bluuebunny/crossref_metadata_2025 huggingface dataset:
Formulation of a Generalized Narrow Groove Theory for Spiral Grooved Viscous Pumps
Authors: Hsing F. C.
Published: November 2010

The well-established narrow groove theory for spiral groove gas bearings [1] has been generalized to include the effects of rarefied gas and turbulence. The slip flow effect was considered locally depending upon gaseous density and molecular mean free path [2] while the local turbulence effect was introduced by a set of viscosity modification functions [3, 4]. For transition flow, the concept of “mean” local Reynolds number may be adapted [5]. The fundamental governing equation was derived in terms of a generalized coordinate for bodies of rotational symmetry and valid for both incompressible and compressible bearings or seals.
The Effect of Cross-Sectional Geometry on the Life of Ball Bearings—An Experimental Investigation
Authors: Kepple R. K. , Mattson R. L.
Published: November 2010

The effect of ball bearing cross-sectional geometry (ring stiffness) on spalling fatigue life of bearings under heavy radial load was investigated experimentally. For a circular undercut design, the particular case tried, the fatigue life was significantly increased, supporting the proposal that an “undercut” below the raceway is desirable. Static load tests showed that force oscillations are reduced in the more flexible bearing. Hence bearing-induced vibrations should be reduced.
Optimization of Conical Hydrostatic Bearing for Minimum Friction
Authors: Nypan L. J. , Hamrock B. J. , Scibbe H. W. , Anderson W. J.
Published: November 2010

Equations for the flow rate, load capacity, and friction torque for a conical hydrostatic bearing were developed. These equations were solved by a digital computer program to determine bearing configurations for minimum friction torque. Design curves are presented that show optimal bearing dimensions for minimum friction torque as a function of dimensionless flow rate for a range of dimensionless load capacity. Results are shown for both laminar and turbulent flow conditions. The results indicate the hydrostatic pocket friction is a significant portion of the total friction torque. However, the bearing dimensions for a minimum friction design are affected very little by inclusion of pocket friction in the analysis. For laminar flow the values of the outerland radius ratio X3 and outer bearing radius ratio X4 did not change significantly with increasing friction factor. For turbulent flow, the outer bearing radius ratio X4 did not change with increasing friction factor; therefore, the value determined for X4 in the laminar flow case is valid for all turbulent flows.
An Elastohydrodynamic Analysis of the Sleeve Type High Pressure Seal
Authors: Harris H. D.
Published: November 2010

A high pressure seal between a moving shaft and a pressure vessel can be formed by arranging for the shaft to pass through a closely fitting externally pressurized sleeve. This paper analyzes the elastic deformation of the sleeve and shaft, and the leakage through the clearance space, for an arbitrary geometry and working fluid. Design curves are presented for use with water.
A Study of the Stability of Externally Pressurized Gas Bearings With Porous Wall by Liapunov’s Direct Method
Authors: Gorez R.
Published: November 2010

Criteria of stability of externally pressurized gas bearings fed through a porous wall are derived from a quadratic Liapunov functional, taking into account the transverse motion of the bearing and the pressure distributions inside the bearing clearance and the porous wall. The stability condition found from this Liapunov functional reduces to the condition previously given by some authors, when the pressure distribution is assumed to be the same as in steady state. Finally, it is shown that the stability domain is increased by diminishing the effective porosity and the thickness of the porous wall.
Analysis of an Arched Outer-Race Ball Bearing Considering Centrifugal Forces
Authors: Hamrock B. J. , Anderson W. J.
Published: November 2010

A thrust load analysis of an arched outer-race ball bearing which considers centrifugal forces but which neglects gyroscopics, elastohydrodynamics, and thermal effects was performed. A Newton-Raphson method of iteration was used in evaluating the radial and axial projection of the distance between the ball center and the outer raceway groove curvature center (V and W). Fatigue life evaluations were made. The similar analysis of a conventional bearing can be directly obtained from the arched bearing analysis by simply letting the amount of arching be zero (g = 0) and not considering equations related to the unloaded half of the outer race. The analysis was applied to a 150-mm angular contact ball bearing. Results for life, contact loads, and angles are shown for a conventional bearing (g = 0) and two arched bearings (g = 0.127 mm (0.005 in.), and 0.254 mm (0.010 in.)). The results indicate that an arched bearing is highly desirable for high speed applications. In particular, for a DN value of 3 million (20000 rpm) and an applied axial load of 4448 N (1000 lb), an arched bearing shows an improvement in life of 306 percent over that of a conventional bearing. At 4.2 million DN (28000 rpm), the corresponding improvement is 340 percent. It was also found for low speeds, the arched bearing does not offer the advantages that it does for high speed applications.
Elastomer Viscoelasticity Effects in Compliant Surface Bearings
Authors: Pirvics J. , Castelli V.
Published: November 2010

