bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress Distributions in Plane Strain Layered Elastic Solids Subjected to Arbitrary Boundary Loading
Authors: Gupta P. K. , Walowit J. A. , Finkin E. F.
Published: November 2010

Mechanical behavior of surface-coated bearing materials is analyzed and the possibilities of high tensile and shear stresses, which may lead to ultimate cracking of the coating, is investigated. An analysis for the stress distribution in layered elastic solids subjected to an arbitrary boundary loading is presented in terms of Fourier transforms of the Airy stress function. Stresses at the layer substrate interface as obtained by normal elliptical pressures at the layer surface are compared with those obtained by true pressure profiles. It is shown that for most cases the analysis for stress distributions in the materials of the layered solid may be performed by assuming an elliptical pressure at the boundary. However, the parameters for the ellipse should be obtained from the general solution to the contact problem. It is shown that extremely high tensile stress may be developed in the layer when the layer is relatively rigid compared to the substrate. Also, the shear stresses on the layer surface can induce high tensile stresses in the layer. These stresses will generally be responsible for brittle fracture or rupture of surface coatings used in many bearing applications.
Experiments on the Stability of Various Water-Lubricated Fixed Geometry Hydrodynamic Journal Bearings at Zero Load
Authors: Schuller F. T.
Published: November 2010

Stability tests were conducted with 3.8 centimeter-(1.5 in.-) diameter, 3.8 centimeter-(1.5 in.-) long, fixed geometry hydrodynamic journal bearings in water at 300 K (80 deg F) with zero load. Five fixed geometry bearings were rated in order of diminishing stability as follows: (1) three-tilted-lobe bearing (offset factor of 1.0), (2) herring-bone-groove bearing, (3) one-segment, three-pad, shrouded Rayleigh-step bearing, (4) three-tilted-lobe journal with axial grooves (offset factor of 1.0) mated with a plain bearing, and (5) three-centrally-lobed bearing with axial grooves (offset factor of 0.5). Maximum stability in lobed bearings and journals is achieved when the lobes are tilted so that the points of minimum film thickness occur near the trailing edges. The herringbone-groove journals had a maximum stability (maximum fractional frequency whirl onset speed) when the groove to ridge clearance ratio was closest to 2.1, as predicted by incompressible flow theory. The one-segment, three-pad shrouded Rayleigh-step bearing configuration was the most stable of the four step-bearing configurations tested. The tilted-lobe journals mated with plain bearings were unique in that, in some tests, the bearings could be run to a shaft speed twice the shaft speed at which initial fractional frequency whirl occurred before any sign of bearing distress was observed.
Approximations in Turbulent Film Analysis
Authors: Burton R. A.
Published: November 2010

In the analysis of thin turbulent films, approximations must be made in (a) the calculation of the relationship between flow and wall stress, (b) the effects of inertia at steps, and (c) the effects of roughness. The state of such approximations is discussed and, where appropriate, different approaches are compared.
Development and Effects of Super-Critical Taylor-Vortex Flow in a Lightly Loaded Journal Bearing
Authors: DiPrima R. C. , Stuart J. T.
Published: November 2010

At sufficiently high operating speeds in lightly loaded journal bearings the basic laminar flow will be unstable. The instability leads to a new steady secondary motion of ring vortices around the cylinders with a regular periodicity in the axial direction and a strength that depends on the azimuthial position (Taylor vortices). Very recently published work on the basic flow and the stability of the basic flow between eccentric circular cylinders with the inner cylinder rotating is summarized so as to provide a unified description. A procedure for calculating the Taylor-vortex flow is developed, a comparison with observed properties of the flow field is made, and formulas for the load and torque are given.
On the Possibilities of Improving the Accuracy of the Evaluation of Inertia Forces in Laminar and Turbulent Films
Authors: Constantinescu V. N. , Galetuse S.
Published: November 2010

The momentum equations for laminar and turbulent flow in fluid films are evaluated by assuming that the shape of the velocity profiles is not strongly affected by the presence of the inertia forces. Approximate integral momentum equations are thus obtained, which are similar in form to those proposed in a previous paper, but have an improved accuracy in evaluating the influence of the inertia forces, especially when the film exhibits regions with reverse flow. It is thus found that the overall influence of the inertia forces consists, for example, in a partial conversion of the static pressure into dynamic pressure when the flow is accelerated, rather than a complete conservation of the total pressure as assumed in a previous work.
Performance of Thrust Bearings at High Operating Speeds
Authors: Gregory R. S.
Published: November 2010

As part of a continuing research program, a standard 10 1/2 in. dia thrust bearing, of the tilting-pad, self-equalizing type, was tested at shaft speeds up to 11,000 rpm and bearing loads ranging up to 400 psi. The bearing and lube oil system were instrumented to measure bearing performance under laminar and turbulent operating conditions. The effects of varying the oil feed rate on bearing temperature and power loss are discussed in this paper. Some observations on the laminar to turbulent transition region are included.
The Thermally Boosted Oil Lubricated Sliding Thrust Bearing
Authors: Rodkiewicz C. M. , Hinds J. C. , Dayson C.
Published: November 2010

