Friction stir welding: Thermal effects of a parametric study on butt and lap welds

The purpose of this thesis was to develop and validate finite element models of the friction stir welding process for butt and lap welds for specific experimental cases that in effect enhances the predictability of temperature evolution in the joined workpiece. Significant research has been conducted on butt weld thermal process but limited study has been conducted on lap welds. Through examination of several process parameters critical to both weld and lap weld operations insights into process characterization of process parameters could be made. In this study three dimensional finite element heat transfer models using the commercial code LS-DYNA were developed to obtain the temperature distribution in the workpiece for two types of welds, namely butt joints and lap joints. For the lap weld model a step function for thermal conductance between sheets was applied to account for varying contact resistance. The developed finite element models were validated with published experimental data. Parametric studies were performed involving both types of welds including process parameters such as tool travel rate and rotational tool velocity for different aluminium alloys.