scholarly journals Film Thickness Calculations in Elastohydrodynamically Lubricated Circular Contacts, Using a Multigrid Method

1988 ◽  
Vol 110 (3) ◽  
pp. 503-507 ◽  
Author(s):  
A. A. Lubrecht ◽  
C. H. Venner ◽  
W. E. ten Napel ◽  
R. Bosma
Keyword(s):  
Film Thickness ◽  
Multigrid Method ◽  
Point Contact ◽  
Hertzian Contact ◽  
Medium Size ◽  
Fine Grid ◽  
Central Value ◽  
Minimum Film Thickness ◽  
Inlet Zone ◽  
The Cost

Minimum, central and average film thicknesses have been calculated for the isothermal E.H.L. point contact case, for a variety of load, rolling speed, and material parameters. The equations governing this problem were solved using a Multigrid method. This technique offers the possibility to work with a very fine grid, obtaining detailed and accurate solutions, at the cost of moderate cpu times and storage requirements, on medium size computers. Computations for low loads, requiring a large inlet zone, have been carried out using local grid refinements. The fluid in these calculations is assumed to be compressible and its viscosity-pressure behavior is described by either the Roelands equation, or the Barus equation. The ratio between the calculated minimum film thickness and the central value varied with the parameters governing the problem, but for low loads, a value of 3/4 was obtained. The film thickness behavior at these low loads can be accurately described in terms of the minimum film thickness. For higher loads, however, a description based on a film thickness, averaged over the Hertzian contact, is more appropriate to be compared with the asymptotic solution (Ertel, Grubin).

Multigrid, an Alternative Method of Solution for Two-Dimensional Elastohydrodynamically Lubricated Point Contact Calculations

1987 ◽  
Vol 109 (3) ◽  
pp. 437-443 ◽  
Author(s):  
A. A. Lubrecht ◽  
W. E. ten Napel ◽  
R. Bosma
Keyword(s):  
Film Thickness ◽  
Iterative Methods ◽  
Multigrid Method ◽  
Computing Time ◽  
Point Contact ◽  
Two Dimensional ◽  
Point Contacts ◽  
Pressure Profiles ◽  
Minimum Film Thickness ◽  
Method Of Solution

Detailed and accurate film thickness and pressure profiles have been calculated for point contacts at moderate and high loads, using a multigrid method. The influence of the compressibility of the lubricant and of the number of nodal points on the calculated minimum film thickness and maximum spike pressure have been examined. The required computing time is two orders of magnitude less, compared with the calculations using “classical” iterative methods.

Scale Effects in Generalized Newtonian Elastohydrodynamic Films

2008 ◽  
Author(s):  
I. I. Kudish ◽  
P. Kumar ◽  
M. M. Khonsary ◽  
S. Bair
Keyword(s):  
Film Thickness ◽  
Scale Effects ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Viscosity Coefficient ◽  
Shear Thinning ◽  
Effective Pressure ◽  
Practical Advantage ◽  
Inlet Zone ◽  
Real Machine

The prediction of elastohydrodynamic lubrication (EHL) film thickness requires knowledge of the lubricant properties. Today, in many instances, the properties have been obtained from a measurement of the central film thickness in an optical EHL point contact simulator and the assumption of a classical Newtonian film thickness formula. This technique has the practical advantage of using an effective pressure-viscosity coefficient which compensates for shear-thinning. We have shown by a perturbation analysis and by a full EHL numerical solution that the practice of extrapolating from a laboratory scale measurement of film thickness to the film thickness of an operating contact within a real machine may substantially overestimate the film thickness in the real machine if the machine scale is smaller and the lubricant is shear-thinning in the inlet zone.

An Experimental Evaluation of the Hamrock and Dowson Minimum Film Thickness Equation for Fully Flooded EHD Point Contacts

1981 ◽  
Vol 103 (2) ◽  
pp. 284-294 ◽  
Author(s):  
K. A. Koye ◽  
W. O. Winer
Keyword(s):  
Experimental Data ◽  
Statistical Analysis ◽  
Film Thickness ◽  
Experimental Evaluation ◽  
Point Contact ◽  
Major Axis ◽  
Point Contacts ◽  
Lubricant Film Thickness ◽  
Minimum Film Thickness ◽  
Ellipticity Ratio

Fifty-seven measurements of the minimum lubricant film thickness separating the elastohydrodynamically lubricated point contact of a steel crowned roller and a flat sapphire disk were made by an optical interferometry technique. The data collected were used to evaluate the Hamrock and Dowson minimum EHD film thickness model over a practical range of contact ellipticity ratio where the major axis of the contact ellipse is aligned both parallel and perpendicular to the direction of motion. A statistical analysis of the measured film thickness data showed that the experimental data averaged 30 percent greater film thickness than the Hamrock and Dowson model predicts.

Effect of Stiff Coatings on EHL Film Thickness in Point Contacts

2007 ◽  
Author(s):  
Yuchuan Liu ◽  
Q. Jane Wang ◽  
Dong Zhu
Keyword(s):  
Film Thickness ◽  
Working Conditions ◽  
Coating Thickness ◽  
Point Contact ◽  
Thickness Variation ◽  
Point Contacts ◽  
Lubricant Film Thickness ◽  
Wide Range ◽  
Minimum Film Thickness ◽  
Coating Material Properties

This study investigates the influences of coating material properties and coating thickness on lubricant film thickness based on a point-contact isothermal EHL model developed recently by the authors. The results present the trend of minimum film thickness variation as a function of coating thickness and elastic modulus under a wide range of working conditions. Numerical results indicates that the increase in minimum film thickness, Imax, and the corresponding optimal dimensionless coating thickness, H2, can be expressed in the following formulas: Imax=0.766M0.0248R20.0296L0.1379exp(−0.0245ln2L)H2=0.049M0.4557R2−0.1722L0.7611exp(−0.0504ln2M−0.0921ln2L) These formulas can be used to estimate the effect of a coating on EHL film thickness.

