bluuebunny/crossref_metadata_2025 huggingface dataset:
An Initial Appraisal of the Contact Fatigue Strength of Electron Beam Melted Bearing Steel
Authors: Widner R. L.
Published: November 2010

Three test groups of 2.75 in. bore tapered roller bearings were manufactured from pilot heats of cold hearth electron beam remelted modified 4620 steel, a heat of standard consumable electrode vacuum remelted (CV) 4620 steel and from conventionally melted modified 4620 bearing steel. Bearing life tests were performed in a synthetic fluid and two mineral oils of different viscosity to determine the contact fatigue strength of the electron beam melted steel as compared to the CV steel and conventional steel. The electron beam and the consumable vacuum melted steel had equivalent contact fatigue strength in this initial appraisal. The CV steel had contact fatigue strength 4.5 to 9.8 times better than the conventional bearing steel.
The Optimum Slider Bearing in Terms of Friction
Authors: Rohde S. M.
Published: November 2010

The film profile which minimizes the coefficient of friction and the film profile which minimizes the total friction force for a given load for a one-dimensional slider bearing are determined using a variational method. The lubricant is assumed to be incompressible and of constant viscosity. The flow is assumed to be laminar, and the optimization in the first case is based upon an assumed minimum film thickness. It is shown by the use of the nonlocal variational formulation that these profiles do yield a minimum among all admissible profiles.
Gas Flow Through Trapezoidal Microgaps
Authors: Rieder W. G. , Haworth D. R.
Published: November 2010

A generalized approach based on a model of the Boltzmann equation is suggested for predicting velocity profiles and gas flow rates through trapezoidal microgaps. Sample results are given for selected trapezoidal, rectangular, square, and circular cross section passages for Knudsen numbers ranging from 0.1 to about 10. Comparison of predicted flow rates for rectangular passages with available empirical data seems to indicate that where passage size is characterized by a single dimension, a simple across-channel measurement is inappropriate. While relative velocity profiles are independent of this value, flow rates are not. Accuracy of predictions may be enhanced by matching with analytical or empirical results for similar geometries of larger size. A flow rate from the low Knudsen number end of the transition regime is matched with one from the overlapping region of the slip-flow regime and an arbitrary adjustment is made in the characterization of passage size. This adjustment can then be incorporated into the results throughout the transition regime.
Optimal Speed Sharing Characteristics of a Series-Hybrid Bearing
Authors: Nypan L. J. , Scibbe H. W. , Hamrock B. J.
Published: November 2010

A series-hybrid bearing assembly consisting of a conical hydrostatic fluid-film bearing and a ball bearing is described. Computer studies are used to predict friction torque and life characteristics of a 150-millimeter ball bearing. A conical hydrostatic fluid-film bearing is designed for minimum friction and maximum speed reduction of the ball-bearing component of the series-hybrid bearing. At a thrust load of 4000 lb and speeds corresponding to DN (bearing bore in millimeters times shaft speed in rpm) values of 3 and 4 million, ball-bearing speed may be reduced by 30 percent. This speed reduction corresponds to ball-bearing fatigue life improvement factors of 3.4 at 3 million DN and 5.9 at 4 million DN. An oil flow rate at 18.2 lb per min is required to maintain a fluid-film thickness of 0.001 in. in the hydrostatic bearing.
The Friction of Boron Carbide in Controlled Atmospheres
Authors: Childs T. H. C.
Published: November 2010

Experiments on the sliding of boron carbide on boron carbide in atmospheres of dry air and water vapor at room temperature have shown the frictional behavior of boron carbide to be similar to that of graphite. As boron carbide has not a lamellar structure this is surprising. Electron diffraction studies have shown that the surface of the boron carbide probably contained graphite, thus explaining the frictional behavior.
Dynamic Stability of Gimbaled Spiral-Grooved Thrust Bearing
Authors: Gu A. , Pan C. H. T. , Badgley R. H.
Published: November 2010

A general, easily implemented technique is developed by which stability maps may be determined for gimbaled, gas-lubricated, spiral-grooved thrust bearings. This technique is based upon the spectral analysis (frequency domain) method in which the neutrally stable states of the stator-gimbal system are determined through solution of the system’s characteristic equations. The method has proven effective for conducting low-cost investigations of the sensitivity of system instability thresholds to changes in various system design parameters. Containing data valid for a wide range of gimbal inertias, stability maps are presented for a range of bearing compressibility numbers, for several bearing geometries, and for several values of mechanical damping in order to illustrate both the power of the technique and also its effectiveness. Limited experimental information which is presently available verified the essential features of the corresponding stability maps. The technique has been reduced to a form usable in the design of gas bearings for use in gas turbine engines.
Shear Stresses Below Asperities in Hertzian Contact as Measured by Photoelasticity
Authors: Leibensperger R. L. , Brittain T. M.
Published: November 2010

