Aluminum alloys are well known as the materials which face difficulties in weldability due to the high heat conductivity, thermal expansion coefficient, the sensitivity of hot crack, different solubility of the hydrogen content between sold and liquid phase and the existence of the oxide-layer on surface. A solution of the methods to increase the weldability in aluminum alloys is removing the oxide layer on aluminum surface by adopting the variable polarity welding or alternating current welding. In this study, it is limited to the variable polarity arc welding instead of the AC welding.
According to the recent experimental result with regard to the variable polarity arc welding by Jungho Cho, the higher DCEP fraction is, the more increasing heat input in the aluminum alloy is. It is the completely different result compared with existing theory. Jungho Cho has introduced the tunneling effect and the movement of the cathode spot during DCEP to explain this contrary experimental result and proved these suggested theories by himself through experimental result with CCD camera. This paper is the follow-up study to estimate the relative heat input efficiency of the DCEP compared with DCEN by introducing the numerical analysis of the weld pool in aluminum alloy applied to the variable polarity arc welding with the Flow-3D which is following the VOF method to track the free surface. In addition, the arc heat source, arc pressure, electromagnetic force, Marangoni flow regarding the variable polarity GTAW have been applied to the boundary conditions and governing equations such as the conservation of the mass and momentum and energy.
As a result of analysis, it has been confirmed that the experimental result by Jungho Cho can be reproduced successfully through the CFD analysis and there are differences between variable polarity and fixed polarity welding source as well. This developed model will be expected to estimate the relative heat input efficiency of DCEP/DCEN while VP GTAW by comparing the experimental result with equal welding condition.