Investigation of Patterned Textures in Ball-on-Disk Lubricated Point Contacts

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Wang Wenzhong ◽  
Shen Dian ◽  
Zhang Shengguang ◽  
Zhao Ziqiang
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Contact Region ◽  
Point Contact ◽  
Friction Reduction ◽  
Hertzian Contact ◽  
Rheological Parameters ◽  
Boundary Edge ◽  
Optimal Distribution ◽  
Wide Range

The numerical simulations of surface textures in point-contact lubrication are conducted based on the unified Reynolds equation model. The textures are numerically produced on one of the interacting surfaces. The lubricant rheological parameters used in the simulations are calibrated by experiments. The numerical results show good agreements with those from experiments. The friction reduction mechanism is investigated by systemically analyzing the periodic change of friction coefficient of textures. It is illustrated that the transient friction coefficient is minimal when the dent moves to the front boundary edge of the Hertzian contact zone. A local film enhancement region will be formed on the trail of the dent within the Hertzian contact region. The results suggest that a bigger local film enhancement area will offer stronger film thickness enhancement as well as a lower friction coefficient. Different pattern distributions are also studied to find the optimal distribution of patterned textures, which not only achieves a lower friction coefficient, but also offers stronger film thickness enhancement; moreover, the optimal distribution is numerically proved to be applicable for a wide range of working conditions.

Influence of Laser Micro-Mesh Texturing on the Tribological Performance in an EHL Point Contact

2007 ◽  
Vol 353-358 ◽  
pp. 796-800
Author(s):  
Xiao Wang ◽  
Jian Li ◽  
Wei Chen ◽  
Lan Cai ◽  
Jian Ying Zhu
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Reynolds Equation ◽  
Point Contact ◽  
Tribological Performance ◽  
Design And Optimization ◽  
Thickness Profile ◽  
Wide Range ◽  
Key Factor

Fabricating surfaces with controlled micro-geometry may be an effective approach to improved tribological performance. In this paper, the effect of laser surface micro-mesh texturing on the tribological performance is investigated theoretically with numerical solution of EHL point contact. In the theoretical model, the Reynolds equation is used as the governing equation. Well controlled micro-mesh texturing is described in film thickness equation. By Full Multi-Grid (FMG) method, the solutions of film thickness profile and pressure distribution map are present over a wide range of texturing parameters. The influence of width, depth and orientation of mesh texturing on the friction coefficient is analyzed. Result shows that, the film thickness profile and pressure distribution are sensitive to the parameters of micro-mesh texturing. The curve result of friction coefficient under two load conditions indicated that the parameters of mesh are key factor for texturing design. Solutions demonstrate the ability of numerical simulation on the design and optimization of surface mesh texturing.

scholarly journals A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

2017 ◽  
Vol 232 (11) ◽  
pp. 2088-2102 ◽  
Author(s):  
Eduardo de la Guerra Ochoa ◽  
Javier Echávarri Otero ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thermal Effects ◽  
Good Accuracy ◽  
Computational Cost ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
New Approach ◽  
Ball On Disc

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.

scholarly journals The Effects of Artificially-Produced Defects on the Film Thickness Distribution in Sliding EHD Point Contacts

1982 ◽  
Vol 104 (3) ◽  
pp. 365-375 ◽  
Author(s):  
C. Cusano ◽  
L. D. Wedeven
Keyword(s):  
Film Thickness ◽  
Contact Region ◽  
Thickness Distribution ◽  
Point Contact ◽  
Optical Interferometry ◽  
Point Contacts ◽  
Thickness Profile ◽  
Inlet Region

The effects of artificially-produced dents and grooves on the elastohydrodynamic (EHD) film thickness profile in a sliding point contact are investigated by means of optical interferometry. The defects, formed on the surface of a highly polished ball, are held stationary at various locations within and in the vicinity of the contact region while the disk is rotating. It is shown that the defects, having a geometry similar to what can be expected in practice, can dramatically change the film thickness which exists when no defects are present in or near the contact. This change in film thickness is mainly a function of the position of the defects in the inlet region, the geometry of the defects, the orientation of the defects in the case of grooves, and the depth of the defect relative to the central film thickness.

Effect of Stiff Coatings on EHL Film Thickness in Point Contacts

2007 ◽  
Author(s):  
Yuchuan Liu ◽  
Q. Jane Wang ◽  
Dong Zhu
Keyword(s):  
Film Thickness ◽  
Working Conditions ◽  
Coating Thickness ◽  
Point Contact ◽  
Thickness Variation ◽  
Point Contacts ◽  
Lubricant Film Thickness ◽  
Wide Range ◽  
Minimum Film Thickness ◽  
Coating Material Properties

This study investigates the influences of coating material properties and coating thickness on lubricant film thickness based on a point-contact isothermal EHL model developed recently by the authors. The results present the trend of minimum film thickness variation as a function of coating thickness and elastic modulus under a wide range of working conditions. Numerical results indicates that the increase in minimum film thickness, Imax, and the corresponding optimal dimensionless coating thickness, H2, can be expressed in the following formulas: Imax=0.766M0.0248R20.0296L0.1379exp(−0.0245ln2L)H2=0.049M0.4557R2−0.1722L0.7611exp(−0.0504ln2M−0.0921ln2L) These formulas can be used to estimate the effect of a coating on EHL film thickness.