The effect of varying the ratio of slider to pad temperature boundary conditions and the influence of varying inlet to outlet ratio of a plane infinitely wide slider bearing is examined. The lubricant is assumed to be incompressible and the variation of viscosity with temperature is taken into account. The nondimensionalized governing equations, transformed in terms of the stream function, are solved numerically. The results show that maintaining a lower slider temperature to pad temperature ratio causes an increase in the load carrying capacity of the bearing. A means of which advantage could be taken of this effect in the design of thrust bearings is suggested.
Analysis of the Stiffness and Damping of an Inherently Compensated, Multiple-Inlet, Circular Thrust Bearing
Authors: Stiffler A. K.
Published: November 2010

A circular thrust bearing with inherently compensated feedholes evenly distributed around an interior radius is analyzed. The feedhole boundary between the central disk region and exterior annular region is modeled as a line source. A periodic load disturbance is imposed on the bearing, and the dynamic pressure distribution is determined by small perturbations of the Reynolds equation. The solution is given in terms of Kelvin functions. Design curves are presented for the stiffness and damping as a function of squeeze number, external pressure, restrictor coefficient and feedhole location.
Static and Dynamic Performance of Externally Pressurized Fluid Film Journal Bearings in the Turbulent Regime
Authors: Heller S.
Published: November 2010

The fluid film lubrication equations for externally pressurized bearings are solved for steady-state performance and spring and damping coefficients using finite differences and a variable grid bearing model. Turbulence is included as local effective viscosities. Entrance inertia effects are included at the recess edges and are seen to be a significant factor for flow estimates. Performance data is developed for a six-pocket bearing of L/D = 0.75. Experimental verification was obtained for load capacity, flow, and dynamic coefficients, using a two-bearing dynamic test rig and water at speeds from 0 to 4000 rpm. Axial flow of Reynolds numbers range from 22,000 to 125,000.
Temperature Measurements in Sliding Elastohydrodynamic Point Contacts
Authors: Turchina V. , Sanborn D. M. , Winer W. O.
Published: November 2010

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.
A Method for Determination of Constant and Varying Friction Factors During Ring Compression Tests
Authors: DePierre V. , Gurney F.
Published: November 2010

Available mathematical analyses have been applied to develop a reliable method for treating experimental results from ring compression tests with and without bulge formation to obtain quantitative evaluation of constant and varying friction factors, m, and stress-strain curves of the test material. Ring compression tests were made at room temperature on dry and lubricated rings of aluminum, copper, and 1018 steel with 6:3:2 and 6:2:1 (outside diameter:inside diameter:height) nominal dimensions. Neutral radii of the rings at each test height during compression were determined mathematically from measurements of ring dimensions. Substitution of calculated neutral radii and measured ring dimensions into mathematical equations provided quantitative values of the friction factor, m, at each height after compression. Load measurements, made during compression tests, were utilized for verifying the validity of the method.
A Thermal, Thermoelastic, and Wear Simulation of a High-Energy Sliding Contact Problem
Authors: Kennedy F. E. , Ling F. F.
Published: November 2010

This paper describes an investigation of the sliding contact problem encountered in high-energy disk brakes. The analysis includes a simulation modeling, using the finite element method, of the thermoelastic instabilities that cause transient changes in contact to occur on the friction surface. In order to include the effect of wear of the concentrated contacts on the friction surface, a wear criterion is proposed that results in prediction of wear rates for disk brakes that are quite close to experimentally determined wear rates. The thermal analysis shows that the transient temperature distribution in a disk brake can be determined more accurately by use of this thermomechanical analysis than by a more conventional analysis that assumes constant contact conditions. It is also shown that lower, more desirable, temperatures in disk brakes can be attained by increasing the volume, the thermal conductivity, and especially, the heat capacity of the brake components.
Analysis of the Lubricant Film Formation Process in Plane Strain Forging
Authors: Wilson W. R. D. , Wong C. J.
Published: November 2010

A thermal Reynolds’ equation is developed for a lubricant with an exponential viscosity-temperature variation. The equation is used to analyze the film formation process in liquid lubricated plane strain forging. The effects of temperature and pressure induced viscosity changes on the film formation process are described.
Further Investigation of the Delamination Theory of Wear
Authors: Suh N. P. , Jahanmir S. , Abrahamson E. P. , Turner A. P. L.
Published: November 2010

The wear mechanisms of metals under low-speed sliding conditions have been investigated experimentally in order to check the validity of the delamination theory of wear. The subsurface damage done under the wear track is documented using nine different metals with various chemical compositions and microstructures under an argon atmosphere. The experimental results show that the predominant wear mechanism is the wear by delamination of sheets. The wear sheet is generated by a subsurface crack extending over a distance which is in general, one to two orders of magnitude longer than the diameter of the asperity contact. Voids are nucleated around inclusions during plastic deformation. In metals without inclusions the void nucleation rate is low and so is the wear rate, even when they have very low hardness. All these observations substantiate the predictions of the delamination theory of wear. It is postulated that a tangential load which is greater than that predicted by the adhesion theory can be transmitted by a “plowing” mechanism between the sliding surfaces. A new wear equation is presented, which complements the model presented in a previous paper.
Theoretical and Experimental Study of the Glass Lubricated Extrusion Process
Authors: Baque´ P. , Pantin J. , Jacob G.
Published: November 2010

