Review of Fatigue Crack Propagation under Variable Amplitude Loading

Mechanical structures mainly bear fatigue loading, especially variable amplitude loading in the engineering. In this article, the current frequently-used crack propagation models and theories under variable amplitude loading were analyzed in detail, including induced plastic closure theory, crack tip passivation theory and residual compressive stress theory. The current frequently-used models can obtain relatively accurate results in predicting single or multimodal overload fatigue crack propagation life. But in high load ration and taking the component thickness effects into account, there tend to be big errors. Every model has its own basis of theory, premise condition and application area. In the practical engineering application, proper models should be chosen according to different conditions. The prediction accuracy of the models under high load ration or large scale yielding of crack tip will be emphasized in the future. Based on this paper, the readers can know about the application area of the prediction models and their simplified versions so that proper models can be used to obtain relatively accurate results.