A two-dimensional friction stir welding (FSW) process model has been developed. The fully coupled model is based on fluid mechanics and handles the solid state material transport during welding as a laminar, viscous flow of a non-Newtonian fluid past a rotating circular cylinder. The heat necessary for the material softening is generated by deformation of the material. Material flow visualisation experiments agree very well with the predicted flow field. Accordingly, material within the pin diameter is transported only in the rotation direction around the pin. Owing to the simplifying assumptions inherent in the two-dimensional model, other experimental data such as forces on the pin, torque, and weld energy cannot be directly used for validation. However, the two-dimensional model predicts many of the trends observed in the experiments. The model also predicts a deviation from the 'normal' material flow for certain combinations of welding parameters, suggesting a possible mechanism for the occurrence of some typical FSW defects.. (C) 2003 IoM Communications Ltd. Published by Maney for the Institute of Materials, Minerals and Mining.
