고체역학 (Beer) — Stress and Strain—Axial Loading: Problem 2.65

2.65 In a standard tensile test, an aluminum rod of 20-mm diameter is subjected to a tension force of \( P = 30 \text{ kN} \). Knowing that \( \nu = 0.35 \) and \( E = 70 \text{ GPa} \), determine (a) the elongation of the rod in a 150-mm gage length, (b) the change in diameter of the rod.