bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic Nondestructive Measurement of Irradiation Damage in Steel
Authors: Hunter D. O.
Published: November 2011

Measurements of changes in ultrasonic velocities and critical angle method signal amplitude have been made on reactor irradiated A302-B, A542-B, and 304 steels. Results show a strong sensitivity to neutron fluence and irradiation temperature. Changes at lower irradiation temperatures appear correlative to some irradiation degraded changes in mechanical properties.
Yielding and Flow Characteristics of Low-Carbon Steel Between Ambient and Liquid Nitrogen Temperatures
Authors: Goodenow R. H. , Bucher J. H.
Published: November 2011

The yielding behavior and flow characteristics of a low-carbon rimmed steel and a titanium-stabilized steel were examined between ambient and liquid nitrogen temperatures. The initial grain size and carbide morphology were varied by suitable thermal-mechanical treatments, while temper rolling was used to prestrain representative samples. Yielding at room temperature occurred heterogeneously in the annealed rimmed steel, and homogeneously in the titanium steel. With tensile testing at low temperatures, plastic instability upon yielding was observed in both steels. The plastic instability transition temperature, TPI, was analyzed in terms of the quantities σi and ky in the Hall-Petch relationship, σy2 = σi + kyd−1/2, and the influence of interstitial content and temper reduction on σi and ky are discussed. In the annealed condition TPI for the titanium steel was found to be approximately 100 F lower than for the rimmed steel. However, a strong grain size dependency was observed for both steels, i.e., only moderate to fine grained specimens exhibited a TPI. Temper rolling raised TPI for the titanium steel with all reductions, while for the rimmed steel TPI was lowered initially for temper reductions up to approximately 0.75 percent. Electron microscopic examination did not reveal any correlation between TPI and deformation structure.
Forced and Self-Excited Oscillations in Propellant Lines
Authors: Zielke W. , Wylie E. B. , Keller R. B.
Published: November 2011

Analytical techniques used to model the dynamics of propellant feed systems of rocket engines are presented as well as experimental results which provide verification. The laboratory hydraulic system, consisting of suction pipe, centrifugal pump, and discharge pipe, provides longitudinal fluid oscillations which are analyzed by use of linear methods employing a distributed parameter representation of the pipes. Of particular interest is the effect of the pump upon pressure oscillations when the pump is operating under cavitating conditions. A self-excited instability caused by the interaction between hydraulic and structural portions of the system is also described.
Aerodynamic Drag on Vehicles in Tunnels
Authors: Gouse S. William , Noyes B. S. , Nwude J. K. , Swarden M. C.
Published: November 2011

The purpose of this study was to investigate the aerodynamic drag on vehicles moving in guideways of varying degrees of enclosure. The reason for this study was that several potential high speed ground transport system concepts involve high speed motion of vehicles in enclosed guideways for significant portions of their travel time. Analytical and experimental investigations have been carried out. The analytical studies developed the solution for the aerodynamic drag on a vehicle in an enclosed guideway in laminar flow. The analysis is based on an analogy between the governing equations for the unsteady flow resulting when an infinite body is started impulsively from rest and the steady flow that results from steady motion of a semi-infinite body. The results of this analysis for laminar flow provided a base from which to begin in turbulent flow and were used to justify the basing of a drag coefficient on the wetted surface area of a vehicle rather than the frontal area of a vehicle. Preliminary experiments were executed using spheres as vehicle models. Final experimental studies were carried out using cylindrical models in circular tunnels of various lengths and various degrees of wall porosity. A drop testing apparatus was employed and results were obtained for Reynolds number of the order of 5 · 105. Results to date indicate that for vehicle length-diameter ratios of the order of 15 and above, with tunnel to vehicle diameter ratios of 1.5 and greater, a drag coefficient based on the wetted surface area of the vehicle is independent of the vehicle length-diameter ratio for incompressible flow. Results also indicate that, for incompressible flow, employing a tunnel model with a closed end simulates a tunnel length-diameter ratio of infinity. Tunnel wall porosity, assuming relatively unobstructed motion of fluid outside the porous wall, has a marked effect on decreasing the aerodynamic drag on vehicles moving in enclosed guideways and that for the range of variables investigated (clearance ratio as low as 1.4) tunnel wall porosity of 20 per cent is adequate for all the significant drag reduction that is possible. Qualitative predictions of loss coefficient analytical modeling and literature on transonic flow wind tunnel testing with porous walls are in agreement with the data presented.
Linear Dynamic Modeling of Flowing Fluid Lines
Authors: Orner P. A.
Published: November 2011

