A Stochastic Modeling for Predicting Fatigue Crack Growth under Variable Amplitude Loading

摘要

In this study, to investigate and to predict the crack growth behavior under variable amplitude loading, crack growth tests are conducted on 7575-T6 aluminum alloy. The loading waveforms are generated by normal random number generator. All waveforms have same average and RMS(root mean square) value, but different standard deviation, which is to vary the maximum load in each wave. The modified Forman's equation is used as crack growth equation. Using the retardation coefficient D defined in the previous study, the load interaction effect is considered. The variability in crack growth process is described by the random variable Z that was obtained from crack growth tests under constant amplitude loading. From these, a statistical model is developed. The curves predicted by the proposed model well describe the crack growth behavior under variable amplitude loading and agree with experimental data. In addition, this model well predicts the variability in crack growth process under variable amplitude loading.