Numerical analysis of plasma arc welding process for aluminium alloy

Three-dimensional time dependent governing equations in non-orthogonal body fitted curvilinear coordinate system for analysis of variable polarity plasma arc welding (VPPAW) process were established. The numerical analysis of VPPAW process for aluminium alloy LF6 was conducted via the developed models, which laid a foundation to guide procedure optimisation for VPPAW process. Functions between temperature and thermophysical properties for aluminium alloy LF6 were established. Fluid flow field, thermophysical properties, temperature field and free surface deformation of the keyhole weld pool were coupled into computation. Effect of wire filling on the geometry of the molten pool and double sided weld reinforcements was considered in the simulation. Dynamic evolutions of geometrical dimensions versus time for both weld pool and keyhole were simulated through the developed computational routines. Moreover, effects of welding current, travel speed and also heat input on geometry and dimensions of the keyhole weld pool as well as fluid flow field in the molten pool for the main welding stage were numerically analysed and compared. In addition, VPPAW experiments were conducted. Effect of welding heat input on areas of front and back weld reinforcements was experimentally analysed, and the experimental measurements for weld cross-sections agreed the predicted ones well.