A solid steel bar of diameter d1 = 25.0 mm is enclosed by a steel tube of outer diameter d3 = 37.5 mm and inner diameter d2 = 30.0 mm (see figure). Both bar and tube are held rigidly by a support at end A and joined securely to a rigid plate at end B. The composite bar, which has a length L = 550 mm, is twisted by a torque T = 400 N ( m acting on the end plate.

(b) Determine the angle of rotation ( (in degrees) of the end plate, assuming that the shear modulus of the steel is G = 80 GPa.
(c) Determine the torsional stiffness kT of the composite bar. (Use Eqs. 3-44 a and b to find the torques in the bar and tube.)

T2