Development of a Tribotester for Investigation of Ferrofluids Lubrication Performance on the Thrust Pad Bearing

Under steady-state pure rolling conditions with low speed, the thickener fiber agglomerations can be maintained for a long time, generating a beneficial thicker film thickness. However, in industrial applications, motions with sliding or transient effects are very common for gears, rolling-element bearings or even chain drives, evaluation of the grease performance under such conditions is vital for determining the lubrication mechanism and designing new greases. In this project, optical interferometry experiments were carried out on a ball-disk test rig to study the disintegration time of the grease thickener agglomerations with the increase of the slide-to-roll ratio under steady-state and reciprocation motions. Under steady-state conditions, the thickener fiber agglomeration can exist for a while and the time becomes shorter with the increase of the slide-to-roll ratio above the critical speed. Below the critical speed, the thickener fiber can exist in the contact in the form of a quite thick film for a very long time under pure rolling conditions but that time is decreased with the increase of the slide-to-roll ratio. The introduction of the transient effect can further reduce the existence time of the thickener.

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Impact of chosen force fields and applied load on thin film lubrication

Friction ◽

10.1007/s40544-020-0464-2 ◽

2021 ◽

Author(s):

Thi D. Ta ◽

Hien D. Ta ◽

Kiet A. Tieu ◽

Bach H. Tran

Keyword(s):

Thin Film ◽

Shear Stress ◽

Surface Structure ◽

Rheological Properties ◽

Surface Potential ◽

Applied Load ◽

Velocity Slip ◽

Thin Film Lubrication ◽

Lubrication Performance ◽

Film Lubrication

AbstractThe rapid development of molecular dynamics (MD) simulations, as well as classical and reactive atomic potentials, has enabled tribologists to gain new insights into lubrication performance at the fundamental level. However, the impact of adopted potentials on the rheological properties and tribological performance of hydrocarbons has not been researched adequately. This extensive study analyzed the effects of surface structure, applied load, and force field (FF) on the thin film lubrication of hexadecane. The lubricant film became more solid-like as the applied load increased. In particular, with increasing applied load, there was an increase in the velocity slip, shear viscosity, and friction. The degree of ordering structure also changed with the applied load but rather insignificantly. It was also significantly dependent on the surface structure. The chosen FFs significantly influenced the lubrication performance, rheological properties, and molecular structure. The adaptive intermolecular reactive empirical bond order (AIREBO) potential resulted in more significant liquid-like behaviors, and the smallest velocity slip, degree of ordering structure, and shear stress were compared using the optimized potential for liquid simulations of united atoms (OPLS-UAs), condensed-phase optimized molecular potential for atomic simulation studies (COMPASS), and ReaxFF. Generally, classical potentials, such as OPLS-UA and COMPASS, exhibit more solid-like behavior than reactive potentials do. Furthermore, owing to the solid-like behavior, the lubricant temperatures obtained from OPLS-UA and COMPASS were much lower than those obtained from AIREBO and ReaxFF. The increase in shear stress, as well as the decrease in velocity slip with an increase in the surface potential parameter ζ, remained conserved for all chosen FFs, thus indicating that the proposed surface potential parameter ζ for the COMPASS FF can be verified for a wide range of atomic models.

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Constructing a biomimetic robust bi-layered hydrophilic lubrication coating on surface of silicone elastomer

Friction ◽

10.1007/s40544-021-0513-5 ◽

2021 ◽

Author(s):

Luyao Gao ◽

Xiaoduo Zhao ◽

Shuanhong Ma ◽

Zhengfeng Ma ◽

Meirong Cai ◽

...

Keyword(s):

