比例加载下应力幅比对2A12-T4疲劳寿命的影响

采用2A12-T4铝合金漏斗形试件,针对不同拉扭应力幅比,进行了比例加载下多轴高周疲劳寿命试验,研究了不同应力幅比对多轴高周疲劳寿命的影响.针对试验结果,采用3种常用的多轴高周疲劳寿命预测模型,包括等效应力准则、应力不变量准则、临界面准则进行了预测.结果表明:在相同的Von-Mises等效应力下,随着扭转应力幅与拉压应力幅比值的增大,疲劳寿命逐渐升高.等效应力准则的预测结果或过于危险,或过于安全;应力不变量准则的预测结果认为应力幅比的变化对疲劳失效没有影响,与试验结果不符;临界面准则的预测结果优于其他准则.

Effect of stress amplitude on high-cycle fatigue life of 2A12-T4 aluminum alloy under proportional loading

Fatigue life experiments with funneled-shape specimens were conducted to investigate the effect of stress amplitude on multi-axial high-cycle fatigue failure of 2A12-T4 aluminum alloy under tension-torsion proportional loading. Based on the experiment results, three kinds of life-prediction criteria, which were widely used for multi-axial high-cycle fatigue analysis, were discussed. The results showe that under the same von-Mises equivalent stress, fatigue life raised gradually when the ratio of stress amplitude in tension and torsion increased. Fatigue life of uniaxial tension is the shortest and that of pure torsion is the longest. The forecast results of equivalent stress criteria are either too dangerous, or too conservative. Stress invariant criteria cannot predict the impact of stress-amplitude ratio on multi-axial high-cycle fatigue failure. Critical-plane criteria has better prediction capability than others.