Effects of nano thickener deposited film on the behaviour of starvation and replenishment of lubricating greases

Huang, Lu; Guo, Dan; Liu, Xiang; Xie, Guoxin; Wan, G.T.Y.; Wen, Shizhu

doi:10.1007/s40544-016-0123-9

Cited by 20 publications

(11 citation statements)

References 22 publications

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“…Therefore, a ball-on-disc tribometer was extended by a second ball specimen, which was added in front of the measuring ball to increase the over rolling frequency in a dependent manner However, since the replenishment time is dependent on the lubricant flow, it varies with different lubricants and lubricant properties [21,30,41]. Moreover, some studies [33,41,42] show that the replenishment time does not only depend on the over rolling frequencies, but additionally on operating conditions, such as vibrations or centrifugal forces in radial bearings as well as the wettability of the lubricant on different surfaces, e.g., in the presence of deposited thickener layers on the surfaces. Future work should consider these aspects when investigating the lubricant supply of oil or grease lubricated EHD contacts under starved conditions.…”

Section: Discussionmentioning

confidence: 99%

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Effect of Over Rolling Frequency on the Film Formation in Grease Lubricated EHD Contacts under Starved Conditions

et al. 2019

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The service life of rolling bearings is significantly affected by the lubricating film formation in elastohydrodynamic (EHD) contacts. Grease lubricated EHD contacts show a film thickness decay from a characteristic rotational speed, which is referred to as starvation. Thus, the film thickness of grease lubricated contacts differs from that of oil lubricated contacts. However, the base oil properties under fully flooded conditions are commonly assumed to estimate the operating lifetime of grease lubricated bearings, which are usually not fully flooded. Hence, this assumption results in an overestimation of the film thickness for rotational speeds in the range of starvation, which can lead to uncertainties in the bearing design. At high rotational speeds, i.e., high over rolling frequencies, starvation is likely to occur, due to insufficient lubricant supply by replenishment behind the rolling element. Therefore, the focus of this contribution is to investigate the effect of over rolling frequency, and thus replenishment time, on the lubricating film formation in starved, grease lubricated EHD contacts. The film thickness measurements were performed on a ball-on-disc tribometer, which was extended by adding a second ball specimen in front of the measuring ball. By varying the angular distance between the two contacts, the lubricant displacement can be controlled, such that the effect of replenishment time on the film formation can be determined. These investigations should help to establish an advanced understanding of the mechanisms of grease lubrication, and encourage future work with a focus on developing a method to predict the film formation in grease lubricated EHD contacts.

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Section: Discussionmentioning

confidence: 99%

“…Moreover, it is generally assumed that the film thickness in grease lubricated EHD contacts is a build-up of layers of deposited thickener that forms on the contacting surfaces and bleed oil [6,8,13,15,21,32,33]. A schematic sketch of a grease lubricated contact is shown in Figure 3.…”

Section: Introductionmentioning

confidence: 99%

Effect of Over Rolling Frequency on the Film Formation in Grease Lubricated EHD Contacts under Starved Conditions

et al. 2019

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“…The thickener structure on the contact area is destroyed by the shear stress released by the base oil from the thickener structure [31]. Simply, the thickener acts as an oil reservoir releasing the base oil to the contact area [32]. Meanwhile, the contact area forms a hydrodynamic film with the effect of relative sliding of the friction pairs.…”

Section: Effect Of Thickener Component On Lubrication Processmentioning

confidence: 99%

Improving the lubrication and anti-corrosion performance of polyurea grease via ingredient optimization

Ren

Sun

et al. 2020

Friction

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Thickener formulation plays a significant role in the performance characteristics of grease. The polyurea greases (PUGs) were synthesized using mineral oil (500SN) as the base oil, and by regulating the reaction of diphenylmethane diisocyanate (MDI) and different organic amines. The as-prepared PUGs from the reaction of MDI and cyclohexylamine/p-toluidine exhibit the optimum physicochemical and friction-wear properties, confirming that the regulation of thickener formulation can improve the performance characteristics of grease, including friction reduction, wear, corrosion resistance, and load-carrying capacity. The anticorrosion and lubrication properties of as-prepared PUGs depend on good sealing functions and a boundary lubrication film (synergy of grease-film and tribo-chemical reaction film), as well as their chemical components and structure.

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“…The previous study suggested that the solvency of the base oil strongly impacts the pumpability and rheological properties of grease, and is in a close relation with the thickener [10]. The base oil could bleed from the thickener; then, the grease softens under compression and shearing [11]. The type of base oil, structure of thickener, and their interaction strongly determine the operating conditions (load-bearing ability, running speed) and environment (e.g., high/low temperature, humid, dust) [12].…”

Section: Introductionmentioning

confidence: 99%

Comparative study on corrosion resistance and lubrication function of lithium complex grease and polyurea grease

Ren

Zhang

et al. 2019

Friction

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In this study, lithium complex grease (LCG) and polyurea grease (PUG) were synthesized using mineral oil (500SN) and polyalphaolefin (PAO40) as base oil, adsorbed onto lithium complex soap and polyurea as thickeners, respectively. The effects of grease formulation (thickener and base oil with different amounts (80, 85, and 90 wt%) on the corrosion resistance and lubrication function were investigated in detail. The results have verified that the as-prepared greases have good anti-corrosion ability, ascribed to good salt-spray resistance and sealing function. Furthermore, the increase in the amount of base oil reduces the friction of the contact interface to some extent, whereas the wear resistance of these greases is not consistent with the friction reduction, because the thickener has a significant influence on the tribological property of greases, especially load-carrying capacity. PUG displays better physicochemical performance and lubrication function than LCG under the same conditions, mainly depending on the component/structure of polyurea thickener. The polyurea grease with 90 wt% PAO displays the best wear resistance owing to the synergistic lubrication of grease-film and tribochemical film, composed of Fe 2 O 3 , FeO(OH), and nitrogen oxide.

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Effects of nano thickener deposited film on the behaviour of starvation and replenishment of lubricating greases

Cited by 20 publications

References 22 publications

Effect of Over Rolling Frequency on the Film Formation in Grease Lubricated EHD Contacts under Starved Conditions

Effect of Over Rolling Frequency on the Film Formation in Grease Lubricated EHD Contacts under Starved Conditions

Improving the lubrication and anti-corrosion performance of polyurea grease via ingredient optimization

Comparative study on corrosion resistance and lubrication function of lithium complex grease and polyurea grease

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