 mm conductor track at 12.5 µm fired thickness) Printing Resolution: (line/space) 11.5 ± 2.5 µm 100 - 125 cm²/g < 2.5 mΩ/ 0.200 mm / 0.200 mm Adhesion: (90° pull, 2 mm x 2 mm pads, 62Sn/36Pb/2Ag) Initial pull strength: (on most ceramic substrates) Aged 48 hours at 150°C: > 7.0 kg > 4.5 kg Thermosonic Au Wire Bond: (25 µm wire; bond length 1 mm; 100% wire breaks; on alumina; 850°C firing) >8g Aged Au Wire Bond: (24 hours at 200°C) >7g ESL Europe 9912-K 0601-E *Complies with RoHS, ELV, WEEE and CHIP 3 EC directives. CAUTION: Proper industrial safety precautions should be exercised in using these products. Use with adequate ventilation. Avoid prolonged contact with skin or inhalation of any vapours emitted during use or heating of these compositions. The use of safety eye goggles, gloves or hand protection creams is recommended. Wash hands or skin thoroughly with soap and water after using these products. Do not eat or smoke in areas where these materials are used. Refer to appropriate MSDS sheet. DISCLAIMER: The product information and recommendations contained herein are based on data obtained by tests we believe to be accurate, but the accuracy and completeness thereof is not guaranteed. No warranty is expressed or implied regarding the accuracy of these data, the results obtained from the use hereof, or that any such use will not infringe any patent. ElectroScience assumes no liability for any injury, loss, or damage, direct or consequential, arising out of its use by others. This information is furnished upon the condition that the person receiving it shall make his own tests to determine the suitability thereof for his particular use, before using it. User assumes all risk and liability whatsoever in connection with his intended use. ElectroScience’s only obligation shall be to replace such quantity of the product proved defective. Electro-Science Laboratories, Inc. 416 East Church Road • King of Prussia, PA 19406-2625, U.S.A 610-272-8000 • Fax: 610-272-6759 • www.ElectroScience.com • [email protected] R-300-A/B Resistor Series Tolerant to Processing and Design Variations Excellent Printing Characteristics Low TCR’s High Performance Low Cost The ESL R-300-A and R-300-B Resistor Series are economical, high performance materials for the manufacture of hybrid circuits and resistors networks. Features of the ESL R-300-A and R-300-B Series include excellent printability and low sensitivity to processing conditions. The dependence of resistance and TCR on blending follows the usual curves for resistor materials. Adjacent members of the Series can be blended. The R-300-A Series members can not be blended with members of the R-300-B Series. The resistors are calibrated with ESL 9693-S PdAg conductor terminations. Other silver-based and gold-based conductors can be used; however, TCR and resistivity shifts may be observed. R-300-A/B 9910-F ESL Affiliates Japan: ESL-Nippon Company, Ltd. • Sukegawa Bldg. • 6 floor • 3-4 Yanagibashi 1-chome • Taito-ku • Tokyo 111, Japan • Tel: (011-81)-3-3864-8521 • Fax: (011-81)-3-3864-9270 [email protected] th China: Shanghai Agmet Electro-Science Laboratory Ltd. • Second Floor Bldg. 12A1 • #223 North Fe Te Road • Waigaoqiao Free Trade Zone • Shanghai, China Tel: (011-86)-21-5866-0497 • Fax: (011-86)-21-5866-0497 • [email protected] Europe: Agmet, Ltd. • 8 Commercial Road • Reading, Berkshire, England RG2 0QZ • Tel: (011-44)-118-987-3139 • Fax: (011-44)-118-986-7331 • [email protected] See Caution and Disclaimer on other side. Typical 850°C Firing Profile R-300-A/B Temperature (°C) 1000 900 800 700 600 500 400 300 200 Belt Direction Exit 100 0 0 5 10 15 20 25 30 35 40 Time (minutes) EFFECT OF OVERGLAZING