bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress-Corrosion Susceptibility of High-Strength Steel, in Relation to Fracture Toughness
Authors: Mulherin J. H.
Published: November 2011

The stress-corrosion susceptibility of several ultrahigh-strength ferrous alloys is described on the basis of fracture-mechanics parameters. Two general conditions were considered: First, the susceptibility of a material at various levels of tensile yield strength and fracture toughness; and second, the susceptibility as a function of applied subcritical stress-intensity levels. Experimentally, a notched and fatigue-cracked bendbar specimen configuration was used. Under a subcritical load, fracture of the specimen occurs upon sufficient environmentally influenced crack extension. The susceptibility criterion adopted in this investigation was the time period to catastrophic fracture of the specimen. The results are evaluated in terms of strength level and fracture toughness, and the usefulness of the data generated is examined in terms of material evaluation and application.
Cumulative Damage and Effect of Mean Strain in Low-Cycle Fatigue of a 2024-T351 Aluminum Alloy
Authors: Ohji Kiyotsugu , Miller W. R. , Marin Joseph
Published: November 2011

By assuming a linear cumulative damage hypothesis for strain cycling, theories are developed in this paper for fatigue life under varying strain amplitude, residual ductility after a given history of strain cyling, and life under mean strain condition. These predictions are based on uniaxial completely reversed cycling behavior. The expressions obtained were compared with the experimental results on 2024-T351 aluminum alloy as well as other data available in the literature. The agreements between theories and experiments were found to be satisfactory.
On A Priori Statistics in Minimum-Variance Estimation Problems
Authors: Soong T. T.
Published: November 2011

Simple general formulas are derived for investigating the effect of errors in a priori statistics on the minimum-variance estimates of linear regression parameters from observations obscured by noise. These formulas permit a direct evaluation of the covariance matrix of the errors of a posteriori estimates, showing the sensitivity to errors in a priori weighting matrix. A simple example illustrates that, for slight variations in the assumed a priori statistics, the calculated a posteriori error standard deviations of the estimates can deviate substantially from the correct values.
Stability Analysis of Gas-Lubricated, Self-Acting, Plain, Cylindrical, Journal Bearings of Finite Length, Using Galerkin’s Method
Authors: Cheng H. S. , Pan C. H. T.
Published: November 2011

This paper extends the method of Cheng and Trumpler [5] to study stability of plain cylindrical gas journal bearings of finite length. Both equilibrium and stability results have been obtained.
Misalignment Torques of Hydrodynamic Gas-Lubricated Journal Bearings
Authors: Rice John R.
Published: November 2011

Design curves for misalignment torques are presented which are valid for high eccentricity ratios. Instead of perturbation analysis, numerical analysis is used to solve the governing Reynolds equation. A comparison of the two methods is also included.
Solution of the Stability Problem for 360 Deg Self-Acting, Gas-Lubricated Bearings
Authors: Castelli V. , Elrod H. G.
Published: November 2011

This is an investigation of the stability of self-acting, gas-lubricating bearings. Two approaches to the solution are presented and their results are compared. Also, the relation is discussed between the present work and other, more simplified, methods available in the literature. The particular case of a 360 deg journal bearing of infinite length is treated, and the changes necessary to use the same theories with other geometries are pointed out.
An Interpretation of the Mechanics of Crack Growth by Fatigue
Authors: Cotterell B.
Published: November 2011

A theory for the growth of cracks by fatigue is developed that is analogous to the brittle fracture of high strength materials. It is argued that it is possible to describe crack growth with a curve of resistance which is dependent on the alternating stress at low rates of crack propagation. At higher rates there is much less dependency on the alternating stress. Once such curves have been prepared the rate of crack growth can be found from the value of the crack driving force. This force is dependent mainly on the maximum stress and crack length.
A Comparison of the Initiation With the Rapid Propagation of a Crack in a Mild Steel Plate
Authors: Eftis J. , Krafft J. M.
Published: November 2011

Recent indications of a direct proportionality between plane strain fracture toughness KIc and the strain hardening exponent n provide a new basis for comparing the initiation with the propagation of a crack. A mild steel from the University of Illinois wide plate studies was employed because of its extensive crack propagation data. With this, the proportionality KIc/n was established at low temperatures. The n values were then measured at service temperatures and also at extremely high strain rates, to 6000/sec, with bar impact loaders. The additional speed range delineates a series of minimum fracture toughness levels even at temperatures above the NDT or CV15. A plot of adiabatic minima KIc(Q) as pertinent to the crack arrest temperature and isothermal KIc(T) to crack initiation permits a more quantitative interpretation of the Pellini fracture diagram.
The Choice of Time for Zeroing a Disturbance in a Minimum-Fuel Consumption Control Problem
Authors: Flu¨gge-Lotz I. , Craig Andrew
Published: November 2011

The choice of time T for zeroing an initial disturbance with minimum-fuel consumption influences the dependence of the switching instances on the phase variables. For a set of discrete values of time T this relation can be found easily and mechanized in a simple manner. The restriction of the free choice of time T is so mild that it does not impair the usefulness of the scheme.
A Fluid-Metering Device for Measuring Dive Rate of a Vehicle Traveling in Water
Authors: Bennett M. D.
Published: November 2011

