基于损伤力学的疲劳裂纹萌生及扩展规律研究

针对金属构件疲劳裂纹的萌生、扩展寿命及其规律等问题,应用损伤力学理论与有限元相结合的方法,建立了计算疲劳裂纹全寿命的统一模型。引入附加载荷法,通过MATLAB编程计算,实现了对刚度矩阵的连续计算,并给出了编程的流程。通过对单个单元的损伤计算,得到了单元从无损到破坏过程中等效应力的变化;通过计算各个构件损伤单元寿命,进而给出了金属构件总体疲劳寿命。分析得到了微裂纹萌生及扩展寿命占总体疲劳寿命的80%以上,并应用有限元软件ANSYS模拟给出了缺口件裂纹萌生及扩展过程。理论计算的结果与试验数据对比基本一致,验证了本工作方法的准确性。

Fatigue Crack Initiation and Extension Regularity Based on Damage Mechanics

Aiming at the problem of metal fatigue crack initiation and propagation life forecast, an unified a model was presented based on damage mechanics and finite element method, and the calculating program was established.The stiffness matrix was continuously calculated by introducing the additional loading method.The calculating program was designed in MATLAB and the calculation flow diagram was showed in this paper.Then through the calculation of a single cell,the changing process of equivalent stress was presented with the cell from undamaged state to completely damaged state and the reasons of the changes were analyzed. It was found that the crack initiation and propagation life was more than 80% of the total life. By finite element software ANSYS simulation, the crack initiation and propagation process of notched specimen were obtained. Finally, the results of theoretical calculation and the experimental data were basically identical, which verify the accuracy of this method.