bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbulence Modeling of Axial Flow in a Bare Rod Bundle
Authors: Bartzis J. G. , Todreas N. E.
Published: November 2010

Temperature distribution within the rod bundle of a nuclear reactor is of major importance in nuclear reactor design. However temperature information presupposes knowledge of the hydrodynamic behavior of the coolant which is the most difficult part of the problem due to the complexity of the turbulence phenomena. In the present work a two equation turbulence model—a strong candidate for analyzing actual three dimensional turbulent flows—has been used to predict fully developed flow of infinite bare rod bundle of various aspect ratios (P/D). The model has been modified to take into account anisotropic effects of eddy viscosity. Secondary flow calculations have been also performed although the model seems to be too rough to predict the secondary flow correctly. Heat transfer calculations have been performed to confirm the importance of anisotropic viscosity in temperature predictions. Experimental measurements of the distribution of axial velocity, turbulent axial velocity, turbulent kinetic energy and radial Reynolds stresses were performed in the developing and fully developed regions. A two channel Laser Doppler Anemometer working in the reference mode with forward scattering was used to perform the measurements in a simulated interior subchannel of a triangular rod array with P/D = 1.124. Comparisons between the analytical results and the results of this experiment as well as other experimental data in rod bundle arrays available in the literature are presented. The predictions are in good agreement with the results for high Reynolds numbers.
Onset of Convection in Fluid Layers with Non-uniform Volumetric Energy Sources
Authors: Yu¨cel A. , Bayazitog˘lu Y.
Published: November 2010

The thermal stability of a fluid layer with non-uniform distribution of the volumetric energy sources is studied. The conditions leading to the onset of convective motions in the fluid are determined analytically by linear stability theory. The system considered consists of a fluid layer of infinite horizontal extent which is confined between two rigid parallel boundaries and subjected to general convective boundary conditions. The fluid is heated internally by way of absorption of the external radiation penetrating in the fluid body. The effects of the stabilizing and destabilizing temperature differences at the boundaries and the properties of the bounding surfaces are investigated. Optically thicker layers are found to be more stable.
Quasi-Harmonic Friction-Induced Vibration
Authors: Brockley C. A. , Ko P. L.
Published: November 2010

A theoretical and experimental investigation of quasi-harmonic friction-induced vibration is reported. The vibration is of near-sinusoidal form and is solely governed by dynamic friction forces. However, the friction-velocity curve must be of a particular shape for the vibration to occur. The amplitude of the quasi-harmonic vibration is shown to increase with sliding velocity until oscillation ceases at some upper velocity boundary. The introduction of suitable damping will quench the vibration entirely. The vibration can exist at high sliding velocities and as a consequence may influence the operation of automatic transmissions, brakes, and clutches.
Stability Contours for a Whirling Finite Journal Bearing
Authors: Akers A. , Michaelson S. , Cameron A.
Published: November 2010

The equations of motion have been solved for a journal bearing for L/D = 1/8, 1/2, 1.0, and 12.0. Trajectories have been obtained for motion of the bearing center in both uncavitated and cavitated conditions and the effect of out of balance and of friction in specific cases has been examined. From the trajectories calculated, whirl stability boundaries have been produced. The boundaries are in general accord with work by other authors. It is found that when out-of-balance load is added it sometimes makes the bearing more stable and sometimes less stable. When friction is included it always improves stability. Experimental work with no out-of-balance shows approximate agreement with theory.
A Theoretical Investigation of Compliant Surface Journal Bearings
Authors: Benjamin M. K. , Castelli V.
Published: November 2010

The problem of the compliant surface journal bearing is investigated. The mathematical problem is divided into two parts, the elasticity problem and the fluid problem. The equations of linear elasticity, which represent the elasticity problem, are solved; (a) by expansion of the solution in eigenfunctions (b) by the Raleigh Ritz method, and (c) by a collocation method. Reynolds’ equation, which represents the fluid problem, is then coupled with the solution to the elasticity problem. The corresponding finite difference representation of Reynolds’ equation, which is a set of fourth-order nonlinear algebraic equations, is inverted by Newton iteration. Finally, numerical results are presented.
Fluid Rheological Effects in Sliding Elastohydrodynamic Point Contacts With Transient Loading: 1—Film Thickness
Authors: Sanborn D. M. , Winer W. O.
Published: November 2010

This paper describes an experimental investigation of the elastohydrodynamic problem. The investigation was limited to a study of nominal point contacts in pure sliding motion. The profile of the lubricant film separating the bearing surfaces was determined during a transient of the normal load. During this transient the Hertzian contact stresses were increased from zero to a maximum of 150,000 lbf/in2 in approximately 45 milli-secs. The sliding velocities used in this study were varied from 13.7 to 92.1 ips. The resulting mean shear rate, however, was typically 107 reciprocal seconds. Both pure and polymer-blended naphthenic and paraffinic oils, in addition to several synthetic fluids, were studied. On the basis of the film thickness profiles obtained for the polymer-blended oils, it was concluded that the ambient value of viscosity often used in theoretical considerations does not characterize the behavior of the system. It was also found that the rapid application of the normal load had a negligible effect on the film thickness profile. During this investigation the contact traction was also measured. The results of those measurements are reported in the companion paper, “Fluid Rheological Effects in Sliding Elastohydrodynamic Point Contacts With Transient Loading: II—Traction.”
Cavitation Erosion in a Thin Film as Affected by the Liquid Properties
Authors: Tao F. F. , Appledoorn J. K.
Published: November 2010

