bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation of the Pitting Fatigue Life of Bearings With Rolling Contact Rig Data
Authors: Morrow JoDean
Published: November 2011

The general method for correlating the fatigue pitting life of simple rolling elements with the life of bearings is discussed. A “correlation equation” is presented which permits the pitting fatigue life of full scale bearings to be estimated from minimal rolling contact rig data. Three M-50 (MV-1) bearings are analyzed using this equation. In all three cases the life is predicted within a factor of two.
Experimental Determination of the Critical Reynolds Number for Pulsating Poiseuille Flow
Authors: Sarpkaya Turgut
Published: November 2011

The stability of fully developed Poiseuille flow pulsating under a harmonically and a nonharmonically varying pressure gradient was studied experimentally. The characteristics of turbulent plugs were determined for both steady and pulsating flow by means of pressure transducers. It was found that (a) for oscillating, stable Poiseuille flow, the phase angles determined experimentally agree well with those determined theoretically; (b) for the same mean pressure gradient, pulsating flow is more stable than the corresponding steady Poiseuille flow; (c) in pulsating flow, the presence of one or more inflection points is necessary but not sufficient for instability; and (d) the curves of the critical Reynolds number versus the relative amplitude of the periodic component of the cross-sectional mean velocity reach their maximum when at least one inflection ring continues to exist a time period 53 percent of the period of oscillation.
Propagation of Contact Fatigue From Surface and Subsurface Origins
Authors: Littmann W. E. , Widner R. L.
Published: November 2011

Fatigue life of tapered roller bearings and other elements subject to cyclic contact stress reflects the fatigue strength of the selected material under given environmental conditions. The various modes of contact-fatigue failure have been classified according to their appearance and the factors which promote their initiation and propagation. Illustrations of the various failure modes include rig test specimens and bearings representing normal catalog-rated life under laboratory and application environments. Evidence is presented for the propagation of contact fatigue from surface and subsurface origins.
Effect of Exposure Time on Cavitation Damage
Authors: Plesset M. S. , Devine R. E.
Published: November 2011

It has been proposed in some recent publications that the cavitation damage rate decreases markedly in solids after long exposure to cavitation. It has also been proposed that this low rate of cavitation damage is the one with physical significance for the solid. These observations have been made with specimens oscillated sinusoidally in liquids by means of magnetostrictive devices. In the observations described here, it is shown by means of photographs of the cavitation cloud over such specimens that the reduced damage rate results from the very sparse bubble cloud which is formed over the deeply damaged surface. The change in the damage rate therefore has hydrodynamic origin and is not related to a change in the properties of the solid. X-ray analyses show also that the extent of the plastic deformation of a solid with very light damage is the same as for a solid with very heavy damage.
Discharge Coefficients of Fire Nozzles
Authors: Murakami Mitsukiyo , Katayama Kinji
Published: November 2011

The most efficient nozzle is generally considered to be that for which the discharge coefficient is nearest unity. Forms and dimensions of the nozzles being equal, the greater the discharge coefficient, the less the jet turbulence becomes. The inefficiency of fire streams is directly attributable to the inital turbulence of the jet and this turbulence has its chief origin in the flow condition inside the nozzle. Thus a knowledge of the discharge coefficients is of great importance in fire engineering. With various smooth nozzles, the coefficients were measured experimentally and the results were discussed theoretically.
Separation in the Flow Between Eccentric Rotating Cylinders
Authors: Kamal M. M.
Published: November 2011

This study is concerned with the steady flow of a fluid of constant density and viscosity between two eccentric cylinders of fixed parallel axes. The inner cylinder has a constant angular velocity and the outer one is stationary. Approximate solutions of the Navier-Stokes equations were obtained for the two-dimensional flow. These solutions together with an experiment were utilized to study the appearance of an eddy with separation and reattachment points occurring at the outer cylinder.
Most Probable Discharge Coefficients for ASME Flow Nozzles
Authors: Benedict Robert P.
Published: November 2011

In this paper, various rational, semirational, and, empirical approximations for the ASME long-radius, flow-nozzle discharge coefficients are first reviewed. These approximations are then compared to obtain the most probable representation of ASME flow-nozzle data according to a mathematical method developed in the paper. A table of most probable discharge coefficients versus the throat Reynolds number is given, based on the results of this study.
Near Optimal Control in the Presence of Small Stochastic Perturbations
Authors: Kushner H. J.
Published: November 2011

We consider the stochastic system x˙(t) = f(x(t), u(t)) + ξ(t) where ξ(t) is a noise term, with loss criterion E∫0Tg(x,u)dt. A method of computing a correction to the optimal deterministic control, when the effects of ξ(t) are small, is presented. The method is based on some recent works in the stochastic calculus of variations which prove the applicability of a form of the Lagrange multiplier rule and the Hamiltonian formulation to stochastic extremum problems. The method is quite general and is capable of expansion to a greater degree of control correction as the noise effects increase.
On the Formulation of Adaptive Optimal Control Problems
Authors: Pearson A. E. , Sarachik P. E.
Published: November 2011

