Inlet Shear Heating in Elastohydrodynamic Lubrication

1973 ◽  
Vol 95 (4) ◽  
pp. 417-423 ◽  
Author(s):  
J. A. Greenwood ◽  
J. J. Kauzlarich
Keyword(s):  
Shear Rate ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Temperature Rise ◽  
Thermal Effects ◽  
Elastohydrodynamic Lubrication ◽  
Oil Film ◽  
Comparison With Experiment ◽  
Pure Rolling ◽  
Shear Heating

In EHL, the oil film thickness of rollers is controlled by the rate at which the oil is drawn into the conjunction of the disks by the moving surfaces of the rollers. The theory often assumes isothermal conditions in the inlet although it can be shown that the maximum shear rate often exceeds 106 sec−1, even in pure rolling. A theoretical analysis is presented for the oil temperature rise in the inlet of rollers, and the result is applied to predict the consequent film thickness. It is found that thermal effects on film thickness are only negligible at low rolling speeds. A comparison with experiment supports the conclusion that the thinning of the film thickness below that predicted by isothermal theory is substantially explained by inlet shear heating of the lubricant.

Lubrication state identification of the line contact tribo-pair under a pure rolling condition with ultrasonic method

2021 ◽  
pp. 135065012110337
Author(s):  
Zhihe Duan ◽  
Tonghai Wu
Keyword(s):  
Theoretical Analysis ◽  
Film Thickness ◽  
Ultrasonic Method ◽  
Elastohydrodynamic Lubrication ◽  
Theoretical Models ◽  
Lubrication Theory ◽  
Operating Conditions ◽  
Line Contact ◽  
Oil Film ◽  
Pure Rolling

A line contact tribo-pair is a key mechanism unit in rolling bearings, which is often characterized by ultra-high contact pressure and ultra-thin oil film. Elastohydrodynamic lubrication is often adopted to characterize the lubrication state of such a tribo-pair. As a primary parameter for elastohydrodynamic lubrication, the oil film thickness is often evaluated with simplified theoretical models or complicated measurements. So far, a comprehensive verification of the lubrication states in a real line-contact tribo-pair, however, is rarely reported. Focusing on the roller/ring tribo-pair of a wet-lubricated rolling bearing under pure rolling conditions, this study investigates the lubrication states by integrating multiple theories. Five regions including isoviscous hydrodynamic, piezoviscous hydrodynamic, elastohydrodynamic lubrication, mixture lubrication, and boundary lubrication regions can be identified using the framework. Then, validation experiments are carried out on a line contact tribo-pair test rig under the same operating conditions applied in the theoretical analysis. The oil film thickness is measured by the ultrasonic method. The analysis results demonstrate that only two regions, the elastohydrodynamic lubrication and mixture lubrication regions, can be identified using the experimental data. The identified elastohydrodynamic lubrication and mixture lubrication regions are consistent with theoretical analysis; and the Blok equation and elastohydrodynamic lubrication theory are suggested to calculate the oil film thickness in the elastohydrodynamic lubrication and mixture lubrication regions, respectively. Moreover, the oil film thickness calculated by the Dowson equation is larger than that based on the elastohydrodynamic lubrication theory due to a different viscous pressure equation.

Size effect on thermal elastohydrodynamic lubrication of industrial chain bush-pin hinge pair

2019 ◽  
Vol 71 (9) ◽  
pp. 1080-1085 ◽  
Author(s):  
Mingyu Zhang ◽  
Jing Wang ◽  
Yi Liu ◽  
Longjie Dai ◽  
Zhaohua Shang
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Temperature Rise ◽  
Elastohydrodynamic Lubrication ◽  
Curvature Radius ◽  
Line Contact ◽  
Content Type ◽  
Oil Film ◽  
Industrial Chain ◽  
Infinite Line

