Bearing torque characteristics of lithium soap greases with some synthetic base oils

Oikawa, Eri; Inami, Noriyuki; Hokao, Michita; Yokouchi, Atsushi; Sugimura, Joichi

doi:10.1177/1350650112442780

Cited by 8 publications

(12 citation statements)

References 7 publications

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“…A higher degree of physical entanglements was observed for Li/SS over Li/M, and CaS/M showed large spaces between the thickeners in comparison with CaS/MS (not shown). This suggests that there is an influence on the fiber interaction by the thickener concentration and base oil viscosity as is suggested in [28,29]; however, the effect on the particle shape and size is neglectable.…”

Section: Microstructural Characterizationmentioning

confidence: 84%

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: 84%

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

et al. 2016

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“…In the range of 500-2000 rpm, the bearing torque lubricated with Grease-A was about half of those with Grease-B and Grease-C. For the investigation of the cause of these torque differences, some measurements including rheological properties and grease flows were conducted. According to past reports, viscosity and channeling property are important [1,2], and hence these factors will be also confirmed.…”

Section: Grease Thickener Structurementioning

confidence: 93%

“…6. According to a past report, higher yield stress causes grease channeling and contributes to lower torque [2]. In the report, yield stresses among different type base oils with the same thickener type were evaluated.…”

Section: Rheological Parameters and Film Thicknessmentioning

confidence: 99%

“…Cousseau et al investigated the influence of grease rheological parameter for thrust bearing torques and proposed that the bearing rolling torque is dependent on the viscosity of the bleed oil [1]. Oikawa et al indicated a relationship between yield stress of greases and ball bearing torque and that higher yield stress of grease leads to channeling state in a bearing, which is effective in torque reduction [2]. Venner et al estimated the reduction of the grease film thickness in ball and roller bearings by numerical simulations of grease flows, but they did not look at the bearing torque [3,4].…”

Section: Introductionmentioning

confidence: 99%

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Effect of Formulation of Li Greases on Their Flow and Ball Bearing Torque

et al. 2016

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This paper describes a study on the effect of base oil type and thickener type on bearing torques with Li type greases. Using a ball bearing tribometer equipped with a torque sensor, friction torque behaviors were determined for model Li greases with different hydrocarbon type base oils. The results showed that the bearing torque changed with the formulation of the greases. For the clarification of the mechanisms, rheological parameter and film thickness of greases were evaluated, and the fluorescence technique was introduced to observe flow behaviors of the greases in and around EHL contact area by using a ball-on-disk tribometer, furthermore, thickener fiber structure was observed by an electron microscope. The abundance of grease around EHL contact area was different depending on thickener types. It is suggested that film thickness, flow behaviors, and thickener structure influence simultaneously on the bearing torque behaviors.

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“…Figure 11 shows the film-thickness interference images for different thickener concentrations. As the concentration of the aluminum-complex-based grease used for lubrication increased, more soap fibers appeared in the contact area, which may have increased the frictional torque [17]. In the case of the lithium-based grease, the large soap clumps tended to agglomerate at the end of the roller with a higher thickener concentration (#F).…”

Section: Film Thickness Of Roller's Middle and End Regionsmentioning

confidence: 99%

Experimental investigation of EHD grease lubrication in finite line contacts

et al. 2018

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Abstract:The objective of this study was to investigate the grease-lubricated film-forming mechanisms in the finite line contact and to improve the grease-lubricated finite line contact's film-forming capacity. An elastohydrodynamic lubrication (EHL) test rig with two interferometry microscopes, which could simultaneously monitor two different contact locations in the finite line contact, was constructed in order to study the influences of the grease thickener formulation on the film thickness and lubrication condition. By using the relative light intensity method, the thickness maps of the grease-lubricated film were calculated from the interferometer images captured by the two microscopes. The test results revealed that the grease thickener's formulation had remarkable effects on film formation and the perturbation of film thickness. For the lithium-based grease, the film's thickness near the two ends of the roller was prone to severe perturbation caused by the conglomeration of clumps that were hard to shear. For the aluminum-complex-based grease, the fibers tended to accumulate in the middle of the roller rather than at the two ends. The urea-based grease could be easily sheared into smaller particles. In addition to the straight-line profile rollers, the logarithmic profile rollers were tested and found to effectively enhance the axial grease flow, increase the axial shear stress, and thus shear more fibers into particles within the contact area.

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Bearing torque characteristics of lithium soap greases with some synthetic base oils

Cited by 8 publications

References 7 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

Effect of Formulation of Li Greases on Their Flow and Ball Bearing Torque

Experimental investigation of EHD grease lubrication in finite line contacts

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