A bearing system using a compliant surface may be so constructed that the lubricant pressure distribution is either stationary or in motion relative to the elastomer. In the latter case the motion of the deformation in the elastomer introduces viscoelastic effects which can be important at conventional bearing velocities. This paper is concerned with the assessment of these effects. Steady state operating conditions are computed and analytical techniques presented for the infinite width slider and infinite length journal bearing.
Experimental Rotor Unbalance Response Using Hydrostatic Gas Lubrication
Authors: Dayton R. D. , Chasman M. R.
Published: November 2010

This paper investigates the adequacy of the theoretical model in predicting the unbalance response of a rotor supported in hydrostatic gas-lubricated journal bearings. The magnitude of experimental whirl amplitudes induced by applying various unbalances to a rotor supported in hydrostatic journal bearings were measured and compared to the theoretical predictions. Variables investigated were rotor unbalance, rotor speed, and bearing supply pressure. Reasonable agreement between the experimental and theoretical results was obtained.
The Taylor Vortex Regime in the Flow Between Eccentric Rotating Cylinders
Authors: Mobbs F. R. , Younes M. A. M. A.
Published: November 2010

With the exception of very small clearance ratios, transition to turbulence in journal bearings is likely to be preceded by the appearance of Taylor vortices. The resultant regime may extend over a wide range of Taylor numbers and include transitions to several types of wavy vortex modes. The influence of eccentricity, clearance ratio, and axial flow on the critical Taylor numbers corresponding to the appearance of regular Taylor cells and their subsequent wavy mode transformations is reviewed.
Experimental Study on the Interference of Inertia and Friction Forces in Turbulent Lubrication
Authors: Galetuse S.
Published: November 2010

The experiments concern the turbulent motion of an air film between a rotating cylindrical surface (of large diameter) and a fixed plane surface. The pressure distribution upon the main flow direction and upon the lateral direction were determined. This led to the obtaining of important information on the effect of inertia forces when the lubricant film thickness presents large variations. With the aid of a hot wire anemometer the velocity profiles upon the normal to the fluid film were determined.
Calculation of Pressure, Shear, and Flow in Lubricating Films for High Speed Bearings
Authors: Pan C. H. T.
Published: November 2010

Inertial effects in lubrication flows, can be attributed to the roles of transient acceleration and the convective momentum transport in the dynamic equilibrium condition. As they become important, only when the Reynolds number is very large, a self-consistent analysis must make allowance for the commensurate alterations in the turbulent momentum transport process. At the same time, the pressure boundary condition at entrance edges should be accordingly modified to account for convective momentum transport and the developing shear effects. The latter aspect can be suitably approximated by the conservation condition of total pressure transport. A perturbation method (for inertial effects), which is a direct extension of the (noninertial) linearized turbulent lubrication theory, has been formulated.
Low-Cost Shaft Sealing With Shop Air
Authors: Courtney W. J.
Published: November 2010

This paper elucidates a method of using shop air to seal oil lubricated bearings. A graphical solution of Rayleigh’s equation is presented as a design aid. The efficacy of this sealing method is supported by experimental evidence derived during the development of an ultrahigh-vacuum high-speed rotary feedthrough.
Friction Viewed as a Random Process
Authors: Kilburn R. F.
Published: November 2010

A stationary cast-iron button sliding against a rotating cast-iron disk generated a time-varying friction signal. The signal was recorded using digital computer data-acquisition techniques. Sixty runs were taken, using different values for various parameters (such as load, velocity, and temperature). The data were analyzed on a digital computer by two different techniques. The first was a time-series analysis: the Fourier transform of each run was taken and the power spectral density of the run was studied. The second technique was a standard statistical analysis using the Kolmogorov-Smirnov goodness-of-fit test. From the two analyses, some interesting conclusions were made: 1 – the friction behaves like a random process, 2 – friction may be treated as a constant signal with superimposed white noise, 3 – the instantaneous coefficient of friction is normally distributed, 4 – friction is influenced by load and velocity, and 5 – the mean value and standard deviation are functionally related.
Dynamic Behavior of Pure Squeeze Films in Narrow Porous Bearings
Authors: Murti P. R. K.
Published: November 2010

The dynamic behavior of squeeze film in a narrow porous journal bearing under a cyclic load is analyzed. A thin-walled bearing with a nonrotating journal is considered and a closed form expression for the pressure distribution is derived. The locus of the journal center is found by numerical methods and it is established with an example that actual contact between the journal and bearing can be avoided by appropriate design of the bearing. Consequently, it is proved that pure squeeze films have a load capacity only under cyclic loads. The analysis also reveals that the permeability of the bearing material and the wall thickness of the bearing influence significantly the operating eccentricity ratio.
Analysis of Short Journal Bearings With New Upstream Boundary Conditions
Authors: Etsion I. , Pinkus O.
Published: November 2010

The Reynolds equation, for short journal bearings, is treated with a new approach to the boundary condition at the beginning of the lubricating film. The nondimensional hydrodynamic side leakage and other performance characteristics of the bearing are shown to be a function not only of Sommerfeld number and width over diameter ratio but also of another parameter which depends on the starting condition at the film inlet. The results obtained by other investigators till now are shown to be only a limiting case of the more general analysis given here. This work is the first part of a larger work embracing the analysis of finite bearings.
The Surface Deformation of Aluminum Compressed With Viscous Lubricants
Authors: Ratnagar D. D. , Cheng H. S. , Schey J. A.
Published: November 2010

