bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimum Surface Profile for the Enclosed Pocket Hydrodynamic Gas
Thrust Bearing
Authors: Chow C. Y. , Cheng H. S. , Wilcock D. F.
Published: November 2010

The relative importance, with respect to load-carrying capacity, of each geometrical parameter in a self-lubricated thrust bearing, with an enclosed pocket, is examined at Λ = 0.55. The bearing geometries, including the pocket configurations, for three types of film profiles are optimized. The film profiles in the pocket considered are flat-step, tapered, and taper-step, Fig. 1. Of these three profiles of film, the taper-step film, in an enclosed-pocket bearing, offers the best load-carrying capacity. The variations of load versus each geometrical parameter are shown graphically to facilitate design procedure. These results are obtained from the solution of Reynold’s equation for a compressible fluid film as approximated by the finite-difference method [5]. The load-carrying capacity of an enclosed-pocket bearing with taper-step profile can be significantly higher than that of a bearing with the spiral-grooved pattern under the conditions investigated.
Zero-Load Stability of Rotating Externally Pressurized Gas-Lubricated
Journal Bearings
Authors: Fleming David P. , Cunningham R. E. , Anderson W. J.
Published: November 2010

A small eccentricity analysis was performed for a bearing having two feeding planes, each of which is assumed to be a line source. Numerical results were obtained for a range of bearing number, pressure ratio, feeding parameter, and orifice recess volume by means of a digital computer. Steady-state load and attitude angle were obtained, as well as stability data. Stability decreased markedly with increasing recess volume; moreover, for large recess volume and low bearing number, an increase in pressure ratio decreased stability. There was no correlation between stability and steady-state attitude angle for any of the cases studied. Fair agreement was obtained with available experimental data.
Dynamic Response of a Double Squeeze-Film Thrust
Plate
Authors: Chiang T. , Pan C. H. T. , Elrod H. G.
Published: November 2010

The dynamic response of a double squeeze-film thrust plate was analyzed theoretically. Asymptotic approximations were used in calculating the squeeze-film forces. The dynamic response was found to be essentially synchronous; sub-harmonic responses are negligibly small in magnitude. When the squeeze frequency is higher than a critical frequency, the synchronous response is 180 deg out-of-phase with the squeeze motion. This enhances the squeeze action, and thus increases the load capacity and stiffness. The converse is true when the squeeze frequency is lower than the critical frequency.
Finite Element Solution of the Steady-State Compressible Lubrication Problem
Authors: Reddi M. M. , Chu T. Y.
Published: November 2010

Direct and incremental variational formulations for the steady-state compressible Reynolds’ equation are given. Finite element equations for these are derived and sample solutions are presented.
Dynamic Analysis of Three-Foil Rotor Support System in Zero Gravity Environment
Authors: Eshel A.
Published: November 2010

The dynamic and static behavior of a gas lubricated bearing, consisting of stretched foil sectors, is analyzed. General equations describing the fluid film and valid for shaft excursions of the order of the clearance, are derived on the basis of planar motion and negligible fluid inertia. The analysis is then specialized to the case of a bearing consisting of three equally spaced foil sectors. For the static equilibrium condition, tensions and gaps are calculated and graphs are presented. For the dynamic case, the basic equations are linearized, and equations for the in and out-of-phase steady-state response to sinusoidal excitation are derived. This serves as an illustration of foil-bearing dynamic behavior as well as for stability investigation. For the case of zero radial load, the effects of speed, rotor radius, foil thickness, wrap angle, and initial tension on the coefficients of damping and stiffness are graphically presented. Within the range of parameters investigated, the following distinct characteristics of the foil bearing have been found: (a) The bearing is stable. (b) The stiffness coefficient is not sensitive to half frequency excitation nor to excitation of any other frequency. (c) The damping coefficient assumes nearly zero values whenever the ratio of frequency of excitation to frequency of rotation is an integral multiple of π/Θ, where Θ is the wrap angle. (d) In contrast with other fluid-film bearings, the increase in mass has no unstabilizing effect.
The Dynamics of Ball Bearings
Authors: Walters C. T.
Published: November 2010

The details of the dynamics of the elements of a ball bearing become increasingly important at high speeds. A comprehensive general analysis of the motions of balls and a ball separator with realistic lubrication is summarized. The equations of motion consider four degree-of-freedom balls and a six degree-of-freedom separator and are integrated numerically with a fourth order Runge Kutta scheme. Numerical results are presented for a particular spin axis gyro bearing configuration.
Measurement of Elastohydrodynamic Oil Film Thickness and Wear in a Ball Bearing by the Strain Gage Method
Authors: Meyer D. R. , Wilson C. C.
Published: November 2010

A simple method of measuring elastohydrodynamic oil film thickness and wear in a ball bearing using only a preloaded bearing and a strain gage is presented. In order to illustrate this method, measured lubricant film thickness as a function of bearing speed for several different oils are given and compared to theoretical values. Wear data, based on measured wear in an actual bearing, are also presented.
Lubricant and Ball Steel Effects on Fatigue Life
Authors: Rounds F. G.
Published: November 2010

