External authors:

• Volker Schneider ( Leibniz University Hannover )
• Josephine Kelley ( Leibniz University Hannover )
• Bela Lehnhardt ( Leibniz University Hannover )
• Marius Krewer ( Leibniz University Hannover )
• Norbert Bader ( University of Twente )
• Johannes Marx ( Leibniz University Hannover )
• Gerhard Poll ( Leibniz University Hannover )

Abstract:

This study presents a novel method for in situ monitoring of the condition of elastohydrodynamically (EHL) lubricated contacts, as occurring in rolling bearings and gears, using a capacitance-based evaluation of the electrical charging behavior. A nonlinear regression model is applied to segmented portions of the voltage response curve following a defined voltage pulse. This enables accurate extraction of the contact capacitance and parallel resistance, which reflect the thickness and electrical integrity of the EHL film. The method is validated against LCR meter readings on reference circuits, showing deviations below 5%. It is then applied to deep-groove ball bearings (6008 HSMB) under oil-air lubrication, varying temperatures (60 degrees C and 100 degrees C), and rotational speeds up to 30000 1/min. Over 500 measurements per speed step confirm the method's robustness and sensitivity to changes in lubrication regime, including detection of starvation effects. The extracted electrical parameters serve both for condition monitoring and for populating equivalent circuit models in the context of inverter-fed electric drive systems. The method thus contributes to improved understanding and monitoring of bearing durability, tribological film behavior, and electrical system integration.