Three configurations of a small device using either incompressible or compressible fluids to indicate the dive speed of a vehicle descending in water are theoretically considered. The device is contained within or on the vehicle, and it consists of a case which houses the fluid, an orifice plate, springs, and a piston that is driven by the increasing water pressure. Equations of the motion are derived for general trajectories, and the resultant fluid pressures are calculated for constant dive rates. The configuration that uses an incompressible fluid appears to be of most practical value.
On the Control of Linear Systems With Pure Time Delay
Authors: Koepcke R. W.
Published: November 2011

A synthesis technique is developed for control systems governed by linear differential-difference equations. It is shown that such a system is equivalent to an infinite-dimensional difference equation whose matrix elements can be calculated readily by recursive formulas. From this it takes but a slight extension of present-day procedures to calculate a stable control.
Electron Fractographic Studies of Mechanical Fracture Processes in Metals
Authors: Beachem C. D.
Published: November 2011

Electron microscope studies of metal fracture surfaces have shown the existence of fine-scale plastic tearing during the early stages of crack growth for a large number of specimens. “Running” fractures in many structural metals (steels, aluminum alloys, and titanium alloys) propagate by the satellite nucleation of one or more different fracture mechanisms with the resultant submerged cracks linking with one another and with the major fracture to form incremental advances of the fracture front. The transition of macroscopically flat fracture to shear lips may occur over distances of about 10 to 100 microns, with the fine-scale fracture mode often changing from that of the fast fracture mode to tearing, normal rupture, and shear rupture. Shear lips always exhibit shear rupture dimples at high magnifications. Fatigue cracks are usually propagated by extremely fine-scale plastic rupture processes.
High Temperature Rupture, Fatigue, and Damping Properties of AISI Designation 616 (Type 422 Stainless) Steel
Authors: Matters R. G. , Blatherwick A. A.
Published: November 2011

This paper covers the high temperature rupture, fatigue, and damping properties of AISI Designation 616 (Type 422) steel conforming substantially to the requirements of ASTM specification A437 grade B4C. This material has been extensively used for boiling and for steam turbine blading for service in the temperature range of 850 to 1000 F. The results of stress rupture and fatigue tests of smooth and notched bars at 800, 950, and 1050 F are presented. Stress rupture tests extend to 2000 hr or more and fatigue tests generally extend to 2 × 107 cycles or about 100 hr. The fatigue tests were performed in a direct stress machine at stress ratios A = infinity, 2.5, and 1.0. Vibration decay damping tests with various mean stresses were performed at 75, 800, 950, and 1050 F.
A Set of Fatigue Failure Criteria
Authors: Fuchs H. O.
Published: November 2011

A set of three criteria is presented: One for crack nucleation, one for crack propagation, and one for yielding. In combination these three criteria simply explain known data on long-life fatigue, especially the strong effect of mean stress on the notch factor and nonpropagating cracks. Criteria for propagation and yielding are given only in first approximation; the former because a first approximation seems adequate, the latter because of lack of data on yielding in fatigue.
The Effect of Quench Aging and Cyclic-Strain Aging on Low Carbon Steel
Authors: Coffin L. F.
Published: November 2011

The present paper is an extension of a previous investigation, and considers the effects of various quench aging treatments on SAE 1010 and 1111 subjected to cyclic strain at aging temperatures. For both of these steels prior quench aging leads to much greater cyclic strain hardening at 250 deg C than was observed from the annealed condition. The strain aging effect was found to be sensitive to the severity of the quench and to strain rate. Cyclic-strain softening was observed when the temperature was restored to room temperature. Of considerable interest is the effect of these general cyclic-aging treatments on subsequent mechanical properties. The fracture ductility of annealed and quenched aged, cyclic-strain aged SAE 1111 was investigated as a function of temperature for uniaxial tension. It was found that the temperature for low ductility, cleavage-type fracture varied considerably depending on the pretreatment. In particular, quench aging and cyclic straining at 250 deg C raised this temperature to slightly below room temperature. The significance of these observations to the behavior of welded joints is discussed. The response of these metals to low-cycle fatigue is also examined.
Effects of Repeated Loading and Moisture on the Fracture Toughness of SAE 4340 Steel
Authors: Van Der Sluys W. A.
Published: November 2011

This investigation determined the combined effect of water vapor and repealed loading on slow crack growth and fracture toughness. Round notched bars of SAE 4340 steel with a Rockwell C hardness of 48 were tested in tension, in a controlled environment, and at room temperature. The compliance of the specimen was measured on each cycle and was used to determine the amount of crack growth. It appears that the GIc values (fracture toughness) may be lowered slightly as the moisture content of the atmosphere increases. It was also found that the water vapor alone assists slow crack growth, but that water vapor combined with repeated loading has a greater effect. The effect can be easily seen by looking at the ratio σn′σys where σn′ is the stress level sufficient to cause either slow crack growth or failure in less than 100 cycles. An interesting result is that if a specimen was cycled in the 100 percent relative humidity condition and with a natural crack present, the σn′σys ratio was found to be about 0.30 while it was about 0.55 if no moisture was present.
Initial Phases of Damage to Test Specimens in a Cavitating Venturi
Authors: Hammitt F. G. , Barinka L. L. , Robinson M. J. , Pehlke R. D. , Siebert C. A.
Published: November 2011