Pitting of rolling contact bearings has been generally considered to be a metallurgical problem since it is a metal part that fails. However, both the physical and the chemical properties of the lubricant have been shown to affect fatigue life. To further study interactions between the ball steel and the lubricant, 4 ball fatigue data were obtained with base oils (25–30 cs at 210 F) and additive-treated lubricants using seven different alloy steels. Both the magnitude and direction of additive effects as well as the magnitude of the base oil viscosity effect on fatigue life were found to depend on the ball steel. The nature of the surface reaction products formed appears to be the principal factor controlling the effect of lubricants on fatigue. These results show that the steel and the lubricant must be considered together to obtain maximum life.
Pneumatic Hammer in a Gas Lubricated Externally Pressurized Annular Thrust Bearing
Authors: Stowell T. B.
Published: November 2010

An experimental study was conducted on the occurrence of pneumatic hammer in a gas lubricated externally pressurized annular thrust bearing. The bearing, which was orifice compensated, was fed by sets of three approximately equal orifices having nominal diameters 0.040, 0.020, 0.015, 0.010, and 0.005 in. Instability was most marked for the supply orifices of nominal diameter 0.020 in. The employment of orifices which had nominal diameters greater or smaller than 0.020 in. tended to make the bearing more stable. Experimental results were compared with the predictions of the simple, lumped parameter analysis.
Nonuniform Magnetic Field Effects in MHD Slider Bearing
Authors: Anwar M. I. , Rodkiewicz C. M.
Published: November 2010

A theoretical analysis is made of a slider bearing using an electrically conducting lubricant in the presence of a nonuniform magnetic field applied perpendicularly to the bearing surfaces. In the differential equations inertia terms are retained and the solution is obtained numerically for low Hartmann numbers. The results indicate that the contribution of inertia terms decreases with the increase of Hartmann number and that the nonuniform magnetic field gives higher load capacity than the comparable uniform magnetic field.
The Narrow Groove Theory of Spiral Grooved Gas Bearings: Development and Application of a Generalized Formulation for Numerical Solution
Authors: Smalley A. J.
Published: November 2010

Application of the narrow groove theory to spiral groove bearings of any rotationally symmetric geometry is described. An effective method for numerical solution of the governing equation to yield radially centered pressures, and small perturbation stiffness performance, is developed. The power of the approach is demonstrated by application to two problems of widely different geometries, one involving a spool bearing, and one involving a spherical bearing.
A Demonstrably Optimum One Dimensional Journal Bearing
Authors: Rohde S. M.
Published: November 2010

By the use of a new variational technique, the bearing profile which maximizes the load carrying capacity of an infinite length journal bearing is obtained. The lubricant is assumed to be incompressible and of constant viscosity. The flow is assumed to be laminar and the optimization is based upon a minimum film thickness. The solution obtained is a concentric step bearing with a film thickness ratio of 1.812 and a ridge to pad ratio of 0.328. It is mathematically shown by the use of the “nonlocal” formulation that this step profile does yield a maximum among all profiles sufficiently “close.”
Stability Characteristics of Floating Bush Bearings
Authors: Tanaka M. , Hori Y.
Published: November 2010

Stability characteristics, or “oil-whip suppressing effect”, of floating bush bearings is investigated theoretically and experimentally. A theory based on the assumptions of “infinitely short bearing” and “film rupture in negative-pressure region” is derived and stability charts obtained by numerical calculations are presented. Experimentally, it is found that there are two kinds of oil-whip suppressing effects depending on mean bearing pressure. The present theory is considered to be valid for the case of relatively high bearing pressure, because of the second assumption, and is actually in good agreement with experiments in that case.
The Role of Compressional Viscoelasticity in the Lubrication of Rolling Contacts
Authors: Harrison G. , Trachman E. G.
Published: November 2010

A simple model for the time-dependent volume response of a liquid to an applied pressure step is used to calculate the variation with rolling speed of the traction coefficient in a rolling contact system. Good agreement with experimental results is obtained at rolling speeds above 50 in/sec. At lower rolling speeds a very rapid change in the effective viscosity of the lubricant is predicted. This behavior, in conjunction with shear rate effects, is shown to lead to large errors when experimental data are extrapolated to zero rolling speed.
A Brief Comparison of the Accuracy of Time-Dependent Integration Schemes for the Reynolds Equation
Authors: Coleman R. L.
Published: November 2010

Two dynamic methods are compared for integrating the Reynolds equation as applied to determining the axial dynamics of a spool bearing. It is shown that very sensitive phase shifts in the numerical schemes can badly falsify the dynamics and thus care is needed in interpreting results using classical methods. Second order temporal accuracy can alleviate these problems and one such scheme is presented with excellent phase properties that is just as computationally efficient per time step as any of the first order accurate schemes.
Static and Dynamic Behavior of Spherical Hydrostatic Bearings: Theory and Experiments
Authors: Whitney D. E.
Published: November 2010

