bluuebunny/crossref_metadata_2025 huggingface dataset:
Solution of Anisotropic Problems of First Class by Coordinate-Transformation
Authors: Poon K. C. , Tsou R. C. H. , Chang Y. P.
Published: November 2010

In an earlier paper, it was suggested to divide heat conduction problems in anisotropic media into three classes for the systematic presentation of their analytical solutions. It is shown in this paper that a large number of the first-class problems governed by differential equations of hyperbolic, parabolic and elliptic types with boundary conditions of the first, second, third and fourth kinds can be transformed into those for isotropic media. Solutions of two illustrative problems are shown while those of more complicated problems will be reported in subsequent papers.
Thin Disk On A Convectively Cooled Plate—Application To Heat Flux Measurement Errors
Authors: Wesley D. A.
Published: November 2010

An analysis is made of the steady-state thermal processes associated with a thin disk affixed to a convectively cooled solid plate. The disk represents a thermopile heat flux gauge. In the first part of the paper, the heat conduction problem of the plate is solved for the simplified condition where the heat flow through the disk is axially one-dimensional. It was found that the local divergence of the heat flux field within the plate owing to the presence of the disk may result in a gauge reading that underestimates the heat transfer rate. Also, a sizeable local plate temperature augmentation can occur. Furthermore, the analysis yields dimensional estimates of the region where the temperature and heat flux fields within the plate are significantly altered by the presence of the disk. An adjunct to the foregoing analysis develops a one-dimensional conduction factor which is useful in determining when the heat flow through the disk can be considered to be axially one-dimensional.
Heated Three-Dimensional Turbulent Jets
Authors: Sforza P. M. , Stasi W.
Published: November 2010

An experimental investigation of heated three-dimensional turbulent free jets is presented. Emphasis is placed on the basic character of such flows and their relation to their unheated counterparts and to heated axisymmetric jets. Temperature and velocity distributions indicate that these flow fields may be characterized by three distinct regions in terms of the axis decays: a potential core region where axis values are close to the exit values, a characteristic decay region wherein the axis decays are dependent upon orifice geometry, and an axisymmetric decay region where the axis decay is axisymmetric in nature and thus independent of orifice geometry. These regions are not exactly the same for temperature as for velocity, the former being shifted somewhat upstream of the latter. Half-width data indicate that heated three-dimensional jets change shape as they proceed downstream, ultimately becoming axisymmetric in nature, regardless of initial orifice shape. Profile characteristics and similarity are discussed as well as cross-plane contours of pertinent flow variables. Some of the effects of initial conditions and exit flow quality on the subsequent development of three-dimensional jets are shown and the sensitivity of such flows to these factors is described.
Response of Building Components to Heating in a Fire
Authors: Kanury A. M. , Holve D. J.
Published: November 2010

This paper deals with the response of building components such as walls, doors, etc. exposed to the severe thermal atmospheres created by accidental fires in structures. The standard fire test ASTM E-119 of the American Society for Testing and Materials, which is used to measure this response, is considered for a theoretical analysis. Only the thermal aspects of the problem are examined. Through dimensional, order-of-magnitude, and phenomenological analyses of the governing equations of an idealized model, a variety of conclusions are drawn. These conclusions are consistent with various successful current fire protection design practices. Deviations of the idealized theoretical model from the practical operating conditions of the actual test are carefully noted for consideration in the future refinements of the analysis.
Effect of Surface Roughness on Heat Transfer from Horizontal Immersed Tubes in a Fluidized Bed
Authors: Grewal N. S. , Saxena S. C.
Published: November 2010

Experimental results of the total heat transfer coefficient between 12.7 mm dia copper tubes with four different rough surfaces and glass beads of three different sizes as taken in a 0.305 m × 0.305 m square fluidized bed as a function of fluidizing velocity are reported. The comparison of results for the rough and technically smooth tubes suggests that the heat transfer coefficient strongly depends on the ratio of pitch (Pf) to the average particle diameter (dp), where Pf is the distance between the two corresponding points on consecutive threads or knurls. By the proper choice of (Pf/dp) ratio, the maximum total heat transfer coefficient for V-thread tubes (hwfb) can be increased by as much as 40 percent over the value for a smooth tube with the same outside diameter. However, for values of (Pf/dp) less than 0.95, the maximum heat transfer coefficient for the V-thread rough tubes is smaller than the smooth tube having the same outside diameter. The qualitative variation of the heat transfer coefficient for rough tubes with (Pf/dp) is explained on the basis of the combined effect of contact geometry between the solid particles and the heat transfer surface, and the solids renewal rate at the surface. The present findings are critically compared with somewhat similar investigations from the literature on the heat transfer from horizontal or vertical rough tubes and tubes with small fins.
Natural Convection in a Ternary Gas Mixture—Application to the Naphthalene Sublimation Technique
Authors: Sparrow E. M. , Niethammer J. E.
Published: November 2010

