Rheological and Film Forming Behavior of the Developed Nanocomposite Greases Under Elastohydrodynamics Lubrication Regime

Performance of grease lubricated point contact under elastohydrodynamics lubrication (EHL) regime is critical in many engineering applications. The present work deals with the evaluation of rheological, film forming characteristics and elastic recovery of newly developed nanocomposite greases. The nanocomposite greases are formulated by dispersing different nano-additives to bare grease (BG). The nano-additives include reduced graphene oxide (rGO) nanosheets, CaCO3 and α-Al2O3 nanoparticles. The microstructure evaluation of the nano-additives and different greases is done using high-resolution transmission electron microscopy (HRTEM). Estimation of the rheological parameters (storage and loss moduli) is done using rotational rheometer. The film forming behavior is recorded using elastohydrodynamic (EHD) rig for range of speed at different temperatures and constant load. The results indicate that change in microstructure due to nano-additive incorporation improves the responses of different greases. Based on rheological response, CaCO3 doped grease seems better but rGO doped grease is able to bear high shear stresses. Further, based on film forming characteristics and reflow or recovery behavior, rGO doped grease is better. The rGO-based grease registers approximately 90% elastic recovery followed by 75% for CaCO3-based grease, 65% for BG and 10% for α-Al2O3-doped grease.

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TRIBOLOGICAL PROPERTIES OF A NEW KIND OF FRICTION-PROMOTING GREASE IN SLIDING POINT CONTACTS

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-2015-0016 ◽

2015 ◽

Vol 39 (2) ◽

pp. 221-237

Author(s):

Wan Ma ◽

Zhen C. Zhu ◽

Yu X. Peng ◽

Guo A. Chen

Keyword(s):

Tribological Properties ◽

Point Contact ◽

Constant Load ◽

Normal Operation ◽

Point Contacts ◽

Contact Conditions ◽

Rotating Speed ◽

Operation Conditions ◽

Film Forming ◽

The Coefficient Of Friction

In this paper, the tribological properties and the film-forming properties of the friction-promoting grease (FPG) A under point-contact conditions were investigated by conducting respectively four-ball experiments and FPG A-lubricated ball-and-disc contact experiments. The experimental results indicate that the coefficient of friction (COF) decreases with an increase in the rotating speed at a constant load; FPG A has a good film-forming ability and a good adhesion property; the application of FPG A under hoist’s normal operation conditions could greatly protect the contact surfaces from wear and supply a sufficient COF.

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Film-Forming Characteristics of Grease in Point Contact Under Swaying Motions

Tribology Letters ◽

10.1007/s11249-009-9455-1 ◽

2009 ◽

Vol 35 (2) ◽

pp. 149-149

Author(s):

Gang Li ◽

Chenhui Zhang ◽

Jianbin Luo ◽

Shuhai Liu ◽

Guoxin Xie ◽

...

Keyword(s):

Point Contact ◽

Film Forming ◽

Forming Characteristics

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Development of Nanocomposite Grease: Microstructure, Flow, and Tribological Studies

Journal of Tribology ◽

10.1115/1.4035775 ◽

2017 ◽

Vol 139 (5) ◽

Cited By ~ 12

Author(s):

Jayant Singh ◽

Deepak Kumar ◽

Naresh Tandon

Keyword(s):

Friction Mechanisms ◽

Low Noise ◽

Al2o3 Nanoparticles ◽

Flow Properties ◽

Transmission Electron ◽

Reduced Graphene ◽

Nano Additives ◽

The Difference ◽

Α Al2o3 ◽

Alpha Alumina

Greases are widely used for variety of applications at extreme pressures, temperatures, and speeds with obligation of high bearing and shaft life with low noise. The present study deals with the development of nanocomposite greases and records their flow and frictional characteristics. The commercial grease is modified, by dispersing nanoparticles, to get the nanocomposite greases. Reduced graphene oxide (rGO), calcium carbonate (CaCO3), and alpha-alumina (α-Al2O3) are used as nano-additives. The microstructure of newly developed greases is examined using high-resolution transmission electron microscopy (HRTEM), and the presence of different chemical functional groups is explored using Fourier transform infrared spectroscopy (FTIR). Further, the new greases are investigated for rheological, consistency, and tribological behavior using Visco Tester, penetrometer, and elastohydrodynamic (EHD) rig, respectively. The flow properties reveal the shear-thinning, yielding, and thixotropic nature of lubricating greases. The study shows that there is an optimality in concentration of different nano-additives above which grease's flow and tribological performance degrades. Up to 35%, 27%, and 10% reduction in coefficient of friction is recorded for optimum concentration of rGO nanosheets, CaCO3, and α-Al2O3 nanoparticles, respectively. The difference in the performance of nanocomposite greases can be attributed to the appearance of different friction mechanisms for different nano-additives.