A static and dynamic analysis is carried out for spherical hydrostatic bearings under conditions of incompressible flow. The usual static theory is shown to need the addition of quadratic loss effects in order to agree with experiments. Computer models of static and dynamic behavior agree well with experimental data. Procedures for estimating stiffness and damping are presented taking the extra quadratic losses into account. Comparison with circular recess bearings shows that spherical bearings appear capable of higher damping ratio for the same size bearing.
The Mechanism of Fretting Wear
Authors: Stowers I. F. , Rabinowicz E.
Published: November 2010

An experimental study has been carried out of wear and energy dissipation of contacts vibrated at high frequencies. The amplitude, number of cycles, and degree of lubrication were varied. In addition, an analysis was carried out of quantitative fretting wear results described in the literature. The results suggest that the material loss resembles that produced by unidirectional adhesive wear much more closely than it does that produced by other types of wear, and that in fact the amount of wear may be computed by the use of Archard’s equation.
The Role of Wear in the Initiation of Thermoelastic Instabilities of Rubbing Contact
Authors: Dow T. A. , Burton R. A.
Published: November 2010

Thermoelastic instability of rubbing contact results from the interaction of thermal expansion, frictional heating, and conduction of heat away from the contact zone. These interactions are modified by wear, which is shown to damp the growth of disturbances in contact pressure from a nominal uniform value. In some cases the presence of wear is found to give rise to oscillatory behavior where portions of the rubbing surfaces alternately rise and drop in temperature. These effects are analyzed for the case of a two-dimensional scraper or blade moving normal to its edge, which presses against the surface of a stationary semi-infinite body. The roles of material properties and operating variables are delineated in terms of dimensionless parameters appropriate to the system.
Some Refinements of the Theory of the Viscous Screw Pump
Authors: Elrod H. G.
Published: November 2010

Recently performed analysis for herringbone thrust bearings has been incorporated into the theory of the viscous screw pump for Newtonian fluids. In addition, certain earlier corrections for sidewall and channel curvature effects have been simplified. The result is a single, refined formula for the prediction of the pressure-flow relation for these pumps.
Fatigue Failure Distributions for Ball Bearings
Authors: Smith C. F.
Published: November 2010

High reliability requirements of aircraft gas turbine mainshaft ball bearings necessitate reliable methods for estimating fatigue lives in the early failure region of the life dispersion. Economical and rapid comparisons of surface fatigue lives of modern track materials demand extrapolation from limited numbers of rig results, using a statistical distribution which gives reasonable rectification of early failures. The investigation indicates that lognormal distributions are more satisfactory than Weibull distributions for low failure probabilities.
Experimental Investigation of Porous Bronze Bearings
Authors: Cusano C. , Phelan R. M.
Published: November 2010

An experimental study was made of the performance of porous bronze bearings under different operating conditions. A PV value of 50,000 psi ft/min was found to be too high for the assembly used when the bearings were lubricated only by the oil initially provided within their structure. Tests at a PV value of 33,000 psi ft/min gave satisfactory results. The coefficient of friction was found to vary with load and to be almost independent of speed for the bearings tested under boundary lubrication conditions. Except for relatively light loads and moderate and higher speeds, the bearings operate under boundary lubrication conditions. When pressurized oil was supplied to the bearings, it was found that, for the same operating conditions, porous bearings run at higher eccentricity ratios than solid bearings, as predicted by theoretical analyses.
Molybdenum Disulfide in Oils and Greases Under Boundary Conditions
Authors: Gansheimer J. , Holinski R.
Published: November 2010

A mineral oil and a lithium-based mineral oil grease containing molybdenum disulfide are tested under boundary conditions on the Shell Four Ball Testing Machine and on a modified Reichert Wear Balance. The investigation of the wear tracks by scanning electron microscopy and microprobe analysis shows that a continuous MoS1 film is formed on the metal surface under mild friction conditions. Under extremely severe conditions, however, the MoS2 reacts chemically. It is found that molybdenum diffuses into the steel surface forming intermetallic compounds and carbides which improve the quality of the steel surface. The effect of time and pressure on the thickness of the molybdenum disulfide is determined and the amount of wear reduction by chemical reaction of molybdenum disulfide with the steel surface is compared to that of a traditional EP-additive.
Elastohydrodynamic Traction Characteristics of 5P4E Polyphenyl Ether
Authors: Smith R. L. , Walowit J. A. , McGrew J. M.
Published: November 2010

An elastohydrodynamic rolling disk test apparatus has been designed, built, and a matrix of traction data covering a range of loads, speeds, and temperatures have been obtained for 5P4E polyphenyl ether. Measured tractions are found to markedly increase with load and decrease moderately with rolling speed. The data show a very weak sensitivity to temperature. An apparent viscosity model has been advanced which uses an increased base viscosity and a decreased pressure coefficient of viscosity determined from the traction data to correlate the traction data and can provide a reasonable mathematical representation of the data.
The Effect of Variable Viscosity on the Stability of Plain Journal Bearings and Floating-Ring Journal Bearings
Authors: Nikolajsen J. L.
Published: November 2010

