고체역학 (Beer) — Stress and Strain—Axial Loading: Problem 2.116

2.116 A uniform steel rod of cross-sectional area \( A \) is attached to rigid supports and is unstressed at a temperature of \( 45^\circ\text{F} \). The steel is assumed to be elastoplastic with \( \sigma_Y = 36\text{ ksi} \) and \( E = 29 \times 10^6\text{ psi} \). Knowing that \( \alpha = 6.5 \times 10^{-6}/^\circ\text{F} \), determine the stress in the bar (a) when the temperature is raised to \( 320^\circ\text{F} \), (b) after the temperature has returned to \( 45^\circ\text{F} \).