The effect of surface roughness on shear stresses below the surface of an unlubricated Hertzian contact is analyzed using a three dimensional stress freezing photoelastic technique. The shear stresses in the micro-Hertzian contact in each asperity are shown to combine and form, at a greater depth below the surface, shear stresses generally associated with contact stress theory. These macro-Hertzian stresses are compared with the micro-Hertzian stresses in the asperities. The results are also correlated with an existing asperity contact theory and are discussed in relation to the contact fatigue phenomenon.
An Experimental Study and Analysis of Turbulent Film Tilted Pad Bearings
Authors: Burton R. A. , Carper H. J. , Hsu Y. C.
Published: November 2010

Velocity profiles and pressure distributions are reported for turbulent flow under tilted pads in a large scale bearing model (6-ft shaft size, with air as the working fluid). Results are extended analytically to other bearing sizes and aspect ratios.
Gas-Lubricated Foil Bearings for High Speed Turboalternator—Construction and Performance
Authors: Licht L. , Branger M. , Anderson W. J.
Published: November 2010

Foil bearings were designed and fabricated to replace pivoted-shoe journal bearings in a Brayton cycle turboalternator, within space limitations and constraints imposed by the existing machine. The foil bearings were integrated into a unified assembly with the rotor, housing, seals, and gimbal-mounted thrust bearing, without changes and modifications of machine components other than the journal bearings. The gas-lubricated foil bearings, which require no external pressure-source, furnished a stable support for a 21.9 pound rotor in the vertical attitude at speeds to 43,200 rpm. Excellent wipe-wear characteristics permitted well over 1000 start-stop cycles, without deterioration of performance in the entire speed range. The paper reviews salient aspects of design, fabrication, and performance. An account is given of rotor dynamics during starting, stopping, and traversing the region of resonances. The state of journal and foil surfaces is examined following intensive start-stop cycling and high-speed runs over extended periods of time.
Experimental Evaluation of 150-Millimeter Bore Ball Bearings to 3-Million DN Using Either Solid or Drilled Balls
Authors: Scibbe H. W. , Munson H. E.
Published: November 2010

Seven 150-mm bore ball bearings were run under 8900 Newton (2000 lb) thrust load at speeds from 6670 to 20,000 rpm (1 to 3 million DN). Four of the bearings had conventional solid balls and three bearings had drilled (cylindrically hollow) balls with 50 percent mass reduction. The bearings were under-race cooled and slot-lubricated with type II ester oil at flow rates from 4.35 to 5.80 liters per min (1.15 to 1.57 gal/min). Friction torque and temperatures were measured on all bearings. While there was considerable spread in the temperature data, the drilled ball bearings tended to run slightly cooler at higher speeds. No significant difference in torque was noted, between the solid and drilled ball bearings. One bearing of each type was rerun at 17,800 Newtons (4000 lb) thrust load. The solid ball bearings performed satisfactorily at 3 million DN. However, at about 2 million DN the drilled ball bearing experienced a broken ball and cracks appeared in two other balls as the result of flexure fatigue. Metallurgical examination of the cracked balls indicated a brittle structure in the bore of the drilled balls.
Labyrinth Seal Literature Survey
Authors: Sneck H. J.
Published: November 2010

A survey of the important published papers pertaining to labyrinth seals. A discussion of the present state-of-the-art of labyrinth seal theory and design from a thermodynamic and fluid mechanic viewpoint.
The Use of Hydrostatic Thrust Bearing in Flow and Temperature Measurements
Authors: Morsi S. A.
Published: November 2010

This paper describes two new applications for the hydrostatic thrust bearing. The first application is the use of the bearing, when the gap is fixed, as a linear constant resistance. Several bearings have been connected together in parallel to obtain large flow rates at small pressure drops for use as a flowmeter. The second application is the use of a bearing, when modified, as a temperature sensor. Description and performance of this modified design when used as a temperature sensor are given.
Nondimensional Presentation of Frictional Tractions in Elastohydrodynamic Lubrication—Part I: Fully Flooded Conditions
Authors: Archard J. F. , Baglin K. P.
Published: November 2010

Using several sources, analytic and semi-analytic solutions for frictional tractions of a lubricated line contact are presented in the appropriate non-dimensional form which is similar to that previously used by Moes for film thickness. A Newtonian lubricant with an exponential relationship between viscosity and pressure is assumed and, at this stage, the treatment is confined to fully flooded conditions. The components of frictional tractions arising from rolling (Poisseiulle) and sliding (Couette) flows are distinguished and sliding tractions in the outlet cavitated region are separated from those in the main pressure zone. Three main regimes of lubrication are studied: classical (isoviscous, undeformed), low elastic modulus (isoviscous, heavily deformed) and high elastic modulus (pressure dependent viscosity, heavily deformed). The results presented here provide a broad background of approximate results, covering a very wide range of conditions against which the results of more precise computer-based analyses can be judged. Thus the treatment reveals the existence of a range of conditions (typical of the lubrication of glassy polymers by hydrocarbon lubricants) which has been little studied and is, as yet, imperfectly understood.
Nondimensional Presentation of Frictional Tractions in Elastohydrodynamic Lubrication—Part II: Starved Conditions
Authors: Archard J. F. , Baglin K. P.
Published: November 2010

