Geometry of Deformation  
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Diagram shows a shaft A B with aluminum segment marked 1 of length 1,000 millimeters inside which is a brass shaft marked 2. Both the shafts are centered on the central axis x. A torque T is applied at B.

Torque T applied at end B causes both shafts to twist. While the support prevents rotation at A, the shaft rotates through an angle of ϕB at the free end.