Suppose a plastic material can have its creep behaviour described by a Maxwell model is to be subjected to the stress history as shown in Figure 1 below. If the spring and dashpot constants for the model are ξ : 20 GPa and η 1000 GPa.s respectively, predict the strains in the material after 150s, 250s, 350s, and 450s. Plot the predicted strain response for the time period shown in Figure 1

20 15 10 100 200 300 400 500 Time (s) Figure 1: Applied stress history. Stress (MPa)