scholarly journals Origin of the tribofilm from MoS2 nanoparticle oil additives: Dependence of oil film thickness on particle aggregation in rolling point contact

Friction ◽  
2020 ◽  
Author(s):  
Hongxing Wu ◽  
Liping Wang ◽  
Guangneng Dong
Keyword(s):  
Film Thickness ◽  
Contact Area ◽  
Point Contact ◽  
Particle Aggregation ◽  
Engine Oil ◽  
Lubrication Mechanism ◽  
Base Oil ◽  
Thickness Increase ◽  
Oil Film ◽  
Film Thickness Increase

Abstract The lubrication effectiveness of MoS2 nanoparticles as an oil additive remains unclear, restricting its application in industry to reduce friction. The goal of this work was to explore the lubrication mechanism of MoS2 nanoparticles as an oil additive. In this study, the oil film thickness behaviors of MoS2 nanoparticles in poly-alpha olefin (PAO4) base oil, PAO4 with 3 wt% dispersant (polyisobutyleneamine succinimide, PIBS), and 0W20 engine oil were investigated using an elastohydrodynamic lubrication (EHL) testing machine. Following the EHL tests, the flow patterns around the contact area and the tribofilm covering rate on contact area were studied using optical microscopy to understand the lubrication mechanism. The results indicate that both the dispersant and nanoparticle aggregation significantly affected the oil film thickness. The expected oil film thickness increase in the case of 0.1 wt% MoS2 in PAO4 base oil was obtained, with an increase from 30 to 60 nm over 15 min at a velocity of 50 mm/s. Flow pattern analysis revealed the formation of particle aggregation on the rolling path when lubricated with 0.1 wt% MoS2, which is associated with a tribofilm coverage rate of 41.5% on the contact area. However, an oil film thickness increase and particle aggregation were not observed during the tests with 0.1 wt% MoS2 blended with 3 wt% PIBS as the dispersant in PAO4 base oil, and for 0.75 wt% MoS2 in 0W20 engine oil. The results suggest that nanoparticles responsible for tribofilm formation originated from aggregates, but not the well-dispersed nanoparticles in point contact. This understanding should aid the advancement of novel lubricant additive design.

Oil Film Thickness and Rolling Friction in Elastohydrodynamic Point Contact

1971 ◽  
Vol 93 (3) ◽  
pp. 371-379 ◽  
Author(s):  
R. Gohar
Keyword(s):  
Film Thickness ◽  
Tungsten Carbide ◽  
Material Properties ◽  
High Pressures ◽  
Glass Plate ◽  
Point Contact ◽  
Rolling Friction ◽  
Significant Alteration ◽  
Oil Film ◽  
Rolling Ball

The effect of material properties upon the film thickness in elastohydrodynamic point contact is demonstrated with a rolling ball and plate machine. A 220 fold range of Young’s modulus is employed and a maximum Hertzian pressure of 5 × 105 lb f/in2 is reached. The oil film, which is measured by interferometry, shows no significant alteration at such high pressures, and is also fairly insensitive to the choice of bounding materials. Using a technique similar to that employed by Crook, the rolling friction between a tungsten carbide and a glass plate is found and compared with theory. The effect of spin is investigated and found to be slight.

Theoretical and experimental studies of the oil film in lubricated point contact

1966 ◽  
Vol 291 (1427) ◽  
pp. 520-536 ◽  
Keyword(s):  
Surface Layer ◽  
Film Thickness ◽  
Strong Evidence ◽  
Experimental Studies ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Point Contacts ◽  
Previous Theory ◽  
Oil Film

A technique using Newton’s rings for mapping the oil film of lubricated point contacts is described. A theoretical value for the film thickness of such contacts in elastohydrodynamic lubrication is derived. The experimental results give the exit constriction predicted by previous theory but never shown in detail. The comparison of theoretical and experimental oil film thicknesses, which is satisfactorily accurate, gives strong evidence for a viscous surface layer some 1000Å thick. This film agrees with the known ‘lubricating power’ of the various oils tested.