The influences of lubricant viscosity and loading velocity on the surface finish of plastically compressed 6061 aluminum alloy cylinders were studied. Specimens with polished end faces were subjected to compression between two flat, chromium plated dies, with lubricants of a viscosity ranging from 42 cp to 1207 cp at 38 deg C. The deformed surfaces were studied under a scanning electron microscope and by stylus tracings and CLA readings. With the lighter lubricants surface roughening resulted from preferential yielding leading to a clear delineation of grain boundaries and slip lines. With the heavier lubricants, localized “hydrodynamic pockets” formed in addition to the above features. The depth of pockets increased with viscosity and/or velocity.
Full Journal Bearings Under Dynamic Duty: Impulse Method of Solution and Flapping Action
Authors: Blok H.
Published: November 2010

For full journal bearings impulse capacity, as “consumed” typically during the “dominant quasi-squeeze interval” of severe duty cycles, has proved itself a design criterion much more significant than the conventional one of maximum or time-averaged load capacity. This is first shown for assumedly perfectly rigid bearing/journal systems which, however, are rather unrealistic. Thereupon the author proceeds with illustrating the promising potentialities for promoting impulse capacity that are inherent in “flapping action”, the generalized kind of squeezing engendered by the elastic and pulsating distortion of the circumferential contour of the bearing surface.
The Statistical Application of a Thermal EHL Theory for Individual Asperity-Asperity Collisions to the Sliding Contact of Rough Surfaces
Authors: Fowles P. E.
Published: November 2010

The numerical results of a previously developed thermal EHL theory describing the collisions between idealized asperities are analyzed statistically to obtain macroscopic values of unit load, traction, and friction coefficient for two model surfaces in sliding contact under a range of conditions. It is shown that significant unit loads and tractions can be generated as a result of the microsopic EHL contacts alone. The variation of friction coefficient with load and sliding speed corresponds qualitatively with experiment in the mixed lubrication regime between boundary and hydrodynamic lubrication, but quantitatively the friction coefficients are two to three times too high. The results imply that the lubricant becomes non-Newtonian and/or exhibits a limiting shear strength in virtually all asperity interactions, even those in which the thickness of the intervening lubricant film is maintained in the 20-nm range.
Stability of Rotor-Bearing Systems With Generalized Support Flexibility and Damping and Aerodynamic Cross-Coupling
Authors: Warner R. E. , Soler A. I.
Published: November 2010

This paper examines stability of the flexible single mass rotor, acted on by motion induced forces due to aero-dynamic cross-coupling and supported most generally by oil film tilting pad bearings which are in turn mounted on flexible, damped supports. Plotted results include the frequency dependent spring and damping coefficients for the 4-pad tilting pad bearing, damping coefficients for the 360-deg squeeze bearing and stability plots of rotor-bearing systems including aerodynamic cross-coupling, the 4-pad tilting pad bearing and the 150-deg partial arc bearing with various support arrangements.
The Short-Time Viscosity Behavior of a Lubricant in a Hertzian Pressure Zone
Authors: Trachman E. G.
Published: November 2010

The variation of the viscosity of a lubricant as it passes through a concentrated contact with a Hertzian pressure profile is predicted by a simple model for the time dependent volume response of a liquid to a sudden change of applied pressure. For a wide range of operating conditions, the computed values of transient viscosity are asymmetric with respect to the center of the contact zone and are significantly lower than the equilibrium values. Three design graphs are presented which allow easy application of the results.
Contributions to the Influence of Retained Austenite Content in Steels on the Temperature Stability of Boundary Lubricant Layers in Friction
Authors: Matveevsky R. M. , Sinaisky V. M. , Buyanovsky I. A.
Published: November 2010

The results of investigations by various authors on the influence of retained austenite on seizure are briefly considered. Using as an example the investigation of the critical temperature of mineral oil in the friction of alloyed steels, it is shown that the temperature of destruction of the lubricant layer appreciably depends on the nature and content of the alloying elements and doe not strictly depend on the retained austenite content in the surface layer of steel specimens. Certain questions are considered—the influence of the contact geometry on the determination of the critical temperature in conditions of boundary lubrication, and the expediency of using austenite steel for investigating the temperature stability of lubricant layers.
On the Axial Symmetric Contact Problem Involving Elastic Hollow Spheres
Authors: Chiu Y. P.
Published: November 2010

An approximate solution is given for the contact problem of an elastic hollow sphere indenting a solid sphere or cup with axial symmetry. The elastic deflection, maximum stress and contact radius are graphically presented as functions of a dimensionless load using hollowness ratios as parameter for the particular case that the two contacting bodies are of the same material. The numerical results include the Hertz theory as a limiting case for small hollowness ratio.
An Investigation of “Diaphragm” Type Thrust Bearings—Part II: Theory
Authors: Tieu A. K.
Published: November 2010

