A Simplified Model for Calculating Hydrodynamic Lubrication Film Thickness in Elastoplastic Line Contacts

2011 ◽  
Vol 87 (4) ◽  
pp. 707-723
Author(s):  
Yongbin Zhang
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Simplified Model ◽  
Lubrication Film ◽  
Line Contacts

Numerical Analysis for Influence of Plastic and Elastic Deformation of Rough Surfaces on PEHL for Line Contacts

Tribology ◽  
2005 ◽  
Author(s):  
R. J. Niu ◽  
P. Huang
Keyword(s):  
Plastic Deformation ◽  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Paper Analysis ◽  
Line Contact ◽  
Plastic Deformations ◽  
Rolling Contacts ◽  
Line Contacts ◽  
Elastic And Plastic Deformations ◽  
Strain Relationship

In the present paper, analysis of elasto-plasto-hydrodynamic lubrication (PEHL) in the line contact is carried out to investigate the effect of heavily loaded roll-over on the change in profile of indents. The pressure and film thickness profiles are obtained to solve the Reynolds and film thickness equations simultaneously. And, both the elastic and plastic deformations of the contact, featured with an indent, have been considered. A multi-grid numerical algorithm used in EHL of line contacts is modified and then used for the oil lubricated rolling contacts. In the program, stress and plastic deformation of the indent profile are calculated with the hardening plastic stress-strain relationship according to the theories of plasticity when pressure excesses the yield stress. The results, with and without considering plastic deformation, are compared to show the different influences on the pressure and film thickness. Analysis shows that since the plastic deformation will change the surface roughness, it will significantly change the pressure but film thickness.

Uniform Equations in the Inlet and Exit Zones of Heavily Loaded Point and Line Elastohydrodynamically Lubricated Contacts Involved in Various Steady Motions

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Ilya I. Kudish
Keyword(s):  
Film Thickness ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
Lubrication Film ◽  
Lubricated Contacts ◽  
Asymptotic Equations ◽  
Line Contacts ◽  
Steady Motions ◽  
Numerical Approaches

Heavily loaded point elastohydrodynamically lubricated (EHL) contacts involved in steady purely transitional, skewed transitional, and transitional with spinning motions are considered. It is shown that in the central parts of the inlet and exit zones of such heavily loaded point EHL contacts the asymptotic equations governing the EHL problem along the lubricant flow streamlines for the above types of contact motions can be reduced to two sets of asymptotic equations: one in the inlet and one in the exit zones. The latter sets of equations are identical to the asymptotic equations describing lubrication process in the inlet and exit zones of the corresponding heavily loaded line EHL contact (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC). For each specific motion of a point contact, a separate set of formulas for the lubrication film thickness is obtained. For different types of contact motions, these film thickness formulas differ significantly (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC). For heavily loaded contacts, the discovered relationship between point and line EHL problems allows to apply to point contacts most of the results obtained for line contacts (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC; Kudish, I. I., and Covitch, M. J., 2010, Modeling and Analytical Methods in Tribology, Chapman and Hall/CRC).

Uniform Equations in the Inlet and Exit Zones of Heavily Loaded Point EHL Contacts Involved in Various Steady Motions

2014 ◽  
Author(s):  
Ilya I. Kudish
Keyword(s):  
Film Thickness ◽  
Point Contact ◽  
Point Contacts ◽  
Lubrication Film ◽  
Asymptotic Equations ◽  
Lubricant Flow ◽  
Different Types ◽  
Line Contacts ◽  
Steady Motions ◽  
Ehl Contact

Heavily loaded point EHL contacts involved in steady purely transitional, skewed transitional, and transitional with spinning motions are considered. It is shown that in the central parts of the inlet and exit zones of such heavily loaded point EHL contacts the asymptotic equations governing the EHL problem along the lubricant flow streamlines for the above types of contact motions can be reduced to two sets of asymptotic equations: one in the inlet and one the exit zones. The latter sets of equations are identical to the asymptotic equations describing lubrication process in the inlet and exit zones of the corresponding heavily loaded line EHL contact [1]. For each specific motion of a point contact a separate set of formulas for the lubrication film thickness is obtained. For different types of contact motions these film thickness formulas differ significantly [1]. For heavily loaded contacts the discovered relationship between point and line EHL problems allow to apply to point contacts most of the results obtained for line contacts [1,2].

