The Importance of Variable Speeds under Extreme Pressure Loading in Molybdenum Disulfide Greases Using Four-Ball Wear Tests

Nehme, Gabi

doi:10.1080/10402004.2013.816812

Cited by 18 publications

(26 citation statements)

References 11 publications

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“…Under grease lubrication conditions, the formation of an antifriction film is critical to improve frictional performance. Three film formation mechanisms were presented in the literature: the base oil separates out from grease and comes into the surface, 24,25 the MoS 2 particles also come out of grease matrix and spread uniformly over the surface to generate transfer film, 26,27 or the deposited film formed by the physical deposition of the thickener. 24,28 When subjected to a normal load, grease exhibits a shear-thinning flow behavior with time.…”

Section: Analysis Of Frictional Performancementioning

confidence: 99%

Effect of surface texture on the frictional properties of grease lubricated spherical plain bearings under reciprocating swing conditions

Tang

Liu

2016

Proceedings of the Institution of Mechanical Engineers, Part J:

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Surface texturing is a widely used method to improve the tribological performance of the mechanical systems. To introduce the surface texture into the mechanical components, this study experimentally examined the frictional behaviors of grease lubricated spherical plain bearings under mixed lubrication conditions on an electro-hydraulic servo tribological test rig. The effects of the surface texture parameters and roughness parameters on the frictional properties of bearings were investigated. The results showed that higher dimple depths and lower dimple densities would result in a distinct improvement on the friction coefficients. A maximum reduction of 55% was gained for the textured sample under running conditions compared with the untextured one. In addition, the surface roughness parameters also influence the frictional behaviors. In the high load conditions, the friction coefficient decreases while the Ssk value gets more negative, even though the Sa value is much higher. On the other hand, in the low load conditions, when the value of Ssk varies between −5 and −1, the influence of the value of Sa on the friction coefficient becomes obvious, a higher Sa value results in a higher friction coefficient.

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Section: Analysis Of Frictional Performancementioning

confidence: 99%

Effect of surface texture on the frictional properties of grease lubricated spherical plain bearings under reciprocating swing conditions

Tang

Liu

2016

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…Grease is a semifluid to solid mixture of a fluid lubricant, a thickener, and additives. It performs like mineral or synthetic oil in the lubrication regime but with the aid of thickener such as soap, or organic and inorganic non-soap, its consistency will be enhanced and it will perform better in high-pressure applications [1]. The majority of greases on the market are composed of mineral oil blended with a soap thickener.…”

Section: Introductionmentioning

confidence: 99%

Effects of break in period on the 4-ball wear tests using molybdenum disulphide (MoSշ) as EP additives in lithium based grease

Nehme

El-Merhabi

Ghalambor

2020

Agricultural Engineering

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The lamellar structure of MoS 2 provides very good protecting layer that can be easily sheared under the application of extreme pressures and thus enhance the antiwear performance of the chromium steel bearing aircraft grade E52100. ASTM standard 2266 uses 4-ball testing by keeping the load at 393 Newton wherein the grease is heated to 75ºC and the test is conducted at a rotational speed of 1200 min -1 for 1 hour and the wear scar is measured at the end of the period. While this method is useful under fixed conditions it is not always representative of the fields where variable loads and speeds and different break in periods play a role and could change the results tremendously.The goal of this study was to examine the loads and speeds conditions with and without break in period of 30 second at the start of the test and every 7.5 minutes thereafter. This will help explain their influences on the wear properties of lithium base grease under fixed 2% MoS 2 concentrations. Results indicated that wear was largely dependent on the loading condition during specific break in period at a higher rotational speed. It is believed that MoS 2 greases perform better under moderate loading when break in period is used as was optimized by Design Expert analysis (DOE). MoS 2 is sufficient to improve the wear characteristics at different break in period for different speeds and loads for extreme pressure applications.

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“…Engine oils, which normally contain zinc-based anti-wear and anti-friction additives, often fail under these conditions. Several studies 1–21 have been made on the influence of dispersion of nanomaterials on the tribological properties of lubricant. It has been found from these studies that nanomaterials are promising additives for the reduction of friction, wear, and improvement of extreme pressure properties.…”

Section: Introductionmentioning

confidence: 99%

“…Zhmud and Pasalskiy 18 in their review presented an overview on the use of various classes of nanomaterials. In their study, aluminum-complex grease without any traditional extreme pressure or anti-wear additives is tested with dispersion of inorganic fullerene WS 2 particles.…”

Section: Introductionmentioning

confidence: 99%

Physicochemical properties and tribological performance of motorbike lubricant dispersed with surface-modified WS₂ nanoparticles

Srinivas

Thakur

Jain

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part J:

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This paper investigates the effect of dispersion of surface-modified WS2 nanoparticles on the tribological performance and physicochemical properties of motorbike lubricant. Surface-assisted WS2 nanoparticles were dispersed in motorbike engine oil and an optimum amount of surfactant for best stability of the lubricant suspension was found by investigating the changes in the physicochemical properties of lubricant. The stability analysis using light scattering techniques confirmed the stability of nanoparticles dispersed in lubricant medium and surface-modified WS2 nanoparticles remained stable for 180 days. The physicochemical properties were evaluated as per ASTM standards over a period of two months to check the state of lubricant and observable changes in the properties during this period. The tribological performance of the lubricants was assessed by conducting endurance tests on a 100 cc motor bike. The performance was evaluated by checking the wear of the engine components and fuel consumption. It was found that there were no abnormal changes in the physicochemical properties of lubricant up to a certain surfactant to nanoparticle ratio indicating its utility in automotive engines. However, if the amount of surfactant was increased beyond optimum quantity abnormal changes are seen in the viscosity index, leading to the deterioration of key lubricant properties. Lubricant dispersed with WS2 nanoparticles gave good performance characterized by the reduction in both engine wear and fuel consumption. Worn surfaces of the oil rings after the endurance test were assessed for deposits and it was found that a layer of WS2 deposited on the oil ring surface that reduced friction and wear.

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The Importance of Variable Speeds under Extreme Pressure Loading in Molybdenum Disulfide Greases Using Four-Ball Wear Tests

Cited by 18 publications

References 11 publications

Effect of surface texture on the frictional properties of grease lubricated spherical plain bearings under reciprocating swing conditions

Effect of surface texture on the frictional properties of grease lubricated spherical plain bearings under reciprocating swing conditions

Effects of break in period on the 4-ball wear tests using molybdenum disulphide (MoSշ) as EP additives in lithium based grease

Physicochemical properties and tribological performance of motorbike lubricant dispersed with surface-modified WS₂ nanoparticles

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The Importance of Variable Speeds under Extreme Pressure Loading in Molybdenum Disulfide Greases Using Four-Ball Wear Tests

Cited by 18 publications

References 11 publications

Effect of surface texture on the frictional properties of grease lubricated spherical plain bearings under reciprocating swing conditions

Effect of surface texture on the frictional properties of grease lubricated spherical plain bearings under reciprocating swing conditions

Effects of break in period on the 4-ball wear tests using molybdenum disulphide (MoSշ) as EP additives in lithium based grease

Physicochemical properties and tribological performance of motorbike lubricant dispersed with surface-modified WS2 nanoparticles

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Physicochemical properties and tribological performance of motorbike lubricant dispersed with surface-modified WS₂ nanoparticles