A Thermal Reynolds Equation and Its Application in the Analysis of Plasto-Hydrodynamic Inlet Zones

1974 ◽  
Vol 96 (4) ◽  
pp. 572-577 ◽  
Author(s):  
W. R. D. Wilson ◽  
S. M. Mahdavian
Keyword(s):  
Energy Dissipation ◽  
Film Thickness ◽  
Reynolds Equation ◽  
Wire Drawing ◽  
Lubricant Film ◽  
Pressure Gradients ◽  
Lubricant Film Thickness ◽  
Strip Rolling ◽  
Deformation Processes ◽  
Lubricated Contact

An equation which is equivalent to the steady, one-dimensional incompressible Reynolds equation but which takes account of viscosity variations across the lubricant film thickness due to energy dissipation within the film is developed. It indicates that the pressure gradients developed in a lubricated contact are reduced by the influence of energy dissipation. The use of the equation is illustrated by applying it in the analysis of the inlet zones of continuous deformation processes such as strip rolling and strip and wire drawing. The analysis indicates that thermal effects play an important role in deciding the lubricant film thickness in such contacts.

Pressure Distribution Within EHD Point Contacts Based on Measured Film Thickness

Tribology ◽  
2006 ◽  
Author(s):  
Radek Poliscuk ◽  
Michal Vaverka ◽  
Martin Vrbka ◽  
Ivan Krupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
Pressure Distribution ◽  
Elastic Deformation ◽  
Contact Fatigue ◽  
Lubricant Film ◽  
Rolling Contact ◽  
Lubricant Film Thickness ◽  
Machine Elements ◽  
Lubricated Contact

Surface topography significantly influences the behavior of lubricated contacts between highly loaded machine elements. Most oil- or grease- lubricated machine elements such as gears, rolling bearings, cams and traction drives operate in mixed lubrication conditions and the lubricant film thickness is directly related to the main practical performance parameters such as function, wear, contact fatigue and scuffing. For determination wear and especially contact fatigue, the values and distribution of the pressure in rolling contact are required. The theoretical studies usually involve the numerical solution of pressure and film thickness in the contact, using some physical mathematical model built around the Reynolds equation to describe the flow and the theory of elastic deformation of semi-infinite bodies. Such calculations can be extremely time consuming, especially when lubricant films are very thin and/or contact load very high. This study is aimed at obtaining pressure distribution within lubricated contact from measured film thickness. Lubricant film thickness distribution within the whole concentrated contact is evaluated from chromatic interferograms by thin film colorimetric interferometry. Consequently, an elastic deformation is separated from the film thickness, geometry and mutual approach of the surfaces. Calculation of the pressure distribution is based on inverse elasticity theory. EHD lubricated contact with smooth surfaces of solids was first investigated. Calculated pressure, distributions were compared with data obtained from full numerical solution to check the accuracy. The approach was also applied to surfaces with dents and their influence on distribution of pressure in lubricant film.

Study of Scale Effect in a Starved Elastohydrodynamically Lubricated Contact

2016 ◽  
Vol 821 ◽  
pp. 138-143
Author(s):  
Petr Svoboda ◽  
David Kostal ◽  
Ivan Křupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Scale Effect ◽  
Thickness Measurement ◽  
Lubricant Film ◽  
Scale Model ◽  
Lubricant Film Thickness ◽  
Film Distribution ◽  
Multiple Contacts ◽  
Optical Test ◽  
Lubricated Contact

The article describes an experimental investigation of scale effect in a starved elastohydrodynamically lubricated contact on lubricant film thickness. Lubricant film thickness and its distribution is one of the most important parameters determining the performance and life of machine parts. Current experimental and numerical studies are mostly connected with oil lubrication. However, greases are used in more than 80 % of all rolling bearings where the starvation phenomenon occurs most frequently. The aim of this work is to compare two approaches to measuring film thickness of different greases. The use of multiple contacts optical test rig based on thin film colorimetric interferometry for film thickness measurement has enables to obtain film thickness of starved contact and the film distribution. The experimental observation of full-scale model of bearing will help to understand better the behavior of real bearing. The evaluation of the experiment was made by chromatic interferometry. This method is used to measure thin lubrication films.

The Effect of Porosity of Articular Cartilage on the Lubrication of a Normal Human Hip Joint

1992 ◽  
Vol 206 (3) ◽  
pp. 117-124 ◽  
Author(s):  
Z M Jin ◽  
D Dowson ◽  
J Fisher
Keyword(s):  
Articular Cartilage ◽  
Synovial Fluid ◽  
Film Thickness ◽  
Hip Joint ◽  
Elastic Material ◽  
Single Phase ◽  
Reynolds Equation ◽  
Lubricant Film ◽  
Lubricant Film Thickness ◽  
Normal Human

The effect of porosity of articular cartilage on the lubrication of a normal human hip joint has been studied. The poroelasticity equation of articular cartilage and the modified Reynolds equation for the synovial fluid lubricant have been successfully solved under squeezefilm motion and for the conditions experienced in a normal human hip joint. It has been shown that porosity of the articular cartilage depletes the lubricant film thickness, rather than increasing it, particularly when the lubricant film thickness becomes small. Furthermore, it has been shown that articular cartilage can be treated as a single-phase incompressible elastic material in the lubrication modelling under physiological walking conditions.