A theoretical analysis including linear perturbation is presented, investigating the stability against fractional frequency whirl (“oil whip”) for a symmetrical rotor supported in plain journal bearings or in floating-ring journal bearings operating with an incompressible lubricant under laminar fluid film flow conditions. In order to improve the conventional theoretical model of the bearing behavior, emphasis is put on the effect on stability of the considerable viscosity gradient which can arise in the bearing film due to film friction. The results are presented in the form of design data diagrams for the two bearing types. In the area of practical interest, the average effect on stability arising from the consideration of the viscosity gradient can be characterized as moderate. Concerning the floating-ring bearing superior stability characteristics are obtained primarily from correct choice of clearance ratio.
The Incompressible-Turbulent-Thin-Film Short Bearing With Inertial Effects
Authors: Burton R. A. , Hsu Y. C.
Published: November 2010

Solutions are derived for the limiting short-bearing configuration of complete 360 deg journal bearings. The analysis draws upon an integrated form of the momentum and continuity equations, and is supported by velocity profile measurements on crossed Couette and pressure flows. Results are compared with pressure measurements made in a large scale bearing model, and are shown to account for the principal features of the pressure distribution. The contribution of inertia is discussed with regard to an experimentally and analytically predicted static instability under small displacements from the central position of the shaft.
Squeeze-Film Behavior in Porous Circular Disks
Authors: Murti P. R. K.
Published: November 2010

The squeeze film behavior between two circular disks is analyzed when one disk has a porous facing and approaches the other disk with uniform velocity. The modified Reynolds equation governs the pressure in the film region while the pressure in the porous facing satisfies the Laplace equation. These equations are solved in a closed form and expressions are derived for pressure distribution, load capacity, and time of approach for the plates in terms of Fourier-Bessel series. It is found that an enhanced value for the permeability parameter diminishes the pressure over the entire disk and also evens out the pressure distribution; however, there is an adverse effect on the load capacity and time of approach. Unlike in the nonporous case, the entire fluid can be squeezed out in a finite time resulting in actual contact of the disks. The porous effects are shown to predominate at very low film thickness values.
The Geometrically Irregular Foil Bearing
Authors: Dais J. L. , Barnum T. B.
Published: November 2010

Equations are derived for the steady state problem of a foil moving relative to a drum with a geometric deviation from the perfectly circular shape. The fluid in the lubricating film is considered as incompressible and the foil as perfectly flexible but possessing mass. Numerical results are presented for the problem of a stationary foil stretched over a rotating circular drum with a flat.
Ambient Edge Correction for the Locally Incompressible Narrow-Groove Theory
Authors: Gupta P. K. , Coleman R. L. , Pan C. H. T.
Published: November 2010

Numerical solutions to the ambient edge problem associated with narrow helical grooves are presented. It is shown that the computed value of edge correction, Δcorr, holds a parabolic relation with the mesh size. The final converged solutions are, therefore, obtained by extrapolating numerical results obtained at different mesh sizes. For extreme cases, the numerical solutions are in total agreement with the analytical solutions obtained by Elrod [1, 2]. Complete maps for the edge correction as a function of groove geometry are presented.
Pressure and Traction Rippling in Elastohydrodynamic Contact of Rough Surfaces
Authors: Tallian T. E.
Published: November 2010

Local variations in asperity dimensions (rippling) of elastohydrodynamic (EHD) pressure are calculated using Christensen’s stochastic model of the hydrodynamics of heavily loaded two-dimensional contacts between rough surfaces. Pressure ripple amplitudes of the order of the maximum Hertz pressure, i.e., well in excess of 105 psi (69.107 N/m2) are predicted at the inlet perimeter of the EHD contact plateau and at the upstream slope of the exit constriction for heavily loaded contacts, if the plateau film thickness to rms roughness ratio is h/σ = 2. Pressure ripple amplitudes in excess of 104 psi (69.106 N/m2) are probable even for the thick film condition h/σ = 10. Sliding traction rippling is calculated for small slide/roll velocity ratios in the same type of contact, and ripple amplitudes in excess of the mean value of the traction are predicted in the high pressure EHD plateau region of the contact for h/σ = 3. The predicted traction ripple amplitude exceeds 30 percent of the mean traction, even for h/σ = 6. Rippling increases the average traction over that for smooth surfaces. Both the pressure and traction rippling may contribute to surface plastic flow and fatigue.
Continuous as Against Intermittent Fling-Off Cooling of Gear Teeth
Authors: van Heijningen G. J. J. , Blok H.
Published: November 2010

The main subject of the present paper is the still relatively unknown fling-off cooling method through continuous supply of the gear oil to the roots of the tooth faces to be cooled, for instance through holes connecting with a manifold inside the tooth rim. The cooling potentialities of this continuous method are compared with those of the naturally occurring “intermittent” fling-off cooling treated previously by A. de Winter and H. Blok [1]. A third fling-off cooling method is again continuous but, in contrast to that by root supply, occurs naturally in that it is brought about by the impingement of comparatively cool droplets from the oil mist in the gear casing. This method will be treated only cursorily, lacking certain experimental data to be substituted in design calculations based on the pertinent theoretical relationships.
The Effects on Bearing Load-Carrying Capacity of Two-Sided Striated Roughness
Authors: Rhow S. K. , Elrod H. G.
Published: November 2010

