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Unformatted text preview: 1 92-411 Machine Design Winter 2009 Department of Mechanical, Automotive, and Materials Engineering 92-411: Machine Design I 2 Chapter 2: Materials | Selection of part material and manufacturing process is the responsibility of the design engineer z Selection usually made before part dimensions are established z Material properties are necessary for estimating part stress and deflection z Other factors: aesthetics, corrosion, temperature 92-411: Machine Design I Figure 2-1 3 Chapter 2: Materials | Standard tensile test determines material characteristics 2 : strain normal , 4 1 : stress l l l d P A P = = = 92-411: Machine Design I Figure 2-2 4 Chapter 2: Materials | Plot resulting stress-strain relationship Ductile Brittle 2 92-411: Machine Design I Figure 2-2 5 Chapter 2: Materials | pl: proportional limit | el: elastic limit | y: yield point | u: point of ultimate strength | f: fracture point 92-411: Machine Design I Figure 2-3 6 Chapter 2: Materials | Engineering stress , , and engineering strain , , are calculated with original dimensions z Lower than true values | True stress , t , and true strain , t , are calculated with current dimensions z True strain (logarithmic strain): = = l l t l l l dl ln 92-411: Machine Design I Figure 2-4 7 Chapter 2: Materials t- t diagram Note that the true value of f > u , unlike S f < S u in Figure 2-2 92-411: Machine Design I 8 Chapter 2: Materials | Compressive tests use samples of a different geometry because of buckling and to more evenly distribute the stresses | Usually, compressive and tensile...
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This note was uploaded on 09/19/2009 for the course ME 416 taught by Professor Kauzmania during the Spring '09 term at Windsor.
- Spring '09
- Machine Design