Prelim Ib09 - . YOUR NAME PLEASE PRINT MSE 40200 Prelim I...

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MSE 40200 Prelim I October 9, 2008 1. A 2500 lbs car, traveling at 30 mph is hitting a concrete wall. The designer has designed the car such that all the energy is dissipated by crunching an Al front end, 3 feet in length down to 1 foot. The stress strain curve of Al is given by True stress-true strain curve in tension for 1100-0 aluminum plotted on a log log scale (reproduced from S. Kalpakjian, Manufacturing Processes for Engr. Materials). Y = (4740,0.00025) a) Verify that the coordinates of Y are correct ( 2 pt) b) Derive an analytical description that describes the stress strain curve in units of PSI, as a function of strain (4 pts) c) Assume that the material fails catastrophically when the true strains reaches 1. What is the engineering strains, in % ? (4 pts) d) Calculate the kinetic energy stored in the traveling car in units of your choice but give the answer in units of foot pounds. (5 pt) e) Using the data given in the plot, and assuming failure at a true strain of 1, how many pounds of Al are needed to absorb the kinetic energy. The density of Al is
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Prelim Ib09 - . YOUR NAME PLEASE PRINT MSE 40200 Prelim I...

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