The effect of liquid properties and the atmospheric environment on cavitation erosion was investigated in a thin film cavitation apparatus which consists of an ultrasonic horn with a flat tip vibrating against a stationary 1/2 in. ball at a frequency of 20 KC. The experimental results show that cavitation erosion is less severe for liquids of higher gas solubility or at vapor pressures greater than 100 torr. It is therefore possible to reduce the damage by blending a light component in lubricants or liquids and/or by environmental control. The effect of ambient pressure was also observed by tests in vacuum and under various reduced pressures up to one atmosphere. The damage increases with the increase of pressure. These results indicate that the most important factor in cavitation erosion is the differential pressure inside and outside the cavities, with the dissolved gases and/or vapor serving to control this pressure differential. The investigation of cavitation erosion with liquids of various properties also provides information for the understanding of the erosion mechanism. Evidence was obtained which supports the theory that the damage is caused by fatigue failure attributable to the impingement of liquid jets during bubble collapse. The liquid properties may control the jets velocity and thus affect the applied stress on surface boundaries.
Interpretations of the Thickness of Lubricant Films in Rolling Contact. 2. Influence of Possible Rheological Factors
Authors: Bell J. C. , Kannel J. W.
Published: November 2010

Several theories involving rarely analyzed but yet realistic rheological effects have been developed in an effort to find why lubricant film thicknesses in rolling contact, as measured by X rays for rigorous operating conditions, do not obey simple theories well, especially with respect to load effect. The analysis is based on actions in the inlet zone, using the approximate geometry implied for previous simple theories. Effects investigated include a generalized pressure variation of viscosity, a non-Newtonian rheology of Ree-Eyring form, and a time delay in pressure effect on viscosity. Simple formulas are found for the influence of all these factors on lubricant film thickness. The time delay theory is found to provide the best correlation with experimental measurements of film thickness, and it is suggested to offer an attractive field for further research embracing friction effects as well as film thickness.
An Experimental Study of Grease in Elastohydrodynamic Lubrication
Authors: Poon S. Y.
Published: November 2010

The formation of a lubricating film by grease in conditions pertinent to elastohydrodynamic lubrication is studied in a disk machine, and the thickness measured by means of a magnetic reluctance technique. The greases examined are three lithium hydroxystearate greases, of different soap structures and soap contents, a low temperature sodium-based grease, and a high temperature clay-based grease, all in mineral oils. The film thickness of greases in EHL differs from that of pure mineral oils in one important aspect: with one charge of the lubricant the thickness decreases continuously with time. The time-dependent behavior of greases is examined in relation to the thickener structure, viscosity of the base oil, and the conditions of the inlet zone.
An Analysis of the Squeeze Film Between Porous Rectangular Plates
Authors: Wu Hai
Published: November 2010

The squeeze film between two rectangular plates when one has a porous facing is studied theoretically. The problem is described by the modified Reynolds equation in the film region and the Laplace equation in the porous region. Results are presented for pressure distribution, load-carrying capacity, and film thickness as functions of time in series form. The effect of the porous facing on the squeeze film behavior is discussed and found to be important.
An Experimental Study of the Dynamic Behavior of Foil Bearings
Authors: Barnum T. , Elrod H. G.
Published: November 2010

This paper describes an experiment performed to verify the theory for the response of an infinitely wide, perfectly flexible foil to small sinusoidal variations in its tension, as developed in reference [3]. A fixed foil with a rotating drum was used. The tension was oscillated by varying the pressure in a loop of foil at one end with a fixed support at the other. The height of the foil from the drum was measured with a capacitance probe. The results agree substantially with reference [3] especially as to frequency and decay rate of the waves in the foil. However, the theory does not consider the effects of standing waves which can occur in the sections of foil between the supports and drum.
The Hollow-Ended Roller—A Solution for Improving Fatigue Life in Asymmetrically Loaded Cylindrical Roller Bearings
Authors: Derner W. J. , Goodelle R. A. , Root L. E. , Rung R.
Published: November 2010

To reduce the influence of misalignment (asymmetrical loading) on cylindrical roller bearings it is necessary to supplement the crown modifications of bearing elements. A unique hollow-ended roller design was developed for this purpose employing a three-dimensional finite element elasticity study to determine the stress state in the flexible rim section. The results when combined with the classical Hertzian contact stress distribution result in an accurate description of the shear stress field throughout the roller rim sections. Results of fatigue tests run under asymmetrically distributed loads supported the analytical efforts demonstrating significant improvements in L10 lives for the hollow-ended roller as compared to a solid roller. Peak stresses occurred in the vicinity of the contact area for both types of rollers with the solid exhibiting stresses 5 percent or more higher than those found in the hollow-ended type. Of equal importance, the observed failure mode for hollow-ended rollers under heavy load fatigue test conditions is one of conventional subsurface initiated O.D. spalling, thereby proving the rim design to be structurally sound.
Oil Film Thickness and Shape for a Ball Sliding in a Grooved Raceway
Authors: Thorp N. , Gohar R.
Published: November 2010

