Thermohydrodynamic Analysis of Submerged Oil Journal Bearings Considering Surface Roughness Effects

1997 ◽  
Vol 119 (1) ◽  
pp. 100-106 ◽  
Author(s):  
J. Ramesh ◽  
B. C. Majumdar ◽  
N. S. Rao
Keyword(s):  
Surface Roughness ◽  
Thermal Effects ◽  
Hydrodynamic Pressure ◽  
Height Distribution ◽  
Asperity Contact ◽  
Roughness Effects ◽  
State Behavior ◽  
Total Load ◽  
Contact Loads ◽  
Effect Of Surface

A theoretical study of a submerged oil journal bearing is made considering surface roughness and thermal effects. The total load-supporting ability under such condition is due to the thermohydrodynamic as well as the asperity contact pressure. The effect of surface roughness and viscosity-temperature dependency on hydrodynamic pressure has been found by solving the average Reynolds equation, energy equation and heat conduction equations simultaneously. The cavitation model of Jacobsson-Floberg has been modified to take the surface roughness effects into consideration. A parametric study of steady-state behavior has been carried out. Finally, the isothermal, thermohydrodynamic, and contact loads for a model bearing have been calculated, assuming the surface height distribution as Gaussian.

Surface Roughness Effects on Circular Cylinders at High Reynolds Numbers

2002 ◽  
Author(s):  
M. Eaddy ◽  
W. H. Melbourne ◽  
J. Sheridan
Keyword(s):  
Surface Roughness ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Flow Induced Vibration ◽  
Roughness Effects ◽  
Vortex Induced Vibration ◽  
Smooth Cylinder ◽  
Lift Forces ◽  
High Reynolds ◽  
Effect Of Surface

The problem of flow-induced vibration has been studied extensively. However, much of this research has focused on the smooth cylinder to gain an understanding of the mechanisms that cause vortex-induced vibration. In this paper results of an investigation of the effect of surface roughness on the cross-wind forces are presented. Measurements of the sectional RMS fluctuating lift forces and the axial correlation of the pressures for Reynolds numbers from 1 × 105 to 1.4 × 106 are given. It was found that surface roughness significantly increased the axial correlation of the pressures to similar values found at high subcritical Reynolds numbers. There was little effect of the surface roughness on the sectional lift forces. The improved correlation of the vortex shedding means rough cylinders will be subject to larger cross-wind forces and an increased possibility of vortex-induced vibration compared to smooth cylinders.

Calculation of Surface Roughness Effects on Air-Riding Seals

2002 ◽  
Author(s):  
C. Guardino ◽  
J. W. Chew ◽  
N. J. Hills
Keyword(s):  
Surface Roughness ◽  
Compressible Flows ◽  
Reynolds Equation ◽  
Incompressible Flows ◽  
Numerical Solutions ◽  
Cfd Analysis ◽  
Roughness Effects ◽  
Stationary Wall ◽  
Comparative Results ◽  
Effect Of Surface

The effects of surface roughness on air-riding seals are investigated here using the Rayleigh-pad as an example. Both incompressible and compressible flows are considered using both CFD analysis and analytical/numerical solutions of the Reynolds equation for various 2D or 3D roughness patterns on the stationary wall. A ‘unit-based’ approach for incompressible flows has also been employed and is shown to be computationally much less expensive than the full-geometry solution. Results are presented showing the effect of surface roughness on the net lift force. The effects of varying the Reynolds number are demonstrated, as well as comparative results for static stiffness.

Calculation of Surface Roughness Effects on Air-Riding Seals

2004 ◽  
Vol 126 (1) ◽  
pp. 75-82 ◽  
Author(s):  
C. Guardino ◽  
J. W. Chew ◽  
N. J. Hills
Keyword(s):  
Surface Roughness ◽  
Compressible Flows ◽  
Reynolds Equation ◽  
Incompressible Flows ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Roughness Effects ◽  
Stationary Wall ◽  
Comparative Results ◽  
Effect Of Surface

The effects of surface roughness on air-riding seals are investigated here using the Rayleigh pad as an example. Both incompressible and compressible flows are considered using both CFD analysis and analytical/numerical solutions of the Reynolds equation for various two-dimensional or three-dimensional roughness patterns on the stationary wall. A “unit-based” approach for incompressible flows has also been employed and is shown to be computationally much less expensive than the full-geometry solution. Results are presented showing the effect of surface roughness on the net lift force. The effects of varying the Reynolds number are demonstrated, as well as comparative results for static stiffness.

