Problem 2-5 - 1 2 Sy Nylon 2 E Nylon . U RNylon 1.8 MN m ....

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MACHINE DESIGN - An 2-5-1 PROBLEM 2-5 Statement: Which of the thermoplastic polymers shown in Figure 2-22 would you choose to obtain (a) Maximum strength (b) Maximum modulus of resilience (c) Maximum modulus of toughness (d) Maximum stiffness Units: ksi 10 3 psi . MPa 10 6 Pa . GPa 10 9 Pa . MN 10 6 newton . Solution: See Figure 2-22 and Mathcad file P0205. 1. Determine, from the graph, values for yield strength, ultimate strength, strain at fracture, and modulus of elasticity for each material. Plastic Yield Strength Ultimate Strength Fracture Strain Mod of Elasticity Nylon 101: Sy Nylon 63 MPa . Sut Nylon 80 MPa . ε f Nylon 0.52 E Nylon 1.1 GPa . HDPE: Sy HDPE 15 MPa . Sut HDPE 23 MPa . f HDPE 3.0 E HDPE 0.7 GPa . PTFE: Sy PTFE 8.3 MPa . Sut PTFE 13 MPa . f PTFE 0.51 E PTFE 0.8 GPa . 2. From the values of S ut above it is clear that the Nylon 101 has maximum strength . 3. Using equation (2-7) and the data above, determine the modulus of resilience. U RNylon
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Unformatted text preview: 1 2 Sy Nylon 2 E Nylon . U RNylon 1.8 MN m . m 3 = U RHDPE 1 2 Sy HDPE 2 E HDPE . U RHDPE 0.16 MN m . m 3 = U RPTFE 1 2 Sy PTFE 2 E PTFE . U RPTFE 0.04 MN m . m 3 = Even though the data is approximate, the Nylon 101 clearly has the largest modulus of resilience. 4. Using equation (2-8) and the data above, determine the modulus of toughness. U TNylon 1 2 Sy Nylon Sut Nylon . f Nylon . U TNylon 37 MN m . m 3 = U THDPE 1 2 Sy HDPE Sut HDPE . f HDPE . U THDPE 57 MN m . m 3 = U TPTFE 1 2 Sy PTFE Sut PTFE . f PTFE . U TPTFE 5 MN m . m 3 = Even though the data is approximate, the HDPE has the largest modulus of toughness. 5. The Nylon 101 has the steepest slope in the (approximately) elastic range and is, therefore, the stiffest of the three materials. . P 0205.mcd...
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This note was uploaded on 04/26/2010 for the course MAE 3242 taught by Professor N/a during the Spring '10 term at University of Texas-Tyler.

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