Change search
ReferencesLink to record
Permanent link

Direct link
Grease in elastohydrodynamic lubrication
Luleå tekniska universitet.
1993 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The rheology of soap thickened greases has been investigated in a cone and plate rheometer and a model that includes base oil viscosity and temperature has been suggested and fitted to the results. With the use of a bouncing ball apparatus, the pressure coefficient of the limiting shear stress of the greases was determined. It is related to friction in EHL and the results verified the friction reducing properties of the soap thickeners of the grease. Film thickness in EHL of a grease lubricated point contact was measured in a ball and disc apparatus. The initial film thickness was thicker than the film thickness given by the base oil. After some seconds of running the film thickness dropped far below the base oil film thickness, because of insufficient replenishment. Replenishment was studied by looking at the distribution and flow of lubricant around the contact in the ball and disc apparatus. Primary reservoirs and primary bands close to the track of the contact, on the ball and the disc, contained small amounts of grease that constituted a potential supply of lubricant to the inlet of the contact. The majority of the grease was pushed away from the contact initially and seemed no to participate in the lubrication. Soap thickener formations were observed entering the contact in the ball and disc apparatus and cause a local increase in the film thickness that disturbed the normally horseshoe-shaped film thickness map. For lithium greases, the amount and size of the film disturbances were found to be connected with the manufacturing process of the grease and the soap thickener content. A method to evaluate the pressure fluctuations induced by the film thickness disturbances was proposed. The method was verified by comparing film thickness measurements from an oil lubricated contact and the pressure profile calculated from that, with the results from a fully numerical solution. Good agreement was found. The method was applied to a grease lubricated contact and showed significant variations in the pressure, caused by the soap thickener formations.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 1993. , 21 p.
Series
Doctoral thesis / Luleå University of Technologyy… → 31 dec 1996, ISSN 0348-8373 ; 132
Research subject
Machine Elements
Identifiers
URN: urn:nbn:se:ltu:diva-18023Local ID: 66b91650-f664-11db-ac79-000ea68e967bOAI: oai:DiVA.org:ltu-18023DiVA: diva2:991029
Note
Godkänd; 1993; 20070429 (ysko)Available from: 2016-09-29 Created: 2016-09-29Bibliographically approved

Open Access in DiVA

fulltext(33077 kB)9 downloads
File information
File name FULLTEXT01.pdfFile size 33077 kBChecksum SHA-512
bd6277884ac196de16dffa5689f30f41e0fd91c631b598c19911c111176c2b1d2b9bd3f4a3feba6ef556ee1a0f9ae40888147e9f10504b3a93c1be5b1a3dd823
Type fulltextMimetype application/pdf

Search outside of DiVA

GoogleGoogle Scholar
Total: 9 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 7 hits
ReferencesLink to record
Permanent link

Direct link