Use of frequency-based methods for quantitative evaluation of resistance spot welds

This paper presents a comprehensive framework integrating infrared (IR) thermography, electrode surface imaging, and welding process parameters to provide robust non-destructive evaluation (NDE) of resistance spot welded (RSW) joints. Employing lock-in thermography with digital analysis of carbon copy electrode imprints, our method accurately captures variations in weld nugget characteristics linked to electrode geometry and wear conditions. Metrics such as weld area, circularity, and phase gradient magnitude extracted from thermal images highlight the influence of electrode contact conditions on the resulting weld quality. The results demonstrate the capability of thermal imaging to rapidly detect subtle weld inconsistencies arising from electrode degradation or uneven pressure distributions. This unified, data-driven approach effectively bridges traditional destructive methods and advanced NDE techniques, enabling continuous, real-time quality monitoring and enhanced weld integrity assurance in high-volume manufacturing environments.