ON R-300-A/B RESISTORS R-316-B R-315-B R-314-B R-314-A R-313-A R-312-A R-311-A R-310-A RESISTANCE CHANGE AFTER OVERGLAZING WITH G-471 0 Resistance Change(%) -1 -2 -3 -4 -5 -6 -7 -8 o Fired at 500 C, 30 minute cycle, 2 minutes at peak temperature -9 -10 R-300-A/B 9910-F CAUTION: Proper industrial safety precautions should be exercised in using these products. Use with adequate ventilation. Avoid prolonged contact with skin or inhalation of any vapors emitted during use or heating of these compositions. The use of safety eye goggles, gloves or hand protection creams is recommended. Wash hands or skin thoroughly with soap and water after using these products. Do not eat or smoke in areas where these materials are used. Refer to appropriate MSDS sheet. DISCLAIMER: The product information and recommendations contained herein are based on data obtained by tests we believe to be accurate, but the accuracy and completeness thereof is not guaranteed. No warranty is expressed or implied regarding the accuracy of these data, the results obtained from the use hereof, or that any such use will not infringe any patent. Electro-Science assumes no liability for any injury, loss, or damage, direct or consequential arising out of its use by others. This information is furnished upon the condition that the person receiving it shall make their own tests to determine the suitability thereof for their particular use, before using it. User assumes all risk and liability whatsoever in connection with their intended use. Electro-Science’s only obligation shall be to replace such quantity of the product proved defective. <8 COEFFICIENT OF VARIATION (%) 436 NA NA MAX RATED POWERf (mW/mm2) QUAN-TECH NOISE (dB) LASER TRIM (%∆R) (1000 hours at 150°C) ≤ 0.3 NA 871 2.95 7.38 ≤ 0.3 ≤ -10 300 54.8 137 0 ± 50 ESL 401 <7 ± 10 10 k R-314-A ESL 9693-S ≤ 0.3 ≤ -10 ≤ -10 ≤ 0.3 944 30.7 76.8 0 ± 50 968 9.84 24.6 0 ± 100 <8 ± 10 1k R-313-A ≤ 0.3 ≤2 360 60 150 0 ± 100 <5 ± 10 10 k R-314-B R-300-A/B 9910-F b 3 CALIBRATION: Resistor size used for tests; A—1.25 mm square; B—1.0 mm square at dried thickness shown. VISCOSITY: Brookfield RVT, ABZ Spindle, 10 rpm, 25.5°C±0.5°C. c CTCR: -55°C to +25°C. HTCR: +25°C to +125°C. d STOL: Voltage required, 5 second duration, to induce a resistance change of ±0.1% at 25°C. Resistor size as in 1. e STANDARD WORKING VOLTAGE: 0.4 x STOL Voltage. f MAXIMUM RATED POWER: (Standard Working Voltage)2/Resistance. a The R-314-B is used as a blending member with R-315-B. For use as a 10 kΩ/sq. resistor, R-314-A is recommended. TERMINATION OF CALIBRATION 0.66 STD. WORKING VOLTAGE (V/mm) 1.65 STOLd (V/mm) e 50 ± 100 TCR (ppm/°C) c THINNER 22.5 ± 2.5 DRIED THICKNESS (µm) <8 225 ± 25 0 ± 100 <8 ± 10 100 R-312-A VISCOSITY (Pa•s) b ± 30 SHIPPING SPECIFICATION (%) ± 10 10 1 RESISTIVITY (Ω/square) a R-311-A R-310-A PROPERTIES TYPICAL RESISTOR PROPERTIES R-300-A/B RESISTOR SERIES ≤ 0.4 ≤5 190 140 350 0 ± 100 20.0 ± 2.0 300 ± 50 <5 ± 10 100 k R-315-B ≤ 0.5 NA 17 130 330 0 ± 100 <8 ± 10 1M R-316-B 4 4 5 5 0.8 1.0 1.2 1.4 1.6 0.4 R-300-A/B 9910-F 0.4 2 3 Resistor Length (mm) R-314-A 2 3 Resistor Length (mm) 0.4 1 1 0.6 0.8 1.0 1.2 1.4 1.6 0.6 0 0 R-310-A 0.6 0.8 1.0 1.2 1.4 1.6 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Relative Resistivity Relative Resistivity 0 0 1 1 2 3 Resistor Length (mm) R-314-B 2 3 Resistor Length (mm) R-311-A 4 4 5 5 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0.4 0.6 0.8 1.0 1.2 1.4 1.6 4 0 0 1 1 2 3 Resistor Length (mm) R-315-B 2 3 Resistor Length (mm) R-312-A RESISTANCE VERSUS LENGTH R-300-A/B Resistor Series Relative Resistivity Relative Resistivity Relative Resistivity Relative Resistivity 4 4 5 5 Relative