6 Questions on Engineering Science - Quiz 4 | ENSC 3313, Quizzes of Materials science

Download 6 Questions on Engineering Science - Quiz 4 | ENSC 3313 and more Quizzes Materials science in PDF only on Docsity! ENSC 3313, Fall 2011 Quiz 4 -KEY Name __________________ Answer ONLY 4 of the following 6 questions. Show all work. 1 point each Grade:______/4 1. A 0.5" diameter 1040 steel bar is subjected to a 2,000 lbf load. Calculate the maximum tensile stress in the bar and the lateral strain of the bar after application of the load based on the following properties for this steel: E=29×106 psi, UTS=74700 psi, YS=50750 psi, Poisson's ratio 29.0 z x = ε ε −=ν . Cross sectional area: 164 dA 2 π → π = , therefore: psi185,10000,32 A P = π ==σ The axial strain is: 0004.0 1029 000,32 E 6z ≈ ×⋅π = σ =ε , therefore: 0001.029.0 zx ≈ε−=ε Note: if the bar was 10" long initially, it would only elongate by 0.004" and thin by 0.0005" regardless of length. 2. The stress-strain plot is from a cylindrical specimen of 4 inch gauge length and diameter of 0.5”. Determine a) the force at yielding (use the 0.5% offset method), b) the elastic modulus, and c) the maximum force this specimen can support before failure. Calculate all loads in units of lbf or ksi. Note: inset is the magnified low strain region. cross sectional area is A = π (0.25) 2 = 0.2 in2 ∴ force = stress / 5 (a) Draw a vertical line from 0.005 strain. YS~150 ksi. Thus, the load is P = 30,000 lbf (b) At a strain of 0.005, the stress is 150 ksi so E=150/0.005=30x106 psi (c) Drawing a horizontal line from the max in the stress- strain curve over to the stress axis, I read: TS~280,000 psi. Thus, the maximum supportable load is Pmax = A×TS = 56,000 lbf 3. What two items did I show on the overhead projector on Tuesday to demonstrate the use of gauge marks for strain measurement? A rubber band with two lines drawn on it and a broken metal sample with gauge mark indents. ~1600 MPa (232x103 psi) ~1950 MPa (~280,000 psi)