计算缺口局部应力应变的能量法和低周疲劳寿命预测

ENERGY METHOD FOR CALCULATING LOCAL STRESS AND STRAIN AT A NOTCH ROOT AND PREDICTION OF LOW CYCLE FATIGUE LIFE

局部应力应变法已成为预测结构零、部件疲劳寿命的有效方法。 在工程上,常常用近似的方法来计算应力应变。其中最常用的一种近似方法就是Neuber法,其优点是计算比较简单,但是,所得的局部应变往往偏大,用此应变预测疲劳寿命则偏于保守。因此,有人提出用疲劳缺口系数来代替Neuber法中的应力集中系数。

The local stress-strain approach has been widely used to predict the low-cycle fatigue life for notched members. The life prediction using this approach requires the local stress and strain at a notch root. The elastic-plastic finite element method can be used to obtain the local stress and strain.But it requires complex computer program. Neuber's rule is a simple and commonly used method. Some papers have shown that Neuber'rule is generally more conservative than the corresponding finite element analysis. In this paper the energy method for calculating the local stress and strain at a notch root is presented. Based on the deformation theory of plasticity, it has been generalized to the plane strain condition. Numerical examples show that the fatigue life predicted by the local stress strain using the energy method agrees favourably with the experimental results.