The detailed characteristics of pitting in the early phases of cavitation damage incurred by test specimens inserted into the diffusing portion of a cavitating venturi are shown pictorially and discussed in terms of degree of cavitation, fluid, material, duration, and velocity effects. Quantitative damage results are presented from these tests for mercury and water as test fluids and for a variety of test materials. Various possible damage correlating parameters are discussed and examined.
Distortion of Short Pulses in Tapered Tube Pulse Transformers. Part II—Viscous Liquid
Authors: Rouleau W. T. , Young F. J.
Published: November 2011

A short pulse of pressure or volume flux can be changed in magnitude by sending it through a tapered tube. However, both the geometry of the taper and viscous shear cause the pulse to become distorted. In this paper a method of analysis is developed which allows the distortion to be quantitatively determined for pulses that are transmitted through viscous liquids. Viscous shear is shown to round the leading and trailing edges of the pulse, and geometry causes the top of the pulse to be sloped if it is initially flat.
Laminar Boundary Layers and Their Separation From Curved Surfaces
Authors: Massey B. S. , Clayton B. R.
Published: November 2011

The equation of motion in a laminar boundary layer on curved surfaces has been developed from the Navier-Stokes equations. After an order-of-magnitude analysis terms of highest and next order have been retained and a single ordinary differential equation of motion derived by the method of “similar solutions.” An iteration procedure has been used to determine effects of displacement thickness and surface curvature up to and including separation. The equation of motion has been solved by a digital computer using the Runge-Kutta step-by-step integration technique.
Effect of Surface Roughness on Cavitation Performance of Hydrofoils—Report 1
Authors: Numachi F. , O¯ba R. , Chida I.
Published: November 2011

The effect of surface roughness on hydrofoil characteristics, particularly cavitation performance, was studied experimentally. It was intended to initiate the first of a series of studies to examine the effect on mechanical characteristics, particularly efficiency, of the surface finishing accuracy of blades in axial-flow turbines and pumps.
A Photographic Study of the Dynamics and Damage Capabilities of Bubbles Collapsing Near Solid Boundaries
Authors: Shutler N. D. , Mesler R. B.
Published: November 2011

The effect of proximal rigid boundaries on the motion and damage capabilities of spark bubbles is investigated by means of a qualitative photographic study. It is determined that an axially symmetric bubble collapsing nonhemispherically against a solid boundary can form a liquid jet which impinges against the solid boundary, but the jet has little or no damage capability. Observations of the toroidal minimum volume and associated damage to the boundary in the form of circular dents on indium indicate a pressure pulse damage mechanism.
A Table of the Journal-Bearing Integral
Authors: Booker J. F.
Published: November 2011

A comprehensive list of recursion formulas is given for integrals of the type ∫sinlθcosmθdθ(1+εcosθ)n.
Linearized PH Stability Theory for Finite Length, Self-Acting Gas-Lubricated, Plain Journal Bearings
Authors: Ng Chung-Wah
Published: November 2011

Use of Ausman’s linearized, PH method to determine the threshold of half frequency whirl for a rigid rotor in self-acting cylindrical journal bearings is extended to include finite length effects. Rotating polar coordinates are used to derive the governing equation. Results obtained are generally consistent with several previous works in wide ranges of all parameters. This method is judged to give conservative results and is suitable for studying dynamic problems of more complicated systems.
The Effect of External Pressurization on Self-Acting Foil Bearings
Authors: Wildmann M. , Wright A.
Published: November 2011

The effects of introducing a small amount of lubricant under pressure into a self-acting foil bearing film are investigated. Foil shape and pressure distribution under the foil are obtained by combining the equilibrium equation with the Reynolds’ equation and solving the resulting equation. The results show that the effect of even small external pressurization in a self-acting foil bearing is very important.
Mechanism of Boundary Lubrication and the Edge Effect
Authors: Tamai Y. , Rightmire B. G.
Published: November 2011

Experimental work was carried out on the boundary lubrication of a copper-copper couple with pure cetane, palmitic acid solution of cetane, and some other organic materials. The purpose was to get information about α and μlube, which appear in the friction equation: μ=αμsolid+(1−α)μlube, by using two different kinds of copper surface, a clean surface, and an oxidized surface. α was found to be small with palmitic acid solution, and the estimated shear strength of palmitic acid was high under the examined condition. α and μlube seemed to be properties which are independent of each other. α is closely related to the attraction force between the lubricant and the substrate, whereas μlube is related to the complexity of molecular structure of the lubricant. A comparison was made of bulk-liquid and thin-film lubrication. μlube was smaller in thin-film lubrication than it was in bulk-liquid lubrication. This suggests that the frictional resistance may be partly contributed by liquid in the edge space around the real contact.
Effect of Oxidation on Boundary Friction of Steel in Hydrocarbon Media and Critical Friction Duties Under Which Cold and Hot Seizure (or Welding) Develop
Authors: Vinogradov G. , Korepova I. V. , Podolsky Y. Y. , Pavlovskaya N. T.
Published: November 2011