An analysis is made of natural convection mass transfer in a ternary gas mixture adjacent to a vertical plate. The main feature of the analysis is the proper mathematical description of the buoyancy force and of the boundary conditions. With regard to the latter, account is taken of the selective impermeability of the plate to certain components of the mixture. The governing boundary layer equations are shown to admit a similarity solution, and a numerical scheme for solving the similarity equations and boundary conditions is outlined. The general formulation is specialized to the case of sublimation from a solid, vertically oriented naphthalene plate situated in a humid air environment. Solutions were obtained for temperature levels corresponding to those encountered in practice and for relative humidities of water vapor between zero and one. It was found that the mass transfer results were unaffected by the presence of humidity, and this finding gives license to the utilization of the naphthalene technique without special concern about the humidity level. In addition, the transverse velocity at the plate surface associated with the mass transfer was too small to affect the magnitude of the mass transfer.
Natural Convection in a Multi-Layered Geothermal Reservoir
Authors: Rana R. , Horne R. N. , Cheng P.
Published: November 2010

The effect of layered structure of rock formation on free convection in a geothermal reservoir is investigated in this work. The model examined is that of a rectangular reservoir comprised of three horizontal permeable layers with different permeabilities. The reservoir is considered to be bounded by impermeable surfaces on the sides and at the bottom. The upper boundary of the aquifer is permeable, which permits the recharge and discharge of water to and from the aquifer. A transient two-dimensional convective flow is developed when the impermeable boundaries are raised suddenly to high temperatures. The governing nonlinear partial differential equations with appropriate boundary and initial conditions are solved numerically by finite difference methods. Application of the direct method for solving Poisson’s equation for stream function made it possible to carry out the solution for a much longer time than possible with iterative techniques. Numerical results are obtained for various parameters and configurations of the geothermal reservoir. The influence of a less permeable middle layer on the flow and heat transfer characteristics in the aquifer is discussed. The computed vertical temperature profiles are similar in shape to the complex temperature profiles observed at the HGP-A well.
Investigation of Freezing of Salt Solutions in Cells
Authors: Hayashi Y. , Komori T.
Published: November 2010

Phenomena of salt rejection during freezing process of saline solutions included in cells were investigated analytically and experimentally as a problem of heat and mass transfer with phase change. By experiments of freezing of the aqueous solutions of 2.0–15.0 wt percent sodium chloride, three regions—a solid, a solid-liquid and a liquid—were recognized to coexist together in the freezing process. In the solid-liquid region, when freezing proceeds, freezing fronts were found to occur stepwise within several adjacent cells. This phenomenon was due to the depression of the freezing point which was caused by salt rejection in the cells. Furthermore, the mechanism of the freezing process was clarified in connection with the constitutional supercooling of the solution. The analytical solutions for the freezing problem of saline solutions were obtained by an approximation of using apparent heat capacity involving latent heat of fusion released in the solid-liquid region, and applying the procedure of Newmann’s exact solutions for a semi-infinite body with phase change.
Calculation of Variable Property Turbulent Friction and Heat Transfer in Rough Pipes
Authors: Wassel A. T. , Mills A. F.
Published: November 2010

A numerical calculation method for turbulent flow in rough pipes is developed. A mixing length model is used in the turbulent core while a roughness element drag coefficient and a sub-layer Stanton number are used to characterize transport to the wall. Sample wall relations are developed for sandgrain roughness and transverse repeated rib roughness, and it is shown that large roughness heights require accounting for terms of order of roughness height divided by pipe radius. For gas flows with cooling, the effects of variable properties are investigated for smooth walls and both roughness patterns. For smooth walls, comparison with experiment is satisfactory; for rough walls experimental data is not available. Simple power law formulae representing variable property effects for fully rough flows are presented.
Turbulent Boundary Layer Heat Transfer on Curved Surfaces
Authors: Mayle R. E. , Blair M. F. , Kopper F. C.
Published: November 2010

Heat transfer measurements for a turbulent boundary layer on a convex and concave, constant-temperature surface are presented. The heat transferred on the convex surface was found to be less than that for a flat surface, while the heat transferred to the boundary layer on the concave surface was greater. It was also found that the heat transferred on the convex surface could be determined by using an existing two-dimensional finite difference boundary layer program modified to take into account the effect of streamline curvature on the turbulent shear stress and heat flux, but that the heat transferred on the concave surface could not be calculated. The latter result is attributed to the transition from a two-dimensional flow to one which contained streamwise, Taylor-Go¨rtler type vortices.
Heat Transfer in the Meniscus Thin-Film Transition Region
Authors: Holm F. W. , Goplen S. P.
Published: November 2010

Capillary surface wetting is a passive phenomenon that depends on free surface energies. As heat transfer rates increase, within limits, more liquid flows onto the surface and evaporates. The differential equations describing mass and heat transfer mechanisms have been solved simultaneously for several capillary groove configurations. Further, by methods outlined in this paper, the effects of solid-liquid-vapor interline heat transfer phenomena can be isolated and evaluated. Not only does this provide a method for predicting surface heat transfer coefficients for surfaces wetted through capillary grooves, it also provides basic information about heat transfer in the vicinity of the meniscus attachment region.
A New Similarity Method for Analysis of Multi-Dimensional Solidification
Authors: Shamsundar N. , Srinivasan R.
Published: November 2010

