Showing papers in "Journal of Lubrication Technology in 1983"
TL;DR: In this article, it was shown that squeeze film damping cutoff frequencies can be computed directly from the lowest eigenvalue of the Helmholtz equation, and a kinematic mode was proposed and analyzed for the computation of those frequencies.
Abstract: It is shown that squeeze film damping cutoff frequencies can be computed directly from the lowest eigenvalue of the Helmholtz equation. A kinematic mode is proposed and analyzed for the computation of those frequencies and it is demonstrated that Griffin’s calculations may underestimate considerably those frequencies. New results are given for the squeeze film behavior between rectangular plates, annuli which are not necessarily thin and plate sectors.
348 citations
TL;DR: The authors evaluate caracteristiques de fonctionnement d'un palier a gaz utilisant comme surface portante une feuille metallique souple supportee par un systeme elastique.
Abstract: Evaluation des caracteristiques de fonctionnement d'un palier a gaz utilisant comme surface portante une feuille metallique souple supportee par un systeme elastique. Analyse donnant l'influence des differentes variables de construction et de fonctionnement sur le comportement du palier, les solutions etant presentees sous forme de graphiques ou de tableaux. Caracteristiques de conception souhaitables quant au depart de l'arc, au choix de l'angle de charge, au nombre de patins, et au degre de souplesse
316 citations
287 citations
TL;DR: In this paper, the experimental investigation discussed here gives experimental confirmation of the slip-flow theory for modeling hydrodynamic gas bearings with clearances below 0.25 microns, and the effects of molecular rarefaction are studied by operating the slider bearing in different gas media of different mean free paths.
Abstract: : The experimental investigation discussed here gives experimental confirmation of the slip-flow theory for modeling hydrodynamic gas bearings with clearances below 025 microns An interferometric technique employing two CW lasers is used to measure the small clearances with an accuracy of 0025 microns The effects of molecular rarefaction are studied by operating the slider bearing in different gas media of different mean free paths Bearings operating at extremely high local Knudsen numbers are studied without approaching excessively high bearing numbers Experimentally measured trailing edge clearances and pitch angles are compared with theoretical predictions using the modified Reynolds equation with velocity slip boundary conditions Excellent agreement between experiment and theory is found for clearances as high as 160 microns to as low as 0075 microns with corresponding ambient Knudsen numbers of 004 and 251, respectively
274 citations
TL;DR: In this article, the authors discuss thermohydrodynamique theorique and experimental d'un palier de longueur finie, l'analyse tenant compte du transfert de chaleur entre le film, L'arbre, le manchon, la cavitation, la recirculation du lubrifiant, and the recurrence du lube.
Abstract: Etude du probleme thermohydrodynamique theorique et experimental d'un palier de longueur finie, l'analyse tenant compte du transfert de chaleur entre le film, l'arbre, le manchon, la cavitation, la recirculation du lubrifiant etant prise en consideration. Mesure de la distribution de pression et de temperature le long de la paroi du palier ainsi que du rapport d'excentricite et du debit pour differentes vitesses et differentes charges. Bon accord entre resultats experimentaux et theoriques
221 citations
TL;DR: Extension and generalisation du modele d'ecoulement moyen de Patir et Cheng pour lobtention d'une equation de Reynolds moyenne en presence of a rugosite de surface bidimensionnelle.
Abstract: Extension et generalisation du modele d'ecoulement moyen de Patir et Cheng pour l'obtention d'une equation de Reynolds moyenne en presence d'une rugosite de surface bidimensionnelle. Calcul des valeurs des facteurs d'ecoulement apparaissant dans le formalisme au moyen d'un developpement de perturbation de la pression dans un film parallele nominal. Accord des resultats de perturbation avec les resultats d'une simulation numerique recente jusqu'a ce que le contact de surface devienne important les deux approches devenant inadequates a ce moment-la. Mise en evidence de la dependance des facteurs d'ecoulement des parametres de rugosite sous une forme explicite simple
188 citations
TL;DR: In this paper, a forme legerement modifiee de l'equation de Reynolds is presented for un fonctionnement portant sur un certain domaine de L/D and des exposants rheologiques.
