Computerized simulation of laser beam welding, modelling and verification

Abstract

The theoretical basis for the numerical simulation of stationary penetration welding with a laser beam is presented. The characteristics of the self-consistent model are the following. Vapour channel, weld pool and solid are considered as a nonlinear thermodynamic continuum. The laser-induced channel formation, multiple reflection of the laser beam in the channel, and plasma generation are taken into account. The absorption coefficient of the plasma is assumed as dependent on the degree of ionization. The geometry of the channel is determined on the basis of the pressure equilibrium at the channel surface taking the enthalpy of the molten mass into account. The input parameters for the simulation are the geometry of the workpiece, the material characteristic values dependent on temperature and the technological parameters such as laser beam power, beam diameter at focus, focus position, divergence angle of the beam, type of working gas and welding velocity. The results comprise the distribution of enthalpy and temperature, the shape and dimensions of the vapour channel of the weld pool and of the completed weld, and the energy losses by reflection, vaporization, thermal radiation and plasma shielding. The model was verified with welding experiments on steel and aluminium alloy. Data taken from the literature were also used for verification.