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Homework 9 - 1 ENMA 300/ENME 382 HW 9 The fatigue data for...

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ENMA 300/ENME 382 HW 9 Due November 21 1. The fatigue data for a steel alloy are given as follows: Stress Amplitude [MPa (ksi)] Cycles to Failure 470 (68.0) 440 (63.4) 390 (56.2) 350 (51.0) 310 (45.3) 290 (42.2) 290 (42.2) 290 (42.2) 1.0 × 10 4 3.0 × 10 4 1.0 × 10 5 3.0 × 10 5 1.0 × 10 6 3.0 × 10 6 1.0 × 10 7 10 8 a. Make an S-N plot (stress amplitude versus logarithm cycles to failure) using these data. b. What is the fatigue limit for this alloy? c. Determine the fatigue lifetimes at stress amplitudes of 415 MPa (60,000 psi) and 275 MPa (40,000 psi). d. Estimate the fatigue strengths at 2 x 10 4 and 6 x 10 5 cycles. 2a. A relatively large plate of glass is subjected to a tensile stress of 40 MPa. If the specific surface energy and modulus of elasticity for this glass are 0.3 J/m 2 and 69 GPa, respectively, determine the maximum length of surface flaw that is possible without fracture. b. A structural component in the form of a wide plate is to be fabricated from a steel alloy that has a plane strain fracture toughness of 98.9 MPa √m (90Ksi in ) and yield strength of 860 MPa (125,000 psi). The flaw size resolution limit of a
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