The multiple-scale method which was earlier employed for lubricating films with striated roughness on one of two opposing surfaces is here extended to include striated roughness on both surfaces. In some papers, the transient effects due to the roughness have been neglected. However, the present analysis shows that the term representing these effects is of the same order of magnitude as others retained in the final equation governing the average pressure. As an example, it is shown that with the same overall roughness characteristics, the load-carrying capacity of an infinitely wide slider bearing varies according to how the same roughness is distributed on opposing surfaces.
A Thermal Reynolds Equation and Its Application in the Analysis of Plasto-Hydrodynamic Inlet Zones
Authors: Wilson W. R. D. , Mahdavian S. M.
Published: November 2010

An equation which is equivalent to the steady, one-dimensional incompressible Reynolds equation but which takes account of viscosity variations across the lubricant film thickness due to energy dissipation within the film is developed. It indicates that the pressure gradients developed in a lubricated contact are reduced by the influence of energy dissipation. The use of the equation is illustrated by applying it in the analysis of the inlet zones of continuous deformation processes such as strip rolling and strip and wire drawing. The analysis indicates that thermal effects play an important role in deciding the lubricant film thickness in such contacts.
Analysis of the Steady State Characteristics of Gas-Lubricated, Porous Journal Bearings
Authors: Sun Dah-chen
Published: November 2010

The steady state operational performance of gas-lubricated porous journal bearings is analyzed by using a numerical iterative method. Results are obtained, and presented in charts and tables, for the length-to-diameter ratio values of 1, 2, and 3; the eccentricity ratio values of 0.2, 0.4, 0.6, and 0.8; the compressibility number from 0 to 10; and several values of the feeding parameter and the supply-to-ambient pressure ratio commonly found in applications.
Dynamic Characteristics of an Inherently Compensated, Square, Gas Film Bearing
Authors: Stiffler A. K. , Smith D. M.
Published: November 2010

A rectangular gas film bearing with inherently compensated feedholes evenly distributed around the interior is analyzed. The feedhole boundary between the enclosed central region and the exterior perimeter region is modeled as a line source. A periodic load disturbance is imposed on the externally pressurized bearing, and the dynamic pressure distribution is determined by small perturbations of the Reynolds’ equation. The solution for the square bearing is obtained by numerical methods. Design curves are presented for the load capacity, mass flow, stiffness, and damping as a function of squeeze number, external pressure, restrictor coefficient, and source location. A design methodology is presented.
Ball Motion and Sliding Friction in an Arched Outer Race Ball Bearing
Authors: Hamrock B. J.
Published: November 2010

The motion of the ball and sliding friction in an arched outer-race ball bearing under thrust load is determined. Fatigue life evaluations were made. The analysis is applied to a 150 millimeter bore ball bearing. The results indicated that for high speed-light load applications the arched bearing has significant improvement in fatigue life over that of a conventional bearing. An arching of 0.254 mm (0.01 in.) was found to be an optimal. For an arched bearing it was also found that a considerable amount of spinning occurs at the outer race contacts.
Motion of a Small High-Speed Rotor in 3 Types of Foil Bearings
Authors: Licht L. , Branger M.
Published: November 2010

Experiments are conducted with 3 types of oilless (air lubricated) foil bearings and a small rotor, at speeds up to and in excess of 3,500 rps (210,000 rpm). The modular construction of the experimental apparatus provides for interchangeability of foil retainers in the supporting brackets, for their alignment, and for the positioning of bearings at various stations along the rotor axis. The symmetrical rotor, 12.7 cm (5.0 in.) long and weighing 2.97 N (0.667 lb) has both cylindrical and conical journals. The main purpose of the investigation is a preliminary examination of whirl-suppressing (stabilizing) characteristics of these flexible bearings, with the objective of application to small high-speed turbomachines.
Elastohydrodynamic Film Thicknesses at Extreme Pressures
Authors: Gentle C. R. , Duckworth R. R. , Cameron A.
Published: November 2010

There has recently been disagreement on the effect of load on elastohydrodynamic film thicknesses at pressures beyond 7 × 108 Nm−2, which was the approximate limit of earlier experiments. This disagreement which concerns a departure from established theory has been heightened by the fact that it is based on results from rather novel techniques. This paper describes an extension of well-characterized optical interferometric measurements on rolling-point contacts to pressures of over 2 × 109 Nm−2. The central film thickness is found to fall off with load at a rate which agrees well with theory. In view of this, the results from other techniques are considered and in one case reproduced. It is concluded that the theory is essentially correct as far as it goes and possible causes of the disagreements are advanced in terms of thermal and surface roughness effects.
Traction of Elastohydrodynamic Contacts With Thermal Shearing Flow
Authors: Jakobsen J. , Winer W. O.
Published: November 2010