The Ugine-Se´journet patent for glass lubrication of metals extrusion made it possible to extrude steel in large quantities. A cold pad of glass powder inserted between the die and the billet head melts progressively, providing a high viscosity glass film between the die and the metal. The authors propose a theoretical model of the lubrication mechanism: progressive melting, hydrodynamic flow, and stability of the film. The influence of process parameters is discussed and results are compared with experimental measurements.
An Improvement of Rolling Stability During Cold Rolling of Aluminum
Authors: Kondo S.
Published: November 2010

Forward slip during the rolling process is adopted as a measure in evaluating rolling stability. Forward slip during cold rolling of aluminum has a serious effect on the productivity as well as the quality of rolled sheets. The forward slip must remain within a specified range depending on the thickness of sheet if the rolling is to stay stable. Rolling speed, rolling tension, rolling oil viscosity, additives, rolling surface roughness, and roll diameter constitute an important factor for controlling forward slip during rolling. The present paper examines the effects of these factors on forward slip using both production-type and experimental rolling mills.
A Hydrodynamic Lubrication Theory for Strip Rolling Including Thermal Effects
Authors: Dow T. A. , Kannel J. W. , Bupara S. S.
Published: November 2010

A model of hydrodynamically lubricated cold rolling including thermal and pressure effects on the lubricant is developed in this paper. The hydrodynamic film thickness is calculated as well as the work zone pressure and shear stress distribution for several conditions assuming that the lubricant behaves as a Newtonian fluid. Pressure measurements made with vapor-deposited thin-film transducers on the roll surface are used for experimental comparison.
Controlling Hydrodynamic Foil Air-Bearing Clearance With an Opposing Pressure Pad
Authors: Baumann G. W.
Published: November 2010

This paper summarizes a theoretical study of a method of controlling the clearances of hydrodynamic foil bearings. The air-bearing clearance for certain large-wrap cylindrical foil bearings (that is, for perfectly flexible webs) is determined exclusively by the tension, the viscosity of air, the velocity of the web, and the radius of the cylinder. This clearance cannot usually be modified without changing one of the above parameters. However, a pressure pad placed above the web where the web enters the air bearing enables this uniform clearance to be reduced considerably. The pressure pad can thus be used to control the position of the web relative to the cylinder. This paper presents the relationships of the pressures and size of the pad to the reduction in uniform clearance. Clearance profiles for many different pads are also presented, and the practical limitations on reductions in clearance are discussed.
Optimum Design of Multiple-Hole Inherently Compensated Air Bearings—Part 1: Circular Thrust Bearings
Authors: Eshghy S.
Published: November 2010

Analyses of inherently compensated hydrostatic gas bearings of three types are presented. The flow model incorporates empirically the partial recovery of the dynamic pressure in the entrance region. Conditions leading to maximum normal stiffness or/and load are given for air. Analytical results are compared with experimental measurements. Circular thrust bearings are discussed in this article. Subsequent papers will deal with collar thrust and journal bearings.
Spherical and Conical Spiral Groove Bearings—Part II: Load Capacity and Stability
Authors: Bootsma J.
Published: November 2010

The theory developed in Part I is applied to the solving of problems encountered in practice. The manner in which the axial and radial load capacity and stiffness depend on bearing dimensions, particularly on groove dimensions, is shown. The important aspect that spherical and conical spiral groove bearings, just as spiral groove journal bearings, can be stable even if not subjected to a radial load is investigated. A necessary condition for the stability of these bearings in the radially unloaded state is shown to be the complete filling of the bearing gap with a lubricant. In the case of an incompletely filled bearing gap the interaction between the gas-to-liquid interface and the pressure distribution in the lubricating film is such that these bearings have a negative stiffness.
Fatigue Life of High-Speed Ball Bearings With Silicon Nitride Balls
Authors: Parker R. J. , Zaretsky E. V.
Published: November 2010

Hot-pressed silicon nitride was evaluated as a rolling-element bearing material. This material has a low specific gravity (41 percent that of bearing steel) and has a potential application as low mass balls for very high-speed ball bearings. The five-ball fatigue tester was used to test 12.7-mm- (0.500-in-) dia silicon nitride balls at maximum Hertz stresses ranging from 4.27 × 109 N/m2 (620,000 psi) to 6.21 × 109 N/m2 (900,000 psi) at a race temperature of 328K (130 deg F). The fatigue life of NC-132 hot-pressed silicon nitride was found to be equal to typical bearing steels and much greater than other ceramic or cermet materials at the same stress levels. A digital computer program was used to predict the fatigue life of 120-mm- bore angular-contact ball bearings containing either steel or silicon nitride balls. The analysis indicates that there is no improvement in the lives of bearings of the same geometry operating at DN values from 2 to 4 million where silicon nitride balls are used in place of steel balls.
The Frictional Behavior of Human Synovial Joints—Part I: Natural Joints
Authors: Unsworth A. , Dowson D. , Wright V.
Published: November 2010

