Two stages of experiments are involved in the study. First are
fundamental trials with an objective of establishing whether the
C-scan technology is feasible for NDT of resistance spot welds in
aluminium. During fundamental trials, spot welds were initially
examined in the as welded condition; then the same samples were
re-examined after removal of the surface indentation by milling the
surface with a 15 mm cutter. The spot weld locations were easily
discernable in first instance by the surface indentations commensurate
with the 50 mm spherical radius of electrodes; and subsequently
by the concentrically surface milled area, which allowed the
ultrasonic scanner to be positioned symmetrically about the weld.
Upon success of the fundamental trials, advanced trials were carried
out to validate the NDT technique on resistance spot welds in real
assemblies. A conventional rechargeable hand tool with a 20 mm
abrasive disc attachment was used to provide a flat ground sheet
surface. Following NDT, all welds were either destructively peeled to
reveal the weld plug diameters, or sectioned for metallographic
examination for comparison with the ultrasonic test results