Method for contact resistance determination of copper during fast temperature changes

Abstract

Contact resistance is crucial for temperature evolution at the fusion zone during resistance welding. In this paper, we introduce a new approach to determinate specific electrical contact resistance $${\rho }_{cont,el}$$ for a constant contact pressure during dynamic temperature changes. We utilize total resistance curves from a specially designed experimental apparatus, implement them in a FEA-method and use this simulation method to separate material and contact resistance to calculate the specific contact resistance. The experimental setup is especially designed to achieve homogenous contact conditions during dynamic heating from real welding currents. We perform numerical and experimental validation of the developed determination method, including the usage of temperature measurements in the region of the fusion zone. Finally, we present pressure- and temperature-dependent data for specific contact resistance of Cu-ETP R200 (CW004A, soft) up to temperatures of 400 °C for two given contact pressures (64 MPa and 160 MPa) and a variation of contact surface properties. The data show a decrease in contact resistance with increasing temperature and pressure. Additionally, the properties of the surface show a strong influence on the contact resistance values.