Resistivity Relative Resistivity 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0 0 1 1 2 3 Resistor Length (mm) R-316-B 2 3 Resistor Length (mm) R-313-A 4 4 5 5 R-300-A/B Resistor Series TCR VERSUS PEAK FIRING TEMPERATURE (10 minutes at peak temperature) R-310-A R-311-A 175 R-312-A 175 175 Cold TCR 125 125 75 75 Hot TCR 125 Hot TCR 75 Hot TCR 25 25 25 Cold TCR -25 -25 -25 -75 -75 -75 -125 -125 -125 Cold TCR -175 825 -175 850 Peak Firing Temperature 875 -175 825 R-313-A 850 Peak Firing Temperature 875 825 R-314-A 175 R-314-B 175 125 175 125 125 Hot TCR Hot TCR 75 75 75 25 25 25 -25 -25 -25 -75 -75 -75 -125 -125 -125 825 -175 850 Peak Firing Temperature (°C) Hot TCR Cold TCR Cold TCR Cold TCR -175 875 -175 825 850 Peak Firing Temperature (°C) R-315-B 875 825 850 Peak Firing Temperature (°C) R-316-B 175 175 125 125 75 Hot TCR 25 75 25 -25 Hot TCR -25 Cold TCR -75 -75 -125 -125 -175 825 R-300-A/B 9910-F Cold TCR -175 850 Peak Firing Temperature 875 850 Peak Firing Temperature 875 825 5 850 Peak Firing Temperature (°C) 875 875 R-300-A/B Resistor Series TCR VERSUS TIME AT PEAK FIRING TEMPERATURE (850°°C) R-310-A R-311-A R-312-A 350 350 150 300 300 100 250 250 Hot TCR 50 200 200 0 150 150 Cold TCR 100 Hot TCR Cold TCR -50 100 Hot TCR 50 -100 50 Cold TCR 0 0 8 10 12 Time at Peak Firing Temperature (minutes) -150 8 10 12 Time at Peak Firing Temperature (minutes) R-313-A 8 10 12 Time at Peak Firing Temperature (minutes) R-314-A R-314-B 150 150 150 100 100 100 50 50 Hot TCR Hot TCR 50 Hot TCR 0 0 0 Cold TCR -50 -50 -50 Cold TCR -100 -100 -150 12 8 10 Time at Peak Firing Temperature (minutes) -150 Cold TCR -150 8 10 12 Time at Peak Firing Temperature (minutes) R-315-B 8 10 12 Time at Peak Firing Temperature (minutes) R-316-B 150 150 100 100 50 -100 Hot TCR 50 0 0 -50 -50 Hot TCR Cold TCR -100 -100 -150 -150 12 8 10 Time at Peak Firing Temperature (minutes) 8 10 12 Time at Peak Firing Temperature (minutes) R-300-A/B 9910-F Cold TCR 6 R-300-A/B Resistor Series R-300-A SERIES - RELATIVE RESISTIVITY vs. PEAK FIRING TEMPERATURE 1.60 Relative Resistivity R-314-A 1.40 R-313-A R-312-A R-311-A 1.20 R-310-A 1.00 0.80 0.60 820 830 840 850 860 870 880 Peak Firing Temperature (°C) R-300-B SERIES - RELATIVE RESISTIVITY vs. PEAK FIRING TEMPERATURE 1.60 R-316-B Relative Resistivity 1.40 R-315-B R-314-B 1.20 1.00 0.80 0.60 0.40 820 830 840 850 860 870 880 Peak Firing Temperature (°C) Time at peak temperature = 10 minutes. Relative Resistivity = resistivity at specified peak firing temperature/resistivity at 850°C. R-300-A/B 9910-F 7 R-300-A/B Resistor Series R-300-A - RELATIVE RESISTIVITY vs. TIME AT PEAK TEMPERATURE R-314-A 1.20 R-313-A Relative Resistivity R-312-A 1.10 R-311-A R-310-A 1.00 0.90 0.80 6 8 10 12 14 Time at Peak Temperature (minutes) R-300-B - RELATIVE RESISTIVITY vs. TIME AT PEAK TEMPERATURE Relative Resistivity 1.20 R-316-B 1.10 R-315-B R-314-B 1.00 0.90 0.80 6 8 10 12 14 Time at Peak Temperature (minutes) Peak temperature = 850°C Relative Resistivity = resistivity at specified time at peak temperature/resistivity at 10 minutes. R-300-A/B 9910-F 8 1987 Gordon and Breach Science Publishers, Inc. Printed in Great Britain Active and Passive Elec. Comp., 1987, Vol. 12, pp. 231-237 Photocopying permitted by license only STABILITY AND PERFORMANCE CHARACTERIZATION OF THICK FILM MICRORESISTORS SHOBHA C. RAVI Roa& Kanata, Canada Epitek Electronics, 100 Schnieder In recent years, interest in the performance of small dimension resistors has increased primarily due to the need to reduce parasitic resistance in high frequency applications. This paper presents results on the characterization of thick film microresistors, i.e. resistors of 80 80 mil to 10 x 10 mil dimension. The thickness, sheet resistance and temperature coefficient of resistance were dependent on the resistor length, whereas, thermal ageing drift and the thermal cycling drift values did not exhibit any such dependence. With reasonable precautions and optimization of the manufacturing conditions highly stable and good quality microresistors can be fabricated. 