Effects of Surface Roughness and Surface Force on the Thin Film Elastohydrodynamic Lubrication of Circular Contacts

2012 ◽  
Vol 67 (6-7) ◽  
pp. 412-418
Author(s):  
Li-Ming Chu ◽  
Jaw-Ren Lin ◽  
Jiann-Lin Chen
Keyword(s):  
Thin Film ◽  
Surface Roughness ◽  
Film Thickness ◽  
Contact Region ◽  
Load Condition ◽  
Elastohydrodynamic Lubrication ◽  
Surface Force ◽  
Surface Forces ◽  
Hertzian Contact ◽  
Deformation Equation

The effects of surface roughness and surface force on thin film elastohydrodynamic lubrication (TFEHL) circular contact problems are analyzed and discussed under constant load condition. The multi-level multi-integration (MLMI) algorithm and the Gauss-Seidel iterative method are used to simultaneously solve the average Reynolds type equation, surface force equations, the load balance equation, the rheology equations, and the elastic deformation equation. The simulation results reveal that the difference between the TFEHL model and the traditional EHL model increase with decreasing film thickness. The effects of surface forces become significant as the film thickness becomes thinner. The surface forces have obvious effects in the Hertzian contact region. The oscillation phenomena in pressure and film thickness come mainly from the action of solvation forces

Optical Interferometric Observations of the Effects of a Bump on Point Contact EHL

1992 ◽  
Vol 114 (4) ◽  
pp. 779-784 ◽  
Author(s):  
M. Kaneta ◽  
T. Sakai ◽  
H. Nishikawa
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Numerical Simulations ◽  
Contact Region ◽  
Thickness Distribution ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Interesting Phenomenon ◽  
Contact Conditions ◽  
Average Speed

The effects of surface kinematic conditions on micro-elastohydrodynamic lubrication (micro-EHL) are investigated under rolling and/or sliding point contact conditions using the optical interferometry technique. A long bump of chromium sputtered on the surface of a highly polished ball is used as a model asperity. It is shown that the film thickness distribution or the elastic deformation of the bump is influenced significantly by the surface kinematic conditions and the orientation of the bump. An interesting phenomenon is also found when contacting surfaces move with different speeds; the thin film formed on a transversely oriented bump existing at the entrance of the contact travels through the contact region at the average speed of the surfaces. The experimental results obtained qualitatively confirm published numerical simulations.

Effect of Liquid-Solid Lubricant on Mixed Lubrication in Line Contact

2011 ◽  
Vol 148-149 ◽  
pp. 778-784
Author(s):  
Rattapasakorn Sountaree ◽  
Panichakorn Jesda ◽  
Mongkolwongrojn Mongkol
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Solid Lubricant ◽  
Reynolds Equation ◽  
Contact Region ◽  
Mixed Lubrication ◽  
Line Contact ◽  
Load Carrying ◽  
Roughness Amplitude ◽  
Raphson Method

This paper presents the performance characteristics of two surfaces in line contact under isothermal mixed lubrication with non-Newtonian liquid–solid lubricant base on Power law viscosity model. The time dependent Reynolds equation, elastic equation and viscosity equation were formulated for compressible fluid. Newton-Raphson method and multigrid technique were implemented to obtain film thickness profiles, friction coefficient and load carrying in the contact region at various roughness amplitudes, applied loads, speeds and the concentration of solid lubricant. The simulation results showed that roughness amplitude has a significant effect on the film pressure, film thickness and surface contact pressure in the contact region. The film thickness decrease but friction coefficient and asperities load rapidly increases when surface roughness amplitude increases or surface speed decreases. When the concentration of solid lubricant increased, friction coefficient and asperities load decrease but traction and film thickness increase.

Elastohydrodynamic Lubrication Analysis of Conjugate Meshing Face Gear Pairs

2012 ◽  
Vol 57 (3) ◽  
pp. 1-10 ◽  
Author(s):  
Zihni B. Saribay ◽  
Robert C. Bill ◽  
Edward C. Smith ◽  
Suren B. Rao
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Gear Tooth ◽  
Elastohydrodynamic Lubrication ◽  
Transmission Efficiency ◽  
Hertzian Contact ◽  
Maximum Efficiency ◽  
Gear Pair ◽  
Face Gear ◽  
Fixed Axis

