고체역학 (Beer) — Torsion: Problem 3.86

3.86 Knowing that the stepped shaft shown transmits a torque of magnitude \( T = 2.50 \text{ kip}\cdot\text{in.} \), determine the maximum shearing stress in the shaft when the radius of the fillet is (a) \( r = \frac{1}{8} \text{ in.} \), (b) \( r = \frac{3}{16} \text{ in.} \)