A Study on the Influence of Micro Surface Texture on Mixed EHL Friction

2017 ◽  
Author(s):  
Sheng Li ◽  
Utsav Parmar
Keyword(s):  
Surface Texture ◽  
Point Contact ◽  
Ground Surface ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Polished Surface ◽  
Surface Versus ◽  
Friction Performance ◽  
The Impact ◽  
Micro Dimple

In this work, the impact of the surface micro-dimple arrays on the frictional behavior under the mixed elastohydrodynamic lubrication condition is examined, considering a point contact problem. The interested geometric parameters of the micro-dimple arrays include the dimple center distance and the dimple depth. To quantify the influence of these parameters on the friction coefficient, a computational approach is implemented. In addition, different surface texture combinations, namely micro-dimpled and polished surface versus polished surface, polished surface versus polished surface and ground surface versus ground surface, are compared to determine any advantage or disadvantage of micro-dimpled surfaces on the aspect of the friction performance under the typical gearing application operating conditions.

The Isothermal Elastohydrodynamic Lubrication of Spheres

1981 ◽  
Vol 103 (4) ◽  
pp. 547-557 ◽  
Author(s):  
H. P. Evans ◽  
R. W. Snidle
Keyword(s):  
Iterative Method ◽  
Reynolds Equation ◽  
Point Contact ◽  
Numerical Procedure ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Operating Conditions ◽  
Analysis Of Results ◽  
Approximate Formulas ◽  
Pressure Analysis

The paper describes a numerical procedure for solving the point-contact elastohydrodynamic lubrication problem under isothermal conditions at moderate loads. Results are presented showing the shape of the film and variation of hydrodynamic pressure. Analysis of results for a range of operating conditions gives the following approximate formulas for minimum and central film thickness, repsectively: Hm = 1.9 M−0.17 L0.34 and Ho = 1.7 M−0.026 L0.40 where H, M, and L are the Moes and Bosma nondimensional groups. In common with earlier solutions based upon the forward-iterative method the solution breaks down under moderately heavily loaded conditions. Ways of extending the solution to heavier loads using the authors’ inverse solution of Reynolds’ equation under point-contact elastohydrodynamic conditions are discussed.

Flow Continuity of Isothermal Elastohydrodynamic Point-Contact Lubrication under Different Numerical Iteration Configurations

2021 ◽  
pp. 1-26
Author(s):  
Liangwei Qiu ◽  
Shuangbiao Liu ◽  
Zhijian Wang ◽  
Xiaoyang Chen
Keyword(s):  
Error Control ◽  
Multigrid Method ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Point Contacts ◽  
Numerical Iteration ◽  
Mesh Method ◽  
Iteration Methods ◽  
Relaxation Factors

Abstract Elastohydrodynamic Lubrication (EHL) in point contacts can be numerically solved with various iteration methods, but so far the flow continuity of such solutions has not been explicitly verified. A series of closed regions with the same inlet side boundary is defined and two treatments to total all flows related to the other boundaries of the closed regions are defined to enable flow continuity verifications. The multigrid method and the traditional single mesh method with different relaxation configurations are utilized to solve different cases to evaluate computation efficiencies. For the multigrid method, the combination of a pointwise solver together with hybrid relaxation factors is identified to perform better than other combinations. The single mesh method has inferior degrees of flow continuity than the multigrid method and needs much smaller error control values of pressure to achieve a decent level of flow continuity. Because flow continuity has a physical meaning, its verifications should be routinely included in any self-validation process for any EHL results. Effects of control errors of pressure, mesh sizes, differential schemes and operating conditions on flow continuities are studied. Then, trends of film thickness with respect to speed are briefly discussed with meshes up to 4097 by 4097.

scholarly journals Multiphysics Investigations on the Dynamics of Differential Hypoid Gears

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
M. Mohammadpour ◽  
S. Theodossiades ◽  
H. Rahnejat
Keyword(s):  
Multiscale Analysis ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Transmission Efficiency ◽  
Operating Conditions ◽  
Hypoid Gear ◽  
Tooth Contact Analysis ◽  
Hypoid Gears ◽  
Gear Teeth ◽  
Noise Vibration

Vehicular differential hypoid gears play an important role on the noise, vibration, and harshness (NVH) signature of the drivetrain system. Additionally, the generated friction between their mating teeth flanks under varying load-speed conditions is a source of power loss in a drivetrain while absorbing some of the vibration energy. This paper deals with the coupling between system dynamics and analytical tribology in multiphysics, multiscale analysis. Elastohydrodynamic lubrication (EHL) of elliptical point contact of partially conforming hypoid gear teeth pairs with non-Newtonian thermal shear of a thin lubricant film is considered, including boundary friction as the result of asperity interactions on the contiguous surfaces. Tooth contact analysis (TCA) has been used to obtain the input data required for such an analysis. The dynamic behavior and frictional losses of a differential hypoid gear pair under realistic operating conditions are therefore determined. The detailed analysis shows a strong link between NVH refinement and transmission efficiency, a finding not hitherto reported in literature.