The paper relates to an approach introduced by Kulikowski for adaptive optimal control of nonlinear systems. In this approach, the plant dynamics are represented symbolically by an operator which transforms or maps input time functions into corresponding output time functions. The contributions of the paper arise mainly from the physical considerations associated with such an operator representation, specifically the memory of the plant, and the influence of these considerations upon the formulation. It is shown that the optimal control problem may be formulated in various ways for a given plant and given performance criteria depending upon how the memory of the plant is taken into account.
Analysis and Test of the Screw Seal in Laminar and Turbulent Operation
Authors: McGrew J. M. , McHugh J. D.
Published: November 2011

An analytical and experimental study of the screw seal in both laminar and turbulent operation is presented. The various scattered analyses of laminar screw seal operation are evaluated in comparison with one another and with a simplified flow model. The basic equations are extended to cover turbulent flow. Experiments are described in which the screw seal was tested in both laminar and turbulent flow regimes. Finally, the breakdown of sealing capability under certain conditions is examined and reasons postulated for its behavior.
Frictional Characteristics of Liquid Hydrostatic Journal Bearings
Authors: Shinkle J. N. , Hornung K. G.
Published: November 2011

A theoretical and experimental analysis is made of the frictional torque resisting the motion of high-speed liquid hydrostatic bearings. Results are presented in terms of friction factors which will enable the calculation of resisting torque for any hydrostatic bearing.
Thermal Effects in Contact Fatigue Under Oscillatory Normal Load
Authors: Burton R. A. , Tyler J. C. , Ku P. M.
Published: November 2011

Experiments are reported wherein contact fatigue was brought about by the application of an oscillatory normal load between a ball and a flat specimen. Plots of the flat-specimen temperature versus time showed that a rapid temperature rise occurred in the initial stage of crack formation, and thus provided an early indication of fatigue. Thermal resistances were measured for the apparatus components as well as the specimen contact. Using these, it was possible to apply the measured flat-specimen temperature to obtain estimates of the contact temperature as well as the energy dissipation rate prior to the incidence of fatigue cracks. It was shown that the contact temperature did not rise sufficiently to produce annealing in the test specimens. Thus, toroidal rings of hardened and softened material in the stressed zone could not be attributed to thermal transformation of the bearing steel. It was also shown that energy dissipation due to cyclic loading varied in approximate exponential relationship with dynamic load, and decreased upon increase of static load when dynamic load was maintained constant.
Hydraulic Speed Governor With Major Governor Problems Solved
Authors: Oldenburger Rufus
Published: November 2011

The dashpot-type isochronous governor (which may be modified by droop) is the standard hydraulic governor in current use for prime movers. This governor is designed to give proportional-plus-integral (actually, rate-responsive) control. The governor has the advantages of giving constant speed control where desired; it can be adjusted to compensate for a low value of damping in the engine system to be controlled, and it has a dashpot including a needle valve whereby one of the governor constants can be varied readily. Disadvantages of hydraulic governors in common use are the poor adjustability of control parameters; too small needle valve openings for normal applications; sensitivity of the dashpot to variations in the viscosity of dashpot oil causing corresponding variations in control parameters; floating (receiving or proportioned pistons that can and do stick; and the relative noninterchangeability of the governors from one type of engine to another. In the new governor described in the paper the foregoing problems and others not mentioned are all solved with the aid of a technique for hydraulic addition. In contrast to current governors, governor parameters including governor time lag can be adjusted independently. Load control can be introduced to the governor without the need of an extra servomotor. Nonlinearities are incorporated to improve performance. This governor is a radical departure from existing units greatly increasing the flexibility and reliability of the speed governor.
Thermal Fatigue of a Nickel-Base Alloy
Authors: Carden A. E.
Published: November 2011

The results of conventional (Coffin-type) thermal-fatigue tests of Hastelloy N are reported. The plastic-strains induced by thermal stresses ranged from a hundred micro-units to more than ten-thousand microunits and correlated well with fatigue life. The slope of the plastic-strain fatigue relationship differs from the conventional slope of minus one half being about −0.9. The thermal-fatigue data are in good agreement with the isothermal (1300 and 1500 deg F) strain fatigue data available on this alloy. The same plastic-strain criterion for failure describes the results of tests where plastic flow is produced by yielding and a combination of yielding and stress relaxation. The plastic-strain energy per cycle versus life suggests that a constant plastic work to failure exists for this alloy. The implications of such a criterion are discussed.
On Performance Losses in Some Adaptive Control Systems: I
Authors: Aoki Masanao
Published: November 2011