There are many multi-dimensional phase change problems which are of interest in applications but cannot be solved by even the powerful computational techniques that are available today. A new similarity rule is presented in this paper to make the solution of such problems possible. The similarity rule applies to problems in which sensible heat contributions are much smaller than latent heat contributions, and the heat flux distribution on the surface of the phase change substance is more or less uniform. After a derivation of the similarity rule is given, it is verified by application to some problems arising in latent heat storage for which finite-difference computations have been performed previously. The similarity rule is easy to apply, and greatly reduces the effort needed in analysing phase change problems. In conjunction with the energy conservation principle, the similarity rule provides an efficient tool for analysing the time-response of a phase change system to arbitrarily varying heat loads, as is demonstrated by examples.
Further Developments of Dropwise Condensation Theory
Authors: Tanaka H.
Published: November 2010

The high rates of heat transfer of dropwise condensation as well as its limits are explained on the basis of the behaviors of submicroscopic active drops. The expression for the substantial growth rate of a single drop valid down to the thermodynamic critical size is incorporated into a set of basic equations from [8] whose capability to describe the process of coalescence and growth of drops in dropwise condensation has been demonstrated in [9]. Consideration of the nondimensionalized forms of the basic equations with the aid of numerical analysis results in an expression of the Nusselt number for dropwise condensation in terms of a few characteristic parameters. Comparison of the predicted Nusselt numbers with available experimental data suggests that the condensation coefficient of water is around 0.2 provided the nucleation site density is infinitely high. Otherwise, if the condensation coefficient should be unity, we have to accept that the nucleation sites are fairly scattered.
Open-Loop Thermosyphons with Geological Applications
Authors: Torrance K. E.
Published: November 2010

Natural convection flows in open-loop thermosyphons are examined. The thermosyphons are embedded in an impermeable medium which is heated uniformly from below. The thermosyphon loops charge and discharge fluid at a horizontal boundary of the medium. The impermeable medium is of high thermal conductivity and the temperature of both the medium and the thermosyphon walls increases linearly with depth. Analytical and numerical solutions are presented for a range of thermosyphon geometries. Critical Rayleigh numbers for the onset of motion are determined. A maximum exit temperature is found for elliptical-open-loop thermosyphons. Higher exit temperatures require long residence times at depth. Results are applicable to the cooling of porous materials and to hydrothermal circulations in the oceanic and continental crusts.
The Transient and Stability Behavior of a Natural Convection Loop
Authors: Greif R. , Zvirin Y. , Mertol A.
Published: November 2010

A study has been made of the transient flow and energy transfer in a natural convection loop. In particular, a toroidal thermosyphon has been considered with orientation in a vertical plane that is heated over the lower half and cooled in the upper half. The basic conservation equations have been solved and the velocity and temperature distributions have been obtained which elucidate the phenomena in natural convection loops. The results include stable, as well as unstable configurations.
Experimental Study of Evaporation and Breakdown of Thin Liquid Films Driven by Shear Stresses
Authors: Ihnatowicz E. , Gumkowski S. , Mikielewicz J.
Published: November 2010

An experimental investigation of a thin water film driven by steam, its evaporation and breakdown, was carried out. The shear stresses, the main factor influencing the film motion, were calculated as a function of the “blowing parameter”. The influence of the blowing parameter on evaporation and breakdown of the film was investigated. The results obtained are in agreement with a theoretical analysis which included the effects of the evaporating mass stream and of small droplets within the vapor boundary layer.
A Study of Entropy Generation in Fundamental Convective Heat Transfer
Authors: Bejan A.
Published: November 2010

The second law aspects of heat transfer by forced convection are illustrated in terms of four fundamental flow configurations: pipe flow, boundary layer over flat plate, single cylinder in cross-flow, flow in the entrance region of a flat rectangular duct. The interplay between irreversibility due to heat transfer along finite temperature gradients and, on the other hand, irreversibility due to viscous effects is analyzed in detail. The spatial distribution of irreversibility, entropy generation profiles or maps, and those flow features acting as strong sources of irreversibility are presented. It is shown how the flow geometric parameters may be selected in order to minimize the irreversibility associated with a specific convective heat transfer process.
Analysis of the Elastic Contact of a Hollow Ball With a Flat Plate
Authors: Rumbarger J. H. , Herrick R. C. , Eklund P. R.
Published: November 2010

