bluuebunny/crossref_metadata_2025 huggingface dataset:
Similarity Solutions of Laminar, Incompressible Boundary Layer Equations of Non-Newtonian Fluids
Authors: Hansen A. G. , Na T. Y.
Published: November 2011

A similarity analysis is made of the steady, two-dimensional, laminar boundary layer flow of non-Newtonian fluids. The important conclusion drawn from this analysis is that for non-Newtonian fluids of any model, similarity solutions exist only for the case of a wedge flow of 90 deg. The only limitation is that the stress and rate-of-strain can be related by an arbitrary continuous function. The result in this paper further extends a recent work by Lee and Ames [11]. Numerical solutions for the Powell-Eyring model are presented in dimensionless form as an engineering application of the theory.
The Behavior of a Spherical Bubble in the Vicinity of a Solid Wall
Authors: Shima A.
Published: November 2011

The behavior of a spherical bubble as it collapses in the vicinity of a solid wall was theoretically analyzed, in terms of the effect of compressibility, viscosity, surface tension, and gravity being ignored, and the gas in the bubble following the adiabatic law of compression assumed. Numerical examples obtained by applying the theoretical treatment are given for the change in time of bubble shape as it collapses, the impulse pressure occurring during bubble collapse, and the flow velocity at the bubble surface.
Vent Effects on the Response of a Proportional Fluid Amplifier
Authors: Healey A. J.
Published: November 2011

Fluid amplifier dynamic response can be a limiting factor in the design of closed-loop systems. An approximation analysis is presented which extends previous work to include the effect of vent fluid, the inertia and friction of which combine to provide additional dynamic lags. Experimental frequency response results obtained using water show reasonable correlation over a range of supply pressures, indicating that for some amplifier designs, vent effects cannot be neglected.
A Differential Pulse-Length Modulated Pneumatic Servo Utilizing Floating-Flapper-Disk Switching Valves
Authors: Goldstein S. R. , Richardson H. H.
Published: November 2011

A novel approach to gas servo design is presented which provides closed-center operation while eliminating close clearance sliding seals and elastic members. Pulse-length modulated pressure waves having zero quiescent pulse width are used to actuate a new type of switching valve termed a “floating flapper disk.” Signal generation and modulation as well as power-level flow control are shown to be possible using this novel valve. System performance is discussed and compared with that of an equivalent linear servo. A prototype system fabricated to demonstrate feasibility is described. The valving concepts described are adaptable to digital, bang-bang, and optimally switched fluid control systems.
Two Models for Cavity Flow—A Theoretical Summary and Applications
Authors: Street R. L. , Larock B. E.
Published: November 2011

A summary is given of two-dimensional, steady-state, nonlinear theory for two finite-cavity models and their solutions. Two applications are described. First, the influence of the foil’s depth of submersion below a free surface on cavity length and foil performance is described. Second, the effect of a blunt nose on a circular-arc hydrofoil is examined.
A Biaxial Fracture Criterion for Porous Brittle Materials
Authors: Babel H. W. , Sines G.
Published: November 2011

The Griffith criterion for fracture of brittle materials is based on a model of a continuum in which infinitely sharp cracks are distributed with random orientations. This study extends the Griffith analysis to cracks of finite sharpness. While the Griffith criterion predicts a compressive strength of eight times the tensile strength, the extended criterion predicts a compressive strength of any value from three to eight times the tensile strength depending on the sharpness of the cracks. To test the validity of the extended criterion, tests were conducted on porous zirconia under ratios of compressive to tensile stress of 0, 3, and 5, and under compressive stress. A specimen was designed and test procedures developed so that the average bending stress was 1.99 percent. A test program was designed so that a statistical confidence limit could be assigned to the test results. The test results of the proposed criterion fell within a 99 percent confidence band, while all other criteria fell outside of the band for many combinations of tensile and compressive stress. The average compressive strength of the porous zirconia was approximately 7.1 times the tensile strength.
The Thermal Ratchet Mechanism
Authors: Burgreen D.
Published: November 2011

Thermal ratcheting is the cyclic growth of a structure that is subjected to successive cycles of heating and cooling. The mechanism of thermal ratcheting in a simple two-element assembly is investigated. The conditions required for nonratcheting captive thermal cycling and for ratcheting cyclic growth are defined and a method is developed for computing the magnitude of the plastic strains and the cyclic growth.
The Dynamics of a Heated Free Jet of Variable Viscosity Liquid at Low Reynolds Numbers
Authors: Glicksman L. R.
Published: November 2011

To spin polymers or glass into continuous fibers, molten material is forced through a nozzle into air forming a free liquid jet. The jet is cooled as it proceeds through the air and the cold fiber is collected on a rotating drum. The drum maintains tension on the jet causing it to attenuate as it cools. The behavior of a variable viscosity jet of glass was studied analytically and experimentally. In the analysis, it was assumed that the velocity and temperature distributions within the jet were one dimensional. Predictions of the jet shape, the temperature distribution and the tension in the jet as a function of the material properties and the process variables were obtained. Measurements of the jet shape and the tension distribution in the jet were made for various values of the flow rate, the collecting drum speed, and the nozzle temperature. The analytical predictions were found to be in error in the region of the jet within three to four nozzle diameters of the nozzle exit; below this point the theoretical and experimental results were in good agreement.
Jet Impact and Cavitation Damage
Authors: Canavelis R.
Published: November 2011

