Abstract: A two-dimensional model of friction stir welding is established to study the distributions of the longitudinal residual stress and the material flow under different process parameters. In the friction stir welding process, the tangent flow constitutes the major part in material flow. The faster material flow occurs on the retreating side. In the tangent flow, the flow direction is not simple and there may exist a swirl in the material flow on the advancing side. With the increase of the translational velocity and the angular velocity of the pin, the flow becomes faster on the retreating side. But in the region where the material velocity is smaller, the effect of the variation of the process parameters is not clear. The maximum longitudinal residual stress occurs on the boundary of the heat affected zone and the longitudinal residual stress is positive near the welding line but negative near the boundaries of the welded plate. The maximum longitudinal residual stress can be increased with the argument of the translational velocity of the pin. But the change of the angular velocity of the pin does not affect the longitudinal residual stress significantly.

Key words: Material flow, Finite element simulation, Friction stir welding, Residual stress