고체역학 (Beer) — Torsion: Problem 3.49

3.49 The electric motor exerts a torque of 800 N·m on the steel shaft ABCD when it is rotating at a constant speed. Design specifications require that the diameter of the shaft be uniform from A to D and that the angle of twist between A and D not exceed 1.5°. Knowing that \(\tau_{max} \leq 60 \text{ MPa}\) and \(G = 77.2 \text{ GPa}\), determine the minimum diameter shaft that can be used.