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exam2fall01

# exam2fall01 - ENSC 3313 Fall 2001 Name TEST 2'Answer alll O...

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Name ENSC 3313, Fall 2001 TEST 2 .'- Answer alll O Questions. 2 points each. ,\$-"' Shown is the load-elongation plot for a tensile specimen of circular cross section, 0.25 inches diameter and 1.0 inches gauge length. Determine the a) tensile strength (ksi), b) yield strength (ksi), c) elastic modulus, and d) strain at fracture. 1 Cross sectional area = 7t(0.25)2/4 = 0.049 in2 * Stress = Load/O.O49! * One inch gauge length, so elongation equals strain. * Hence a) TS = 1300/0.049 -26.5 ksi b) YS(0.5% extension) -850/0.049 -17.4 ksi c) (500/0.049)/0.002 = 5 x 106 Rsi d) Read off plot, -~ 0. b o.~ o'~ ~LUI'4GA7'oN. ;,.r Lt.. / Tell about the Rockwell B (HRB) hardness test! a) What is the indenter? b) What is the load? c) What is the hardness measured in terms of? d) Deduce why there are other Rockwell scales besides B. 2. a) A 1/16" diameter hard steel sphere b) 100 kg c) depth of penetration d) For soft materials, would need a lower load and/or a larger diameter penetrator; for hard materials, would need a diamond indenter and a large load. Machine won't work if penetration is too much or too little. Also, indenter must not deform.

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The starting material is a 10 mm diameter rod of ~ brass (85Cu -15Zn) of HRB 80. Required is an ~ diameter rod ofHRB 70. Describe an appropriate processing sequence. (,(0 3 ~ , ~ .,...1 HRB 70 signifies a final processing stage of ~ 32% CW.
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