On the basis of presently known erosion theories, an analogy is made between jet impact and cavitation erosion, and confirmed by experiments. As a consequence of this analogy, data on jet impact experiments are used to explain some peculiar aspects of cavitation damage.
Interaction of a Sloshing Liquid With Elastic Containers
Authors: Bauer H. F. , Hsu Teh-Min , Wang J. Ting-Shun
Published: November 2011

The coupled oscillations of a liquid partially filled container having an elastic bottom or elastic walls have been studied. Two different tank configurations, a rectangular and a circular container both with flat bottoms are considered. For the cases where the flexibility of the container walls of a rectangular tank are taken into account, the lowest frequency of the system occurs when the tank is completely filled. The frequency increases as the depth of the liquid decreases. The corresponding natural frequencies for a rectangular tank having one flexible wall only are slightly higher. The effect of flexibility of the bottom of a rectangular tank shows a reduction of natural frequencies of the system. The frequency increases as the depth of the liquid increases and gradually approaches to the value corresponding to that of the rigid container. The more flexible the bottom, the lower the frequency will be. For a circular cylindrical container the frequency increases with increasing wall thickness and exhibits lower values for larger liquid heights.
Unsteady Rotating Flow in a Cylinder With a Free Surface
Authors: Goller H. , Ranov T.
Published: November 2011

The investigation deals with the “spin-up” of the liquid partially filling a right circular cylinder which is impulsively accelerated from rest to a constant angular velocity. By application of certain simplifying assumptions, a simplification of the Navier-Stokes equations is obtained and numerically solved, obtaining the unsteady angular velocity distribution of the liquid and the configuration of the liquid’s free surface, as it approaches, asymptotically with time, a paraboloid. The simplifying assumptions are qualitatively verified by experiment. Measurement of the theoretically predicted free-surface configuration is obtained by an electrohydraulic servosystem designed and developed for the problem. Good agreement between experiment and theory is obtained.
The Near-Wake of a Circular Cylinder in Crossflow
Authors: Hanson F. B. , Richardson P. D.
Published: November 2011

The flow in the near-wake of a circular cylinder was measured with hot-wire anemometry. Processing of the large body of data on unsteady features of the flow was aided with a digital computer. The major sets of results are for Reynolds numbers of 10,600 and 53,000. The results are presented in several complementary forms. In discussion of the results it is shown how they relate to the generation and maintenance of the Strouhal frequency, the existence and discussion of velocity spikes, the control of heat transfer, and to greater irregularity at lower Reynolds numbers. Some issues are raised in the processing of nonstationary random data.
Fluctuating Lift Forces on Aerofoils Moving Through Transverse and Chordwise Gusts
Authors: Horlock J. H.
Published: November 2011

An analysis is given for determining the lift fluctuation on an aerofoil due to a gust parallel to the undisturbed flow. By combining the new analysis with an established theory for “transverse” gusts perpendicular to the undisturbed flow, it is possible to obtain the fluctuating lift on a rotating fan or compressor blade moving through a flow disturbance. It is shown that simple design rules may be derived for fans and compressors if the fluctuating lift forces, and possibly therefore the associated noise, are to be reduced.
On the Calculation of Unsteady Nonlinear Three-Dimensional Supersonic Flow Past Wings
Authors: Kacprzynski J. J. , Ashley H. , Sankaranarayanan R.
Published: November 2011

A comprehensive study is made of factors influencing the accuracy of predicted thickness effects on the flow due to oscillatory motion of a sweptback wing in supersonic flight. For a delta planform with its leading edge swept at or near the Mach angle, the streamlines and velocity pattern due to thickness are found to be highly three-dimensional. Based on this observation, improvements are suggested to previous approximate second-order theories for the unsteady loading. Numerical examples are presented for a 45 deg della which indicate a substantial difference between the linearized and nonlinear pressure distributions. Although a greater volume of computation is needed to guarantee adequate accuracy, practical means are described for the complete numerical solution of problems of this type.
An Experimental Investigation of the Formation and Flow Characteristics of an Impulsively Generated Vortex Street
Authors: Asher J. A. , Dosanjh D. S.
Published: November 2011

