Using a New Electrical Contact Resistance Model for Investigating Nugget Diameter Variations in Small-Scale Resistance Spot Welding

Abstract

Small-scale resistance spot welding is used frequently in various industries. The key factor that affects the welding quality is the nugget size. In this paper, the relationship between the nugget size and the input process parameters is investigated. A new practical equation is provided to calculate the electrical contact resistance that does not require the information about the contact points. To perform a simulation of the process, resistance spot welding is considered as an electrical–thermal–mechanical process in the finite element model. Thermal expansion and electromagnetic heating are considered. The film layer on the sheets is also modeled. The simulation is carried out using a three-dimensional model in COMSOL Multiphysics. Electrical contact resistance is applied using the relation that is obtained in the theoretical analysis. The results of the simulation work are validated through performing experimental validation on Hastelloy X sheets of thickness 0.4 mm. It is observed that the finite element model can efficiently and accurately determine the high-temperature contours. Also, it was concluded that increasing time and current enlarges the nugget diameter.