고체역학 (Beer) — Stress and Strain—Axial Loading: Problem 2.108

2.108 For the composite rod of Prob. 2.107, if P is gradually increased from zero until the deflection of point C reaches a maximum value of \(\delta_m = 0.3 \text{ mm}\) and then decreased back to zero, determine (a) the maximum value of P, (b) the maximum stress in each portion of the rod, (c) the permanent deflection of C after the load is removed. Data from Prob. 2.107: Rod AB consists of two cylindrical portions AC and BC, each with a cross-sectional area of \(1750 \text{ mm}^2\). Portion AC is made of a mild steel with \(E = 200 \text{ GPa}\) and \(\sigma_Y = 250 \text{ MPa}\), and portion BC is made of a high-strength steel with \(E = 200 \text{ GPa}\) and \(\sigma_Y = 345 \text{ MPa}\). The lengths of portions AC and BC are both \(190 \text{ mm}\). A load P is applied at C pointing downwards.