In controlling dynamic systems with unknown parameters and/or systems operating in unknown environment, the systems suffer due to the unknowness of pertinent parameter values, compared with situations with perfect information where all pertinent information is available to control systems optimally. The paper defines the concept of loss of performance to represent the loss in performance of some adaptive control situations compared with perfect information situations and defines the optimal control problems as the one where the loss of performance is minimized. This concept is illustrated for a control system governed by a scalar linear differential equation with unknown gain. The minimax control policy is defined as the control policy which minimized the maximum possible loss in performance where no a priori knowledge on the unknown parameter is available. It also discusses the optimal estimation problem of the unknown parameter from the point of view of loss of performance.
Optimum Nonlinear Control for Step and Pulse Disturbances
Authors: Oldenburger R. , Chang R. C. C.
Published: November 2011

This paper treats the responses of a controlled system to step and pulse disturbances where the rate of change of the controlling variable is bounded. Optimum transients in the sense of minimizing the maximum error, response duration, and other variables are derived for step and pulse disturbances whose parameters, i.e., magnitude, sense of change, instant of occurrence and pulse duration, are either completely known in advance, or known at the instant the disturbance starts, or not known in advance at all. It is shown that the more that is known about the disturbance beforehand, the better the response that can be obtained. The improvement may be very great. The optimum control function for a pulse disturbance known at the initiation of the pulse contains disturbance parameters. A practical control function can be derived by eliminating these parameters so that no advance information about the disturbance is required. The resulting control function will yield optimum transients and will depend entirely on the system error and its derivatives. This practical control function yields improved response over classical theory to a train of pulse-load disturbances.
Effect of Composition and Microstructure on the Low Cycle Fatigue Strength of Structural Steels
Authors: Stout R. D. , Pense A. W.
Published: November 2011

In a number of studies of data obtained from fatigue tests on various materials it has been shown that the number of cycles to failure is related to the strain range by a relationship of the form εNm=c where N is the number of cycles to failure, ε the strain range, and m and c are constants. In the low cycle portion of the strain range versus cycles to failure curve, evidence has been presented by several investigators to show that the relationship should be εpN1/2=c where εp is the plastic strain range and c, the constant, can be related to tensile ductility. Some investigators have found the relation εtNm=c more useful. Here εt is the total strain range. As a result of a series of Pressure Vessel Research Committee investigations at Lehigh University, a large body of low cycle fatigue data has been obtained for a wide range of steels, microstructures, heat-treatments, and testing conditions. A study of these data has been undertaken, with special emphasis on the suitability of a relationship of this type for analysis and representation of fatigue data. As a result of this study the following conclusions have been drawn: (a) In the range of 5000 to 100,000 cycles a relation εtNm = c appears to be satisfactory. (b) Using this latter relation, an analysis of the low cycle fatigue behavior of structural steels reveals that they can be classified into three broad groups on the basis of their composition. Each group has a characteristic value of m and c which can be used to predict their behavior over the range 5000–100,000 cycles. (c) The value of m and the total strain for 5000 cycle life can be related to n, the strain hardening exponent, for the steels. The total strain for 100,000 cycle life is related to the ultimate tensile strength of the steels. Using these relationships, the fatigue curve for a structural steel can be estimated from tension test data. (d) The effect of microstructural variations for a steel within any one of the three groups was of secondary importance when compared to the compositional groupings, although some systematic effects of microstructural variations were noted.
Creep-Rupture Behavior of Unnotched and Notched Nickel-Base Alloys in Air and in Vacuum
Authors: Shahinian P.
Published: November 2011

The influence of test atmosphere on creep-rupture properties was determined for plain and notched bars of nickel, Nichrome V, Udimet 500, and Inconel X. The rupture life of nickel and of Nichrome V was shorter in air than in vacuum at relatively low temperatures, but at high temperatures it was longer in air. While both types of specimen geometry were generally affected alike by atmosphere, a larger atmosphere effect was observed for notched bars of the two materials in the air-strengthened region. The Udimet 500 and the high-strength Inconel X alloys at 1500 deg F were slightly stronger in vacuum than in air. However, the Inconel X with a modified heat-treatment displayed a reversal in the atmosphere effect. It was observed that all the materials generally develop intergranular cracks more readily in air than in vacuum.
Uniaxial Creep-Rupture Behavior of Low-Alloy Steel Under Variable Loading Conditions
Authors: Goldhoff R. M.
Published: November 2011

One of the analytical tools most used by elevated-temperature designers is the log stress-log minimum creep-rate curve. The curve is normally constructed using at least three and preferably more data points from individual tests. In this paper the possibility of constructing the stress-minimum creep-rate curve using a single specimen programmed for variable step-up and step-down loading is investigated. Both high and low-ductility Cr-Mo- V steels are studied. The results are treated both graphically and analytically to predict rupture under variable loading. Interesting metallographic features of rupture are shown and the results treated using phenomenological theory of anelasticity. It is concluded that a reasonable estimate of the stress-minimum creep-rale curve can be obtained during step-up loading of a single specimen of ductile steel. Among the various techniques for predicting rupture life under variable loading, a strain-fraction method gives good results.
Thermal Stresses in Anisotropic Hollow Cylinders
Authors: Weng Tu-Lung
Published: November 2011

