Figure - available from: Tribology Letters
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A schematic diagram of the optical setup for the ratiometric laser induced fluorescence technique employed in the Sapphire Bearing Rig (SBR). Top: Hardware set-up of the SBR in the fluorescence mode; Bottom: Detail of the optical paths for the ratiometric fluorescence imaging (Color figure online)
Source publication
This paper describes a unique experimental set-up constructed for studies of lubricant behaviour in an operating rolling element bearing including in situ quantitative measurements of film thickness in and around the element-raceway contact. The set-up is based on a deep groove ball bearing in which the outer race is made of sapphire to allow full...
Citations
... They combined laser-induced fluorescence and light emitting diode (LED) illumination with two high-speed cameras and simultaneously observed the radial and axial directions of the bearing up to a rotational speed of 5,000 min -1 . Chennaoui et al. (2022) measured the oil-film thickness between the ball and outer ring under oil-lubricated conditions using a 6206-type deep-groove bearing with a sapphire outer ring by applying the ultrathin film interferometry method, commonly used in ball-on-disc tests. A triggering system enabled the capture of images when a ball passed the uppermost point of the bearing, independent of the rotational speed, and fluorescence methods were used to observe the oil distribution. ...
Deep-groove ball bearings for the eAxles of electric vehicles must adapt to higher rotational speed conditions because the speed of eAxle motors have been increasing as the size and weight of the motors decrease. Therefore, understanding the oil-lubricated conditions inside ball bearings at high rotational speeds is essential for optimizing their design for eAxles. To clarify the oil-lubricated conditions inside ball bearings at these high speeds, a new test apparatus was developed. This apparatus is capable of simultaneously measuring the friction torque of deep-groove ball bearings, the oil-film thickness on the rolling balls, and observing the oil distributions inside the bearings at rotational speeds up to 20,000 min ⁻¹ . The oil-film thickness was measured using three-wavelength optical interferometry, and the oil distribution was observed using fluorescence. It was found that the oil-film thickness became constant at rotational speed conditions exceeding approximately 7,700 min ⁻¹ . Oil starvations were observed on the raceway around the rolling ball, and these regions increased with increasing rotational speeds. Additionally, in the deep-groove ball bearing with a crown-shaped cage, the oil was mainly supplied to the rolling balls from the inner ring side through the space between the cage claws that held the ball. Moreover, the amount of mixed air tended to increase as the rotational speed increased to approximately 7,700 min ⁻¹ . Those oil starvations and increasing air in oils were considered to be factors that prevent the increase in oil-film thickness. The findings of the reported study will contribute to the development of multibody dynamic technology for high-speed ball bearings necessary in electric vehicles.
... For investigating the behaviors of lubricating oil films inside bearing, many studies employed ball-on-disc experiments using optical interferometry [3][4][5][6][7][8][9] or computational analyses based on the elastohydrodynamic lubrication (EHL) theory [10][11][12][13] to determine the oil film thickness, and only a few studies used actual bearing configuration. In a recent study, a sapphire outer ring with actual bearing shape was used for measuring the film thickness with optical interferometry [14], but the maximum rotational speed was 2,900 min −1 . No report can be found on the state of lubrication in actual bearings at speeds above 10,000 min −1 . ...
High-speed deep-groove ball bearings for the eAxle of electric vehicles must adapt to higher rotational speed conditions, because eAxle motor speed increases to downsize the unit. Therefore, it is necessary to clarify the lubrication process of ball bearings at the high rotational speeds to prevent seizure and wear. The oil-film thickness between outer-ring and ball, and the oil distribution around balls in 6008 deep-groove ball bearings incorporating experimental quartz outer rings were measured under high-speed conditions, with speeds exceeding 20,000 min⁻¹. These measurements were carried out by employing the three-wavelength flash-light optical interferometry method and the UV-LED light-induced fluorescence method. It was found that the oil-film thickness did not increase even when the rolling speeds increased, which is in contrast to the EHL theory under sufficient lubrication condition. Contrary to the EHL theory, these phenomena can be attributed to the oil starvation and lowering effective viscosity of oil containing bubbles resulting from aeration under high-speed conditions.