Purpose The purpose of this paper is to use elastohydrodynamic lubrication (EHL) theory to study the variation of the equivalent curvature radius “R” on the change of oil film thickness, pressure, temperature rise and friction coefficient in the contact zone between bush-pin in industrial chain drive. Design/methodology/approach In this paper, the contact between bush and pin is simplified as infinitely long line contact. The lubrication state is studied by numerical simulation using steady-state line contact thermal EHL. The two constitutive equations, namely, Newton fluid and Ree–Eyring fluid are used in the calculations. Findings It is found that with the increase of equivalent curvature radius, the thickness of oil film decreases and the temperature rise increases. Under the same condition, the friction coefficient of Newton fluid is higher than that of Ree–Eyring fluid. When the load increases, the oil film thickness decreases, the temperature rise increases and the friction coefficient decreases; and the film thickness increases with the increase of the entraining speed under the condition “R < 1,000 mm”. Research limitations/implications The infinite line contact assumption is only an approximation. For example, the distances between the two inner plates are 5.72 mm, by considering the two parts assembled into the inner plates, the total length of the bush is less than 6 mm. The diameter of the pin and the bore diameter of the bush are 3.28 and 3.33 mm. However, the infinite line contact is also helpful in understanding the general variation of oil film characteristics and provides a reference for the future study of finite line contact of chain problems. Originality/value The change of the equivalent radius R on the variation of the oil film in the contact of the bush and the pin in industrial chain drive was investigated. The size effect influences the lubrication characteristic greatly in the bush-pin pair.

Thermal EHL Analyses of Point Contacts With Surface Roughness

2005 ◽  
Author(s):  
J. Wang ◽  
P. Yang ◽  
M. Kaneta
Keyword(s):  
Surface Roughness ◽  
High Temperature ◽  
Film Thickness ◽  
Temperature Rise ◽  
Point Contacts ◽  
Oil Film ◽  
Sliding Motion ◽  
Pure Rolling ◽  
Thermal Ehl ◽  
High Temperature Rise

The Newtonian thermal EHL analyses of point contacts with two-sided surface roughness have been performed under pure rolling, sliding/rolling and simple sliding conditions. Thermal results are compared with isothermal ones. It has been found that the sliding motion produces high temperature rise and reduces the film thickness greatly. The influence of amplitude and wavelength of the surface roughness on variation of tribo-characteristics of oil film is also discussed.

Elastohydrodynamic Lubrication of a Line Contact

1974 ◽  
Vol 188 (1) ◽  
pp. 221-238 ◽  
Author(s):  
D. G. Wymer ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Central Region ◽  
Glass Plate ◽  
Elastohydrodynamic Lubrication ◽  
Optical Interferometry ◽  
Optical Measurements ◽  
Line Contact ◽  
Electrical Measurements ◽  
Oil Film ◽  
Pure Rolling

In Part 1, optical interferometry is used to study an elastohydrodynamically lubricated line contact between a taper roller and a glass plate under pure rolling conditions. The results give detailed information on film profiles and show the effects of end blending, lubricant starvation, deep scratches and static oil entrapments. In Part 2, oil film thicknesses in an elastohydrodynamic line contact are measured using optical interferometry and compared with theory. Two empirical formulae are derived for film thickness in the central region and at the exit constriction. In addition to the optical measurements, electrical measurements (resistance and capacitance) are made simultaneously, enabling a direct comparison to be made.

Thermal elastohydrodynamic lubrication characteristics and optimisation of the ball-type tripod universal joint

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fuqin Yang ◽  
Xiaojie Han ◽  
Mingqing Si
Keyword(s):  
Elastic Modulus ◽  
Film Thickness ◽  
Temperature Rise ◽  
Elastohydrodynamic Lubrication ◽  
Lubricating Oil ◽  
Universal Joint ◽  
Oil Viscosity ◽  
Content Type ◽  
Oil Film ◽  
Lubrication Characteristics

Purpose This paper aims to study the influence of three-column groove shell radius, ball radius, lubricating oil viscosity and elastic modulus on the thermal elastohydrodynamic lubrication (TEHL) characteristics and optimisation of the ball-type tripod universal joint. Design/methodology/approach The point contact TEHL model of the joint was developed, and the multi-grid method was used to solve it. The influence of three-column groove shell radius, ball radius, lubricating oil viscosity and elastic modulus on the lubrication characteristics was analysed. Further, the optimisation of the joint TEHL performance was carried out by the Kriging approximation model combined with the multi-objective particle swarm optimisation (MOPSO) algorithm. Findings The research results show that increasing groove shell radius and ball radius can effectively increase the oil film thickness, and decrease the oil film pressure, as well as the temperature rise. Decreasing elastic modulus can reduce the oil film temperature rise and pressure, and increasing viscosity can effectively increase the oil film thickness. The optimised minimum oil film thickness increases by 33.23% and the optimised maximum oil film pressure and maximum temperature rise decrease by 11.92% and 28.87%, respectively. Furthermore, the relative error of each response output is less than 10%. Originality/value This study applies TEHL theory to the tribological research of the ball-type tripod universal joint, and the joint’s lubrication performance is improved greatly by the Kriging model and MOPSO algorithm, which provides an effective measure to raise the joint’s working efficiency.