In this shock tube investigation, the passage of a plane normal shock wave and its associated drift flow over a two-dimensional circular cylinder impulsively generated a vortex street. The operating free stream Reynolds and Mach number range was 3.25 × 104 ≤ Rn ≤ 2.03 × 105 and 0.193 ≤ M∞ ≤ 0.483, respectively. The formation of the initial standing pair of vortices, their shedding, and the subsequent establishment of the vortex street were recorded interferometrically using a high speed framing camera. The movement of the initial vortex pair was observed to be significantly altered for Rn > 1.5 × 105, where a secondary vortex pair was generated and merged with the initial vortex pair well before shedding commenced. During the lifetime of the impulsively generated wake, the Strouhal number, S, approached an average value of 0.16 which is significantly lower than the usual steady-state value of about S ≃ 0.2. Values of spacing ratio were found to decrease with increasing vortex street lifetime for all downstream locations. Other pertinent vortex street characteristics were also reported.
A New Method to Measure the Microresidual Stress-Field Around Inclusions
Authors: Gulbransen L. B. , Chatterjee S. K.
Published: November 2011

A brief review of various theories of interaction of inclusions and domain walls in a ferromagnetic material is presented. A postulate concerning the modification of domain patterns by inclusions, based on theory, is described and the various free-energy contributions of the inclusion to the matrix in the vicinity of the inclusion are discussed. Examples of domain wall bending in ingot iron by manganese sulfide inclusions are shown to agree with the postulated model of interaction of a stress field around the inclusion and the domain wall.
Determining the Dynamic Elastic Modulus at Elevated Temperatures by Using Rapid Heating Techniques
Authors: Austin A. L. , Parker R.
Published: November 2011

A unique method of determining the dynamic elastic modulus at elevated temperatures is reported. It consists of discharging a low-inductance capacitor bank through a preheated thin rod of the test material, which is clamped at one end and free at the other. The transient i2R heating during bank discharge takes place in a time interval short compared to the mechanical response time of the rod, inducing longitudinal oscillations. The periodic motion of the free end of the rod interrupts a collimated light beam directed over the rod and onto an SD-100 photodiode whose output is recorded on a 561A Tektronix oscilloscope. This gives a direct measure of the modulus since it is inversely proportional to the square of the period of oscillation. The theory, experimental apparatus, and method are discussed and sample data are given for tests made on type 304 stainless steel to illustrate the accuracy and usefulness of this technique. The data are compared with those of other investigators using other methods, and excellent agreement was obtained. This method is particularly useful for testing hazardous materials where remote operation is required for safety.
A New Approach to the Reduction of Pump Cavitation: The Hubless Inducer
Authors: Jekat W. K.
Published: November 2011

This paper describes a new and promising inducer which has no hub but a shroud. The design makes it possible to employ drastic vane sweepback. The shroud eliminates the vane clearance cavitation observed in the conventional screw inducer. Test data, cavitation photographs, and an analysis are presented. Maximum suction specific speed reached was 55,000 with 153 F water. Suction specific speed increases with speed and temperature up to a point. A special form of Reynolds number correlates the speed and temperature effect. The possible interrelation of boundary-layer transition and cavitation is discussed. Best suction specific speeds occur at positive incidence angles. The concept of incidence head is introduced and a theoretical equation is given.
Performance and Design of Straight, Two-Dimensional Diffusers
Authors: Reneau L. R. , Johnston J. P. , Kline S. J.
Published: November 2011

Performance data and flow characteristics for subsonic, two-dimensional, straight center line diffusers are presented. The four primary flow regimes which can occur are described and presented as functions of overall diffuser geometry. The performance of both stalled and unstalled diffusers is mapped for a wide range of geometries and inlet boundary layer thicknesses. An understanding of the relationships between flow regime and performance leads to a rational basis for diffuser design. The important maxima of performance and their location on the performance maps are presented. Both the range of data and correlations of optima of performance are extended beyond previous results.
Effects of Wall Shape on Flow Regimes and Performance in Straight, Two-Dimensional Diffusers
Authors: Carlson J. J. , Johnston J. P. , Sagi C. J.
Published: November 2011

Three diffuser sets (N/W1, held constant in each set) were built and tested for performance and flow regime over a range of total area ratios, AR, which yielded unstalled and stalled flows. At each AR and N/W1, a simple class of convex-inward (trumpet-shaped), straight, and convex-outward (bell-shaped) wall shapes were tested. It is concluded that there is little advantage to be gained by contouring the walls of two-dimensional diffusers. A corollary result shows that the performance prediction method of reference [1] gives good results for unstalled diffusers.
The Effect of Viscous Shear on Transients in Liquid Lines
Authors: Holmboe E. L. , Rouleau W. T.
Published: November 2011

Two separate experiments were performed and the results were compared with theory: (1) The propagation of a short, rectangular pulse of pressure in a cylindrical tube of previously undisturbed liquid and (2) the pressure surge resulting from a step change of flow in a pipe, commonly termed “water hammer.” By considering viscous shear to be frequency-dependent, good agreement between experiment and theory was found. The observation of a precursing phenomenon in a low viscosity liquid is also discussed.
Incompressible Jet Mixing in Converging-Diverging Axisymmetric Ducts
Authors: Hill P. G.
Published: November 2011

