scholarly journals Lubricant film formation in rough surface non-conformal conjunctions subjected to GPa pressures and high slide-to-roll ratios

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jonny Hansen ◽  
Marcus Björling ◽  
Roland Larsson
Keyword(s):  
Surface Roughness ◽  
Film Formation ◽  
Operating Conditions ◽  
Thin Film Lubrication ◽  
Initial State ◽  
Oil Film ◽  
Post Test ◽  
Surface Irregularities ◽  
Film Lubrication ◽  
Ball On Disc

AbstractA ball-on-disc machine was employed in a highly idealised setting to study the interplay between oil film formation and surface irregularities in single-sided rough elasto-hydrodynamic lubricated (EHL) conjunctions. The tests were operated under GPa pressures and high slide-to-roll ratios in a situation where the separating gap was smaller than the combined surface roughness height. Under the initial state of solid contact interference and with the operating conditions held fixed, surfaces were found to gradually conform such that a fully separating oil film of nanometre thickness eventually developed—a thin film lubrication state known as micro-EHL. Additionally, with a previously developed approach for 3D surface re-location analysis, we were able to very precisely specify the pertained nature of surface transformations, even at the asperity scale, by comparing the post-test surfaces to those in the virgin state. The surface roughness Sq was reduced by up to 17% after running-in, while the speed required for full film EHL was reduced by a remarkable 90%. Hence, full film EHL is possible even in cases where the Λ-ratio falsely suggests boundary lubrication. This discrepancy was attributed to the way surfaces are deformed inside the contact, i.e., through the establishment of micro-EHL.

Thermohydrodynamic Lubrication Analysis of Misaligned Plain Journal Bearing With Rough Surface

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Jun Sun ◽  
Mei Deng ◽  
Yonghong Fu ◽  
Changlin Gui
Keyword(s):  
Surface Roughness ◽  
Thermal Effect ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Eccentricity Ratio ◽  
Oil Viscosity ◽  
Oil Film ◽  
Lubrication Performance ◽  
Journal Misalignment

Journal misalignment exists generally in journal bearings. When severe journal misalignment takes place, the minimum film thickness of journal bearings reduces greatly. In this condition, the surface roughness, the oil viscosity-pressure relationship (VPR), and the thermal effect have obvious effects on hydrodynamic lubrication performance of misaligned bearings. In this paper, the oil film pressure, oil film temperature, load-carrying capacity, end leakage flow rate, frictional coefficient, and misalignment moment of a journal bearing with different angles of journal misalignment and surface roughness, and considering oil VPR and thermal effect, were calculated based on the generalized Reynolds equation, energy equation, and solid heat conduction equation. The results show that the oil VPR and surface roughness have a significant effect on the lubrication of misaligned journal bearings under large eccentricity ratio. The thermal effect will affect obviously the lubrication of misaligned journal bearings when eccentricity ratio and angle of journal misalignment are all large. In the present design, the size of the journal bearing is compact more and more, and the eccentricity ratio and angle of journal misalignment are usually large in operating conditions. Therefore, it is necessary to take the effects of journal misalignment, surface roughness, oil VPR, and thermal effect into account in the design and analyses of journal bearings.

scholarly journals A New Film Parameter for Rough Surface EHL Contacts with Anisotropic and Isotropic Structures

2021 ◽  
Vol 69 (2) ◽  
Author(s):  
Jonny Hansen ◽  
Marcus Björling ◽  
Roland Larsson
Keyword(s):  
Surface Roughness ◽  
Hydrodynamic Lubrication ◽  
Major Advance ◽  
Microscopic Scale ◽  
Film Parameter ◽  
Anisotropic Structures ◽  
Surface Irregularities ◽  
Optimal Efficiency ◽  
The 1960S ◽  
Ball On Disc

AbstractNumerous tribological contacts worldwide rely on adequate lubrication quality for proper functionality. Despite this, there is no existing approach to accurately predict the state of lubrication. The default model since introduced in the 1960s—the $$\Lambda$$ Λ -ratio, defined as the oil film thickness over the surface roughness height—is unpredictable and may yield erroneous results. Here, we put forward a framework for a new updated film parameter, $${\Lambda }^{*}$$ Λ ∗ , which accounts for the elasto-hydrodynamic lubrication (EHL) effects induced by surface irregularities on the microscopic scale (micro-EHL). This new film parameter was validated in ball-on-disc tribological tests with engineering surfaces comprising isotropic and anisotropic structures. As expected, the new model was found to accurately predict the experimentally measured true mixed and full-film EHL regimes. The ability to accurately predict the mode of lubrication represents a major advance in designing tribological interfaces for optimal efficiency and durability.