This paper presents the analysis of the stress field in a hollow sphere in the vicinity of the contact area. The sphere is subjected to a normal load applied through a flat plate. The elastic contact shape and extent are developed for a load of 1000 lb applied to a 1-in-dia hollow ball with a 0.08-in-thick wall. Hollow ball shell bending stresses have a significant effect upon the subsurface stress field. Fatigue life estimates for the hollow ball vary significantly depending upon the selection of decisive stress amplitude. Comparison of the maximum value and location of the reversing orthogonal subsurface shear stress with solid ball data according to the Lundberg-Palmgren dynamic life theory predicts a 91.6 percent life reduction for the hollow ball contact. The use of the unidirectional subsurface shear stress results in a prediction of hollow ball contact life over 30 times the solid ball contact life.
Elastohydrodynamic Theory of Spherical Bodies in Normal Approach
Authors: Christensen H.
Published: November 2010

The elastohydrodynamic problem of normal approach of two spherical bodies is studied and the lubrication and elasticity equations governing this type of motion are established. Numerical solutions to the general case accounting for elastic deformation of the bodies and pressure dependent viscosity are presented. It is found that for values of central film thickness that are not too small, the load and relative approach velocity is much more influenced by the increase of viscosity with pressure than by the effects of elastic distortion. Once the separation of the two surfaces becomes small enough, however, the effects of elastic deformation will profoundly influence all aspects of the motion. The transition film thickness HT at which this change takes place is sharply defined and for metallic contacts lubricated with mineral oils quite small, even compared to the surface roughness. Very high pressure—considerably in excess of the Hertzian maximum pressure corresponding to the load—can be generated by the normal approach motion. The maximum value of pressure is generated when film thickness reaches its transition value HT for the load in question. For loads sufficiently large to generate a high enough pressure in the oil film a small increase in load will cause a large increase in maximum pressure. Once the pressure has reached a high enough value it becomes extremely sensitive to a further increase in load.
Load Ratings and Fatigue Life Prediction for Ball and Roller Bearings
Authors: McCool J. I.
Published: November 2010

A review of current rolling bearing load rating and life prediction practices is given, based on the ASA standard method. Experimental results show the existence of life-factors in addition to those encompassed in the ASA standard. A more general rolling contact fatigue theory is sketched but is not yet at a stage where it can be applied to practical life calculations. Therefore a simple generalization of ASA life formulas is proposed for practical use, which accounts for material and environmental variables by multiplicative factors and permits life prediction for any desired reliability using another, tabulated factor.
Simulation of Ball-Bearing Lubrication With a Rolling-Disk Apparatus
Authors: Bell J. C. , Kannel J. W.
Published: November 2010

The validity of experimental simulation of ball-bearing lubrication by a rolling-disk apparatus has been scrutinized mathematically, with specific attention to films generated for thickness measurements by X-rays. Emphasis was given to distinctive ball-bearing features, such as surface slip and related thermal effects alterable by geometric expansion. For a representative ball bearing, rigorous simulation demanded unattainble disk speeds and hampered X-ray measurements of film thickness, but experiments were made feasible through acceptable relaxation of carefully chosen details. Several experiments were performed under fairly severe combinations of load, speed, and temperature. Specific results with a synthetic paraffinic oil under maximum pressure of 200,000 psi at high speeds showed films about 20 microin. thick at 200 F but indicated only about one microin. at 600 F. Even the thin films allowed little surface contact, though they may have increased susceptibility to damage from sliding.
Rolling Friction, IV—Additional Car Wheel Experiments
Authors: Hersey M. D. , Golden P. L.
Published: November 2010

Rolling friction was increased by flange contact and by sand or leather on surfaces. It was but slightly decreased by water. It could be increased by a thick oil film and decreased by a thinner one. Increasing the wheel hardness diminished rolling friction. Roughness raised static resistance with little effect on kinetic.
Resistance Against Cavitation Erosion of 14 Chromium
Steels
Authors: Tichler J. W. , van den Elsen J. B. , de Gee A. W. J.
Published: November 2010

For 14 chromium steels of different composition and structure, cavitation-erosion damage has been studied and interpreted in terms of structure and strength properties. The use of chambered cylindrical specimens ensured a uniform attack from the very beginning of the erosion process and, thus, highly reproducible wear values. As could be expected on the basis of existing evidence, the duration of the incubation period is a function of the initial condition of the surface, as determined by the finishing process. The reciprocal rate of volume loss, occurring during the first steady-state period (which is characterized by a uniform attack of the surface, without formation of deep craters) (Rc), turned out to be a linear function of the “true” tensile strength, measured at maximum load. It does not depend on grain size, structure and elongation properties of the material. On the other hand, the tendency toward the formation of craters in the surface and the ratio Rc/R∼, in which R∼ is the reciprocal rate of volume loss, during the second, and final, steady-state period, are shown to be exclusively determined by structural parameters.
An Experimental Method for Determining Poisson’s Ratio of Elastomers
Authors: Rightmire Glenn K.
Published: November 2010

