An in situ experimental method for monitoring the viscosity change and oil amount during the sliding test

This study measures the changes in the viscosity and oil volume of lubricants in a vacuum sliding test under starved EHL to evaluate the lubrication life of a small amount of lubricants, and investigates their time transition and a mechanism of lubrication life. Starved EHL is observed in ball beari...

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Main Authors: Hiroshi Shiomi, Shingo Obara
Format: Article
Language:English
Published: Frontiers Media S.A. 2025-03-01
Series:Frontiers in Mechanical Engineering
Subjects:
Online Access:https://www.frontiersin.org/articles/10.3389/fmech.2025.1522524/full
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author Hiroshi Shiomi
Shingo Obara
author_facet Hiroshi Shiomi
Shingo Obara
author_sort Hiroshi Shiomi
collection DOAJ
description This study measures the changes in the viscosity and oil volume of lubricants in a vacuum sliding test under starved EHL to evaluate the lubrication life of a small amount of lubricants, and investigates their time transition and a mechanism of lubrication life. Starved EHL is observed in ball bearings lubricated with a small amount of lubricant, which require low friction torque even at high speeds, such as bearings used in artificial satellites. Under starved oil conditions, the oil film formed in the contact area becomes thin, so it is important to accurately estimate the oil film thickness in order to avoid solid contact. Since viscosity and oil volume affect the oil film thickness in the contact area, it is important to know how they change during the test. In this study, a method was proposed to measure viscosity and oil quantity without breaking the vacuum during a sliding test using a small amount of oil in a vacuum. Using this method, changes in viscosity and oil quantity until the end of lubrication life were measured in a sliding test using a small amount of MAC. As a result, an increase in viscosity and a decrease in oil quantity were observed. The measured results discussed the relationship between the increase in viscosity and the frictional work or sliding distance and indicated that the lubrication condition at the end of lubrication life was severely starved.
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spelling doaj-art-83fe28435ef44433b8bd179ee76b10ee2025-08-20T03:02:16ZengFrontiers Media S.A.Frontiers in Mechanical Engineering2297-30792025-03-011110.3389/fmech.2025.15225241522524An in situ experimental method for monitoring the viscosity change and oil amount during the sliding testHiroshi ShiomiShingo ObaraThis study measures the changes in the viscosity and oil volume of lubricants in a vacuum sliding test under starved EHL to evaluate the lubrication life of a small amount of lubricants, and investigates their time transition and a mechanism of lubrication life. Starved EHL is observed in ball bearings lubricated with a small amount of lubricant, which require low friction torque even at high speeds, such as bearings used in artificial satellites. Under starved oil conditions, the oil film formed in the contact area becomes thin, so it is important to accurately estimate the oil film thickness in order to avoid solid contact. Since viscosity and oil volume affect the oil film thickness in the contact area, it is important to know how they change during the test. In this study, a method was proposed to measure viscosity and oil quantity without breaking the vacuum during a sliding test using a small amount of oil in a vacuum. Using this method, changes in viscosity and oil quantity until the end of lubrication life were measured in a sliding test using a small amount of MAC. As a result, an increase in viscosity and a decrease in oil quantity were observed. The measured results discussed the relationship between the increase in viscosity and the frictional work or sliding distance and indicated that the lubrication condition at the end of lubrication life was severely starved.https://www.frontiersin.org/articles/10.3389/fmech.2025.1522524/fulloil degradationstarved EHLviscosity measurementlubrication lifevacuumvisualization test
spellingShingle Hiroshi Shiomi
Shingo Obara
An in situ experimental method for monitoring the viscosity change and oil amount during the sliding test
Frontiers in Mechanical Engineering
oil degradation
starved EHL
viscosity measurement
lubrication life
vacuum
visualization test
title An in situ experimental method for monitoring the viscosity change and oil amount during the sliding test
title_full An in situ experimental method for monitoring the viscosity change and oil amount during the sliding test
title_fullStr An in situ experimental method for monitoring the viscosity change and oil amount during the sliding test
title_full_unstemmed An in situ experimental method for monitoring the viscosity change and oil amount during the sliding test
title_short An in situ experimental method for monitoring the viscosity change and oil amount during the sliding test
title_sort in situ experimental method for monitoring the viscosity change and oil amount during the sliding test
topic oil degradation
starved EHL
viscosity measurement
lubrication life
vacuum
visualization test
url https://www.frontiersin.org/articles/10.3389/fmech.2025.1522524/full
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