A test has been made of the constant turbulent Reynolds number hypothesis for a turbulent jet flow in a converging-diverging axisymmetric tube. Using the free turbulent jet as the sole source of data for evaluation of the Reynolds number, and velocity shear distributions, the general ducted flow was predicted with the aid of appropriate similarity relations. Calculated results are compared with the extensive and consistent data of Helmbold; good agreement is observed. It is found that the methods of calculation employed can be considerably simplified without large effect on the calculated results. The existence and extent of zones of recirculation are also discussed.
Dynamic Reversibility in Fluid Flows
Authors: Yajnik Kirit
Published: November 2011

This note points out the relatively simple character of dynamically reversible flows. A flow is said to be dynamically reversible if the reversed flow is possible under the action of suitable forces. The velocity field in the case of such flows of a Newtonian fluid subjected to conservative body forces can be decomposed into two parts, one satisfying Laplace’s equation and the other, the conduction equation. An integral similar to Bernoulli’s integral can also be found. In addition, the vorticity in two-dimensional flows is constant along a streamline. The property of dynamic reversibility is enjoyed by many flows such as irrotational flows, unidirectional flow through pipes, and two-dimensional axisymmetric vortexes.
Fracture Toughness of Structural Steels as a Function of the Rate Parameter T ln A/ε˙
Authors: Corten H. T. , Shoemaker A. K.
Published: November 2011

The influence of temperature and strain rate upon the fracture toughness of structural steel is the question considered in this paper. The hypothesis is proposed that fracture toughness, KIc, for initial crack extension is a single-valued function of the rate parameter T ln A/ε˙. Measurements made by Krafft and Sullivan of fracture toughness, KIc, for three steels covering a range of low temperatures and high strain rates are presented as a function of this rate parameter. Two of the materials support the contention that a single-valued relation exists between KIc and the parameter, while scatter in the data for the third steel does not allow a conclusion. The complexity of design against fracture in structural steels is reviewed. For conservative design it must be assumed that a crack is present in the structure. Design against fracture must insure that the minimum fracture toughness at the service temperature, strain rate and stress is sufficient to prevent this crack from extending rapidly through the base metal. A means of using low temperature laboratory fracture toughness tests for estimating a minimum fracture toughness corresponding to the service conditions is discussed.
Cavitation Damage Studies With Rotating Disk in Water
Authors: Wood G. M. , Knudsen L. K. , Hammitt F. G.
Published: November 2011

The cavitation damage resistance of alloys of aluminum, columbium (niobium), tantalum, molybdenum, and stainless steel was evaluated in water using a rotating disk apparatus that simulated the cavitation vortex patterns encountered in pumps operating at high suction specific speed. The alloys in decreasing order of cavitation resistance were Ta-8W-2Hf, Cb-18W-8Hf, Ta-10W, 316SS, Mo-.5Ti, Cb-1Zr, Al-4Cu-.7Mn-.5Mg, and Al-2.5Mg-.25Cr. The damage resistance order does not follow the variation of any single property such as strain energy to failure, yield strength, or hardness, but appears to be a combination of mechanical properties and phase structure. Photomicrographs show predominant intergranular cracking for the molybdenum alloy and transgranular erosion and cracking for the remaining alloys tested. The second phase precipitate in the aluminum alloy appears to hinder the erosion of material. Investigation of small variations in the grain size of the heat-treated Cb-1Zr alloys resulted in some variation in damage resistance, with the largest grain structure exhibiting the highest resistance. Correlation curves of volume loss as a function of the peripheral velocity are presented for all materials tested. In addition, the operation of the rotating disk apparatus itself was examined in considerable detail and the effects of various design changes were evaluated.
Linearization of Time-Independent Nonlinearities by Use of an Extra Signal and Extra Nonlinearity
Authors: Oldenburger R. , Ikebe Y.
Published: November 2011

The technique of signal stabilization is that of introducing an extra signal at the input to a nonlinearity to improve or otherwise alter its performance. In this paper this technique is extended to the introduction of both an extra signal and a nonlinear element to improve performance. Here a method is given for linearizing time-independent non-linearities in the sense of time averages by the introduction of a high frequency sawtooth wave and an ideal relay. The technique of pulse width modulation, employed in the communications field, is applied here. The method developed is applicable to feedback systems with a time-independent nonlinearity in the loop. The method is illustrated by applications to nonlinear systems with first and second-order lags. The concept of equivalent gain is used to simplify the mathematical approach so that the technique can be readily employed in engineering analysis and design. Good agreement is obtained between precise theory and approximations.
Optimal Control With Chebyshev Minimax Performance Index
Authors: Johnson C. D.
Published: November 2011

The optimal control of dynamical systems with conventional Mayer, Lagrange, and Bolza type performance indexes has been studied in some detail [1], [2], [3]. In the present paper, the optimal control of dynamical systems with a certain minimax type performance index, which cannot be expressed in the Mayer, Lagrange, or Bolza format, is studied. The form of the optimal control is described and certain geometric properties of the solution are discussed. Several examples are worked in detail to illustrate application of the proposed method of solution.
Quasi-Optimum Control of a Flexible Booster
Authors: Cohen V. , Friedland B.
Published: November 2011

