The assumption, generally, made in the theory of simple bending is that

The change in length due to a tensile or compressive force acting on a body is given by (where P = Tensile or compressive force acting on the body, l = Original length of the body, A = Cross-sectional area of the body, and E = Young's modulus for the material of the body)

The maximum shear stress in a thin spherical shell subjected to an internal pressure (p) is zero.

The state of stress at a point in a loaded member is shown in the below figure. The magnitude of maximum shear stress is

For biaxial stress, the planes of maximum shear are at right angles to each other and are inclined at 45° to the principal planes.