... When Coy et al. [8] compared the thrust bearing film thickness measurements with the ball-on-disc test, they found that the major cause of the bearing's decreasing thickness was an inadequate supply of grease in the contact region. Utilizing the optical method, Chennaui M et al. [9] found that the oil film thickness in the contact area of a model bearing is lower than that predicted by the elastohydrodynamic lubrication (EHL) theory due to oil starvation. Gonçalves et al. [10] discovered that as soon as starvation starts, the grease film thickness decreases with increasing speed. ...
The lubrication performance of bearings is greatly influenced by the distribution of the lubricant. In this study, a cylindrical rolling bearing test rig was constructed and presented. The distribution of grease and lubricating oil along the contact region was examined using the laser-induced fluorescence technique, and the thickness of the layer was determined. The lubricating oil and grease layer thickness distribution map was acquired. The effects of supply amount, thickener content, and speed on grease distribution were examined. Mechanisms for replenishing the line contact area were investigated.
... [14], Chennaoui et.al. [15] or by Liang et.al. [16,17]. ...
Grease is important lubricant for ball bearings as it is used much more often than oil. However, mechanism of the lubrication is not completely clear, especially concerning the role of the thickener in the lubricating process. It was shown that contribution of the thickener to film thickness build-up varies with operating conditions. Also, its influence on the resistive torque of the bearing was proved. However, all studies were in-direct showing its effects. This paper presents new in-situ fluorescence method of the grease constituents’ observation, where both, thickener, and base oil can be observed independently. Two different fluorescence dyes are used to distinguish grease constituents with the use of different microscope setup. Moreover, the new method was tested on two different test rigs. First is typical ball on disc test rig widely used for study of elastohydrodynamic lubrication. Second is ball on ring test rig which more closely represents radial ball bearing conditions. It was shown that thickener engagement is very different for each geometrical configuration.
This book was written to benefit potential postgraduates and researchers who are doing research in Rolling Contact Bearings. As I had experiences in teaching and learning, I know it is difficult to digest information from journals, therefore, to make it easier to you to read, I had arranged it into
1. Overall summary
2. Problem statement
3. Methodologies
4. Findings
5. Future research
6. List of Future research
7. Literature matrix
If you study the contents of this book, you may find it easy to identify the names of analysis, methods, models, tests, experiments related to the subject matter. All the references quoted here are from 2021 until 2023. Meaning that it is latest research. Hopefully this book will act as catalysts for you all to initiate your research.
The book was written using #softwaretheses and various modern AI tools. #softwaretheses was created by myself and my brother. Made in Malaysia. For those who wants to learn softwaretheses, you can meet me.
Film thickness is a direct indicator of bearing lubrication; nevertheless, measuring it in a bearing is tricky. The optical relative interference method was used to measure the central film thickness in a model rolling bearing at speeds ranging from zero to 3500 rpm in this article. The film thickness for a ball-outer-ring contact in a model rolling bearing is discovered to be different when compared to the results from the conventional ball-on-disc model. Thermal effects and starvation are investigated. The key influencing factors for replenishment in a rolling bearing are discussed.
Lubrication is very important for good working performance and long life for rolling bearings. The distribution of the lubricating oil layer outside the ball-raceway contact directly determines the formation of the lubricating oil film in the contact area. A bearing model test rig was built with the outer ring replaced by a glass one so as to realize the direct observation and measurement of the oil layer outside the ball-raceway contact area by photography. The migration of lubricating oil on the outer ring, steel ball, and cage under low speed was mainly studied. The influence of working-condition parameters such as time, speed, oil supply, and viscosity of lubricating oil was investigated.