This paper investigates the nominal elastohydrodynamic lubrication (EHL) characteristics of the conjugate meshing face gears and predicts the mesh efficiency of the pericyclic transmission system. The meshing face-gear tooth geometries and meshing kinematics are modeled. Hertzian contact and the isothermal non-Newtonian lubricant film characteristics of the meshing face-gear pair are investigated. The friction coefficient is calculated with the effects of lubricant behavior and mesh kinematics. Finally, the pericyclic transmission efficiency is calculated as a function of friction coefficient, mesh loads, and mesh kinematics. The Hertzian contact behavior, film thickness, and friction coefficient values are simulated for an example fixed axis face-gear pair rotating at 1000 rpm with 3.4 kN-m torque. The EHL film thickness ranges from 0.1 to 0.25 μm in this example. The average friction coefficient is predicted as 0.05. The efficiencies of three different 24:1 reduction ratio 760 HP pericyclic transmission designs are investigated. The minimum and maximum efficiency in the given design space are 97% and 98.7%, respectively.

scholarly journals Multiscale Analysis of the Roughness Effect on Lubricated Rough Contact

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Ibrahim Demirci ◽  
Sabeur Mezghani ◽  
Mohammed Yousfi ◽  
Mohamed El Mansori
Keyword(s):  
Friction Coefficient ◽  
Point Contact ◽  
Friction Reduction ◽  
Real Surface ◽  
Surface Geometry ◽  
Roughness Effects ◽  
Multiscale Decomposition ◽  
Lubricated Contact ◽  
Major Factors ◽  
Film Lubrication

Determining friction is as equally essential as determining the film thickness in the lubricated contact, and is an important research subject. Indeed, reduction of friction in the automotive industry is important for both the minimization of fuel consumption as well as the decrease in the emissions of greenhouse gases. However, the progress in friction reduction has been limited by the difficulty in understanding the mechanism of roughness effects on friction. It was observed that micro-surface geometry or roughness was one of the major factors that affected the friction coefficient. In the present study, a new methodology coupling the multiscale decomposition of the surface and the prediction of the friction coefficient by numerical simulation was developed to understand the influence of the scale of roughness in the friction coefficient. In particular, the real surface decomposed in different roughness scale by multiscale decomposition, based on ridgelets transform, was used as input into the model. This model predicts the effect of scale on mixed elastohydroynamic point contact. The results indicate a good influence of the fine scale of surface roughness on the friction coefficient for full-film lubrication as well as a beginning of improvement for mixed lubrication.

A theoretical analysis of the isothermal elastohydrodynamic lubrication of concentrated contacts. II. General case, with lubricant entrainment along either principal axis of the Hertzian contact ellipse or at some intermediate angle

1985 ◽  
Vol 397 (1813) ◽  
pp. 271-294 ◽  
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Major Axis ◽  
Hertzian Contact ◽  
Analysis And Design ◽  
Principal Axes ◽  
Wide Range ◽  
Central Regions ◽  
Machine Elements ◽  
Initial Objective

The initial objective of the work reported in this paper was the development of generalized representations of film thickness results for elastohydrodynamic conjunctions in which lubricant entrainment coincided with one of the principal axes of the Hertzian conjunction. Some 106 solutions have been considered, including 33 presented in part I for entrainment along the major axis, four further solutions of a similar kind, the 34 solutions presented by Hamrock & Dowson ( J. lubr. Technol . 98, 264-276 (1977)) for entrainment along the minor axis and 35 new solutions for similar geometries. It has been shown that normalization of the principal parameters in terms of the curvature in the direction of lubricant entrainment, 1/ R e , permits the display of both central and minimum film thickness values as functions of the ratio of the radii of the solids normal to, and in the direction of, lubricant entrainment. These continuous curves enable film thickness to be predicted over a very wide range of geometrical configurations, but valid empirical expressions for both central and minimum dimensionless film thickness have also been developed. The second major feature of the study was to develop elastohydrodynamic solutions for the non-symmetrical conditions encountered when the lubricant entraining vector did not coincide with either of the principal axes of the conjunction. Such solutions are more representative of the conditions encountered in certain machine elements than the symmetrical solutions already reported. Examples of the resulting nonsymmetrical pressure distributions, elastic deformations and film shapes are presented. It is shown that normalization in terms of the curvature in the direction of lubricant entrainment, and the use of a simple trigonometric function, enables both the central and minimum film thicknesses to be predicted for any entrainment angle. It is demonstrated that this comprehensive and generalized presentation of new and previous solutions to the elastohydrodynamic lubrication problem for elliptical conjunctions yields film thickness predictions that compare very well indeed with specific solutions reported earlier. It is further shown that the central film thickness is little affected by the orientation of the lubricant entraining vector for many ellipsoidal solids, but that the minimum film thicknesses encountered cover a much wider range of values. In many cases the minimum film thicknesses occur in side-lobes located near the lateral boundaries of the Hertzian conjunction, which perform a sealing role and thus permit the generation of near-Hertzian hydrodynamic pressures in the central regions of the conjunction. The results are expected to provide a basis for the analysis and design of a wide range of machine elements operating in the elastohydrodynamic régime of lubrication.

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