This paper, a further development of our earlier investigations of heavy boundary friction duties of steel in mineral oils, presents the results of a study of the antifriction, antiwear (and EP) properties of low-molecular individual hydrocarbons. The dependence of the lubricating action of low-molecular hydrocarbons on their nature and on the oxidative activity of the gas phase is such that it improves greatly with the intensity of oxidation in the friction zone. The effectiveness of higher fatty acids as lubricitors under heavy friction duties depends on the oxidative activity of the gas phase and the tendency of the hydrocarbons to oxidize. During a study of the boundary friction of steel in mineral oils in the air and in vacuum with sliding speeds varying over a 108-fold range, it was established that under constant load and temperature both increasing and decreasing the sliding speed may result in seizure. Hot seizure occurs in the former case, cold seizure in the latter.
The Magnetohydrodynamic Parallel Plate Slider Bearing
Authors: Kuzma D. C.
Published: November 2011

The effect of a nonuniform applied magnetic field on the operation of a parallel plate slider bearing is investigated analytically. It is found that the optimum magnetic field profile is a step function. This profile increases the load-carrying capacity while decreasing the friction factor. Results indicate that the nonuniform applied magnetic field is definitely superior to the uniform applied magnetic field.
Calculation of Wear Rate
Authors: Kraghelsky I. V.
Published: November 2011

This paper contains exhaustive analytical data on factors contributing to wear. The wear of a deformed body interacting with an absolutely rigid rough solid is considered. It is believed that wear results from the deformation of a body due to geometrical and mechanical factors and due to the adhesion bonds thereof. Three types of wear are considered: By elastic deformation, by plastic deformation, and by microcutting. The suggested criteria allow us to determine conditions which cause these types of wear to appear. It is shown that the rate of wear, i.e., the ratio of height of the worn layer to the distance of sliding at elastic contact depends on the elasticity modulus, roughness, friction coefficient, nominal pressure, rupture stress of material, and on the power exponent of fatigue curve; at plastic contact it depends on roughness, nominal pressure, hardness, destroying deformation, and friction coefficient; at microcutting—on roughness, nominal pressure, and hardness; wear at microcutting is independent of friction coefficient. The formulas deduced are borne out by experiments. These formulas may be readily modified for the case of two rough surfaces.
Density Effect and Reynolds Number Effect on Gas Turbine Flowmeters
Authors: Lee W. F. Z. , Evans H. J.
Published: November 2011

A simplified analysis of the density effect and the Reynolds-number effect on the performance of a gas turbine flowmeter is presented. The analysis indicates a simple method to determine numerically both the density effect and the Reynolds-number effect by a single calibration of the meter in a convenient gas (air) at any convenient pressure and temperature. Results of the analysis are used to predict meter performance in other gases under other operating conditions. A 6-in. gas turbine meter is used to illustrate the practical application of the analysis.
Torque Produced by Misalignment in Short Lubricated Bearings
Authors: Galletti-Manacorda L. , Capriz G.
Published: November 2011

The torque due to the lubricant, and acting on a journal in a short cylindrical bearing, is derived in the special, and particularly simple, case of a journal whirling and rocking in the neighborhood of its steady-state position under load. The results of the investigation have a bearing in the study of the damping of forced vibrations and of the development of self-excited oscillations of rotors.
Plastic Strain Fatigue in Air and Vacuum
Authors: Martin D. E.
Published: November 2011

The plastic strain-life relation for several ductile materials is examined in both air and vacuum and interpreted in light of the well-known plastic strain (ΔξP) life (N) relation, N1/2ΔξP = constant. These data indicate that the relation applies as well in vacuum as in air and, in certain cases, better and to a much larger number of cycles. Further experiments are described in which these materials are repeatedly fractured and rejoined in vacuum, exhibiting a very substantial capacity for vacuum cold reweldment of completely fractured specimens.
An Elastic-Plastic Curved Bar Analysis
Authors: Tuba I. S.
Published: November 2011

A simple approach is given for the analysis of stress and strain in curved bars when the tangential stress and strain are related by Neuber’s law.
Tip-Clearance Effects in Centrifugal Pumps
Authors: Wood G. M. , Welna H. , Lamers R. P.
Published: November 2011

Several design models of centrifugal pump impellers were tested in water to determine tip-clearance effects on noncavitating and cavitating performance. Although most of these impellers were designed without tip shrouds, three direct comparisons for shrouded versus unshrouded models are included. Within the scope of this investigation, varying degrees of tip clearance produced dissimilar trends in the hydraulic performance for the different design models tested. Fully shrouded impellers consistently yielded inferior cavitation performance as compared to unshrouded versions.
The Flow and Interference Effects of a Body of Revolution and Its Stabilizing Surfaces When at a Small Angle of Attack
Authors: Rodgers E. J.
Published: November 2011

