Three-dimensional simulation transient keyhole evolution during laser keyhole welding

Laser keyhole welding process is not well understood because the related physics are too complex. Numerical simulation of transient keyhole evolution provides fundamental data needed to improve understanding of the mechanisms of porosity formation during laser welding. In this paper, a three dimensional mathematical model was proposed to simulate the keyhole formation process of laser welding. The coupled effects of multi-reflections Fresnel absorption of keyhole, heat conduction, heat convection, heat radiation and Knudsen jump boundary conditions on the liquid-vapor evaporation interface were considered in this model. A level set method and a fast sweeping method were developed to solve the model. The transient keyhole shape, the surface recession speed due to evaporation and the thermal distribution of keyhole wall were investigated. The time-varied surface tension force of keyhole wall was also calculated.