Measuring Film Thickness in Starved Grease-Lubricated Ball Bearings: An Improved Electrical Capacitance Method

Shetty, Pramod; Meijer, R.J. de; Osara, Jude A.; Lugt, Piet M.

doi:10.1080/10402004.2022.2091067

Cited by 18 publications

(7 citation statements)

References 39 publications

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“…In contrast to Bartz [28], these authors demonstrated that oil film thickness could be accurately measured, comparable to the precision of optical methods, by calculating explicitly the electrical capacitances outside the loaded area C O , instead of lumping its effect into a correction factor (detailed in Section 2.3). Note that these authors considered a fully flooded area including a fully established inlet area C inlet , and a cavitating area C Cav [31][32][33], whereas for starved lubrication conditions, the flooded area at the inlet of the contact will become smaller [34,35] as well as the cavitating zone. Note that since the dielectric constant of the lubricant depends on the contact pressure and temperature distribution, accurately determining the film thickness from these measurements is challenging.…”

Section: State Of the Artmentioning

confidence: 99%

“…The method of Jablonka et al [29,30], initially developed via a ball-on-glass test setup, has been applied to ball bearings (point contacts), as discussed in [35]. Since Jablonka et al [29,30] considered only the capacitive contribution of the contacts, Equation ( 4) can be rewritten as…”

Section: Capacitance-based Film Thickness Reconstruction: Jablonka Me...mentioning

confidence: 99%

“…To verify the central oil film thickness h c obtained by means of both methods under investigation, it is compared with the theoretical value of h C by the correlations of Moes [52] for a lubricant viscosity at the measured bearing temperature [35]. It is, however, well known that some correction is required in order to account for the inlet shear heating in fully flooded contacts [53].…”

Section: Measurement Of Electrical Impedance Of Roller Bearingsmentioning

confidence: 99%

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Electrical Impedance Spectroscopy for Precise Film Thickness Assessment in Line Contacts

Manjunath,

Hausner,

Heine

et al. 2024

Lubricants

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In this article, we focus on utilising electrical impedance spectroscopy (EIS) for the assessment of global and contact impedances in roller bearings. Our primary objective is to establish a quantitative prediction of lubricant film thickness in elasto-hydrodynamic lubrication (EHL) and investigate the impedance transition from ohmic to capacitive behaviour as the system shifts from boundary lubrication to EHL. To achieve this, we conduct measurements of electrical impedance, bearing and oil temperature, and frictional torque in a cylindrical roller thrust bearing (CRTB) subjected to pure axial loading across various rotational speeds and supply oil temperatures. The measured impedance data is analysed and translated into a quantitative measure of lubricant film thickness within the contacts using the impedance-based and capacitance-based methods. For EHL, we observe that the measured capacitance of the EHL contact deviates from the theoretical value based on a Hertzian contact shape by a factor ranging from 3 to 11, depending on rotational speed, load, and temperature. The translation of complex impedance values to film thickness, employing the impedance and capacitance method, is then compared with the analytically estimated film thickness using the Moes correlation, corrected for inlet shear heating effects. This comparison demonstrates a robust agreement within 2% for EHL film thickness measurement. Monitoring the bearing resistance and capacitance via EIS across rotational speeds clearly shows the transition from boundary to mixed lubrication as well as the transition from mixed lubrication to EHL. Finally, we have observed that monitoring the electrical impedance appears to have the potential to perform the run-in of bearings in a controlled way.

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Section: State Of the Artmentioning

confidence: 99%

Section: Capacitance-based Film Thickness Reconstruction: Jablonka Me...mentioning

confidence: 99%

Section: Measurement Of Electrical Impedance Of Roller Bearingsmentioning

confidence: 99%

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Electrical Impedance Spectroscopy for Precise Film Thickness Assessment in Line Contacts

Manjunath,

Hausner,

Heine

et al. 2024

Lubricants

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“…However, it requires the use of light-transmitting materials, and therefore, it cannot determine the lubrication conditions of actual ball bearings. Electrical methods [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] can be a potential solution for monitoring the lubrication conditions of non-light-transmitting materials. There are three main types of electrical methods: the electrical resistance method [16][17][18][19][20], electrical capacitance method [21][22][23][24][25][26][27], and electrical impedance method [28][29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Lubrication Condition Monitoring in EHD Line Contacts of Thrust Needle Roller Bearing Using the Electrical Impedance Method

Maruyama¹,

Radzi²,

Sato³

et al. 2023

Lubricants

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In this study, we developed the electrical impedance method which simultaneously measures the thickness and breakdown ratio of oil films in elastohydrodynamic (EHD) line contacts within thrust needle roller bearings. Initially, we theoretically demonstrated that the oil film thickness and breakdown ratio can be simultaneously measured using the complex impedance that is produced when an AC voltage is applied to EHD line contacts. To verify the measurement accuracy of the electrical method, we monitored the oil film thickness of a thrust needle roller bearing and compared it with the theoretical value. The results revealed that the oil film thickness was thinner than the theoretical value immediately after starting the test, with the breakdown ratio being greater than 0 (indicating mixed lubrication); however, the breakdown ratio decreased over time, and the oil film thickness nearly matched the theoretical value one hour after starting the test, when it is believed that running-in wear is complete (i.e., breakdown ratio ≈ 0). Furthermore, following the test, after examining the race surface, we confirmed that running-in wear had indeed occurred. These results suggest that the developed method can monitor the lubrication conditions in EHD line contacts, such as those in thrust needle roller bearings, in detail.

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“…Thirdly, capacitance measurements are used for lubrication film measurements and are highly dependent on the quality of the electrical bearing models. Therefore, models are constantly improved [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Analyzing Ball Bearing Capacitance Using Single Steel Ball Bearings

2023

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A precise modeling of the capacitance of rolling element bearings is of increasing significance over the last years, e.g. in the context of bearing damage estimation in electric drives. The complexity of a steel bearing as an electrical network makes reliable validation of calculation models under realistic operating conditions nearly impossible. A way to reduce complexity in yet realistic conditions is the use of hybrid bearings with a single steel rolling element. This helps to measure only one current path through the bearing at a time and thus, gives a much clearer picture of the contact capacitance of rolling elements in and out of the load zone. The usage of different materials comes with different thermal expansion coefficients and different elasticities, which cause a significant change in load distribution. For the first time, this work considers both of these effects in calculation and validates them with corresponding experiments using single steel ball bearings.

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Measuring Film Thickness in Starved Grease-Lubricated Ball Bearings: An Improved Electrical Capacitance Method

Cited by 18 publications

References 39 publications

Electrical Impedance Spectroscopy for Precise Film Thickness Assessment in Line Contacts

Electrical Impedance Spectroscopy for Precise Film Thickness Assessment in Line Contacts

Lubrication Condition Monitoring in EHD Line Contacts of Thrust Needle Roller Bearing Using the Electrical Impedance Method

Analyzing Ball Bearing Capacitance Using Single Steel Ball Bearings

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