Experimental and numerical study on failure of friction stir welded joint in conventional and bobbin tool using GTN model

The main purpose of this study is experimental and numerical investigation on failure of friction stir welded AA6061-T6 joint under tensile-shear test using damage model. In the past, due to the problem of development in high-strength welds, fatigue and corrosion resistance in aluminum, the use of welding in these industries was limited. However, with the advent of the friction stir welding process, aluminum alloys has been considered and their welding has become possible. The use of lightweight materials, especially aluminum alloys in the automotive, shipbuilding and aerospace industries is increasing rapidly and the operation of these alloys requires the development of joining and welding methods. Therefore, the study and analysis of friction stir welding is substantial. In this study Gurson-Tevergaard- Needleman (GTN) model is utilized to study the failure of welded joint. A finite element (FE) model is developed to simulate failure of the welded joint under tensile-shear test. To validate the model, 8 samples including 4 samples of friction stir welds with conventional tool and 4 samples with bobbin tool are welded with different welding parameters to obtain failure. The comparison between experimental and FE model results shows that the GTN model has a good reliability to predict the failure force. In addition, the results show that the FE model can predict truly the starting of failure in the welded joint.