材料因素对金属疲劳裂纹扩展的影响

Impacts of Material Factors on Metal Fatigue Crack Growth

先进工艺和材料的发展往往突破了经典断裂力学理论中的宏观均匀各向同性材料假设,使得当前主要关注裂尖力学参数,仅以试验数据拟合参数来考虑材料因素影响的金属材料疲劳裂纹扩展分析方法难以适用。本文首先基于课题组近年来在金属材料疲劳裂纹扩展方面的研究,对材料因素导致的特殊疲劳裂纹扩展行为进行介绍,并对其机理进行分析和总结;然后,对当前疲劳裂纹扩展分析方法的逻辑思路进行分析,并指出相关研究的主要落脚点在于合理有效地考虑力学因素和材料因素的影响;最后,主要针对疲劳裂纹路径偏折的预测方法进行讨论,提出了一种疲劳裂纹扩展的净驱动力概念模型。本文的分析讨论有助于从力学因素与材料因素交互作用的角度来看待金属疲劳裂纹扩展问题,所得结论能够为先进工艺金属材料的疲劳裂纹扩展分析及相应结构的损伤容限分析评估提供指导。

Developments of advanced processing and materials is violating the assumption of material homogeneity and material isotropy in classical fracture mechanics,and it is thus infeasible for the present analysis methods of fatigue crack growth(FCG)to apply,in which mechanical parameters are the focus and material impacts are considered merely as fitting parameters of experiment data.In this paper,typical fatigue crack growth behaviors are firstly introduced and the underlying mechanisms are briefly summarized,which are based on our relevant studies in the past few years.Then,the logics of present models and methods are analyzed,which implies that the research focus should be put on the reasonable and effective considerations of interactions between mechanical factors and material factors.Finally,prediction methods of fatigue crack path deflections are discussed,based on which a conceptional model of net driving force for FCG is proposed.The analysis and discussions in this paper help conceive FCG from the perspective of mechanics-material interaction,and the obtained conclusions can provide guidelines for FCG analysis of advanced materials as well as damage tolerance evaluations of corresponding structures.