Hydrodynamics of Wire-Drum Contact

1987 ◽  
Vol 109 (4) ◽  
pp. 679-683
Author(s):  
A. Magnin ◽  
J. M. Piau ◽  
J. Frene ◽  
D. Bois ◽  
M. Godet
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Analytical Solutions ◽  
Numerical Solutions ◽  
Wire Tension ◽  
Active Pressure ◽  
Tension Level ◽  
Foil Bearing ◽  
Pressure Zone ◽  
Minimum Film Thickness

The hydrodynamics of a wire-drum contact is analyzed using theoretical techniques developed in foil bearing studies. Analytical solutions and numerical solutions are obtained. Results show that: when for a given minimum film thickness the wire tension increases, the pressure arc extent decreases and reaches a minimum for certain wire tension level; the pressure distribution is independent of wire tension for large values of tension; and the active pressure zone depends strongly on film thickness.

An Engineering Approach to Non-Hertzian Contact Elasticity—Part II

2000 ◽  
Vol 123 (3) ◽  
pp. 589-594 ◽  
Author(s):  
Luc Houpert
Keyword(s):  
Pressure Distribution ◽  
Analytical Solutions ◽  
Curve Fitting ◽  
Numerical Solutions ◽  
Companion Paper ◽  
Hertzian Contact ◽  
Line Contact ◽  
Correction Factors ◽  
Analytical Development ◽  
Single Radius

Roller/race misalignment and deformation are used for calculating analytically the pressure distribution along the roller/race contact and the final roller/race load and moment. Use is made of the surface crowns and race undercuts for calculating contact dimensions with their possible truncations at large misalignment or loads. The pressure distribution is not symmetrical when misalignment occurs. This analytical development was possible by using a slicing technique in which the local roller/race geometrical interference was calculated in each slice of the contact. A mix of point and line contact Hertzian solutions developed in a companion paper “Part I” is used for obtaining the final load per slice. The final analytical solutions (load, moment and pressure) are successfully compared to two numerical solutions described briefly. The analytical model has been slightly fine-tuned using correction factors obtained by curve-fitting for matching the results to the numerical ones. In the curve-fitting, the single radius profile and multi-radius profile are distinguished.

Stiffness Effects on the Infinitely Wide Foil Bearing

1967 ◽  
Vol 89 (1) ◽  
pp. 92-97 ◽  
Author(s):  
A. Eshel ◽  
H. G. Elrod
Keyword(s):  
Film Thickness ◽  
Numerical Solutions ◽  
Foil Bearing ◽  
Wrap Angle

Numerical solutions are presented for the film thickness of the infinitely wide, self-acting foil bearing for various values of tape stiffness. The solutions indicate that with increasing stiffness there are: (a) a slow reduction in the nearly uniform clearance prevailing under most of the wrap angle; (b) an increase in the peak of the undulations occurring in the region where the tape leaves the spindle; and (c) virtually no change in the trough of these undulations.

Hydrodynamic Analysis of Hydrostatic Bearings With Runner Misalignment and Pad Damage

2013 ◽  
Author(s):  
Timothy Dimond ◽  
David Barnes
Keyword(s):  
Film Thickness ◽  
Analytical Solutions ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Element Solution ◽  
Flow Loop ◽  
Hydrodynamic Analysis ◽  
Hydrostatic Bearing ◽  
Hydrostatic Bearings ◽  
Minimum Film Thickness

Hydrostatic bearings are used in applications where surface speeds are low, or viscosities are insufficient to develop significant load capacity due to shear flow. They are also used in jacking applications for initial liftoff of rotors under low or no rotation conditions, especially for heavy rotors where significant babbitt damage would otherwise occur. Traditional hydrostatic bearing analyses assume isothermal lubricating flows. Analytical solutions also assume that the pressure in the pocket of the hydrostatic bearing is constant. This assumption is only approximately correct for low and zero operating speeds. Analytical solutions also assume that the runner and pad surfaces are parallel. The analytical solutions are not capable of capturing damage or misalignment effects. This paper describes a hydrodynamic analysis of a hydrostatic thrust bearing. The solution is based on a finite element solution to the generalized Reynolds equation. The finite element solution is applied in both the pocket and pad regions of the hydrostatic bearings. The analysis includes a flow loop balance that considers the effects of pressure losses in the lubricant supply piping, allowing for modeling of saturation effects in bearing load capacity. The flow loop balance for the lubrication supply is coupled with the bearing solution. This allows for pad loads to vary as a function of circumferential position in thrust bearings. The analysis was applied to the operation of a hydrostatic thrust bearing system for the HUSIR radio telescope at the Massachusetts Institute of Technology. Simplified models of pad damage and runner misalignment were considered in the analysis. The minimum film thickness and pressure profile was calculated. Runner misalignment reduced minimum film thickness by up to 80% when compared to a parallel runner under identical loading conditions. Runner damage equivalent to twice the nominal film thickness reduced the minimum film thickness by approximately 10%.

