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EGGG 101: Introduction to Engineering Dr. Jill Higginson Assistant Professor Department of Mechanical Engineering University of Delaware ME Lecture 4 Today’s objectives Introduction What can MEs do? What is biomechanics? Newton’s laws Introduction to biomechanics lab Introduction Course webpage Schedule Engineers… Apply tools of math and science to develop cost-effective solutions to technological problems in society Design consumer products Develop machinery, factories (processes) and quality control systems for manufacturing products Make useful things that work! Mechanical Engineering Liberal arts of engineering Diverse applications – Biomechanics – Composites and materials – Environmental and bio-fluid mechanics – Robotics and control – Fuel cells (clean energy) – Manufacturing science Mechanically engineered products Micro-electro-mechanical sensors in airbags HVAC for office buildings Off-road construction equipment Hybrid vehicles Gears, bearings, machine components Artificial hip implants Deep-sea research vessels Robotic manufacturing systems Replacement heart valves Planetary exploration spacecraft Top Ten Achievements 1. 2. 3. 4. 5. 6. Automobile Apollo program Power generation Agricultural mechanization Airplane Integrated-circuit mass production 7. 8. 9. 10. Air conditioning and refrigeration Computer-aided engineering technology Bioengineering Codes and standards Automobile High power, lightweight engines (ICE) Efficient mass production Safety, fuel economy, comfort, emission control Hybrid technology, antilock brakes, air bags, composite materials, fuel injection systems, GPS, fuel cells Computer-aided engineering technology Automation technologies Performing calculations Preparing technical drawings Simulating performance Controlling machine tools Analysis software Information databases Prototyping equipment What is biomechanics? The science that examines forces acting upon and within a biological structure and effects produced by such forces CYTOMECHANICS IMAGING FLUID DYNAMICS EXPERIMENTATION and INTERVENTION MODELING and SIMULATION Running shoes Goals – protect foot, run faster, keep cool Materials selection – Foam, air pockets, gel, springs Absorb shock Promote stability / flexibility Ventilation (thermodynamics!) Sensors Fashion statement! Injury mechanisms Forces on the musculoskeletal system Moment = tendency of a force to make an object rotate Depends on force and lever arm M=∑Fd The time rate of change of momentum of a body is equal to the magnitude of the applied force and acts in the direction of the force F d (mv) dt Inverse dynamics Calculate elbow joint moment (M=∑Fd) M=(10N)(0.13m) + (20N)(0.30m) M=7.3 Nm M=(Fbiceps)(0.025m) F=10 N Fbiceps = 292 N M=? F=20 N 30 cm 2.5 cm Optimization Estimate muscle forces from joint moment Choose optimization function Infinite solutions possible! Muscle force l l l muscle force Force-length curve Force-velocity curve active lengthening passive shortening muscle fiber length muscle fiber velocity Strength Applications Rehabilitation devices Exoskeleton (rehab, carry load) Accident reconstruction Helmet design Biomechanics Lab Objectives: – To develop the force-length curve based on isometric strength of the quadriceps muscle group – To quantify changes in pressure under the foot as a function of footwear – To manipulate ground reaction forces during dynamic activities Motivation Oscar Pistorius – Blade Runner – Fastest man on no legs – “I’m not disabled, I just don’t have any legs” Double amputee world records: 100m, 200m, 400m – 2008 Paralympic gold (100,200) 400 m – 2004 Olympic gold (men): 44.00 – Pistorius world record: 46.56 – 1928 Olympic gold (men): 47.8 IAAF 2007: ban the use of “any technical device that incorporates springs, wheels or any other element that provides a user with an advantage over another athlete not using such a device” Does Pistorius have an unfair advantage? Cheetahs Stage 1: absorbs 97% impact, stores energy (higher speed -> higher force) Stage 2: gluts and quads provide propulsion Stage 3: blade releases energy at push-off Natural leg Stage 1: Achilles tendon absorbs and stores impact energy Stage 2: gluts, quads and plantarflexors provide propulsion Stage 3: plantarflexors releases energy at push-off Methods MAmax P=F/A “isometric strength” “plantar pressures” Methods “ground reaction forces” Lab Report Due: Wednesday by 5:00 pm Answer questions on template! Describe experimental and analytical methods (brief) Results – What measurements were recorded and computed? – How does strength vary with knee flexion angle? Discussion and Conclusions – – – – At what knee angle is performance best? How does peak pressure vary with shoe selection? How does force change with dynamic activities? What factors should be considered in the design of a prosthesis for Oscar Pistorius? Lab report template Logistics Spencer 209 You will rotate through 3 stations Data may be collected solo or with a partner Resources • Running shoes • http://people.bath.ac.uk/mnp21/Adv_mat _sports.htm • www.basf.com/corporate/elastollan.html • http://engineeringworks.tamu.edu/?p=29 • Cheetah: • http://www.wired.com/wired/archive/15. 03/bladefast.html