关键词: 缺口, 应力梯度, 应力分布, 疲劳寿命预测

Abstract: Aiming at the problems that existed in the predicting the fatigue life processes by the critical distance method and the stress field intensity method, taking advantages of the two methods, an equivalent stress approach was proposed, where the effective stress average in spherical regions near the notch was taken as fatigue behavior control parameters. According to a set of fatigue tests, the relationship between the equivalent stress and spherical radius was studied, results show the relationship is well represented in the form of linear and exponential functions, by defining the stress gradient and relative stress gradient, a fatigue life prediction model was constructed considering the stress gradient. Determination of parameters in the model was studied,The spherical radius with the same equivalent stress of the smooth specimen and the notched specimen was taken as the damage region size under action of fatigue limit in the same load condition.  The spherical radius was obtained without test, so this method had a strong practicality. Validation of the fatigue test results indicates that the model prediction results are within 2 fold of the dispersion bands, show that the model has good prediction accuracy; the model may also predict the fatigue damage location.

Key words:  , notch；stress gradient；stress distribution；fatigue life prediction