Magneto-thermo-hydrodynamic modelling of TIG welding: a 3D unified coupling of the arc-plasma and the weld pool

This work presents the development and analysis of both the physical phenomena of the TIG welding procedure, and the numerical approaches necessary to couple the arc-plasma and the weld pool. The mathematical developments, implemented numerically in the finite element method toolbox Cast3M, couple a cathode, arc-plasma and weld pool model in a robust manner. The arc-plasma and weld pool models are numerically coupled at the interface. Thus, to couple the energy conservation models, a mixed variable algebraic approach is proposed and implemented which allows for the use of domain dependent variables in a monolithic manner. Furthermore, both a partitioned Dirichlet-Neumann and a quasi-monolithic coupling algorithm were implemented to join the mass and momentum conservation models of the arc-plasma and weld pool domains. Their respective numerical performances are analysed and discussed. In order to identify key parameters in the fully coupled model, multiple sensitivity studies were performed and the importance of cathode geometry, inlet current, interface hypothesis and weld pool viscosity are discussed. Finally, a verification study for the unified 3D model was set up and discussed. The verified model is then used to simulate a fully-coupled 3D welding configuration with displacement effects, which is compared to experimental results and discussed. (author)