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

Abstract

An important input property in the development of process models for resistance spot welding is electrical contact resistance. A model for the pressure 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, which is experimentally problematic. To overcome this difficulty the electrical resistance of contacting interfaces was measured as a function of the pressure applied across the interfaces. Using known information about the temperature dependence of bulk resistivity and mechanical properties, a curve fitting procedure was used to establish the desired relationship of contact resistance to pressure and temperature. This empirical model agrees well with experimental measurements in the regime of low applied pressure. At high pressures, predictions underestimate contact resistance, and this was attributed to strain hardening of asperities at the contacting interface. The model also predicts that the competing effects of bulk resistance and contact resistance will produce a peak in the variation of contact resistance with temperature. The model provides a suitable means for incorporating the pressure and temperature dependence of contact resistance into process models of the resistance spot welding process.

Metodologia Não Destrutiva de Parametrização da Queima do Zinco no Processo de Soldagem a Ponto por Resistência

“…Isto é devido as suas características metalúrgicas e elétricas que impõem dificuldades na operação de soldagem, podendo comprometer a qualidade final da solda realizada. Neste contexto, [5] observaram que, o amassamento das asperezas do zinco, provocada pela pressão dos eletrodos contribui para a redução da resistência de contato entre chapas e, entre eletrodo e chapa. Já [6] descreveram que a menor resistividade elétrica apresentada pelo zinco justifica a utilização de níveis maiores de correntes necessárias à formação do ponto de solda.…”

The estimation of the contact interface temperature during resistance spot welding of zinc coated steels using numerical technique

“…Classical theory states the electrical contact resistance will fall with an increase in temperature and pressure due to the softening, yielding, and eventual melting of contacting points on the contact surface [1][2][3]. Recently, an increasing electrical contact resistance with temperature until a peak has been proposed using an empirical model [4]. This increasing trend has also been experimentally measured with a Gleeble machine as well as during an experimental ex-situ device [5][6].…”

Finite element analysis of the thermo-mechanical behavior of the resistance spot welding

“…Simulation in order to prevent convergence transition problems between values should be smooth. The concept of plastic deformation ends when it begins to melt, however this incident fails in the package simulation programs yet, special attention is required to show to solidified metal simulation [10,11].…”