One of the most important and sensitive parameters defining the characteristic behavior of compliant-surface, fluid-film bearings has been found to be the value of Poisson’s ratio of the elastomer material—a 1 percent variation in ν in the range of common values produces about a 25 percent change in load carrying capacity. Since values of Poisson’s ratio for the common elastomers are unknown with any degree of accuracy, an experimental method has been devised to measure Poisson’s ratio for typical cases to better than four significant figures. This paper describes the method together with an error analysis and typical data from elastomeric samples.
The Validity of Mathematical Solutions for Determining Friction From the Ring Compression Test
Authors: Male Alan T. , DePierre Vincent
Published: November 2010

The ring test has previously been experimentally calibrated for friction studies on the assumption of constant coefficient of friction under metal-working conditions. This investigation has demonstrated that the same experimental results may be used to calibrate the ring test on the assumption of constant interface friction factor. Use of available mathematical solutions, based on the concept of a constant interface friction factor, provides a possible means for the calibration of different initial ring geometries by computer solution. Excellent correlation has been shown between the shape of calculated curves and experimental ring test results on a wide variety of materials. However, the actual values of m obtained by using the theory to analyze experimentally determined shape changes appear to be somewhat in error to a degree depending on the initial specimen geometry and the general friction level under which it is deformed. This is due essentially to the assumption used in the theoretical treatment, that the surface frictional stresses are transmitted uniformly throughout the specimen thickness, not being generally valid in the practical situation except with very thin specimens.
Conditions for the Rupture of a Lubricating Film. Part I: Theoretical Model
Authors: Coyne J. C. , Elrod H. G.
Published: November 2010

The shape of the film-vapor interface is found for a thin liquid film separating from a stationary surface and being swept away on an opposing moving surface. The analysis is for two-dimensional Newtonian flow, and includes the effects of gravity, inertia, and surface tension. The principal assumption is that of a quadratic tangential velocity distribution across the film. The solution shows that the entire separation phenomenon is completed in a distance of about one plate clearance from the stagnation point. Stagnation points occur on the vapor-liquid interface at the separation point and at a film height of 3h∞ (three times the film height on the moving plate far downstream). For a fixed separation height, the asymptotic film thickness h∞ is shown as a function of three dimensionless parameters. The results are in good agreement with published experimental data.
On the Influence of Inertia Forces in Turbulent and Laminar Self-Acting Films
Authors: Constantinescu V. N.
Published: November 2010

A method is given for determining the motion in a fluid film including inertia forces. The method is developed for infinitely long bearings and can be used for both laminar and turbulent flows, as well as for incompressible and compressible lubricants. The obtained results show that for steady films, convective inertia forces lead basically to Bernoulli effects, while for unsteady films inertia forces may influence both damping and stiffness characteristics of the bearing. At the same time it is pointed out that when Bernoulli effects are important, similar effects may occur in the inlet region of the film. A generalization of the method for bearings of finite dimensions is also given.
The Measurement of Friction and Friction-Induced Vibration
Authors: Ko P. L. , Brockley C. A.
Published: November 2010

The design, development, and application of a pin-on-disk tribometer for the measurement of friction and friction-induced vibration is described. Careful isolation techniques eliminated many of the errors in measurement which are associated with vibration arising from the apparatus or the surroundings. The use of acceleration, velocity, and displacement transducers in association with a one-cycle sequence triggering circuit and other electronic devices permitted the accurate measurement of kinetic friction forces in the presence of friction-induced vibration.
A Theoretical Study of the Dynamic Behavior of Foil Bearings
Authors: Barnum T. B. , Elrod H. G.
Published: November 2010

The differential equations and boundary conditions for the problem of a foil bearing subjected to small variations in tape tension are developed. The numerical results show that the fluctuations of the foil are a function or the frequency parameter ω* = 2r0ωε1/3H0*/U and of the compressibility factor θ = T0/par0.
Measurement of the Dynamic Characteristics of a Large Sleeve Bearing
Authors: Morton P. G.
Published: November 2010

The contribution of fluid lubricated bearings to the unstable whirl and “critical speeds” of any rotor system can be expressed in terms of certain linearized coefficients. The most important of these coefficients are those relating to vertical and horizontal translation of the journal relative to the bearing bush. Much work has been done on the theoretical derivation of these eight coefficients for hydrodynamically lubricated bearings, but there has been no published work on their direct experimental determination in the case of large turbo-type bearings. The paper describes the design and operation of a rig capable of measuring the dynamic oil film characteristics for bearings up to 28 in. dia running at speeds up to 4000 rpm. Coefficients measured on a 20-in.-dia bearing running in the laminar regime are compared with computed coefficients. Both theoretical and experimental coefficients are used to predict the dynamic characteristics of several large turbogenerator rotors running under test conditions on bearings of similar geometry. It is shown that predictions based on current theory considerably underestimate the stability and overestimate the stiffness of the test bearing.
Evaluation of Electron-Beam Welded Hollow Balls for High-Speed Ball Bearings
Authors: Coe Harold H. , Parker Richard J. , Scibbe Herbert W.
Published: November 2010