The equations of thermal stresses and displacements in anisotropic hollow cylinders subjected to various selected temperature boundary conditions have been derived. The hollow cylinder is assumed to be made of transversely isotropic material. Several numerical examples are treated and the effects of the degree of anisotropy on the magnitudes of the critical stress and maximum permissible gas temperature for various sizes of grades ATJ and ZTA graphite hollow cylinders are examined. The errors which could result from the assumption of isotropic material are calculated.
On the Distribution of Rises and Falls in a Continuous Random Process
Authors: Rice J. R. , Beer F. P.
Published: November 2011

This paper is concerned with the statistics of the height of rise and full for continuous random processes. In particular, approximate methods are given for determining the probability density of the increment in a random continuous function as the function passes from one extremum to the next. Application of the general result is made to the case of processes with a Gaussian distribution. Numerical results are given for four special cases of stationary Gaussian processes. Computed results are found to agree well with available experimental data. The knowledge of such statistical information is of use in studies dealing with fatigue under random loadings.
An Analytical and Experimental Study of the Plane, Incompressible, Turbulent Free-Shear Layer With Arbitrary Velocity Ratio and Pressure Gradient
Authors: Sabin C. M.
Published: November 2011

A first-order approximation is derived in similarity coordinates for the velocity variation across a mixing zone between two streams of different velocities in an arbitrary pressure grudient. The velocity profiles obtained are functions of a single parameter, the ratio of the velocity of the slow stream to that of the fast stream. The first-order velocity profiles are compared to those obtained from the complete solution to the zero-pressure-gradient case obtained by Go¨rtler and good agreement is found when the velocity ratio is greater than 0.5. The form of the eddy diffusivity appropriate to the first-order theory is determined from analysis and experimental data. This form leads to an explicit transformation for the similarity coordinate requiring only a single empirical constant for all cases.
Distortion of Short Pulses in Tapered Tube Pulse Transformers. Part I—Inviscid Liquid
Authors: Rouleau W. T. , Young F. J.
Published: November 2011

A tapered pipe (or “line”) is a convenient transformer for pulses of pressure or volume flux, but the pulse usually becomes distorted, depending on the geometry of the taper. The principal objective of this paper is to present and illustrate a method for determining the distortion of short pulses and to show that it is possible to construct a distortion-free line. In the model considered a pulse input of volume flux is applied to one end of a tapered line containing an inviscid liquid and the form of the output pulse is found for a termination consisting of a very long uniform line.
Pressure Surges in Magnetoviscous Flow
Authors: Young F. J. , Rouleau W. T.
Published: November 2011

An examination is made of the effect produced by an externally applied magnetic field when the flow of an electrically conducting fluid is stopped by the sudden closure of a valve. The fluid is confined in a rectangular channel, one end being connected to a constant pressure source and the other end terminated by the valve. An expression is derived for the fluid pressure in terms of the properties of the fluid and the applied magnetic field for the open circuit case. It is shown that electromagnetic forces, while exerting no net body force on the fluid in this particular case, act to increase wall shear and thereby tend to increase the damping of the pressure surges. Expressions are also derived for the induced magnetic fields.
Lubrication Phenomena in Spur Gears: Capacity, Film Thickness Variation, and Efficiency
Authors: Adkins R. Wayne , Radzimovsky E. I.
Published: November 2011

In this paper the oil film separating the mating surfaces of involute spur gears operating under hydrodynamic lubrication conditions is analyzed. This analysis surpasses previous analyses in as much as the actual motion of the involute profiles (rolling, sliding, and squeezing motion) and the total number of teeth engaged at any one time are considered. Expressions are derived for the pressure distribution, shear stress, and power loss in the oil film at any phase of tooth engagement. A method is developed by which these expressions can be applied to determine the film thickness at any instant and the power loss for a given load, speed, and lubricant viscosity.
Contributions to the Determination of the Real Clearance in Sliding Bearings
Authors: Nica Al.
Published: November 2011

When the bearing is running, its clearance is no longer equal to the initial one, as a result of the thermal regime and load. This paper presents a calculation method which takes into consideration the temperature distribution in the bearing, the load, and the elastic properties of the materials. The deduced calculus relations allow to establish the correction of the initial radial clearance in order to obtain the designed clearance when the bearing is running.
An Approximate Solution for the Infinitely Long, Gas Lubricated Slider Bearing
Authors: Sneck H. J.
Published: November 2011

The only exact solution for the infinitely long, gas-lubricated slider bearing is the one obtained by Harrison [1] for the plane wedge isothermal film. The resultant formulas for the pressure distribution and load-carrying capacity are complicated and therefore quite cumbersome in numerical design calculations. In the analysis to follow, a simplified, approximate solution is developed which can be applied to any infinitely long slider geometry.
Thermal Wedge Lubrication of Parallel Surface Thrust Bearings
Authors: Currie I. G. , Brockley C. A. , Dvorak F. A.
Published: November 2011