Part I of this paper presented a broad semi-analytic treatment of frictional tractions in nondimensional terms; this was confined to the fully flooded situation and the present paper extends the analysis to include starved conditions. As in Part I three major conditions are considered in detail: classical (isoviscous, undeformed) low elastic modulus (isoviscous, heavily deformed) and high elastic modulus (pressure dependent viscosity, heavily deformed). The influence of starvation is presented as a series of correction curves for the rolling and sliding friction derived for fully flooded conditions. Starvation influences friction both through the extent to which the gap between the surfaces is filled by lubricant and through its influence upon the film thickness. Both factors affect rolling friction which is therefore markedly reduced by starvation so mild that there is negligible influence upon the film thickness. In contrast, sliding friction (arising either in the main pressure zone or the cavitated region) is most strongly influenced by the film thickness and is therefore markedly affected only by relatively severe starvation.
Performance of Hydrostatic Spherical Gas Gyro Bearings
Authors: Gu A. , Cziglenyi L.
Published: November 2010

Analysis and method of numerical solution for evaluating the performance of hydrostatic spherical gas gyro bearings at any gimbal angle and at any eccentricity have been developed. Performance data on load capacity, gas flow rate, drag torque, and error torque over some ranges of gimbal angle and eccentricity are presented. Comparison has been made between the equatorially vented and nonvented bearings of fixed bearing angles.
The Effect of Surface Roughness on the Average Film Thickness Between Lubricated Rollers
Authors: Chow L. S. H. , Cheng H. S.
Published: November 2010

The Christensen theory of stochastic models [7] for hydrodynamic lubrication of rough surfaces is extended to elastohydrodynamic lubrication between two rollers. The Grubin-type equation including asperity effects in the inlet region is derived. Solutions for the reduced pressure at the entrance as a function of the ratio of the average nominal film thickness to the r.m.s. surface roughness (in terms of standard deviation σ), have been obtained numerically. Results were obtained for purely transverse as well as purely longitudinal surface roughness for cases with or without slip. The reduced pressure is shown to decrease slightly by considering longitudinal surface roughness. The transverse surface roughness, on the other hand, has a slight beneficial effect on the average film thickess at the inlet. The same approach was used to study the effect of surface roughness on lubrication between rigid rollers and lubrication of an infinitely-wide slider bearing. Results of these two cases show that the effects of surface roughness are similar to those found in elastohydrodynamic contacts.
Operating Limitations of High-Speed Jet-Lubricated Ball Bearings
Authors: Zaretsky E. V. , Signer H. , Bamberger E. N.
Published: November 2010

A parametric study was performed with 120-mm bore angular-contact ball bearings having a nominal contact angle of 20 deg. The bearings either had an inner- or an outer-race land riding cage. Lubrication was by recirculating oil jets. The oil jets either had a single or dual orifice. Thrust load, speed, and lubricant flow rate were varied. Test results were compared with those previously reported and obtained from bearings of the same design which were under-race lubricated but run under the same conditions. Jet lubricated ball bearings were limited to speeds less than 2.5 × 106 DN. Bearings having inner-race land riding cages produced lower temperatures than bearings with outer-race land riding cages. For a given lubricant flow rate dual orifice jets produced lower bearing temperatures than single orifice jets. However, under-race lubrication produced under all conditions of operation lower bearing temperatures with no apparent bearing speed limitation.
Performance Characteristics of Tilting Pad Thrust Bearings at High Operating Speeds
Authors: Capitao J. W.
Published: November 2010

A full scale experimental program was conducted to investigate the influence of fluid film turbulence on the performance of the tilting-pad, self-equalizing type thrust bearing. Test results include data on centrally pivoted, 6-pad, 381-mm (15-in.) and 432-mm (17-in.) O.D. bearings operating with shaft speeds up to 10000 rpm and bearing loads ranging up to 3.447 MPa (500 psi). Data collected include bearing metal temperatures, bearing power loss, and observation of the laminar to turbulent transition range.
An Experimental Investigation of a Tilting-Pad, Compliant-Surface, Thrust Bearing
Authors: Rightmire Glenn K. , Castelli Vittorio , Fuller Dudley D.
Published: November 2010

Results are provided for an investigation of a compliant-surface, tilting-shoe bearing, when operating in oil. Two values of elastomer durometer were used on shoes as well as seven different pivot locations. The investigation included measurements of lubricant film pressure fields and film-thickness profiles under the shoes during operation. Friction and overall stiffness were also recorded for a typical range of speeds, loads, and pivot positions.
An Experimental Investigation of Cylindrical Roller Bearings Having Annular Rollers
Authors: Suzuki A. , Seireg A.
Published: November 2010

This study deals with an experimental investigation of a cylindrical roller bearing having annular rollers. Comparisons are made with a solid roller bearing having the same configuration and dimensions. Radial deformations and load distribution between rollers are measured under static load and compared with numerical solutions. Bearing temperature rise and roller wear are investigated in a specially designed tester. A radioactive tracing technique is utilized for the measurement of roller wear and proved to be reliable for wear detection. The results show several advantages of annular rollers over the solid rollers.
Traction Characteristics of a MIL-L-7808 Oil
Authors: Walowit J. A. , Smith R. L.
Published: November 2010

