A new way to predict the mechanical properties of friction stir spot welding for Al-Cu joints by energy analysis of the vibration signals

A new proposal for evaluating the relationship between the energy of vibration signals produced by a friction stir spot welding process and mechanical properties of dissimilar AA1050 H24 aluminum alloy–Cu lap joints is presented here. We characterized the vibration signals during the FSSW process to correlate them with microhardness and the failure load of the joints. The influences of dwell time and tool rotation speed on the mechanical properties of the join and its correlation with the energy of the vibration signals were studied. Macro images and microhardness maps of welds were also produced. The strong correlation found confirms that the energy of the vibration signals on the Z and Y axes can be used as an indicator of mechanical properties and as a novel method for weld evaluation. Finally, results based on numerical predictions are compared with the experimental failure load. The mathematical model obtained to calculate failure load values based on friction stir spot welding process parameters, also including the energy of vibration signals, improves the fit from 74.3% (with analyzed process parameters only) to 93.8% with the addition of the energy of the signal.