An aluminum bar has length L = 5 ft and diameter d = 1.25 in. The stress-strain curve for the aluminum is shown in Fig. 1-13 of Section 1.3. The initial straight-line part of the curve has a slope (modulus of elasticity) of 10 × 106 psi.
The bar is loaded by tensile forces P = 39 k and then unloaded.
(a) What is the permanent set of the bar?
(b) If the bar is reloaded, what is the proportional limit?