고체역학 (Beer) — Pure Bending: Problem 4.95

4.95 The prismatic bar \(AB\) is made of a steel that is assumed to be elastoplastic and for which \(E = 200 \text{ GPa}\). Knowing that the radius of curvature of the bar is \(2.4 \text{ m}\) when a couple of moment \(M = 350 \text{ N}\cdot\text{m}\) is applied as shown, determine (a) the yield strength of the steel, (b) the thickness of the elastic core of the bar.