Inspection of the physical contact between two steel sheets by means of a potential drop technique

In this paper, we propose a potential drop technique for inspecting the physical contact between two steel sheets. One of the important targets in this study is the examination of spot welds in the steel sheets and we evaluated this using the electrical circuit in a welding machine. First, we used numerical analysis to analyze the changes in the potential drop due to the size of the physical contact between the steel sheets. In the conventional setup for spot welding, two steel sheets are inserted between two Cu electrodes. In the analysis, the current is supplied through two terminals, one on the surface of each electrode, and the potential drop is measured between two other terminals, again, one on the surface of each electrode. The validity of the analysis was confirmed experimentally where the physical contact between the steel sheets was modified by inserting shims between the sheets.