多轴载荷下弹塑性有限元分析及疲劳寿命预测

FINITE ELEMENT ANALYSIS OF ELASTIC-PLASTIC AND FATIGUE LIFE PREDICTIONS UNDER MULTIAXIAL LOADING

在550℃温度下,针对Mod.9Cr-1Mo铁素体钢进行一系列多轴疲劳试验,定义主应变比用于考虑不同的比例程度对多轴疲劳寿命的影响。采用Ansys软件进行模拟计算,材料弹塑性特性采用von Mises屈服准则、多线性运动硬化律和单轴循环应力应变曲线描述。采用柱坐标系,通过固定试件一端,另一端加轴向和周向位移来实现拉扭应变控制。有限元模拟得到的应力应变曲线与试验结果对比分析表明,模拟得到的正应力值与试验值总体平均误差为5%。基于模拟得到的应力应变结果,采用Smith-Watson-Topper和Fatemi-Socie法进行疲劳寿命预测。

A series of tests for low cycle fatigue are conducted for Mod. 9Cr - 1Mo ferrite steel under muhiaxial loading at 550 ℃. The effect of strain multiaxiality under proportional loading on the fatigue life is considered by defining the principal strain ratio. Ansys software is used for simulating and the von Mises yield criterion, multlinear kinematic hardening rule, and uniaxial cyclic stress-strain curve are employed to indicate the material elastic-plastic property. In the cylindrical coordinate, one end is fixed and another one is subjected to the axial displacement and circumference displacement to gain the strain control as those in the test. The comparison analysis of the stress-strain hysteresis has been done between the test results and simulations. The normal stress comparison between the simulation results and the tests shows that the whole error is less than 5% . Smith- Watson-Topper and Fatemi-Socie approaches are employed to predict the [atigue life based on tile simulation results.