Evaluation of fatigue life via stress and strain damage criterions

Attempts to describe the effect of the variable amplitude loading character on fatigue damage accumulation are made for a structural steel element. We show the possibility of durability prediction of steel taking into account stress and strain parameters of stationary cyclic loading and parameters that describe the range of random loading. It is proposed to quantify the influence of the loading character on durability by a damage model with the nonstationarity factor and spectrum fullness factor. The accuracy of the model is analyzed on the basis of steel 40Cr tests. The experimental evidence and analytical results of the proposed model are correlated.