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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。
The application of elasto-plastic finite element method and incremental plastic damage theory points out that the compressive load effect of fatigue crack growth is the result of plastic damage at crack tip. A two-parameter model of fatigue crack growth rate of aluminum alloy under tension-compression cyclic loading is established. LY12-M high-strength aluminum alloy MT test pieces in the stress ratio R = 0,0.5,1,2 fatigue crack growth experiments. The results show that the fatigue crack growth rate under constant amplitude tension-compression loading (stress ratio R <0) is obviously higher than that under constant amplitude tension loading (stress ratio R = 0) when the maximum stress intensity factor Kmax is the same. Of the ballast part of fatigue crack growth rate has a catalytic role. The prediction model of fatigue crack growth rate of LY12-M aluminum alloy under the tension-compression cycle is in good agreement with the experimental results.