The problem of minimizing both the in-flight bending moments as well as the terminal drift of a flexible vehicle is considered. The performance criterion V(T)=12y2(T)+k¯2∫tTM2(ξ)dξ, where y(T) is the drift, and M is the in-flight bending moment, is selected to achieve a compromise between excessive drift and excessive structural loading. The two-point boundary value problem for the design of the rigid-body control system is solved analytically for the linear, time-varying optimum control law. The flexibility of the vehicle is then accounted for, in a model consisting of two rigid sections hinged together with a torsional spring, by augmenting the rigid-body optimum control law with feedback terms proportional to the vehicle flexure and its rate. The results of a digital computer simulation indicate that the quasi-optimum control law obtained by this technique results in satisfactory performance, while the rigid-body control law is inadequate for a vehicle of moderate flexibility.
Distributed Parameter Optimum Control of a Nuclear Rocket With Thermal Stress Constraints
Authors: Briggs D. L. , Shen C. N.
Published: November 2011

The problem considered here is that of controlling the flow rate through a nuclear rocket such that temperature gradients in the fuel elements, and the corresponding thermal stresses produced, do not exceed specified values. The desired control program is that which takes the system from steady-state conditions at a given flow rate to a higher, specified flow rate in minimum time without violating the thermal stress constraints. The system equations here are a pair of coupled, first-order, bilinear, partial differential equations and the thermal stress constraint is proportional to a product of state and control variables. By analyzing both the solution for a step in control and the coupling between control level and time response in the bilinear system, the form of the optimal control is deduced. It is shown how the optimal control law can be generated using a digital computer. Numerical results are given.
Hydraulic System Simulation Using Time-Delay Elements
Authors: Blodgett R. E. , King R. E.
Published: November 2011

A method of simulating a class of hyperbolic distributed systems without using space discretization is presented. Complex distributed systems are realized by means of subsystems of basic distributed elements. The time-delay operation forms the basis of the technique which is ideally suited to hybrid or digital computation. Using this method the system is simulated independently of its boundary conditions which may be dynamic in nature. An example of a simple hydraulic system is presented.
Signal Stabilization of a Memory Type Nonlinearity
Authors: Mahalanabis A. K. , Oldenburger R.
Published: November 2011

The dual input describing function (DIDF) is derived here by statistical methods for the difficult case of a memory type nonlinearity. Special mathematical techniques are used to simplify the problem so that closed form solutions can be obtained. The DIDF is employed to determine the effect of an external sinusoidal signal on system limit cycles. The theoretical results are verified by tests on an analogue computer.
A Fluidic Temperature Control Using Frequency Modulation and Phase Discrimination
Authors: Kelley L. R.
Published: November 2011

Methods of using fluidic devices for sensing and controlling temperature were developed for gas turbine engine application. Frequency modulation and phase discrimination techniques were used both in the sensing of the temperature and in the comparison of the sensed temperature with the reference value. These techniques proved to be practical for measurement at a point and can be adapted for average temperature measurements. Temperature information was transmitted 5 ft by a pneumatic carrier frequency signal. Key fluidic circuitry was built and tested at temperatures ranging from 70 F to 2000 F. The temperature limitations were found to be those inherent in the material from which the devices were fabricated. No degradation of performance was noted at high temperatures.
Optimum Nonuniform Error Quantizers for Feedback Control Systems
Authors: Limbert D. E. , Taft C. K.
Published: November 2011

The effects of nonuniform error quantization on feedback control system stability from the viewpoint of the existence of limit cycles are discussed. The existence of limit cycle is investigated for both step and ramp inputs and results are compared to actual system simulation. Guidelines are given for the selection of a quantizer to allow maximum velocity for a given number of error quantization levels with no loss of position accuracy.
Optimum Control of Linear Systems With Transportation Lag
Authors: Khatri H. C.
Published: November 2011

A necessary condition for the optimum control of a linear system with input delay or transportation lag is derived in terms of the system weighting function. For a general quadratic integrand in an integral-type index of performance and a linear time invariant system with input delay, an expression for the optimum controller is given in the Laplace domain in terms of the system transfer function. This expression simplifies the calculation of the optimum controller. The results are applicable to systems with or without input delay. An example is given to illustrate the procedure.
A Unified Approach to the Analysis of Uniform One-Dimensional Distributed Systems
Authors: Brown F. T.
Published: November 2011

Proper selection and ordering of the variables of uniform, linear, one-dimensional distributed, dynamic models are shown to simplify their analysis, particularly when several simultaneous energy flows are coupled. Symmetric and asymmetric product variables are identified in pairs, leading toward criteria for system symmetry and reciprocity and formulas for the desired transmission matrices. Standard operational matrix techniques allow the identification of generalized wave-scattering variables, leading to decoupled equations. Application of the technique is demonstrated for simple systems, counterflow heal exchangers, the Bernoulli-Euler beam, and flexible fluid-carrying tubes.
A Comprehensive Creep Model
Authors: Harmathy T. Z.
Published: November 2011

