ABSTRACT
Stress and strain are dened in many elementary textbooks about the mechanics of deformable bodies [1,2]. e terms stress and strain are used to describe loads on and deformations of solid materials. e simplest types of solids to describe are homogeneous and isotropic. Homogeneous means the material properties are the same at dierent locations and isotropic means the material properties are independent of direction in the material. An annealed steel bar is homogeneous and isotropic, whereas a human femur is not homogeneous because the marrow has very dierent properties from the bone, and it is not isotropic because its properties are dierent along the length and along the cross section.