Comparison of tribological performance of roller follower and flat follower under mixed elastohydrodynamic lubrication regime

2016 ◽  
Vol 231 (8) ◽  
pp. 986-996 ◽  
Author(s):  
Amir Torabi ◽  
Saleh Akbarzadeh ◽  
Mohammadreza Salimpour
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Numerical Model ◽  
Film Thickness ◽  
Thermal Effects ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Minimum Film Thickness ◽  
Cam Follower ◽  
Key Parameter

In this study, a numerical model is developed to show the performance improvement of a cam–follower mechanism when using a roller type follower compared to the flat-faced follower. Nonconformal geometry besides the thermal effects due to the shearing of the lubricant film results in formation of a thin film in which the asperities contribute in carrying the load. The numerical model is developed in which the geometry, load, speed, lubricant properties, and the surface roughness profile is taken as input and the film thickness and friction coefficient as a function of cam angle are predicted. The asperities are assumed to have elastic, elasto-plastic, and plastic deformation. Simulation results indicated that the thermal effects cannot be neglected. Surface roughness is also a key parameter that affects the pressure distribution, film thickness, and friction coefficient. Finally, asperity and hydrodynamic pressure is reported and the performance of the two mechanisms is compared. Roller follower has a considerable preference in terms of friction coefficient compared to flat-faced follower. The minimum film thickness, however, is slightly larger in the flat follower.

A Study of Vibration in Caliper-Disc Brake Systems With Surface Roughness Effects: Part B — Inclusion of Surface Roughness Effects in the Equations of Motion and Results

2000 ◽  
Author(s):  
Glenn Meinhardt ◽  
Kambiz Farhang ◽  
Jamil Abdo
Keyword(s):  
Surface Roughness ◽  
Equations Of Motion ◽  
Companion Paper ◽  
Brake System ◽  
Disc Brake ◽  
Roughness Effects ◽  
Vibration Model ◽  
Nonlinear Contact ◽  
Effect Of Surface ◽  
Elastic Characteristics

Abstract Vibration of mechanical systems with friction depends on the physical characteristics of the frictional contact. The elastic characteristics are developed in a companion paper, wherein the results show the surface roughness manifested through nonlinear contact stiffnesses. This paper, the second of two companion papers, incorporates the elastic characteristics of contact between the pad surfaces and the rotor in a vibration model of an automotive caliper-disc brake system. The elastic representation of contact, in the form of polynomial functions of the relative pad/rotor displacements, are used to account for the effect of surface roughness on the vibration response of a caliper-disc brake system. The results indicate a range of frequencies due to the roughness induced stiffness nonlinearities.

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.

Surface Roughness Effects in Infinitely Long Porous Journal Bearings

1999 ◽  
Vol 121 (1) ◽  
pp. 139-147 ◽  
Author(s):  
K. Gururajan ◽  
J. Prakash
Keyword(s):  
Surface Roughness ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Rough Surfaces ◽  
Stochastic Theory ◽  
Journal Bearings ◽  
Roughness Effects ◽  
Effect Of Surface

Christensen’s stochastic theory of hydrodynamic lubrication of rough surfaces is used to study the effect of surface roughness in an infinitely long porous journal bearing operating under steady conditions. It is shown that the surface roughness considerably influences the bearing performance; the direction of the influence depends on the roughness type.

Effect of Surface Roughness on Elastohydrodynamic Line Contact

1982 ◽  
Vol 104 (3) ◽  
pp. 401-407 ◽  
Author(s):  
B. C. Majumdar ◽  
B. J. Hamrock
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Strain Analysis ◽  
Elastohydrodynamic Lubrication ◽  
Asperity Contact ◽  
Pressure Dependent Viscosity ◽  
Surface Irregularities ◽  
Dependent Viscosity ◽  
Contact Pressures ◽  
Effect Of Surface

A numerical solution of an elastohydrodynamic lubrication (EHL) contact between two long, rough surface cylinders is obtained. A theoretical solution of pressure distribution, elastohydrodynamic load, and film thickness for given speeds and for lubricants with pressure-dependent viscosity, material properties of cylinders, and surface roughness parameters is made by simultaneous solution of an elasticity equation and the Reynolds equation for two partially lubricated rough surfaces. The pressure due to asperity contact is calculated by assuming a Gaussian distribution of surface irregularities. The elastic deformation is found from hydrodynamic and contact pressures by using plane strain analysis. The effect of surface roughness on EHL loads, speeds, and central film thicknesses is studied. The results indicate that for a constant central film thickness (1) increasing the surface roughness decreases the EHL load and (2) there is little variation in minimum film thickness as the surface roughness is increased.

Random Surface Roughness Effects in Microasperity Lubrication

2005 ◽  
Author(s):  
Prerit Vyas ◽  
Lyndon S. Stephens
Keyword(s):  
Surface Roughness ◽  
Classical Theory ◽  
Experimental Results ◽  
Roughness Effects ◽  
Random Surface ◽  
Pressure Buildup ◽  
Hydrodynamic Bearings ◽  
Parallel Surfaces ◽  
Lubrication Characteristics ◽  
Effect Of Surface

It is well known that the classical theory of lubrication does not predict the existence of a stable hydrodynamic film between two parallel surfaces. Experimental results have shown that the surface roughness (asperities and cavities) helps the pressure buildup between the two surfaces, thus maintaining the load support that keeps the surfaces from collapsing into each other. The effect of surface roughness on lubrication has gained considerable attention since it is widely recognized that surface roughness can alter the solution for pressure and leakage in hydrodynamic bearings from that given by classical theory. The present work investigates the effect of random (stochastic) surface roughness on the lubrication characteristics of a thrust ring engineered with deterministic surface features.

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