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Fatigue Life Prediction for High Strength AI-alloy under Variable Amplitude Loading

변동하중하에서 고강도 알루미늄 합금의 피로수명 예측

  • Published : 2000.08.01

Abstract

In this study, to investigate and to predict the crack growth behavior under variable amplitude loading, crack growth tests are conducted on 7075-T6 aluminum alloy. The loading wave forms are generated by normal random number generator. All wave forms 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 previous study, the load interaction effect is considered. The variability in crack growth process is described by the random variable Z which was obtained from crack growth tests under constant amplitude loading in previous work. 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.

Keywords

Fatigue Crack Growth;Variable Amplitude Loading;Random Variable;Retardation Coefficient;Variability;Normal Distribution

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