一种估算谱载疲劳裂纹起始寿命的方法

提出了一种估算谱载疲劳裂纹起始寿命的等效载荷法，该法在变幅载荷的均方根算式中引入加权因子和修正系数来分别反映不同载荷变程和平均应力对变幅疲劳寿命的影响，并用相应获得的等幅载荷取代变幅载荷来估算谱载下的疲劳裂纹起始寿命．该法仅依赖于材料的等幅S-N曲线和单轴力学性能，不含任何待定参数，使用方便；两种材料3种谱载下15组变幅疲劳试验数据的评估结果显示，该法的平均寿命预测精度分别较同类型的Miner法则、修正Miner法则、均方根法提高了99．1％，24．6％和50．0％。

A SIMPLE AND PRACTICAL METHOD FOR ESTIMATION OF FATIGUE CRACK INITIATION LIFE UNDER SPECTRUM LOADING

This paper presents an equivalent load method for estimation of fatigue crack initiation life under spectrum loading. A weight factor and a coefficient of correction are added to the formula of root mean square of variable-amplitude-loading, respectively, to reflect influence of different loading range and mean stress upon variable-amplitude-fatigue life, and then the corresponding constant-amplitude-loading instead of the variable-amplitude-loading is used to estimate fatigue crack initiation life under spectrum loading. The method is easy to use as it only depends on constant-amplitude S-N curve and uniaxial mechanical property of the material and it does not contain any undetermined parameters. The results of fifteen sets of random fatigue test data under three spectrum types for two materials are compared with three parallel methods. Miner rule, modified Miner rule and Root-Mean-Square method, and the average life-prediction accuracy of the method is improved, respectively, by 99.1, 24.6 and 50.0 per cent.