A Theoretical Model for the Dynamic Resistance in Resistance Spot Welds

Abstract

Although the behaviour of dynamic resistance has been reported to give a good indication of weld quality for the process of resistance spot welding, this resistance variable has not been widely used for the purpose of a feedback controller design as well as for the determination of a good welding condition required for a specified weld material. This is mainly due to the fact that no analytical method is at present available to describe the behaviour of the variable. This paper presents an analytical model that can predict the variation of the resistance. In this model the complicated phenomenon of the thermo-electric interaction at the interface is included to obtain both the voltage and temperature distributions in the weldment. The computed dynamic resistance based upon this model is compared with that experimentally obtained for the case of welding of mild steel. The comparison of results shows that this numerical analysis enables the behaviour of the dynamic resistance to be predicted fairly accurately.