中文摘要：

应用弹塑性有限元方法与增量塑性损伤理论指出疲劳裂纹扩展的压载荷效应是裂纹尖端塑性损伤的结果,建立了在拉-压循环加载下铝合金疲劳裂纹扩展速率的双参数预报模型,对LY12-M高强铝合金MT试件在应力比R=0、0.5、1、2进行了疲劳裂纹扩展实验。结果表明：当最大应力强度因子Kmax相同时,恒幅拉压加载（应力比R〈0）的疲劳裂纹扩展速率明显高于恒幅拉拉加载（应力比R=0）的情况,拉-压循环载荷的压载荷部分对疲劳裂纹扩展速率具有促进作用。该文得出的LY12-M铝合金在拉-压循环加载下的疲劳裂纹扩展速率预报模型与实验结果符合较好。

英文摘要：

The effect of compressive loading on fatigue crack growth was studied using an elastic-plastic finite element analysis and incremental plastic damage theory.The results show that the effect of compressive loading on fatigue crack growth results from the plastic damage of a crack tip.A double parameter model of predicting fatigue crack propagation rate under tension-compressive loading is established.The fatigue crack growth test of the high-strength aluminum alloy LY12-M at the stress ratio R=0,-0.5,-1 and-2 is performed.The results show that the fatigue crack growth rate at R0（R=-0.5,-1 and-2） is significantly higher than the one at R = 0 for the same Kmax.The compressive loading in the load cycle promotes the fatigue crack propagation of LY12-M aluminum alloy.The model has been proved to be in agreement with the experimental data.