一种多轴疲劳寿命预测的统一模型

基于SAE 1045中碳钢的单-多轴疲劳试验结果，在研究了扭转名义应力幅与拉伸名义应力幅不同比值时的多轴疲劳寿命预测模型之后，建立了统一的多轴疲劳寿命预测模型。发现：不同的扭转名义应力幅与拉伸名义应力幅之比导致不同的寿命预测模型，为寻求单轴模型与多铀统一模型的关系，假设单轴疲劳寿命预测模型中的疲劳强度指数和疲劳延性指数不变，而对疲劳强度系数乘以1．5435、疲劳延性系数乘以0．6713，以第一主应变幅取代单轴拉压应变幅，则修正后的单轴模型等价于多轴统一模型，利用修正后的单轴模型可以预测任意扭转名义应力幅与拉伸名义应力幅之比时的多轴疲劳寿命。

A Unified Model for Predication of Multi-Axial Fatigue Life

Based on the fatigue test results of SAE 1045 medium carbon steel, the multi - axial fatigue life predication models for different ratios of torsional nominal stress amplitude to the axial one are studied respectively. Then a unified multi -axial fatigue life predication model is founded. It is found that the different ratios induce different models. In order to get the relationship between the axial model and the unified multi - axial model, it is supposed that the fatigue strength exponent and the fatigue ductility exponent are constants, while the fatigue strength coefficient times 1. 5435 and the fatigue ductility coefficient times 0. 6713, the maximum principle stain amplitude replaces the axial push- pull strain amplitude, then the revised axial fatigue life predication model is equivalent to the unified multi -axial model. Therefore, the revised axial fatigue life predication model can be used to predict the multi - axial fatigue life for any ratio of torsional nominal stress amplitude to the axial one.