变幅载荷下的疲劳裂纹扩展

Fatigue Crack Propagation Under Variable Amplitude Loading

通过１６Ｍｎ钢在高－低、低－高－低和低－高加载情况下，不同超载比时的裂纹扩展进行了实验研究，获得了裂纹长度与循环次数、裂纹扩展速率与裂纹长度的相应变化曲线．实验表明，在高－低和低－高－低加载下疲劳裂纹扩展具有迟滞效应，其随超载比增大而增大，文中使用常用的Ｗｉｌｌｅｎｂｏｒｇ模型对具有迟滞效应情况进行了寿命分析，计算表明在大超载比下与实验结果相比明显偏大，上述现象对变幅载荷下有裂纹机械构件的安全寿命预测具有重要意义．

The fatigue crack propagation experiments of 16 Mn steel are performed under high-low,lowhigh-low,and low-high loading with different overload ratio. The relative curves of crack length vs cycle number and crack propagation rate vs crack length are obtained. The experiments confirm that fatigue crack propagation under high-low and low-high-low loading possesses retardation effect. This effect is increased with moressing overload ratio. The paper uses Willenborge model for evalutaing the life with retardation effect. It appears that the above calculating result under large overload ratio tends to be great compared with experimental result. The above phenomenon is important for safe life evaluating of mechanical components under variable amplitude loading.