Characterisation of friction stir spot welding process based on envelope analysis of vibro-acoustical signals

The evaluation of the relationship between the vibro-acoustical signals generated by friction stir spot welding (FSSW) process with its parameters and stages such as torque, dwell time, and tool rotation speed, is developed in this work. A dissimilar lap-joint was conducted using pure copper and AA1050 H24 aluminium alloy. The vibro-acoustical signals in Z and Y directions, and torque applied by the tool during the process have been acquired by the instrument NI USB-9234. The characterisation in the time and frequency domains of the vibro-acoustical signals has been performed in order to correlate them with the stages of processing and tool torque. The analysis has confirmed that the vibro-acoustical signals were significantly affected by changes in process forces and can thus be used as a non-destructive method for process monitoring, optimisation tasks, and control of FSSW process.