The formulation and solution for the shear stress and temperature in heavily loaded sliding elastohydrodynamic contacts is presented. The solutions are presented in dimensionless design charts. Integration over the contact area will yield the traction. Accuracy is expected to be very good over the nearly flat part of the contact area where the majority of the sliding traction is generated. The procedure presented is not appropriate for thick film lubrication, for the inlet region, or for the rolling friction of elastohydrodynamic contacts.
On the Comparison Between Lubrication Theory, Including Turbulence and Inertia Forces, and Some Existing Experimental Data
Authors: Constantinescu V. N. , Galetuse S. , Kennedy F.
Published: November 2010

The results obtained by using lubrication theory, including inertia forces, are checked against experimental data concerning flows in relatively thin films at moderate and large Reynolds numbers. It is shown that a reasonably good agreement is obtained provided that the peculiar features of the experimental flow are properly taken into account; namely, proper consideration of the type of flow (laminar, transition, turbulent), proper evaluation of the region where lubrication flow prevails, entrance flow conditions (relating the flow into the film to the incoming flow), conditions for film rupture, cavitation or separation.
Squeeze Film Theory for Micropolar Fluids
Authors: Prakash J. , Sinha P.
Published: November 2010

Needs’ experimental results on thin films deviate considerably from those predicted by the classical theory when the film thickness is less than 0.00127 mm. In recent years there has been a tendency to attribute this deviation to the inadequacy of the classical continuum theory to describe the fluid flow behavior when confined to narrow passages. In this paper the micropolar fluid theory is applied to the squeeze films for circular disks to explain Needs’ findings. An excellent qualitative agreement is found to exist between the results based on this analysis and Needs’ results. Analytical expressions are obtained for various squeeze film characteristics and effect of microstructure elaborated through graphs.
Linear Transient Response of a Flexible Rotor Supported in Gas-Lubricated Bearings
Authors: Lund J. W.
Published: November 2010

Assuming sufficiently small journal amplitudes, a rotor supported in gas-lubricated bearings represents a nonconservative, nonself-adjoint system with frequency dependent support coefficients. A method is developed to compute the complex eigenvalues together with the associated modal and adjoint functions for such a system for use in establishing normal coordinates. On this basis, the response to any arbitrary excitation is readily obtained. The application of the method is illustrated by calculations of the response to shock excitation and external random vibration of a rigid rotor supported in tilting pad bearings.
Some Effects of Lubricant Starvation in Cylindrical Roller Bearings
Authors: Hargreaves R. A. , Higginson G. R.
Published: November 2010

Experiments on cylindrical roller bearings of 50-mm bore lubricated by an air/oil mist show that friction torque and operating temperatures are much reduced by running at low lubricant supply rates.
Elastohydrodynamic Lubrication in an Instrument Ball-Bearing
Authors: Kannel J. W. , Snediker D. K.
Published: November 2010

The paper deals with experimental measurement of bearing torque and “percentage of lubrication” in instrument size (R6) bearings. The primary parameter found to affect bearing performance for several lubricant investigations is base viscosity. Inference of EHD film thickness is made from the percentage of film measurements which are compared with X-ray data. A reasonable correlation between the two types of data is presented, thereby, paving the way toward the use of the more universally applicable percentage of film measurements for the determination of EHD conditions in real bearing systems.
Short Bearing Analysis Applied to Rotor Dynamics—Part 2: Results of Journal Bearing Response
Authors: Kirk R. G. , Gunter E. J.
Published: November 2010

The results of an extensive investigation of the transient response of rotors supported in fluid-film journal bearings is presented in the form of computer generated orbits of rotor motion. The stability of the rotor-bearing system was determined by examination of the system characteristic equation in Part 1. Rotor transient response orbits demonstrate the rotor behavior below and above the stability threshold. The results show the effect of imbalance, steady loading, cyclic unidirectional and rotating loads upon the stability and performance of a short journal bearing. The results are compared to previous investigations and modified stability maps are deduced from the results obtained. The concept of whirl is examined and several plots presented of the instantaneous whirl ratio and radius of curvature versus cycles of motion (of the journal) for the various cases considered. Bearing forces are analyzed and the resulting plots of force versus cycles of motion are presented for selected cases.
Asymptotic Methods for an Infinite Slider Bearing With a Discontinuity in Film Slope
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 pressure for large bearing numbers for the case of an infinite slider bearing with a general film thickness that has a discontinuous slope at a point. It is shown that, in addition to the boundary layer of the pressure at the trailing edge, there is also a boundary layer in the derivative of the pressure at the point of discontinuity. The corresponding load formula is also derived. The special cases of the taper-flat and taper-taper slider bearings are discussed.
Gas-Lubricated Porous Bearings—Infinitely Long Journal Bearings, Steady-State Solution
Authors: Wu Erh-Rong , Castelli V.
Published: November 2010