Bearing Capacity ◽

Composite Layer ◽

High Load ◽

Silicone Elastomer ◽

Aqueous Lubrication ◽

Low Friction ◽

Load Bearing Capacity ◽

Load Bearing ◽

Lubrication Performance ◽

Wide Range

AbstractSilicone elastomers-based materials have been extensively involved in the field of biomedical devices, while their use is extremely restricted due to the poor surface lubricity and inherent hydrophobicity. This paper describes a novel strategy for generating a robust layered soft matter lubrication coating on the surface of the polydimethylsiloxane (PDMS) silicone elastomer, by entangling thick polyzwitterionic polyelectrolyte brush of poly (sulfobetaine methacrylate) (PSBMA) into the sub-surface of the initiator-embedded stiff hydrogel coating layer of P(AAm-co-AA-co-HEMA-Br)/Fe, to achieve a unified low friction and high load-bearing properties. Meanwhile, the stiff hydrogel layer with controllable thickness is covalently anchored on the surface of PDMS by adding iron powder to provide catalytic sites through surface catalytically initiated radical polymerization (SCIRP) method and provides high load-bearing capacity, while the topmost brush/hydrogel composite layer is highly effective for aqueous lubrication. Their synergy effects are capable of attaining low friction coefficient (COFs) under wide range of loaded condition in water environment with steel ball as sliding pair. Furthermore, the influence of mechanical modulus of the stiff hydrogel layer on the lubrication performance of layered coating is investigated, for which the COF is the lowest only when the modulus of the stiff hydrogel layer well matches the PDMS substrate. Surprisingly, the COF of the modified PDMS could remain low friction (COF < 0.05) stably after encountering 50,000 sliding cycles under 10 N load. Finally, the surface wear characterizations prove the robustness of the layered lubricating coating. This work provides a new route for engineering lubricious silicon elastomer with low friction, high load-bearing capacity, and considerable durability.

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Plasto ‐elastohydrodynamic lubrication performance of greased ellipsoid contact

Lubrication Science ◽

10.1002/ls.1536 ◽

2021 ◽

Author(s):

Yong Zheng ◽

Changqing Wang ◽

Chao Pu ◽

Jiayu Gong ◽

Fanming Meng

Keyword(s):

Elastohydrodynamic Lubrication ◽

Lubrication Performance

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Lubrication Performance Distribution of Large Aspect Ratio Water-Lubricated bearings Considering Deformation and Shaft Bending

Tribology Transactions ◽

10.1080/10402004.2021.1913538 ◽

2021 ◽

pp. 1-15

Author(s):

Wu Ouyang ◽

Qichao Cheng ◽

Yong Jin ◽

Qilin Liu ◽

Bin Wang ◽

...

Keyword(s):

Aspect Ratio ◽

Large Aspect Ratio ◽

Lubrication Performance ◽

Performance Distribution

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On the Fictitious Grease Lubrication Performance in a Four-Ball Tester

Lubricants ◽

10.3390/lubricants9030033 ◽

2021 ◽

Vol 9 (3) ◽

pp. 33

Author(s):

Sravan K. Joysula ◽

Anshuman Dube ◽

Debdutt Patro ◽

Deepak Halenahally Veeregowda

Keyword(s):

Critical Factor ◽

Maximum Load ◽

Test Method ◽

Extreme Pressure ◽

Motor Speed ◽

Low Friction ◽

Grease Lubrication ◽

Additive Package ◽

Variable Frequency Drive ◽

Lubrication Performance

The extreme pressure (EP) behavior of grease is related to its additives that can prevent seizure. However, in this study following ASTM D2596 four-ball test method, the EP behavior of greases was modified without any changes to its additive package. A four-ball tester with position encoders and variable frequency drive system was used to control the speed ramp up time or delay in motor speed to demonstrate higher grease weld load and lower grease friction that were fictitious. A tenth of a second delay in speed ramp up time had showed an increase in the weld load from 7848 N to 9810 N for grease X and 6082 N to 9810 N for grease Y. Further increase in the speed ramp up time to 0.95 s showed that the greases passed the maximum load of 9810 N that was possible in the four-ball tester without seizure. The mechanism can be related to the delay in rise of local temperature to reach the melting point of steel required for full seizure or welding, that was theoretically attributed to an increase in heat loss as the speed ramp-up time was increased. Furthermore, the speed ramp up time increased the corrected load for grease X and Y. This resulted in lower friction for grease X and Y. This fictitious low friction can be attributed to decrease in surface roughness at higher extreme pressure or higher corrected load. This study suggests that speed ramp up time is a critical factor that should be further investigated by ASTM and grease manufacturers, to prevent the use of grease with fictitious EP behavior.

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The Effect of Nanoparticle Functionalization on Lubrication Performance of Nanofluids Dispersing Silica Nanoparticles in an Ionic Liquid

Journal of Tribology ◽

10.1115/1.4035342 ◽

2017 ◽

Vol 139 (4) ◽

Cited By ~ 6

Author(s):

Cengiz Yegin ◽

Wei Lu ◽

Bassem Kheireddin ◽

Ming Zhang ◽

Peng Li ◽

...