Based on Dorn’s creep theory, a comprehensive creep model has been developed that is applicable to the calculation of deformation processes at steadily increasing temperatures and slowly varying load. It is shown that the entire course of the creep curve (excepting the tertiary creep) of structural (polycrystalline) materials is uniquely determined by two stress-dependent parameters, εt0 and Z. Explicit expressions for the description of creep processes are proposed. These expressions cannot strictly be regarded as equations of state, but yield an accuracy acceptable for engineering calculations even if dσ/dt ≠ 0.
Fracture Toughness of 7075-T6 and -T651 Sheet, Plate, and Multilayered Adhesive-Bonded Panels
Authors: Kaufman J. G.
Published: November 2011

Fracture-toughness tests have been made of 7075-T6 sheet and -T651 plate and of multi-layered panels of the sheet and plate. The nominal net fracture strength and the critical fracture-toughness parameters (Kc and Gc) of multilayered adhesive-bonded panels are greater than those of sheet or plate of the same total thickness, because the individual layers may fracture independently, each developing shear surfaces. The fracture strength and critical stress intensity factor, Kc, for a 0.5-in. thick panel made up of eight layers of 0.063-in. sheet are approximately twice those of 0.5-in. plate. Multilayered metallurgically bonded panels do not exhibit any advantage over sheet or plate of the same thickness, if the metallurgical bond retards shear-surface formation on the individual layers. The plane-strain stress-intensity factor, determined at pop-in on multi-layered adhesive-bonded or metallurgically bonded panels, is independent of thickness or number of layers.
An Ultrasonic Pressure Gage
Authors: Heydemann Peter L. M.
Published: November 2011

The transit time of short ultrasonic pulses in solid rods is used to measure pressures throughout the fluid range. Self-excited regenerating circuits are used. Measurements to 3500 bar with an uncertainty of 0.3 bar and to 20 kb with an uncertainty of 2 bar are reported. Further improvements, temperature compensation, and stability are discussed.
Forced and Periodic Vortex Breakdown
Authors: Sarpkaya Turgut
Published: November 2011

The results of an experimental study of the forced and periodic breakdown of a confined vortex rotating in the opposite direction are presented. The vortex tube consists of two chambers connected by a short conduit through streamlined transitions. The upstream end is closed by a plain wall, and a circular orifice is provided at the downstream end. The swirling flow and the breaker-vortex are generated by introducing varying proportions of air or water through tangential ports located near the upstream and downstream walls of the unit. The cases of single breakdown and periodic breakdown are explored and typical data are presented for each case. Finally, the pros and cons of the two existing transition theories are discussed.
A Performance Prediction Method for Unstalled, Two-Dimensional Diffusers
Authors: Reneau L. R. , Johnston J. P.
Published: November 2011

A method based on turbulent boundary layer integral theory is presented for the prediction of performance in two-dimensional, straight-center-line diffusers which contain, at most, small amounts of stall. The method is shown to adequately predict experimental pressure recovery data from diffusers with very thin to moderately thick inlet boundary layers. An approximate method for prediction of the onset of severe stall in two-dimensional diffusers is presented, but the general problem of boundary layer separation prediction is not solved.
Investigation of Cavitating Cascades
Authors: Wade R. B. , Acosta A. J.
Published: November 2011

Experiments on cavitating and noncavitating cascades were carried out in a conventional water tunnel modified for this purpose. The comparison of the experimental results with theory, in both the fully wetted and fully cavitating conditions, was found to be satisfactory.
The Design and Performance of Two-Dimensional, Curved Diffusers: Part I—Exposition of Method and Part II—Experiment, Evaluation of Method, and Conclusions
Authors: Sagi C. J. , Johnston J. P.
Published: November 2011

A procedure for the design of two-dimensional, curved diffusers is developed and evaluated through comparisons with flow regime and performance data. As input to the method, the inner and outer-wall potential-flow pressure distributions are specified as combinations of straight-wall diffuser pressure distributions. The diffuser shape is calculated using the method of Stanitz. In Part II criteria are established for choosing desirable inner and outer-wall pressure distributions. These criteria are based on systematic performance and flow regime tests carried out on curved diffusers with inner-wall length to throat width ratios between 4 and 10, area ratios between 1.5 and 2.1, and turning angles between 30 and 90 deg. The procedure yields diffusers of higher performance than circular-arc center-line diffusers.
Pressure Distribution and Bubble Formation Induced by Longitudinal Vibration of a Flexible Liquid-Filled Cylinder
Authors: Schoenhals R. J. , Overcamp T. J.
Published: November 2011

Analytical and experimental results are presented for a flexible liquid-filled cylinder subjected to forced longitudinal vibration. Analytical predictions are correlated with experimental measurements of pressure amplitudes and threshold acceleration levels required to produce bubble formation, as well as visual observations of the regions in which formations occur.
An Evaluation of the Hydrogen Bubble Technique for the Quantitative Determination of Fluid Velocities Within Clear Tubes
Authors: Davis W. , Fox R. W.
Published: November 2011

