Nonlinear fatigue life prediction models based on material damage state correction

The determination of the interaction factor of adjacent loads under variable amplitude loading is difficult. In this paper, two new nonlinear accumulation damage models are proposed based on the material damage state. Besides considering loading sequence, load interference, and mean stress effect, the proposed models consider the effect of material damage state and then modify the key parameter δ by introducing the load cycle ratio and the amount of material memory degradation in order to express the damage state. Verifying by different materials’ test data and comparing with the existing models shows the proposed models good predictive ability and reliability. Further, in this method, there are no new variables introduced, no complex nested calculations, and only one conventional parameter that is easy to obtain by experimental fitting. Furthermore, the proposed models are convenient for fatigue life prediction in practical engineering problems.