Analysis of elastohydrodynamic lubrication in a novel metal-on-metal hip joint replacement

2002 ◽  
Vol 216 (3) ◽  
pp. 185-193 ◽  
Author(s):  
M Jagatia ◽  
Z M Jin
Keyword(s):  
Finite Element ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Contact Pressure ◽  
Elastohydrodynamic Lubrication ◽  
Metal On Metal ◽  
Minimum Film Thickness ◽  
Acetabular Components ◽  
Cobalt Chrome Alloy ◽  
Cobalt Chrome

Elastohydrodynamic lubrication (EHL) analysis was carried out in this study for a novel metal-on-metal hip prosthesis, which consists of a cobalt-chrome alloy femoral head articulating against a cobalt-chrome alloy acetabular insert connected to a titanium fixation shell through a taper. Finite element models were developed to investigate the effect of the pelvic bone and the load on the predicted contact pressure distribution between the two bearing surfaces under dry conditions. The finite element method was used to develop elasticity models for both the femoral and the acetabular components; it was found that the elastic deformation of the acetabular insert was mainly dependent on the load, rather than the detailed pressure distribution. A modified solution methodology was accordingly developed to couple the elasticity models for both the femoral and the acetabular surfaces with the Reynolds equation and to solve these numerically by the finite difference method. It was found that a load increase from 500 to 2500 N had a negligible effect on the predicted maximum contact pressure and the minimum film thickness, due to the relatively flexible and accommodating structure of the acetabular insert. Furthermore, the predicted minimum film thickness was shown to be significantly greater than the simple estimation based on the assumption of semi-infinite solids (mono-block design) using the Hamrock and Dowson formula. The effects of the viscosity of the lubricant and the radial clearance between the femoral and the acetabular components on the predicted lubricating film thickness were investigated under both in vitro simulator testing and in vivo walking conditions.

The Theory of the Infinitely Wide, Perfectly Flexible, Self-Acting Foil Bearing

1965 ◽  
Vol 87 (4) ◽  
pp. 831-836 ◽  
Author(s):  
A. Eshel ◽  
H. G. Elrod
Keyword(s):  
Differential Equations ◽  
Film Thickness ◽  
Numerical Solutions ◽  
Uniform Thickness ◽  
General Applicability ◽  
Foil Bearing

The differential equations applicable to the film thickness beneath an infinitely wide, perfectly flexible self-acting tape are derived in this paper. Accurate numerical solutions are obtained for the film thickness in both the entrance and exit regions. These solutions have general applicability to situations where the entrance and exit regions are separated by a third region of uniform thickness.

A Simulation of Hydrodynamic Lubrication on Non-Glazed Surfaces under Different Sliding Velocities and Loads

2007 ◽  
Vol 353-358 ◽  
pp. 827-830
Author(s):  
Peng Li ◽  
Jian Li ◽  
Yong Zhen Zhang ◽  
M. Scherge
Keyword(s):  
Wear Resistance ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Hydrodynamic Lubrication ◽  
Maximum Pressure ◽  
Minimum Film Thickness ◽  
Pin On Disk ◽  
Lubrication Conditions

Recent researches have found that surfaces with non-glazed or laser dimpling topography offer improved lubricating efficiency and wear resistance under lubrication conditions over their conventional glazed status. It was carried out in this paper to simulate a pin-on-disk experimental condition and perform hydrodynamic lubrication (HL) calculations for both non-glazed and glazed surfaces under conditions of different sliding velocities and loads with a view of understanding the tribological mechanism and characteristics of non-glazed surfaces. The results showed that the minimum film thickness of non-glazed surfaces, which closed to a typical elasto-hydrodynamic lubrication (EHL) film thickness, was thicker than that of glazed surfaces under the condition of low sliding velocities and small loads. At the same time, a decreased maximum pressure of full-film of non-glazed surfaces demonstrated an even pressure distribution on them.