1. INTRODUCTION The general trend towards hybrid miniaturization, the increasing customer’s demand for high density circuits and the need to reduce parasitic resistance in high frequency circuits motivated this investigation on characterization of thick film microresistors. These have reduced dimensions compared with those generally used in hybrids and that are recommended by the ink vendor. It is known that the resistor performance is effected by its dimension. The purpose of this study was not to introduce any major changes to our thick film manufacturing line, nor to investigate any particular ink source or any new material. The properties of as-fired resistors, terminated on gold, have been measured as a function of resistor length and resistance value. The post-trim drift, temperature coefficient resistance and stability have been considered. To the author’s knowledge this is one of the first investigations on performance of thick film microresistors having dimensions smaller than 40 40 mils. Bellardo et.al and Naguib 2 have reported on resistors of larger dimensions, i.e. 50 mils. 2. EXPERIMENTAL METHOD The inks used in this work were DuPont 1711 (10 ohm/sq) and the DuPont 1600 series (100 ohm/sq to 1 Mohm/sq). All resistors were terminated with gold conductors (4119) and overglazed with 3563. Ceramic substrates of 96% alumina and 2 in. 2 in. were used. The test pattern, as illustrated in figure 1, consisted of 20 parts (specimens) having nine resistors each. The resistors were of equal aspect ratio (AR 1.0) but of different lengths, i.e. from 80 x 80 mils to 10 x 10 mils. The specimens were prepared under the normal thick film production processing conditions; conductors and resistors were printed with a 325 mesh screen to a fired average thickness of 20-25 m. Prior to the final specimen preparation initial work was done to establish the optimum fabrication parameters. All resistors were laser trimmed and encapsulated before subjecting them to stability tests. The resistors were trimmed to approximately 2.3 times the as-fired value with conventional plunge cuts. Laser trimming conditions were those normally used on our production line. 231 SHOBHA C. RAVI 232 FIGURE 1. Test pattern: (Scale in inches) 80 50 30 R1 R4 R7 80 mils; R2 50 mils; R5 30 mils; R8 70 40 20 70 mils; R3 40 mils; R6 20 mils; R9 60 30 10 60 mils; 30 mils; 10 mils. RESULTS AND DISCUSSION 3. The post-trim drift at room temperature was negligible (average (/kR/R)% < 0.1) over a two month period. The pre-trimmed average resistance values are tabulated in Table I. It is observed that there is a strong dependence of resistance on the resistor length. The sheet resistance is constant down to 50 mils and decreases with further decrease in length (Figure 2). This is due to the larger thickness of the smaller dimension resistors. Analysis of thickness profiles of resistors is illustrated in Figure 3. The results indicate that films of length Pre-trimmed TABLE Average Resistance vs. Resistor Length Average Resistance (ohm) length (mil) 1711 1621 1631 1641 1651 1660 80 14.04 155.63 1410 10640 83750 1912000 60 13.60 150.62 1340 10270 81920 1857000 30 12.35 136.46 1180 9110 73350 1524000 20 11.26 116.52 1080 8770 65150 1268000 10 8.61 93.3 790 7010 50420 888000 CHARACTERIZATION OF THICK FILM MICRORESISTORS 233 160---- 120 80 40 1621 0 80 60 30 20 10 Length (mils) FIGURE 2. Dcpcndcnce of shcet resistance on resistor length less than 50 mils are thicker. The thickness is constant down to 50 mils and increases with further decrease in length. This behavior of sheet resistance and thickness is independent of the resistance value of the paste. 