The three types of finite width thrust bearings, tilting pad, diaphragm tilting pad and diaphragm stepped pad, are simulated on the PDP-6 computer taking into account thermal effects on the oil film viscosity and the diaphragm deflection. The temperature boundary conditions of the three-dimensional oil film volume are obtained from the experiment described in Part I. The computed load carrying capacities of the three types of thrust bearings are compared with the experimental results, and quite good agreement between theory and experiment is obtained.
Heat Generated by MHD Couette Flow With Porous Walls
Authors: Balaram M.
Published: November 2010

The simultaneous effects of mass injection and magnetic field on the heat generation due to viscous dissipation is investigated analytically. The present findings are in general agreement with the temperature measurements of Chang-Yi Wang [1]. Results indicate larger reductions in maximum temperature and a significant increase in the heat take off by porous boundaries, if magnetic field is present. The most striking feature of this investigation is the marked improvement in the temperature reduction with the application of the electromagnetic force.
Lubricant Flow in a Plastohydrodynamic Work Zone
Authors: Mahdavian S. M. , Wilson W. R. D.
Published: November 2010

An analysis of the lubricant flow in zones of plastic deformation is developed. This includes the effects of different surface temperatures and shear heating within the lubricant film. Thermal effects on the lubricant velocity and temperature profile, traction and volume flow rate are described. The difference in surface temperatures plays a dominant role in deciding the variation of lubricant film thickness with position and time in metal forming operations.
Hydrodynamic Lubrication of Hydrostatic Extrusion
Authors: Wilson W. R. D. , Mahdavian S. M.
Published: November 2010

An analytical model for the hydrodynamic lubrication of hydrostatic extrusion is developed. This includes the effect of viscous heating on the film formation process and the effect of viscous and plastic heating on the friction and film thickness variation in the work zone. Theoretical predictions of film thickness and extrusion pressure show good agreement with experimental measurements for aluminum billets lubricated with castor oil.
Effects of High-Operating Speeds on Tilting Pad Thrust Bearing Performance
Authors: Capitao J. W. , Gregory R. S. , Whitford R. P.
Published: November 2010

A comparison of the high-speed performance characteristics of tilting-pad, self-equalizing type thrust bearings through two independent full-scale programs is reported. This paper presents experimental data on centrally pivoted, 6-pad, 267-mm (10 1/2-in.) and 304-mm (12-in.) O.D. bearings operating at shaft speeds up to 14000 rpm and bearing loads ranging up to 2.76 MPa (400 psi). Data presented demonstrate the effects of speed and loading on bearing power loss and metal temperatures. Included is a discussion of optimum oil supply flow rate based upon considerations of bearing pad temperatures and power loss values.
Chemical Effects of Lubrication in Contact Fatigue—Part III: Load-Life Exponent, Life Scatter, and Overall Analysis
Authors: Littmann W. E. , Kelley B. W. , Anderson W. J. , Fein R. S. , Klaus E. E. , Sibley L. B. , Winer W. O.
Published: November 2010

A brief review of relevant literature is presented with the logic underlying the selection of lubricant base stocks, additives, materials, surface textures, and other variables used in contact fatigue tests under rolling-sliding conditions. Tests of selected combinations (mineral oil with and without a zinc dialkyldithiophosphate additive and a polyolester synthetic with and without its typical additive package) showed that lubricant chemistry affects the stress/life slope and the Weibull slope (scatter in life). Results of the overall program show that the relative contact fatigue life for different lubricant chemistries should be evaluated using operating conditions, especially stress and slip levels, near to expected application conditions.
Influence of Pressure Viscosity of Lubrication Oils on Pressure, Temperature, and Film Thickness in Elastohydrodynamic Rolling Contacts
Authors: Bartz W. J. , Ehlert J.
Published: November 2010

Experimental investigations of pressures, temperatures, and film thicknesses in pure rolling elastohydrodynamic contacts have been made in a two-disk apparatus. Transducers for pressure, gap, and temperature measurements were applied by an evaporation technique. Measurements were made over a range of speeds, loads, and oil inlet temperatures with oils having various pressure-viscosity coefficients. The predicted film thicknesses and shape of the pressure profile (including the secondary pressure peak) agree well with the experimental observations as inlet viscosity, pressure viscosity coefficient, and load are varied.
Surface Roughness Effects on Fatigue in Partial EHD Lubrication
Authors: Li D. F. , Kauzlarich J. J. , Jamison W. E.
Published: November 2010

A simple surface originated fatigue theory has been developed to study the effects of surface topography on the fatigue life of rolling element bearings. The bearing surface fatigue life is assumed to relate to the magnitude of the average shearing stresses generated at the interacting asperities on the surfaces that are separated by an elastohydrodynamic lubricant film of some thickness. Utilizing a published rough surface model, it is possible to express the relative fatigue life of a bearing as a function of the lubricant film thickness to roughness ratio h/σ and a roughness parameter R. Comparison of the theory to sets of published endurance test data has been carried out. Possibilities of fatigue life prediction of both roller and ball bearings in the partial elastohydrodynamic lubrication regime are discussed.
Dynamic Stiffness and Damping of Externally Pressurized Gas Lubricated Journal Bearings
Authors: Fleming David P. , Thayer William J. , Cunningham Robert E.
Published: November 2010

