MODELING DEEP PENETRATION LASER-WELDING USING A BEM SENSITIVITY SCHEME

The process of deep penetration welding is modelled by dividing the pr oblem into three sub-regions: solid, liquid and vapor. Each of these s ub-regions are analyzed individually by the most suitable method. By m atching these three solutions with appropriate boundary conditions, a complete model is obtained. The boundary element method (BEM) is used to simulate the heat transfer within the solid region. Lubrication the ory is applied to model the heat transfer within the liquid. The non-e quilibrium vaporization and subsequent gas dynamics are modelled by a one-dimensional model. This paper presents a BEM formulation for three -dimensional steady-state convection-conduction problems and a BEM sen sitivity formulation for the determination of sensitivities of tempera ture and heat flux due to a boundary shape parameter. The BEM sensitiv ity formulation is based on the direct differentiation approach (DDA). These formulations are applied to simulate deep penetration welding. It is found that the BEM and the sensitivity formulation are very effi cient and robust in the determination of the solid-liquid interface in a workpiece.