Empirical model of effects of pressure and temperature on electrical contact resistance of metals

An important input property in the development of process models for resist ance spot welding is electrical contact resistance. A model for the pressur e and temperature dependence of electrical contact resistance was developed from established concepts of contact resistance. The key to developing the desired relationship is determining surface roughness characteristics, whi ch is experimentally problematic. To overcome this difficulty the electrica l resistance of contacting interfaces was measured as a function of the pre ssure applied across the interfaces. Using known information about the temp erature dependence of bulk resistivity and mechanical properties, a curve f itting Procedure was used to establish the desired relationship of contact resistance to pressure and temperature. This empirical model agrees well wi th experimental measurements in the regime of low applied pressure. At high pressures, predictions underestimate contact resistance, and this was attr ibuted to strain hardening of asperities at the contacting interface. The m odel also predicts that the competing effects of bulk resistance and contac t resistance will produce a peak in the variation of contact resistance wit h temperature. The model provides a suitable means for incorporating the pr essure and temperature dependence of contact resistance into process models of the resistance spot welding process. Dr Babu (babuss@ornl.gov) and Dr Santella (santellaml@arnl.gov) are in the Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA, Dr Feng is with Engineering Mechanics Corp. of Columbus, Columb us, OH 43221, USA. Dr Riemer is at the Spallation Neutron Source, Oak Ridge National Laboratory, and Dr Cohron is with Byron Products, Fairfield, OH 4 5014, USA, received 2 August 2000: accepted 7 September 2000. (C) 2001 loM Communications Ltd.