The flow over a body of revolution and its stabilizing surfaces, at an angle of attack, was studied experimentally in order to obtain a better understanding of the real-flow effects as well as the interference effects between components of the configuration. The velocity field about the configuration, the surface flow, and the pressure distribution were obtained with the model mounted in the wind tunnel of the Ordnance Research Laboratory. Analysis of the data showed there is an increase in lift on the body and a decrease in lift on the stabilizing surfaces from that of the isolated components at the same incidence to the flow. The interference effects between components is evidenced by the surface flows and pressure distributions as well as the vorticity distribution calulated from the measured velocity field. The decreased lift on the stabilizing surfaces is clearly related to the flow over the after part of the body.
Some Analytical Aspects of Bubble Dynamics
Authors: Hsieh Din-Yu
Published: November 2011

A unified, systematic survey of the recent developments of bubble dynamics is presented with the emphasis on its analytical aspects. A general formulation of the problem is established first; then it is shown how simplifications may result from the spherical symmetry of the system and the assumption of uniform interior of the bubble. Two classes of problems of physical interest are treated subsequently; namely, the growth and collapse of a bubble, and the bubble in oscillation. In the first category, various aspects of the problem are investigated depending on whether the inertial, the thermal, or the diffusive effect is the dominating controlling factor of the motion. In the second category, the nonlinear mechanical oscillations are discussed, as well as the linear oscillations with thermal and diffusive interactions. The paper concludes with a study of the stability of the spherical symmetry of the flow system.
Supercavitating Foils With Flaps Beneath a Free Surface
Authors: Auslaender J.
Published: November 2011

Linearized airfoil theory—in conjunction with a mapping technique—is applied to the calculation of the forces and moments acting on supercavitating hydrofoils operating near a free surface at very large Froude numbers and zero cavitation number. Only the effects of angle of attack and flap deflection are considered. The results—intended for engineering use—are presented primarily in the form of curves of flap effectiveness, lift curve slope, pitching and hinge moment coefficient, and flap loading versus flap-chord ratio, depth being introduced as a parameter. Lift-drag ratio and hinge moment coefficient as functions of lift coefficient are presented for typical operating conditions.
The Problem of Pneumatic Pressure Lag: Part 2—Unsteady Flow in a Tubing System Closed at One End
Authors: Ducoffe A. L. , White F. M.
Published: November 2011

The results of the steady-state analysis presented in Part 1 are applied to a quasi-steady analysis isothermal flow in constant diameter tubes (with straight-through unions at the extremities) connected to a closed sensing volume. The ranges of transient pressure inputs and geometric variables were chosen to simulate typical missile pressure sensing systems. The effect of high inlet temperature during descent was not studied, all tests being at room temperature. The correlation of theory with experiment for three types of input (impulse, continuous, and shock) is shown to be quantitative over the range of variables studied. It is concluded that the empirical analysis presented herein provides an adequate working theory for pressure lag during transient flight.
Void Fraction Measurements in a Cavitating Venturi
Authors: Smith Willy , Atkinson G. L. , Hammitt F. G.
Published: November 2011

A method is described for obtaining precise measurements of local density (or void fraction) in an axially symmetrical cavitating flow regime wherein a heavy fluid as mercury, molten lead, and so on, is used. The method can be adapted to light fluids by substituting a softer radiation source. Significant information regarding the cavitating flow regime in a particular venturi operating with mercury has been obtained. Among other things it has been shown that regions where substantial damage to test specimens has previously been noted [7] have void fractions of the order of only five percent.
On the Mechanism of Head Breakdown in Cavitating Inducers
Authors: Jakobsen J. K.
Published: November 2011

The mechanism of head breakdown in cavitating inducers, as affected by thermodynamic properties of the pump fluid and scale effects, is discussed. The approach taken by other investigators is presented, and the limitations to cavitation scaling are examined in relation to experimental data. Because of the incomplete correlation with test data observed, a hypothesis is introduced which relates the head breakdown process to an acoustic shock phenomenon at the point of the leading-edge blade cavity collapse. Also, an integrated model for the cavitating cascade blade is developed, which makes it possible to correlate the potential flow cavity cascade model with the influence of thermodynamic properties, the thermostatic approach, and application of bubble dynamic studies to understand how suction performance is limited by inlet pressure.
Analysis of Plain Cylindrical Journal Bearings in Turbulent Regime
Authors: Arwas E. B. , Sternlicht B. , Wernick R. J.
Published: November 2011

This paper presents a simplified steady-state analysis of turbulent lubrication. Load-carrying capacity, attitude angle, and fluid film stiffness for plain cylindrical journal bearings operating in the turbulent regime are presented. Simple, easy to use relations for the calculation of load-carrying capacity were generated. Fluid film stiffnesses are included so that they can be used to calculate system critical speeds. In the analysis presented here, side leakage is neglected; however, existing published data on a 360 deg plain circular bearing were used to establish a correlation factor between laminar and turbulent leakage factors.
Simplification of Hydraulic Line Dynamics by Use of Infinite Products
Authors: Oldenburger Rufus , Goodson R. E.
Published: November 2011

