LASER WELDING DEPTH EVALUATION BY MEANS OF AN ANALYTIC MODEL

Abstract

An analytical model has been developed for the laser welding process which, based on multipole theory, predicts the depth of the weld bead at a very low computational cost. For this, the model starts from the thermal field previously calculated considering only the heat transfer by conduction, and includes the influence of the monopoles, dipoles and quadrupoles, which allows considering the finite thickness of the sheet to be welded, the latent heat of the material and the internal movement of the molten material, respectively. The model has been experimentally validated for Inconel 718 and the case in which a wobble strategy is used, which is a combination of linear advance motion and superposed oscillatory motion resulting in a trochoidal trajectory. For the different situations analyzed, and thanks to the consideration of multipole, the model is able to determine the depth of the weld bead with an error below 12%. This is a considerable improvement over the situation in which the multipole effect was not considered and the heat transfer was modelled only by conduction, since in this case around 50% errors are obtained, which demonstrates the validity of the model. Keywords: Laser welding, wobble, analytical model, multipole theory.