一种考虑应力梯度的疲劳寿命预测方法

发布时间：2019-03-17 11:27

【摘要】：针对临界距离法及应力场强法在疲劳寿命预测过程中存在的问题,结合临界距离法计算量小、应力场强法能够反映构件所处应力状态的优点,提出了以缺口附近球形区域内的等效应力均值作为控制疲劳行为的当量应力的方法。参照一组疲劳试验对当量应力与球形区域半径的关系进行了研究,结果表明可用线性和指数函数的形式表示两者间的关系。通过定义应力梯度、相对应力梯度,构建了一种能够考虑应力梯度的疲劳寿命预测模型。对模型中参数的确定方法进行研究,提出了以光滑试件、缺口试件在各自相同载荷条件的疲劳极限作用下,两者当量应力相等时的球形区域半径作为损伤区域大小的方法,该方法不再需要通过试验获得半径参数,具有较强的实用性。疲劳试验结果表明,模型预测结果均在2倍分散带内,证明模型具有较好的预测精度,同时模型可准确预测疲劳破坏位置。
[Abstract]:In view of the problems of critical distance method and stress field strength method in the process of fatigue life prediction, combined with the small calculation amount of critical distance method, the stress field strength method can reflect the stress state of the component, and the stress field strength method can reflect the stress state of the component. In this paper, the equivalent stress in spherical region near the notch is used as the equivalent stress to control fatigue behavior. The relationship between equivalent stress and radius of spherical region is studied with reference to a group of fatigue tests. The results show that the relationship between equivalent stress and radius of spherical region can be expressed in the form of linear and exponential functions. By defining the stress gradient and the relative stress gradient, a fatigue life prediction model which can consider the stress gradient is constructed. The method of determining the parameters in the model is studied. Under the fatigue limit action of the smooth specimen and the notched specimen under the same loading conditions, the radius of the spherical region with equal equivalent stress between the two specimens is used as the size of the damage region. This method no longer needs to obtain radius parameters by experiment, and it has strong practicability. The results of fatigue test show that the prediction results of the model are within 2 times of the dispersed band, which proves that the model has a good prediction accuracy, and the model can accurately predict the position of fatigue failure.
【作者单位】：西南石油大学机电工程学院;
【分类号】：O346.2

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