Lubricant Film Thickness Distribution Research Articles

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 kc 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.

Ultrasonic measurement of lubricant film thickness distribution of journal bearing.

Most film thickness measurement methods damage the working surface of a bearing and cannot measure the minimum film thickness, making it difficult to reveal the lubrication state and warn of wear. Two non-intrusive ultrasonic methods were proposed for measuring the film thickness distribution of the bearing, i.e., the full circumferential measurement and the prediction based on limited measuring points. The ultrasonic recognition model of film thickness was built. A film thickness measuring device and its calibration device were constructed. A calibration experiment in the range of 1-150 µm and a measurement experiment of the bearing's film thickness distribution were carried out. The results showed that in the calibration range, the relative error of most recognition values was less than ±5%, and some are less than 3%. The identification accuracy of the spring model has a zoned phenomenon. The relative difference between the experimental and the simulated values of the film thickness was less than 8% under most working conditions. The predicted values of eccentricity, attitude angle, and minimum film thickness have a small difference from the simulated values, indicating that the accuracy of the measurement method is high.

On the Temperature and Lubricant Film Thickness Distribution in EHL Contacts with Arbitrary Entrainment

An understanding of mechanisms which are responsible for elastohydrodynamic lubricant film formation under high sliding conditions is necessary to increase durability of machine parts. This work combines thin-film colorimetric interferometry for lubricant film thickness measurement and infrared microscopy for in-depth temperature mapping through the contact. The results describe the effect of operating conditions such as speed, slide-to-roll ratio, ambient temperature, and sliding direction on lubricant film thickness and temperature distribution. Film thickness data shows how much the film shape is sensitive to operating conditions when thermal effects are significant, while the temperature profiles provides an explanation of this behavior.

Ultrasonic Measurement of Cylindrical Roller–Bearing Lubricant Film Distribution with Two Juxtaposed Transducers

ABSTRACTThis article describes the measurement of lubricant film thickness distribution in a roller bearing by using two juxtaposed transducers, which are excited by a new ultrasonic pulse receiver with a maximum pulse repetition rate (PRR) of 100 kHz. The experimental results demonstrate the feasibility and advantage of this method with high PRRs. The influence of rotating speed and radial load on the measured film thickness are shown to be consistent with the theoretical predictions. Skewing of the roller in the bearing is observed. A combined trigger signal is proposed to reduce the influence of the cyclical vibration of the rotor.

Elastohydrodynamic Film Thickness Mapping by Computer Differential Colorimetry

This paper describes a new experimental technique for the study of elastohydrodynamic (EHD) lubricant films. This technique, which is based on the computer processing of EHD chromatic interferograms, uses a combination of image analysis and differential colorimetry for film thickness evaluation. This approach overcomes some major limitations of conventional optical interferometry and allows the precise mapping of lubricant film thickness distribution in EHD contacts, including transient and quasistatic phenomena. The technique has been used for the evaluation of chromatic interference patterns obtained from a conventional optical test rig for rolling point contacts. Three-dimensional representations of lubricant film thickness and shape with high accuracy and spatial resolution have been obtained. The technique's accuracy has been checked and a comparison with conventional monochromatic interferometry has been done for validation. The technique's resolution has been confirmed through the observation of local film thickening just before the EHD exit constriction for both pure rolling and sliding conditions. Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, England, United Kingdom September 8–12, 1997

A non-symmetric discretization formula for the numerical solution of elasto-hydrodynamic lubrication circular contact problem

The control volume method has been employed to obtain an appropriate discretization scheme for the numerical solution of the two-dimensional Reynolds equation. A non-symmetric discretization formula has been developed and incorporated into the author's computer program. The lubricant film thickness distribution for a typical configuration of the EHL circular contact has been solved as a benchmark. Results are presented. Convergence behavior is investigated using different density of grids for computations. A comparison with the finite difference-based formula is presented. Dependence of results on the grid density is reduced in comparison with results obtained using the finite difference formula. On conclusion, an additional discussion on the discretization of the Reynolds equation is presented and further recommendations are given.