Traction versus slip curves for a full matrix of loads, speeds, and temperatures are given for one MIL-L-7808. Hertzian contact pressures from 80,000 psi (551.6 MN/m2) to 150,000 psi (1034.2 MN/m2), speeds from 900 ips (22.9 m/s) to 1,820 ips (46.2 m/s), and temperatures from 75°F (23.9°C) to 160°F (71.1°C) are the test matrix limits of variation. Slip speeds up to 10 percent of the rolling speeds are shown for the full matrix test range.
The Transport and Breakdown of Solid Lubricants in a Simple Forging Operation
Authors: Wilson W. R. D. , Lak S.
Published: November 2010

Aluminum alloy workpieces of different roughness, lubricated with graphite, P.T.F.E., lead or polyethylene, were upset between overhanging dies. Measurements of the width of the unlubricated zone formed at the workpiece edge indicated that the rates of outward transport of the lubricants were increased by roughening the workpiece. This was in agreement with a simple analytical model of the lubrication process.
The Elastic Distortion of the Flanged Inner Ring of a High Speed Cylindrical Roller Bearing
Authors: Taylor Christopher M.
Published: November 2010

The elastic distortion of the inner ring of an experimental 3 × 106 DN roller bearing is investigated analytically. The geometry of this bearing is unusually complex and for this reason a bearing with an axially symmetric inner ring and shaft is also analyzed. Only the inner ring and shaft are considered using a two dimensional finite element computer program which enables interference between these components to be accommodated. The results for the experimental bearing suggest that elastic distortions are modest in relation to the design clearances. However, the variation of the radial deflection of the raceway may be significant for some circumstances and the interference fit adopted between the ring and shaft appears to be questionably low.
Determining the Coefficient of Friction for Rolling Disks
Authors: Offner D. H. , Tomita N.
Published: November 2010

A method and testing device for determining a coefficient of friction for rolling disks is described. The method equates the energy of rolling resistance to the change in potential energy of a moving system. The experimental results of applying this method to steel, aluminum, and plexiglass disks of 3.8, 2.5, and 1.7 cm radii and 1 cm width rolling on steel and aluminum bases are summarized. An empirical relationship between the coefficient of friction and energy of surface deformation is presented. Use of device for determining the static coefficient of friction for impending rolling and sliding of disks is discussed.
Depth of Penetration as a Predictor of the Wear Polymers on Hard, Rough Surfaces
Authors: Warren J. H. , Eiss N. S.
Published: November 2010

Polymers were slid on rough, hard surfaces with normal loads which caused full penetration (real and apparent areas equal) and partial penetration (real less than apparent area). SEM photographs of full penetration showed that the polymer sheared off at an angle to the horizontal, the shear angles were 10.8, 12.6, and 18.9 deg for polyvinylchloride, polychlorotrifluoroethylene, and nylon 6/6, respectively. These shear angles correlated with the energy-to-rupture of the polymers and inversely with the wear of polyvinyl-chloride and polychlorotrifluoroethylene. In partial penetration experiments the wear of polyvinylchloride and polychlorotrifluoroethylene could be discriminated by the depth of penetration of the surface into the polymer. The penetration depth is a function of the polymer yield strength and the bearing area curve of the surface.
Prediction of Traction and Microgeometry Effects on Rolling Contact Fatigue Life
Authors: Tallian T. E. , Chiu Y. P. , Van Amerongen E.
Published: November 2010

A refined mathematical model for the prediction of rolling contact fatigue is presented. It analyzes the effect of frictional traction in the contact surface, and of surface asperity slope, on the failure hazard functions applicable to surface and subsurface originated spalls. Major effects of traction on life arise from three sources: (a) increased surface distress micropitting; (b) increased microscopic shear stresses beneath surface furrows; (c) greatly increased macroscopic shear stresses in the zone relatively free from shear-stress which exists, in the absence of traction, between the asperity stress region and the Hertzian shear stress region. The major effect of steeper asperity slopes is to increase surface distress micropitting. A strong effect of traction on the angular orientation of the Hertz stress field is used to correlate experimentally observed changes in the Martin angle of orientation of deformation bands. The correlation permits calculation of the variation in the effective traction coefficient as a function of film thickness/roughness ratio. The traction coefficients obtained are then used as input to numerical life prediction. Satisfactory agreement is obtained between theory and experiment in predicting the life of seven groups of fatigue tested ball bearings with different surface roughness, run at different film thickness/roughness ratios.
Performance of 75-Millimeter Bore Arched Outer-Race Ball Bearings
Authors: Coe H. H. , Hamrock B. J.
Published: November 2010

