Accumulation of fatigue damage and lifetime prediction under irregular loading conditions with overloads and random cycle asymmetry

The prediction of service life with an experimentally established relation for correcting the magnitude of cumulative fatigue damage on overloads is discussed. The results of block loading tests of cylindrical aluminum alloy specimens with different stress concentrators were used to quantitatively estimate the effect of cycle asymmetry of basic loading and overload steps on the lifetime. It was demonstrated how the lifetime decreased in passing from block to random variations of loading conditions. It is shown that the estimation of service life can be based on experimental models for the correction of cumulative damage under random loading conditions simulating the operating ones.