考虑尺寸效应的缺口疲劳寿命预测方法

A life prediction method for size effects on notched fatigue

利用试样缺口根部归一化应力的分布规律,在考虑应力梯度的缺口疲劳寿命预测方法的基础上,着重考虑尺寸效应对缺口疲劳寿命的影响,构建了综合考虑平均应力、应力梯度和尺寸效应的缺口疲劳寿命预测方法.利用已有的TC4合金缺口疲劳试验数据对所发展的方法进行了验证,并与常用的几种局部应力应变法的寿命预测结果进行了对比分析.结果表明:所对比的几种局部应力应变法的寿命预测结果过于保守,而所发展的缺口疲劳寿命预测方法的预测结果几乎全在3倍分散带以内,且大多数预测结果在2倍分散带以内.

By use of the normalized stress distribution at the notch root of a specimen, and based on a notched fatigue life prediction method with consideration of the effects of stress gradient, a life prediction method for fatigue of notched specimen was constructed by taking mean stress, stress gradient and size effect into account with focus on the influence of size effect on the fatigue life of notched specimen. The developed method was verified by use of fatigue test data of TC4 alloy notched specimen, and the prediction results were comparatively analyzed with those of several commonly-used local stress-strain approaches, indicating that those local stress-strain approaches over-conservatively predicted the fatigue life of notched specimen. The developed method can predict the result more precisely with almost all the prediction results within the scatter band of 3 and more than three quarters of the re- sults within the scatter band of 2.