Interaction between laser beam, process effects, and structural properties during welding using models based on the finite element analysis

The aim of this contribution is to study the influence of the laser beam on the structural properties of sheet metals during welding by considering particular process effects. The interaction between process parameters, such as the exact positioning of the laser focus and the weld gap between sheets, affects the stability of the laser beam welding process and thus the quality of weld seams. Furthermore, additional interaction of the welding process with manufacturing tolerances and structural properties, i.e., material thinning and residual stresses after forming, influence the behavior of structures. Heat effects during and after the laser beam welding process produce residual stresses as well as phase transformation, in the case of steel alloys, in the weld seam and the heat affected zone. For this reason distortion of the whole welded structure is caused. Depending, next to the laser beam parameters, on the type of welded joint, on the structure geometry and on the clamping conditions, the residual stresses and the distortion of structures may vary. In order to examine the process design variation, three different types of welded joints were considered. A lap and a fillet seam as well as a heat conduction bead-on-plate seam on a formed sheet of steel were produced and the distortion was measured. Finally, the results are compared with the finite element analysis. (c) 2007 Laser Institute of America.