Establishing relationship between optimised friction stir spot welding process parameters and strength of aluminium alloys

Friction stir spot welding is a single spot, solid state joining process and it massively replaces the traditional single spot joining of electrical resistance spot welding in automobile industries. The friction stir spot welding process parameters such as tool rotational speed, plunge rate, plunge depth, dwell time and the inherent strength properties of base metal such as yield strength and shear strength both decide the plastic flow of material under the action of rotating non consumable tool. In this investigation, three grades of aluminium alloys (AA6061, AA2024 and AA7075) were used to fabricate the joints. The process parameters were optimised using response surface methodology to attain higher lap shear tensile fracture load. And empirical relationships were developed relating these optimised process parameters and base metal strength of aluminium alloys. These relationships can be very useful to estimate the unknown optimised value of the FSSW process parameters from the known base metal strength.