Numerical Simulation Of The Dynamic Behavior Of Weld Pools In High-Speed Pulsed Gas Metal Arc Welding

In order to optimize the welding parameters, a 3D transient numerical model for the fluid flow and heat transfer in high-speed pulsed gas metal arc welding (GMAW) is established to investigate the dynamic behaviors of weld pool.First, according to the features of periodical droplet transfer, deformation and fluctuations on weld pool free surface in high-speed pulsed GMAW, a forced vibration model and a wave fluctuation model on deformed weld pool free surfaces are established. On this basis, a new heat source model that can describe the heat flow density distribution in arc spaces above the deformed and fluctuated weld pool free surfaces is developed, which is called heat flow density distribution model in arc spaces. Second, the governing differential equations are derived as the energy conservation, momentum conservation and mass conservation, respectively. After that, corresponding initial conditions and boundary conditions are given and the governing equations are discretized. Finally, the calculating software written in FORTRAN is programmed.The dynamic behaviors of weld pools are analyzed numerically by using forced vibration and wave fluctuation models on deformed weld pool free surface, heat flow density distribution model in arc spaces and numerical model of the thermal process. The vibration and wave fluctuation of the free surface of weld pools are simulated by the established models above, so accurate morphology of weld pool free surface at different time is obtained. Therefore, the heat flux distribution of arc in 3D space is grounded on the wave behaviors of deformed weld pool free surfaces. By utilizing the heat input model, the heat and fluid flow fields of high-speed pulsed GMAW workpiece are studied carefully with time changes. Comparison between predicted data and measured ones are performed, and the results show that the new established heat source model is suitable for the numerical simulation of heat and mass transfer in high-speed pulsed GMAW. Apparent heat capacity method is used to deal with the latent heat of phase transformation.The dynamic behaviors of weld pools in different welding parameters such as welding current and welding speed are predicted, thus the transient developments of 3D heat field, fluid field and shape of weld pool with different welding parameters are obtained. The changing tendency of the 3D heat fields, fluid fields and shapes of weld pool with different welding parameters are analyzed and the predicted results show a good agreement with the experimental data.This study could provide basic data and theoretical instruction for the industry application and optimization of welding parameters of high-speed pulsed GMAW.