To better understand the behavior of a torsion member, a grid will be superimposed on the surface of a shaft to help illustrate the deformation of the shaft in response to an applied torque . The left end of the shaft will be held fixed in position.
Several characteristics of torsional loading can be observed on the circular prismatic shaft.
1. The longitudinal axis of the shaft remains straight.
2. The shaft does not increase or decrease in length.
3. Radial lines remain straight and radial as the cross section rotates.
4. Cross sections rotate about the longitudinal axis of the member.