A round bar having a length of 1.2 m and a diameter of 6 mm is made of an aluminum alloy for which the stressstrain diagram can be described mathematically by the following equation:
in which σ has units of megapascals (MPa). The shape of this stress-strain diagram is shown in the figure. The bar is axially loaded by tensile forces P = 12.5 kN, after which the loads are removed. What is the permanent set of the bar?
