This study is based on continuum damage mechanics and constructs an improved macro–micro-two-scale model to predict the fatigue life of engineering metallic materials subjected to variable amplitude loading. To account quantitatively for the fatigue damage retarding effect of higher load on lower ones in a loading sequence, the cyclic plastic response curve of microscopic weak inclusion is independently designed. Meanwhile, an improved two-scale fatigue damage model in rate form is proposed by introducing a new exponent function acted on the equivalent plastic strain term in the model for taking account of fatigue mean stress effect under variable amplitude loading. The parameters of the two-scale fatigue damage model are identified through an inverse approach based on fatigue test results under constant amplitude loading. The predictive accuracy of the proposed model is validated by fatigue test data of Al 2024-T3 standard coupon and plate with a hole under different variable amplitude loading.

这项研究基于连续损伤力学，并构建了改进的宏观－微观－两尺度模型，以预测承受可变振幅载荷的工程金属材料的疲劳寿命。为了定量说明在加载顺序中较高负载对较低负载的疲劳破坏抑制效果，我们独立设计了微观弱夹杂物的循环塑性响应曲线。同时，通过考虑可变振幅载荷下的疲劳平均应力效应，通过引入作用于等效塑性应变项的新指数函数，提出了一种改进的速率形式的两级疲劳损伤模型。基于恒定振幅载荷下的疲劳测试结果，通过逆方法确定了两级疲劳损伤模型的参数。