A rigid vertical shaft was operated with known amounts of unbalance at speeds up to 30,000 rpm and gas supply pressure ratios to 4.8. From measured amplitude and phase angle data, dynamic stiffness and damping coefficients of the bearings were determined. The measured stiffness was proportional to the supply pressure, while damping was little affected by supply pressure. Damping dropped rapidly as the fractional frequency whirl threshold was approached. A small eccentricity analysis overpredicted the stiffness by 4 to 55 percent. Predicted damping was close to measured at low speeds but higher at high speeds.
First Effects of Stokes Roughness on Hydrodynamic Lubrication
Authors: Sun Dah-chen , Chen Kuo-Kuang
Published: November 2010

Considering the actual roughness dimensions as well as the typical dimensions of a hydrodynamically lubricating film, the Stokes equations are used to analyze the roughness effects. The surface profile is modeled by an ergodic, stationary random process. It is revealed that the roughness effects can be determined by three parameters; viz., the rms roughness, the correlation length, and the correlation wavelength. The present results are significantly different from those in the literature, where the Reynolds equation is used for analysis.
Bearing Oil Delivery by Disk-Scraper Means
Authors: Gardner W. W.
Published: November 2010

Certain bearing applications require the use of a lubrication system contained within the bearing housing and independent of any outside systems or power sources. Marine main propulsion lineshaft bearings often fall into this category and the use of a disk-scraper system for oil supply represents one solution. Tests on two sizes of such lubricating systems were conducted to determine flow rates and the influence of the primary variables involved. The test data is presented and correlated to assist in the design of this type of lubrication system.
Flow in Finite-Width Thrust Bearings Including Inertial Effects: II—Turbulent Flow
Authors: Launder B. E. , Leschziner M. A.
Published: November 2010

A new set of turbulent resistance laws for hydrodynamic lubricant films has been derived with the aid of a turbulence model which includes transport effects on two turbulence parameters. The model consists of two differential equations for the turbulence energy and its rate of dissipation and a constitutive equation for the turbulent viscosity. The model places no restrictions on the Reynolds number. An efficient finite-difference scheme, based on the integro-differential approach and incorporating the resistance laws and a set of accurate inertial coefficients, is applied to the solution of the turbulent inertial flow in finite-width slider bearings. A selection of predictions is presented for non-inertial and inertial flows. The former are compared with solutions obtained with alternative turbulent lubrication theories. The importance of including fluid inertia effects is demonstrated.
A Simplified Model of Cage Motion in Angular Contact Bearings Operating in the EHD Lubrication Regime
Authors: Kannel J. W. , Bupara S. S.
Published: November 2010

An analytical model describing the in-plane motions of a bearing cage is developed for angular contact bearings operating in the EHD lubrication regime. The ball-cage impacts are treated as impulse forces imparted to the cage. The model is developed on the basis that during ball-cage impact, energy is transmitted to the cage at the ball-cage interface by friction, whereas, cage energy is dissipated at the ball-race interfaces as a result of the ball being caused to translate along its EHD film by the cage. Numerical computations using the model indicate that the level of ball-cage friction, lubricant viscosity, and extent of ball-race lubrication are significant factors in determining the conditions for which the cage motions may be stable or unstable. The predicted trends concerning the stability of the cage motions conform qualitatively to observed experimental results.
On the Analytical Solution of Externally Pressurized Porous Gas Journal Bearings
Authors: Majumdar B. C.
Published: November 2010

A closed form solution of pressure distribution which leads to the determination of bearing performance characteristics of an externally pressurized porous gas bearing without journal rotation is obtained. A good agreement with a similar available solution confirms the validity of the method.
Gas-Lubricated Porous Bearings—Short Journal Bearings, Steady-State Solution
Authors: Wu Erh-Rong , Castelli Vittorio
Published: November 2010

The governing equations for a short porous bearing are derived by adopting Ocvirk’s approximation to the general equations for a finite bearing, which are given in a previous paper (reference [1]). Crank-Nicholson’s numerical method and the analytical-numerical technique, which consists of Green function approximation and the local smoothing by integration for a Fourier series, developed in reference [1] are employed to solve the modified Reynolds equation for a wide range of compressibility number. The solution for a solid-wall bearing is obtained as a special case of a porous bearing. Comparison between two thicknesses of porous layer is included.
Experimental Verification of Thermoelastic Instabilities in Sliding Contact
Authors: Dow T. A. , Stockwell R. D.
Published: November 2010