An experimental investigation was performed with two series (115 and 215) of 75 mm bore ball bearings using hollow balls as the rolling elements. The bearings were tested at 500 and 1000 pounds thrust loads at shaft speeds up to 24000 rpm. The 115 series bearings with 1/2-in. SAE 52100 steel balls showed very little difference in torque, outer-race temperature, or rolling-element fatigue life when compared to similar data for a solid ball bearing. The 215 series bearings with 11/16-in. AISI M-50 steel balls showed only slight differences in torque and outer-race temperature but a very significant decrease in rolling-element fatigue life compared to a solid ball bearing. The balls failed in flexure fatigue, due to a stress concentration in the weld area.
An Isothermal Hydrodynamic Lubrication Theory for Hydrostatic Extrusion and Drawing Processes With Conical Dies
Authors: Wilson W. R. D. , Walowit J. A.
Published: November 2010

A hydrodynamic lubrication theory is developed for a generalized hydrostatic extrusion and drawing process with augmentation and back pressure. The die is assumed to be conical and uniform deformation and isothermal lubrication conditions are assumed to exist. The theory is in good agreement with experimental data previously published by other workers.
Optimization of Clearance in a Squeeze-Film Journal Bearing
Authors: Strodtman C. L.
Published: November 2010

It is shown that a squeeze-film journal bearing supporting a mass completely contained within the bearing can be designed with the optimum value of minimum clearance by proper selection of the drive amplitude to nominal clearance ratio, the length to diameter ratio, and the shape factor of the excursion. Both a small parameter and an augmented, small parameter analysis are given. In the latter case, numerical methods are employed to solve the resulting equations. The results of the analysis are illustrated in application to an accelerometer design.
Dynamics of Air-Lubricated Slider Bearings for Noncontact Magnetic Recording
Authors: Tang T.
Published: November 2010

One of the key technologies which led to the success of modern magnetic disk storage devices is the development of self acting gas lubricated slider bearings for positioning a magnetic head precisely over a high speed rotating recording disk. This paper covers a dynamic simulation of such an air bearing system used in direct access disk storage devices. In the simulation model, the Reynolds equation, which describes the dynamics of the lubricating air film, is solved by finite difference techniques in two dimensions and time for compressible, isothermal flow. The equations of motion of the slider bearing are solved simultaneously with the Reynolds equation for three degrees of freedom. Applications of the simulation are demonstrated, and experimental measurements to verify the theory are presented and discussed.
Speed Effects in Forging Lubrication
Authors: Wallace P. W. , Schey J. A.
Published: November 2010

The effect of forging speed on the efficiency of selected solid and liquid lubricants was investigated by the axial upsetting of 0.45 percent C steel cylinders and rings at 2000 deg F, at press (30–500 in./min), and at hammer (28–40 ft/sec) speeds. Increasing speed reduced friction both in the unlubricated state and with lubricants capable of forming hydrodynamic (squeeze) films. Carrier fluids used for the application of solid lubricants such as graphite were effective when contact time was kept short enough to prevent their evaporation; residues of a mineral oil carrier appeared to impair the effectiveness of graphite. Squeeze films were most marked with glassy lubricants and caused anomalous material flow by the formation of an immobile lubricant wedge. In general, speed and the condition of the carrier at the moment of deformation were found to be the primary variables that determined the relative performance of forging lubricants.
The Hydrodynamic Lubrication of Rough Bearing Surfaces of Finite Width
Authors: Christensen H. , Tonder K.
Published: November 2010

The paper describes a theoretical analysis of the effects of surface roughness in a finite width bearing. The analysis is based upon a stochastic theory of hydrodynamic lubrication developed previously. It is shown how the effect of surface roughness on the bearing characteristics is closely tied up with features of nominal geometry as well as with operational factors.
A Thermal Elastohydrodynamic Theory for Individual Asperity-Asperity Collisions
Authors: Fowles P. E.
Published: November 2010

A thermal elastohydrodynamic theory is developed for the collision between two idealized asperities on surfaces in sliding contact. Numerical solutions are obtained for the pressure, temperature, and film thickness between the asperities as functions of their overlap, the sliding speed, and the time since the initiation of the collision for a given lubricant and asperity geometry. It is shown that extremely high pressures, temperatures, and surface shear stresses are to be expected at the center of the contact region. The tractions generated are shown to be of the same order as the load capacities. At the higher sliding speeds, overlapping asperities may pass over each other, separated at all times by a finite lubricant film. At the lower sliding speeds, boundary processes must take over before the completion of the collision.
The Effect of Atmospheric Environment on the Wear Properties of Filled TFE Materials
Authors: Fuchsluger J. H. , Taber R. D.
Published: November 2010

