REZONING AND DYNAMIC SUBSTRUCTURING TECHNIQUES IN FEM SIMULATIONS OF WELDING PROCESSES

Distortion and residual stresses cause significant problems in the wel ding of large structures. Prediction of these phenomena would provide substantial assistance to the design and fabrication of welding. Unfor tunately, the complexity of structural interactions during welding and the severe nonlinearities associated with the welding process limit t he application of weld simulations. This presentation develops rezonin g and dynamic substructuring techniques that make the finite element w elding simulation of large structures more tractable. Both techniques exploit the fact that only a local zone around the welding electrode i s nonlinear during welding. We therefore model the local nonlinear zon e around the electrode or heat source with a dense finite element mesh . The rest of the larger structure is modeled using both a coarser mes h and substructures. The model is then redefined incrementally to repr esent the motion of the electrode through the larger structure. The re definition is performed on the deformed geometry of the previous incre ment, achieving a step-wise coupled thermo-mechanical analysis. The te chniques are applied to a two-dimensional plate welding example, achie ving significant reductions in model size. Computer memory requirement s and analysis times achieve close to order-of-magnitude reductions. T hree-dimensional welding simulations should experience greater reducti ons in analysis time. Although developed for welding applications, the rezoning and dynamic substructuring techniques can also be used for o ther analyses involving a small nonlinear zone translating within a la rger elastic body.