When there is no load on the two-segment bar in Fig. P3.11-6, there is a 1-mm gap between the bar and the rigid wall at C. The two-segment rod is made of linearly elastic, perfectly plastic material with a stress-strain diagram like
(a) Determine the value of P, say PR, where the right end of the bar initially makes contact with the rigid wall at C. Determine the displacement uR of node B that corresponds to the load PR. (b) Determine the load PY at which first yielding occurs, and determine the corresponding displacement uY of section B where the load P is applied. (c) Determine the load PU at which yielding occurs in the remaining segment of the bar, and determine the corresponding displacement, uU, of section B. (d) Sketch a load-displacement diagram, that is, sketch a diagram of P versus u up to PU.