In the design of sliding seals, uniform loading is often assumed in order to calculate leakage, pressure, and surface temperature. Previous theoretical and experimental evidence has shown that for some material properties and operating conditions, nonuniform contact between the sliding surfaces can result. This nonuniform contact is exhibited as a concentrated region of higher pressure and temperature which moves under the influence of thermal expansion and wear. This paper describes the results of experiments which have been performed to verify the existence of the concentrated loading in a seal configuration. Nonuniform surface contact can be caused by a thermoelastic phenomenon which is a balance between the thermal expansion of the sliding materials and the wear resulting from their interaction. If the effects of thermal expansion are greater than the wear, the load will concentrate to a small region of the nominal contact area. The occurrence of this unstable operation can be written in terms of the critical sliding speed necessary to produce it. Sliding experiments were performed using several different material combinations and the critical speeds were measured. The results of the experiments have been compared with the small perturbation stability analysis published previously. Although the magnitude of the critical speed could not be accurately calculated using the analysis, the results indicated that the relative performance of different material combinations could be predicted.
Friction and Wear of Glass and Carbon Fiber-Filled Thermoplastic Polymers
Authors: Tanaka Kyuichiro
Published: November 2010

Measurements of friction and wear were made on PTFE and polyacetal incorporating glass and carbon fibers. Glass and steel were used as counterface materials. The friction of filled PTFE was generally lower than that of filled polyacetal. The fibers greatly reduced the friction of polyacetal, carbon fibers being more effective in friction reduction than glass fibers. Carbon fiber-filled polyacetal displayed a much lower wear rate than glass fiber-filled polyacetal. The wear rate on glass of fiber-filled polyacetal at lower speeds was much greater than that of unfilled polyacetal. Glass fiber-filled polyacetal also exhibited a greater wear rate on steel than unfilled polyacetal. However, the wear reducing action of both fibers was remarkable in filled polyacetal at high speeds on glass. The frictional surface became fiber rich. Hypotheses for the mechanism of formation of fiber rich surfaces, and the mechanisms of wear increasing and reducing action of the fibers, are discussed.
Measurement of Roller Speed in a Cylindrical Roller Bearing Using a Laser Anemometer
Authors: Goksem P. G. , Fletcher E. J. , Hargreaves R. A.
Published: November 2010

A technique for measuring roller speeds in cylindrical roller bearings using a modified laser anemometer has been developed. The technique described does not require any mechanical interference with the roller and cage geometries, and is suitable for high speed testing. The method has been used to measure roller speeds exceeding 15,000 rpm, in a standard 50 mm nominal bore, flanged inner track cylindrical roller bearing, under the conditions of light loads and lubricant starvation. Considerable cage and roller slip is detected only at radial loads less than 100 N, and the degree of slip present is found to be virtually independent of the low lubricant flow rates used in the investigation.
Analysis of Pneumatic Instability of Externally Pressurized Porous Gas Journal Bearings
Authors: Rao N. S. , Majumdar B. C.
Published: November 2010

A theoretical analysis is presented for the study of pneumatic instability for a rigid rotor supported in externally pressurized porous gas journal bearings. The analysis is based on a first-order perturbation with respect to the amplitude of dynamic displacement of rotor. The variation of threshold mass parameter with feeding parameter is shown. In addition, the effects of supply pressure, eccentricity ratio, L/D ratio, and porosity parameter are investigated and presented in the form of graphs.
Elastohydrodynamic Squeeze Films: Effects of Viscoelasticity and Fluctuating Load
Authors: Rohde S. M. , Whicker D. , Booker J. F.
Published: November 2010

The dynamic responses of squeeze films to fluctuating loads are compared for the cases of rigid, elastic, and viscoelastic bounding surfaces. Unexpected and interesting differences are observed. These include the oscillatory response of indenter position to a non-negative fluctuating load and the decaying load versus time response to a prescribed indenter trajectory which remains constant over a period of time. Practical implications of these responses are noted. The transient analysis procedure, while general, is applied to a simple geometrical and physical model: an isoviscous Newtonian fluid squeezed between circular, initially flat, three-element viscoelastic Winkler solids. Surface deformation rate and film rupture are incorporated. The fully implicit numerical method utilizes a generalized Newton scheme together with finite element spatial discretization.
Stability and Unbalance Response of Centrally Preloaded Rotors Mounted in Journal and Squeeze Film Bearings
Authors: Hahn E. J.
Published: November 2010

The unbalance response and stability of centrally preloaded symmetric rigid rotors are investigated. Steady state solutions for unbalance transmissibilities, orbit eccentricity radii, and stability are presented for rotors running in hydrodynamic journal bearings and in rolling element bearings which are supported in squeeze film bearings. The Ocvirk and Warner approximations are used to evaluate the fluid film forces, rendering the data applicable to any length/diameter ratio. Both pressurized (2π film) and unpressurized (π film) oil supply are considered. Pressurization has a far reaching influence on the steady state behavior of both journal and squeeze film bearings. For unpressurized bearings, conditions of multistable operation and for stability are depicted, with journal bearings exhibiting ‘half frequency whirl’ possibilities as well. The error involved in predicting vertical bearing behavior by assuming an equivalent unidirectional load equal to the unbalance load is demonstrated. For pressurized bearings multistable operation is eliminated but both squeeze film and journal bearings are unstable for most length/diameter ratios in the absence of external radial stiffness. The stabilizing effect of superimposed external radial stiffness on pressurized bearings is clearly demonstrated. While pressurized journal bearings can run stably, they are less suited than pressurized squeeze film bearings for vibration isolation.
Theoretical and Experimental Determination of the Dynamic Characteristics of a Hydrodynamic Journal Bearing
Authors: Parkins D. W.
Published: November 2010