An investigation was performed to determine the operating characteristics of 75-mm bore, arched outer-race bearings, and to compare the data with those for a similar, but conventional, deep groove ball bearing. Further, results of an analytical study, made using a computer program developed previously, were compared with the experimental data. Bearings were tested up to 28,000 rpm shaft speed with a load of 2,200 N (500 lb). The amount of arching was 0.13, 0.25, and 0.51 mm (0.005, 0.010, and 0.020 in.). All bearings operated satisfactorily. The outer-race temperatures and the torques, however, were consistently higher for the arched bearings than for the conventional bearings.
Friction and Wear of Sintered Fibermetal Abradable Seal Materials
Authors: Bill R. C. , Shiembob L. T.
Published: November 2010

Three abradable gas path seal material systems based on a sintered NiCrAlY fibermetal structure were evaluated under a range of wear conditions representative of those likely to be encountered in various knife-edge seal (labyrinth or shrouded turbine) applications. Conditions leading to undesirable wear of the rotating knife were identified and a model proposed based on thermal effects arising under different rub conditions. It was found, and predicted by the model, that low incursion (plunge) rates tended to promote smearing of the low density sintered material with consequent wear to the knife-edge. Trade-off benefits between baseline 19 percent dense material, a similar material of increased density, and a self-lubricating coating applied to the 19 percent dense material were identified based on relative rub tolerance and erosion resistance.
Response of Infinite Journal Gas Bearings to Harmonic Perturbations in the Rotational Speed
Authors: Narkis Y. , Cohen M. J.
Published: November 2010

The dynamics of a long hydrodynamic gas bearing is investigated for periodic variations of the rotational speed. The analysis is divided into two regions of interest, namely: (1) for small eccentricities the system is represented by a pair of linear differential equations with time-dependent coefficients. Investigation for a sinusoidally varying rotational speed proves that an unloaded bearing can be stable, though it is known not to be stable at all constant speeds. An approximate analytical solution is given for the orbit of a stable journal whirling about its equilibrium position. (2) For higher eccentricities the nonlinear equations describing the motion of the journal center are derived. When the speed perturbation is small, the equations may be linearized, and analytical expressions are obtained for the calculation of journal response. At given speed and eccentricity resonance is reached at the critical mass of instability threshold, but even for smaller mass the amplitudes are liable to endanger safe operation of the system.
A Contribution to the Problem of Designing Optimum Performance Bearings
Authors: Kanarachos A.
Published: November 2010

The maximum load capacity goal in hydrodynamic bearing optimization is extended to include dynamic performance characteristics, expressed by the spring and damping constants of the bearing. Investigations, based on the Maximum Principle approach and parameter optimization methods, lead to interesting conclusions, concerning the optimum film thickness geometry rsp. its convenient degrees of freedom. Emphasis is put on quasideterministic parameter optimization procedures, as they impose no restrictions on the mathematical model for the bearing pressure calculation and allow a straightforward solution of the optimization problem. Last, the presented sample results show that bearing optimization is a worthwhile task.
An Analytical Study of Starved Porous Bearings
Authors: Cusano C.
Published: November 2010

An analytical solution for the performance characteristics of starved porous bearings is obtained. The solution is based on a finite bearing with an arbitrary wall thickness. The Reynolds equation is modified to include the effect of velocity slip at the interface between the oil film and porous wall. The data presented are for a bearing with a length-to-diameter ratio of 1.0, an outside diameter-to-inside diameter ratio of 1.25 and a radial clearance-to-inside radius ratio of 0.0015. The data are presented in a form such that by knowing the oil supplied externally to the porous bearing or by knowing the active oil film arc, the load capacity and coefficient of friction of the bearing can be obtained for given eccentricity ratios and permeability parameters.
Wear and Thermal Processes in Asbestos-Reinforced Friction Materials
Authors: Pogosian A. K. , Lambarian N. A.
Published: November 2010

In design it is useful to have equations for the prediction of the wear life of clutches and brakes, and to have coefficients and parameters for various materials and conditions. On the assumption that the surface temperature of the metal counterface, as induced by rubbing at various pressures and speeds is the variable that in fact controls wear rate, an equation is given for calculating average surface temperature, and an experimental verification is given. In addition the wear coefficients and exponents are given for five materials for the equation ΔW = KPavbtc.
Dynamic Severity Criterion for Designing Against High Cycle Fatigue
Authors: Shawki G. S. A.
Published: November 2010

A novel approach to the interpretation of material behavior under cyclic loading is presented. In this approach a nondimensional criterion, featuring the dynamic severity of applied load, is put forward with a view to the provision of simple though confident assessment of component performance under dynamic load. The fatigue diagram based on the proposed criterion displays significant merits over previous diagrams, the presented approach thus providing an effective tool for designing against high cycle fatigue with due consideration to maximum utilization of material.
Squeeze Film Damper Characteristics for Gas Turbine Engines
Authors: Marmol R. A. , Vance J. M.
Published: November 2010