The behavior in the lubricated contact area of a driven ball sliding in a conforming glass groove, is studied. Interferometry is used to measure the oil film. Coupled ball surface velocity components are provided by angling the drive, while loads and speeds are varied in order to cover a range of conditions from undistorted surfaces to elastohydrodynamic lubrication. A general theory for lubrication with, no distortion and pressure-dependent viscosity, is developed and compared with experiment. Ball spin is found to have only a small effect on the oil film thickness.
Lubrication Review—A Digest of the Literature for 1969–1970
Authors: Rumbarger J. H. , Devine M. J. , Stallings L. , Petronio M. , Glaeser W. A. , Peterson M. B. , Finkin E. F. , Conte A. A. , Chiu Y. P. , Liu J. Y. , Adams M. L.
Published: November 2010

The volume of lubrication literature continued to expand, reflecting increased experimental and theoretical attention being focused upon this discipline. The following eleven categories of lubrication technology are summarized by authorities in each particular field: Developments in Lubrication (including synthetics and greases); Metal-working Lubricants; Plain Bearings; Frictional Behavior of Materials; Wear; Solid Lubrication; Rolling Bearings; Incompressible and Compressible Fluid Film Lubrication and Bearings; Static and Dynamic Seals; Gears and Splines. Over 600 reference publications are included in the review.
Thermohydrodynamic Phenomena in Fluid Film Lubrication
Authors: Seireg A. , Ezzat H.
Published: November 2010

The classical hydrodynamic theory of fluid film lubrication as described by Reynolds’ equation assumes isothermal conditions in the film. Such conditions may never exist in many engineering applications. A common practice is to calculate bearing performance with isothermal conditions at an average film temperature. This paper presents results on the load-carrying capacity of the film when thermal homogeneity does not exist. An empirical procedure is proposed for the prediction of the thermohydrodynamic behavior of the film. A hysteresis-type phenomenon in the pressure-temperature relationship is also observed.
Measurement of the Journal Locus in the Con-Rod Big-End Bearing of an Automobile Gasoline Engine
Authors: Hiruma M. , Furuhama S.
Published: November 2010

To measure the absolute oil film thickness or the journal center locus in con-rod big-end bearings of a practical automobile engine, a special new device and procedure have been developed. By means of this method, the measurement could be carried out stably up to full load at 5000 rpm. These measurements revealed that the journal travels along the vicinity of bearing surface by the inertia force. In the combustion period, however, the journal center passes near the center point of the bearing. On the other hand, under a misalignment condition, the minimum oil film thickness depends on the combustion pressure. Therefore in the future many of the problems related to con-rod big-end bearings will be resolved by this method.
Stability Analysis of an Externally Pressurized Gas-Lubricated Porous Thrust Bearing
Authors: Sun Dah-Chen
Published: November 2010

A linear stability analysis is carried out for a porous thrust bearing considering only the axially symmetric mode of oscillation. It is found that the stability characteristics of the bearing are determined by three competing mechanisms, namely, the compressibility of the lubricant, the mass of the bearing, and the viscous resistance to the thin film flow. To avoid pneumatic hammer, the bearing should be designed to be light weight and to operate at the smallest possible film thickness and supply pressure.
Thin-Film Lubrication Theory for Newtonian Fluids With Surfaces Possessing Striated Roughness or Grooving
Authors: Elrod H. G.
Published: November 2010

Earlier work by others concerning the effects of striated roughness and grooving upon the load-carrying capacity of lubricating films is summarized, substantiated, and generalized. A multiple-scale double-variable technique is used on such lubrication problems for the first time. The present analysis applies to one-face roughness having striation wavelengths sufficiently long for the applicability of Reynolds equation. Transient effects are included. The final differential equation for support pressure is simple in form. In addition to predicting the effects of striated “Reynolds roughness”, this equation can be directly used in grooved-bearing design.
Turbulent Lubrication Theory—Application to Design
Authors: Taylor C. M. , Dowson D.
Published: November 2010

The purpose of this paper is to review the existing turbulent lubrication theories and their application to fluid film bearing design. The differences between and limitations of the alternative approaches are discussed. Design information is stressed rather than fluid mechanics fundamentals, but the basic concepts are dealt with in an appropriate manner in order to give the designer a feel for the nature of the problem. The quantitative predictions of the various theories are compared for the case of a plane inclined slider bearing. Finally, some outstanding questions and possibilities are considered.
Thermohydrodynamic Lubrication in Laminar and Turbulent Regimes
Authors: Safar Z. , Szeri A. Z.
Published: November 2010

