Numerical modeling of molten pool formation during an interaction of a pulse laser (Nd:YAG) with an aluminum sheet

Laser welding offers many advantages over conventional techniques, but is subject to a great number of different parameters. Whereas a purely experimental study would be very expensive, modelling the process can optimize it more economically. Laser welding leads to the occurrence of physical phenomena that do not appear in conventional welding. Modelling presents several difficulties arising from the following: the strong thermal gradients present over short distances; the evaporation of the material, leading to a deformation of the free surface; the appearance of a keyhole-like cavity if the recoil pressure becomes particularly high. Marangoni convection, initiated by surface tension gradients, has a considerable effect on thermal transfer in the melted pool and, consequently, on the enlargement of the melted pool. The latent heat of fusion and vaporization are introduced into the model as sources in the heat equation. The Newton-Stokes equations are modified to model the flow in the solid-liquid zone. The model takes into account the non-linearities arising from the variations, with temperature, of thermophysical characteristics. The results of a 2D numerical calculation for a laser pulse (Nd : YAG) on a sheet of aluminium are presented here. FEMLAB, a software based on the finite element method, was used.