A structural member must be able to support repeated tension-compression loads (load amplitude is 66800 N, R=-1) without experiencing a fatigue fracture for at least 100 000 cycles. The structure should be as light as possible. Which of the given materials (whose properties and S-N diagrams are given below) would you select for this application to meet these criteria? Show all your derivations and calculations. 1MPa 10 N/m. (Hint: first derive an equation for the weight) ALLOY 1045 Steel 2014-T6 Al Alloy Red Brass Stress amplitude, S (MPa) 500 400 300 200 100 0 10 Yield Strength (MPa) 660 300 280 104 105 E(MPa) 210,000 70,000 100,000 1045 steel Density(g/cm) 7.9 2.7 8.6 2014-T6 aluminum alloy Red brass 106 107 108 Cycles to failure, N 10 80 70 60 50 40 30 20 10 0 100