8) Pre Lab 1) At an axial load of 22 kN, a 15‐mm‐thick x 45‐mm‐ide polyimide polymer bar elongates 3.0 mm while the bar width contracts 0.25 mm. The bar is 200 mm long. At the 22‐kN load, the stress in the polymer bar is less than its proportional limit. Determine: a) The modulus of elasticity b) Poisson’s ratio c) The change in the bar thickness
2) A portion of the stress‐strain curve for a stainless steel alloy is shown in the figure. A 350‐mm‐long bar is loaded in tension until it elongates 2.0 mm and then the load is removed. a) What is the permanent set of the bar? b) What is the length of the unloaded bar?
3) A tensile specimen of stainless steel alloy having a diameter of 0.495 in and a gauge length of 2.00 in. was tested to fracture. Stress and strain data obtained during the test are shown in the figure. Determine: a) The modulus of elasticity b) The ultimate strength c) The Yield strength (0.20% offset) d) The fracture stress e) The true fracture stress if the final diameter of the specimen at the location of the fracture was 0.350 in.