ME 111L Lab Unit 1 part 2

# ME 111L Lab Unit 1 part 2 - about.2 of the true strain at...

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In general, the true strain at the onset of necking is slightly greater than the engineering strain at the onset of necking. This is because the true strain takes into account the slightly decreasing cross sectional area. At the onset of necking, the engineering strain is given by the equation ε = (l-ln )/ln . And the true strain is given by the equation ε t = ln(1+ε). The strain hardening exponent(n) for each steel is approximately equal to its true strain at the onset of necking. From the four lab sections data, the average of the strain hardening exponent(n) for 1018 HR is about .21, which is very close to the approximate value of
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Unformatted text preview: about .2 of the true strain at the onset of necking. For 1018 CD, the n value of about .04 is very close to the true strain value at the onset of necking of about .03. The 1045 HR value of n and true strain are about .22 and .12 respectively, differing only by about a tenth. And the 304 SS’ values for n and true strain at onset of necking are about .38 and 1.05, respectively. The 304 SS’ true strain at onset of necking is about 64% greater than its strain hardening exponent....
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