Numerical Study Of Fluctuations Of Double Wire GMA Weldpool Surface

Welding has become an essential means of connection in equipmentmanufacturing industry. In order to improve the welding efficiency, pulsed double wireGMA welding has been more widely used in practice. Relevant reports about doublewire GMA weld pool surface fluctuations is not seen in current research, and the weldcorrugation is a very important aspect of welding quality. Numerical simulation is aneffective way to study the twin-wire GMA pool surface fluctuations. It can provide aquantitative calculation of dynamic pool level fluctuations.This paper focuses on the interface of twin-wire GMA arc and workpiece--theweldpool free surface transient fluctuations behavior. Using thin film vibration andcombining the wave theory, in the analysis of surface force of low carbon steel basematerial partially penetrated weldpool, considered arc pressure, droplet impact force,the surface fluctuation wave equations are established under arc pressure and dropletimpact separately. With modular design concept, the program is written and modulatedon the Intel Visual Fortran platform. By using mathematical model established, thefluctuations displacement and velocity dynamic changes of arc induction, singledroplet impact and double wire GMA weldpool surface are simulated, the influence ofdifferent pulse current parameters to the instantaneous fluctuation behavior ofweldpool surface is studied, and simulation results are validated by experimentalresults.The results show: weldpool surface fluctuations induced by arc pressure havemaximum displacement and maximum velocity at the time that the transition happensfrom base current to peak current, and fluctuation displacements near the welddirection are larger than back displacements; maximum downward weldpool surfacefluctuation displacement caused by single wire droplet impact appears when the firstdroplet falls, at this time the maximum impact velocity reaches-35m/s, the averagevelocity of ripples spreading is about2.5m/s; double wire GMA weldpool surface has maximum downward fluctuation amplitude-1.0mm approximately at the dropletimpact time, the maximum velocity is up to-48m/s, then the fluctuation displacementsweaken pretty rapidly under the effects of liquid metal viscous resistance and thesurface tension, ripples produced by back wire droplets impact are with more completeforms on the weldpool surface. Overall, fluctuations induced by the arc pressure havelarger scope on the surface, but smaller amplitude, and attenuated most powerfully.The fluctuations on the double wire GMA pool surface can promote metal melting infront of the pool, but no substantive effect to the ripples forming on the tail of theweldpool. Under the conditions of the material parameters and welding processparameters used in this study, fluctuations in the adjacent pulse cycle have nointerferences. The simulation results and experimental results of single wire GMAWweldpool surface fluctuations basically coincide.Adjusting the program, take a300A peak current and the base current is constant,the weldpool surface fluctuations resulted from arc pressure are calculated, and theinstantaneous fluctuations of double wire GMA weldpool surface induced by thedroplet impact are simulated in turn when the welding current is increased to200A,250A. The results show that: increasing peak current causes increasing fluctuationdisplacements and increasing velocities of weldpool surface accordingly, but thefluctuation cycle does not change too much; After the welding current increases, boththe fluctuation displacements and velocities of weldpool surface appear nearly linearattenuation phenomenon.Study of this subject will provide a solid foundation to deeply understanding ofthe mechanism of double wire GMA welding and optimizing of welding currentparameters.