Numerical investigation on thermo-mechanical and material flow characteristics in friction stir welding for aluminum profile joint

Friction stir welding (FSW) technology has been applied for aluminum profiles which are widely used in rail vehicles, while process and flow behavior investigations by numerical simulation technology are still insufficient as the geometric complexity of profile joint. In this study, a fully coupled thermo-mechanical model is presented for the FSW process of AA6082-T6 profile. The numerical modeling scheme is executed on the basis of rigid-viscoplastic finite element theory with adaptive re-meshing technology, which is validated firstly by experimental measured temperatures for a sheet case in literature. The temperature field and material deformation are investigated for two different rotational directions of welding tool. The material flow around the tool is visualized and elaborated using a material trajectory demonstration manner based on the point tracking method. The material flow behavior in the three-dimensional space is clearly captured, which shows that the material flow along both the horizontal and vertical directions on the advancing side is more complicated and essentially different with that on the retreating side. Especially, a “sparse material area” is found at the rear of the pin which explains the formation mechanism of void or groove defects. Furthermore, the material stir zone is also presented by the material flow characteristics and analyzed at different welding process.