Pavement Friction Modeling using Texture Measurements and Pendulum Skid Tester

2018 ◽  
Vol 2672 (40) ◽  
pp. 440-451 ◽  
Author(s):  
Ahmad Alhasan ◽  
Omar Smadi ◽  
Georges Bou-Saab ◽  
Nacu Hernandez ◽  
Eric Cochran
Keyword(s):  
Surface Texture ◽  
Friction Model ◽  
Operating Conditions ◽  
Friction Modeling ◽  
Friction Forces ◽  
Frictional Behavior ◽  
Kinetic Coefficients ◽  
Friction Measurements ◽  
The Impact ◽  
Pavement Friction

Pavement frictional behavior affects pavement performance in terms of vehicle safety, fuel consumption, and tire wear. Comprehending and interpreting pavement friction measurements is a challenging task, because of friction sensitivity to several uncontrollable factors. These factors include: pavement surface conditions, such as the type and thickness of contaminants and fluids on the surface and their interaction with friction forces; and the device operating conditions, such as sliding speed, material properties and geometry of the rubber slider used, and operating temperature. Despite the efforts to describe and quantify the impact of varying conditions on pavement friction, which ultimately will allow for a better harmonization of friction measurements, there is a need to better understand the link between the surface texture and physical friction measurements. In this paper, Persson’s friction model is used to analyze and understand the impact of surface texture on frictional behavior of dry pavement surfaces. The model was used to analyze 18 test locations, which were compared with the dry kinetic coefficients of friction (COF) estimated using a British pendulum tester (BPT). The results show that Persson’s friction model could predict the COF estimated from the BPT results with relatively high accuracy. In addition, the model could provide a profound explanation of the frictional forces mechanism. Finally, it was found that the mean profile depth (MPD) cannot provide a full picture of the frictional behavior. However, combining MPD with the Hurst exponent, texture measurements can potentially provide a full physical explanation of the frictional behavior for road surfaces.

scholarly journals The Effects of Microdimple Texture on the Friction and Thermal Behavior of a Point Contact

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
S. Li ◽  
U. Parmar
Keyword(s):  
Surface Temperature ◽  
High Speed ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Disk Surface ◽  
Underlying Mechanism ◽  
Surface Versus ◽  
Ball Surface ◽  
Two Parameters

This study investigates the effects of the microdimple texture on the friction and surface temperature performances of a ball-on-disk contact, operating under the speed and load ranges that cover typical gearing applications. Circular-shaped microdimple arrays with different dimple center distances and dimple depths are implemented on the ball surface to quantify the impacts of these two parameters on the friction coefficient and the maximum ball surface temperature. In addition, the contacts of three surface texture combinations, namely microdimpled and polished ball surface versus polished disk surface, polished ball surface versus polished disk surface, and ground ball surface versus ground disk surface, are compared to demonstrate any beneficial or detrimental effect of microdimples in heavily loaded high-speed applications. This study adopts a thermal mixed EHL point contact model, whose capability and accuracy have been well demonstrated by comparing to the experimental measurements, to quantify the deterministic tribological behavior within the contact, allowing the exploration of the underlying mechanism that governs the role of microdimples in the elastohydrodynamic lubrication (EHL).

Transient elastohydrodynamic lubrication of rectangular elastomeric seals for linear hydraulic actuators

2003 ◽  
Vol 217 (6) ◽  
pp. 461-473 ◽  
Author(s):  
G. K. Nikas
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Complete Analysis ◽  
Transient Effects ◽  
Hydraulic Actuators ◽  
Applicable Range ◽  
Friction Performance ◽  
Time Variables ◽  
Elastomeric Seals ◽  
Elasticity Effects

A numerical model developed previously by the author to study rectangular rubber seals for reciprocating piston rods in hydraulic actuators is extended to include transient effects, considering the sealed pressure and the stroking velocity of the piston rod as time variables. The model incorporates various improvements regarding the treatment of seal extrusion, non-linear seal elasticity effects, as well as the modelling of back-up rings at the air side of the actuator, all of which have been dealt with individually in previous studies by the author. These new features are combined in the present model for a complete analysis of the leakage and friction performance of the seal-ring system under real transient operating conditions of industrial and aircraft actuators, including thermal effects and rough-contact analysis, and covering the widest applicable range of sealed pressures (over 0.1 MPa) and operating temperatures (− 60 to + 140°C).

