Identification of the Wear Process of a Silver-Plating Layer by Dual Acoustic Emission Sensing

A method based on acoustic emission (AE) sensing in which two AE sensors are used to measure the tribological characteristics of two interacting friction materials simultaneously in real time was assessed for the in situ measurement and evaluation of the wear process of silver plating. AE sensors were attached to a silver-plated pin and a silver-plated plate, and the two AE signals were measured simultaneously on a pin-on-plate-type reciprocating sliding tester. The resulting changes in the AE signal could be classified into three phases. Surface observations and energy-dispersive X-ray spectroscopy analyses showed that the wear of the silver-plating layer progressed in Phase I, the nickel intermediate layer was exposed and wear of the nickel progressed in Phase II, and the contact electrical resistance increased and the copper substrate was exposed in Phase III. In summary, the wear process of a silver-plating layer, which cannot be identified from the changes in the frictional resistance or the contact electric resistance, can be detected from changes in the dual AE signals. Furthermore, changes in the wear state of both the pin and plate specimens can be identified from differences in the amplitudes of the AE signals and the timing of their detection.