随机载荷下疲劳裂纹的闭合和扩展估算模型

本文分析了裂尖前,后方塑性区对闭合性能的影响,提出从裂尖塑性钝化量和尾迹区残余塑性变形两个方面来确定裂纹面的残余变形,并讨论了压缩载荷对闭合应力的影响,由此建立了一个疲劳裂纹闭合模型,然后通过模型“有限记忆”性质的假定将它应用到随机加载情况。用此模型对铝合金2219——T851受飞机谱载荷的CCT平面应力试件进行了疲劳寿命估算,估算值与实验结果接近。

PREDICTION MODELS OF FATIGUE CRACK CLOSURE AND GROWTH UNDER RANDOM LOADING

The effects of plastic zones both infront of and behind crack tip on crack closure has becn analysed. The total residual deformationss of crack surfaces involve two parts, that is, the amount of plastic blunting of crack tip and the residual deformation in the wake of the up. The paper presents a fatigue crack closure model, in which the influences of compression load on closure stress are covered. The model is then applied to random loading conditions by the assumption of "limit memory" properties.The fatigue lives are predicted based on the crack growth model for CCT plane stress specimen cut from 2219-T851 aluminum alloy under flight spectrum loadings,and the prediction values consist with the test results.