1. Failure [20 points] a. This type of failure is responsible for 90% of all service failures: fatiguo/creep/fracture (p

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1 Failure 20 Points A This Type Of Failure Is Responsible For 90 Of All Service Failures Fatiguo Creep Fracture P 1 (49.54 KiB) Viewed 24 times

1 Failure 20 Points A This Type Of Failure Is Responsible For 90 Of All Service Failures Fatiguo Creep Fracture P 2 (43.12 KiB) Viewed 24 times

1 Failure 20 Points A This Type Of Failure Is Responsible For 90 Of All Service Failures Fatiguo Creep Fracture P 3 (37.55 KiB) Viewed 24 times

1. Failure [20 points] a. This type of failure is responsible for 90% of all service failures: fatiguo/creep/fracture (pick one) [1 point]. Flaws in objects are referred to as Raisers [1 point]. b. Draw brittle and moderately ductile fracture surfaces. [3 points] c. A structural component is fabricated from an alloy that has a plane-strain fracture toughness of 62 MPam. It has been determined that this component fails at a stress of 250 MPa when the maximum length of a surface crack is 1.6 mm. What is the maximum allowable surface crack length (in mm) without fracture for this same component exposed to a stress of 250 MPa and made from another alloy that has a plane strain fracture toughness of 51 MPa√m? [5 points].
d. The fatigue data for a steel alloy are given as follows: Stress Amplitude [MPa (ksi)] Cycles to Failure 470 (68.0) 10 440 (63.4) 3 x 10¹ 105 390 (56.2) 350 (51.0) 3 x 105 310 (45.3) 10⁰ 290 (42.2) 3 x 10° 290 (42.2) 107 290 (42.2) 10⁰ (1) Make an S-N plot (stress amplitude versus logarithm of cycles to failure) using these data. (2) What is the fatigue limit for this alloy? (3) Determine fatigue lifetimes at stress amplitudes of 415 MPa (60,000 psi) and 275 MPa (40,000 psi). (4) Estimate fatigue strengths at 2 x 104 and 6 x 105 cycles. [2 points for (1) and 1 point each for the rest, Total= 5 points]
e. A cylindrical rod of diameter 14.7 mm fabricated from a 2014-T6 Aluminum alloy (characteristics shown below) is subjected to a repeated tension-compression load cycling along its axis. Compute the maximum and minimum loads that will be applied to yield a fatigue life of 1.0 x 106 cycles. Assume that data in figure below were taken for repeated axial tension-compression tests, that stress plotted on the vertical axis is stress amplitude, and data were taken for a mean stress of 50 MPa. [5 points). UCF 80 70 Stress amplitude, S (MP) 500 400 300 200 100 0 10³ 10 105 1045 steel 2014-T6 aluminum alloy Red brass LE 10% Cycles to failure, N 60 889 50 40 30 20 10 lo 10' 10⁰ 10⁰ 1010 Stress amplitude (10³)