Abstract: Etude ayant pour but l'obtention d'equations de lubrification adaptees aux fluides a propriete constante ayant des caracteristiques non Newtoniennes non elastiques. Analyse donnant une forme legerement modifiee de l'equation de Reynolds. Presentation de resultats pour un fonctionnement portant sur un certain domaine de L/D et des exposants rheologiques
157 citations
156 citations
TL;DR: In this article, the authors derived dynamic coefficients for high pressure annular seals typical of neck-ring and interstage seals employed in multistage centrifugal pumps, and compared the stiffness, damping, and inertia coefficients derived herein based on Hirs' model and previously published results based on other models.
Abstract: Expressions are derived which define dynamic coefficients for high-pressure annular seals typical of neck-ring and interstage seals employed in multistage centrifugal pumps. Completely developed turbulent flow is assumed in both the circumferential and axial directions, and is modeled in this analysis by Hirs' turbulent lubrication equations. Linear zeroth and first-order 'short-bearing' perturbation solutions are developed by an expansion in the eccentricity ratio. The influence of inlet swirl is accounted for in the development of the circumferential flow field. Comparisons are made between the stiffness, damping, and inertia coefficients derived herein based on Hirs' model and previously published results based on other models. Finally, numerical results are presented for interstage seals in the Space Shuttle Main Engine High Pressure Fuel Turbopump and a water pump.
145 citations
TL;DR: In this paper, a finite-length solution procedure is developed for perturbation equations which are based on Hirs' (1973) turbulent lubrication model and apply to small motions about a centered position.
Abstract: A finite-length solution procedure is developed for perturbation equations which are based on Hirs' (1973) turbulent lubrication model. The equations apply to small motions about a centered position and include the influence of swirl and changes in Reynolds number due to perturbations in clearances. Numerical results are presented for a range of L/D ratios, with and without swirl. For zero swirl, changes in the L/D ratios show results which are similar to those obtained by Black and Jenssen (1970), but when L/D = 1, differences of about 15 percent appear. The results including swirl give physically insupportable results at small L/D ratios, such as a negative cross-coupled stiffness coefficient at L/D = 0.2. This result demonstrates that the complete Hirs turbulence model is not suitable for short seals with significant swirling flow.
131 citations
TL;DR: In this article, the effect of bearing wear on turbine bearing lubrication at low operating speeds has been investigated by conducting site visits to inspect used bearings during overhaul disassemblies, by interviewing the turbine manufacturers and technical personnel at selected utilities, and by performing an analysis of the effect on bearing wear.
Abstract: The subject of wear of steam turbine bearings at low operating speeds was addressed by conducting site visits to inspect used bearings during overhaul disassemblies, by interviewing the turbine manufacturers and technical personnel at selected utilities, and by performing an analysis of the effect of bearing wear on lubrication at low operating speeds. There is a general lack of understanding of the mechanisms of bearing wear, but there is universal agreement that maintaining proper alignment and minimizing debris in the lubricant are critical to obtaining long bearing life. Wear problems definitely exist, but there is a variation in level of concern regarding these problems. Lift pumps systems on turbines using a low turning gear speed were not found to eliminate bearing wear. Many of the wide variations in bearing design philosophies regarding bearing wear appear to be related to the need for reliable wear-related design data. An analysis of lubrication at low speeds has shown that a limited amount of bearing wear may enhance bearing lubrication and that an optimum in the extent of this wear may exist. Experimental data are needed to develop an understanding of bearing wear mechanisms and bearing operation at low speeds.
TL;DR: In this paper, the effects of particle size and concentration of (CF)n, and a suspending agent AD-6 on the friction and wear process were discussed, and it was found that when a large number of particles can penetrate into the interface in accordance with an oil flow, they show a good performance as a lubricant but solid lubricant films were not formed on worn surfaces besides graphite particles embedded on those of a copper disk.
Abstract: Lubricating properties of machine oils containing such solid lubricants as (CF)n, MoS2, graphite, etc., were studied on a pin and disk machine by measuring an electric contact resistance and a friction force. After lubrication tests, solid lubricants films and transferred wear particles on worn surfaces have been observed by means of an XMA and an optical microscope. The wear mechanism of metals was analyzed considering a mean peak to peak distance and a mean depth of scratches on worn surfaces. The effects of particle size and concentration of (CF)n, and a suspending agent AD-6 on the friction and wear process were also discussed. It was found that when the large number of (CF)n particles can penetrate into the interface in accordance with an oil flow, they show a good performance as a lubricant but solid lubricant films were not formed on worn surfaces besides graphite particles embedded on those of a copper disk.