Keyword(s):

Silica Nanoparticles ◽

Coefficient Of Friction ◽

Shear Thinning ◽

Antiwear Additives ◽

Functionalized Silica ◽

Low Concentrations ◽

Lubrication Performance ◽

The Coefficient Of Friction ◽

High Concentrations ◽

Newtonian Behavior

Recently, ionic liquids (ILs) have received an increasing attention as lubricants owing to their intriguing properties such as tunable viscosity, high thermal stability, low emissions, nonflammability, and corrosion resistance. In this work, we investigate how the incorporation of octadecyltrichlorosilane (OTS) functionalized silica nanoparticles (NPs) in 1-butyl-3-methylimidazolium (trifluoromethysulfony)imide influences the tribological properties and rheological properties of IL under boundary lubrication and elastohydrodynamic conditions, respectively. It was found that the coefficient of friction was depended on the concentration of NPs in IL with a concave upward functional trend with a minimum at 0.05 wt.% for bare silica NPs and at 0.10 wt.% for OTS-functionalized silica NPs. For steel–steel sliding contact, the presence of functionalized NPs in IL at the optimum concentration decreased the coefficient of friction by 37% compared to IL and 17% compared to IL with bare silica NPs. While IL with bare NPs demonstrated a shear thinning behavior for all concentrations, IL with functionalized NPs showed a Newtonian behavior at low concentrations and shear thinning behavior at high concentrations. Overall, this study provides new insights into the antifriction and antiwear additives for lubrication systems involving ILs.

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Effect of recess depth on lubrication performance of annular recess hydrostatic thrust bearing by constant rate flow

Industrial Lubrication and Tribology ◽

10.1108/ilt-03-2017-0066 ◽

2018 ◽

Vol 70 (1) ◽

pp. 68-75 ◽

Cited By ~ 4

Author(s):

Jun-peng Shao ◽

Guang-dong Liu ◽

Xiao-dong Yu ◽

Yan-qin Zhang ◽

Xiu-li Meng ◽

...

Keyword(s):

Thrust Bearing ◽

Simulation Method ◽

Content Type ◽

Oil Film ◽

Constant Rate ◽

Lubrication Performance ◽

Optimal Value ◽

Improved Performance ◽

Lubrication Characteristics ◽

Volume Method

Purpose The purpose of this paper is to describe a simulation and experimental research concerning the effect of recess depth on the lubrication performance of a hydrostatic thrust bearing by constant rate flow. Design/methodology/approach The computational fluid dynamics and finite volume method have been used to compute the lubrication characteristics of an annular recess hydrostatic thrust bearing with different recess depths. The performances are oil recess pressure, oil recess temperature and oil film velocity. The recess depth has been optimized. A test rig is established for testing the pressure field of the structure of hydrostatic thrust bearing after recess depth optimization, and experimental results show that experimental data are basically identical with the simulation results, which demonstrates the validity of the proposed numerical simulation method. Findings The results demonstrate that the oil film temperature decreases and the oil film pressure first increases and then decreases with an increase in the recess depth, but oil film velocity is constant. To sum up comprehensive lubrication performance, the recess depth of 3.5 mm is its optimal value for the annular recess hydrostatic thrust bearing. Originality/value The computed results indicate that to get an improved performance from a constant flow hydrostatic thrust bearing, a proper selection of the recess depth is essential.

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Analysis of misaligned journal bearing lubrication performance considering the effect of lubricant couple stress and shear thinning

Journal of Mechanics ◽

10.1093/jom/ufaa018 ◽

2021 ◽

Vol 37 ◽

pp. 282-290

Author(s):

Junchao Zhu ◽

Haiyu Qian ◽

Huabing Wen ◽

Liangyan Zheng ◽

Hanhua Zhu

Keyword(s):

Film Thickness ◽

Couple Stress ◽

Journal Bearing ◽

Shear Thinning ◽

Inlet Temperature ◽

Stress Effect ◽

Misalignment Angle ◽

Oil Film ◽

Stress Coefficient ◽

Lubrication Performance

ABSTRACT This paper investigates journal bearings, and builds a lubrication model taking into account misalignment, the lubricant couple stress effect and shear thinning. In order to explore the sensitivity of couple stress fluid lubrication performance to oil film thickness, we introduce the critical oil film thickness coefficient. The results show that the sensitivity increases with the increase of the couple stress coefficient, and it is highest in the area of minimum oil film thickness. Compared with a parallel journal, increases in the misalignment angle strengthen the effect of couple stress. Shear thinning also plays an important role in bearing lubrication performance. For a low oil inlet temperature, the effect of shear thinning increases with the increase of the couple stress parameter. For a high oil inlet temperature, the influence is negligible. An increase in the misalignment angle will not further enhance the effect of shear thinning.

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