激光穿孔焊接过程热流场数值模拟

采用随小孔形状实时变化的自适应热源,建立了三维光纤激光穿孔焊接过程的数值分析模型。激光热源加载在时变的气/液界面,考虑气相和液相转变过程中存在的传热与传质现象,利用焓-孔介质法处理焊接过程中动量损耗及相变潜热问题。小孔壁面计算主要考虑反冲压力和表面张力,求解VOF方程获得气/液界面。结果表明,焊接过程中可能产生飞溅、焊瘤和余高,小孔前部的金属液体沿着小孔回流至小孔尾部形成焊缝,小孔后部熔池左右两侧可能产生涡旋现象,光致等离子体产生时间极短,穿孔前等离子体最大速度快速增加到102.95 m/s左右,穿孔后速度值下降至80 m/s左右,仿真分析为实际焊接过程提供理论依据。

Numerical simulation of temperature and velocity field in laser drilling weld

A three dimensional numerical simulation model of optical laser drilling weld was established,by using adaptive heat source with real-time variation of keyhole shape.The laser heat source was loaded at the time-varying gas/liquid interface,considering heat and mass transfer in the process of gas and liquid phase transition.The momentum loss and latent heat due to solidification and melting was dealt with by enthalpy-porosity technique.The keyhole wall was calculated by solving VOF equation,mainly considering recoil pressure induced by the metal evaporation and surface tension.The result shows that the welding process may produce flash,overlap and reinforcement.Welded joint is formed when the metal liquid flows back from the front to the rear of the keyhole,and a swirl may occur on the left and right sides the welding pool at the rear of the keyhole.The time of plasma generation is very short,and the maximum velocity of plasma increases rapidly to about 102.95 m/s before drilling,then it drops to about 80 m/s after drilling.The simulation analysis provides a theoretical basis for the actual welding process.