Some theoretical consideration has been given to the use of pendulum machines when used to examine the frictional properties of human joints by incorporating them as fulcra. As a result, a new type of pendulum machine has been built which incorporates the facility to apply sudden loads to the joint on starting the swinging motion, and also the ability to measure directly the frictional torque experienced by the joint. The results obtained from natural hip joints (reported in Part I) indicate the presence of squeeze film lubrication under conditions of sudden loading. In addition, a self-generated fluid film process was observed at low loads whilst at high loads boundary lubrication appeared to be important. Artificial joints (Part II) are shown to exhibit similar lubrication properties to the natural joints but with a higher absolute value of friction. The metal on plastic type of joint is shown to exhibit a creeplike phenomenon which recovers with time.
Stability of Gas-Lubricated, Externally Pressurized Porous Journal Bearings
Authors: Sun Dah-chen
Published: November 2010

A linear theory of hybrid instability, due to a combination of both whirl and pneumatic hammer, in gas-lubricated porous journal bearings is presented. An approximate solution to the stability problem is obtained by the use of a Galerkin expansion. Results are presented in terms of the variation of stability parameters, such as the threshold mass, the whirl frequency ratio, etc., with the compressibility number and eccentricity ratio. In addition, the effects of permeability, supply pressure, and bearing length are investigated.
Analysis of a Planet Bearing in a Gear Transmission System
Authors: Liu J. Y. , Chiu Y. P.
Published: November 2010

This paper develops a general theory whereby the effects of the elastic distortions of a planet bearing outer ring due to gear loads and inertial forces on the bearing load distribution and fatigue life can be considered. The analysis makes use of a recently developed solution for a thin elastic ring under an arbitrary system of loads. A numerical example for a planet gear roller bearing under heavy gear loads and operating at a high speed is presented.
Pressure Perturbation in EHD Contacts Due to an Ellipsoidal Asperity
Authors: Chow L. S. H. , Cheng H. S.
Published: November 2010

The pressure fluctuations around an ellipsoidal asperity tip at the inlet region of an elastohydrodynamic contact is determined by solving a perturbed Reynolds equation assuming that the asperity shape is unaffected by the perturbed pressure. Results are presented as the amplitude of the perturbed pressure as a function of ellipticity ratio, maximum Hertzian pressure, nominal EHD film thickness, asperity size, asperity height, and pressure viscosity coefficient. For the case of simple sliding between a smooth surface and a stationary asperity, a comparison is also made between the results for large ellipticity ratios and the pressure fluctuations obtained by using a previous line contact EHD analysis [6] for a two-dimensional asperity ridge. The agreement is found to be close for moderate Hertzian pressure and relatively thick EHD film thickness.
Infrared Temperature Mapping in Elastohydrodynamic Lubrication
Authors: Ausherman V. K. , Nagaraj H. S. , Sanborn D. M. , Winer W. O.
Published: November 2010

An improved technique for the measurement of temperature distributions in an EHD conjunction is presented. The technique reported here employs the infrared radiation emitted by the EHD conjunction and appears more rigorous, more reliable, and less cumbersome than that reported previously by the authors. Detailed mapping of fluid temperature (averaged through the thickness) and the ball surface temperature can be obtained. These temperature distributions have been reported for a naphthenic mineral oil for peak Hertz pressures of 1.05 and 1.51 GN/m2 (148 and 219 kpsi), at sliding speeds ranging from 0.35 to 12.7 m/s (13.4 to 500 ips) and a bath temperature of 40°C.
Cyclic Squeeze Films in Micropolar Fluid Lubricated Journal Bearings
Authors: Prakash J. , Sinha P.
Published: November 2010

The Reynolds equation for the general case of dynamic loading is derived for fluid suspensions, using the micropolar fluid theory. Detailed consideration is given to the dynamic behavior of squeeze films in journal bearings under a fluctuating load with no journal rotation. The characteristics of an infinitely long journal bearing under a cyclic sinusoidal load are shown in curve form, so as to elaborate the micropolar effects.
A Life Study of Ausforged, Standard Forged, and Standard Machined AISI M-50 Spur Gears
Authors: Townsend D. P. , Bamberger E. N. , Zaretsky E. V.
Published: November 2010