The general governing equations for finite porous journal bearings with compressible lubricants and slip-flow are derived. A mass content rule is developed for infinitely long porous bearings; an exact solution is established for a gas-lubricated porous bearing with very large bearing number consistent with the mass content rule. An analytic-numerical technique which takes advantage of the linearity of the pressure equation in the porous medium is developed to solve the problem for finite values of compressibility. The results approach those for the solid bearing case as the defined poro-slip parameter β becomes very large.
The Lubrication of Lightly Loaded Cylinders in Combined Rolling, Sliding, and Normal Motion—Part I: Theory
Authors: Dowson D. , Markho P. H. , Jones D. A.
Published: November 2010

The problem considered in this paper is that of the lubrication of rigid cylindrical solids by an isoviscous lubricant. The steady-state problem has been studied by several authors, but the present analysis explores the effect of non-steady-state conditions arising from combined ‘normal’ and ‘entraining’ motion. It is shown that the major bearing performance characteristics can be accounted for by means of a dimensionless parameter (q) involving the ‘normal’ and ‘entraining’ velocities, the minimum film thickness and the radius of a geometrically equivalent cylinder near a plane. The results are represented graphically and by a set of convenient polynomials in (q). The influence of the cavitation boundary condition is considered and it is shown that sinusoidal ‘normal’ motion superimposed upon ‘entraining’ action can lead to a substantial increase in the nett load carrying capacity.
Analysis of Tapered Roller Bearings Considering High Speed and Combined Loading
Authors: Liu J. Y.
Published: November 2010

This paper presents an analytical study of the load distribution in a tapered roller bearing operating at a high speed and under combined loading. The friction forces at the rolling contacts and the cage forces are not considered. A numerical example showing, among other things, the effects of misalignment and speed on the bearing fatigue life and the sliding velocity at the flange contact is given.
The Fluid Pivot Journal Bearing
Authors: Nelson D. V. , Hollingsworth L. W.
Published: November 2010

A promising new type of tilting pad journal bearing—the Fluid Pivot journal bearing—is described. The long development history of this bearing is summarized, showing how the design evolved through research and testing. Static and dynamic performance features of the bearing are presented, with sample test results compared with predictions based on an advanced computer analysis. Comparisons of the Fluid Pivot journal bearing with conventional mechanically pivoted journal bearings are given.
A Microcontinuum Theory for the Elastohydrodynamic Inlet Zone
Authors: Prakash J. , Christensen H.
Published: November 2010

The micropolar fluid theory is used to analyze the elastohydrodynamic inlet zone of a line contact. The analysis, which is based on Grubin’s approximation, indicates clearly that the additive caused film thickness enhancement as observed by several researchers in heavily loaded contacts has a possible explanation in this theory.
Wear In Lubricated Journal Bearings
Authors: Begelinger A. , de Gee A. W. J.
Published: November 2010

If the combination of bearing material, lubricant, and journal material is well chosen, wear in lubricated journal bearings has a mildly abrasive character, the asperities of the journal surface slowly grinding away material of the inner surface of the bearing. It is shown that this process can be simulated adequately on a pin-and-ring apparatus. Experiments performed on such equipment show that the specific wear rate of bronzes, white metals, aluminum-tin alloys, copper-lead, zinc-aluminum and copper-aluminum increases linearly with increasing surface roughness of the mating component, i.e. a journal made from carburized steel AISI 5120 with a Vickers hardness of 680 · 107 N/m2. It is also shown that, when in contact under conditions of boundary lubrication with copper-tin, copper-aluminium, copper-lead, lead babbitt or tin babbitt the roughness asperities of the hard steel journal gradually disappear by a polishing process. This effect does not occur if the steel journal is in contact with either aluminium-tin or zinc-aluminium. The effect is tentatively explained in terms of an electrochemical interaction between the nonferrous alloys and the steel.
Traction Behavior in Sliding ehl Contacts
Authors: Odi-Owei S. , Roylance B. J.
Published: November 2010

Traction behavior between a stationary disk loaded against a rotating disk has been investigated using two mineral lubricants exhibiting markedly different viscosity characteristics. A theoretical model is developed and compared with experimental results obtained in a twin disk machine in which the importance of lubricant properties is evaluated. The base viscosity and temperature coefficient of viscosity are seen to be important control parameters in this type of operation.
Effect of Wall Thickness and Material on Flexural Fatigue of Hollow Rolling Elements
Authors: Bamberger E. N. , Parker R. J.
Published: November 2010

Hollow cylindrical bars were tested in a rolling-contact fatigue tester to determine the effects of material and outside diameter to inside diameter (OD/ID) ratios on fatigue failure mode and subsequent failure propagation. The range of applied loads with OD/ID ratios of 2.0, 1.6, 1.4, and 1.2 resulted in maximum tangential tensile stresses ranging from 165 to 655 MPa (24,000 to 95,000 psi) at the bore surface. Flexural failures of the hollow test bars occurred when this bore stress was 490 MPa (71,000 psi) or greater with AISI 52100 hollow bars and 338 MPa (49,000 psi) or greater with AISI M-50 hollow bars. Good correlation was obtained in relating the failures of these hollow bars with flexural failures of drilled balls from full-scale bearing tests published previously.
Phase Change in Liquid Face Seals
Authors: Hughes W. F. , Winowich N. S. , Birchak M. J. , Kennedy W. C.
Published: November 2010

