Vol.19, No.3, 2019, pp. 195–209
UDC:

Friction stir welding (FSW) has become an important welding technique to join materials that are difficult to weld by traditional fusion welding. The model in this study is a simplified version of the thermomechanical model developed by Zhu and Chao for FSW of aluminium alloy A6061-T6. Zhu and Chao presented nonlinear thermal and thermomechanical simulations using finite element analysis code - Ansys APDL 16.2. They initially formulated a heat transfer problem using a moving heat source, and later used the transient temperature outputs from thermal analysis to determine maximum temperature, Von Mises stress, equivalent plastic strain and residual stresses in welded plates via a 3D elastoplastic thermomechanical simulation. In the first part we fixed the rotation speed and varied the welding speed (600 rpm; 80, 100, and 140 mm/min). The objective is to study the variation of transient temperature and distribution of Von Mises stress, equivalent plastic strain and evaluate the residual stress in a friction stir welded plate of A6061-T6. Results show that the simulation peak temperature is approximately near the measured one. However, the peak temperature of welded joints increases by increasing the welding frequency rotation for the same tool profile and welding speed. Residual stresses are affected by the FSW process, moreover, processing parameters influence the types of resultant stress, welding temperature and mixing. An increase in welding speed apparently has led to an increase in the residual stress. Residual stresses found by this FE model have never exceeded 54 % of the elastic limit. We conclude that the model gives a good result in terms of stress and the obtained results give a good theoretical basis for aluminium welding by FSW.

Keywords: FSW process, numerical medialization, Von Mises stress, plastic equivalent strain, residual stress