Tests were conducted at 350 K (170° F) with three groups of 8.9 cm (3.5 in.) pitch diameter spur gears made of vacuum-induction melted (VIM), vacuum-arc remelted (VAR), AISI M-50 steel and one group of vacuum-arc remelted (VAR) AISI 9310 steel. The pitting fatigue life of the standard forged and ausforged gears was approximately five times that of the VAR AISI 9310 gears and ten times that of the bending fatigue life of the standard machined VIM-VAR AISI M-50 gears run under identical conditions. There was a slight decrease in the 10-percent life of the ausforged gears from that for the standard forged gears. However, the difference is not statistically significant. The standard machined gears failed primarily by gear tooth fracture while the forged and ausforged VIM-VAR AISI M-50 and the VAR AISI 9310 gears failed primarily by surface pitting fatigue. The ausforged gears had a slightly greater tendency to fail by tooth fracture than the standard forged gears.
A Refined Model for the Hydrodynamic Lubrication of Strip Rolling
Authors: Wilson W. R. D. , Murch L. E.
Published: November 2010

An analytical model for the hydrodynamic lubrication of high speed strip rolling is developed. The model includes the effect of thermal loading due to back flow and slip on the film formation process. The work zone analysis takes account of thermal effects on film thickness and friction. The influence of geometry, speed and lubricant and work-piece properties on the forward slip, roll load and torque are described in detail and compared with previously published experimental data.
Design Equations for the Short-Time Viscosity Behavior of a Lubricant
Authors: Trachman E. G.
Published: November 2010

A model for the variation of lubricant viscosity in a concentrated contact and a graphical method for determining the reduction of effective viscosity of a lubricant due to insufficient time in the contact zone has been presented in [1]. Design equations are now developed for the effective viscosity which are more convenient for use in numerical procedures.
An Optical Interference Method of Studying the Lubrication of a Compliant Bearing
Authors: Field G. J. , Nau B. S.
Published: November 2010

In recent years, compliant bearings, having one surface of an elastomer, have been studied both theoretically and experimentally. A technique for studying the lubricant film in such a bearing has been developed at BHRA Fluid Engineering in a study of the lubrication of reciprocating elastomer seals. The technique employs optical interference and can determine the film thicknesses to within a few microin. under static, dynamic, and pressurised conditions. The present paper describes the development of the technique and some results which amply illustrate the difference between rigid and compliant bearings.
Theoretical Prediction of Journal Center Motion Trajectory
Authors: Singh D. V. , Sinhasan R. , Tayal S. P.
Published: November 2010

By discretizing time and numerically integrating the equations of motion either for the linearized or the nonlinear journal bearing system, the locus of journal center can be predicted in the wake of a disturbance which upsets the equilibrium. From this locus, not only the stability of the system can be readily checked but also a greater insight into the dynamic characteristics of the rotor bearing systems can be obtained. Systems of solid bearings and porous bearings with journal bearing axes parallel as well as skewed have been studied.
A Systems Approach to Determining Actual Misalignment and Load Distribution for Cylindrical Roller Bearings in Commercial Gear Trains
Authors: Bhardwaj N. K. , Pfaffenberger E. E. , Derner W. J.
Published: November 2010

The Contact Pattern Analysis technique was used to determine the actual distribution of load among rollers, misalignment, and roller edge loading effects in cylindrical roller bearings in a commercial gear train. In all the bearings in the system, the summation of the vertical components of individual roll body loads determined from Contact Pattern Analysis agreed well with the total load imposed on the bearing by the system, thereby demonstrating the practicability and accuracy of the technique. In a few cases the load distribution among rollers in the bearing and, in one case, the number of rollers loaded, were found to be far from ideal. Similarly, it was found that the direction of the bearing reaction differed significantly from the applied load direction. The misalignment as calculated from the contacts was .003 to .005 mm/mm. Also, evidence of contact truncation and roller edge loading at peak torque loads were found. Thus this systems approach, utilizing the Contact Pattern Analysis technique revealed several anomalies that suggest adjusting system parameters, such as housing stiffness and/or roller crown, to improve bearing reliability and performance. This could not have been done by any other known analytical technique.
Design of Nonlinear Squeeze-Film Dampers for Aircraft Engines
Authors: Gunter E. J. , Barrett L. E. , Allaire P. E.
Published: November 2010

This paper examines the effect of squeeze-film damper bearings on the steady state and transient unbalance response of aircraft engine rotors. The nonlinear effects of the damper are examined, and the variance of the motion due to unbalance, static pressurization, retainer springs, and rotor preload is shown. The nonlinear analysis is performed using a time-transient method incorporating a solution of the Reynolds equation at each instant in time. The analysis shows that excessive stiffness in the damper results in large journal amplitudes and transmission of bearing forces to the engine casing which greatly exceed the unbalance forces. Reduction of the total effective bearing stiffness through static pressurization and rotor preload is considered. The reduction in stiffness allows the damping generated by the bearing to be more effective in attenuating rotor forces. It is observed that in an unpressurized damper, the dynamic transmissibility will exceed unity when the unbalance eccentricity exceeds approximately 50 percent of the damper clearance for the relatively wide range of conditions examined in this study.
Short-Time Torque Investigations on DMA-Bearings
Authors: Rivera M. P.
Published: November 2010