A study is made of boiling (or phase change) in liquid face seals. An appropriate model is set up and approximate solutions obtained. Some practical illustrative examples are given. The principal conclusions are: 1) Boiling may occur more often than has been suspected particularly when the sealed liquid is near saturation conditions. 2) The temperature variation in a seal clearance region may not be very great and the main reason for boiling is the flashing which occurs as the pressure decreases through the seal clearance. 3) There are two separate values of the parameter (h/ω2) (and associated radii where phase change takes place) which provide the same separating force under a given set of operating conditions. For a given speed seal face excursions about the larger spacing are stable, but excursions about the smaller spacing are unstable, leading to a growth to the larger spacing or a catastrophic collapse.
Squeeze Film Flow in Arbitrarily Shaped Journal Bearings Subject to Oscillations
Authors: Modest M. F. , Tichy J. A.
Published: November 2010

Squeeze film flow in smooth but arbitrarily shaped infinite journal bearings is considered. The nonrotating shaft is subject to small sinusoidal oscillations. An analytic solution is presented which improves on the lubrication theory by including inertia terms in the equations of motion. The solution technique is to introduce a stream function by which the problem can be reduced to a linear partial differential equation, with time varying boundary conditions, which can be solved by conventional means. The solution to an illustrative problem is presented—the circular journal and bearing. The velocity field and pressure distribution differ qualitatively from those predicted by lubrication theory due to the existence of out-of-phase components. The results show that the lubrication solution for the amplitude of load and pressure can be significantly in error for high Reynolds number operation of a bearing at low eccentricity ratio. At high eccentricity ratios, however, the lubrication theory can be used with confidence, even at very extreme (high Reynolds number) conditions. Simple approximate closed form expressions for pressure and load are presented which are sufficiently accurate for engineering use (error <3 percent) in the range of practical applications.
Effect of Structure on Wear Resistance of Co-, Fe-, and Ni-Base Alloys
Authors: Silence William L.
Published: November 2010

Alloy characteristics that relate directly to wear resistance are much sought after, but elusive. Attempts have been made to correlate wear resistance with mechanical and physical properties, including hardness, but only with limited success. During the course of this investigation, cast, wrought, and hard facing wear alloys were processed using various casting, consolidation and deposition techniques and evaluated using laboratory sand abrasion wear tests, and metal-to-metal (adhesive) wear tests. In general, superior abrasive wear resistance was obtained with those processing conditions that produced microstructures which contained coarse carbide morphologies. No general relationship between hardness and abrasive or adhesive wear was found in this processing study. Little effect of processing, structure or hardness was observed on metal-to-metal wear. Where chemical similarity and common structural condition between the commercial alloys tested allows comment on chemical effects, carbon appeared to be the most effective variable; particularly with abrasive wear where resistance increased with increasing carbon level and volume percent of carbide phases present.
The Behavior of Bubbles in Non-Newtonian Lubricants
Authors: Shima A. , Tsujino T.
Published: November 2010

The behavior of cavitation bubbles and the impulse pressure occurring from the bubble in non-Newtonian lubricants are analyzed as one of the studies on cavitation which is caused on the bearing metals and oil pressure valves. That is, the equation of motion for a bubble and the pressure equation can be derived by using the Sisko model which well represents the rheological properties of lubricants (lubricating greases, and crude oils in place of lubricating oils), and the variation with time of the bubble radius and the pressure and velocity at the bubble wall in greases and crude oils are numerically obtained. In consequence, it was found that the impulse pressure occurring from the collapse of comparatively large bubbles can be a cause for the cavitation damage.
Static and Dynamic Analysis of Capillary Compensated Hydrostatic Journal Bearings by Finite Element Method
Authors: Singh D. V. , Sinhasan R. , Ghai R. C.
Published: November 2010

Using finite element method steady state and dynamic performance of a capillary compensated hydrostatic journal bearing have been investigated. For stability studies, the critical mass of the bearing system has been determined by Routh’s criterion. The locus of the journal center has been predicted by discretizing time and numerically integrating the equations of motion governing the journal bearing system.
Filtration Effects on Ball Bearing Life and Condition in a Contaminated Lubricant
Authors: Loewenthal S. H. , Moyer D. W.
Published: November 2010

Ball bearings were fatigue tested with a noncontaminated MIL-L-23699 lubricant and with a contaminated MIL-L-23699 lubricant under four levels of filtration. The test filters had absolute particle removal ratings of 3, 30, 49, and 105 microns. Aircraft turbine engine contaminants were injected into the filter’s supply line at a constant rate of 125 milligrams per bearing hour. Bearing life and running track condition generally improved with finer filtration. The experimental lives of 3- and 30-micron filter bearings were statistically equivalent, approaching those obtained with the noncontaminated lubricant bearings. Compared to these bearings, the lives of the 49-micron bearings were statistically lower. The 105-micron bearings experienced gross wear. The degree of surface distress, weight loss, and probable failure mode were dependent on filtration level, with finer filtration being clearly beneficial.