Question 1 (a) A cylindrical 1045 steel rod is subjected to repeated compression-tension stress cycling along its axis. The S-N curve of 1045 steel is shown in Figure Q1. Apply the data given in Figure Q1 to compute the minimum allowable rod diameter to ensure that fatigue failure will not occur, given that the load amplitude is 66,700 N. Stress amplitude (MPa) 500 400 80 Stress amplitude (10 psi) 28 70 60 20 1045 steel 50 300 40 2014-T6 aluminum alloy 30 200 100 Red brass 10 0 10 10 10% 105 10% 107 10 10 100 Cycles to failure, N Figure Q1 (5 marks) (b) (c) A cylindrical 2014-T6 aluminum alloy rod with a diameter of 6.4 mm is subjected to a stress cyclic loading with a zero stress ratio. The ultimate tensile strength of 2014-T6 aluminum alloy is 400 MPa and its yield strength is 365 MPa. Interpret Figure Q1 and apply Basic Goodman diagram to calculate the maximum allowable axial stress (in MPa) that can be applied to this rod such that its fatigue life is 1106 cycles. (8 marks) A bar with a rectangular cross-section measuring 30 mm by 20 mm is fabricated from red brass and is subjected to a compression-tension stress cycle along its axis. The S-N curve for red brass is plotted in Figure Q1. (i) Given that a mean stress of 0 MPa is applied, describe its loading characteristics by determining if it is a reversed stress cycle loading. State its stress ratio. (2 marks) Calculate the maximum load and minimum load (in kN) that can be applied to yield a fatigue life of 1105 cycles. (10 marks)