Assessment of the friction behaviour of selected base oils under oscillatory sliding conditions

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dc.contributor.advisor De Vaal, Phillip L.
dc.contributor.coadvisor De Goede, S.
dc.contributor.postgraduate Masilela, Sipho Rudolph
dc.date.accessioned 2018-12-05T08:04:58Z
dc.date.available 2018-12-05T08:04:58Z
dc.date.created 2009/06/18
dc.date.issued 2018
dc.description Dissertation (MEng)--University of Pretoria, 2018.
dc.description.abstract The ability of a lubricating oil to reduce friction in mechanical surfaces which are in relative sliding motion depends on the base oil behaviour. Previous studies have demonstrated that temperature has a significant influence on the friction behaviour of mineral and synthetic base oils by using a laboratory based friction testing machine. However, the effect of a constantly changing load under different temperature conditions has not been explored fully. In this study, the effect of an increasing load on the friction behaviour of four six different mineral base oils and a polyalphaolefin (PAO) base oil were studied using the SRV4® tribometer. The sliding surfaces were AISI 52100 steel ball and disc. The average loads (range: 50 – 250 N), temperatures (range: 40 – 120 oC), relative humidity of 20 % and a sliding speed of 0.2 m.s-1 were selected as the test conditions. The seven base oils were selected from four API base oil groups. Stribeck curves were used as a tool to characterize the friction behaviour of the base oils. The results show that for all the base oils, the coefficient of friction and the Stribeck parameter decrease gradually with the increase in applied normal load under constant temperature conditions. The increase in temperature increased the coefficient of friction and decreased the Stribeck parameter at each load stage. The external friction mechanisms dominated the friction behaviour under all test conditions. Viscosity showed a strong influence on the film forming characteristics of the seven base oils only at 40 and 60 oC. Between 80 and 120 oC, the oil-surface interactions were predominant. The results further demonstrated that effect of an increasing temperature on the coefficient of friction was bigger between 80 and 100 oC for all Group III base oils and was consistent between 40 and 120 oC for the Group III+ and PAO base oil. The highly saturated (PAO and Group III+) base oils have demonstrated good thermal stability and less reactivity compared to the less saturated base oils (GI and GIII) under all test conditions. The friction behaviour of the PAO base oil was the most affected by the presence of dissolved water. The presence of water proved to increase the friction at the sliding steel interfaces.
dc.description.availability Unrestricted
dc.description.degree MEng
dc.description.department Chemical Engineering
dc.identifier.citation Masilela, SR 2018, Assessment of the friction behaviour of selected base oils under oscillatory sliding conditions, MEng Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/67797>
dc.identifier.other S2018
dc.identifier.uri http://hdl.handle.net/2263/67797
dc.language.iso en
dc.publisher University of Pretoria
dc.rights © 2018 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.
dc.subject Unrestricted
dc.subject UCTD
dc.subject Coefficient of friction
dc.subject Stribeck parameter
dc.subject Base oil
dc.subject Viscosity
dc.subject Saturation
dc.title Assessment of the friction behaviour of selected base oils under oscillatory sliding conditions
dc.type Dissertation


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