PTFE and MoS2 Additives for Mineral Oil Film Formation in EHL Point Contacts

2016 ◽  
Author(s):  
Glenn Kwabena Gyimah ◽  
Zhongning Guo ◽  
Ping Huang ◽  
Shuzhen Jiang ◽  
Gary C. Barber
Keyword(s):  
Film Thickness ◽  
Viscosity Index ◽  
Point Contact ◽  
Rolling Speed ◽  
Optical Interferometry ◽  
Lubricant Film ◽  
Steel Ball ◽  
Engine Oil ◽  
Lubricant Film Thickness ◽  
Viscosity Index Improvers

Lubricant film-forming viscosity index improvers blended with commercial engine oil have been developed and studied by using optical interferometry. The influence of the viscosity index improvers (PTFE and MoS2) mixed with oil were experimentally studied and compared with engine oil without the index improvers as the baseline. The effect of the viscosity index improvers on lubricant film thickness, contact pressure and rolling speed for the case of a steel ball loaded on a flat glass surface in point contact condition was investigated. An optical interferometry technique which utilized a monochromatic two-beam interferometry light source, a microscope and a high-speed video recording device was used for the investigation. Hamrock and Dawson calculations for EHL film thickness were also used for comparative analysis. The lubricants used were commercial SAE #30 engine oil and PTFE and MoS2 mixed with commercial SAE #30 engine oil. The oil viscosities ranged from 0.0109 Pa.s to 0.255 Pa.s. The rolling speed and the loads were varied between 0.189 m/s to 0.641 m/s and 1 N to 2.6 N respectively. The lubricant film thickness stability at the point of contact between the steel ball and the glass disc was investigated for both steady and rolling state conditions. The viscosity index improvers were found to have a significant effect on the film thickness behavior under pure rolling point contact conditions.

Experimental Investigation of Oil Accumulation in Second Land of Internal Combustion Engines

2005 ◽  
Vol 127 (1) ◽  
pp. 206-212
Author(s):  
T. Icoz ◽  
Z. Dursunkaya
Keyword(s):  
Film Thickness ◽  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Engine Oil ◽  
Combustion Engines ◽  
Oil Consumption ◽  
Oil Accumulation ◽  
Oil Film ◽  
Piston Cylinder ◽  
Total Oil

Blowback of engine oil suspended in combustion gases, when the gas flows from the piston second land back into the combustion chamber, is believed to contribute to oil consumption and hydrocarbon emissions in internal combustion engines. Oil accumulation in the region between top and second compression rings is a factor that influences this phenomenon. The effects of individual parameters, such as oil film thickness and viscosity, however, have still not been understood. The present study was aimed at constructing an experimental setup to study the effect of oil film thickness on oil accumulation in the second land of internal combustion engines. Due to the inherent difficulties of experimentation on production engines, a modeled piston-cylinder assembly was constructed. Total oil accumulation in the modeled second land after a single piston stroke was measured and compared to oil consumption in operating engines.

Development of a Laser Fluorescence Technique For Measuring Piston Ring Oil Film Thickness

1980 ◽  
Vol 102 (2) ◽  
pp. 165-170 ◽  
Author(s):  
L. L. Ting
Keyword(s):  
Light Intensity ◽  
Film Thickness ◽  
Piston Ring ◽  
Laser Fluorescence ◽  
Engine Oil ◽  
Fluorescent Light ◽  
Fluorescence Technique ◽  
Thickness Change ◽  
Oil Film ◽  
Cylinder Sleeve

A single cylinder engine equipped with a transparent cylinder sleeve has been used to develop a technique to make visual investigations of piston ring lubrication behavior and engine oil loss mechanism. This paper describes this apparatus and the development of a laser excited oil fluorescence technique for measuring the oil film thickness change between the piston rings and the transparent cylinder sleeve wall. The amount of oil accumulated in the piston-cylinder clearance spaces above and below the ring pack, and those in the inter-ring spaces, can also be observed. Preliminary results showing oil fluorescence light intensity traces indicate that this technique works very well. Quantitative oil film thickness data should be readily obtainable from these traces once the fluorescent light intensity is calibrated.