A new bearing torque rig capable of qualifying and analyzing bearing torque signals for large-bore high-precision bearings is described. The servomechanical subsystem responsible for torque definition within ± 5.9 × 10−4 Nm is also described. In addition to a space proven lubricant, two lubricants were tested in this rig: KG-80 oil and Polyfluoralkylalkyl polysiloxane grease. Tests were conducted on short-time basis in open air conditions. All three lubricants were tested in a 100 mm bore high-precision angular ball bearing, with and without ball retainer. The bearing was operated at various loads and speeds. Dependence on torque and Root Mean Square-torque as function of lubricant quantity are established. Data trend reveals the existence of a region of minimum torque for oil-retainer bearing configurations. Data also imply the feasability of using the two aforementioned lubricants and the full ball complement configuration in DMA-type applications.
A Theoretical Analysis of a Compliant Shell Air Bearing
Authors: Oh Kong Ping , Rohde Steve M.
Published: November 2010

A mathematical analysis of a class of compliant journal bearings operating with a compressible lubricant is presented. Finite element methods are used to obtain approximate solutions, and results for the rigid case are compared to those obtained by finite difference methods. Results for the case in which the compliant bearing component is a shell show that the steady-state performance can be radically different from that predicted by the rigid bearing assumption. These differences may explain the antiwhirl characteristics exhibited by this type of bearing.
The Dual Action Gas Thrust Bearing—A New High Load Bearing Concept
Authors: Etsion I.
Published: November 2010

The principle of utilizing hydrodynamic effects in diverging films for improving load capacity in gas thrust bearings is discussed. A new concept of dual action bearing based on that principle is described and analyzed. The potential of the new bearing is demonstrated both analytically for an infinitely long slider and by numerical solution for a flat sector shaped thrust bearing. It is shown that the dual action bearing can extend substantially the range of load carrying capacity in gas lubricated thrust bearings and improve their efficiency.
Review of Wear Problems in the Computer Industry
Authors: Engel P. A. , Talke F. E. , Bayer R. G. , Chai S. , Martin J. T. , Adams C. E. , Lee F. F. M.
Published: November 2010

Many mechanical operations in computers tend to cause wear. The authors grouped the problem areas into the following list: 1. Printers; 2. Magnetic recording technology; 3. Wear by paper; 4. Bearings and lubricants; 5. Gears; 6. Electric contacts.
Elastohydrodynamic Lubrication of Elliptical Contacts for Materials of Low Elastic Modulus I—Fully Flooded Conjunction
Authors: Hamrock Bernard J. , Dowson Duncan
Published: November 2010

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.
Asymptotic Methods for a General Finite Width Gas Slider Bearing
Authors: Schmitt J. A. , DiPrima R. C.
Published: November 2010

The method of matched asymptotic expansions is used to develop an asymptotic expression for the load-carrying capacity of a finite width gas slider bearing for large bearing numbers and for film thicknesses varying both in the sliding and transverse directions. The individual terms in the formula for the load are independent of the bearing number and are related to the interior portion, the side edge boundary layers, and the trailing edge boundary layer of the bearing. Only the terms associated with the side leakage phenomena must be computed numerically. Two special cases are discussed: (i) the film thickness varying only in the sliding direction, and (ii) the film thickness having linear or parabolic variation in the sliding direction and parabolic variation in the transverse direction.
Film Thickness and Effective Viscosity of Some Fire Resistant Fluids in Sliding Point Contacts
Authors: Dalmaz G. , Godet M.
Published: November 2010

Optical film thickness measurements are performed in a pure sliding point contact apparatus for different fire resistant fluids: a water in oil emulsion, a water glycol and a chlorinated diphenyl. Good correlation between theoretical and experimental film thickness results is obtained in the elastohydrodynamic regime for a wide range of pressure viscosity coefficients. No relaxation effects are noted, but the viscosity of the water in oil emulsion is shown to exhibit essentially that of the base oil at high shear rates.
Squeeze Film Flow Between Arbitrary Two-Dimensional Surfaces Subject to Normal Oscillations
Authors: Tichy J. A. , Modest M. F.
Published: November 2010

An analytic solution is presented for squeeze film flow with smooth, arbitrary, two-dimensional surface geometry. One surface undergoes sinusoidal oscillation toward the other. The oscillation amplitude is much smaller than the film thickness, which is in turn much smaller than the bearing length. The solution improves on the lubrication theory due to the inclusion of inertia effects. The solution to an illustrative problem is presented—the thrust bearing. The velocity field, pressure distribution and load differ significantly from those predicted by lubrication theory. The results show the lubrication solution for load and pressure to be in error by over 100 percent for Reynolds numbers as low as 5.
Flow in Finite-Width, Thrust Bearings Including Inertial Effects: I—Laminar Flow
Authors: Launder B. E. , Leschziner M.
Published: November 2010