4. TEMPERATURE COEFFICIENT OF RESISTANCE ’Hot’ and ’Cold’ temperature co-efficient of resistance (TCR) were calculated from the measurements taken between +25C and -55C respectively. As expected, the TCR 3O E 25 = o 20 a 10 o 20 o o 30 40 50 Length (mils) FIGURE 3. Thickness variation with resistor length 60 70 80 SHOBHA C. RAVI 234 TABLE II Average TCR (ppm/C) Rcs. Length (mils) C H 1631 1621 1711 80 +71.35 +25.74 H C H 1641 C H 69.93 -170.10 50.01 -141.09 -4.59 1651 C H 1660 C H C 82.85 -29.17 -118.58 -41.98 -125.81 70 +77.65 +30.98 68.16 -171.82 51.88 -145.61 -4.91 83.89 -28.93 -117.65 -43.82 -128.93 60 +80.71 +33.14 73.27 -179.06 51.58 -146.98 -7.24 88.04 -30.12 -120.06 -45.10 -129.86 50 +87.85 +38.28 75.69 -181.04 53.05 -147.60 -9.11 91.41 -31.39 -121.65 -44.68 -128.18 40 +78.81 +29.85 80.51 -186.98 55.62 -151.01 -1.41 96.82 -33.67 -124.81 -45.96 -130.05 30 +74.05 +29.82 87.61 -197.38 66.41 -167.27 -1.85 -102.89 -37.59 -128.02 -44.88 -128.18 30 +73.32 +30.74 86.93 -191.59 68.02 -175.34 -1.78 -104.21 -36.93 -136.43 -43.63 -132.16 20 +73.06 +32.93 -103.14 -214.74 79.72 -181.07 -3.43 -122.51 -51.60 -147.39 -46.22 -133.28 10 +87.41 +48.07 -144.77 -270.76 -142.42 -260.95 -7.43 -181.07 -88.24 -195.11 -69.15 -157.11 behavior trends for the two series, 1711 and 1600, were quite different. Both the ’Hot’ and ’Cold’ TCR values are positive for 1711 paste, whereas, it is negative for 1600 series (Table II). This could be due to their different rheological properties and also due to the higher metal content of the 10 ohm/sq paste. However, in both cases the TCR values do not change sign with decrease in length. All the higher resistivity (100 ohm/sq to 100K ohm/sq) resistors have TCR strongly dependent on resistor length. Our results indicate that the magnitude is constant down to 50 mils and increases with further decrease in resistor length. This behavior is independent of the paste resistance value. Thus, this is a consequence of the observed decrease in sheet resistance with length. 0’I 80 -40 0" -80 70 Resistor Length (mil) 60 50 30 40 _I------l-- 20 _ii \ *--’’*-’----*--__"" oo=,a M 100 K K -120 100ohm/sq -160 FIGURE 4. 10 Dependence of temperature co-efficient of resistance on resistor length CHARACTERIZATION OF THICK FILM MICRORESISTORS 235 Resistor Termination FIGURE 5. Illustration of thick film resistor A simple formula for the total resistance is (3): R Os (l/w) + 0’s (2d/w) (1 + 0’s/0s) -1 + Rc (1) where 0s and 0’s are the sheet resistivities of the thick film resistor and the conductive termination material, and w are the length and width of the resistor and d is the overlap length of the resistor on the termination (Figure 5). The first term represents the resistor sheet resistance, the second is that of the parallel combination of resistor and conductor overlap and the third term, RC, is the contact resistance at the resistor-conductor interface. Rc can be expressed as (3): Rc 2/w x (0s/G) 1/2 (2) where G is the conductance of the resistor-conductor interface. From Eqns. 1 and 2 the effective sheet resistance is given by R 0s (l/w) + 0’s (2d/w) x 1/(1 + 0’s/0s) + 2/w x (0s/G) 1/2 The second term can be neglected since 0s "> R 0s (l/w) 0’s. + 2/w x (0s/G)1/2 (3) Thus, (4) The resistance is thus a function of geometry and the interface conductance. This explains the decrease in