The parallel surface thrust bearing has been studied both theoretically and experimentally. The general equations governing the laminar flow of a Newtonian fluid are presented and suitably reduced to describe the flow of lubricant through a plain collar bearing with sector pads. A computer solution of the resulting equations has been obtained in which the variations of density and viscosity with temperature are accommodated and the circumferential leakage of oil from the bearing is recognized. The resulting performance curves indicate that useful load-carrying capacities, produced by a “thermal wedge” effect, are possible with a parallel surface thrust bearing. The effect of the inlet oil temperature and bearing speed on the performance is shown. Tests were carried out on three, four, and five-pad bearings operating at 15,000 rpm. It was found that circumferential oil seals were required to insure stable operation. The results confirm that hydrodynamic lubrication may be achieved with a parallel surface thrust bearing. However, it was found that some practical limitations are imposed by high temperatures. A comparison between the theoretical load capacity of an optimum tilting pad bearing and that of a parallel surface bearing for equivalent pad dimensions, speed, and lubricant conditions revealed that the tilting pad bearing had the superior performance. Comparison of friction results with the findings of other workers shows good agreement.
Push-Pull Fatigue Strength of Mild Steel at Very High Frequencies of Stress Up to 100 kc/s
Authors: Kikukawa M. , Ohji K. , Ogura K.
Published: November 2011

Previous investigations of frequency on fatigue strength are briefly reviewed in this paper. New resonant-type push-pull fatigue testing machines at 50 and 100 kc/s were also developed by using a ferrite magnetostrictive vibrator. By using these machines, as well as previously developed high and low-frequency push-pull fatigue testing machines, the influence of stress frequency on fatigue limit of two carbon steels was determined at frequencies ranging from 40 to 100,000 c/s. The fatigue limit was found to increase monotonically with increasing frequency. No peak in the value of the fatigue limit was observed at frequencies up to 100,000 c/s.
The Interaction Effect of Neighboring Holes or Cavities, With Particular Reference to Pressure Vessels and Rocket Cases
Authors: Peterson R. E.
Published: November 2011

The problem treated in this paper is the following: If the strength of a member is reduced a certain amount by the presence of a single hole (or cavity), how close can a second hole (or cavity) be located relative to the first one without causing appreciable further reduction of the strength of the member? This problem arises in evaluating the results of nondestructive tests (x-ray, ultrasonic) of welds, forgings, and castings with regard to inclusions and porosity [1]. The available results for elastic stress distributions are reviewed; some estimates are made for examples for which solutions are not available. A complete solution of this problem must consider inelastic behavior and failure. In the absence of the needed information, it is believed that some guidance can be obtained from a comparison of elastic solutions, since we are concerned here with ratios (i.e., comparisons between one and two holes) rather than absolute strength determinations.
An Engineering Basis for Establishing Radiographic Acceptance Standards for Porosity in Steel Weldments
Authors: Greenberg H.
Published: November 2011

Radiographic acceptance standards, such as those found in the ASME Unfired Pressure Vessel Code are critically reviewed. Limits on the size and distribution of porosity in steel welds are analyzed from the viewpoint of susceptibility to failure in service. In large part, present standards for porosity appear to have been established on a “good workmanship” basis rather than on setting sound conservative limits for the maximum size, and distribution of flaws which can be tolerated without decreasing the reliability of the product. Radiographic acceptance standards in use today do not reflect the significant advances being made in (1) the fracture mechanics approach to designing for prevention of failure; (2) theoretical studies of the stress-concentration effects of holes in close proximity to one another; and (3) the possible use of complementary nondestructive testing techniques. Considerable emphasis is placed on the proposition that radiographic acceptance standards for weldments must be designed specifically for each particular application. Considerations applicable to welds in the 120-in-dia rocket motor case are cited as an example of how standards for acceptable porosity and inclusions can be established.
System Oscillations Associated With Cavitating Inducers
Authors: Sack L. E. , Nottage H. B.
Published: November 2011

The nature and inception of pressure and flow-rate oscillations associated with a high-speed cavitating inducer have been investigated by nonlinear analog computer simulation. The favorable accord between simulation findings and typical actual dynamic oscillation characteristics validates the general technique for extension into inducer design analyses. The nature and behavior of the cavitation vapor volume and the dynamic response characteristics of the complete fluid circuit play key roles in the incidence and suppression of oscillations.
Cavitation Bubble Collapse in Viscous, Compressible Liquids—Numerical Analysis
Authors: Ivany R. D. , Hammitt F. G.
Published: November 2011

