Numerical Simulation Of Friction Stir Welding Process Based On Computational Fluid Dynamics

Friction Stir Welding is one solid-state joining method, which iswidely applied in aluminum alloys welding. In this paper, the single phasefluid model, double phase model with continuous fluid and dispersed solidparticle, heat transfer model are established on the basis of computationalfluid dynamics, which aim to reveal the mechanism of defects formationand property of welding joint.The investigation of single phase fluid flow of quasi-steady FrictionStir Welding process is conducted firstly. The fluid material made ofaluminum alloys is assumed to be incompressible and laminar. The fluidmodel based on Rotating Reference Frame is established with rotatingdomain beneath the shoulder and stationary domain outside the shoulder,which are connected with domain interface. The Frozen Rotor interfacemodel is first utilized to obtain approximate results and then restart withStage interface to obtain the best results.The typical defect in Friction Stir Welding joint-Residual OxideDiscontinuities is investigated secondly. The source of amorphous oxideparticle is located on the butt surface of base metal via variable controlmethod, metallography, EDS and TEM. Eulerian-Lagrangian fluid andsolid particle double phase model is established on the basis of RotatingReference Frame. And the motion profile of solid particle is visualizedwith Lagrangian particle tracking method. In those cases, the mechanismof ROD formation is revealed.Heat transfer model of Friction Stir Welding is finally establishedwith the assumption that the heat flux is made of two surface heat flux on the shoulder and pin separately. The transient problem is converted torelatively simple stationary convection-conduction problem after makingthe coordinate transformation. The peak temperature occurs on theshoulder below solidus temperature of2219aluminum alloys, whichreveals there is no liquid phase generated in this process.