Reliability of a resistance spot welding process based on characteristics parameters

In this paper, the reliability of a resistance spot welding (RSW) process is studied by monitoring the quality of the corresponding welding points. Each welding point is uniquely represented by a resistance curve over time. Five learning resistance curves, the good quality of the related welding points was verified by means of experimental non-destructive ultrasonic techniques, are available. The corresponding learning maximum, minimum and average resistance curves, as a reference to check the quality of the welding points related to different process resistance curves, are obtained. In order to estimate the quality of a generic welding point, two different parameters comparing the corresponding process resistance curve with the learning maximum, minimum and average resistance curves are considered, i.e., Euclidean distance and ascent/descent velocity. Both good quality and defective welding points are observed, where Euclidean distance allows the presence of the defect to be detected, while ascent/descent velocity allows the typology of the defect to be diagnosed.