고체역학 (Beer) — Torsion: Problem 3.109

3.109 The magnitude of the torque T applied to the tapered shaft of Prob. 3.108 is slowly increased. Determine (a) the largest torque that may be applied to the shaft, (b) the length of portion BE that remains fully elastic. (Note: From Prob 3.108, the shaft is made of mild steel assumed to be elastoplastic with \(\tau_Y = 21\) ksi. The diameters are \(d_{AB} = 2.5\) in. and \(d_{CD} = 2.0\) in., and the length of the tapered portion \(BC\) is 4 in.)