激光入射角影响焊接熔池匙孔瞬态行为数值模拟

在激光焊接中，激光入射角直接影响着熔池匙孔瞬态行为，而仅采用工艺试验方法难以探索其规律。利用数值模拟技术模拟激光入射角分别为30°、0°、-30°的焊接过程，研究激光入射角对熔池匙孔瞬态行为的影响。同时通过激光焊接试验对仿真结果进行验证，数值仿真的焊缝横截面形貌与试验结果吻合较好，表明仿真结果能够反映激光焊接过程。分析不同激光入射角下温度场、熔池内流场、匙孔后壁反冲压力、匙孔深度和匙孔后壁静压力的变化。结果表明，激光入射角的正负影响熔池内部流动的快慢；激光入射角为正时，有利于抑制飞溅形成，而激光入射角为负时，则促进飞溅生成；激光入射角的正负明显影响匙孔的稳定性，当激光入射角为负时，匙孔稳定性降低，坍塌频率增加，产生气泡的概率提高。使用合适的激光正入射角有利于提高激光焊接质量。

Numerical Simulation of Effects of Laser Incident Angle on Transient Behaviors of Molten Pool and Keyhole during Laser Welding

The laser incident angle affects the transient behaviors of a molten pool and keyhole in the process of laser welding. However, it is difficult to investigate its impact rule only by using technical experimental methods. Three processes of laser welding with the laser incident angle of 30°, 0°, -30° are respectively simulated by the numerical simulation technology to study the effects of laser incident angle on transient behaviors of a molten pool and keyhole. At the same time, the simulated results are validated through the laser welding experiments. The cross-section geometry of simulated welds agrees well with the experimental results, which indicates that the simulated results can represent the laser welding process. The variations of temperature field, flow field in a molten pool, recoil force on the rear keyhole wall, the depth of keyhole and static pressure on the rear keyhole wall are analyzed at different laser incident angles. The results show that when the laser incident angle is positive, the flow is slow in a molten pool, when it is negative, the flow is faster. Also it can be found that the positive incident angle welding is helpful to suppress the formation of spatters, while the negative promotes the generation of spatters. When the laser incident angle is positive, the stability of a keyhole increases. When it is negative, the stability of a keyhole decreases, and the collapse of a keyhole increases which raises the probability of bubbles generation. Thus, it is shown that the laser welding quality can be improved with a suitable positive laser incident angle.