Diagram shows a shaft with brass segment A B of length 1800 millimeters which is connected to aluminum segment B C of length 800 millimeter using a flange at B and a torque T of 50 Newton meter is applied on C. The x axis is taken along the axis of the cylinders and the y axis is taken along the rigid support at A and perpendicular to the x axis.

For the compound torsion member considered here, the internal torque T is the same in both segments. However, J and G are different in segments (1) and (2).

To compute the rotation angle at C relative to A, we must consider the twist of each segment separately and sum the results according to:

ϕ=TLJGi