Effects of Load, Speed, and Surface Roughness on Sliding EHD Contact Temperatures

1977 ◽  
Vol 99 (2) ◽  
pp. 254-261 ◽  
Author(s):  
H. S. Nagaraj ◽  
D. M. Sanborn ◽  
W. O. Winer
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
High Frequency ◽  
Point Contact ◽  
Temperature Measurements ◽  
Maximum Pressure ◽  
Surface Temperatures ◽  
Ball Surface ◽  
The Relationship ◽  
Frequency Temperature

An infrared technique has been used to determine the effects of load, speed and surface roughness on temperature in a sliding EHD point contact. Ball surface temperatures are reported for sliding speeds of 0.35 to 5.08 m/s at 0.52 to 2.03 GN/m2 maximum pressure with surface roughness in the range 0.01 to 0.38 μm c.1.a. The relationship between asperity interaction, as measured by relocation surface profilimetry and high frequency temperature measurements, and the ratio of film thickness to surface roughness has also been studied.

Relating Surface Roughness to Subsurface Stress

2005 ◽  
Author(s):  
A. Martini ◽  
S. B. Liu ◽  
B. Escoffier ◽  
Q. Wang
Keyword(s):  
Surface Roughness ◽  
Stress Field ◽  
Point Contact ◽  
Surface Characteristics ◽  
Operating Conditions ◽  
Surface Design ◽  
Dry Contact ◽  
Subsurface Stress ◽  
The Relationship ◽  
Machined Surfaces

Understanding and anticipating the effects of surface roughness on subsurface stress in the design phase can help ensure that performance and life requirements are satisfied. The specific approach taken in this work to address the goal of improved surface design is to relate surface characteristics of real, machined surfaces to subsurface stress fields for dry contact. This was done by digitizing machined surfaces, simulating point contact numerically, calculating the corresponding subsurface stress field, and then relating stress results back to the surface. The relationship between surface characteristics and subsurface stress is evaluated using several different approaches including analyses of trends identified through stress field visualization and extraction of statistical data. One such approach revealed a sharp transition between cases in which surface characteristics dominated the stress field and those in which bulk, or global contact effects dominated the stress. This transition point was found to be a function of the contact operating conditions, material properties, and most interestingly, the roughness of the surface.

Numerical Evaluation of Recalling Elasticity due to Surface Roughness by Finite Element Modeling of Human Skin

2019 ◽  
Author(s):  
Tomohisa Yamamoto ◽  
Atsushi Sakuma
Keyword(s):  
Surface Roughness ◽  
Finite Element ◽  
Human Skin ◽  
Tactile Perception ◽  
Maximum Pressure ◽  
Skin Model ◽  
Solid Objects ◽  
Pitch Ratio ◽  
The Relationship ◽  
Maximum Inclination

Abstract Among human sensations, tactile perception has an important role in physics and in living comfortably. It is already known that surface roughness greatly affects the feel of solid objects, but the mechanics of the relationship between feeling and physics, as well as their effects, are difficult to determine. This study, aims to clarify the numerical relationship between elastic tactile perception and surface roughness of a rigid body by designing various products with surfaces comfortable to touch. The finite element method (FEM) has been adopted for this clarification, and a numerical model of human skin with 3 layers, epidermis, dermis, and subcutaneous, has been developed to discuss the mechanical effects of touch movement. This skin model is used to evaluate the distribution of skin deformations during the process of touch movement, and the analysis of the tactile perception is done by discussing the distribution change due to touching objects. The change in distribution of deformation is mainly discussed in terms of pressure under the epidermis, and various patterns of distribution are inspected by changing the diameters and pitch ratio of a uniformly spread ball used as a plain surface. By comparing the relationship between distributions of rigid and elastic surfaces, similar distributions of pressure in the skin model were observed, and the relationships of the distribution are summarized to solve the mechanics of touch feeling. In this summarization, the maximum pressure and the maximum gradient of pressure distribution are adopted as parameters for the analysis. The analysis shows that it is numerically possible to represent the elasticity recalled by the rigid surface from its relationship with the elastic surface when they have the same maximum pressure and maximum inclination of pressure. The importance of maximum inclination of pressure for touch feeling is also shown here.

The Influence of the Roughness Parameters on the EHL Line Contact Using the Free Volume Model

2013 ◽  
Author(s):  
V. D’Agostino ◽  
V. Petrone ◽  
A. Senatore
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Free Volume ◽  
Rough Surfaces ◽  
Random Number Generator ◽  
Elastohydrodynamic Lubrication ◽  
Maximum Pressure ◽  
Line Contact ◽  
Volume Viscosity ◽  
Minimum Film Thickness

A numerical solution of elastohydrodynamic lubrication (EHL) contact between two rough surface cylinders is presented. In the theoretical approach the free-volume viscosity model is used to describe the piezo-viscous behavior of the lubricant in a Newtonian Elastohydrodynamic line contact [1,2]. Random rough surfaces with Gaussian and exponential statistics have been generated using a method outlined by Garcia and Stoll [3], where an uncorrelated distribution of surface points using a random number generator is convolved with a Gaussian filter to achieve correlation. This convolution is most efficiently performed using the discrete Fast Fourier Transform (FFT) algorithm, which in MATLAB is based on the FFTW library [4]. The maximum pressure and average film thickness are studied at different values of RMS, skewness, kurtosis, autocorrelation function and correlation length. Numerical examples show that skewness and kurtosis have a great effect on the parameters of EHD lubrication. Surface roughness, indeed, tends to reduce the minimum film thickness and it produces pressure fluctuations inside the conjunction which tend to increase the maximum stress. In this way the dynamic stress increases and tends to reduce the fatigue life of the components. It can be seen that the pressures developed in the fluid film in the case of rough surfaces fluctuate with the same frequency of the surface roughness. These pressure ripples correspond to the asperity peaks. This indicates that surface roughness causes very high local contact pressures which may lead to local thinning of the film. A significant reduction has been also observed in the minimum film thickness due to surface roughness.

