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Rede Temática em Engenharia de Materiais
UFOP - CETEC - UEMG
REDE MAT
_________________________________________________________________________
Belo Horizonte, 28 de julho de 1997.
Exame de seleção para o ingresso no Mestrado em Engenharia de Materiais.
Segundo semestre de 1997
Prova de Inglês
Instruções ao Candidato:
1. Leia o texto anexo e redija, em português, uma interpretação livre de cada um dos parágrafos presentes no original
em inglês.
2. O exame terá uma duração de 2h (duas horas).
Adapted from
‘Materials Courses for Student Engineers in the 1990s”
by Lawrence H. Van Vlack
Journal of Materials, january 1990
Introduction
Its well acknowledged that engineers of all disciplines encounter technical materials in their professional
activities. The products that they make, and the systems that they develop and monitor, involve parts and components that
utilize a wide variety of materials which possess the specific characteristcs and properties to meet the necessary demands.
While mechanical, electrical and many other types of engineers normally do not develop the materials to be used, each of these
engineers work closely with materials engineers in the selection, processing and enhancement of the materials required for their
products and systems. Therefore, they must posses a basic understanding of the engineering materials. As their products and
systems become more sophisticated and the number and variety of materials increase, a renewed attention is warranted with
respect to the initial course in materials that is offered to engineers who will not be materials science and engineering (MSE)
majors.
In this article, the introductory course in materials is reexamined. Being a introductory materials course, it
assumes a background in general chemistry and physics. Typically, this is the only materials course in these engineering
curricula. It is usually located near the middle of the undergraduate curriculum, since it should precede design courses. This
sequence of basic science >materials>design requires that attention be given to the necessary coupling if the engineering
curricula are to be optimized.
The current trend has been toward emphasizing basic principles and applying these principles appropriately to
various materials.
Background
There has been an evolutionary change in the nature of the materials courses taught to engineers. The “shop”
course of pre-World War Il days has completely disappeared. Commonly, it included metal casting and some metal shaping by
deformation and machining. The civil engineering version included concrete, plus selected properties of structural metals.
During that same period, what is now know as materials engineering focused separately on: extractive
metallurgy; the forming and firing of ceramics; and the chemical synthesis that is applicable to plastics. These courses started
with raw materials. The characteristics of the material product received by the technical consumer were basically dictated by
the primary process. The above categories were isolated, since, in general, the nature of the raw materials led to distinct
processing procedures for plastics, ceramics and metals.
Although the metallurgical engineer, the ceramic engineer, and the polymer chemist improved existing
products and develop new products from their raw materials, the concerted effort to “tailor-make” materials for specific uses
required the combined effort of those making materials and those using them in technological applications. This approach has
been accelerated over the past few decades, and palces and emphasis on the materials instruction for all engineers.
2
During the period just cited, metallurgists played a leading role in the classroom since metals were a
predominant material for technological advances. Further, many metals were simpler and more readily understood than were
the commonly avaialable ceramics and plastics. This led to earlier process control and product improvements among many
metals. If there were a metallurgy department, a course in metallurgy could be required in the curriculum, particularly for
mechanical engineers. In the absence of a metallurgy department, the mechanical engineering department commonly included a
metallurgist as a faculty member.
Relatively few schools had ceramic engineering departments. Also, academic contacts between the
engineering units and those chemists focusing on plastics were commonly remote. Thus, as engineering uses on nonmetallic
materials increased in the technical world, their inclusion into a materials course lagged. When included, those materials would
receive attention as an inserted chapter in an otherwise metallurgical text. Such additions had relatively low odds of being
covered within the time pressures of a course. Typically, these inserted topics were limited to the description of selected
processing equipment, or to the presentation of unrationalized data.
More recently, an effort has been made toward balancing the presentation of all types of materials. This
integration is a result of several factors. First, a materials science and engineering community has emerged as a federation of
the several materials disciplines – metals, ceramics and polymers. Second, design engineers have demonstrated and increasing
willingness to consider substitute materials when these materials are shown to have the required characteristics. Third, unifying
principles that apply to more than one of the materials categories have been expanded. From this, younger staff members feel
freer to venture into the adjacent materials disciplines in both research and teaching. Fourth and finally, textbooks have become
available that develop the principles that control properties and service behavior.
The pattern for the 1990s is already emerging as a consequence of the above mentioned inputs. It involves a
greater attetion to basic science principles, to the structural response of various materials to these principles, and to property
consequences that result. Processing steps are an important adjunct, which may vary with the clientele of the course and the
sequel design courses. The next item lists some principles that apply to a variety of different materials, and should be part of
any introductory course in materials science.
Principles Pertinent to Solids
Basic principles apply to all types of materials since they are governed by the laws of natures. In some cases,
parallelisms between material categories are easy to envisage. Such examples include the crystallization of metals and the
crystallization of most oxide ceramics. Further, crystallinity may be expected in some of the polymeric materials such as the
high density polyethylene.
Likewise, the age-old process of supercooling silicate liquids past their glass transition temperature to
produce silicate glasses is duplicated among the majority of the common polymers with resulting amorphous or vitreous phases.
Thus, it was also anticipated that very rapidly quenched metals could be glassy, and that they too would exhibit glass-trasition
temperatures. This has proved to be the case. A large number of other parallelisms between ceramics, polymers and metals
could be cited. Included would be examples such as diffusion, powder processing, notch sesitivity for fracturing, radiation
damage, vapor deposition, magnetic saturation in superconductors, and crystal imperfections – to name a few.
Of course, it is necessary to recognize that the response of various materials will not behave identically.
Aluminum silicate, with a more complex structure than aluminum oxide, crystallizes more slowly. Conversely, pure metals
crystallize so rapidly that it is nearly impossible to obtain them in vitreous form. For example, glassy iron for low-loss magnetic
applications must include solutes such as phosphorus, silicon or boron to slow crystallization to a practical quenching rate. Any
materials course that builds on the commonality of principles must also address the differences in the response of the materials.
Therefore, the basic topics that should be included in an introductory materials course include: chemical
bonding, crystallinity, disorder, phase relationships, reaction rates, and microstructural development.