This paper describes a theoretical and experimental investigation into the nonlinear characteristics of the eight coefficients which specify the lateral flexibility of a hydrodynamic journal bearing. Coefficient calculations allowed viscosity to vary with temperature, and pressure, and examined a range of positive and negative displacements and velocities. Experimental techniques have been developed in which coefficients were deduced from specially chosen, imposed vibration orbits arising from two mutually perpendicular external oscillating forces of variable relative magnitude and phase. Journal centre displacement and velocity were measured using high speed data logging equipment. Coefficients are defined in terms of a “zero” value and linear gradient. Using realistic criteria, measured coefficient non-linearity was found to be significant at eccentricity ratios greater than 0.78. Theory adequately predicted some “zero” values but not gradients. An improvement in the coefficient prediction may depend on the inclusion of some previous history dependent factors.
Dynamics of Rolling-Element Bearings—Part II: Cylindrical Roller Bearing Results
Authors: Gupta P. K.
Published: November 2010

Cylindrical roller bearing performance simulations are expressed in terms of the general motion of the bearing elements as derived by integrating the differential equations of motion. Roller skew as induced by relative race misalignment is simulated. It is shown that skidding can be reduced by using a lubricant providing relatively high traction. However, such a fluid results in increased bearing torque and power loss. The influence of geometrical parameters, such as roller/cage, or race/cage clearance and radial preload, on the roller and cage motion is also investigated.
Stiffness of Straight and Tapered Annular Gas Path Seals
Authors: Fleming David P.
Published: November 2010

Radial stiffness of annular (ring-type) gas path seals is calculated for both constant-clearance designs and tapered designs for which the inlet clearance is larger than the outlet clearance. Under some conditions a constant-clearance seal can have a negative stiffness; this undesirable property can be completely eliminated by use of tapered seals. Leakage rates are only moderately higher in tapered seals.
Exact Two-Dimensional Analysis of Circular Disk Spiral Groove Bearing (Part II)
Authors: Murata S. , Miyake Y. , Kawabata N.
Published: November 2010

Two-dimensional pressure field of circular disk grooved thrust bearing when it does three kinds of elementary unsteady motions has been successfully analyzed using potential flow theory. The cancellation of the pressure jump by putting line vortices on the groove-land boundaries is demonstrated to be useful. The analysis of the velocity field can be carried out only in one basic domain, while the pressure field must be calculated in every domain by doing rather complicated selection among infinite number of values of inverse tangent.
A Parametric Study of Journal Bearing Performance: The 80 Deg Partial Arc Bearing
Authors: Suganami T. , Szeri A. Z.
Published: November 2010

The thermohydrodynamic (THD) lubrication model of reference [1], tested and shown to be valid in both laminar and superlaminar flow regimes, is applied here to a series of geometrically similar, but of different size, bearings. The resulting parametric study shows significant thermal effects on both the static and the dynamic performance of the bearings.
Detection of Rolling Element Bearing Damage by Statistical Vibration Analysis
Authors: Dyer D. , Stewart R. M.
Published: November 2010

A new method is presented for predicting rolling element bearing condition from measurements of bearing housing vibration. This method is based on a statistical parameter Kurtosis, that remains constant for an undamaged bearing irrespective of load and speed, yet changes with damage. The extent of damage can be assessed from the distribution of this statistical parameter in selected frequency ranges. An assessment of bearing condition can thus be made with minimum recourse to historical information. Most other damage detection techniques rely heavily on the trend analysis of data and so this new method may prove to be a significant advance in bearing fault detection technology, at least when viewed within the original objective to provide a simple and cheap technique. As with most other simple detection techniques, the precise nature of the fault cannot be defined and for such information it is necessary to use the more sophisticated diagnostic methods.
Design of Clamped Composite-Material Plates to Maximize Fundamental Frequency
Authors: Bert C. W.
Published: November 2010

Methodology and equations are developed for maximizing the fundamental frequency (ωf) of small-amplitude, free flexural vibration of a clamped, rectangular plate consisting of multiple, equal-thickness layers of the same unidirectional filamentary composite material. The synthesis is based on a concise, explicit equation for ωf in terms of plate dimensions, density and the anisotropic flexural and torsional rigidities. The equation is developed in the paper and shown to be quite accurate. Application of the optimization procedure shows that aligned (0 of 90 deg) parallel-ply laminates are the most advantageous. For plate aspect ratios (R) less than unity, 0 deg is optimal, and for R > 1, 90 deg is best. Comparative optimal frequency data are given for plates of three different aspect ratios and constructed of four different filamentary composite materials.
Design Synthesis of a Multi-Speed Machine Tool Gear Transmission Using Multiparameter Optimization
Authors: Osman M. O. M. , Sankar S. , Dukkipati R. V.
Published: November 2010

