Finite element studies on friction stir welding processes of tailored blanks

Although friction stir welding (FSW) has been successfully used to join materials that are difficult-to-weld or unweldable by fusion welding methods, it is still in its early development stage and, therefore, its potential has not been fully exploited yet. FSW appears to be a very promising process for tailor-welded blanks to overcome the difficulties encountered in traditional fusion welding processes for obtaining a sound welding with good nugget integrity. In this paper the friction stir welding process for tailored blanks of aluminum alloy is investigated through a FEM developed by the authors. In particular FSW for sheets with different thicknesses is studied. For each setup a different welding tool is designed, an extra nuting angle is considered, and numerical simulations are performed in order to predict the feasibility of the process, the final shape of the welded blank, and the distribution of the main process variables, i.e. temperature, strain and strain rate. It is found that a quite large range of different thicknesses can be successfully friction stir welded with good nugget integrity.