Tool Temperature and Process Modeling of Friction Stir Welding

Friction stir welding (FSW) has many advantages rather than fusion welding, but details of internal phenomena during its processes have not yet been clarified. In this study, a thermo-mechanically coupled process model was developed to investigate FSW phenomena inside a tool and workpiece. As a workpiece, 6061-T6 aluminum alloy was employed. The system of FSW process model includes several thermal boundaries. Among heat flows through these boundaries, heat transfers into the exterior of the system become more sensitive to tool and workpiece temperatures than heat transfers within the system. This paper especially focused on a heat transfer coefficient at a workpiece bottom, and optimized it through experiments and finite element method (FEM) analyses. The tool temperatures during FSW were measured with a special tooling system with imbedded thermocouples within a tool. As a result, an analysis model that is able to investigate details at a wide range of traverse speeds was developed for practical high speed welding. Then, the accuracy of developed FEM model was validated with them. Finally, the temperatures and stress distribution around workpiece/tool interfaces were investigated with the developed model.