Nondestructive testing of resistance spot welds using eddy current thermography.

The paper presents the use of eddy current thermography for detecting cracks in resistance spot welds. The sample is a three-sheet stack-up joined together by welding spots. Inductive Helmholtz coil is used for heating up the sample, and the thermal response of each spot is monitored using a cooled indium antimonide camera. The sequence of images captured is processed using the pulsed-phase thermography technique. The phase image is completed with a supplementary filtering operation to allow outlining defects. The result was confirmed with confocal microscopy inspection.