The hydrogen bubble technique for flow visualization is modified for quantitative determination of velocity of water flowing in clear plastic tubes. Calibration tests are reported showing the accuracy which may be expected of the technique. The technique is verified by application to the determination of the hydrodynamic entrance length in steady flow.
An Analysis of the Bauschinger Effect in Some Engineering Alloys
Authors: Wells C. H.
Published: November 2011

A simple relationship between the stress-strain curves during initial and reversed loading is shown to approximate closely the shape of hysteresis loops for several materials and test temperatures. This relationship is derived from the assumption of homogeneous total strain and a model of slip based upon reversible, long-range interactions of dislocations, which is equivalent to kinematic strain hardening on a microscopic scale. The alternative assumption of homogeneous stress predicts behavior not in agreement with experimental results.
The Laminar Boundary Layer on a Rotating Circular Arc Blade
Authors: Halleen R. M. , Johnston J. P. , Reynolds W. C.
Published: November 2011

The primary objective was to develop an exact solution to the simplest possible laminar boundary-layer problem for a curved rotating blade. It was formulated initially so that the results might be used to illuminate some of the characteristics of boundary-layer behavior on centrifugal impeller blades. The solution was obtained by a perturbation technique and the results compared to existing approximate solutions and related exact solutions. A primary result shows that rotation itself may induce laminar boundary-layer separation on a blade trailing face in the absence of free-stream, longitudinal adverse pressure gradients. This result is then interpreted to show that such a separation may become important for impellers of low ReD = uˆtD/ν; i.e., when ReD ≤ 900.
Effects of Cavitation on Periodic Wakes Behind Symmetric Wedges
Authors: Young J. O. , Holl J. William
Published: November 2011

Measurements of the shedding frequency and spacing of cavitating vortex street wakes have been made for four wedge models having apex angles of 15, 30, 60, and 90 deg. The wake pattern made visible by the presence of cavitation bubbles enabled measurements of the shedding frequency and vortex street spacing to be taken. It was found that the cavitation produced negligible effects on the shedding frequency with decreasing cavitation number down to as low as half the incipient cavitation number. Further decrease in the cavitation number produced an increase in the shedding frequency to a maximum value followed by a decrease with a general decay to random shedding. The analysis of high-speed motion pictures demonstrated a general decrease in the cross-stream spacing of the two rows of vortices with decreasing cavitation number. The longitudinal spacing of vortices in the same row also decreased with decreasing cavitation number followed by a rapid increase at cavitation numbers lower than that producing the peak frequency. In a simplified analysis, it was hypothesized that the cavitation in the vortex cores caused a general sink effect in the shed wake. Modeling the cavitation with cylindrical cavitation bubbles, some agreement with the experimental results was obtained for the cross-stream spacing with decreasing cavitation number.
The Effect of the Rotation of the Stress Axes on the Yield Criterion of Prestrained Materials
Authors: Hsu Tao-Ching
Published: November 2011

The yield locus of a prestrained material can be based on different systems of combined stress, such as biaxial tension and combined tension and shear. No matter what the combined stresses may be, however, the deviatoric yield stress is a function of only two variables, the characteristic index, which represents the stress ratio, and the stress direction, or the inclination of the principal stress axes. It is shown that, when tubular specimens are tested under combined torsion and axial tension, the results show the mixed effects of the characteristic index and the stress direction on the yield stress. In such tests, the two effects can, however, be separated if the strain vectors as well as the yield stresses are known. The theory is applied to several groups of experimental results on the yield locus of prestrained materials, including Taylor and Quinney’s results.
Gain Characteristics of Subsonic Pressure-Controlled, Proportional, Fluid-Jet Amplifiers
Authors: Simson A. K.
Published: November 2011

The gain characteristics of a subsonic, pressure-controlled, proportional, fluid-jet amplifier are developed in relation to the control-port and receiver-design parameters. The analysis uses an assumed submerged-jet representation. Control ports are added and the control flows associated with various control-port positions are calculated. The control-port characteristics are presented in a series of design curves. The receiver characteristics are obtained also as a function of their inlet geometry. Optimum dimensions are found to maximize gain for pressure, flow, and power amplifiers. Linearity is discussed. The receiver characteristics are presented in a series of design curves. Complete amplifier characteristics are obtained by combining the control-port and receiver characteristics. An example calculation is shown.
Optimal Control of Some Class of Imperfectly Known Control Systems
Authors: Aoki Masanao
Published: November 2011

The paper discusses optimal controls of processes with unknown constant parameters, where the processes are such that no measurements on the parameters are available during control periods. The general formulation of this optimal control problem is given for such systems, and it is shown that the formulation becomes quite simple when the equation for the observed-state vector is invertible, and that the problems of estimation and optimal controls cannot be separated for the class of problems discussed in the paper even when the systems are linear with quadratic criterion functions.
Fluid Center-Line-Velocity Effect on Fluid-Temperature Transients in a Heat Exchanger
Authors: Thal-Larsen H. , Loscutoff W. V.
Published: November 2011