In many hydraulic control and other systems the effect of fluid carrying lines is an important factor in system dynamics. Following electrical transmission line technique a hydraulic line between two cross sections is characterized by a four-terminal network with pressure and flow the interacting variables. Use of this four-terminal network in a variety of system problems leads to transfer functions relating pairs of variables in the system, where these transfer functions are transcendental. These transfer functions cause serious mathematical difficulties when employed for the computation of system transients. The standard mathematical technique of using power series expansions fails in that this yields instability in most applications where this instability does not actually occur. In this paper these difficulties are overcome by writing these functions as quotients of infinite products of linear factors. It is shown that it is necessary to keep only a few of these factors to compute transients accurately. The transfer functions are thus replaced by rational approximations. However, in contrast to the classical lumped constant approach to distributed systems the accuracy of the approximation can be seen from the factors directly, facilitating system analysis and synthesis. The technique applies to electrical transmission lines as well as hydraulic pipes. This method yields a technique for automatically smoothing stepwise transient responses obtained in water hammer studies. Good agreement has been obtained between theory and experiment on the four terminal hydraulic network approach. The paper covers the results of the experiments made in the United States to verify the theory.
A Simple Stability Criterion
Authors: Becker P. W.
Published: November 2011

A quick method is described by which it may be determined for which ranges of gain, K, all the roots of the characteristic equation have negative real parts. These ranges of stability are determined by the relative position of two curves. The curves also indicate where the stability is marginal. The method is especially well suited for multiple loop systems as it is based on the coefficients of the powers of s. The criterion does not require any tables, charts, or special equipment. Few calculations are needed and they are all of the simplest nature with real numbers. Instead of gain K could be a damping ratio, time constant, and so forth.
When Is a Linear Control System Optimal?
Authors: Kalman R. E.
Published: November 2011

The purpose of this paper is to formulate, study, and (in certain cases) resolve the Inverse Problem of Optimal Control Theory, which is the following: Given a control law, find all performance indices for which this control law is optimal. Under the assumptions of (a) linear constant plant, (b) linear constant control law, (c) measurable state variables, (d) quadratic loss functions with constant coefficients, (e) single control variable, we give a complete analysis of this problem and obtain various explicit conditions for the optimality of a given control law. An interesting feature of the analysis is the central role of frequency-domain concepts, which have been ignored in optimal control theory until very recently. The discussion is presented in rigorous mathematical form. The central conclusion is the following (Theorem 6): A stable control law is optimal if and only if the absolute value of the corresponding return difference is at least equal to one at all frequencies. This provides a beautifully simple connecting link between modern control theory and the classical point of view which regards feedback as a means of reducing component variations.
Relative Stability Via the Direct Method of Lyapunov
Authors: Vogt W. G.
Published: November 2011

A mathematically rigorous concept of relative stability based on the v-functions of the direct method of Lyapunov is introduced. Two systems of the type representable by x˙ = f(x) are considered, where under the proper restrictions on f(x), a Lyapunov function, v(x) is uniquely determined by a positive definite error criterion r(x) and the equation v˙(x) = −r(x). The definition of the relative stability proposed, eventually leads to conditions on the linear approximation systems which are sufficient to assure the relative stability of the nonlinear systems. This leads to conditions on the eigenvalues of the linear approximation system which are necessary but not sufficient for relative stability. Additional conditions on the choice of the error criteria are needed. The present definition permits the gap between concepts of stability in classical control theory and that due to the direct method of Lyapunov to be at least partially bridged.
Analysis of an Improved Planetary Gear-Transmission Bearing
Authors: Harris T. A. , Broschard J. L.
Published: November 2011

In planetary-gear transmissions, especially for aircraft applications, the planet gears are frequently made integral with the outer rings of rolling bearings. Thus the outer ring of the rolling bearing is subjected to the tangential, radial, and moment loading attendant to spur gears. If the outer ring of the bearing is relatively thin, the distortion induced therein by the gear forces alters the distribution of load from that of a roller bearing with a rigid outer ring, causing a significant reduction in the bearing fatigue life. Since the maximum rolling-element loads in the bearing occur in close angular proximity of the points of load application, it would appear that the magnitude of these rolling-element loads may be diminished and fatigue life subsequently increased by selectively applying clearance between rolling elements and raceway at the points of load application. In fact, theoretical analysis of a planetary-gear bearing having an out-of-round inner ring, wherein the major axis is oriented parallel to the tangential gear-tooth load, indicates that a condition of optimum clearance and out-of-round exists with respect to bearing fatigue life. An increase in fatigue life of approximately 40 percent is indicated with only a nominal amount of out-of-round.
Performance Characteristics of Elbow Flowmeters
Authors: Murdock J. W. , Foltz C. J. , Gregory C.
Published: November 2011