Numerical Solution of Mixed Thermal Elastohydrodynamic Lubrication in Point Contacts With Three-Dimensional Surface Roughness

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Xiaopeng Wang ◽  
Yuchuan Liu ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Thickness Variation ◽  
Wide Range ◽  
Film Lubrication

Elastohydrodynamic lubrication (EHL) is a common mode of fluid-film lubrication in which many machine elements operate. Its thermal behavior is an important concern especially for components working under extreme conditions such as high speeds, heavy loads, and surfaces with significant roughness. Previous thermal EHL (TEHL) studies focused only on the cases with smooth surfaces under the full-film lubrication condition. The present study intends to develop a more realistic unified TEHL model for point contact problems that is capable of simulating the entire transition of lubrication status from the full-film and mixed lubrication all the way down to boundary lubrication with real machined roughness. The model consists of the generalized Reynolds equation, elasticity equation, film thickness equation, and those for lubricant rheology in combination with the energy equation for the lubricant film and the surface temperature equations. The solution algorithms based on the improved semi-system approach have demonstrated a good ability to achieve stable solutions with fast convergence under severe operating conditions. Lubricant film thickness variation and temperature rises in the lubricant film and on the surfaces during the entire transition have been investigated. It appears that this model can be used to predict mixed TEHL characteristics in a wide range of operating conditions with or without three-dimensional (3D) surface roughness involved. Therefore, it can be employed as a useful tool in engineering analyses.

scholarly journals Molecular behaviors in thin film lubrication—Part one: Film formation for different polarities of molecules

Friction ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 372-387 ◽  
Author(s):  
Shaohua Zhang ◽  
Yijun Qiao ◽  
Yuhong Liu ◽  
Liran Ma ◽  
Jianbin Luo
Keyword(s):  
Thin Film ◽  
Film Formation ◽  
Thin Film Lubrication ◽  
Film Lubrication

scholarly journals Tribological properties of termally sprayed WC cermet coating under extreme operating conditions

1970 ◽  
Vol 39 (1) ◽  
pp. 13-17
Author(s):  
DM Nuruzzaman ◽  
Akira Nakajima ◽  
Toshifumi Mawatari
Keyword(s):  
Surface Roughness ◽  
Tribological Properties ◽  
Surface Finish ◽  
Substrate Surface ◽  
Surface Hardness ◽  
Operating Conditions ◽  
Material Loss ◽  
Slip Ratio ◽  
Oil Film ◽  
Cermet Coating

In this study, tribological properties of thermally sprayed WC-Cr-Ni cermet coating were investigated experimentally under lubricated rolling with sliding contact conditions. Hi-HVOF sprayed WC cermet coatings were deposited onto the axially ground, blasted and circumferentially ground roller specimens made of carburized hardened steel. Under extreme operating conditions such as contact pressure PH = 1.4 GPa, slip ratio s = - 28.0% and mating surface roughness Rmax = 6.0 µm, the effects of substrate surface finish on the tribological properties of the cermet coating were examined. It was found that cermet coating showed a long life and durability was not influenced by the substrate surface finish. It was also found that coefficient of friction, oil film formation, surface temperature and oil film thickness were not much influenced by the substrate surface finish. On the other hand, surface hardness, surface roughness and coating material loss were significantly influenced depending on the substrate surface finish. Keywords: Substrate surface finish, Tribological properties, WC-Cr-Ni cermet doi:10.3329/jme.v39i1.1828 Journal of Mechanical Engineering, vol. ME39, No. 1, June 2008 13-17

Surface roughness effects on non-Newtonian MHD non-parallel squeeze film bearing

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mouhcine Mouda ◽  
Mohamed Nabhani ◽  
Mohamed El Khlifi
Keyword(s):  
Surface Roughness ◽  
Peer Review ◽  
Load Capacity ◽  
Homogenization Method ◽  
Squeeze Film ◽  
Squeezing Effect ◽  
Thin Film Lubrication ◽  
Roughness Effects ◽  
Content Type ◽  
Film Lubrication

Purpose The purpose of this paper is to examine the effect of surface roughness on the magneto-hydrodynamic (MHD) non-parallel squeeze film lubrication using non-Newtonian lubricant. Design/methodology/approach Based on the MHD thin film lubrication theory and the Stokes theory and homogenization method, the homogenized MHD Reynolds equation is derived considering the squeezing effect. Findings It is found that the obtained results indicate that the interaction among non-Newtonian, MHD and surface roughness influences is significant. Originality/value This study is original which compares the dimensionless load capacity and dimensionless response time among transverse, longitudinal and, for the first time, anisotropic surface roughness types under magneto-hydrodynamic non-Newtonian non-parallel squeeze film lubrication. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2020-0071/

Lubrication characteristics of the worn slipper in the slipper-swashplate pair

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Haiji Wang ◽  
Guanglin Shi
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Design Methodology ◽  
Reynolds Equation ◽  
Thickness Distribution ◽  
Operating Conditions ◽  
Test Rig ◽  
Content Type ◽  
Oil Film ◽  
Lubrication Characteristics

