Effects of Soap Fiber Structure on Boundary Lubrication of Lithium Soap Greases

Yokouchi, Atsushi; Hokao, Michita; Sugimura, Joichi

doi:10.2474/trol.6.219

Cited by 8 publications

(10 citation statements)

References 7 publications

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“…Grease-A can form thicker film, because film thickness of G-I base oil is thicker than that of G-IV base oil. In addition, Li-complex thickener raises film thickness more, since the thin and long fiber structure can enter the contact area as Yokouchi et al reported [10]. The thickener behavior also increases grease abundance in the inlet of EHL contact area.…”

Section: Discussionmentioning

confidence: 81%

“…In contrast, the fiber structure of Grease-B exhibited thicker feature so that the thickener accumulated in the inlet region of contact area, which must have led to oil starvation. Yokouchi et al reported similar ideas that the grease with longer soap fibers had a higher capability to be entrained into the conjunction, although it was referred in boundary lubrication [10]. Based on these factors, lubrication mechanisms in this study are proposed as shown in Figs.…”

Section: Discussionmentioning

confidence: 85%

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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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Section: Discussionmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 85%

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

et al. 2016

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“…Kimura et al [14] controlled the thickness of the thickener fibers through the optimization of the heating-cooling conditions in its manufacturing process. Yokouchi et al [15] and Oikawa et al [16] studied the effect of fiber length, and showed that the grease with longer soap fibers was more easily entrained into the contact and showed favorable lubrication with low friction coefficient. All these works suggest that the role of thickener in grease lubrication should not be neglected.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Starvation and Flow Behavior in Grease-Lubricated EHD Contact

2015

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This paper describes an experimental study of starvation and flow behavior in grease-lubricated elastohydrodynamic contact. Rolling tests were conducted with four grease samples with different thickeners and base oils in a conventional ball-on-disk test rig. The EHL central film thickness was determined with SLIM, the Spacer Layer Imaging Method, and grease flow around the conjunction and the flow pattern on the track of the disk specimen were observed with CCD cameras. The grease track included some thickener deposited on the track and a corrugated fingerlike flow pattern outward from the center of the track. It was found that the flow pattern varied with grease type and test conditions, and that the average interval between fingers decreased with the entrainment speed. At higher speeds, inlet starvation occurred and the finger pattern was deformed and gradually ruptured. The speed of the finger-loss was higher than the speed at which starvation started. It was also found that the starvation speed was greater with greases having lower apparent viscosity at lower shear rate and higher apparent viscosity at high shear rate. This implied that the replenishment and entrainment of the greases depended on the viscosity characteristics of the greases.

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“…The ratio may depend on physical property of the grease, the parameter of the bearing and an operating condition. The yield stress Y represents the physical property of the grease, and the coefficient 9.6 of equation (4) corresponds to the parameter of the bearing and an operating condition. A physical meaning of equation (4) may be as follows; the yield stress Y represents the ability to channel in the allowed space and the coefficient 9.6 represents the possible space for grease to channel between balls and races.…”

Section: Bearing Torque Characteristicsmentioning

confidence: 99%

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

Oikawa

Inami

Hokao

et al. 2012

Proceedings of the Institution of Mechanical Engineers, Part J:

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This article describes the influence of rheological properties on the bearing torque characteristics of the lithium soap greases with five types of base oils. The greases used had different yield stress depending on the base oils even with the same thickener concentration. Measurement of bearing torque was conducted for a deep-groove radial ball bearing by using a bearing test apparatus. The bearings filled with greases initially exhibited high torque but showed gradual decrease in the torque with prolonged rotation, where the greases with higher yield stress showed larger normalized torque decrease. Observation of bearing after the rotation revealed a tendency that the greases with larger normalized torque decrease had been pushed aside in the raceway by channeling. This implied that the greases with higher yield stress tended to show channeling. On the other hand, the greases with lower yield stress circulated within the bearing by churning and showed smaller normalized torque decrease. These behaviors were explained in terms of the yield stress of the greases and the shear stress to entrain the greases into the contacts. Observation of grease structure was made with atomic force microscopy showed that the greases whose thickener network structure was distributed more densely had higher yield stress.

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Effects of Soap Fiber Structure on Boundary Lubrication of Lithium Soap Greases

Cited by 8 publications

References 7 publications

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

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

Experimental Study of Starvation and Flow Behavior in Grease-Lubricated EHD Contact

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

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