A mathematical model for squeeze film dampers is developed, and the solution results are compared with data from four different test rigs. A special feature of the analysis is the treatment of several different types of end seals and inlets, with inlet feedback included. A finite difference method is used to solve the Reynolds equation, with a banded matrix inversion routine. The test data are taken from a new high-speed free-rotor rig, and from three previously tested controlled-orbit rigs.
The Dynamics of Multi-Rotor Systems Supported on Oil Film Bearings
Authors: Holmes A. G. , Ettles C. M. McC. , Mayes I. W.
Published: November 2010

The self-excited transverse vibration of an elastic multirotor system due to vertical misalignment of the support bearings is investigated using initial value problem techniques. The equations of motion are expressed in terms of the free-free modes of the shaft and the modal coefficients propagated in time. The method was used to study a two-rotor four-bearing system subjected to misalignment. Previous authors have reported that for bearings with circular symmetry, some external damping acting on the shaft was necessary to obtain finite limit cycle motion. This is confirmed and it is found that, using noncircular lemon bore bearings with wide feed ports, realistic limit cycles were obtained which were in agreement with the amplitude and frequency of limit cycle motion observed on large turbogenerators. The method is general and may be used for any rotor geometry for which the free-free modes and natural frequencies are known and for any number of bearings. As a by-product, the correct alignment of the system is calculated and the linearized properties, such as stability and forced response, are produced.
Lattice Contact In Generated Spiral Bevel Gears
Authors: Baxter M. L.
Published: November 2010

The tooth surfaces of generated spiral bevel gears are composed of a large number of flats, or facets, spaced so closely that substantially smooth surfaces result. In the simplest form of such gears, having constant-depth teeth, these facets on each member coincide in direction as the gears mesh together. For the more common case of teeth with tapering depth, there is a small angle between the flats of the mating members. This paper describes how spiral bevel pairs can be generated on standard machines with standard cutters in such a way that the flats on the mating members cross each other at a substantial angle, so that an averaging effect is produced and only a small fraction of the flat-height is reflected as error in the output motion. This results in reduced noise, permitting higher production rates, less lapping time, and less required accuracy in the cutter truing operation.
An Experimental Study of the Steady-State Response of Oil-Film Dampers
Authors: Sharma R. K. , Botman M.
Published: November 2010

Oil-film dampers are an integral feature of most high-speed, lightweight turbo engines, in which they are used to suppress undesirable shaft dynamic responses. They are generally located at the antifriction main bearings. An experimental study of the steady-state response of an oil-film damper at a main bearing was conducted on the high-speed rig developed for this purpose. The rig and some typical test results on a damper with a discreet number of oil-inlet ports were described in an earlier publication [1]. In this paper, the experimental results are presented on dampers with different geometries and oil-supply arrangements. The results are presented in terms of transmissibility, deflection and damping coefficient plots. The response of the damper with radial springs to simulate gravity effects in a vertical rotor arrangement is compared to that without radial springs. It is shown that there is a range of speeds up to which the response of the damper is synchronous and beyond which it becomes nonsynchronous. No nonsynchronous behavior was observed for damper amplitudes not exceeding the mass eccentricity of the rotor, that is, the displacement of the rotor center of gravity from the geometric center for a given unbalance. It appears that in a good damper design the maximum amplitude does not exceed the mass eccentricity of the rotor.
An Analysis of Undercut Conditions and of Appearance of Contact Lines Envelope Conditions of Gears
Authors: Litvin F. L.
Published: November 2010

Necessary conditions of undercutting of gears, necessary and sufficient conditions of the existence of the contact lines envelope on the generating surface are found. The conditions are studied under which the contact lines envelope appears in the vicinity of the given contact point of the generating surface with beginning of undercutting simultaneously on the mating surface. The Wildhaber-Baxter problem of the limit normal location is a special case of the theory suggested. It is proved that the appearance of a contact lines envelope on the generating surface of skew worm-gears can be avoided and meshing conditions improved.
Steady-State Unbalance Response of a Three-Disk Flexible Rotor on Flexible, Damped Supports
Authors: Cunningham R. E.
Published: November 2010

Experimental data are presented for the unbalance response of a flexible, ball bearing supported rotor to speeds above the third lateral bending critical. Values of squeeze film damping coefficients obtained from measured data are compared to theoretical values obtained from short bearing approximation over a frequency range from 5000 to 31,000 cycles/min. Experimental response for an undamped rotor is compared to that of one having oil squeeze film dampers at the bearings. Unbalances applied varied from 0.62 to 15.1 gm-cm.
Computer Aided Design Studies of a Multiple Cylinder Refrigeration Compressor
Authors: Hamilton J. F. , Schwerzler D. D.
Published: November 2010

