Study of Micro-Morphology Influence on the EHL Analysis of Water-Based Ferrofluid

2013 ◽  
Vol 373-375 ◽  
pp. 417-420
Author(s):  
Xiujiang Shi ◽  
You Qiang Wang
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Local Pressure ◽  
Thickness Change ◽  
Thickness Increase ◽  
Film Thickness Increase ◽  
Water Based ◽  
Pressure Peak ◽  
Micro Morphology ◽  
Morphology Influence

The elastohydrodynamic lubrication (EHL) study of water-based ferrofluid bearing with single sine-shaped peak, rectangular-shaped valley and V-shaped valley was carried out. The influence of the amplitude and the width on the pressure and film thickness was discussed. The results reveal that the pressure and film thickness change apparently with the change of micro-morphology; The amplitudes of the local pressure peak and the film thickness increase with the increase of amplitudes; The widths of the local pressure peak and the film thickness increase with the increase of width.

Influence of Micro-Morphology on Thermal Elatohydrodynamic Lubrication of Water-Lubricated Tenmat Bearing

2015 ◽  
Vol 743 ◽  
pp. 85-90 ◽  
Author(s):  
Ning Dong ◽  
You Qiang Wang ◽  
Qian Liu ◽  
Xing Bao Huang
Keyword(s):  
Numerical Analysis ◽  
Film Thickness ◽  
Partial Pressure ◽  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Single Peak ◽  
Sine Function ◽  
Lubricating Film ◽  
Pressure Peak ◽  
Micro Morphology

The elastohydrodynamic lubrication numerical analysis of water-lubricated tenmat bearing with single sine-type peak, single V-type valley and single rectangular-type valley was carried out by using the Reynolds equation. The results show that, for the bearing with single peak, the partial pressure peak appears and the corresponding film thickness increases rapidly and then decreases; With the increase of the amplitude of the sine function, the partial pressure of the lubricating film is also increased, the partial film thickness is decreased, as the wavelength increases, the pressure and the film thickness of the convex portion widened, the peak remains substantially unchanged. For the bearing with single V-type valley and single rectangular-type valley, the partial pressure are decreased, the partial film thickness are increased; with the amplitude of the roughness function increases, the partial pressure are decreased, on the contrary ,the partial film thickness are increased; with the wavelength increases, the pressure and the film thickness of the convex portion widened.

A thermal EHL investigation on plate-pin hinge pairs in silent chains using a narrow finite line contact

2020 ◽  
Vol 72 (10) ◽  
pp. 1139-1145
Author(s):  
Mingyu Zhang ◽  
Jing Wang ◽  
Jinlei Cui ◽  
Peiran Yang
Keyword(s):  
Film Thickness ◽  
Temperature Rise ◽  
Elastohydrodynamic Lubrication ◽  
Radius Of Curvature ◽  
Line Contact ◽  
Equivalent Radius ◽  
Content Type ◽  
Finite Line Contact ◽  
Pressure Peak ◽  
Finite Line

Purpose The purpose of this paper is to numerically study the variations of oil film pressure, thickness and temperature rise in the contact zone of plate-pin pair in silent chains. Design/methodology/approach A steady-state thermal elastohydrodynamic lubrication (EHL) model is built using a Ree–Eyring fluid. The contact between the plate and the pin is simplified as a narrow finite line contact, and the lubrication state is examined by varying the geometry and the plate speed. Findings With increase in the equivalent radius of curvature, the pressure peak and the central film thickness increase. Because the plate is very thin, the temperature rise can be neglected. Even when the influence of the rounded corner region is less, a proper design can beneficially increase the minimum film thickness at both edges of the plate. Under a low entraining speed, strong stress concentration results in close-zero film thickness at both edges of the plate. Originality/value This study reveals the EHL feature of the narrow finite line contact in plate-pin pairs for silent chains and will support the future works considering transient effect, surface features and wear.

