多轴非比例载荷下镁合金AZ21的疲劳性能研究

Fatigue Characteristics of Mg Alloy AZ21 Under Multiaxial Non-Proportional Loading

镁合金作为结构件承受多轴复杂载荷,其失效形式多为多轴疲劳失效.本文在空气环境中对镁合金AZ21分别进行了单轴、纯扭以及多轴循环力学性能研究,揭示了不同加载路径下材料的变形主导机制.疲劳试验结果表明,在相同等效应力幅下,非比例加载路径下镁合金AZ21的寿命较单轴、纯扭路径显著降低.采用Basquin公式预测镁合金AZ21在复杂载荷下的疲劳寿命.通过将路径非比例度的概念引入到Basquin公式中,可合理预测相同加载幅值下圆形路径和菱形路径作用时镁合金AZ21的疲劳寿命.

Widely used for engineering structural components,Mg alloys are normally subjected to complicated multiaxial loads,and generally suffer multiaxial fatigue failure.In this study,the cyclic mechanical properties of the Mg alloy AZ21 were investigated under uniaxial,torsional and multiaxial loading paths in air.The dominant deformation mechanisms were revealed under different loading paths.The fatigue testing results showed that with the same equivalent stress amplitude,the fatigue lives under multiaxial non-proportional loading paths were much shorter than those under uniaxial and torsional loading paths.Basquin equation was used to predict the fatigue life of the Mg alloy AZ21 under complex loading paths.By introducing a non-proportionality factor into Basquin equation,reasonable life predictions of the Mg alloy AZ21 were achieved for the circular and rhombic paths with the same loading amplitude.