A bench type wear test was used to study the wear characteristics of several basic filled TFE materials in air and in nitrogen atmospheres containing various amounts of moisture. Test results show that the atmospheric environment and the amount of moisture both influence the wear characteristics of filled TFE materials. In particular, environmental conditions are shown to have a direct effect on the mode of wear experienced; that is, whether or not a lubricating film is created on the rubbing surface. This work emphasizes the need for care in selecting the proper filled TFE composition for given environmental conditions.
Analytical Studies of Contact of Nominally Flat Surfaces; Effect of Previous Loading
Authors: Mikic B.
Published: November 2010

This work analytically investigates effect of previous loading on contact area, number of contact prints, their size distribution, and the value of thermal contact conductance for two nominally flat surfaces in contact. The model used in the analysis assumes that the surfaces are Gaussian and that in the first loading deformation of the surface asperities is plastic.
Slip and Cage Forces in a High-Speed Roller Bearing
Authors: Poplawski J. V.
Published: November 2010

A roller bearing model, which includes the effects of full film lubrication at the race contacts, was developed for use in estimating cage slip, roller slip, film thickness, and cage forces for a given bearing geometry and operating condition. The model includes churning loss, cage pilot surface friction, roller pocket friction, cage unbalance as well as the drag due to the unloaded rolling elements. Roller skew and misalignment have been neglected, however these effects could be introduced if desired. The description of the lubricant film thickness, traction, and pressure forces are based upon assumptions introduced by Dowson, which reduce the complex numerical procedure required for a rigorous solution to the isothermal elastohydrodynamics problem to a set of nonlinear equations. A parametric study on a 1907 basic roller bearing is included to illustrate the use of such a model as a design tool.
Rolling-Element Fatigue Lives of Through-Hardened Bearing Materials
Authors: Parker R. J. , Zaretsky E. V.
Published: November 2010

Rolling-element fatigue tests were run with eight through-hardened bearing materials at 150 deg F. One-half in. dia balls of each material were run in five-ball fatigue testers. Care was taken to maintain constant all variables known to affect rolling-element fatigue life. The longest lives at 150 deg F were obtained with AISI 52100. Ten-percent lives of the other materials ranged from 7 to 78 percent of that obtained with 52100. A trend is indicated toward decreased rolling-element fatigue life with increased total weight percent of alloying elements. Three groups of 120-mm bore ball bearings made from AISI M-1, AISI M-50, and WB-49 were fatigue tested at an outer-race temperature of 600 deg F. The 10-percent lives of the M-50 and M-1 bearings exceeded the calculated AFBMA life by factors of 13 and 6, respectively. The bearings with WB-49 races showed lives less than AFBMA life. The results of the bearing tests at 600 deg F correlate well with the results of the five-ball fatigue data at 150 deg F.
The Effect of Misalignment on the Fatigue Life of Tapered Roller Bearings
Authors: Zantopulos H.
Published: November 2010

A comprehensive analytical and experimental study of the effect of misalignment on load distribution and fatigue life of tapered roller bearings is presented. Included are the effects of truncation of crowned rollers and edge of contact stresses. Bearing life tests, involving approximately 500 bearings, were run at various loads and misalignments to obtain sufficient test data to substantiate the analytical results.
Some Considerations on Characteristics of Static Friction of Machine Tool Slideway
Authors: Kato S. , Sato N. , Matsubayashi T.
Published: November 2010

The fundamental characteristics of “stick-slip” motion in a machine tool slideway is ascertained experimentally, and it is clarified that the time-dependence of static friction has a great influence on the behavior of the stick-slip motion. An empirical formula is proposed to express the characteristics of static friction and the mechanism of the time-dependence of static friction is examined experimentally and theoretically. The influence of properties of lubricants and surface topography on the static friction is investigated quantitatively. Finally, a general conception to prevent stick-slip motion is offered.
Flow Between Eccentric Rotating Cylinders
Authors: DiPrima R. C. , Stuart J. T.
Published: November 2010

The flow between eccentric rotating cylinders is studied using a modified bipolar coordinate system. The Sommerfeld pressure distribution and associated flow in a journal bearing are derived from the Navier-Stokes equations by a straightforward and systematic expansion in the clearance ratio (assumed small). First order corrections for curvature and inertial effects are given. There is no restriction on the eccentricity.
On the General Solution of Externally Pressurized Gas Journal Bearings
Authors: Majumdar B. C.
Published: November 2010

Theoretical and experimental studies of externally pressurized gas bearings with multiple supply pressure sources have been made. The solution is obtained for finite journal bearings considering both axial and circumferential flow components. Experimental evidences show the validity of the method.
An Application of Pneumatic Phase Shifting to Stabilization of Externally Pressurized Journal Gas Bearings
Authors: Mori A. , Mori H.
Published: November 2010

Pneumatic phase shifting is studied as a means for self-excited whirl stabilizations in externally pressurized journal gas-bearings. The pneumatic phase shifting stabilizer is composed of several pairs of pneumatic capacitors and restrictors. The stabilizer in this study utilizes negative capacitor pressure instead of positive capacitor pressure as in the case of the Sixsmith design.
The Hydrodynamic Lubrication of Rough Journal Bearings
Authors: Christensen H. , Tonder K.
Published: November 2010

