Grease Aging Effects on Film Formation under Fully-Flooded and Starved Lubrication

• Type: Article in International Scientific Journal
• Date: 2015

Authors

Jorge Seabra (Author) FEUP; Tiago Cousseau (Author) Other; Beatriz Graça (Author) Other; Armando Campos (Author) Other

Journal

Title: Lubricants

Vol. 3

Pages: 197-221

Publisher: MDPI

Indexing

ISI Web of Knowledge - 16 Citations

Other information

Authenticus ID: P-00P-B4J

DOI: 10.3390/lubricants3020197

Abstract (EN): Several film thickness measurements were performed with three fresh and aged lubricating greases, their base and bled oils under a wide range of operating conditions using a ball-on-disc test rig with optical interferometry. The analysis of the film thickness measurements is in agreement with the observations of several authors and adds some important aspects regarding separate film properties in EHL contacts. At full film lubrication and moderate to high speeds, the bled oil showed a similar behavior of its lubricating greases. At fully-flooded condition, low speeds and thin films, it was observed that the thickener lumps play a major role on film formation, overcoming the bled oil effects. A relationship between thickener type and film formation was evidenced. The same trends were observed under starved lubrication, where the thickener type that contributes the most to locally increase the film thickness follows the order of PP > Ca > Li. The aging process of the greases was shown to change their rheological response in different manners-softening or hardening-depending on the grease formulation. Grease aging increased the film thickness under fully-flooded and starved lubrication, regardless of the level of degradation.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 25