"The transformation of strain at a point is similar to the transformation of stress, and as a result the methods of Chapter 9 will be applied in this chapter. Here we will also discuss various ways for measuring strain and develop some important material-property relationships, including a generalized form of Hooke's law. At the end of the chapter, a few of the theories used to predict the failure of a material will be discussed."

PLANE
NORMALLY A FLAT, IMAGINARY SURFACE

PLANE STRAIN
A DEFORMATION OF AN OBJECT IN WHICH ALL THE DISPLACEMENTS OF THE PARTS OF THE OBJECT ARE PARALLEL TO A SINGLE PLANE (OR FLAT SURFACE)

PRINCIPAL STRAIN
THE ELONGATION OR COMPRESSION OF THE OBJECT ALONG ONE OF THE PRINCIPAL AXES OF STRAIN OF THE OBJECT.

STRAIN