고체역학 (Beer) — Pure Bending: Problem 4.91

4.91 A bending couple is applied to the beam of Prob. 4.73, causing plastic zones 30 mm thick to develop at the top and bottom of the beam. After the couple has been removed, determine (a) the residual stress at \(y = 45\text{ mm}\), (b) the points where the residual stress is zero, (c) the radius of curvature corresponding to the permanent deformation of the beam. Reference to Prob. 4.73: A beam of the cross section shown is made of a steel that is assumed to be elastoplastic with \(E = 200\text{ GPa}\) and \(\sigma_Y = 240\text{ MPa}\). The cross section is rectangular with width \(b = 60\text{ mm}\) and height \(h = 90\text{ mm}\).