resistance and the subsequent increase in TCR with decrease in resistor length. It is also observed that the magnitude of TCR is dependent on the resistivity of the paste. As shown in Figure 6, the TCR decreases with increase in paste resistivity, attains a minimum value at 10 Kohm/sq and then increases with further increase in resistivity. This behavior is independent of the resistor length. The first part of the curve can be explained as due to the increase in resistor resistivity and consequently a decrease in TCR. The increase in TCR observed in the latter half of the curve may be due to the large change in resistance (A R) with temperature. It is well known that higher resistivity materials undergo a larger change in resistance than low resistivity materials. SHOBHA C. RAVI 236 1621 Paste # 1631 1641 1651 1660 1621--100 ohrn/sq 163 I--I Kohm/sq 1641-- 10 Kohm/sq 1651--100 Kohm/sq 1660-- Mohm/sq FIGURE 6. Variation of temperature co-efficient of resistance with resistivity of the paste 5. THERMAL AGEING Thermal ageing of encapsulated, trimmed resistors was carried out at 125C for 100 hrs with no load applied. The average percentage change in resistance (A R/R, %) is tabulated as a function of resistor length in Table III. The results can be summarized as follows: 1. Not all the drifts were positive 2. The 10 ohm/sq paste resistors have a relatively higher drift value 3. There is no dependence on the resistor length nor on the resistivity TABLE III @ 125 C for 100 hrs. Thermal ageing (AR/R)% length (mil) 1711 1621 1631 1641 1651 1660 80 -0.31 +0.02 +0.04 -0.06 +0.42 -0.09 60 -0.33 +0.03 -0.11 -0.09 +0.50 -0.14 30 -0.41 -0.10 -0.04 -0.07 +0.17 -0.17 20 -0.36 -0.07 +0.13 -0.20 +0.12 -0.11 10 -0.39 -0.09 -0.07 +0.12 +0.42 -0.15 CHARACTERIZATION OF THICK FILM MICRORESISTORS 237 TABLE IV Pcrccntagc resistance drift after 20 thermal cycles (AR/R%) length (mil) 1711 1621 1631 1641 165l 1660 80 0.14 0.06 0.04 0.04 0.01 0.05 0. (18 0. (/2 (/. 01 (I. 02 0.09 0.06 0.08 60 30 0. (19 0.02 0.00 0.07 0.05 20 0.10 0.04 0.01 0.11 0.16 0.06 10 0.16 0.04 0.06 (I. 14 0.22 0.06 6. THERMAL CYCLING The thick film resistors were subjected to twenty thermal cycles between -55C and + 125C, and the percentage resistance drift was measured. As shown inTable IV, the geometry and resistivity of the resistors do not effect the stability. All the resistors exhibit excellent stability: A R/R < 0.20% after twenty cycles. The drifts were all positive. 7. CONCLUSIONS The resistor thickness increases with decrease in resistor length below 50 mils. The post-trim drift is negligible (less than 0.1% over a two months period) and is independent of the resistor length and resistivity. The temperature coefficient of resistance is minimum for the 10 Kohm/sq paste (1641). The ’Cold’ TCR value is in general larger than the ’Hot’ TCR value. TCR is length independent down to 50 mils, increases gradually at 20 mils and sharply for a 10 mil resistor. The thermal ageing drift is less than 0.2% and the thermal cycling drift (20 cycles) is less than 0.20% The performances of these microresistors having dimensions as small as 10 10 mils are acceptable and have qualified the MIL-STD-202 specifications. However, good control during manufacture is necessary. All the above data presented in this paper has been averaged over 500 thick film resistors for each test. ACKNOWLEDGEMENT The author would like to thank Rob Collier for conducting most of the measurements. REFERENCES 1. 2. 3. A. Bellardo, and G. Lovati, Hybrid Circuits. no. 4, pp. 26-31 (1984). H.M. Naguib, Proc. International Microelectronics Symposium, pp. 48-59 (1977). H.S. Fisher, and P.M. Hall, Proc. IEEE, vol. 59, p. 1418 (1971).