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 Effect of Oil Temperature on Load Capacity and Friction Power Loss in Point Contact Elasto-hydrodynamic Lubrication

2019 ◽  
Vol 22 (3) ◽  
pp. 180-186
Author(s):  
Hassan S Fatehallah ◽  
Zaid S. Hammoudi ◽  
Lutfy Y. Zidane
Keyword(s):  
Film Thickness ◽  
Friction Force ◽  
Coefficient Of Friction ◽  
Hydrodynamic Lubrication ◽  
Load Capacity ◽  
Point Contact ◽  
Fortran Program ◽  
Maximum Pressure ◽  
Force Coefficient ◽  
Friction Power

This study presents a numerical analysis for point contact Elasto-hydrodynamic lubrication EHL. The oils used are (0W-30 and 10W-40) as lubricants. The pressure and film-thickness profiles for point contact EHL are evaluated. The aims of this study are to estimate the effect of oil’s temperature on friction force, coefficient of friction and load carrying capacity. By using FORTRAN program, the Forward-iterative method is used, to solve two dimensional (2D) EHL problem. The viscosity is updating in the solution by using Roeland’s model. After the convergence of pressure is done, the friction force, friction power losses, and friction coefficient are calculated. The temperature used ranges from (-20 to 120 oC). The results showed the film-thickness decreases with the increasing of temperature. Though the maximum pressure is not affected, only the pressure distribution and profile are changed, inlet pressure decreases and the pressure profile tends towards a hertzian (dry contact) one. The friction force and the coefficient of friction decrease with the increasing of temperature.

Temperature Measurements in Sliding Elastohydrodynamic Point Contacts

1974 ◽  
Vol 96 (3) ◽  
pp. 464-469 ◽  
Author(s):  
V. Turchina ◽  
D. M. Sanborn ◽  
W. O. Winer
Keyword(s):  
Film Thickness ◽  
Surface Temperature ◽  
Infrared Radiation ◽  
Point Contact ◽  
Mineral Oil ◽  
Temperature Measurements ◽  
Point Contacts ◽  
Oil Film ◽  
Temperature Distributions ◽  
Minimum Film Thickness

Techniques using the infrared radiation emitted by a sliding EHD point contact to measure oil film and surface temperature are discussed. Temperature distributions in the EHD contact are presented for a naphthenic mineral oil at 1.04 × 109 N/m2 (150,000 psi) Hertz pressure and several sliding velocities. Film temperatures as high as 360 C are reported at locations near the points of minimum film thickness in the contact side lobes.

Surface roughness effects on point contact elastohydrodynamic lubrication in linear rolling guide with fractal surface topographies

2018 ◽  
Vol 70 (4) ◽  
pp. 589-598 ◽  
Author(s):  
Linlin Li ◽  
Jiajun Yang
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Fractal Surface ◽  
Content Type ◽  
Multi Scale ◽  
Surface Topographies ◽  
Scale Characteristics ◽  
Rolling Guide

Purpose The purpose of this paper is to study the effects of surface roughness on the lubrication performances of the linear rolling guide, which provides theoretical guidance for its lubrication design. Design/methodology/approach The two-variable Weierstrass–Mandelbrot function is used to represent the random and multi-scale characteristics of the rough surface topography. The elastohydrodynamic lubrication (EHL) model of contact between the steel ball and raceway is built. The full numerical solutions of the pressure and film thickness are obtained by using the multi-grid technique. Findings The presence of surface roughness can cause the random fluctuations of the pressure and film thickness, and the fluctuations can become more dramatic for the rougher surfaces. It is also found that the film characteristics can be influenced significantly by the working conditions, such as the load, velocity and ambient viscosity of lubricants. Originality/value Characterization of surface topographies regarding EHL problems in the past studies cannot reflect random and multi-scale characteristics. In this paper, the fractal-based method is introduced to analysis of the point-contact micro-EHL. It reveals the mechanism and law of contact lubrication influenced by the fractal surface roughness and enriches the lubrication principle and method of the linear rolling guide.

Thermal EHL of Rough Rolling/Sliding Line Contacts Using a Mixture of Two Fluids at Dynamic Loads

2002 ◽  
Vol 124 (4) ◽  
pp. 709-715 ◽  
Author(s):  
Punit Kumar ◽  
S. C. Jain ◽  
S. Ray
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Dynamic Loading ◽  
Coefficient Of Friction ◽  
Contact Region ◽  
Dynamic Loads ◽  
Maximum Pressure ◽  
Moving Surface ◽  
Line Contacts ◽  
Rough Rolling

The behavior of the thermal elastohydrodynamic lubrication film in rough rolling/sliding line contacts at dynamic loads is investigated numerically. The lubricant is assumed to be a mixture of Newtonian and Ree-Eyring fluids. The results show that the maximum pressure in the contact region undergoes a noteworthy change with time due to dynamic loading and the effect of moving surface roughness. The variation of minimum film thickness and coefficient of friction with the composition of the lubricant is found to be dependent upon the reference viscosity ratio. The superposition of the effects of moving surface roughness and dynamic loading is shown to determine the behavior of time dependent film thickness and coefficient of friction.

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