고체역학 (Gere) — Torsion: Problem 3.2-3

3.2-3 A copper rod of length \( L = 460 \text{ mm} \) is to be twisted by torques \( T \) (see figure) until the angle of rotation between the ends of the rod is \( 3.0^\circ \). (a) If the allowable shear strain in the copper is \( 0.0006 \text{ rad} \), what is the maximum permissible diameter of the rod? (b) If the rod diameter is \( 12.5 \text{ mm} \), what is the minimum permissible length of the rod?