Introduction

There are many classifications of materials properties: thermal, electrical, chemical, optical etc. Of these, probably the most uniformly applicable in different fields is mechanical properties - how materials respond to applied forces. This is because all materials are exposed to applied forces in some ways, and so mechanical response must be considered.

The importance of mechanical properties in construction, aerospace, automotive, and manufacturing is clear. For example, we just need to consider electronic properties for semiconductors in an integrated circuit, right? Well, the computer gets thrown in a backpack and jiggled around. The transistor containing the material changes temperature and may develop thermal stresses. There are mechanical loads during fabrication. The performance of the semiconductor does, to some degree, depend on its mechanical behavior. You'll find that no matter the application, mechanical properties are important.

In this chapter we'll again connect microscale phenomena to macrosopic behaviors. Why do some materials stretch and then return to their original shape while others are permanently deformed? How much energy can we absorb during these deformations? Can we recover it? What's happening to atoms and microstructures when these deformations occur? If we understand those behaviors, can we engineer materials to be stronger, stiffer, more impact-resistant? We'll discuss some of these behaviors in this chapter and the next.