**Introduction**

This unit reviews some of the basic concepts explained in Material Science courses and uses them to develop the generalized Hooke’s Law, the fundamental relationship we will use to examine the loading and deformation throughout this course. Although most of it should be reviewed, it is important for you to fully grasp the concepts in this unit to succeed in this course. This unit is divided into three topics.

**Learning Objectives**

By the end of this unit, you should be able to:

- Describe the concept of stress/strain and in its relation to force/displacement.
- Describe the difference between normal and shear stresses/strains.
- Describe the difference between normal and shear stresses strains.
- Apply the sign convention for stresses/strains to determine the appropriate sign for a given stress/strain state.
- Define and prove the concept of complementary shear stress.
- Define Youn’s modulus, shear modulus, Poisson’s ratio and thermal coefficient of expansion.
- Calculate the strain state at a point from the stress state using Hooke’s Law, and vice-versa.

#### 1.1 Stress

#### 1.2 Strain

#### 1.3 Hooke’s Law

#### 1.4 Summary and Further Reading