焊接弧坑热裂纹的力学机制分析

应用断裂力学物理量和有限元方法，分析并揭示焊缝弧坑热裂纹开裂力学机理. 通过应力的无量纲化和正交变换，将热—弹塑性有限元分析获得的节点应力等效为应力强度因子计算模型的外载荷，建立了基于应力强度因子参量的焊缝弧坑热裂纹数值分析模型. 计算并比较焊接热应力作用下焊缝含裂纹单元的张开、剪切和撕裂三类应力强度因子，揭示弧坑裂纹断裂机制并断口试验验证. 结果表明，弧坑热裂纹以拉裂模式主导，在热裂纹敏感区间1100~1000 ℃扩展速度最快，且呈“之”字形开裂取向.

Fracture mechanics analysis of welding crater solidification crack

Fracture mechanisms of welding crater solidification cracking were analyzed and revealed by fracture mechanics involved physical quantity and finite element method. Non-dimensionalized method and orthogonal transformation were utilized to translate the weld-induced stress into the loading force used in the stress intensity factor calculation model. Numerical simulation model of the crater solidification crack based on the stress intensity factor were established. The thermal stress intensity factors, including opening, shearing and tearing of the cracks, were calculated and analyzed. The fracture mechanism of the crater solidification crack was further revealed and then verified by fractography. Results showed that the fracture mechanism of the crater solidification cracking was dominated by pull crack, while the cracking propagation was fastest under the sensitive temperature range between 1 100~1 000 °C, presenting a zigzag shape cracking orientation.