The distribution of “effective viscosity”—assumed dependent on local shear and temperature—is obtained via iteration between the “long bearing” momentum and energy equations. In this treatment the shaft is isothermal and the bearing conducts heat only in the radial direction. This last assumption leads to essential simplifications: the bearing is replaced by an equivalent homogeneous boundary condition of the energy equation, which thus becomes amenable to solution by the Galerkin-Kantorovich method. The resulting effective viscosity is used to calculate the performance of finite journal bearings.
Piston Ring Lubrication and Cylinder Bore Wear Analysis, Part I—Theory
Authors: Ting L. L. , Mayer J. E.
Published: November 2010

An analytical method developed for determining the bore wear pattern for a reciprocating piston engine over a complete running cycle is presented. The method includes the considerations of the hydrodynamic lubrication theory between the ring and the cylinder bore wall, piston ring geometric and elastic characteristics, blowby through the piston ring pack, minimum film thickness permitting film lubrication, piston side thrust load and Archard’s wear relation. Since the method is general, it also can be applied to other reciprocating piston devices, such as gas compressor, Rankine cycle engine or Stirling engine. Wear factor data, however, must be available in order to make quantitative predictions of wear. The verification of the present theory is given in a subsequent paper (Part II) which shows good agreement between the predicted bore wear curves and measured ones for actual engines.
Thermal Transients in Finite Slider Bearings
Authors: Ezzat H. A. , Rohde S. M.
Published: November 2010

The thermohydrodynamic (THD) performance of finite slider bearings is studied under nonsteady-state conditions. The fluid film energy, momentum and continuity equations are coupled to the heat conduction equation for the bearing solids and the mathematical system is solved numerically to yield the fluid film temperature-time and load capacity-time histories. The effect of isothermal and adiabatic conditions at the fluid-solid interface is presented. The bearing transient response to constant and time-dependent runner speeds is also discussed.
Evaluation of Load-Life Relation With Ball Bearings at 500 Deg F
Authors: Parker R. J. , Zaretsky E. V. , Bamberger E. N.
Published: November 2010

A survey of the literature suggests that a stress-life exponent of approximately 12 is typical of vacuum-processed steels for ball bearings rather than the exponent of 9 which has been generally accepted by the bearing industry and bearing users. Tests run with vacuum-degassed AISI 52100 balls in the five-ball fatigue tester at four maximum Hertz stress levels in the range from 650000 to 875000 psi showed good agreement with the literature. However, tests run with consumable-electrode vacuum melted AISI M-50 steel angular-contact ball bearings at 500 deg F at three thrust loads did not show significant deviation from the accepted ninth power stress-life relation.
Analysis and Design for Zero Impact Wear
Authors: Engel P. A.
Published: November 2010

Wear life analysis methods are set forth for mechanical components subjected to a large number of repeated compound impacts (normal impact coupled with relative sliding). The wear mechanism in the elastic stress range is surface fatigue, and wear life is strongly contact-stress dependent. Several typical impact problems are discussed in conjunction with analytical and experimental solution methods. A general impact wear formulation is presented for two elastically restrained bodies. The role of lubrication is discussed. Some charts and diagrams are given to aid quantitative treatment.
An Isoviscous Model for the Hydrodynamic Lubrication of Plane Strain Forging Processes With Flat Dies
Authors: Wilson W. R. D.
Published: November 2010

Transient isoviscous hydrodynamic theory is used to investigate the lubrication of plane strain forging processes with flat dies. It is shown that during yielding a film which decreases from a maximum thickness at the center of the contact to zero at the edges is formed. As the deformation continues, the film is transported outwards at half the surface speed of the workpiece. In the case where the dies extend beyond the workpiece, an unlubricated region is formed. The variation in width of this region with reduction predicted by the model is in good agreement with experimental measurements.
Study of Ball Bearing Torque Under Elastohydrodynamic Lubrication
Authors: Townsend D. P. , Allen C. W. , Zaretsky E. V.
Published: November 2010

Spinning and rolling torques were measured in an angular-contact ball bearing with and without a cage under several lubrication regimes in a modified NASA spinning torque apparatus. Two lubricants were used—a di-2 ethylhexyl sebacate and a synthetic paraffinic oil, at shaft speeds of 1000, 2000, and 3000 rpm and bearing loads from 45 newtons (10 lb) to 403 newtons (90 lb). An analytical model was developed from previous spinning friction models to include rolling with spinning under lubrication regimes from thin film to flooded conditions. The bearing torque values have a wide variation, under any condition of speed and load, depending on the amount of lubricant present in the bearing. The analytical model compared favorably with experimental results under several lubrication regimes.
Laboratory Evaluation of Lubricants for Cold Rolling Aluminum Alloys
Authors: Sargent L. B. , Stawson C. J.
Published: November 2010

