镁合金低周疲劳损伤演化模型探讨

Discussion of Models for Low Cycle Fatigue Damage Evolution of Magnesium Alloys

通过铸造镁合金AZ91D和变形镁合金AZ31B室温环境应力控制的低周疲劳试验,基于连续损伤力学,选取平均应变的变化作为损伤变量,将镁合金的低周疲劳损伤演化划分为损伤初始阶段、损伤稳定阶段和循环末期的快速损伤阶段,各阶段的损伤分别以形核损伤、微裂纹损伤和主裂纹损伤为主。在此基础上建立了三阶段损伤模型和两阶段损伤模型,并用上述损伤模型进行了镁合金的低周疲劳损伤演化分析。研究结果表明:相对于经典的低周疲劳损伤模型,采用三阶段损伤模型和两阶段损伤模型所得损伤曲线与试验结果符合较好,能较好地反映镁合金低周疲劳损伤的演化过程。

Through low cycle fatigue experiments of the cast magnesium alloy AZ91D and the wrought magnesium alloy AZ31B at room temperature under stress control,the low cycle fatigue damage evolution of magnesium alloys was divided into the initial damage stage,the stable damage stage and the rapid damage stage at the end of the cycle by selecting the change of the mean strain as the damage variable based on the continuum damage mechanics.And the damage of each stage above mentioned was mainly caused by nucleation damage,micro-crack damage and main crack damage respectively.On this basis,the three stage damage model and the two stage damage model were developed.And then,the low cycle fatigue damage evolution was analyzed by using the above-mentioned damage models.Results show that comparing with the classic model for low cycle fatigue damage,the damage curves obtained by the three stage damage model and the two stage damage model are in a better agreement with the experimental,and which can better reflect the low cycle fatigue damage evolution process of magnesium alloys.