A multi-cylinder refrigerant compressor was analytically modeled and simulated on a digital computer. The modeling includes the kinematics of the mechanical compressor, the thermodynamic processes in the cylinders and the flow process of the refrigerant gas in and out of the cylinders. In addition the modeling includes the valve dynamics in controlling the gas flow, the thermodynamic processes in the common suction and discharge plenums and the interaction of the cylinder processes through the common plenums. The remainder of the refrigeration system was treated as pressure-temperature drop. The analytical model was compared to experimental data in terms of cylinder pressures, suction-discharge plenum pressures and temperatures, valve motions and the average mass flow rate of the refrigerant gas. The correlation between the comparison variable was quite good with some error in the prediction of suction valve closing time. The analytical model was used to predict the effect of increased compressor speed on the performance of the compressor. The speed was increased from 500 rpm to 2700 rpm with a decrease in volumetric efficiency from 87 percent to 60 percent, an increase in mass flow rate from 0.0378 kg/s to 0.151 kg/s. Valve impact speeds were also calculated to predict degradation in valve life.
Creep Relaxation of a Beam of General Cross Section Subjected to Mechanical and Thermal Loads
Authors: Eslami M. R.
Published: November 2010

Creep relaxation of a beam of general cross-sectional area subjected to mechanical and thermal load is obtained. Temperature is assumed to be a function of Z, the height of the beam, and the mechanical moment on the cross section M. The stress in the beam is obtained as a function of time. It is concluded that the point of zero stress shifts, and therefore, the neutral axis of the beam moves toward the lower stress magnitude portion of the cross section, and as time passes it sharply drops to a large stress of the opposite sign that for a large enough time will exceed the allowable stress, and therefore causes failure of the beam.
Model Formulation of Complex Mechanisms With Multiple Inputs: Part II—The Dynamic Model
Authors: Benedict C. E. , Tesar D.
Published: November 2010

The system model of a complex multiple degree of freedom mechanical device containing external loads, masses, springs, and dashpots is obtained explicitly in terms of the kinematic influence coefficients given in the companion paper, Part I. The controlling nonlinear coupled differential equations can be obtained by an elementary power balance in terms of this model. The formulation should be effective in developing a qualitative description of complex dynamic systems to treat their dynamic response, vibration, or automatic control during adjustment.
Force System Structural Synthesis By Using Coupler Curves and Interactive Computer Graphics
Authors: Carson W. L. , Haney R. S.
Published: November 2010

An interactive computer graphics program has been developed to structually synthesize force systems which will drive a 4R-4Bar linkage to have a desired dynamic motion time response. The program is also useful for iterative dimensional synthesis. The program contains a coupler curve “boxing” technique to help the designer identify generalized force “characteristic” curve shapes for translational force elements between nonadjacent links. Some general observations about generalized force “characteristic” curve shapes are also presented.
Elastodynamics of Planar Mechanisms Using Planar Actual Finite Line Elements, Lumped Mass Systems, Matrix-Exponential Method, and the Method of “Critical-Geometry-Kineto-Elasto-Statics” (CGKES)
Authors: Bagci C. , Kalaycioglu S.
Published: November 2010

The article presents a general method for the elastodynamic analysis of planar mechanisms. It uses planar actual finite line elements (regular and irregular elements given in a companion article) and lumped mass systems to formulate the equations of motion of a mechanism. Damping coefficient matrix can incorporate time dependent viscous or coulomb damping coefficients in addition to the coefficients of velocity dependent internal damping. The forcing vector can incorporate any externally applied time dependent force or torque, inertial forces and inertial torques, any nonlinear viscous or Coulomb damping forces and torques. The matrix exponential method is introduced for the numerical solution of the equations of motion. Matrix displacement method of determining dynamic stresses using the generalized coordinate displacements is given. Elastodynamic analysis of a plane four-bar mechanism is performed for several cycles of kinematic motion, and the dynamic stresses are compared with those obtained by experiments. The method of “Critical-Geometry-Kineto-Elasto-Statics” (CGKES) is proposed for the computation of dynamic stress magnitudes making use of the critical geometry of the mechanism. It requires the analysis of a mechanism at the critical geometry position of the mechanism which is defined by the lowest fundamental frequency of the mechanism. The results predicted by the method of CGKES compares within two percent with the experimental results.
Degree of the Input-Output Equations of Certain Geared Five-Bar Mechanisms
Authors: Fichter E. F. , Hunt K. H.
Published: November 2010

The properties of trochoids, as given in a theoretical companion paper, are here related to certain geared five-bar mechanisms. Specifically the degrees of the input-output equation for several varieties of geared five-bar mechanisms are tabulated. Several special cases and other variations are discussed and illustrated. The use of point-cognate and line-cognate mechanisms is suggested, and a few examples of the degrees obtained for specific mechanisms are given. Finally an example of one pitfall in the algebraic treatment of these mechanisms is presented.
Human Factors in Machine Design
Authors: Garg A. , Kohli D.
Published: November 2010

A brief literature survey of human factors engineering as applied to machine design is presented. The literature has been classified under the categories: (i) static and functional body dimensions, (ii) body posture and static work, (iii) muscle strength, (iv) metabolic energy expenditure rate, and (v) other factors. A technology transfer mechanism using monographs is suggested to transfer the technology from research level to practice level.
Automated Optimum Design of Refrigerated Warehouses
Authors: Gupta B. D. , Rao S. S.
Published: November 2010

