Thermographic procedure for the assessment of Resistance Projection Welds (RPW): Investigating parameters and mechanical performances

This study presents a non-destructive testing (NDT) thermographic procedure for assessing the quality and mechanical strength of Resistance Projection Welded (RPW) joints with rectangular embossments. We analysed twelve RPW joints by systematically varying process parameters based on a factorial design. These joints underwent flash thermography followed by mechanical tests to evaluate the maximum breaking force (Fmax). Significant statistical correlations between process parameters (time and force) and Fmax were established. Furthermore, we found a correlation (p-value 0.86) between the optically measured fused region and Fmax. Subsequently, we developed a pulsed phase thermography-based procedure for non-destructively measuring the fused region, resulting in an average difference of approximately 4 % compared to optical measurements. An empirical linear relationship was derived to correlate the welded area obtained by thermal data with Fmax, enabling the estimation of mechanical joint strength through non-destructive pulsed thermography. This research offers a promising approach for assessing the mechanical integrity of RPW joints using thermal imaging techniques.