Numerical analysis of the ultrasound induced arc pressure increment in plasma arc welding

A mathematical model is developed to investigate numerically the interaction mechanism between the ultrasonic vibration and the plasma arc in a plasma arc welding (PAW) process variant, i.e. ultrasonic assisted keyholing PAW (U-PAW). It is found that when ultrasound is exerted into the plasma arc from the tungsten electrode, the arc pressure is greatly increased, but the increment at different regions in arc space is varied. Near the anode surface, the difference between the peak value of the plasma arc pressure in U-PAW and the arc pressure in PAW is much larger than the additional acoustic pressure, indicating that the plasma arc pressure in U-PAW is not simply a superposition of plasma arc pressure and ultrasonic pressure. Experimental measurements of plasma arc pressure at anode are conducted in both PAW and U-PAW, and the numerical simulation results are in good agreement with the measured ones. This work lays foundation for understanding the underlying phenomena in U-PAW.