TL;DR: In this article, a simplified version of the classical Hertzian solution for local stress and deformation of two elastic bodies in contact is presented, which employs simplified forms for the ellipticity and for the complete elliptic integrals of the first and second kinds as a function of the geometry.
Abstract: A shortcut is presented to the classical Hertzian solution for local stress and deformation of two elastic bodies in contact, which employs simplified forms for the ellipticity and for the complete elliptic integrals of the first and second kinds as a function of the geometry. Unlike previously proposed simplified formulas whose range of applicability was limited to ellipticities equal to, or greater than one, the present method extends the range of validity to include ellipticities less than one; in which the semimajor axis in the elliptical contact lies in a direction parallel to the rolling, rather than being perpendicular, as in previous studies. An auxiliary shear stress parameter is also expressed in simplified form as a function of the geometry, permitting a shortcut calculation to be made for the location and magnitude of the maximum subsurface shear stress.
TL;DR: In this paper, a numerical solution to the elastohydrodynamic lubrication (EHL) problem is presented for a cylindrical roller with axially profiled ends, rolling over a flat plane.
Abstract: In this paper, a numerical solution to the elastohydrodynamic lubrication (EHL) problem is presented for a cylindrical roller with axially profiled ends, rolling over a flat plane. Convergence was obtained for moderate load and material parameters (glass, steel, and a mineral oil). Isobars, contours, and section graphs, show pressure variation and film shape. Predictions of film thickness compare favorably with experiments which use the optical interference method, as well as with other theoretical results for an infinite line contact, or an ellipse having a long slender aspect ratio. The maximum EHL pressure occurs near the start of the profiling and can exceed pressure concentrations there predicted by elastostatic theory.
TL;DR: In this article, the thermohydrodynamic performance of the bearing is analyzed, taking into account the three-dimensional variation of lubricant viscosity and density, and the effect of pivot position and operating and environmental conditions on the performance is studied.
Abstract: The thermohydrodynamic performance of the bearing is analyzed, taking into account the three-dimensional variation of lubricant viscosity and density The effect of pivot position and operating and environmental conditions on the performance is studied The present analysis is compared with the isoviscous or the two-dimensional analysis, and is found to predict the bearing performance more accurately
TL;DR: In this paper, a simplifed analysis of viscous squeeze-film damper behavior is presented, which makes use of the notation of averaged inertia and calculates linear velocity and inertia coeffcients.
Abstract: This paper presents a simplifed analysis of viscous squeeze-film damper behavior. It makes use of the notation of averaged inertia and calculates linear velocity and inertia coeffcients. These coefficients are shown to be accurate at practical values of the length/diameter ratio and the gap Reynolds number of the viscous damper.
TL;DR: In this paper, a solution analytique precise for determining the surface, surface de contact, and the contraintes for le contact de formes de surface arbitraires is presented.
Abstract: Sur la base de la solution generalisee de Boussinesq pour un demi-espace en couches, formulation des coefficients de deplacement et de contrainte pour une charge uniformement repartie appliquee a une zone rectangulaire sur la surface d'un demi-espace en couches. Developpement d'une solution analytique precise pour determiner la pression de surface, la surface de contact, et les contraintes pour le contact de formes de surface arbitraires. Obtention de resultats numeriques dans un cas simulant le contact d'un element de roulement en acier avec une bague d'acier supportee par un substrat d'aluminium dans un systeme de transmission
TL;DR: In this article, the stiffness and damping coefficients of the fluid film in mechanical face seals are calculated for the three major degrees of freedom of the primary seal ring based on small perturbation of the ring from its equilibrium position.
Abstract: The stiffness and damping coefficients of the fluid film in mechanical face seals are calculated for the three major degrees of freedom of the primary seal ring. The calculation is based on small perturbation of the ring from its equilibrium position. Analytical expressions are presented for the various coefficients and a comparison is made with results of accurate but more complex analyses to establish the range of applicability.
TL;DR: In this paper, a dynamique non lineaire transitoire dans le temps for l'etude du mouvement des segments oscillants de palier statiquement non charges is presented.
Abstract: Presentation d'une analyse dynamique non lineaire transitoire dans le temps pour l'etude du mouvement des segments oscillants de palier statiquement non charges. Etude parametrique montrant que les parametres des paliers a segments oscillants sont importants pour la vibration auto-excitee d'un segment et son elimination