Collapse of a spherical bubble in a compressible liquid, including the effects of surface tension, viscosity, and an adiabatic compression of gas within the bubble is investigated by numerical solutions of the hydrodynamic equations. A limiting value of shear viscosity causes the bubble collapse to slow down markedly, for both compressible and incompressible liquids, whereas moderate viscosities have very little effect on the rate of collapse. The inclusion of surface tension and viscosity introduces two scaling parameters into the solution, so that a single normalized solution is no longer sufficient to describe collapse behavior. The magnitude of the density changes calculated for the compressible liquid and the extremely rapid changes with time suggest that the usual Navier-Stokes equation of motion may not be appropriate. The possibility of liquid relaxational phenomenon and its contribution to sonoluminescence is considered. Shock waves or damagingly high pressures are not generated during collapse at a distance in the liquid equal to the initial radius from the center of collapse, although they will appear at such a distance if the bubble rebounds.
A Combined Analytical and Experimental Approach to the Development of Fluid-Jet Amplifiers
Authors: Brown F. T.
Published: November 2011

An approach to the development of “pressure-controlled” fluid-jet relays and amplifiers is proposed. The technique, based on experiments of a jet attaching to a flat wall, combines theoretical reasoning, experimental data, and graphical source-load matching. Single-control and symmetrical double-control amplifiers of a particular “knife-edge” design are used in the illustrations of the approach; typical data are given. Static and dynamic stability of the jet is emphasized including the criteria for oscillators.
A Review on Vortex Streets, Periodic Wakes, and Induced Vibration Phenomena
Authors: Marris A. W.
Published: November 2011

A survey is presented of recent experimental and theoretical researches on the problem of periodic wakes behind a cylinder in a stream. A synopsis is given of the present knowledge on the mechanics of wake formation and of the associated hydrodynamic forces for the full Reynolds number range from the first appearance of a stationary vortex pair behind the cylinder up to transition of the boundary layer on the cylinder. Experimental data are viewed in the light of the theoretical results of Birkhoff, which, it appears, may replace the classical theory based on the first order stability of a potential flow street of vortex filaments. The paper closes with a discussion of the problem of the induced vibration of a spring mounted cylinder in a stream.
Instabilities in the Flow of a Boiling Liquid
Authors: Stenning A. H.
Published: November 2011

The time-varying flow of a boiling liquid through a series of ducts and heaters is considered for the case where the flow rate is controlled by a downstream orifice. It is shown that oscillatory flow will exist for a variety of configurations, provided that the density ratio across the system exceeds a critical value which depends on the geometry and the heat-transfer relationship.
Passage of a Turbulent Stream Through Honeycomb of Large Length-to-Diameter Ratio
Authors: Lumley J. L.
Published: November 2011

An analysis is performed, similar to the classical one for screens, of the effect of a honeycomb on a turbulent stream, when the cell length is large enough to permit the flow to become fully developed. The results indicate that a honeycomb should reduce the turbulence level of a stream passing through it more effectively than a screen, due to two effects: (a) The annihilation of the transverse fluctuation, dependent on the assumption of fully developed flow; (b) the effect of the mass of fluid in each cell, which must be accelerated to permit the passage of a fluctuation. The latter suggests that the honeycomb may be viewed as an inductive filter, if the screen is regarded as the fluid mechanical analogy of a resistive one. A small number of measurements in water are presented which lend quantitative support to the argument. Finally, design charts are presented, which permit calculation of the reduction to be expected from the placing of a given honeycomb in a given flow.
The Problem of Pneumatic Pressure Lag: Part 1—Steady-State Flow in a Tubing System
Authors: Ducoffe A. L. , White F. M.
Published: November 2011

An analytical and experimental investigation of the steady-state isothermal flow in a series system, comprised of a constant-diameter tube with reduced size unions located at the tube extremities, is reported herein. The pressure drop across the system has been determined experimentally as a function of the system geometry. The parameters chosen for investigation were the tube length to diameter ratio L/D, the union diameter to tube diameter ratio Df/D, and the Reynolds number. The ranges of the parameters investigated consisted of 159 ≤ L/D ≤ 1475, 0.7 ≤ Df/D ≤ 1.0, and 200 ≤ Reynolds number ≤ 100,000. All tests were conducted at room temperature. The theory is derived considering each geometric element of the system, such as inlet, development length, exit, and so on, and a set of five simultaneous algebraic flow equations results. Solutions to these were obtained by use of a digital computer. A pseudo-friction factor, for fully developed laminar or turbulent flow, is defined. The result indicates that the correlation of theory with experiment is quantitative over the range of parameters investigated.
Experimental Investigations of Incipient and Desinent Cavitation
Authors: Lehman A. F. , Young J. O.
Published: November 2011