The state of the art for metering flow with elbow meters is surveyed and past work is correlated with recent data from tests at the Naval Boiler and Turbine Laboratory. The elbow meter is compared with the orifice, Venturi, and flow nozzle and areas where research is needed are delineated.
Calculations of Real-Gas Effects in Flow Through Critical-Flow Nozzles
Authors: Johnson Robert C.
Published: November 2011

Computer calculations have been made of how real-gas effects modify the conventional one-dimensional equations for mass flow of air, nitrogen, oxygen, hydrogen, argon, helium, and steam through a nozzle. The results indicate that for critical flow of air, at room temperature and 100 atmospheres pressure, real-gas effects of 3 1/2 percent exist. Similar magnitudes are found for the other gases.
Choked Flow About Vented or Cavitating Hydrofoils
Authors: Fabula A. G.
Published: November 2011

Linearized theory for two-dimensional, choked-tunnel flow is developed for a vented or cavitating hydrofoil midway between infinite parallel walls, when the upper and lower free streamlines detach at an arbitrary chordwise location and at the trailing edge, respectively. Superposition of step-profile solutions gives the arbitrary-profile solution. Numerical calculations are made for two vented hydrofoils for exhaust at 30 percent chord and tunnel height-to-chord ratio of 3.5. The agreement with experiment becomes good after correction for the pressure at the test-section, static-pressure tap due to the hydrofoil and the cavity. Various aspects of the comparison for equal cavity number of choked flow with unbounded flow are discussed.
Symmetric, Rotational, Supercavitating Flow About a Slender Wedge
Authors: Street R. L.
Published: November 2011

Two approximations to the linearized theory for supercavitating flow about slender bodies are applied to the case of a symmetric, rotational flow about a slender wedge. Both approximations produce relationships for the cavity length and drag coefficients; one approximation also gives certain nonunique solutions not encountered in the corresponding irrotational flow. The presence of rotation is shown to create significant changes in the length of the trailing cavity, but small changes in the drag coefficient.
Analysis of Normal Shock Waves in Particle Laden Gas
Authors: Kriebel A. R.
Published: November 2011

The internal structure of a normal shock wave in a perfect gas heavily laden with particles having a distribution of sizes is machine computed by numerical integration. The results of a small-perturbation analysis for weak shock waves and one particle size compare well with the machine-computed results for these restricted conditions. Both methods indicate that the thickness of weak shock waves increases in proportion to the particle size squared and inversely with the shock strength. For conditions typical of solid propellant-rocket motor exhaust streams the computed shock-wave thickness is several inches. With such computed results both the amount and the size distribution of suspended particles can be found individually from shock-wave measurements.
A Numerical Procedure for Estimating the Stress Intensity Factor of a Crack in a Finite Plate
Authors: Kobayashi A. S. , Cherepy R. D. , Kinsel W. C.
Published: November 2011

The advantages of the complex variable method are combined with the numerical procedure of collocation for estimating the stress intensity factors in finite, cracked plates subjected to in-plane loadings. In this approach, the complex stress functions for an infinite plate problem are modified to meet the boundary conditions for a finite plate with identical crack configuration. This procedure produces a system of linear equations which can be programmed readily on high-speed computers. The procedure is used to find the elastic stress intensity factor at the crack tip in a centrally notched plate in uniaxial tension. The resulting values are nearly identical to the stress intensity values determined analytically by the theory of elasticity. This numerical procedure should be useful for designers and analysts working in the fields of fracture mechanics and fail-safe concepts.
Part-Through Crack Test—Relation to Solid-Propellant Rocket Cases
Authors: Randall P. N. , Felgar R. P.
Published: November 2011

Propagation of a crack from a flaw that escaped nondestructive inspection is shown to be an important mode of failure of rocket motor cases. The notch strengths of part-through crack tensile specimens containing a range of flaw sizes provide a good empirical measure of the material property that governs this mode. Flaw sizes in the specimens simulate those found in failure analyses of Minuteman cases. Starting from this basic simulation of service, it seems possible to correct for the remaining difference between the case and the specimen by experimental and analytical means.
Vane Systems for Very-Wide-Angle Subsonic Diffusers
Authors: Feil O. G.
Published: November 2011

Experiments with straight-walled, two-dimensional subsonic diffusers having total divergence angles of 40, 60, and 80 deg and area ratios from 3 to 5 are reported. The performance of these diffusers was improved by means of vanes placed in the inlet section of the diffusers. The basic concept of the vane systems used and a procedure for their design are described.
Some Details of the Structure of an Axisymmetric Confined Jet With Backflow
Authors: Barchilon M. , Curtet R.
Published: November 2011

The approximate theory of confined jets, as shown in earlier papers [1, 9, 12] is applicable to the case of an axisymmetric jet with backflow. The assumptions usually made, however, are not valid downstream of the core of the recirculation center; the authors have made measurements of the mean and fluctuating velocities and have developed a method of visualization of the instantaneous flow patterns. Because of the high turbulence levels, any future extension of the theory of the region downstream of the recirculation center should allow for the variation in secondary-stream energy, the hitherto neglected fluctuation terms, and the variation of a shear-stress coefficient along the duct axis.
Velocity and Static-Pressure Distributions in Swirling Air Jets Issuing From Annular and Divergent Nozzles
Authors: Chigier N. A. , Bee´r J. M.
Published: November 2011

