很多学者对表面裂纹形状变化规律进行了研究,但是理论上仍存在较大缺陷,因此现有方法预报结果的准确性有待考察.文章作者们提出了一个改进的统一疲劳裂纹扩展速率模型,本模型合理考虑了材料的非线性效应和裂纹前缘的三维约束效应及三维约束大小在前缘各点的分布函数.通过引入等效厚度的概念及法线方向扩展的假定较好地考虑了裂纹前缘各点对扩展之后形状比变化规律的影响,预报得到的裂纹前缘形状能够观察到明显的边界点扩展滞后现象,同时本模型预报结果与试验结果及传统模型预报结果进行了比较,证明本模型提高了表面裂纹扩展规律预报的精度.%Many investigators have carried out the study on crack shape evolution law but some deficiencies are observed from the predicted results obtained using the existed methods. In this paper,an improved fatigue crack growth model was proposed. The nonlinear effect of the material, the closure behavior of the crack front and its distribution along the crack front are sufficiently considered in this model, which will be used to evaluate the surface crack shape evolution. Moreover, by introducing the concept of equivalent thickness at each point and the assumption of crack propagation at normal direction,the effect of different stress state at each point on crack shape evolution law is reasonably considered and the surface retardation due to boundary effect is successfully predicted. The evaluation precision of crack shape evolution law from this model is highly improved compared with the test data and the predicted curve from Paris law.
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