Fatigue life under variable-amplitude loading according to the cycle-counting and spectral methods

We compare the values for the fatigue life of 12010.3 steel determined experimentally under variable-amplitude tension-compression and calculated by two methods in time and frequency ranges. The first method is based on the schematization of the loading history and uses the rainflow algorithm. The fatigue life was calculated according to the Serensen-Kogaev linear hypothesis of damage accumulation wit the use of the Manson-Coffin dependence. The second method is based on power spectral density functions. These methods differ in the approaches used for the determination of the probability density of amplitude distribution from the deformation history. It is established that, in the case considered, the values of fatigue life calculated by the cycle-counting method and by the spectral method are close to the values determined experimentally.