Oil-Bleeding Model for Lubricating Grease Based on Viscous Flow Through a Porous Microstructure

Baart, Pieter; Vorst, Bas van der; Lugt, Piet M.; Ostayen, Ron A.J. van

doi:10.1080/10402000903283326

Cited by 64 publications

(40 citation statements)

References 4 publications

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“…The SEM images were obtained by washing away the base oil by using a volatile solventpetroleum ether. The lithium grease shows a fibrous microstructure with a fine and complex network of twisted fibers [24,25]. Lithium complex grease also appeared to have a fibrous structure but with fewer junctions between the fibers in comparison with lithium grease [26].…”

Section: Microstructural Characterizationmentioning

confidence: 99%

Effect of Thickener Particle Geometry and Concentration on the Grease EHL Film Thickness at Medium Speeds

et al. 2016

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The aim of this paper was to understand the parameters influencing the grease film thickness in a rolling elastohydrodynamically lubricated contact under fully flooded conditions at medium speeds. Film thickness measurements were taken under pure rolling for six commercial greases and their bled oils. The grease film thickness was found to be higher than corresponding bled oil, suggesting the presence of thickener in the contact. No rheological properties (characterized by steady and dynamic shear) showed any direct relation to the film thickness of the studied greases. AFM measurements of the thickener microstructure, from which the dimensional properties of the thickener particles (fibers/platelets/ spheres) were estimated, showed that the relative increase in the film thickness due to entrainment of the thickener was proportional to the ratio of thickener volume fraction to the size of the fibers/platelets/spheres. Hence, with the same concentration, smaller thickener particles lead to the generation of thicker films than larger thickener particles. Next, this relation was used to establish the percentage of the thickener particles passing through the contact. Depending on the grease type, between about 1 and 70 % of the thickener particles were found to travel through the contact.Keywords EHL Á Grease lubrication Á Rheology Á Microstructure List of symbols DAverage diameter of the thickener particle (m) E 0

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Section: Microstructural Characterizationmentioning

confidence: 99%

Effect of Thickener Particle Geometry and Concentration on the Grease EHL Film Thickness at Medium Speeds

et al. 2016

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“…Microscopy methods like atomic force microscopy (AFM), scanning electron microscopy (SEM) or transmission electron microscopy (TEM), reveals micro-and nanoscale structural details, and therefore are powerful and effective tools for visualising the lubricating grease morphology [13][14][15][16][17][18]. However, in spite of the continual development and great diversity of microscopy techniques, microstructure determination of lubricating greases remains a current challenge.…”

Section: Introductionmentioning

confidence: 99%

AFM and SEM Assessment of Lubricating Grease Microstructures: Influence of Sample Preparation Protocol, Frictional Working Conditions and Composition

2016

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The microstructure of lubricating greases greatly conditions their in-service performance. In that sense, optimal testing protocols are required in order to accomplish their correct morphological characterization. This study explores and compares the suitability of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) techniques for imaging six different commercial metallic soap-based greases and two novel biopolymer-based formulations. Pros and cons of both techniques as well as the effect of sample preparation protocol were analyzed. The results revealed a wide variety of morphological characteristics depending on composition. Thus, the four anhydrous calcium-based greases demonstrated two clearly distinct microstructures (fibrous and granular) determined by the type of base oil employed. With regard to the lithium complex greases, the typically reported microstructure characterized by welldefined entangled and fibrous network was observed in both AFM and SEM techniques.As for the two biopolymer-based greases, fiber networks were also encountered.Besides this, selected greases were subjected to different tribological tests, and the effect of high-shear frictional working treatments on their microstructure was also analyzed. As a result of the friction and internal wear, the AFM results evidenced microstructural changes which depended on grease composition. Overall, the combined use of AFM and SEM techniques was demonstrated to be a powerful approach to microstructurally characterize lubricating greases.

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“…2. Similar to Part I of this paper, the oil bleed rate decreases with time, due to a decrease in the permeability of the grease, due to an increase in the thickener fraction (arising from the oil bleeding) and micro-structural changes [21]. In line with this increase in the thickener fraction, it is also possible to notice that the viscosity of the bleed-oil greatly influences the bleed rates.…”

Section: Bleed Rate Resultsmentioning

confidence: 70%

Formulation, rheology and thermal aging of polymer greases—Part II: Influence of the co-thickener content

Gonçalves

Marques

Graça

et al. 2015

Tribology International

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Oil-Bleeding Model for Lubricating Grease Based on Viscous Flow Through a Porous Microstructure

Cited by 64 publications

References 4 publications

Effect of Thickener Particle Geometry and Concentration on the Grease EHL Film Thickness at Medium Speeds

Effect of Thickener Particle Geometry and Concentration on the Grease EHL Film Thickness at Medium Speeds

AFM and SEM Assessment of Lubricating Grease Microstructures: Influence of Sample Preparation Protocol, Frictional Working Conditions and Composition

Formulation, rheology and thermal aging of polymer greases—Part II: Influence of the co-thickener content

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