A machine part will be cycled at ±48 kpsi for 4 (103) cycles. Then the loading will be changed to ±38 kpsi for 6 (104) cycles. Finally, the load will be changed to ±32 kpsi. How many cycles of operation can be expected at this stress level? For the part, Sut = 76 kpsi, f = 0.9, and has a fully corrected endurance strength of Se = 30 kpsi.
(a) Use Miner’s method.
(b) Use Manson’s method.