狭长缺口根部萌生的小裂纹扩展分析

根据伴随着小裂纹延展过程中不同力学参数相互作用的分析研究基础之上，我们就疲劳小裂纹的扩展特性进行了分析，根据不扩展裂纹性质对小裂纹的长度范围进行了讨论，探讨了狭长缺口根部萌生的小裂纹扩展速率, 并研究了不扩展裂纹形成机理，推演出不扩展裂纹长度计算方法，发展出一种预测小裂纹扩展行为的方法，借助这种方法可以实现裂纹萌生寿命的预测，与疲劳设计相结合可以进一步提高构件安全性与可靠性．不扩展小裂纹的长度可以通过计算定量得到，它与材料的疲劳极限、裂纹门槛值及缺口尺寸等参数紧密相关．以理论数据为依据，可以设计出针对一定材料及尺寸的试样，使其在一定荷载条件下不扩展裂纹长度达到宏观可观测的范围，进而降低小裂纹测量方面的技术难度，进一步验证不扩张裂纹形成机理．

Analysis on the Short Crack Growth Initiating from Narrow Notch Root

Based on the interaction of different mechanical parameters in the short crack propagation, the characteristics of fatigue short crack propagation were analyzed. Also discussed was the crack length tolerance according to nonpropagating crack properties, as well as the crack propagation rate initiating from narrow notch root. The form mechanism of nonpropagating crack was studied, and followed by the deduction of the nonpropagating crack length. A predictive method for short crack behavior was subsequently developed. By using this method, it is possible to predict the crack initiation life and further improve the safety and reliability of components associating with the fatigue design method. Nonpropagating crack length can be quantified and it is closely related to the parameters such as fatigue limit, crack growth threshold and notch size etc. Based on the theoretical results, specific specimen could be designed for certain materials and geometries. Under certain loading condition, macroscopic nonpropagating cracks could emerge out of specimen. It reduces the technical difficulties in the measurement of short crack length, and further verifies the mechanism of nonpropagating crack formation.