Presented is a new numerical procedure for the calculation of flow in finite-width bearing films. The method, based on the integro-differential approach, is a development of schemes devised by Patankar and Spalding [8] and Gosman and Pun [9] for general flows occurring in fields other than tribology. Principal features of the method are: the full inclusion of inertial effects; the retention of “primitive” variables; the use of a marching solution procedure using line-by-line solution of the discretized conservation equations. Applications to several aspects of laminar inertial flow problems are discussed.
Lubrication of Surfaces Having Area-Distributed Isotropic Roughness
Authors: To̸nder Kristian
Published: November 2010

A mathematical treatment of the problem of lubrication of bearing surfaces exhibiting two-dimensionally distributed uniform or isotropic roughness, is presented. The result obtained previously by the author and consisting of a modified Reynolds’ equation relating smooth mean values, is confirmed. The conditions necessary for the development of the model are shown to hold in all normal bearings.
On Asymptotic Approximations to a Class of Regular Perturbation Problems
Authors: MacDonald D. A.
Published: November 2010

A new approach to a class of regular perturbation problems of common occurrence in lubrication theory is presented. The approach is not dependent on extensive algebraic manipulation and predicts results which, apart from numerical rounding error, are in exact agreement with standard theory. Three illustrative examples are studied in detail and it is demonstrated that asymptotic approximations obtained through use of the approach can be of a substantially higher order than approximations at present in the literature.
Dynamic Characteristic of Multirecess Externally Pressurized Oil Journal Bearing
Authors: Ghosh M. K.
Published: November 2010

This paper describes a theoretical analysis of the dynamic behavior of multirecess externally pressurized oil journal bearings for a nonrotating journal subjected to plane harmonic vibrations. The generalized Reynolds’ equation for a finite bearing has been solved using perturbation theory. Stiffness and damping characteristics of a capillary compensated bearing are given.
A Thermohydrodynamic Analysis of Journal Bearings
Authors: Suganami T. , Szeri A. Z.
Published: November 2010

An attempt is made to formulate a thermohydrodynamic model of film lubrication, that is valid in both laminar and superlaminar flow regimes. The model represents turbulence by eddy diffusivities and, in the manner of Ng and Pan, considers the flow to be a small perturbation of turbulent Couette flow. The energy equation retains heat conduction in the direction of sliding motion, thus making the analysis applicable even at large eccentricities when backflow of the lubricant occurs. The equations are solved by finite element methods. Theoretical predictions are compared with two sets of experimental data, one set hitherto unpublished.
Study of Polyphenyl Ether Fluid (5P4E) in Operating Elastohydrodynamic Contacts by Infrared Emission Spectroscopy
Authors: Lauer J. L.
Published: November 2010

Infrared emission spectra of 5P4E polyphenyl ether were obtained from an operating elastohydrodynamic sliding contact at different speeds and loads by Fourier emission microspectrophotometry. The spectra were found to be polarized with respect to the direction of the conjunction line, especially at high shear rates. Film and metal surface temperatures were calculated from the spectra, and film thicknesses were determined under various operating conditions. Changes of polarized band structure above a critical shear rate, at which the slope of the film temperature versus shear curve changes abruptly and at which the film thickness assumes a minimum value, are consistent with a transition of the lubricant from a viscous liquid to a visco-elastic liquid or to an elastic solid.
Optical Analysis of Porous Metal Bearings
Authors: Yung K. M. , Cameron A.
Published: November 2010

Optical interferometry is used to study the lubrication of porous bearings. The results suggest that thermal expansion in each metal particle causes it to act as a miniature tapered land bearing. An approximate analysis gives an order of magnitude for the tilt. All the evidence is against the existence of a continuous oil film round the bearing when used normally, which hitherto is the accepted model for the operation of these bearings. Micro-recirculation of the oil was observed and the importance of running-in is discussed.
A Functional Evaluation of a Thrust Carrying Cylindrical Roller Bearing Design
Authors: Morrison F. R. , Pirvics J. , Crecelius W. J.
Published: November 2010

A special 60 mm bore cylindrical roller bearing was designed to support the radial and thrust loads developed by a spiral bevel input in a Blackhawk size helicopter transmission. Two prototype bearings were fabricated and tested in a laboratory environment at various loads and speeds simulating that of the application, culminating in a combined load of 7.12 kN radially and 6.79 kN axially at 21,500 rpm. Lubrication was provided by circulating Mil-L-23699 synthetic lubricant into the bearing from jets located on each side and through inner ring supply holes directing the flow to the flange surfaces. Thirty-two hours of operation were accumulated. Detailed examination of the bearing surfaces conducted visually and using the scanning electron microscope established that no abnormal deterioration of the load-supporting contact surfaces had been experienced. It was concluded that the bearing performed satisfactorily and warrants further consideration for application in helicopter transmissions. In addition, an experimental test series was conducted to evaluate bearing performance under predominant thrust loading. This was completed at 1.3 × 106 Dn maintaining the applied axial load at 6.79 kN while reducing the radial load until a thrust to radial load ratio of 9.5 was achieved without difficulty. The condition of the load-supporting contact surfaces after this test was again quite good although the contact patterns were altered. It was concluded that the bearing design also has the potential to operate in this more severe loading environment.
Elastic Connecting-Rod Bearing With Piezoviscous Lubricant: Analysis of the Steady-State Characteristics
Authors: Fantino B. , Frene J. , Du Parquet J.
Published: November 2010