Experiments with water in a high speed recirculating water tunnel were undertaken to measure the pressures at which incipient and desinent cavitation occurred. Incipient cavitation is defined as the onset of cavitation; desinent cavitation is defined as the cessation of cavitation. The two lucite test sections used formed the minimum area region of the nozzle in the water tunnel. One test section had a smoothly changing internal contour and the other had an abrupt contour change at the entrance to the cylindrical throat region. Cavitation in the abrupt contour occurred at the throat entrance at higher pressures than the cavitation pressures in the smooth contour. The cavitation in the smooth contour occurred at the entrance to the diffuser part of the nozzle. It was concluded that the cavitation pressures and cavitation numbers increased with velocity, the increase being greater for the abrupt contour with the exception of minimums indicated at incipient conditions in the abrupt contour at throat velocities near 88 ft/sec. A notable difference between the incipient and desinent cavitation numbers and pressures occurred for the abrupt contour, but not for the smooth contour using the techniques described for identifying the incipient and desinent cavitation regimes.
Effect of Surface Energy on the Wear Process
Authors: Rabinowicz E. , Foster R. G.
Published: November 2011

It was previously shown that the size of loose wear particles formed during the sliding of two materials is equal to 60,000 Wab/P, where Wab is the surface energy of adhesion and p the penetration hardness. Experimental results are presented which show that the experimental particle sizes obtained with a few materials do indeed obey the theoretical relationship, and that the particle size is, as predicted, almost independent of such external variables as speed, time, geometry, and load, provided the load is not too great. Indeed, if particles of the wrong size are fed into the system, then they tend to be broken down or built up until the correct size is reached. However, changes of atmosphere and the use of lubricants, which alter the energy of adhesion, do have a marked influence on wear-particle size, and this fact suggests a possible use of wear-particle measurement to rate boundary lubricants. Other surface interaction phenomena which are governed by the W/p ratio are discussed, and it is suggested that the surface roughness generated during sliding is a function of this ratio.
The Effect of the 150-Degree Partial Bearing on Rotor-Unbalance Vibration
Authors: Warner P. C. , Thoman R. J.
Published: November 2011

The effect of a centrally loaded 150-deg partial bearing on the transmission of unbalance force is determined for a simple, symmetrical rotor-bearing system considering both static and dynamic unbalance. Design curves giving force transmission, mass and journal vibration, and oil-whip stability limits are included.
Compressible Squeeze Films and Squeeze Bearings
Authors: Salbu E. O. J.
Published: November 2011

Experimental agreement with a finite-difference solution of the isothermal squeeze film equation was obtained for steady-state sinusoidal squeeze motion of parallel, coaxial disks. At low squeeze number, the film force is in phase with the velocity; at high squeeze number, with the displacement. Compressibility effects at high squeeze number introduce a superambient mean film pressure, so that it is possible to operate a gas bearing on squeeze effects alone. Thrust bearings, spherical bearings, and journal bearings have been successfully operated as squeeze bearings, using both electromagnetic and piezoelectric devices to generate the squeeze motion.
Dynamics of Externally-Pressurized Sliders With Incompressible and Compressible Films
Authors: Licht L. , Cooley J. W.
Published: November 2011

The ability of an externally-pressurized slider to follow faithfully the runout, or waviness of a rotating disk, or drum are investigated. The response and the stability of the slider are considered in terms of small displacements from the equilibrium gap width. The first part of the analysis treats the case of an incompressible lubricant. The dynamic Reynolds equation is integrated with respect to the space coordinate and the relative displacement of the slider is described by a nonlinear, second-order differential equation. Peturbation solutions are obtained, which permit successive approximations of small deviations from the equilibrium gap width. The second part of the analysis treats the case of a gaseous lubricant. A quasi-static variation of the pressure field is assumed and the problem is stated in terms of lumped parameters. The continuity equation and the equation of motion are linearized, yielding a third-order differential equation for small displacements of the slider from the equilibrium gap width. Results are discussed, with particular reference to the effect of the squeeze number, σ, on the response of the slider.
Optimal Bang-Bang Control With Quadratic Performance Index
Authors: Wonham W. M. , Johnson C. D.
Published: November 2011

The following optimal regulator problem is considered: Find the scalar control function u = u(t) which minimizes the performance index J[u]=  12∫0T〈x(t),Qx(t)〉dt, subject to the conditions x˙=Ax+u(t)f,|u(t)|≦1x(0)=x0(x0isunrestricted)x(T)=0(Tisfree)Q, A are constant n × n-matrices; f is a constant n-vector. It is shown that optimal control includes both a bang-bang mode and a linear mode, the latter arising from the “singular” solutions of the Pontriagin canonical equations. Conditions are given under which nth-order systems are equivalent, for control purposes, to systems of first or second order. One example of a second-order system is worked in detail and some results of an analog computer study are presented.
Amplitude Frequency Response Analysis and Synthesis of Unfactored Transfer Functions
Authors: Ausman J. S.
Published: November 2011

A graphical method provides, without templates and without factoring, a means for rapidly estimating log-amplitude versus log-frequency response curves from transfer functions in their unfactored polynomial form. The technique can also be used to design or synthesize transfer functions which will produce a specified frequency response characteristic. Included is a graphical stability criterion for third and fourth-order systems which provides a quick check on system stability during the course of design or of analysis of the system response.
Analytical Representation of the Root-Locus
Authors: Wojcik Charles K.
Published: November 2011

