Measurements of fluid flow in weld pools

Understanding the fluid flow in weld pools contributes significantly toward controlling the heat distribution in the base material and the mass distribution of molten base and additive materials. Currently, most investigations focus primarily on numerical models, due to the experimental difficulties associated with the challenging environment in and around the weld pool. Numerical simulations based on computational fluid dynamics are currently addressing the dynamic behaviour of weld pools, such as melting, solidification, temperature and velocity fields; these results provide information about conditions inside the weld pool that is impossible to gain experimentally. However, there is still a shortage of experimental validation to support these models. In this thesis, experimental methods are applied to study the fluid flow of the weld pool in both arc and laser generated weld pools. The general conclusions from the experimental study provides some suggestions for understanding the fluid flow in the weld pool, such as flow asymmetry, rotational flow and interface instabilities. For example, the interface instabilities can affect the energy and mass distribution. Describing these instabilities numerically requires three dimensional flow models. Moreover, the current experimental results question the validity of works where the surfactant concentration is assumed to be constant in the weld pool without consideration of dynamic diffusion and convection. This work has focused on experimental measurement of the fluid dynamics of weld pools, and current results provide a number of validation cases for further numerical simulations.Materials Science & EngineeringMechanical, Maritime and Materials Engineerin