Elastohydrodynamic Lubrication of Elliptical Contacts for Materials of Low Elastic Modulus I—Fully Flooded Conjunction

1978 ◽  
Vol 100 (2) ◽  
pp. 236-245 ◽  
Author(s):  
Bernard J. Hamrock ◽  
Duncan Dowson
Keyword(s):  
Elastic Modulus ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Low Elastic Modulus ◽  
Minimum Film Thickness ◽  
Contour Plots ◽  
Order Of Magnitude ◽  
Ellipticity Parameter

Our earlier studies of elastohydrodynamic lubrication of conjunctions of elliptical form are applied to the particular and interesting situation exhibited by materials of low elastic modulus. By modifying the procedures we outlined in an earlier publication, the influence of the ellipticity parameter k and the dimensionless speed U, load W, and material G parameters on minimum film thickness for these materials has been investigated. The ellipticity parameter was varied from 1 (a ball-on-plate configuration) to 12 (a configuration approaching a line contact). The dimensionless speed and load parameters were varied by 1 order of magnitude. Seventeen different cases were used to generate the following minimum- and central-film-thickness relations: H˜min=7.43(1−0.85e−0.31k)U0.65W−0.21H˜c=7.32(1−0.72e−0.28k)U0.64W−0.22 Contour plots are presented that illustrate in detail the pressure distribution and film thickness in the conjunction.

Central film thickness in time-varying normal approach of rolling elastohydrodynamically lubricated contacts

2008 ◽  
Vol 222 (7) ◽  
pp. 1271-1280 ◽  
Author(s):  
G E Morales-Espejel
Keyword(s):  
Transport Phenomenon ◽  
Film Thickness ◽  
Analytical Solutions ◽  
Numerical Solutions ◽  
Film Formation ◽  
Time Varying ◽  
Lubricated Contacts ◽  
Wave Transport ◽  
Shape Approximation ◽  
Rigid Body Displacement

The effects of time-varying normal approach on the film formation of rolling elastohydrodynamically lubricated (EHL) contacts are studied by means of an inlet analysis. A modified Ertel—Grubin scheme is used to calculate the variation of central film thickness as a response of time-varying normal approach. The inlet shape approximation from Crook is used to derive simple analytical and semi-analytical solutions for the calculation of central film thickness and inlet pressures for situations of prescribed normal rigid-body displacement or prescribed load variation. The methodology is also adopted to model the pressure and clearance wave transport phenomenon shown earlier only with the use of full numerical solutions.

Predictive tool for frictional performance of piston ring-pack/liner conjunction

2019 ◽  
Vol 13 (3) ◽  
pp. 5513-5527
Author(s):  
J. W. Tee ◽  
S. H. Hamdan ◽  
W. W. F. Chong
Keyword(s):  
Film Thickness ◽  
Mathematical Models ◽  
Piston Ring ◽  
Published Data ◽  
Predictive Tool ◽  
Frictional Losses ◽  
Fundamental Understanding ◽  
Minimum Film Thickness ◽  
Piston Ring Pack ◽  
Ring Pack

Fundamental understanding of piston ring-pack lubrication is essential in reducing engine friction. This is because a substantial portion of engine frictional losses come from piston-ring assembly. Hence, this study investigates the tribological impact of different piston ring profiles towards engine in-cylinder friction. Mathematical models are derived from Reynolds equation by using Reynolds’ boundary conditions to generate the contact pressure distribution along the complete piston ring-pack/liner conjunction. The predicted minimum film thickness is then used to predict the friction generated between the piston ring-pack and the engine cylinder liner. The engine in-cylinder friction is predicted using Greenwood and Williamson’s rough surface contact model. The model considers both the boundary friction and the viscous friction components. These mathematical models are integrated to simulate the total engine in-cylinder friction originating from the studied piston ring-pack for a complete engine cycle. The predicted minimum film thickness and frictional properties from the current models are shown to correlate reasonably with the published data. Hence, the proposed mathematical approach prepares a simplistic platform in predicting frictional losses of piston ring-pack/liner conjunction, allowing for an improved fundamental understanding of the parasitic losses in an internal combustion engine.

Sinusoidal Three-Lobe Bearings—Optimization and Stability Charts

1980 ◽  
Vol 102 (4) ◽  
pp. 416-424 ◽  
Author(s):  
W. E. ten Napel ◽  
R. Bosma
Keyword(s):  
Film Thickness ◽  
Stability Parameters ◽  
Stability Regions ◽  
Damping Coefficients ◽  
Optimum Position ◽  
Minimum Film Thickness ◽  
Stiffness And Damping

In contradistinction to the commonly used segmented three-lobe bearing, another type of bearing, i.e., the sinusoidal three-lobe bearing has been investigated in this paper. The main advantage of this bearing is that it can very easily be manufactured. Special attention has been paid to problems of optimization with regard to minimum film thickness and friction, respectively. Stiffness and damping coefficients have been calculated as well as stability regions and stability parameters. Additionally, the optimum position of the oil grooves has been investigated.

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