고체역학 (Beer) — Torsion: Problem 3.94

3.94 A 2-in.-diameter solid shaft is made of a mild steel that is assumed to be elastoplastic with \(\tau_Y = 20 \text{ ksi}\). Determine the maximum shearing stress and the radius of the elastic core caused by the application of a torque of magnitude (a) 30 kip·in., (b) 40 kip·in.