Inlet and outlet temperature fluctuations of the fluid passing through the inner tube of a concentric-tube counterflow heat exchanger are related by a temperature transfer function. This function is affected by the velocity distribution of the stream, a distribution which is usually in the shape of a paraboloid. Such a distribution has a center-line velocity that is higher than the bulk velocity. The center-line velocity is responsible for longitudinal temperature diffusion effects which cannot be ignored. Slug flow at bulk velocity, a convenient assumption made by many authors, does not account for the shape of experimental fluid-temperature transients discussed in this paper. Rather, the center-line velocity and the bulk velocity, both convenient quantities, are recommended as effective aids in the successful prediction of temperature transients.
Drift Compensation of Linear Systems by Parameter Adjustments
Authors: Rissanen J.
Published: November 2011

For a class of linear systems the conditions are given under which drift compensation is possible by adjustments of the control parameters. In such a case the system is called “completely adaptable.” The equations for the adjusting mechanism are derived by use of a functional derivative technique, admitting a remarkably simple implementation. Finally, the stability conditions for the total system are given.
Stability-Boundary Approximations for Relay-Control Systems Via a Steepest-Ascent Construction of Lyapunov Functions
Authors: Weissenberger S.
Published: November 2011

This paper presents a new technique for constructing Lyapunov functions for estimating the domain of asymptotic stability of nonlinear control systems. A machine program assigns figures of merit (based on the quality of the stability-boundary estimates) to the members of a set of Lyapunov functions and then searches for the one which maximizes this measure. The method is applied to relay-control systems, which are not tractable by other systematic techniques such as the method of Zubov. The paper is divided into two parts. The first part contains a discussion of the motions of relay-control systems and the technique of investigating their stability domains with Lyapunov functions. The second part contains a discussion of existing methods of generating Lyapunov functions and a description of the new method, along with a number of second and third-order examples.
Design and Analysis of Commercial Pressure Vessels to 500,000 Psi
Authors: Berman I.
Published: November 2011

On the basis of the finiteness of the flow strength of structural materials, the pressures permitted by current methods of pressure vessel design are limited. In this paper the analysis of a new method of design of commercial large volume pressure vessels is presented. This new design, which is a controlled fluid fill, may be used for many excursions to very high pressures without failure. The pressure that may be attained seems limited only by material property changes at extreme hydrostatic pressures. Large volume commercial vessels to 500,000 psi with reasonable outer to inner diameters may be built. The controlled fluid-fill pressure vessels in addition to piercing the current upper pressure barrier is also competitive with the shrink-fit method at pressures as low as 15,000 psi.
Some Mechanical Properties of Uranium-10 Weight Percent Molybdenum Alloy Under Dynamic Tension Loads
Authors: Hoge K. G.
Published: November 2011

Dynamic tensile tests were conducted on uranium-10 weight percent molybdenum alloy in as-cast and wrought conditions. Carbon content was varied from 71 to 800 ppm. Heat-treatment was also varied. Tests were conducted on a universal testing machine at strain rates of 4.8 × 10−5 and 0.057 in/in/sec and on a modified Dynapak at strain rates up to 100 in/in sec. Tests were run from 75 to 600 F. Relatively low strain rates were used to determine the susceptibility to stress corrosion while the higher strain rates demonstrated the sensitivity of various mechanical properties to strain rate effects.
Temperature and Scale Effects Upon Cavitation and Flashing in Free and Submerged Jets
Authors: Lienhard J. H. , Stephenson J. M.
Published: November 2011

Observations of inception and desinent cavitation numbers in small submerged jets, and observations of the flashing of small, highly superheated, free jets, are presented. The observations, made over a range of jet sizes and water temperatures, reveal a strong influence of geometric scale in both systems. The water temperature has little effect upon the cavitation number for the submerged jet except at high temperatures. Flashing occurs in the free jet after a delay time which is shown to vary as the (−7/2) power of the liquid superheat, and inversely as the jet area.
Strain-Cycle Fatigue of 70-30 Copper Nickel
Authors: Gibbons W. G.
Published: November 2011

Three sets of strain-cycled fatigue tests have been conducted at three laboratories on wrought 70-30 Cu-Ni. The data reported herein provide an unnotched fatigue-failure curve of this material suitable for design purposes.
Microstructural Alterations of Rolling—Bearing Steel Undergoing Cyclic Stressing
Authors: Martin J. A. , Borgese S. F. , Eberhardt A. D.
Published: November 2011

After prolonged cyclic stressing in rolling contact, AISI 52100 bearing steel parts develop extensive regions of microstructural alteration, designated as white etching areas. These are oriented in predictable directions relative to the rolling track. Lenticular carbides are always associated with these areas. Evidence is presented indicating that the boundaries of lenticular carbides constitute planes of weakness which may be preferred planes of fatigue cracking. In the transmission electron microscope the martensitic structure appears gradually transformed into a cell like structure by the action of cyclic stress. The size of crystallites is greatly reduced in this process. The density of microstructural change is found increased with cycling and is distributed in depth along a curve resembling that of the calculated maximum unidirectional shear stress with little or no visible change in the region of maximum orthogonal (alternating) shear stress.