摘要：循环载荷下受广大弹性区包围的I型裂纹尖端塑性区的材料疲劳破坏本质上属于应变疲劳，若考虑I型裂纹尖端在局部应变循环下会以突进方扩展，则可假定每次突进扩展量是平均损伤或应变能达到临界状态时裂尖塑性区的断裂扩展。基于这个思想，考虑I型裂纹裂纹尖端塑性累积损伤与应变能准则并依据I型裂纹尖端区循环应力应变场有限元解及I型裂纹裂尖区HRR（Hutchinson-Rice-Rosengren）单调应力应变场和RKE（Rice-Kujawski-Ellyin）循环应力应变场场，发展了一套基于RVE（材料代表性单元）低周疲劳临界损伤律实现对平面应力I型疲劳裂纹扩展规律的有限元分析方法和理论模型。应用新建立的两类理论模型结合15种金属材料，对疲劳裂纹扩展规律进行了预测，结果表明新模型具有广泛普适性。成果可用于含裂纹结构的结构完整性分析。
　　关键词：低周疲劳，疲劳裂纹扩展，塑性损伤，塑性应变能，断裂，裂纹，工程材料

　　Abstract:Material fatigue failure within the plastic zone near crack tip for mode-I crack essentially belongs to strain fatigue, under cyclic loading due to existing large elastic constraint.  As it is assumed that the mode-I crack propagates in step-type under local strain cycling, the step-type propagation magnitude of the crack at a time is equal to the dimension of plastic zone when the average damage or strain energy of the zone reaches the critical state. Therefore,based on above thoughts and according to some mechanics aspects such as the plastic accumulation damage, the plastic strain energy for mode-I crack tip and the cycle stress or strain solution from the finite element fields, and the Hucthinson-Rice-Rosengren （HRR） or the Rice-Kujawski-Ellyin （RKE） stress-strain fields, the several new methods by finite element and theoretical models are developed to establish the relations between the low cycle fatigue properties and the mode-I crack propagation rate of materials. Finally, fatigue crack growth laws are investigated by the new models developed and the experimental data of fifteen kinds of engineering materials. The results show that the proposed theoretical models and finite element method can be widely used to describe the behavior of material fatigue crack propagation for mode-I crack. The new theoretical models can be applied in the structure integrity estimation including surface crack.
　　Key words : Low cycle fatigue,fatigue crack growth,accumulation damage,strain energy, fracture, crack, engineering material
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