Abstract: Based on analysis of plasma arc shape by high-speed camera and thermogenesis mechanism in positive and reverse polarity period, the models applied with Gaussian plus double ellipsoid combine heat source model are built. Using ANSYS parametric design language(APDL) programming language achieved alternative cycles of heat load that corresponding to the actual variable polarity welding parameters, and calculating the temperature field and molten pool shape of aluminum alloys variable polarity plasma arc welding. Comparing molten pool penetration depth under different currents and welding speeds, and verifying the heat source model accuracy in actual welding. The results provides theoretical basis to the characteristics of variable polarity plasma arc heat source shape, thermogenesis mechanism and polarity plasma arc force, and conduces to select reasonable welding parameters.

Key words: Numerical simulation, Temperature field, Variable polarity plasma arc welding