A Study on Measurement of Conformability of the Piston Oil Ring on the Cylinder Bore Under Engine Operating Condition by LIF Method Using Optical Fiber

2013 ◽  
Author(s):  
Akemi Ito ◽  
Kazuya Mochiduki ◽  
Koji Kikuhara ◽  
Masatsugu Inui ◽  
Hirotaka Akamatsu
Keyword(s):  
Optical Fiber ◽  
Film Thickness ◽  
Engine Oil ◽  
Sliding Surface ◽  
Oil Consumption ◽  
Ring Groove ◽  
Operating Condition ◽  
Oil Film ◽  
Engine Operating Condition ◽  
Cylinder Bore

Engine oil consumption must be reduced for reducing exhaust gas emissions. It is well known that a cylinder bore shape under engine operating condition affects oil consumption. This study aimed clarifying the conformability of an oil ring against the distorted cylinder bore. Oil film thickness at the sliding surface of oil ring upper and lower rails was successfully measured by LIF method using optical fiber, which was embedded in the oil ring. The piston motion was also measured and compared with measured oil film thickness. It was found that the piston tilting motion affected oil film thickness hence its conformability. It was also found that thicker oil film was found at the following rail than that at former rail, and it was suggested that oil was supplied to the following rail from not only the sliding surface of the former ring but also somewhere, for example, the oil ring groove.

The Shear-Thinning Elastohydrodynamic Film Thickness of a Two-Component Mixture

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Yuchuan Liu ◽  
Q. Jane Wang ◽  
Ivan Krupka ◽  
Martin Hartl ◽  
Scott Bair
Keyword(s):  
Film Thickness ◽  
Ambient Pressure ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Component Mixture ◽  
Base Oil ◽  
Viscosity Models ◽  
Viscosity Behavior ◽  
Pure Rolling

Lubricant base oils are often blends of different molecular weight cuts to arrive at a specified ambient pressure viscosity and, to improve the temperature-viscosity behavior or to simply increase the viscosity, viscosity-modifying polymer additives are often added to the base oil. This paper investigates the effect of mixture rheology on elastohydrodynamic lubrication (EHL) film thickness using EHL contact measurements and a full numerical analysis for three synthetic lubricants including two single-component lubricants PAO650 and PAO100 and a mixture of these. The pressure and shear dependences of the viscosity of these lubricants were measured with high-pressure viscometers; viscosities were not adjusted to fit experiment. The point contact film thicknesses for these lubricants in pure rolling were measured using a thin-film colorimetric interferometry apparatus. Numerical simulations based on the measured rheology show very good agreement with the measurements of film thickness while the Newtonian prediction is up to twice the measurement. These results validate the use of realistic shear-thinning and pressure-viscosity models, which originate from viscosity measurements. It is conceivable that simulation may provide a means to “engineer” lubricants with the optimum balance of film thickness and friction through intelligent mixing of components.

Oil Film Thickness and Pressure Distribution in Elastohydrodynamic Point Contacts

1982 ◽  
Vol 24 (4) ◽  
pp. 173-182 ◽  
Author(s):  
A. Mostofi ◽  
R. Gohar
Keyword(s):  
Contact Problem ◽  
Film Thickness ◽  
Numerical Solutions ◽  
Point Contact ◽  
Point Contacts ◽  
Rolling Velocity ◽  
Oil Film ◽  
Static Contact ◽  
Theoretical Predictions ◽  
Interferometry Method

In this paper, a general numerical solution to the elastohydrodynamic point contact problem is presented for moderate loads and material parameters. Isobars, contours and regression formulae describe how pressure and oil film thickness vary with geometry, material properties, load, and squeeze velocity, when the rolling velocity vector is at various angles to the static contact ellipse long axis. In addition, the EHL behaviour under spin is examined. The theoretical predictions of film thickness compare favourably with other numerical solutions to the point contact problem, as well as with experimental results which use the optical interferometry method to find film thickness and

Sign in / Sign up

Export Citation Format

Share Document