The effect of the deformation of an automotive connecting-rod on the oil film characteristics are studied. The simultaneous elastic deformation and pressure distribution are obtained by iterative methods in steady-state conditions under realistic speeds and loads (5500 rpm, 25,000 N). Plane elasticity relations are used in this study. The following parameters are investigated: —bearing characteristics: bearing thickness B and bearing clearance C, —operating conditions: journal speed N and applied load W, —lubricant: viscosity μ0 and piezoviscous coefficient α. As a result of the deformation, the maximum pressure and the attitude angle are decreased and the relative eccentricity is greatly increased. The minimum oil film thickness is slightly but systematically decreased. The piezoviscosity effect is noticeable only at high loads: it increases slightly the oil film thickness and the maximum pressure. An empirical dimensional equation for the minimum oil film thickness hm is derived numerically for the bearing considered. Thus: hm∼μ0NW0.5(1+0.06108α)B0.12C0.09
Model for the Transfer of Polymer to Rough, Hard Surfaces
Authors: Eiss Norman S. , Wood Kathryn C. , Herold John A. , Smyth Kent A.
Published: November 2010

A process is described for the preparation of low density polyethylene (LDPE) doped with two percent dysprosium oxide for use in transfer experiments. The doping agent made it possible to use neutron activation analysis to measure transfer of LDPE to steel disks at levels of less than one microgram. A model is described which predicts the transfer of LDPE, PVC and PCTFE to within a factor of five or less to measured values of transfer. The model also predicts the penetration depth of the highest asperity into the polymer at which the material transferred fills up the valleys on the surface. The major significance of the model is that it does not require an experimentally determined wear coefficient to make the prediction of transfer. The model uses the normal load, yield strength of the polymer, the apparent area of contact, the bearing area curve for the surface, the polymer density, and the shear angle of the polymer to make the transfer prediction.
Application of Average Flow Model to Lubrication Between Rough Sliding Surfaces
Authors: Patir Nadir , Cheng H. S.
Published: November 2010

The Average Flow Model introduced in an earlier paper is extended to include sliding contacts by deriving the shear flow factor for various roughness configurations. Similar to the pressure flow factors, the shear flow factor is obtained through numerical flow simulation on a model bearing having numerically generated roughness. The flow factors for isotropic and directional surfaces are expressed as empirical relationships in terms of h/σ, a surface pattern parameter γ defined as the ratio of x and y correlation lengths, and the variance ratio Vr1 which is the ratio of variance of surface 1 to that of the composite roughness. Expressions for the mean shear stress and horizontal force components due to local pressure in rough bearings are derived through the definition of shear stress factors, also obtained through simulation. The application of the average Reynolds equation to analyze roughness effects in bearings is demonstrated on a finite slider. The effects of the operating parameters as well as the roughness parameters on mean hydrodynamic load, mean viscous friction and mean bearing inflow are illustrated.
Shear Strength Measurements of Lubricants at High Pressure
Authors: Bair Scott , Winer W. O.
Published: November 2010

Measurements of lubricant shear rheological behavior in the amorphous solid region and near the liquid-solid transition are reported on three lubricants under pressure. Elastic, plastic and viscous behavior was observed. The maximum yield shear stress (limiting shear stress) is a function of temperature and pressure and is believed to be the property which determines the maximum traction in elastohydrodynamic contacts such as traction drives.
An Optical Study of the Lubrication of a 65 mm Cylindrical Roller Bearing
Authors: Pemberton J. C. , Cameron A.
Published: November 2010

All measurements of EHD film thicknesses have been carried out in simulated test machines. This study uses an actual bearing. A test rig using a 65 mm bore radial cylindrical roller bearing has been constructed with a specially designed sapphire window in the outer track. Full loads, and speeds to 3000 rpm were applied. With specially polished rollers and chromic oxide coating on the window excellent interferometric film thickness measurements were found possible. A Xenon flash lamp was used and a Xenon laser of 0–50 pps, pulse half width of 150 ns and peak power of 100 watts was developed for this research. A microscope and 35 mm camera as well as video tape were used for recording results. Arrangements were made to study any chosen roller and the side of the bearing was also open to view. First the film measurements, when corrected for inlet zone viscous heating, agreed admirably with theoretical predictions for mid and exit film thickness. The effect of inlet boundary length on the film was then investigated in some depth. Studying the effect of the multiple roller system, a number of techniques were used to demonstrate that the inlet boundary length, which controls the lubricant film thickness, was itself controlled by the film thickness between the rollers and track in the unloaded zone. The ribs of oil, formed at either edge of the roller, are only secondary sources of oil for replenishment of the inlet film. It is in fact usual (as shown by the convex shape of the inlet zone) for oil to feed out of the inlet zone into the ribs. Oil globules were sometimes observed riding on an air cushion at the entry to the roller-track conjunction, though completely inoperative as providers of oil.