中文摘要：

二元疲劳失效判据认为疲劳破坏是由损伤程度和当前作用应力这两个量共同决定的，由此观点出发定义了非线性损伤，并建立了与载荷状态有关的非线性损伤累积模型，推导了在多级加载下的递推公式。经两种金属材料的疲劳试验数据验证表明，用该模型预测疲劳寿命，其结果是令人满意的。从疲劳过程本质上是材料静强度不断退化的过程的观点出发，建立了基于二元疲劳失效判据的非线性强度退化模型，将模型应用于两级及多级载荷下的剩余寿命估算，结果表明，所提出的剩余强度退化模型是合理可行的。

英文摘要：

Damage degree as well as current applied stress level leads to fatigue failure in double parameter fatigue criterion. Proceeded from this argument, a nonlinear fatigue damage cumulative model which related with the current applied stress was proposed after the definition of nonlinear damage. The fatigue limit, current applied stress level and the inseparable characteristics for the damage variables were considered by the proposed fatigue damage cumulative model, the fatigue damage evolu- tion equation was derived under multilevel loading which can describe the fatigue damage evolution behavior well. The fatigue test data for two kinds of material were used to verify the model proposed. The results show that good agreement is achieved with this model to predict fatigue life. A nonlinear strength degradation model based on the double parameter fatigue criterion was presented from the view point that fatigue damage process is the process during which material static strength degrades constantly. The model was applied to predict fatigue lives for both two level cyclic loading and multiple amplitude program loading and verified by the experiments. It is shown that the estimation has good correlation with the experiments.