Analysis of EHL Circular Contact Shut Down

2002 ◽  
Vol 125 (1) ◽  
pp. 76-90 ◽  
Author(s):  
Jiaxin Zhao ◽  
Farshid Sadeghi
Keyword(s):  
Steady State ◽  
Film Thickness ◽  
Contact Area ◽  
Elastohydrodynamic Lubrication ◽  
Hertzian Contact ◽  
Analytical Prediction ◽  
Transient Pressure ◽  
Mean Velocity ◽  
Thickness Change ◽  
Contact Width

In this paper, an isothermal study of the shut down process of elastohydrodynamic lubrication under a constant load is performed. The surface mean velocity is decreased linearly from the initial steady state value to zero. The details of the pressure and film thickness distributions in the contact area are discussed for the two stages of shut down process, namely the deceleration stage and the subsequent pure squeeze motion stage with zero entraining velocity. The nature of the balance between the pressure, the wedge and the squeeze terms in Reynolds equation enables an analytical prediction of the film thickness change on the symmetry line of the contact in the deceleration period, provided that the steady state central film thickness relationship with velocity is known. The results indicate that for a fixed deceleration rate, if the initial steady state surface mean velocity is large enough, the transient pressure and film thickness distributions in the deceleration period solely depend on the transient velocity. The pressure and film thickness at the end of the deceleration period are then the same and do not depend on the initial steady state velocity. From the same initial steady state velocity, larger deceleration rates provide higher central pressure increase, but also preserve a higher film thickness in the contact area at the end of the deceleration period. Later in the second stage when the axisymmetric pressure and film thickness patterns typical of pure squeeze motion form, the pressure distribution in the contact area resembles a Hertzian contact pressure profile with a higher maximum Hertzian pressure and a smaller Hertzian half contact width. As a result, the film thickness is close to a parabolic distribution in the contact area. The volume of the lubricant trapped in the contact area is then estimated using this parabolic film thickness profile.

The Thermal Elastohydrodynamic Lubrication Analysis of Seawater-Lubricated Thordon Bearing

2011 ◽  
Vol 396-398 ◽  
pp. 2507-2510 ◽  
Author(s):  
Li Jing Zhang ◽  
You Qiang Wang
Keyword(s):  
Numerical Simulation ◽  
Film Thickness ◽  
Thermal Effect ◽  
Thermal Condition ◽  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Shaft Diameter ◽  
Pressure Peak

Based on Reynolds equation, the numerical simulation of thermal elstohydronamic lubrication for seawater-lubricated thordon bearing was carried out, the effects of the load, the speed and the shaft diameter on the pressure and the film thickness were discussed. The results show that thermal effect has little effect on the pressure, but the film thickness under the thermal condition is smaller than isothermal. The pressure peak is increased and the film thickness is decreased greatly with the increase of load. The pressure peak is decreased and the film thickness is increased greatly with the increase of speed.

Micro Thermal Elastohydrodynamic Lubrication Analysis of Power Law Water-Based Ferrofluid Journal Bearing

2013 ◽  
Vol 694-697 ◽  
pp. 543-546 ◽  
Author(s):  
Xiu Jiang Shi ◽  
You Qiang Wang
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Elastohydrodynamic Lubrication ◽  
Peak Height ◽  
Bearing Surface ◽  
Roughness Model ◽  
Water Based ◽  
Fluctuation Range ◽  
The Magnetic Field

Based on the Reynolds equation considering the temperature, the effection of non-newtonian and the magnetic field, the elastohydrodynamic lubrication(EHL) analysis of water-based ferrofluid journal bearing were carried out. The influence of roughness peak height and wavelength on the journal bearing surface with cosine roughness model were analysed. The results reveal that the pressure and film thickness of water-based ferrofluid wave apparently with roughness fluctuation; The fluctuation range of pressure and film thickness increase with the increase of roughness peak height, the minimal film thickness decreases; The pressure and film thickness fluctuation range become more and more sparse with the increase of roughness wavelength, the minimal film thickness increases.

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.

Influence of piezo-viscous behavior and load on the effectiveness of inlet zone bump in unidirectional pure sliding EHL line contacts

2018 ◽  
Vol 70 (9) ◽  
pp. 1766-1773
Author(s):  
Punit Kumar
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Governing Equations ◽  
Local Pressure ◽  
Content Type ◽  
Elasticity Equations ◽  
Line Contacts ◽  
Lower Load ◽  
Inlet Zone ◽  
Lubricant Viscosity

Purpose The purpose of this paper is to introduce the concept of stationary inlet zone bump (IZB) for film thickness enhancement in unidirectional pure sliding elastohydrodynamic lubrication (EHL) line contacts and to investigate the effects of maximum Hertzian pressure (load) and piezo-viscous response on the effectiveness of IZB. Design/methodology/approach The numerical analysis involves the solution of Reynolds and elasticity equations. The well-established Doolittle–Tait equations are used herein to determine the lubricant viscosity and density as functions of local pressure, while the Carreau model is used to describe the lubricant rheology. The IZB is assumed to have a sinusoidal profile and it is present on the stationary surface. The governing equations are discretized using finite difference scheme and solved using the Newton–Raphson technique. Findings Two test oils, L7808 and SR600, with linear and exponential piezo-viscous responses in the inlet zone are considered here for comparison. The effectiveness of IZB in terms of film thickness enhancement is found to be more for SR600. Besides, IZB is found to be more effective at lower values of maximum Hertzian pressure. The bump needs to shift downstream at higher load to be as effective as at lower load. Originality/value This is the first paper to simulate EHL characteristics in the presence of a stationary IZB and to study the effect of various parameters on EHL effectiveness. The film thickness enhancement obtained here is remarkable and hence it is a novel and valuable contribution.

