摘要
A three-dimensional laminar steady state numerical model was used to investigate the influence of an alternating current(ac)magnetic field during single pass high power laser beam keyhole welding of 20 mm thick aluminum.The three-dimensional heat transfer,fluid dynamics and electromagnetic field equations were solved with the commercial finite element package COMSOL Multiphysics.Dominant physical effects of the process were taken into account:Thermo-capillary(Marangoni)convection at the upper and lower weld pool surfaces,natural convection due to the gravity influence and the latent heat of solid-liquid phase transition.Simulations were conducted for several magnetic field strengths and it was found that the gravity drop-out associated with welding of thick plates due to the hydrostatic pressure can be prevented by the application of an ac magnetic field below the weld specimen of around 70 mT(rms)at an oscillation frequency of 450 Hz.The inductive support system allows for single-pass laser beam welding of thick aluminum plates.The flow pattern in the molten zone and the temperature distributions are significantly changed by the application of the electromagnetic forces in the weld pool.
A three-dimensional laminar steady state numerical model was used to investigate the influence of an alternating current(ac)magnetic field during single pass high power laser beam keyhole welding of 20 mm thick aluminum.The three-dimensional heat transfer,fluid dynamics and electromagnetic field equations were solved with the commercial finite element package COMSOL Multiphysics.Dominant physical effects of the process were taken into account:Thermo-capillary(Marangoni)convection at the upper and lower weld pool surfaces,natural convection due to the gravity influence and the latent heat of solid-liquid phase transition.Simulations were conducted for several magnetic field strengths and it was found that the gravity drop-out associated with welding of thick plates due to the hydrostatic pressure can be prevented by the application of an ac magnetic field below the weld specimen of around 70 mT(rms)at an oscillation frequency of 450 Hz.The inductive support system allows for single-pass laser beam welding of thick aluminum plates.The flow pattern in the molten zone and the temperature distributions are significantly changed by the application of the electromagnetic forces in the weld pool.
基金
Item Sponsored by the Deutsche Forschungsgemeinschaft (Bonn
Germany) under Grant No.DFG GU 1211/2-1
