A circular tube of outer diameter d3 = 70 mm and inner diameter d2 = 60 mm is welded at the right-hand end to a fixed plate and at the left-hand end to a rigid end plate (see figure). A solid circular bar of diameter d1 = 40 mm is inside of, and concentric with, the tube. The bar passes through a hole in the fixed plate and is welded to the rigid end plate.
The bar is 1.0 m long and the tube is half as long as the bar. A torque T = 1000 N ( m acts at end A of the bar. Also, both the bar and tube are made of an aluminum alloy with shear modulus of elasticity G = 27 GPa.
(a) Determine the maximum shear stresses in both the bar and tube.
(b) Determine the angle of twist (in degrees) at end A of the bar.

Tube Fixed plate End plate Bar Tube Bar