A machine part will be cycled at ±350 MPa for 5 (103) cycles. Then the loading will be changed to ± 260 MPa for 5 (104) cycles. Finally, the load will be changed to ±225 MPa. How many cycles of operation can be expected at this stress level? For the part, Sut = 530 MPa, f = 0.9, and has a fully corrected endurance strength of Se = 210 MPa.
(a) Use Miner’s method.
(b) Use Manson’s method.