The thin-walled tube AB is fixed at end A with a torque applied at the free end B. Determine the average shear stress developed at
points C and D. Also calculate the angle of twist Φ at B.

The thin-walled tube AB is fixed at end A with a torque applied at the free end B. Determine the average shear stress developed at
points C and D. Also calculate the angle of twist Φ at B.