基于Tanaka-Mura位错模型的疲劳裂纹萌生寿命预测

为建立焊趾疲劳裂纹萌生行为仿真方法，基于 Roe-Siegmund 循环内聚力模型对 ABAQUS 进行二次开发，形成用于反映疲劳累积损伤的VUMAT子程序，依据文献方法及试验数据获取Q345焊接区域材料的内聚力参数，通过Voronoi图法和内聚力单元法生成具有疲劳累积损伤特性和晶粒特征的微观模型，并与宏观对接焊缝模型合并，进行多尺度疲劳裂纹萌生仿真模拟，获得裂纹萌生路径、临界循环次数及晶粒力学响应特征. 结果表明，此方法能够自发地选择符合实际情况的裂纹萌生位置以及短裂纹扩展路径，完成对焊接区域材料微观断裂过程的模拟，不同仿真组获取的临界循环次数存在于一定的分布范围内，模型中的累积内聚力长度需通过试验数据进行拟合.

Fatigue crack initiation life prediction based on Tanaka-Mura dislocation model

In order to establish a simulation method for the fatigue crack initiation behavior of the weld toe, ABAQUS was developed based on the Roe-Siegmund cyclic cohesive zone model to form the VUMAT subroutine for reflecting the fatigue cumulative damage. The cohesive parameters of Q345 weld zone materials were obtained by referring to the literature and experimental data. The Voronoi diagram method and cohesive element method were used to generate a microscopic model with fatigue cumulative damage characteristics and grain characteristics. This model was then merged with the macroscopic butt weld model to simulate multi-scale fatigue crack initiation. The results show that this method can spontaneously select the crack initiation location and the short crack extension path in accordance with the actual situation, and complete the simulation of the microfracture process of the material in the welded area, the critical cycle number obtained by different simulation groups exists in a certain distribution range, and the cumulative cohesive length needs to be fitted by experimental data.