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Tribo-Dynamics of Nanocomposite Grease Lubricated Point Contact Under Elastohydrodynamics Lubrication Regime

Journal of Tribology ◽

10.1115/1.4041590 ◽

2018 ◽

Vol 141 (3) ◽

Author(s):

Jayant Singh ◽

Deepak Kumar ◽

Naresh Tandon

Keyword(s):

Film Thickness ◽

Film Formation ◽

Mechanical Vibration ◽

Point Contact ◽

Vibrational Response ◽

Transmission Electron ◽

Reduced Graphene ◽

Nano Additives ◽

Α Al2o3 ◽

Tribological Contact

Friction is usually induced when the contacts are in relative motion, leading to mechanical vibration and consequently heat generation. The reduction of these undesirable parameters is possible by the application of greases, which intends to increase the service life of the bearings. The present work incorporates the frictional and vibration behaviors of concentrated point contact lubricated with bare and nanocomposite greases. The nanocomposite greases were formulated by dispersing different categories of nano-additives like reduced graphene oxide (rGO), calcium carbonate (CaCO3), and alumina (α-Al2O3) in bare grease (BG). The formulated nanocomposite greases are tested for film formation, frictional and vibrational response under a limited supply of greases. The use of transparent glass disk better analyses the profile of film thickness to understand the lubrication mechanism of the point contact. The microstructure of nano-additives and the formulated nanocomposite greases were characterized using high-resolution transmission electron microscopy (HRTEM). The presence of different functional groups in nano-additives and the formulated nanocomposite greases were characterized using Raman spectroscopy. The tribological contact operates under 3% and 30% slide-roll-ratio (SRR) for varying rolling speed (0.001–1 m/s) at a load of 30 N (Hertzian pressure, pH = 0.9 GPa). Film thickness, friction and vibration behavior were recorded to focus the tribo-performance, degree of starvation and dynamics of the tribological contact with slip varying from 3% to 30% SRR. The vibration level was refined to 32% with the addition of rGO nanosheets in BG. The incompatibility of α-Al2O3 with the grease structure results in disruption of tribo-dynamics behavior of the point contact.

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Film-forming Characteristics of Grease in Point Contact under Swaying Motions

Tribology Letters ◽

10.1007/s11249-009-9433-7 ◽

2009 ◽

Vol 35 (1) ◽

pp. 57-65 ◽

Cited By ~ 10

Author(s):

Gang Li ◽

Chenhui Zhang ◽

Jianbin Luo ◽

Shuhai Liu ◽

Guoxin Xie ◽

...

Keyword(s):

Point Contact ◽

Film Forming ◽

Forming Characteristics

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Lubrication Properties of Aqueous Solutions with Polyethoxylated Ether (PEOE) Added

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.239-242.1359 ◽

2011 ◽

Vol 239-242 ◽

pp. 1359-1363

Author(s):

Chao Hui Zhang ◽

Si Si Liu ◽

Yue Tao Sun ◽

Jun Ming Liu

Keyword(s):

Aqueous Solution ◽

Aqueous Solutions ◽

Metal Working ◽

Functional Additives ◽

Film Forming ◽

Minor Influence ◽

Forming Characteristics ◽

Aqueous Surfactants ◽

A Minor ◽

Lubrication Properties

Aqueous solutions have found broad usages as lubricants, in conjunction with other possible utilizations, such as in metal working and other industries. Due to the inferior lubricity, functional additives are needed to improve their tribological performances among which aqueous surfactants are exclusively included. The film forming property of aqueous solution with polyethoxylated ether added (PEOE) is measured, taking consideration of the influences of the temperature and the concentration. The addition of PEOEs into aqueous solutions will largely increase the film forming capacity. But the concentration has only a minor influence on the lubrication property of the aqueous solutions with PEOEs. The cloud point will strongly alter the film forming characteristics.

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Effects of polymers concentration on EHL film-forming in point contacts

Industrial Lubrication and Tribology ◽

10.1108/ilt-07-2020-0263 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Liangwei Qiu ◽

Xiaoyang Chen ◽

Fakai Dong

Keyword(s):

Film Thickness ◽

Peer Review ◽

Point Contact ◽

High Concentration ◽

Content Type ◽

Base Oils ◽

Low Viscosity ◽

Lubricant Oil ◽

Pure Rolling ◽

Film Forming

Purpose This paper aims to experimentally investigate the film-forming capability of base oils containing poly-methacrylate (PMA) and poly-isobutene (PIB), in a point contact under pure rolling. Design/methodology/approach By using the relative light intensity method, the film thickness is calculated from the interferometer images which are captured by multiple-contact optical elastohydrodynamic lubricated test rig. Findings The test results reveal that polymers, both PMA and PIB, have a significant contribution to the film-forming capability of base oils and the film thickness increases with concentration. The forming-film capabilities for PMA and PIB in base oils are similar at low concentration, while PIB gives a higher film thickness than PMA at high concentration. Shear-thinning phenomenon are observed in all polymer-based oils. Originality/value The polymer usually as an additive is added into the low viscosity base oils to improve the properties of lubricant oil. This paper reports the lubricated properties of PMA and PIB with different concentrations in base oils and to evaluate their functional mechanism in a point contact. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0263/

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