考虑应力松弛的缺口疲劳寿命预测方法

Method for Fatigue Life Prediction of Notched Specimen with Considered Stress Relaxation

关键词:  缺口疲劳  粘塑性本构方程  循环应力应变  局部应力应变  应力松弛

Key words:  Notch fatigue  Viscoplastic constitutive model  Cyclic stress-strain  Local stress strain  Stress relaxation

摘要:

为了能够快速准确获得循环载荷条件下缺口局部应力应变并用于缺口疲劳寿命预测，基于粘塑性本构方程及光滑试样循环应力应变试验结果，发展了一种应力应变简化计算方法，采用该方法计算得到的光滑试样循环应力应变结果与试验结果的误差在5%以内，并将该方法结合寿命预测方程采用迭代的方式用于粉末高温合金FGH97单边圆形缺口试样疲劳寿命预测。结果表明:所发展的方法充分考虑了FGH97合金单边圆形缺口试样缺口根部区域的应力松弛，取得了较好的寿命预测结果，其分散带基本在2倍以内。

Abstract:

In order to efficiently and accurately obtain local stress/strain at notch under cyclic loading and predict the notch fatigue life，a stress/strain simplified calculation method was developed based on viscoplastic constitutive equations and the test results of stress/strain for smooth specimens under cyclic loading. The errors between the stress/strain calculated by the developed method and test results are within 5% for smooth specimens. The simplified calculation method combined with life prediction equation was used in the fatigue life prediction of powder metallurgy superalloy FGH97 semi-circular single-edge notched specimens by iteration. The results show that the stress relaxation at notch root is fully considered by the developed method，and the fatigue life prediction of FGH97 unilateral circular notch specimens give good estimation with a scatter band of less than 2.