Method for in situ film thickness measurement of ball bearings under combined loading using capacitance measurements

In this study, a novel capacitance based analytical method to monitor the film thickness in a ball bearing under a combination of axial and radial load is presented. Furthermore, an extended method is presented to infer the difference between the lubricant film height on the inner ring and the outer ring of a rolling element. Numerical investigations provide the basis for describing the influence of the operating parameters on the lubricant film thickness distribution in the HERTZ’ian contact. The method for calculating the correction factor k c presented in a previous paper is extended so that it is valid for a wider operating range. This makes it possible to calculate the total capacitance of a contact from the capacitance of only the HERTZ’ian contact area. • Extension of Capacitance Formulae for Point Contact. • Formula to Calculate Film Thickness Distribution under Combined Load Cases from Capacitance Measurements. • Analytical Formula to Predict the Film Thickness Distribution between the Rolling Element and the Inner and Outer Ring.