Modeling of Line Contacts With Degrading Lubricant

2003 ◽  
Vol 125 (3) ◽  
pp. 513-522 ◽  
Author(s):  
Ilya I. Kudish ◽  
Ruben G. Airapetyan
Keyword(s):  
Kinetic Equation ◽  
Film Thickness ◽  
Linear Structure ◽  
Degradation Process ◽  
Polymer Additive ◽  
Polymer Molecules ◽  
Lubrication Film ◽  
Line Contacts ◽  
Contact Surfaces ◽  
Lubricant Viscosity

A plane isothermal elastohydrodynamic problem for a lubricated line contact is studied. The lubricant represented by a base stock with some polymer additive undergoes stress-induced degradation due to scission of polymer additive molecules. The polymer molecules have linear structure. The degradation process of a polymer additive dissolved in a lubricant while the lubricant passes through the contact is described by a kinetic equation. The kinetic equation is solved along the lubricant flow streamlines. The solution of the kinetic equation predicts the density of the probabilistic distribution of the polymer molecular weight versus polymer molecule chain length. The changes in the distribution of polymer molecules affect local lubricant properties. In particular, the lubricant viscosity changes as polymer molecules undergo scission. These irreversible changes in the lubricant viscosity alter virtually all parameters of the lubricated contact such as film thickness, frictional stresses and pressure. As a result of the polymer additive degradation the lubricant experiences a significant viscosity loss. The viscosity loss (up to 60 percent), in turn, leads to a noticeable reduction in the lubrication film thickness (up to 12 percent) and frictional stresses applied to contact surfaces in comparison with the case of a nondegrading lubricant. Moreover, the pressure distribution in degrading lubricants exhibits extremely sharp spikes of about 2.15 to 2.82 (depending on the slide-to-roll ratio) times greater than the maximum Hertzian pressure. That may lead to noticeable variations in fatigue life of the contact surfaces.

Elastohydrodynamic Lubrication Design of Planetary Gear Transmission

2011 ◽  
Vol 228-229 ◽  
pp. 681-685
Author(s):  
Pei De Bao ◽  
Jun Xie ◽  
Xiao Qin Yin ◽  
Qi Zhi Yang ◽  
Lu Zhong Ma
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Elastohydrodynamic Lubrication ◽  
Planetary Gear ◽  
Gear Transmission ◽  
The Sun ◽  
Oil Film ◽  
Lubrication Film ◽  
Planet Gear ◽  
The Many

Based on elastic hydrodynamic lubrication (EHL) theory, an EHL model of the meshing between the sun gear and planet gear in planetary gear transmission was established. The EHL oil film thicknesses at meshing areas and those distributions for two operation cases were calculated: one case with the sun gear as the driving gear and another case with the ring gear as the driving gear. The Lubrication with second case was worse. Through the many comparing calculations the lubrication film thickness can be significantly increased by right parameter design. Reasonable raise of lubricant viscosity can get better gear lubrication. Increased gear pressure angle can greatly increase the oil film thickness. The increase of oil film thickness can improve the lubrication of gears and prevent wearing and reduce the production cost of gears, which have great practical value.

scholarly journals The Effect of Lubrication on the Vibration of Roller Bearings

2018 ◽  
Vol 217 ◽  
pp. 01004
Author(s):  
N.F.M. Yusof ◽  
Z.M. Ripin
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Roller Bearing ◽  
Rolling Bearing ◽  
Vibration Level ◽  
Surface Degradation ◽  
Lubrication Film ◽  
Roller Bearings ◽  
High Level

Proper lubrication is crucial to ensure smooth operation in machineries. In rolling bearing, the improper lubrication may induce high friction and vibration level due to metal to metal contact between the rolling elements. In this study, the roller bearings with and without lubrication are investigated. the natural surface degradation of the roller bearing is monitored and the surface roughness is measured for the lubricant film thickness calculation. the film thickness is determined by the Hamrock-Dowson equation which showed that the grease lubricated bearing operated under the elastro-hydrodynamic lubrication, with the ratio of lubrication film thickness to the surface roughness of λ in the range of 0.9 to 3.65. the un-lubricated bearing was damaged after 20 minutes whereas the grease lubricated bearing continued to operate for 6600 minutes. the observation under microscope showed that the surface underwent smoothening process where the surface roughness decreases initially (running-in state) followed by roughening at the steady state where the surface roughness increases. At damage, the value of λ = 0.9 can be associated with the high level of the bearing vibration. the increase of vibration level becomes rapid at the critical value of λ = 1.6. As such the overall vibration level of the bearing can be related to the surface degradation and low film thickness.

Simple Formulas for Performance Parameters Used in Elastohydrodynamically Lubricated Line Contacts

1989 ◽  
Vol 111 (2) ◽  
pp. 246-251 ◽  
Author(s):  
Ping Pan ◽  
B. J. Hamrock
Keyword(s):  
Film Thickness ◽  
Curve Fitting ◽  
Center Of Pressure ◽  
Operating Parameters ◽  
Performance Parameters ◽  
Practical Applications ◽  
Line Contacts ◽  
Pressure Spike

The film thickness and pressure in elastohydrodynamically lubricated conjunctions have been evaluated numerically for a rather complete range of operating parameters (dimensionless load, speed, and materials parameters) normally experienced in practical applications. From the film thickness and pressure throughout the conjunction a number of performance parameters were evaluated. By curve fitting the data, formulas were obtained that allow easy evaluation of the amplitude and location of the pressure spike, the minimum and central film thicknesses, the value of ρeHe, and the center of pressure.

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