고체역학 (Beer) — Pure Bending: Problem 4.71

4.71 The prismatic rod shown is made of a steel that is assumed to be elastoplastic with \(E = 200\text{ GPa}\) and \(\sigma_Y = 280\text{ MPa}\). Knowing that couples \(\mathbf{M}\) and \(\mathbf{M}'\) of moment \(525\text{ N}\cdot\text{m}\) are applied and maintained about axes parallel to the \(y\) axis, determine (a) the thickness of the elastic core, (b) the radius of curvature of the bar.