An instrumented laboratory rolling mill was used to obtain data on the performance of five mineral oil base lubricants in rolling 1100 and 5182 aluminum alloys in the annealed and partially hard tempers. The maximum reductions in a single pass were determined for each lubricant with these alloys. An analysis of the data indicated that the best criterion of the frictional aspects of the lubricants during rolling was the energy used to overcome friction when it was plotted against a Sommerfeld number which used the constrained yield stress of the strip as pressure, the differences in roll and exiting metal velocities as speed, and a viscosity adjusted for the temperature and pressures estimated to exist in the lubricant film during rolling. The correlation of this kind of performance with the known production mill performance of these lubricants was very good. Coefficients of friction calculated from these rolling data did not correlate with known mill performance.
A Solution of the Elastohydrodynamic Problem for Non-Newtonian Fluids
Authors: Kodnir D. S. , Salukvadze R. G. , Bakashvili D. L. , Schwartzman V. Sh.
Published: November 2010

An approximate solution of the stationary isothermal elastohydrodynamic problem has been obtained for a Ree Eyring fluid model also the solution’s algorithm is described for a non Newtonian fluid of an arbitrary model. The solution has been obtained for the complex hydrodynamic and thermal problem for the lubricant film of a non Newtonian fluid with its specified thickness and with a relative surface slip. The diagrams have been made for velocities, temperatures, and tangential stresses in the lubricant film. The solution enables the direct estimation of the tangential stress reduction caused by the non Newtonian fluid’s behavior as well as by the nonisothermal process by means of known theological properties (Newtonian viscosity and time of relaxation) with selected values of pressure and temperature as well as with a given velocity of slip, and with the help of simple nomograms.
Micropolar Squeeze Films
Authors: Balaram M.
Published: November 2010

An analysis of micropolar squeeze films is presented. Expressions are derived for calculating the pressure, the load-carrying capacity of the squeeze film and film thickness–time relationship. Numerical results computed from these expressions reveal that fluid microstructure improves the squeeze film action and increases the load-carrying capacity of the squeeze film, while the load-carrying capacity reduces rapidly with an increase in fluid substructure.
Flow Development in a Parallel Plate Channel
Authors: Szeri A. Z. , Yates C. C. , Hai S. M.
Published: November 2010

The paper presents a study of the flow that occurs in a finite, parallel plate channel. The experimental work consists of velocity profile measurements upstream of and inside the channel of a belt-type apparatus. Theoretical prediction of velocity profile development is made via numerical methods in both laminar and turbulent situations. In the laminar flow case analytical solution of a linearized form of the momentum equation was also possible. Good agreement is shown between prediction and experimental results for all Reynolds numbers tested; in turbulent flow this occurs particularly when employing Reichardt’s eddy viscosity model. For laminar flow the entrance length is estimated to be 0.008–0.01 times the Reynolds number, while in turbulent flow no essential difference was found between an entrance and the corresponding asymptotic profile. Upstream from the entrance the similar laminar profiles of Sakiadis were observed experimentally.
An Instability for Parallel Sliding of Solid Surfaces Separated by a Viscous Liquid Film
Authors: Banerjee B. N. , Burton R. A.
Published: November 2010

Thermoelastic phenomena in lubricated face type seals are analyzed for possible instabilities which may lead to large surface deformations and seal failure. Thresholds of such instabilities are found where a small, steadily moving, surface disturbance will neither grow nor decay. For a good thermal conductor sliding on a good insulator, several such thresholds exist. Only one, however, falls within a reasonable operating range, the critical sliding speed being Ucrit=hκ¯KMμαM where h¯ is the nominal film-thickness, κ the wave number of the disturbance, KM the thermal conductivity of the conductor and αM its coefficient of thermal expansion, and μ the viscosity of the oil. Expressions are given for the approximate limits of h¯ within which such a threshold lies. Finally, it is shown that, as expected, a disturbance will grow when U > Ucrit and decay when U < Ucrit.
Dynamic Characteristics of Externally Pressurized Rectangular Porous Gas Thrust Bearings
Authors: Majumdar B. C.
Published: November 2010

A theoretical study on the behavior of an externally pressurized rectangular porous thrust bearing is made using compressible lubricant. A periodic load is imposed on the bearing and the pressure distribution which leads to the determination of stiffness and damping is obtained by small perturbations. The results are calculated numerically using a digital computer. The tabulated theoretical data of a square pad given for a wide range of design variables enable one to use directly in the design. A design procedure of such a bearing is also indicated.
On the Dynamic Behavior of Hybrid Journal Bearings
Authors: Rohde S. M. , Ezzat H. A.
Published: November 2010

An analysis of the dynamic behavior of hybrid journal bearings is presented. The analysis accounts for the compressibility of the lubricant in the bearing recesses and supply line. Results show that when the journal is subjected to high frequency excitation the bearing stiffness and damping can change drastically. The behavior is characterized by a “break frequency” beyond which the bearing stiffness increases sharply. This is accompanied by a rapid decrease in bearing damping. It is also shown that the cross-coupling stiffness coefficients are reduced at high excitation frequencies. The asymptotic behavior of the stiffness and damping coefficients is examined at both ends of the frequency spectrum.
Dynamically Loaded Pivoted Pad Journal Bearings: Mobility Method of Solution
Authors: ten Napel W. E. , Moes H. , Bosma R.
Published: November 2010

