Front tracking thermomechanical model for transient stresses during laser welding

A thermo-elasto-plastic stress analysis of transient conduction-mode pulsed laser welding is performed with the Finite Element Method. The investigation focus on the degree of dependence of resulting residual stresses on the choice of linear, quadratic of cubic elements and the technique to model zero stress state in liquid elements. The so called fixed grid and front tracking technique is used for the stress analysis whereby the front tracking method together with deformable elements makes the proper simulation of the mechanical boundary conditions at the solid/liquid interface possible. The results of the thermomechanical analysis shows significant differences concerning transient stresses depending whether the fixed grid or the front tracking method is used. The application of linear elements leads due to their stiffness to non-physical compressive stresses in the high temperature gradient region. The transient stresses differ up to 8% depending whether quadratic or cubic elements are used.