An “exact” classical solution is presented for the linearized frequency domain characterization of a barotropic fluid in a rigid circular tube. The axial velocity profile (and thus, the phase velocity, attenuation, and impedance) is represented by a confluent hypergeometric function with complex arguments. The confluent hypergeometric function has not been tabulated for general complex arguments, precluding numerical evaluation of the “exact” model. An approximate solution in terms of Bessel functions is derived, and numerically evaluated. The two-port asymmetric model for a uniform circular line with through-flow is derived and compared to known symmetric models (zero through flow). The significance of the linearized energy equation in the through-flowing case is discussed.
Crack-Propagation Rate in 7075-T6 Plates Under Cyclic Tensile and Transverse Shear Loadings
Authors: Iida Soushiro , Kobayashi A. S.
Published: November 2011

Crack-propagation rate in 7075-T6 tension plates was determined for central cracks initially oriented in 45, 60, and 90 deg, to the width direction of the tension plates which were loaded cyclically. Opening and sliding mode of stress-intensity factors, K1 and K2, were determined by the method of direct stiffness for curved cracks generated from these initially slanted cracks. Crack-propagation rates, Δa/ΔN, were then plotted against the maximum opening mode of stress-intensity factor, K1, in the presence of sliding mode of stress-intensity factor, K2. Comparison between the corresponding crack-propagation rate in control specimens without K2 showed that the propagation rate is definitely increased in the presence of K2.
In-Process Control of Residual Stress in Drawn Tubing
Authors: Misra S. K. , Polakowski N. H.
Published: November 2011

Experimental work directed toward the development of means for in-process control of residual stress during tube drawing is described. Experiments were done on 304 and 321 stainless steels, Incoloy 800, and copper tubing. While classical tube reducing processes, such as mandrel and plug drawing and sinking were the main objective, limited data on the effects of reeling and rock-rolling were also included. The distribution of residual axial and hoop stresses across the wall was determined by a Sachs’ analysis. Tandem drawing, wherein a small reduction (∼2 percent) was taken in the second die, produced a drastic reduction of the residual stress levels. A tapered bearing exit-die was specially efficient in this respect. However, the method was inefficient in pure sinking which always left residual stresses of high magnitude.
Aluminum Wire by Cold Hydrostatic Extrusion
Authors: Hettwer P. F. , Uy J. C. , McCann D. R.
Published: November 2011

Electrical grade aluminum wire was made by hydrostatic extrusion. Extrusion ratios ranged from 2.5:1 to 630:1. The surface finishes, diametric variations, and electrical and mechanical properties were found to compare favorably with aluminum wire drawn through conventional dies at lower composite reductions. Several process variables, including the effects of an external draw stress, die angle, and land length of die, were also investigated. The extrusion pressures and yield strengths of the extruded wires were theoretically calculated, using Pugh’s analysis for the total work done and the total strain in hydrostatic extrusion. These values were compared with the experimental results.
Vorticity Transfer and Production in Steady Inviscid Flow
Authors: Horlock J. H.
Published: November 2011

General equations are derived for the rate of change of vorticity in compressible, inviscid flow into which fluid may be introduced, and in which nonuniform body forces may exist. Examples of vorticity transfer and change are given and analogies are drawn between these examples.
Modeling and Compensation of Nonlinear Systems Using Sensitivity Analysis
Authors: Thompson J. G. , Kohr R. H.
Published: November 2011

