MANE-4030: Elements of Mechanical Design: Worksheet #1 8/27/07: Topic: reliability A supplier of 4340 steel has shipped enough material to fabricate 100 fatigue-critical tension links for an aircraft application. As required in the purchase contract, the supplier has conducted uniaxial fatigue tests on random specimens drawn from the lot of material and has certified that the mean fatigue strength corresponding to a life of 10 6 cycles is 68,000 psi, the standard deviation on strength corresponding to a life of 10 6 cycles is 3200 psi, and that the distribution of strength at a life of 10 6 cycles is normal. The tension link has a cylindrical cross-section with a diameter of 0.5 inch with a tolerance of ± 0.002 inch. From dynamic simulations, it has been determined that the expected force amplitude on this component is 10,000 lb with a standard deviation of 1500 lb. You are to estimate how many tension links from the lot of 100 are expected to fail when operated for 10 6 cycles. (a)
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