Heat Source Models in Simulation of Heat Flow in Friction Stir Welding

The objective of the present paper is to investigate the effect of including the tool probe and the material flow in the numerical modelling of heat flow in Friction Stir Welding (FSW). The contact condition at the interface between the tool and workpiece controls the heat transfer mechanisms. The convective heat transfer due to the material flow affects the temperature fields. Models presented previously in literature allow the heat to flow through the probe volume, and the majority of them neglect the influence of the contact condition as the sliding condition is assumed. In the present work, a number of cases are established. Each case represents a combination of a contact condition, i.e. sliding and sticking, and a stage of refinement regarding the heat source distribution. In the most detailed models the heat flow is forced around the probe volume by prescribing a velocity field in shear layers at the tool/workpiece interface. This results in a non-symmetrical temperature field that depends on not only the total heat generation, tool/workpiece geometry and thermal properties, but also on the contact condition, the rotational speed of the tool and the assumed shear layer thicknesses. The models are configured in terms of the the heat source as i) shoulder contribution only, ii) shoulder and probe contribution, the latter as a volume heat source distributed in the probe volume and iii) shoulder and probe contribution distributed at the contact interface, i.e. as a surface flux in the case of sliding and as a volume flux in the shear layers in the case of sticking.