If the material at a point is subjected to a state of triaxial stress, Fig. 10–18a, associated normal strains will be developed in the material. The stresses can be related to these strains by using the principle of superposition, Poisson’s ratio, and Hooke’s law, as it applies in the uniaxial direction, For example, consider the normal strain of the element in the x direction, caused by separate application of each normal stress. When is applied, Fig. 10–18b, the element elongates in the x direction and the strain is