High cycle fatigue data for an alloy at various alternating stresses, 𝜎a (see figure) is given below.
A specimen of this alloy is subjected to multiple stress cycles sequentially in the following order: (i) first 5000 cycles at σa = 400 MPa followed by (ii) 25000 cycles at σa = 300 MPa and finally (iii) at σa = 500 MPa. Assuming that Miner’s law is obeyed, the number of cycles to failure at the final applied stress of
500 MPa is .
