SUMMARY

The interface of an electrical contact, either stationary or dynamic, is a complex environment as several different physical phenomena can occur simultaneously at different scales of observations. The main motivation for this work stems from the need to provide means for accurate determination or prediction of the critical contact parameters viz., temperature and contact resistance. Understanding the behavior of electrical contacts both static and dynamic under various operating conditions can provide new insights into the behavior of the interface. This dissertation covers three major topics: (1) temperature rise at the interface of sliding bodies, (2) study on static electrical contacts, and (3) study of factors influencing behavior of sliding electrical contacts under high current densities. The significant contributions of the work are: A least squares regression-based methodology was developed for obtaining the steady-state temperature distribution at the interface of two sliding bodies, with arbitrary initial temperatures and subjected to Coulomb and/or Joule heating. This model is first of its kind and enables the prediction of full temperature field. A multi-scale model, which closely related to the multi scale nature of rough surfaces, is developed to predict the electrical contact resistance. This model, based on the JS multi-scale contact model, overcomes the sensitivity to sampling resolution inherent in many asperity based models in the literature. The phenomenon of voltage saturation in both static and slidng electrical contacts was demonstrated experimentally. The effect of load and surface roughness on voltage saturation was also demonstrated experimentally. An explanation based on the softening of the interface was proposed rather than more widely referred hypothesis of recrystallization. If the contact voltage is well below the saturation voltage then the interface behaves as an Ohmic resistor, or else the knowledge of current level also becomes important. The behavior of sliding interfaces of aluminum–copper (Al–Cu) and aluminum–aluminum (Al–Al) are analyzed under high current densities. Experimental results are presented that demonstrate the influence of load, speed, current and surface roughness on coefficient of friction, contact voltage, contact resistance, interface temperature and wear rate.