A technique for analytical representation of the root-locus is developed in this paper for both negative and positive feedback. With the help of the derived general equation for the root-locus, such items as intersection of the asymptotes, break-away points, and intersection of loci with imaginary axis are investigated and defined. Simple examples of possible applications are given. Finally, a number of selected root-loci and their equations are shown.
The Rheological Behavior of the Lubricant in the Contact Zone of a Rolling Contact System
Authors: Bell J. C. , Kannel J. W. , Allen C. M.
Published: November 2011

A technique has been developed for studying the rheological behavior of the lubricating film within the contact zone of rolling contact bodies. This is accomplished by rolling two contacting disks together with a small amount of sliding superimposed on a relatively high rolling velocity. By measuring the traction, slip-rate, and the lubricant film thickness in the elastically deformed contact, a plot of traction versus mean shear rate can be made. Data are presented for polyphenyl ether. The data depend on the disk temperature and contact pressure qualitatively as would be expected, but the observed dependencies on shear rate and rolling speed require explanation. Analysis of possible local thermal disturbances on the lubricating film assuming a Newtonian lubricant model indicates that, for the experiments described here, temperature changes only partially explain the observed nonlinear variations of traction with shear rate, and fall far short in accounting for variations with rolling speed. A study assuming isothermal conditions and a Ree-Eyring lubricant model provides a traction theory which is flexible enough to fit the variations with shear rate, if certain parameters have advantageous values, but which appears only partially able to correlate the variations with rolling speed. Thus additional analyses which consider, say, both non-Newtonian and thermal effects or perhaps other entities are necessary for interpreting the data.
The Effects of Misalignment on the Forces Acting on the Retainer of Ball Bearings
Authors: Kakuta K.
Published: November 2011

The forces acting on the retainers of rotating radial ball bearings were measured by wire strain gauge. The bearings were operated under radial and/or thrust load with misalignment, that is, relative inclination between inner ring and outer ring, and also under pure moment load. The mechanism of generating the forces is analyzed theoretically, and the cause of seizure or fatigue rupture of the retainers under such conditions is made clear.
Isothermal Bulk Modulus of Selected Fluids to 700 F and 10,000 Psig
Authors: Hopkins V. , Wilson D. R. , Bolze C.
Published: November 2011

An apparatus has been designed and fabricated which is suitable for collecting bulk-modulus data to 10,000 psig and to 750 F, and results are presented for seven fluids to 700 F. A program has been written for an IBM 1620 computer for use in reducing experimental data to both isothermal secant and tangent bulk-modulus values. Bulk-modulus curves are presented for a chlorinated phenyl methyl silicone (MLO 56-843), hexa-2-ethylbutoxydisiloxane (MLO-8200), phenyl methyl silicone (QF-258), a deep dewaxed mineral oil (MLO 60-294), an ester of TMP (MLO 60-50), di-phenyl-di-n-dodecyl silane (MLO 57-637), and bis(phenoxyphenoxy)benzene (MLO 59-692). The bis(phenoxyphenoxy)benzene exhibited the highest bulk-modulus values and the chlorinated phenyl methyl silicone exhibited the lowest. At the 67 percent confidence level, the standard error about the bulk-modulus curves ranged from ±0.1 percent to ±2.53 percent.
Cavitation Tests on Hydrofoils Designed for Accelerating Flow Cascade: Report 3—Five Profiles Generated From Prescribed Pressure Configurations of Types 1 and 3
Authors: Numachi F.
Published: November 2011

It has been demonstrated that profiles can be found which manifest extremely favorable characteristics when used as blade elements of a given cascade formation. The method of developing such profile forms is to begin by prescribing a suitable configuration for the pressure distribution around the profile, and then to work out theoretically the profile outline that should create the predetermined pressure distribution. In pursuance of the studies described in Reports 1 [1] and 2 [2] of the present series, five newly developed profiles were selected for tests, taking due account of the experience gained with the previous experiments. One of the profiles tested proved to yield performance superior to any tried so far.
Dynamic Response of Fluid Lines
Authors: D’Souza A. F. , Oldenburger R.
Published: November 2011

The use of hydraulic transmission lines in automatic control, liquid-propellant rocket, and other systems requires accurate knowledge of their dynamic response. In this paper the effects of fluid viscosity and compressibility are included to derive transfer functions relating the pressure and velocity variables at the two cross sections of a line. The results of theoretical analysis are compared with experimental data obtained from frequency-response tests. The analysis includes the significant effect on the dynamic response caused by the natural frequency of vibration of the line in the longitudinal direction. It is shown that in small-diameter lines the viscous effects cannot be neglected. The theoretical analysis may be used to improve the performance of systems incorporating hydraulic networks.