Finite element simulation of laser spot welding

The present work reports on a two-dimensional axisymmetric Ž nite element analysis of heat  ow during laser spot welding, taking into account the temperature dependence of the physical properties and latent heat of transformations. An analysis based on conduction heat transfer alone, but using the ‘double ellipsoidal’ representation of the laser beam, seems to be sufŽ cient to estimate the transition to keyhole formation during laser spot welding, although the ‘double ellipsoidal’ representation requires an a priori knowledge of the expected weld pool dimensions. Transient temperature isotherms and the weld pool dimensions are predicted using the model; the latter are found to compare well with measurements of weld bead dimensions. The results show that the keyhole mode is stimulated using either a high laser power and low ontime or a low laser power and high on-time. The outcomes are found to be sensitive to the assumed absorptivity and the assumed weld pool depth used to deŽ ne the ‘double ellipsoidal’ heat source. STWJ/362