IJTC2008-71301 SIMULATION OF THERMAL EFFECTS IN STATIONARY AND SLIDING ELECTRICAL CONTACTS

ABSTRACT Sliding electrical contacts are subject to surface damage and wear, which can be enhanced by the heating at the interface arising from electrical contact resistance. For example, in electromagnetic launcher (EML) technology, thermally assisted wear processes can result in unacceptable levels of material loss at the armature-rail interface. The control of the interface tribology in sliding electrical contacts requires an understanding of the Joule heating in the vicinity of the interface. In the current study, a multiphysics numerical simulation is conducted of transient heat conduction in both a stationary and a sliding electrical contact. The interface under investigation consists of a flat-ended aluminum cylindrical pin sliding against an aluminum rail. Electrical contact resistance is modeled by introducing a thin layer of high resistivity between the pin and the rail. Results show that shortly after sliding has commenced, (1) the maximum temperature rise occurs in the bulk of the pin rather than at the interface, (2) the bulk of the Joule heat goes into the rail, and (3) that sliding can have a significant effect on the temperature field, even when the speed is quite low. INTRODUCTION Contacts that carry electrical current at high density experience significant heating at and near the interface. This heating may lead to thermal softening and melt wear, which can degrade performance. Electromagnetic launchers, for example, operate under conditions that surpass the limits of desirable metal-metal contact for efficient and reliable performance. Such issues ultimately limit the practical application of EML technology As part of an ongoing study to understand tribological mechanisms at the armature-rail interface of an electromagnetic launcher, friction and wear studies have been conducted using a recently developed pin-on-rail test apparatu