Three-Dimensional Temperature Distribution in EHD Lubrication: Part I—Circular Contact

1992 ◽  
Vol 114 (1) ◽  
pp. 32-41 ◽  
Author(s):  
Kyung Hoon Kim ◽  
Farshid Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Temperature Rise ◽  
Thermal Effects ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Simultaneous System ◽  
Ehd Lubrication ◽  
Energy Equations ◽  
Circular Contact

A complete numerical solution of Newtonian thermal compressible elastohydrodynamic lubrication of rolling/sliding point (circular) contact has been obtained. The multilevel multigrid technique was used to solve the simultaneous system of thermal Reynolds, elasticity and the energy equations with their boundary conditions. The effects of various loads, speeds, and slip conditions on the lubricant temperature, film thickness, and friction force have been investigated. The results indicate that the temperature rise in the contact is significant and thermal effects cannot be neglected.

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.

Influence of Surface Waviness on the Thermal Elastohydrodynamic Lubrication of an Eccentric-Tappet Pair

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
J. Wang ◽  
C. H. Venner ◽  
A. A. Lubrecht
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Surface Waviness ◽  
Film Pressure ◽  
Oil Film ◽  
Working Cycle ◽  
Temperature Oscillations ◽  
Minimum Film Thickness ◽  
Traction Coefficient ◽  
Oil Film Pressure

The effect of single-sided and double-sided harmonic surface waviness on the film thickness, pressure, and temperature oscillations in an elastohydrodynamically lubricated eccentric-tappet pair has been investigated in relation to the eccentricity and the waviness wavelength. The results show that, during one working cycle, the waviness causes significant fluctuations of the oil film, pressure, and temperature, as well as a reduction in minimum film thickness. Smaller wavelength causes more dramatic variations in oil film. The fluctuations of the pressure, film thickness, temperature, and traction coefficient caused by double-sided waviness are nearly the same compared with the single-sided waviness, but the variations are less intense.

scholarly journals Contributions of Molecular Dynamics Simulations to Elastohydrodynamic Lubrication

2021 ◽  
Vol 69 (1) ◽  
Author(s):  
James P. Ewen ◽  
Hugh A. Spikes ◽  
Daniele Dini
Keyword(s):  
Molecular Dynamics ◽  
Shear Rate ◽  
Experimental Design ◽  
Md Simulation ◽  
Elastohydrodynamic Lubrication ◽  
Quantitative Agreement ◽  
Coupling Methods ◽  
Fundamental Understanding ◽  
Shear Heating ◽  
Dynamics Simulations

AbstractThe prediction of friction under elastohydrodynamic lubrication (EHL) conditions remains one of the most important and controversial areas of tribology. This is mostly because the pressure and shear rate conditions inside EHL contacts are particularly severe, which complicates experimental design. Over the last decade, molecular dynamics (MD) simulation has played an increasingly significant role in our fundamental understanding of molecular behaviour under EHL conditions. In recent years, MD simulation has shown quantitative agreement with friction and viscosity results obtained experimentally, meaning that they can, either in isolation or through the use of multiscale coupling methods, begin to be used to test and inform macroscale models for EHL problems. This is particularly useful under conditions that are relevant inside machine components, but are difficult to obtain experimentally without uncontrollable shear heating.

Theoretical and experimental studies of the oil film in lubricated point contact

1966 ◽  
Vol 291 (1427) ◽  
pp. 520-536 ◽  
Keyword(s):  
Surface Layer ◽  
Film Thickness ◽  
Strong Evidence ◽  
Experimental Studies ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Point Contacts ◽  
Previous Theory ◽  
Oil Film

A technique using Newton’s rings for mapping the oil film of lubricated point contacts is described. A theoretical value for the film thickness of such contacts in elastohydrodynamic lubrication is derived. The experimental results give the exit constriction predicted by previous theory but never shown in detail. The comparison of theoretical and experimental oil film thicknesses, which is satisfactorily accurate, gives strong evidence for a viscous surface layer some 1000Å thick. This film agrees with the known ‘lubricating power’ of the various oils tested.

Sign in / Sign up

Export Citation Format

Share Document