Mean-velocity and static-pressure measurements have been made in a series of swirling air jets issuing from annular and divergent nozzles into stagnant-air surroundings. Swirl was generated by introducing varying proportions of air through tangential ports while the remainder of the air was introduced axially. A region of subatmospheric pressure is set up in the central region of the jets and as soon as the pressure gradients on the axis exceed a certain critical value, reverse flow is set up with an associated internal ring vortex. With increasing degrees of swirl, the angle of spread of the jets is increased and, correspondingly, the decay of the maximum values of axial, tangential, and radial components of velocity along the lengths of the jets is faster. The integrated axial fluxes of linear and angular momenta were shown to be conserved along the length of the jets.
The Flow Region Near the Nozzle in Double Concentric Jets
Authors: Chigier N. A. , Bee´r J. M.
Published: November 2011

The type of double concentric jets considered in this paper consists of a central round air jet surrounded by an annular air jet issuing into stagnant air surroundings. Detailed measurements of the mean velocity and static-pressure distributions have been made in the region close to the exit of the nozzles and the effect of varying the ratio of the velocities in the central and annular jets has been examined.
Supercavitating Cascade Flow Analysis
Authors: Jakobsen J. K.
Published: November 2011

An exact mathematical theory of supercavitating flow in cascades with arbitrary blade shapes is developed. Applying conformal mapping methods to the potential flow problem involved, a general mapping procedure is established. The geometric interpretation of the obtained mappings is discussed in general and completed in the case of the flat-plate cascade. Furthermore, for this case, a procedure has been established for computing the shape of the free streamline issuing from the leading edge. All results assume infinitely long cavities. The application of the established mapping procedure to the case of a cascade with arbitrary blade shape requires the solution of a nonlinear integral equation for one of the mapping functions, or the approximation of this mapping function by a Fourier series whose coefficients must be determined from implicit conditions imposed by the blade shape. In the case of a circular-arc blade, the integral equation may be rearranged in a form suitable for numerical evaluation of the integral involved, thereby opening the way for its solution by numerical iteration.
On the Generation of Secondary Velocity Along a Vortex Line
Authors: Marris A. W.
Published: November 2011

A general expression for the generation of secondary velocity along a vortex line is developed for the case of incompressible flow with uniform viscosity. The result is given with various degrees of specialization, i.e., for unsteady flows, unsteady circulation-preserving flows, flows with vanishing flexion, and steady inviscid flows. The formulation for the case of steady flow in which the direct action of viscosity is discounted is applied to the rationalization of experimentally observed secondary-flow phenomena at the convex wall for entrance flow in a curved channel of rectangular cross section.
Fully Developed Turbulent Flow in Annuli
Authors: Brighton J. A. , Jones J. B.
Published: November 2011

For annular pipes with diameter ratios from 0.0625 to 0.562 and with Reynolds numbers from 46,000 to 327,000, mean-velocity distributions and the location of the maximum mean velocity for each flow condition are presented. The point of maximum mean velocity in turbulent flow occurs at a smaller radius than in laminar flow. Velocity profiles are compared with the law of the wall and the velocity-defect law and are found to deviate from the usual correlations whenever the radial distribution of Reynolds stress, which was also measured, is far from linear. This occurs in the inner profiles for small diameter ratios. Mixing length and eddy-viscosity distributions were determined from accurate measurements of velocity gradients. Turbulence intensity distributions are presented, and these in conjunction with already published distributions for flow in circular pipes and for flow between parallel planes provide knowledge of turbulence-intensity distributions for all cases of fully developed, one-dimensional flow.
Lubrication Review: Developments in Bearings and Lubricants—a Digest of the Literature From 1962–1963
Authors: Hays D. F. , McHugh J. D. , Klaus E. E. , Wojtowicz W. J. , Hartung H. A. , Renkey E. J. , Ryffel H. H. , Derner W. J. , Ramadanoff D. , Sibley L. B. , Kingsbury E. P.
Published: November 2011

The 1962–1963 Lubrication Review brings together information on publications relating to several aspects of the broad field of lubrication. Although it does not cover all of the significant domestic and foreign publications in this field, it does summarize many of the results of current theoretical and experimental investigations. It also indicates themes or patterns of current programs relating to lubrication. The review is more than a list of references since each reviewer has commented on the essential elements or results reported by the investigators. The areas reviewed include fluid-film lubrication, developments in lubricants, metalworking lubricants, automotive lubricants, gear lubrication, boundary lubrication, rolling element bearings, and friction and wear. It is hoped that those who are currently involved in these specific areas will find the review helpful in summarizing recent developments in these areas and that those who are interested in extending their knowledge of lubrication theory and practice might find the review to be a helpful guide.