Showing papers in "Journal of Tribology-transactions of The Asme in 1989"

Measurements of and Relation Between the Adhesion and Friction of Two Surfaces Separated by Molecularly Thin Liquid Films

Abstract: A new technique is described for sliding (shearing) two molecularly smooth surfaces laterally past each other in liquids while monitoring their exact contact area, the normal and transverse forces, and the surface separation. First, we show that the elastic deformations of two initially curved surfaces in adhesive contact are the same under static and dynamic (i.e., sliding) conditions. Detailed results are then presented of how the shear properties of thin films of water and a simple nonpolar liquid are “quantized” with the number of layers. Results with water as the intervening liquid, as well as the effects of humidity on sliding in air, reveal that more complex mechanisms are operating than with simple liquids which appear to be related to the complex “hydration” forces between two surfaces in water or in aqueous salt solutions. The results suggest a close correlation between the static forces and shear properties of very thin liquid films, and the molecular structure of the liquids confined within such films.

An Average Reynolds Equation for Partial Film Lubrication With a Contact Factor

Abstract: Introduction d'un facteur de contact pour simplifier les calculs dans le cas de l'equation de Reynolds moyennee en lubrification avec film partiel

Equilibrium and Associated Load Distribution in Ball and Roller Bearings Loaded in Five Degrees of Freedom While Neglecting Friction—Part I: General Theory and Application to Ball Bearings

Abstract: Etude de l'equilibre et de la distribution des efforts dans un roulement a billes ou a rouleaux charge avec cinq degres de liberte On neglige le frottement Etude theorique et experimentale

Effects of Lubricant Rheology and Kinematic Conditions on Micro-Elastohydrodynamic Lubrication

Abstract: Influence de la rheologie du lubrifiant et des conditions cinematiques sur la lubrification microelastohydrodynamique

Equilibrium and Associated Load Distribution in Ball and Roller Bearings Loaded in Five Degrees of Freedom While Neglecting Friction—Part II: Application to Roller Bearings and Experimental Verification

Abstract: A new, general and consistent mathematical model of highly modular character is presented for calculation of the equilibrium and associated load distribution in rolling element bearings. The bearings may be loaded and displaced in five degrees of freedom. High speed rolling element loading is considered, internal friction is neglected, the material is assumed linearly elastic and the bearing rings are modelled as rigid except for local contact deformation. Either classical Hertzian contact analysis or modern non-Hertzian contact analysis of sophisticated or approximate character is used as applicable. The bearing stiffness matrix is computed analytically and used internally in the iterative bearing equilibrium calculation; its final values may be used for other purposes such as (rotor) dynamics analysis. In Part I, the general theory and application to ball bearings is presented. In Part II, application of the general theory to roller bearings and an experimental verification are presented.

Simple formulas for performance parameters used in elastohydrodynamically lubricated line contacts

Abstract: Formules simples pour le calcul des caracteristiques des contacts lineaires avec lubrification elastohydrodynamique

Practical limits to the performance of magnetic bearings: peak force, slew rate, and displacement sensitivity

Abstract: Magnetic bearings are subject to performance limits which are quite different from those of conventional bearings. These are due in part to the inherent nonlinearity of the device and in part to its electrical nature. Three important nonideal behaviors are presented: peak force capacity, force slew rate limitation, and sensitivity to rotor motion at large displacements. The problem of identifying the dynamic requirements of a magnetic bearing when used to support a known structure subject to known loads is discussed in the context of these limits. Several simple design tools result from this investigation.

Annular honeycomb seals: test results for leakage and rotordynamic coefficients. Comparisons to labyrinth and smooth configurations

Abstract: Test results are presented for leakage and rotordynamic coefficients for seven honeycomb seals. All seals have the same radius, length, and clearance; however, the cell depths and diameters are varied. Rotordynamic data, which are presented, consist of the direct and cross-coupled stiffness coefficients and the direct damping coefficients. The rotordynamic-coefficient data show a considerable sensitivity to changes in cell dimensions; however, no clear trends are identifiable. Comparisons of test data for the honeycomb seals with labyrinth and smooth annular seals show the honeycomb seal had the best sealing (minimum leakage) performance, followed in order by the labyrinth and smooth seals. For prerotated fluid entering the seal, in the direction of shaft rotation, the honeycomb seal has the best rotordynamic stability followed in order by the labyrinth and smooth. For no prerotation, or fluid prerotation against shaft rotation, the labyrinth seal has the best rotordynamic stability followed in order by the smooth and honeycomb seals.

A Double Scale Analysis Approach of the Reynolds Roughness Comments and Application to the Journal Bearing

Abstract: Analyse asymptotique a double echelle de l'influence de la rugosite de Reynolds. Application aux paliers de glissement

Friction-Induced Thermal Influences in Elastic Contact Between Spherical Asperities

Abstract: Effets thermiques dus au frottement dans le cas du contact entre des asperites spheriques elastiques

Development of a Method for the Prediction of Pressure-Viscosity Coefficients of Lubricating Oils Based on Free-Volume Theory

Abstract: Mise au point d'une methode de calcul des coefficients determinant la relation pression-viscosite des huiles lubrifiantes Utilisation de la theorie du volume libre

Discretization Pressure-Wear Theory for Bodies in Sliding Contact

Abstract: Etude theorique de la pression et de l'usure dans un contact glissant. Methode de discretisation des equations de l'usure

Averaged Reynolds equation extended to gas lubrication possessing surface roughness in the slip flow regime: approximate method and confirmation experiments

Abstract: Calcul approche de l'equation de Reynolds moyennee dans le cas de la lubrification par gaz de surfaces rugueuses en regime d'ecoulement glissant. Verification experimentale

The Solution of the Elrod Algorithm for a Dynamically Loaded Journal Bearing Using Multigrid Techniques

Abstract: A numerical solution to a theoretical model of vapor cavitation in a dynamically loaded journal bearing is developed utilizing a multigrid iteration technique. The method is compared with a noniterative approach in terms of computational time and accuracy. The computational model is based on the Elrod algorithm, a control volume approach to the Reynolds equation which mimics the Jakobsson-Floberg and Olsson cavitation theory. Besides accounting for a moving cavitation boundary and conservation of mass at the boundary, it also conserves mass within the cavitated region via a smeared mass or striated flow extending to both surfaces in the film gap. The mixed nature of the equations (parabolic in the full film zone and hyperbolic in the cavitated zone) coupled with the dynamic aspects of the problem create interesting difficulties for the present solution approach. Emphasis is placed on the methods found to eliminate solution instabilities. Excellent results are obtained for both accuracy and reduction of computational time.

Analyses of the Role of Surface Roughness on Contact Stresses Between Elastic Cylinders With and Without Soft Surface Coating

Abstract: Effets de la rugosite de surface sur les contraintes superficielles dans le contact entre deux cylindres elastiques avec ou sans des revetements en materiau tendre

Compressible Elastohydrodynamic Lubrication of Rough Surfaces

Abstract: Etude de la lubrification elastohydrodynamique dans le cas d'un film compressible et de surfaces rugueuses

Hardness Effect on Three-Body Abrasive Wear Under Fluid Film Lubrication

Abstract: Influence de la durete sur l'usure abrasive. Cas d'un systeme a trois corps avec lubrification par film fluide