In a number of previous papers a hydrodynamic theory of lubrication of rough bearing surfaces has been developed. The present paper describes the application of this theory to the analysis of the full journal bearing of finite width. The analysis demonstrates how the roughness influences the characteristics of the bearing and also shows how roughness interacts with features of nominal geometry and operating factors to determine the bearing response.
Theoretical Investigation of Externally Pressurized Gas-Lubricated Porous Journal Bearing With Surface-Loading Effect
Authors: Mori H. , Yabe H.
Published: November 2010

Externally pressurized porous journal gas bearing is analyzed theoretically in this paper by introducing a flow model, in which the flow in the porous bushing is substituted by a flow in an assumed thin layer. The surface loading effect due to machining is taken into account as the increase of resistance to the gas flow from porous media to bearing clearance. The theoretical results are investigated experimentally, yielding a comparatively good conformity between them enough to certify the analysis. Then, the optimum design conditions of the externally pressurized porous journal gas bearing are obtained by theoretical calculations with considering the surface-loading effect.
A New Criterion for Predicting Rolling-Element Fatigue Lives of Through-Hardened Steels
Authors: Chevalier J. L. , Zaretsky E. V. , Parker R. J.
Published: November 2010

A carbide factor was derived based upon a statistical analysis which related rolling-element fatigue life to the total number of residual carbide particles per unit area, median residual carbide size, and percent residual carbide area. An equation was empirically determined which predicts material hardness as a function of temperature. The limiting temperatures of all of the materials studied were dependent on initial room temperature hardness and tempering temperature. An equation was derived combining the effects of material hardness, carbide factor, and bearing temperature to predict rolling-element bearing life.
The Elastohydrodynamic Lubrication of a Thin Layer
Authors: Conway H. D. , Engel P. A.
Published: November 2010

The elastohydrodynamic lubrication problem of a thin elastic layer pressed between two cylinders which rotate in opposite directions is discussed. The analysis leads to an integro-differential equation for the film thickness, subject to an integral constraint. Numerical results are given for both the isoviscous and variable viscosity cases.
Some Observations of the Relationship Between Film Thickness and Load in High Hertz Pressure Sliding Elastohydrodynamic Contacts
Authors: Lee D. , Sanborn D. M. , Winer W. O.
Published: November 2010

The dependence of film thickness on Hertz pressure at pressure levels typical of design applications has been investigated. The data presented by investigators at NASA and Battelle using an X-ray transmission technique showing a dependence much greater than that indicated by commonly accepted theories are substantiated by an independent study using an optical interference film thickness measurement technique. It is also shown that the minimum film thickness is influenced to a much greater extent by the Hertz pressure than the center line film thickness.
A Hero-Jet Driven Porous Spherical Hydrostatic Gas Bearing Gyro
Authors: Gu A. L. , Walowit J. A. , Wilcock D. F.
Published: November 2010

The gyro system under consideration consists of a hollow porous sphere supported in a hydrostatic gas-lubricated spherical bearing. High pressure gas leaking into the sphere through the pores from the bearing film pressurizes the inside of the sphere and is exhausted from a series of Hero jets located around the equator to counter the viscous drag from the bearing and maintain a constant speed. Analysis has been presented for predicting equilibrium speed, flow rates, and stiffness for axisymmetric condition as a function of various dimensionless system parameters representing porosity, drive nozzles, inlet feeding holes, supply pressure, etc. Effects of the various system parameters on the performance of the gyro are illustrated. A preliminary feasibility study has been made for a wide angle and a narrow angle bearing. It is found that the small angle bearing is less subject to lock-up without significant loss of stiffness, but suffers from a lower speed and a less efficient gas utilization. A particular design will represent a compromise between stiffness and speed.
Effect of Slip-Flow in Narrow Porous Bearings
Authors: Murti P. R. K.
Published: November 2010

The experimental work of Beavers, et al., established that velocity slip takes place over a permeable boundary. The presence of slip flow is taken into account while deriving the appropriate modified Reynolds equation that governs the flow of lubricant in a finite porous bearing. The performance of a thin-walled bearing is then analyzed making use of the narrow bearing approximation. It is found that slip flow adversely affects the load capacity and reduces the friction force on the journal; the attitude angle, however, is not significantly affected. Also the analysis indicates that the effects of velocity slip are prominent when the bearing operates at a lower eccentricity ratio and/or the bearing-matrix has a low permeability.
Flow Transition Criteria in a Journal Bearing
Authors: Freˆne J. , Godet M.
Published: November 2010

High speed Couette type flow was studied for small clearance ratios (C/R = 0.0055 and 0.0031). Water flow pattern visualiszations and torque measurements were performed. Results show that Taylor vortices occur at values predicted by theory, they precede turbulence effects and cause an increase in torque which depends on the clearance ratio. Transition between vortex and turbulent flow is gradual and appears to depend on the Taylor number. Taylor vortices can be found in plain bearings.