The mobility-whirl angle method as introduced by Booker in 1964, has been applied to pivoted pad journal bearings to predict the behavior of a rotor supported in this type of bearing. Both the single pivoted pad and the complete radial bearing with three equally spaced radial pads have been analyzed. It will be shown that the method is restricted to the case where the value of the load on each pad has to be known from the start. Some experiments have been carried out on a squeeze apparatus. The results are in reasonable agreement with numerical results.
Isothermal Elastohydrodynamic Lubrication of Point Contacts: Part 1—Theoretical Formulation
Authors: Hamrock B. J. , Dowson D.
Published: November 2010

The analysis of an isothermal elastohydrodynamic lubrication (EHL) point contact was evaluated numerically. This required the simultaneous solution of the elasticity and Reynolds equations. In the elasticity analysis the contact zone is divided into equal rectangular areas and it is assumed that a uniform pressure is applied over each element. In the numerical analysis of the Reynolds’ equation a phi analysis where phi is equal to the pressure times the film thickness to the 3/2 power is used to help the relaxation process. The EHL point contact analysis is applicable for the entire range of elliptical parameters and is valid for any combination of rolling and sliding within the contact.
Prediction of Rolling Contact Fatigue Life in Contaminated Lubricant: Part II—Experimental
Authors: Tallian T. E.
Published: November 2010

In this second part of a two-part paper, experimental fatigue life data on ball bearings operated under different lubrication conditions are correlated to surface damage densities of life tested ball bearing inner rings, as determined by scanning electron microscopy. In Part I [16], five cases of a mathematical model for the prediction of fatigue life in contaminated bearings were presented. These models are fitted to the experimental data given in the present Part II. The correlation coefficient of experimental L10 life with model Case II predictions, based on observed defect densities, is of the order of 0.99 and highly significant for most test groups. One grease lubricated group requires fitting by model Case III. Predicted life dispersion exponents are too high compared to experiment. General data on lubricant contaminant densities show a sufficiency of particles to cause the observed surface damage, but tend to overpredict damage on the basis of the simple particle transport model used. The principal usefulness of the model in its present form is as a tool for the interpretation of the influence on fatigue life of surface damage acquired in service.
Dynamic Analysis of Elastohydrodynamic Squeeze Films
Authors: Rohde S. M. , Whicker D. , Browne A. L.
Published: November 2010

This paper contains an analysis of a class of elastohydrodynamic squeeze film problems. A true transient analysis is presented. Thick films bounded by a finite rigid plate and a compliant half-space are considered. The effect of different approach constraints is explored, among these being constant and time varying load and constant and time varying center point pressure. The effect of different material models is also considered.
The Performance of a High-Speed Ball Thrust Bearing Using Silicon Nitride Balls
Authors: Reddecliff J. M. , Valori R.
Published: November 2010

A 35-mm bore angular contact ball bearing having M50 tool steel races and hot pressed silicon nitride balls was tested at speeds to 71,500 rpm (2.5-million DN). The bearing ran smoothly throughout 32 hr of accumulated time. Heat generation was 10 to 20 percent lower than that of a comparable bearing with steel balls, and the silicon nitride bearing began to skid at lower axial loads. The silicon nitride balls and steel raceways were in excellent condition after the test.
A Nonlinear-PH Method of Solution for Journal Gas Bearings
Authors: Cohen M. J.
Published: November 2010

This paper describes a method of solving the Reynolds equations governing the fluid motion in an infinite journal gas bearing. The method derives from an exact transformation of the classical equations to a quasi-linear form. The only assumption made is the isothermal one which in practice closely describes the changes in the state of the gas within the bearing. The solution to the transformed equation for ph is sought in series and there are no difficulties in taking more terms into considerations, apart from algebraic ones. A first order solution is immediately obtained and corresponds as an approximation to any of the following methods: small perturbations (Ausman [1]) Katto and Soda [2], linear-ph (Ausman [3]) Harrison [4]. A higher order solution is also presented which requires little more algebra for its derivation. The extension of the method to three-dimensional gas journal bearings is also outlined.
Conditions of Leakage-Free Operation of Herringbone Grooved Journal Bearings
Authors: Bootsma J. , Tielemans L. P. M.
Published: November 2010

Herringbone grooved journal bearings can have full liquid film lubrication without a continuous external lubricant supply. An attempt has been made to determine the operating conditions at which no leakage occurs. In the many experiments performed with transparent housings the speed was raised until breakdown of the air-to-liquid interface in the bearing gap occurred, and hence leakage commenced. It appears that breakdown of the interface in a completely grooved bearing can be such that it leads to leakage either via the plain surface or via the grooved surface of the bearing. Some speculative theories concerning the breakdown of the interface are considered.
Rolling-Element Fatigue Life of AMS 5749 Corrosion Resistant, High Temperature Bearing Steel
Authors: Parker R. J. , Hodder R. S.
Published: November 2010

