b) Below diagram depicts the Whler-curve (S/N-curve) of a 4340 low-alloy steel. Describe the applied stress scenario with the help of the indicated stress ratio. (5P) 1500 1400 1300 1200 1100 1000 900 800 700 600 Stress amplitude, oa (MPa) 500 400 102 103 104 105 4340 Low-alloy steel, quenched and tempered 425C R: min = Stress ratio R = -1 10 Number of cycles to failure, Nf 107 108 max D= => ni N c) Calculate damage D after 1,000 cycles at 1,200 MPa and additional 10,000 cycles at 750 MPa. What do you conclude from your result? (6 P)