Torque T is applied on a shaft of length L at either ends in opposite directions. The radial and longitudinal lines are shown on the shaft. The deformation of the shaft is shown with a counterclockwise segment of angle phi, angle of twist.

In summary, the relationship between applied torque T and shear stress τ is given by the torsion formula:

τmax=TcJ

and the angle of twist ϕ for a prismatic shaft with a circular cross section is found from the following equation:

ϕ=TLJG