An analytical model for prescribing the flow around the tool probe in Friction Stir Welding

The objective of this paper is to present a simple model for prescribing a 2D velocity field for the material flow in the shear layer around the probe in Friction Stir Welding (FSW). By introducing an eccentrically shaped shear layer, and assuming a linear velocity profile between the welding flow outside the shear layer and the rotating velocity flow at the probe/slicar layer interface, a robust 'model' for evaluating different, aspects of the flow is presented. The model takes into account that the material entering the shear layer in front of the probe is transferred around the retreating side of the probe, which in turn calls for a non-symmetrical flow pattern due to the accumulation of material in the shear layer at the leading side and deposition at the trailing side. Based on the model a consistent definition of the rotation zone and transition zone is presented. The model satisfies mass conservation, however, the momentum equations are not solved for. Based on this, a rough estimate of flow rates hi experimental welds can be made. Secondly, by measuring some specific dimensions from welds using marker material, material flow and resulting shear layer properties can be estimated witli the model.