HW 1 Solution 1-7 Solution: Springs are intended to resist high elastic forces, where only the atomic bonds are stretched when the force is applied. The silicon nitride would satisfy this requirement. However, we would like to also have good resistance to impact and at least some difficulty (in case the spring is overloaded) to assure that the spring will not fail catastrophically. We also would like to be sure that all springs will perform satisfactorily. Ceramic materials such as silicon nitride have a virtually no ductility, poor impact properties, often are difficult to manufacture without introducing at least some small flaws that cause to fail even for relatively low force. The silicon nitride is NOT recommended. 1-14 Solution: In order to produce an aluminum matrix composite material with a density of 1.5 g/cm 3 , we would need to select a material having a density considerably less than 1.5 g/cm 3 . While polyethylene’s density would make it a possibility, the polythene has a very low
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