考虑过载效应的金属材料疲劳裂纹扩展试验数据拟合及疲劳裂纹扩展速度计算方法研究

提出一种拟合金属材料疲劳裂纹扩展试验数据,并计算疲劳裂纹扩展速度的通用方法。该方法采用递增的三次多项式函数拟合疲劳试验数据,并采用平均加权方式计算各局部函数拟合的结果,提高了试验数据的拟合精度和疲劳裂纹扩展速度的准确性。通过在疲劳裂纹长度和扩展速度拟合结果的加权计算过程中引入delta函数,该通用方法能够有效地拟合常幅和存在过载载荷的疲劳裂纹扩展试验数据,并计算各试验点的裂纹扩展速度,同时保证了三次多项式拟合过程的连续性。通过多组常幅和存在过载载荷的疲劳试验数据拟合和现有方法及扩展有限元预测结果的对比分析,验证了该通用方法的有效性。

Research on the Curve Fitting of Fatigue Test Data and Computation of Fatigue Crack Growth Rates of Metals in Consideration of the Retardation Effect

A general approach of curve fitting of fatigue test data and calculation of fatigue crack growth rates is developed in the preceding paper.The approach uses five points incremental cubic function to fit the fatigue test data and adopts the average weighted method to deal with the fitting results,which improves the fitting accuracy of fatigue crack length and fatigue crack growth rates significantly.Furthermore,the delta function is introduced in the average process of fitting results to account for the retardation effect due to overloads,which makes the general approach be suitable for fitting the fatigue test data under constant amplitude loading and constant amplitude loading with interval overloads and guarantees the continuity of the fitting process.Several sets of fatigue test data and predictions of the existing approach and the extended finite element method are used to demonstrate the correctness and validity of the general approach,which shows great consistency.