Numerical analysis of the temperature profiles and weld dimension in high power direct-diode laser welding

Since high power direct-diode laser (HPDDL) generates a rectangular output beam profile, unlike the small round beam spot of conventional lasers, HPDDL welding is a new welding technology of larger joint fit-up tolerance and application potential for seam welding of sheet metals. In this paper, a mathematical model is developed to conduct numerical simulation of temperature field and weld pool dimensions for this novel HPDDL welding process. Considering the different distribution characteristics along the length and width directions in the laser strip, the distribution function of heat intensity within the laser strip which has a angle to the welding direction is established for HPDDL welding. Finite difference method is employed to solve the governing equation and boundary conditions for obtaining fundamental information on the temperature profiles, thermal cycles, and weld pool dimensions in HPDDL welding, all which are asymmetric with respect to the weld centerline, because the laser strip is tilted with an angle to the welding direction in HPDDL welding. The experiments are carried out to observe the weld morphology and dimensions. It is found that the predicted HPDDL weld width is in agreement with the experimentally measured one.