Influence of Tool Geometry in Friction Stir Welding on Material Flow Pattern

Friction stir Welding (FSW) is a new solid state processing technique that can locally eliminate casting defects and refine microstructures, thereby improving strength and ductility, increasing resistance to corrosion and fatigue, enhancing formability. FSW can also produce fine grained microstructures through the thickness to impart super plasticity. Essentially, FSW is a local thermo mechanical metal working process that changes the local properties without influencing the properties of the bulk material. The aim of the present work is to study the influence of tool geometry on material flow during friction stir welding in Aluminum & Copper Alloys. Various types of tool geometries are modeled and the resulting flow patterns are analyzed. A FSW process with varying tool geometries and advancing speeds is numerically modeled, and a thermo-mechanically coupled, rigid-viscoplastic, fully 3D FEM analysis is done to predict the process variables as well as the material flow pattern and the grain size in the welded joints. Conclusions are drawn to identify the effect of operating process parameters.