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Lubricants 2018, 6(3), 82;

An Experimental Study on Starved Grease Lubricated Contacts

INEGI, Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal
ISEP-IPP, Instituto Superior de Engenharia do Porto, 4200-072 Porto, Portugal
FEUP, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n, 4200-465 Porto, Portugal
Author to whom correspondence should be addressed.
Received: 17 July 2018 / Revised: 27 August 2018 / Accepted: 6 September 2018 / Published: 10 September 2018
(This article belongs to the Special Issue Advances in Polymer Tribology)
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The film thickness of a ball-on-disc contact lubricated with four greases of different formulations was measured under different operating conditions until starvation. Two polymer-thickened greases and two lithium-thickened greases, formulated with base oils of different nature and/or viscosity, were tested. The central film thickness was measured under constant operating conditions (load, temperature, slide-to-roll ratio) varying only the entrainment speed. In a separate test, the film thickness was measured over time with all operating conditions set to constant. Pictures of the film thickness profile across the contact area were also registered. The results were compared with the fully flooded results. The coefficient of friction (COF) was measured in a ball-on-disc contact under equal operating conditions and the results were correlated with the film thickness findings. The different grease formulations and the influence of the operating conditions on the film thickness and COF were discussed. The polymer thickened the greases, promoting lower COF and higher film thickness, especially when there is thickener material crossing the contact which happens quite often for these greases. View Full-Text
Keywords: starvation; lubricating greases; film thickness; friction starvation; lubricating greases; film thickness; friction

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Gonçalves, D.E.P.; Campos, A.V.; Seabra, J.H.O. An Experimental Study on Starved Grease Lubricated Contacts. Lubricants 2018, 6, 82.

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