고체역학 (Gere) — Axially Loaded Members: Problem 2.7-2

2.7-2 A bar with a circular cross section having two different diameters \(d\) and \(2d\) is shown in the figure. The length of each segment of the bar is \(L/2\), and the modulus of elasticity of the material is \(E\). (a) Obtain a formula for the strain energy \(U\) of the bar due to the load \(P\). (b) Calculate the strain energy if the load \(P = 27 \text{ kN}\), the length \(L = 600 \text{ mm}\), the diameter \(d = 40 \text{ mm}\), and the material is brass with \(E = 105 \text{ GPa}\).