Mechanisms of interfacial degradation and signal waveform distortion in brush-ring sliding electrical contacts

Interfacial degradation during sliding electrical contact critically influences the signal integrity of brush–ring systems, yet its role in waveform distortion remains poorly understood. In this study, a synchronized tribological–electrical test platform was developed to directly correlate interfacial evolution with time-domain signal responses in copper–graphite brush–ring contacts. Progressive sliding over 80,000 cycles led to three distinct friction stages dominated sequentially by ploughing, adhesive, and abrasive–oxidative wear. Concurrently, the transmitted signal evolved from a near-sinusoidal waveform to a severely distorted triangular profile. Signal distortion was found to be weakly related to friction coefficient variations but strongly governed by the formation and evolution of friction-induced interfacial films. Graphite-rich and copper-oxide-containing films increased surface roughness and contact resistance from 0.23 to 0.68 mΩ, resulting in a rise in distortion ratio from 11% to 194% and an associated phase shift. These findings demonstrate that signal waveform integrity is primarily controlled by interfacial film evolution, providing mechanistic insight for tribological interface design in sliding electrical contacts.