고체역학 (Gere) — Torsion: Problem 3.3-6

3.3-6 When drilling a hole in a table leg, a furniture maker uses a hand-operated drill (see figure) with a bit of diameter \(d = 4.0 \text{ mm}\). (a) If the resisting torque supplied by the table leg is equal to \(0.3 \text{ N} \cdot \text{ m}\), what is the maximum shear stress in the drill bit? (b) If the allowable shear stress in the drill bit is \(32 \text{ MPa}\), what is the maximum resisting torque before the drill binds up? (c) If the shear modulus of elasticity of the steel is \(G = 75 \text{ GPa}\), what is the rate of twist of the drill bit (degrees per meter)?