Journal Bearing Surface Topography Design Based on Transient Lubrication Analysis

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Thomas Gu ◽  
Q. Jane Wang ◽  
Arup Gangopadhyay ◽  
Zhiqiang Liu
Keyword(s):  
Film Thickness ◽  
Journal Bearing ◽  
Mass Conservation ◽  
Friction Reduction ◽  
Bearing Surface ◽  
Surface Design ◽  
Thickness Increase ◽  
Film Thickness Increase ◽  
Lubrication Performance ◽  
Data Driven Approach

Abstract A transient mixed lubrication model is used to study the performance of a journal bearing subjected to impulse loading, considering mass conservation and the effects of asperities on flow and contact, to explore a novel journal bearing surface design methodology. The bearing surface features include an outlet pocket and axial lip for topographical design consideration. A data-driven approach for a steadily loaded bearing was first presented to illustrate the behavior of an indented pocket design at low and high loads, and Pareto optimization and sensitivity analysis methods were employed to analyze the data and provide insight to the design. The results show that the pocket location was the most influential parameter for the optimal bearing surface design for energy-efficient lubrication performance. For transient operation, a comprehensive parametric study was conducted, and the results reveal that, when compared to the results of the unmodified bearing, the bearing designed with the optimal outlet pocket can run at 9% lower mean friction while maintaining the baseline film thickness. The bearing with the lip feature shows a 20% minimum film thickness increase and 3% mean friction reduction. The design with outlet pocket and lip features combined can lead to 20% film thickness increase and 10% mean friction reduction.

Rough Air-Soft Elastohydrodynamic Lubrication

2013 ◽  
Vol 420 ◽  
pp. 30-35
Author(s):  
Khanittha Wongseedakaew ◽  
Jesda Panichakorn
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Modulus Of Elasticity ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Multilevel Methods ◽  
Inlet Temperature ◽  
Film Pressure ◽  
Air Inlet ◽  
Air Film

This paper presents the effects of rough surface air-soft elastohydrodynamic lubrication (EHL) of rollers for soft material under the effect of air molecular slip. The time independent modified Reynolds equation and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel methods were used to obtain the film pressure profiles and film thickness in the contact region. The effects of amplitude of surface roughness, modulus of elasticity and air inlet temperature are examined. The simulation results showed surface roughness has effect on film thickness but it little effect to air film pressure. When the amplitude of surface roughness and modulus of elasticity increased, the air film thickness decreased but air film pressure increased. However, the air inlet temperature increased when the air film thickness increased.

Thermal Elastohydrodynamic Lubrication of an Optimized Cam–Tappet Pair in Smooth Contact

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
W. Wu ◽  
J. Wang ◽  
C. H. Venner
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Temperature Profiles ◽  
Cam Mechanism ◽  
Basic Segment ◽  
Order Polynomial ◽  
Isothermal Analysis ◽  
Base Circle ◽  
Smooth Contact ◽  
Oil Characteristics

A high-order polynomial gas distribution cam mechanism is investigated theoretically from the viewpoint of thermal elastohydrodynamic lubrication (EHL). First, a cam with a larger base circle radius is employed, which results in slide–roll ratio 2.0 < S < 9.0 when the two surfaces move oppositely. The pressure, film thickness, and temperature profiles at a number of angular positions of the cam are presented, together with the isothermal results. The comparison between thermal and isothermal oil characteristics is also shown. It is revealed that the isothermal analysis partly overestimates the actual film thickness and it also misses some essential local phenomena. Second, a cam with a smaller base circle radius is studied, which leads to drastic variations in the slide–roll ratio which encounters four times’ occurrences of infinity in one working period. The pressure, film thickness, and temperature profiles at some angular cam positions together with the oil characteristics are given, showing much dramatic variations. A very small film thickness is observed at the contact of the tappet with the start of the cam basic segment, which suggests a possible risk of direct contact of both surfaces.

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