Prediction of variable amplitude fatigue crack growth life based on modified grey model

Grey model has been several applications on fatigue crack, with prediction on fatigue crack growth life curve often serving as milestones. A typical difficulty in predicting the fatigue crack growth life curve is the retardation of crack growth caused by the overload effect. Overload retardation, resulting in the lack of experiment data points in the retardation interval and the deflection of crack growth curve, is a long-term challenge for predicting fatigue crack growth. We improve the ability of grey model to predict fatigue crack growth life by second order B-spline interpolation, an interpolation for local data points. It combines the trend of local data point to deal with the retardation interval, and interpolates multiple data points in the retardation interval when there is a lack of local data, and uses a metabolic grey model to construct the prediction formula of crack growth. In the study involving variable amplitude load and multiple overload fatigue crack growth experiments, the proposed method is proved to improve, with statistical significance, the predictive ability on the whole range of experiment data. The method is simple and accurate. Consequently, it is conducive to solve the problem of fatigue crack growth life of engineering structure.