This paper presents a novel method for the design synthesis of a multi-speed machine tool gear drive using a multi-parameter optimization technique. The method eliminates any complex and tedious algebraic analysis normally required in gear train designs. It requires only the formulation of mesh and speed ratio equations from the geometrical arrangement of the gear drive and the selection of a suitable optimization criterion and constraints. To illustrate the method, the design synthesis of a nine-speed machine tool gear drive is carried out using optimization strategy. The formulation of the optimization criterion is based on (a) minimizing the largest size gears and (b) minimizing the overall size of the gear drive. The method of complex optimization technique is utilized for the design and the optimum values of the gear diameters and the lowest gear ratio Sop are calculated and found to correlate well with those obtained using algebraic methods.
Appreciable Increase in Pitting Limit of Contact Surfaces Under Rolling and Sliding Conditions
Authors: Ishibashi A. , Yokote T. , Yoshino H.
Published: November 2010

This work was conducted to discover the highest pitting limits of the contact surfaces under combined rolling/sliding conditions. Appreciable increases in pitting limits were obtained in rollers with hardnesses in the range 190 to 335 HB using an improved testing machine made by the authors. The allowable contact forces corresponding to the new pitting limits were about four times greater than those corresponding to the earlier pitting limits. Some factors which might prevent appreciable increases in pitting limits were examined and a new experiment was conducted using rollers with a pit-producing ability limited to a small area of less than 0.1 percent of whole contact surface of the rollers. It was found that the local metallic contacts which cause only a slight increase in the friction coefficient can bring about severe pitting failure before 107 rotations.
A Generalized Decomposition Procedure and Its Application to Engineering Design
Authors: Davis W. J.
Published: November 2010

This paper addresses the application of the decomposition theory of mathematical programming to the engineering design process. While decomposition theory does offer a vehicle for solving large mathematical programming problems arising in engineering design, it also provides a framework for modeling the design of engineering systems through the integration of component sybsystems. Based upon this discussion, shortcomings of the present decomposition procedures are related. A new generalized decomposition procedure is then introduced. A linear programming version of the generalized model is developed. Through the application of this model to an example, the solution properties of the model are displayed. Extension of the model to solve a large class of mathematical programming problems is discussed.
The Analytical and Experimental Evaluation of Vibratory Oscillations in Realistically Proportioned Mechanisms
Authors: Sanders J. R. , Tesar D.
Published: November 2010

Deformations in mechanisms composed of link members of realistic proportions and commonly used materials are studied both analytically and experimentally. It is shown that such industrial systems exhibit distortions largely due to the quasi-static application of the cyclically varying inertia forces acting on the links. A four-bar linkage coupler link of five distinct bending rates was strain gauge tested to confirm results predicted by a decoupled vibration study of the same link. The bending spring rates varied from a well proportioned “stiff” link to a very flexible, poorly proportioned “weak” link while the effective mass content was held constant.
Flexural Vibrations of Rotating Electromagnetic Shields
Authors: Shevchuk G. J. , Thullen P.
Published: November 2010

Much interest currently exists in the design and construction of superconducting electrical machines for power generation. All machines of this type include, as part of their rotating member, one or more cylindrical shells. These shells are influenced by elastic, inertial, and electromagnetic forces. Electrical tests on an experimental superconducting alternator at M.I.T. produced unexpected vibrations in one such shell, the electromagnetic shield. The flexural vibrations were in the form of traveling waves, of differing wave speeds, and produced a significant deterioration in shield performance. A simple theoretical analysis of the effects of rotation on the vibrations of long cylinders is presented. These effects are verified over a significant speed range by two experiments as well as data from tests on the experimental alternator. Results are related to the design of electromagnetic shields for superconducting alternators.
Orthotropic Cylindrical Shells Under Dynamic Loading
Authors: Mangrum E. , Burns J. J.
Published: November 2010

An orthotropic right cylindrical shell is analyzed when subjected to a discontinuous, finite length pressure load moving in the axial direction at constant velocity. The analysis utilizes linear, small deflection shell theory which includes transverse shear deformations, and external radial damping. The problem is solved using Fourier transforms. The inverse Fourier integrals are evaluated for the radial deflection, axial deflection and rotation by expanding the characteristic equation in partial fractions. The behavior of load velocity loci is studied for variations in material moduli and thickness to radius ratio. The deflection response is investigated.
Interface Pressure Distribution in a Bolt-Flange Assembly
Authors: Ito Y. , Toyoda J. , Nagata S.
Published: November 2010

The interface pressure distribution of a single bolt-flange assembly was measured for the various surface topographies and the materials of the joint surfaces and also thicknesses of the upper flange by means of ultrasonic waves. The results show that the surface topography, the joint material, and the flange thickness have noticeable influences not only on the form of the interface pressure distribution curve but also upon the effective area of the connecting force. The measured interface pressure distribution and the effective area of the connecting force differ significantly from the analytical values so far presented from the results of theoretical studies using equivalent models with perfect joint surfaces or without joint surfaces.