On Three-Dimensional Flat-Top Defects Passing Through an EHL Point Contact: A Comparison of Modeling with Experiments

2005 ◽  
Vol 127 (1) ◽  
pp. 51-60 ◽  
Author(s):  
A. Fe´lix-Quin˜onez ◽  
P. Ehret ◽  
J. L. Summers
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Three Dimensional ◽  
Point Contact ◽  
Numerical Results ◽  
Shaped Surface ◽  
Pure Rolling ◽  
Pressure Region ◽  
Inlet Zone ◽  
High Pressure Region

A direct comparison between experimental and numerical results for the passage of an array of 3D flat-top, square shaped surface features through an EHL point contact is presented. Results for pure rolling conditions show that the features’ deformation in the high-pressure region is governed by their ability to entrap lubricant both underneath and in the grooves during their passage through the inlet zone. Film perturbations associated with each defect occur as locally enhanced regions of lubricant and film thickness micro-constrictions. Under sliding conditions the features sustain further deformations as they traverse the high-pressure conjunction and meet the highly viscous lubricant entrapped in the grooves, which moves at a different velocity. Lubricant is also seen to accumulate just in front or behind the features depending on the slide-to-roll ratio. Overall, the results highlight the importance of understanding the effects of the defects structure and the lubricant rheology on the film thickness to unravel the effects of real roughness patterns.

Multigrid, An Alternative Method for Calculating Film Thickness and Pressure Profiles in Elastohydrodynamically Lubricated Line Contacts

1986 ◽  
Vol 108 (4) ◽  
pp. 551-556 ◽  
Author(s):  
A. A. Lubrecht ◽  
W. E. ten Napel ◽  
R. Bosma
Keyword(s):  
Film Thickness ◽  
Multigrid Method ◽  
Computing Time ◽  
Alternative Method ◽  
Pressure Profiles ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Pressure Spike ◽  
Order Of Magnitude

Film thickness and pressure profiles have been calculated for line contacts at moderate and high loads, using a Multigrid method. Influence of the compressibility of the lubricant on the minimum film thickness and on the pressure spike has been examined. The required computing time is an order of magnitude less than when using the previous methods.

scholarly journals Analysis of Starvation Effects on Hydrodynamic Lubrication in Nonconforming Contacts

1982 ◽  
Vol 104 (3) ◽  
pp. 410-417 ◽  
Author(s):  
D. E. Brewe ◽  
B. J. Hamrock
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Three Dimensional ◽  
Point Contact ◽  
Sharp Decrease ◽  
Reduction Factor ◽  
Wide Range ◽  
Minimum Film Thickness ◽  
Contour Plots ◽  
Starvation Effects

Numerical methods were used to determine the effects of lubricant starvation on the minimum film thickness under conditions of a hydrodynamic point contact. Starvation was effected by varying the fluid inlet level. The Reynolds boundary conditions were applied at the cavitation boundary and zero pressure was stipulated at the meniscus or inlet boundary. The analysis is considered valid for a range of speeds and loads for which thermal, piezoviscous, and deformation effects are negligible. It is applied to a wide range of geometries (i.e., from a ball-on-plate configuration to a ball in a conforming groove). Seventy-four cases were used to numerically determine a minimum-film-thickness equation as a function of the ratio of dimensionless load to dimensionless speed for varying degrees of starvation. From this, a film reduction factor was determined as a function of the fluid inlet level. Further, a starved fully flooded boundary was defined and an expression determining the onset of starvation was derived. As the degree of starvation was increased, the minimum film thickness decreased gradually until the fluid inlet level became critical. Reducing the fluid inlet level still further led to a sharp decrease in the minimum film thickness. An expression determining the critically starved fluid inlet level was derived. The changes in the inlet pressure buildup due to changing the available lubricant supply are presented in the form of three-dimensional isometric plots and also in the form of contour plots.

Thermal and Starvation Effects on the Minimum Film Thickness in Inlet Zone in Cold Rolling

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
P. Singh ◽  
R. K. Pandey ◽  
Y. Nath
Keyword(s):  
Film Thickness ◽  
Temperature Rise ◽  
Speed Reduction ◽  
Heating Effects ◽  
Empirical Relations ◽  
Viscous Shear ◽  
Minimum Film Thickness ◽  
Starvation Effects ◽  
Shear Heating ◽  
Inlet Zone

The main objective of this research is to analyze the variation of minimum film thickness in the inlet zone of roll-strip interface by incorporating starvation and viscous shear heating effects at high rolling speeds (5–20m∕s), reduction ratios (0.05–0.20), and slip values (varying up to 20%). An additional objective of this paper is to develop empirical relations for predictions of minimum film thicknesses (both isothermal and thermal) and maximum film temperature rise in the inlet zone of the lubricated roll strip contact as functions of roll-speed, reduction ratio, material parameter, slip, and starvation parameter. An efficient numerical method based on Lobatto quadrature technique is adopted for rigorous analysis of the present problem. The results reveal that the existence of starvation seems to be beneficial in terms of reduction in maximum film temperature rise as well as reduction in quantity of oil required for lubrication provided thin continuous film exists at the contact.

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.

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