Process monitoring of friction stir welding via the frequency of the spindle motor current

Abstract

Friction stir welding is a solid-state process that is gaining preference for the joining of metals with low melting points. Despite the clear advantages of friction stir welding over traditional fusion welding, voids within the weld seam arise when improper conditions are present. The work presented in this article examines the development of an automated process monitoring system for friction stir welding. The system indirectly monitors the welding torque through the supplied current to the spindle motor. To measure the current, a clamp-on current meter was used. Our results have shown that using a simple and inexpensive clamp-on current meter provides good insight into the welding torque. Examination focused on the frequency spectrum of the current. A Fourier transform decomposed the signal into various frequencies present. The results consistently showed that when no void was present, there was a component of the current's frequency at 14 Hz. However, when the tool encountered a void, the frequency spectrum changed. The component at 14 Hz went away while content in the range of 1-4 Hz increased.

Effect of pin-profiles on thermal cycle, mechanical and metallurgical properties of friction stir–welded aviation-grade aluminum alloy

“…This plasticized region solidifies and joining occurs. 5 This process can be used for joining similar or dissimilar materials (e.g. metal-metal, plastic-plastic, and aluminum-copper).…”

A New Quality Monitoring System for Friction Stir Welded Joints of Aluminium Pipes

“…Figure 11 shows the captured current plotted over time for the friction stir weld at two different FSW with notch and FSW without notch. It was earlier proved that the spindle motor current signal is a potential source for monitoring the FSW process and the quality [33][34][35][36]. From the graphs, the various stages involved in FSW such as tool penetration, traverse movement, dwell time and tool pull out are distinguishable.…”