The rolling-element fatigue lives of AMS 5749 and AISI M-50 were compared in tests run in the five-ball fatigue tester and the rolling-contact (RC) fatigue tester. The effects of double vacuum melting and retained austenite on the life of AMS 5749 were determined in five-ball fatigue tests. The double vacuum melting process consisted of induction vacuum melting followed by vacuum arc remelting (VIM-VAR). In the five-ball tests, VIM-VAR AMS 5749 gave lives at least six times that of VIM-VAR AISI M-50. Similar tests in the rolling-contact (RC) fatigue tester showed no significant difference in the lives of the two materials. The rolling-element fatigue life of VIM-VAR AMS 5749 was at least 14 times that of vacuum induction melted AMS 5749. A trend toward increased rolling-element fatigue life with decreased retained austenite is apparent, but the confidence that the all experimental differences are significant is not great. The highest level of retained austenite, 14.6 percent, is, however, significantly detrimental to rolling-element fatigue life, relative to the intermediate level of 11.1 percent.
Design Charts for Arbitrarily Pivoted, Liquid-Lubricated, Flat-Sector-Pad Thrust Bearing
Authors: Etsion I.
Published: November 2010

A flat sector-shaped geometry for a liquid-lubricated thrust bearing is analyzed considering both the pitch and roll of the pad. Performance characteristics such as center of pressure location, unit load, and friction loss coefficient, are presented in design charts. These charts enable a direct approach to the design of both point and line pivoted pads and also provide the necessary procedure for the design of nontilting flat pads. The various features of point and line pivoted configurations are discussed, and a comparison is made with the Michell bearing approximation. It is found that this approximation always overestimates load capacity.
The Effect of Viscous Shear Heating on Both Film Thickness and Rolling Traction in an EHL Line Contact—Part II: Starved Conditions
Authors: Goksem P. G. , Hargreaves R. A.
Published: November 2010

A theoretical analysis of both fully flooded rolling traction and film thickness in an EHL line contact has been presented in Part I of this paper. The effect of viscous shear heating was investigated and the results predict a significant reduction in both fully flooded film thickness and rolling traction, relative to the isothermal case, as speed is increased. In this part of the Series, the analysis is extended to consider the calculation of starved rolling traction and film thickness, including viscous shear heating of the lubricant in the inlet region. An approximate equation has been developed, which predicts both the isothermal and non isothermal starved film thickness for all conditions of inlet boundary distance, rolling speed, load, geometry, material constants and lubricant properties. The results show that both rolling traction and film thickness are significantly reduced from the starved isothermal case. For the starved isothermal case, the theoretical analysis for the film thickness agrees closely with experimental data and published empirical formula by Wymer and Cameron, (1974) and the theoretical work of Wolveridge, et al. (1971).
Centrifugally Cast Metallurgical Coatings for Wear Resistance in Plastics Molding Machines
Authors: Saltzman G. A.
Published: November 2010

In extrusion and injection molding, centrifugally cast metallurgical coatings are often utilized to provide wear resistance in the barrel of the molding machine. The need for wear resistance is a result of two potential sources of wear, a screw or plunger that operates within the barrel, and the plastic being processed. Adhesive wear occurs under abnormal operating conditions when the screw bears against the barrel bore. Abrasive wear may result from certain additives used to modify the properties of the plastics. An in situ centrifugal casting process used for production of wear resistant coatings metallurgically bonded to the bores of heavy wall metal tubes is described. Characteristics of industry standard metallurgical coating alloys, a martensitic white iron, a Co-Ni-Cr-B alloy and a composite with tungsten carbide dispersed in a Ni-base alloy matrix are given. Metal-to-metal wear-compatibility tests are discussed.
The Effect of Thermal Diffusion on Flow Stability Between Two Rotating Cylinders
Authors: Li Chin-Hsiu
Published: November 2010

The influence of variable density on the stability of the flow between two rotating cylinders is re-examined. The instability is shown to set in as an oscillatory secondary flow which was overlooked by previous investigators. Results indicate that the radial temperature gradient destabilizes the flow if the outer cylinder is hotter than the inner one, and the destabilizing effect is enhanced if the Prandtl number is high. For the case where the inner cylinder is hotter than the outer one, the stabilizing effect due to the temperature gradient is shown to be weak for any Prandtl number. This modifies previous results which predicted a very high stabilizing effect due to the temperature gradient. The bifurcating structure of the stability curve is shown.
Simplified Solution for Elliptical-Contact Deformation Between Two Elastic Solids
Authors: Brewe David E. , Hamrock Bernard J.
Published: November 2010

A linear regression by the method of least squares is made on the geometric variables that occur in the equation for elliptical-contact deformation. The ellipticity and the complete elliptic integrals of the first and second kind are expressed as a function of the x, y-plane principal radii. The ellipticity was varied from 1 (circular contact) to 10 (a configuration approaching line contact). The procedure for solving for these variables without the use of charts or a high-speed computer would be quite tedious. These simplified equations enable one to calculate easily the elliptical-contact deformation to within 3 percent accuracy without resorting to charts or numerical methods.
Thermohydrodynamic Analysis for Laminar Flow Journal Bearing
Authors: Safar Z. S.
Published: November 2010

