Numerical and Experimental Studies on Friction Stir Welding of AA 7068-T6 for different welding speeds

Abstract

A three dimensional CFD model has been developed to investigate the effect of welding speed in the friction stir welding of AA 7068-T6 aluminium alloy. Numerical simulations were carried out using the RNG k-e turbulence model. Three welding speeds, viz. 30 mm/min, 45 mm/min and 60 mm/min have been considered for the simulation. The tool rotational speed has been kept at 1100 rpm and the axial force at 7 kN. Three weld joints have been fabricated with identical parametric combinations. Peak temperatures for the three cases have been measured using a thermal imager. The quality of the joints fabricated has been evaluated by visual inspection and microstructure studies. The numerical study supported by the experiments has revealed that an increase in the welding speed decreases the peak temperature. The formation of voids seems to be a consequence of incomplete stirring induced by increased welding speed. The measured values of peak temperatures have been higher than the predicted values. The developed model has predicted temperatures with a maximum error of 3.34%. The developed CFD model can be used for optimizing FSW process without carrying out expensive experiments.