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HW _2 Solutions

HW _2 Solutions - σ [email protected] = 58.5 ksi(see graph below(f...

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CE 3020 Construction Materials HOMEWORK 3 Dr. Kurtis SOLUTIONS Question 1 The following engineering tensile stress-strain data were obtained for a 0.2% C plain-carbon steel. Engineering Stress (ksi) Engineering Strain (%) 0 30 55 60 68 72 74 75 76 75 73 69 65 56 51 0 0.1 0.2 0.5 1.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 19.0 (fracture) (a) Plot the engineering stress-strain curve, with stress in units of ksi and strain expressed as a %. ANS.

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(b) Determine the ultimate tensile strength of the alloy. ANS. From data or graph, σ ult = 76ksi (c) Determine the percent elongation at fracture. ANS. 19% (d) Calculate the elastic modulus of the alloy. E = (30ksi-0)/(0.1x100-0) = 30 x 10 3 ksi which is typical for steel. (e) Determine the 0.2% offset yield stress of the alloy.
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Unformatted text preview: σ [email protected]% = 58.5 ksi (see graph below) (f) Make a good estimate the toughness of the alloy. Toughness = area under the stress-strain curve ≈ area region 1 + area region 2 + area region 3 + area region 4 = (50,000 psi x 0.19 in/in) + (1/2 x 12,000 psi x 0.02 in/in) + (1/2 x 13,000 psi x 0.07 in/in) + (12,000 psi x 0.10 in/in) = 11,300 in-lbs/in 3 although estimates may vary with the precision of the method for measuring the area under the curve in part A. (g) On the graph you have made, schematically show the effect of loading from 0 ksi to 68 ksi, and then unloading completely. ANS. see graph in part D. (h) Estimate the plastic strain experienced due to the loading scenario described in question 1.g. ANS. 0.7% (see graph in part D)...
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