Analysis of Thermal Effects in the Yield Phase of Hydrodynamic Lubricant Film in Plane Strain Forging

1996 ◽  
Vol 118 (4) ◽  
pp. 880-885 ◽  
Author(s):  
V. K. Bhatt ◽  
D. K. Sengupta
Keyword(s):  
Film Thickness ◽  
Plane Strain ◽  
Peclet Number ◽  
Film Formation ◽  
Dominant Role ◽  
Lubricant Film ◽  
Pressure Gradients ◽  
Lubricant Film Thickness ◽  
Péclet Number ◽  
Shear Energy

A thermal Reynolds equation, which takes into account viscosity variation across the lubricant film thickness due to shear energy dissipation within the film, has been developed. It also takes into account the effect of conduction and convection on heat transfer in the lubricant film. It indicates that the pressure gradients developed in a no-slip lubricated contact are increased with an increase in Peclet number. The use of the equation is illustrated by applying it in the film formation process in the yield phase of liquid lubricated plane strain forging. The analysis indicates that the Peclet number plays a dominant role infixing the lubricant film thickness in such contacts.

Ultrasonic Measurement of Rolling Bearing Lubrication Using Piezoelectric Thin Films

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Bruce W. Drinkwater ◽  
Jie Zhang ◽  
Katherine J. Kirk ◽  
Jocelyn Elgoyhen ◽  
Rob S. Dwyer-Joyce
Keyword(s):  
Film Thickness ◽  
High Frequency ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Rolling Element Bearing ◽  
Lubricant Layer ◽  
Lubricant Film Thickness ◽  
Oil Film ◽  
Deep Groove ◽  
Lubricated Contact

This paper describes the measurement of lubricant-film thickness in a rolling element bearing using a piezoelectric thin film transducer to excite and receive ultrasonic signals. High frequency (200 MHz) ultrasound is generated using a piezoelectric aluminum nitride film deposited in the form of a very thin layer onto the outer bearing raceway. This creates a transducer and electrode combination of total thickness of less than 10 μm. In this way the bearing is instrumented with minimal disruption to the housing geometry and the oil-film can be measured noninvasively. The high frequency transducer generates a fine columnar beam of ultrasound that has dimensions less than the typical lubricated contact ellipse. The reflection coefficient from the lubricant-layer is then measured from within the lubricated contact and the oil-film thickness extracted via a quasistatic spring model. The results are described on a deep groove 6016 ball bearing supporting an 80 mm shaft under normal operating conditions. Good agreement is shown over a range of loads and speeds with lubricant-film thickness extracted from elastohydrodynamic lubrication theory.

A Thermal Elastohydrodynamic Inlet Zone Analysis

1975 ◽  
Vol 97 (2) ◽  
pp. 212-216 ◽  
Author(s):  
L. E. Murch ◽  
W. R. D. Wilson
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Substantial Reduction ◽  
Lubricant Film ◽  
Simple Equation ◽  
Viscous Heating ◽  
Style Analysis ◽  
Lubricant Film Thickness ◽  
Lubricated Contacts ◽  
Inlet Zone

An equation which takes account of the effects of viscous heating is used in place of the conventional Reynolds equation in a Grubin style analysis of the elastohydrodynamic inlet zone. The analysis indicates that viscous heating in the inlet zone can result in substantial reduction in the lubricant film thickness. The results of the analysis are expressed in a simple equation which will be useful for the design of elastohydrodynamically lubricated contacts under conditions where viscous heating is important.

Study of Direct Measuring of Lubricant Condition in Rolling Element Bearings With Microcomputer Technique

1990 ◽  
Vol 112 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Dongchu Zhao
Keyword(s):  
Film Thickness ◽  
Strain Gage ◽  
Lubricant Film ◽  
Rolling Element Bearings ◽  
Main Program ◽  
Test Apparatus ◽  
Lubricant Film Thickness ◽  
Rolling Element ◽  
Lubricant Films ◽  
Flow Charts

A method for measuring the lubricant condition with strain gage in rolling element bearings and the instrument used are introduced. In order to illustrate the method and the instrument, the theory of measuring lubricant films in rolling element bearings using strain technique, test apparatus, microcomputer hardware as well as software, flow charts for the main program and subprograms, are first described in detail. In addition, the lubricant film thickness is measured for several different lubricants and results are compared with theoretical ones. It is demonstrated that using the method and the instrument introduced in this paper, one can measure the lubricant condition inside bearings very accurately.

Hydrodynamic Model for Cold Strip Rolling

1967 ◽  
Vol 182 (1) ◽  
pp. 153-162 ◽  
Author(s):  
D. S. Bedi ◽  
M. J. Hillier
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Entropy Production ◽  
Coefficient Of Friction ◽  
Hydrodynamic Model ◽  
Reynolds Equation ◽  
Viscous Friction ◽  
Strip Rolling ◽  
Roll Pressure ◽  
Cold Strip Rolling

The theory of rolling is modified to allow calculation of a hydrodynamic film thickness and viscous friction coefficient using Reynolds equation for the lubricant. Calculations are made for the case where the fluid film covers the arc of contact. The film thickness is assumed uniform and is determined by the principle of minimum rate of entropy production. It is shown that the apparent coefficient of friction varies significantly over the arc of contact. At small reductions the roll load tends to decrease with speed of rolling, while at high reductions the load tends to increase. The point of maximum roll pressure does not coincide with the neutral plane; and under certain rolling conditions there may be no maximum in the pressure over the arc of contact.

Sign in / Sign up

Export Citation Format

Share Document