Elastohydrodynamic Lubrication in Ball Thrust Bearing

2016 ◽  
Vol 835 ◽  
pp. 593-598
Author(s):  
Khanittha Wongseedakaew
Keyword(s):  
Film Thickness ◽  
Applied Load ◽  
Thrust Bearing ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Surface Velocity ◽  
Load Increase ◽  
Finite Different Method ◽  
Raphson Method

This paper presents the theoretical characteristics of elastohydrodynamic lubrication (EHL) in point contact under steady operating conditions of ball bearing thrust bearing. The numerical simulations employed a finite different method, Newton Raphson method and multigrid method to solve the modified Reynolds equation with a Non-Newtonian fluid. The general numerical schemes are implemented to investigate the profile of pressure and film thickness, with varying applied loads viscosity of lubricants and speeds. The results show that the applied load has significant effect on the film thickness profile. The contact is increase area but film thickness decrease as the applied load increase. The minimum film thickness and friction coefficient both increase significantly as viscosity of lubricant is increased. The increasing of surface velocity, the film thickness increase but film pressure decrease.

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.

On the Behavior of Friction in Lubricated Point Contact With Provision for Surface Roughness

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
H. Sojoudi ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Type Curve ◽  
Lift Off

This paper presents a simple approach to predict the behavior of friction coefficient in the sliding lubricated point contact. Based on the load-sharing concept, the total applied load is supported by the combination of hydrodynamic film and asperity contact. The asperity contact load is determined in terms of maximum Hertzian pressure in the point contact while the fluid hydrodynamic pressure is calculated through adapting the available numerical solutions of elastohydrodynamic lubrication (EHL) film thickness formula for smooth surfaces. The simulations presented cover the entire lubrication regime including full-film EHL, mixed-lubrication, and boundary-lubrication. The results of friction, when plotted as a function of the sum velocity, result in the familiar Stribeck-type curve. The simulations are verified by comparing the results with published experimental data. A parametric study is conducted to investigate the influence of operating condition on the behavior of friction coefficient. A series of simulations is performed under various operating conditions to explore the behavior of lift-off speed. An equation is proposed to predict the lift-off speed in sliding lubricated point contact, which takes into account the surface roughness.

The Influence of the Operating Conditions on the Lubrication Regimes of Ball Screws

2013 ◽  
Vol 371 ◽  
pp. 581-585
Author(s):  
George Constantin Puiu ◽  
Vasile Puiu
Keyword(s):  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Ball Screw ◽  
Minimum Thickness ◽  
Lubrication Regimes ◽  
Lubrication Regime ◽  
Ball Screw Drive ◽  
Ellipticity Parameter

In point contact related applications (ball bearings, ball-screws) the minimum and the central film thickness of lubricant have a particular importance. The literature presents various numerical solutions to determine these parameters in the case of elliptical contacts [1-4]. Most of them refer to the fully developed elastohydrodynamic lubrication regime (EHD). Hamrock [5] proposes four different lubrication regimes depending on the size and importance of two physical phenomena that occur in contact: elastic deformation of the bodies in contact under a given load and lubricant viscosity variation of contact pressure. These four lubrication regimes have specific relations for calculating the two parameters. Also, Hamrock [5] develops a methodology for identifying the lubrication regime in a point contact, depending on three dimensionless parameters: the ellipticity parameter; the viscosity parameter; the elasticity parameter. According to the viscosity and elasticity parameters, for each value of the ellipticity parameter a map of lubrication regimes can be built. These parameters are influenced by the materials and geometry of the bodies in contact and operating conditions. By using the methodology [5] a comprehensive analysis regarding the lubrication regimes in contacts between balls and races of a ball screw drive has been done. Thus, a complex program to draw lubrication regimes maps, starting from an imposed geometry and from given operating conditions, has been developed. The developed maps have revealed the different lubrication regimes that can occur in contacts between the balls and races on the screw and nut. It was also revealed, for a given type of screw, which are the load and speed limits that allow transition from an isoviscous-rigid regime of lubrication (IVR) / hydrodynamic (HD) to an elastohydrodynamic lubrication regime (EHD). For each lubrication regime, relations were used for calculating the appropriate minimum thickness of lubricant film, hence the major importance of accurate knowledge of lubrication regime.

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