This paper describes a semianalytical method for solving the thermohydrodynamic problem in journal bearings. It is assumed that the shaft is isothermal and the bearing heat flow is in the radial direction. The momentum equation is reduced to ordinary differential equations by separation of variables. Two of the resulting equations are integrated directly, while the third equation is interpreted and solved as an isoperimetric problem. The energy equation with its boundary conditions is solved by the Galerkin Kantarovich method.
Elastohydrodynamic Lubrication of Elliptical Contacts for Materials of Low Elastic Modulus: II—Starved Conjunction
Authors: Hamrock B. J. , Dowson D.
Published: November 2010

By using the theory and numerical procedure developed by the authors in earlier publications, the influence of lubricant starvation upon minimum film thickness in starved elliptical elastohydrodynamic conjunctions for low-elastic-modulus materials has been investigated. Lubricant starvation was studied simply by moving the inlet boundary closer to the center of the conjunction. The results show that the location of the dimensionless inlet boundary m* between the fully flooded and starved conditions can be expressed simply as m* = 1 + 1.07 [(Rx/b)2Hmin,F]0.16, where Rx is the effective radius of curvature in the rolling direction, b is the semiminor axis of the contact ellipse, and Hmin,F is the dimensionless mimimum film thickness for the fully flooded condition. That is, for a dimension-less inlet distance m less than m*, starvation occurs; and for m ≥ m*, a fully flooded condition exists. Furthermore, it has been possible to express the minimum film thickness for a starved condition as Hmin,S = Hmin,F [(m − 1)/(m* − 1)]0.22. Contour plots of the pressure and film thickness in and around the contact are presented for both the fully flooded and starved lubrication conditions. It is evident from the contour plots that the inlet pressure contours become less circular and that the film thickness decreases substantially as the severity of starvation increases. The results presented in this report, when combined with the findings previously reported, enable the essential features of starved, elliptical, elastohydrodynamic conjunctions for materials of low elastic modulus to be ascertained.
Effect of Geometry on Hydrodynamic Film Thickness
Authors: Brewe D. E. , Hamrock B. J. , Taylor C. M.
Published: November 2010

The influence of geometry on the isothermal hydrodynamic film separating two rigid solids was investigated. Pressure-viscosity effects were not considered. The minimum film thickness is derived for fully flooded conjunctions by using the Reynolds boundary conditions. It was found that the minimum film thickness had the same speed, viscosity, and load dependence as Kapitza’s classical solution. However, the incorporation of Reynolds boundary conditions resulted in an additional geometry effect. Solutions using the parabolic film approximation are compared with those using the exact expression for the film in the analysis. Contour plots are shown that indicate in detail the pressure developed between the solids.
Measurements of the Statistical Microgeometry of Engineering Surfaces
Authors: Sayles R. S. , Thomas T. R.
Published: November 2010

Surface and profile measurements and their resulting statistics, based on samples of up to half a million heights, are compared and their interrelationship examined for several common engineering surfaces. The measurements are employed to check the applicability of the spectral moment approach to random surface specification. This technique relates many important geometrical properties of a surface to those of its constituent profiles. A relationship is found to exist between the sampling interval and the spatial size of features accommodated by this form of approach. This explains, for example, why 4 and 8 nearest neighbor summit-density analyses based on the same square grid sampling interval reveal very different results. Having established this basic relationship, good agreement is found between theory and measurement over a large range of sampling intervals. In particular, summit densities and distributions are shown to agree well with theory even for non-Gaussian height distributions. It is shown how the isotropic analysis can be extended to cover directionally anisotropic structures such as ground surfaces by defining equivalent movements based on two profiles at right angles. Here again measurements are in good agreement with theory.
Porous Wall Gas Lubricated Journal Bearings: Experimental Investigation
Authors: Gargiulo E. P.
Published: November 2010

A model has been developed to compute the dynamic stiffness and damping properties of externally pressurized, porous-wall, gas journal bearings. The derivation of this model is described in a companion paper. A special test apparatus was constructed to experimentally investigate the steady and unsteady characteristics of a 51-mm diameter by 51-mm long journal bearing. Tests are described for a bearing pressurized to 0.412 MN/m2 at journal speeds up to 20,000 rpm over a range of clearances. Experimental results are compared to those of the theoretical model and show good quantitative agreement for diametral clearances of 25 μm and larger. Reasonable qualitative agreement is shown for smaller clearances. In addition, an unstable vibration phenomenon was discovered and briefly investigated.
Friction and Wear Characteristics of Bearing Materials Under Boundary Lubricated Conditions
Authors: Doi Yoshiki , Haba Tutom
Published: November 2010

This paper presents the results of tests performed with journal bearings with seven bearing materials, at a variety of loads and rotational speeds. On the basis of these results some empirical equations for predicting the behavior of boundary lubricated journal bearings are proposed. It is demonstrated that a noncontact parameter, that is, the ratio of elastohydrodynamic film thickness to the combined roughness of the two mating surfaces, plays the same important role in the behavior of the boundary lubricated journal bearing as in rolling-sliding elements. The friction coefficient is represented by the noncontact parameter and a nondimensional load parameter, besides by material constants, unless preseizure occurs. A critical flash temperature can predict the preseizure. Moreover it is shown that the correlation between the specific wear and the friction coefficient is close at any operating condition.