Purpose This paper proposes the lubrication characteristics of the worn slipper in the slipper–swashplate pair. The mathematical analysis of lubrication characteristics of slipper with the measured surface roughness distribution is introduced. Based on the results from the test rig, it carries out the result compassion in different operating conditions. Design/methodology/approach This paper introduces the measured surface roughness distribution of new and used slippers and generates the oil film thickness distribution with it. An average flow Reynolds equation of the pressure distribution is introduced too. The experimental results are carried out on a novel adjustable oil film thickness test rig. Findings The surface roughness of the worn slipper enlarges the reacting force and torque only if the oil film thickness is small. When the ratio of oil film thickness to the root mean square of surface roughness is much smaller than 3, the influence of it on torque is obvious. Originality/value Different surface roughness of worn slipper proposed in this paper has an influence on the lubrication characteristics. As the slipper is worn after a period of use, the changed lubrication characteristics should be considered in the slipper design.

scholarly journals A New Approach for Estimating the Friction in Thin Film Lubrication

2010 ◽  
Vol 2010 ◽  
pp. 1-15 ◽  
Author(s):  
Dag Lukkassen ◽  
Annette Meidell ◽  
Peter Wall
Keyword(s):  
Surface Roughness ◽  
Variational Problem ◽  
Reynolds Equation ◽  
Main Idea ◽  
Thin Film Lubrication ◽  
New Approach ◽  
Fine Mesh ◽  
Load Carrying ◽  
Film Lubrication ◽  
Effect Of Surface

An important problem in the theory of lubrication is to model and analyze the effect of surface roughness on, for example, the friction and load carrying capacity. A direct numerical computation is often impossible since an extremely fine mesh is required to resolve the surface roughness. This suggests that one applies some averaging technique. The branch in mathematics which deals with this type of questions is known as homogenization. In this paper we present a completely new method for computing the friction. The main idea is that we study the variational problem corresponding to the Reynolds equation. We prove that the homogenized variational problem is closely related to the homogenized friction. Finally we use bounds on the homogenized Lagrangian to derive bounds for the friction. That these bounds can be used to efficiently compute the friction is demonstrated in a typical example.

The Influence of Surface Roughness on Elastohydrodynamic Journal Bearing With Non-Newtonian Lubricants

2005 ◽  
Author(s):  
Mongkol Mongkolwongrojn ◽  
Chatchai Aiumpornsin ◽  
Somnuk Yawong
Keyword(s):  
Surface Roughness ◽  
Elastic Deformation ◽  
Journal Bearing ◽  
Load Capacity ◽  
Elastohydrodynamic Lubrication ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Static Characteristics ◽  
Heavy Load ◽  
Oil Film

In this paper, the effect of surface roughness and elastic deformation of bearing liner on the static characteristics of journal bearings are presented. A power law model is developed for the elastohydrodynamic lubrication regime. The modified Reynolds equations with elasticity equation were formulated for the elastohydrodynamic journal bearings under heavy load conditions. Multigrid and multilevel technique with Newton’s method were used to calculated the elastohydrodynamic bearing to obtain the oil film pressure profile, oil film thickness profile, load capacity, attitude angle and friction coefficient at various surface roughness parameters. The static characteristics of the rough elastohydrodynamic journal bearing were compared with that of the rough hydrodynamic journal bearings. The results show that the surface roughness and elastic deformation significantly affect the static characteristics of journal bearings under severe operating conditions.

The behaviour of heavily loaded line contacts with transverse roughness

1999 ◽  
Vol 213 (4) ◽  
pp. 309-320 ◽  
Author(s):  
C. J. Hooke
Keyword(s):  
Surface Roughness ◽  
Full Range ◽  
Numerical Results ◽  
Operating Conditions ◽  
Entrainment Velocity ◽  
Original Surface ◽  
Line Contacts ◽  
Transverse Roughness ◽  
Inlet Length

In heavily loaded, piezoviscous contacts the surface roughness tends to be flattened inside the conjunction by any relative sliding of the surfaces. However, before it is flattened, the roughness affects the inlet to the contact, producing clearance variations there. These variations are then convected through the contact, at the entrainment velocity, producing a clearance distribution that differs from the original surface. The present paper explores this behaviour and establishes how the amplitude of the convected clearance varies with wavelength and operating conditions. It is shown that the primary influence is the ratio of the wavelength to the inlet length of the conjunction. Where this ratio is large, the roughness is smoothed and there is little variation in clearance under the conjunction. Where the ratio is small, significant variations in clearance may occur but the precise amplitude and phasing depend on the ratio of slide to roll velocities and on the value of a piezoviscous parameter, c. The numerical results agree closely with existing solutions but extend these to cover the full range of operating conditions.

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