Finite-element Simulation of Aluminum Temperature Field and Thermal Profile in Laser Welding Process

When a laser beam is irradiated on the surface of a material, the absorbed energy causes the heating, melting, and/ or evaporation of the material depending on the absorbed laser power density. The general condition of laser welding process is to create a pool of molten material (weld pool) at the overlapping work piece surfaces. There are two general approaches for laser welding processes. In this paper, the laser beam welding is studied and Aluminum temperature field is gained in this process. The thermal effect of laser beam that specially depends on the laser type and temperature field of it in work piece is the main key of analysis and optimization of this process, from which the main goal of this paper has been defined. Utilizing laser as a method to join plastic components is growing in popularity. There are two laser welding mechanisms, keyhole mode and conduction mode. Keyhole welding is widely used because it produces welds with high aspect ratios and narrow heat affected zones. However keyhole welding can be unstable, as the keyhole oscillates and closes intermittently. This intermittent closure causes porosity due to gas entrapment. Conduction welding, on the other hand, is more stable since vaporization is minimal and hence there is no further absorption below the surface of the material. Conduction welds are usually produced using low-power focused laser beams. This results in shallow welds with a low aspect ratio. In this work, high-power CO₂ and YAG lasers have been used to produce laser conduction welds on 2mm and 3mm gauge AA5083 respectively by means of defocused beams. Full penetration butt-welds of and 3mm gauges AA508 using this process have been produced. It has been observed that in this regime the penetration depth increases initially up to a maximum and then decreases with increasing spot size.