Electrical Methods for the Evaluation of Lubrication in Elastohydrodynamic Contacts

Abstract

This paper reviews the electrical methods to evaluate lubrication, with the focus on elastohydrodynamic applications. The methods are based on the measurement of the electrical resistance and/or capacitance, and are used to determine the thickness of lubricating films as well as to detect asperity contact in the mixed lubrication regime. The experimental works are introduced in which these methods are used in conventional sliding and rolling/sliding tests and machine component tests including piston ring and cylinder liner, cam and follower, and gears. Also some works on the effect of electric field upon lubrication phenomena are introduced. Advantages and disadvantages of the electrical methods are discussed.

Untersuchungen zur Wirkungsweise von Mikrotexturen in elastohydrodynamischen Gleit-/Wälzkontakten

“…Jedoch sind die strahlbasierten Verfahren durch die Notwendigkeit eines optischen Zugangs (transparente Körper) oder der von ihnen ausgehenden Gefährdung und notwendigen Abschirmung (Röntgenstrahlung) meist auf stationäre Systeme mit einfacher Zugangsmöglichkeit beschränkt. Im direkten Einsatz in technischen Systemen haben sich im Wesentlichen die elektrischen Messverfahren etabliert [342]. Ist nur eine Bestimmung des Schmierungszustandes ausreichend, so kann das resistive Verfahren als die Methode der Wahl angesehen werden.…”

Correlation between solid–solid contact ratios and lubrication regimes measured by a refined electrical resistivity circuit

“…The main difficulties of the electrical methods are related to the dependency of the capacitance and resistance on the geometry of the contacting partners as well as the calibration [10]. Despite the abovementioned difficulties, the electrical methods are simple to apply even for real machine components [10].…”

“…However the main drawback of these techniques is based on the fact that at least one of the contacting surfaces must be transparent [10].…”

“…The main difficulties of the electrical methods are related to the dependency of the capacitance and resistance on the geometry of the contacting partners as well as the calibration [10]. Despite the abovementioned difficulties, the electrical methods are simple to apply even for real machine components [10]. In particular, electrical resistivity measurements provide valuable information regarding the metallic asperity contact, the governing lubrication regime and the monitoring of the sudden change between those regimes [8,9,[11][12][13][14].…”

“…Moreover, interferometric techniques are powerful tools for the precise determination of film thicknesses as well as the whole contact area being interesting for the analysis of mixed lubrication contacts [8][9][10]. However the main drawback of these techniques is based on the fact that at least one of the contacting surfaces must be transparent [10].…”