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With the present-day electromagnetic launchers (EMLs), the choice of copper for the rail and aluminum for the armature is the most popular. There have been few published studies investigating the behavior of the copper-aluminum pair under high contact pressures and high current densities. We consider the interface between a stationary copper flat (C-110) and translating aluminum (Al-6061) pins with hemispherical and flat tips. Tests are conducted on a tribo-tester designed specially to study wear and friction of sliding electrical contacts. Electrical current to the interface is supplied by a programmable 8 V/350 A power supply. Operating conditions of the experiments are designed to yield the contact pressures of ~250-375 MPa and electrical current densities (~1-14 GA/m2) representative of a typical electromagnetic launcher, albeit at much lower sliding speeds (~0.15 m/s). The wear of the pins is quantified by measuring change in their mass and using the optical microscopy and scanning electron microscopy. Energy dispersion spectroscopy (EDS) is used to study the material transfer onto the pins. In-situ measurements during the experiments show that during the sliding process the voltage drop across the contact is negatively correlated with the friction force. The measurements of the wear patch on the pins show that as the current is increased through the contact the wear diameter also increases.
Date of Publication: Jan. 2009