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 the literature allow the heat to flow through the probe volume, and the majority neglects the influence of the contact condition as the sliding condition is assumed. In this work, a number of cases is 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/work piece interface. This results in a nonsymmetrical temperature field that depends not only on the total heat generation, tool/work piece geometry and thermal properties, but also on the contact condition, the tool’s rotational speed and the assumed shear layer thicknesses. The models are implemented in FEMLAB and configured in terms of the heat source as: shoulder contribution only; shoulder and probe contribution, the latter as a volume heat source distributed in the probe volume; and 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.