The main consideration in the design of refrigerated commercial warehouses, apart from energy required for operation, is the total cost (initial plus operating costs). There is no simple explicit relation between the total cost and the energy required to maintain the desired inside conditions. Qualitatively, one feels that a design involving less initial cost requires larger energy input and hence a higher operating cost. With limited energy resources, it is necessary to conserve energy or use it optimally. A unified approach to find the optimal combination of initial cost and operating cost (energy) is presented in this paper. Since the thickness of insulation is one of the important factors to be considered in reducing the external load and hence the energy requirements, the optimum building envelope and insulation thicknesses are found for a specified volume and location by using the interior penalty function method of optimization. The procedure outlined in this paper can be used for new as well as existing building to fulfill the functional requirements optimally and thus conserve the energy to the greatest possible extent. For the computation of heat gain, the design day, based on the average maximum solar air temperature computed from the hourly meteorological data, is chosen. The resulting computer program is used to find the effect of some of the parameters like wall thickness, type of insulation, orientation of building and economics model on the optimum design.
Numerical Investigation of Some Potential Problems of Univariate Minimization Methods
Authors: Johnson G. E. , Townsend M. A.
Published: November 2010

Many nonlinear programming algorithms employ a univariate subprocedure to determine the step length at each multivariate iteration. In this note, a popular polynomial approximation-interpolation univariate algorithm (DSC-P) is compared to two versions of the golden section search. One-dimensional test functions which model the behavior of barrier and penalty functions are used for the comparison. In general, the polynominal method indicates convergence in fewer function evaluations than the golden section search. However, it is significantly less reliable. Tight convergence criteria do not necessarily lead to accurate results with the polynomial-based univariate strategy. A companion paper provides a theoretical basis for the observations and gives conditions underwhich DSC-P will fail—even for strictly convex, unimodal functions and exact arithmetic.
International Standardization of Boilers and Pressure Vessels
Authors: Fishman Bernard
Published: November 2010

International standardization in the field of boilers and pressure vessels is being carried out within the International Organization for Standardization (ISO) by Technical Committee No. 11. The American Society of Mechanical Engineers (ASME) is responsible for coordinating this activity on behalf of the American National Standards Institute (ANSI). Forty-two countries are involved in the work of TC 11 which is organized into 4 subcommittees and 16 working groups covering major areas such as materials, design, welded construction, and serially made pressure vessels.
Underground Storage Systems for High-Pressure Air and Gases
Authors: Beam B. H. , Giovannetti A.
Published: November 2010

This paper is a discussion of the safety and cost of underground high-pressure air and gas storage systems based on recent experience with a high-pressure air system installed at Moffett Field, California. The system described used threaded and coupled oil well casings installed vertically to a depth of 1200 ft (366 m). Maximum pressure was 3000 psi (20.7 MPa) and capacity was 500,000 lb (227 kg) of air. A failure mode analysis is presented, and it is shown that underground storage offers advantages in avoiding catastrophic consequences from pressure vessel failure. Certain problems such as corrosion, fatigue, and electrolysis are discussed in terms of the economic life of such vessels. A cost analysis shows that where favorable drilling conditions exist, the cost of underground high-pressure storage is approximately one-quarter that of equivalent aboveground storage. Wider use, however, depends on a favorable reception by other experienced engineers and revisions in the ASME Boiler and Pressure Vessel Code to encompass this technique.
Heat-to-Heat Variation in Creep Properties of Types 304 and 316 Stainless Steels
Authors: Sikka V. K. , McCoy H. E. , Booker M. K. , Brinkman C. R.
Published: November 2010

A wide variation in creep-rupture and long-term creep properties of 20 heats of type 304 and seven heats of type 316 stainless steel was observed. The observed variation in 1000-hr creep-rupture strength, SRt, has been related to the corresponding ultimate tensile strength variation, Sur, by a relationship of the form: SRt=αexp(βSur), where α and β are material constants. This relationship between creep-rupture strength and ultimate tensile strength was further extended for minimum-expected 105-hr creep-rupture strength data reported in the literature. The heat-to-heat variation in ultimate tensile strength for both types 304 and 316 stailness steel was explained in terms of carbon plus nitrogen content and grain intercept, d, by a relationship of the form Sur = A(C + N)−1/2 + B, where A and B are constants for a given temperature. The time to onset of third-stage creep for various heats of type 304 and 316 stainless steel was related to time to rupture by relationships that are independent of test temperature, for test times reaching 22,622 hr.
A J-Integral Analysis to Fracture Toughness of Plates Containing Surface Cracks
Authors: Zamrik S. Y. , Bahgat F. M.
Published: November 2010

The J-integral approach was applied to plates containing surface flaws type of cracks. The experimental procedure followed in this investigation was based on a proposed method by Begley and Landes that utilizes a resistance “R” type curve to find a critical value of J for specimens containing straight cracks. Furthermore, the Begley-Landes procedure was modified to consider the incremental growth of the crack frontal area due to static loading. An interpolation process was used for estimating average values of Jc and Kc for crack geometries which lie between those obtained experimentally. Moreover, a shape correction factor was obtained which shows the dependence of the average value of the stress intensity factor, Kc, on the crack geometry and the relative crack-to-specimen dimensions.