In this paper sensitivity analysis techniques are applied to two aspects of the nonlinear system design problem: The modeling of nonlinear systems and the compensation of nonlinear systems. In the modeling problem the free parameters of the model are selected to minimize an integral performance index where the integrand is a function of the response of the model and the response of the modeled system. Sensitivity functions, which indicate the sensitivity of the response of the model to changes in the free parameters are used in the minimization procedure. Similarly, in the compensation problem, the adjustable parameters of the compensated system are selected to minimize an integral performance index where the integrand is a function of the response of the compensated system and a desired response. Sensitivity functions, which indicate the sensitivity of the response of the compensated system to changes in the adjustable parameters, are again used in the minimization procedure. The sensitivity functions are obtained from multiple solutions of the general sensitivity equation subjected to various forcing functions. The general sensitivity equation is obtained by differentiation of the model equation or of the compensated system equation. The free or the adjustable parameters are determined as functions of some characteristic parameter which represents the magnitude of the input, the degree of the nonlinearity or some other performance characteristic of the system. All the required computations may be performed by a digital computer. Three nonlinear examples are given to illustrate the method.
Distributed System Simulation With Bilateral Delay-Line Models
Authors: Auslander D. M.
Published: November 2011

Consideration of general linear models for transmission line systems (hydraulic, pneumatic, electrical, etc.) has so far been limited to the case of systems in which the lines exhibit no internal dispersion. In this paper, a simulation system for distributed dynamic systems which can include dispersive transmission elements will be described. The ideal transmission line, a lossless, nondispersive transmission line, is used with static junctions to form models of dynamic systems. A simple computational algorithm is obtained if the state of the model is expressed in terms of wave-scattering variables rather than by the pressure-flow or voltage-current type of state variables. A model for dispersive transmission lines is presented, and its feasibility is demonstrated.
New Liapunov Function for Nonlinear Time-Varying Systems
Authors: Newman A. K.
Published: November 2011

A new method of generating Liapunov functions is described that is useful for time-varying nonlinear differential equations. Constant coefficient quadratic forms are often used as Liapunov functions for linear constant coefficient differential equations. However, if the differential equation coefficients are time-varying and nonlinear, better results are usually obtained by using variable quadratic forms as Liapunov functions. This variation in V often introduces undesirable terms in V˙, which are cancelled by modifying V by subtracting integrals of certain partial derivatives of V with respect to the dependent variables. With few restrictions, V is proved to remain positive definite after the modification. The method often directly extends a Liapunov function useful for constant coefficient differential equations to cover the case when the coefficients are time-varying and nonlinear. Two examples are presented, including the incremental circuit for a time-varying nonlinear transmission line with hysteresis and the equations for an N-body collision avoidance problem.
The Turbulent Wake of a Body of Revolution
Authors: Chevray R.
Published: November 2011

The wake behind a six-to-one spheroid was studied for a Reynolds number equal to 2.75 × 106 at 12 sections from 0.25 dia upstream to 18 dia downstream from the stern of the body. The flow pattern was determined and an analytical expression was derived to express the manner in which the mean characteristics of the wake develop in the established flow region. The Reynolds stresses were measured throughout the flow and their magnitudes were checked through the momentum and mean-energy equations.
Development of a Periodic Flow in a Rigid Tube
Authors: Florio P. J. , Mueller W. K.
Published: November 2011

The development of a pulsating velocity field in a rigid, circular tube was experimentally investigated. The wall pressure and the radial variation of the axial velocity were measured at several axial locations. The measured inlet velocities were compared with the fully developed velocities. The experimental results show that, for the range of parameters investigated, the developing pulsating flow can be considered to be simply a superposition of a developing mean flow and a fully developed oscillating flow. These results are in agreement with a previous approximate analytical solution by Atabek and Chang.
Effect of State-of-Stress and Yield Criterion on the Bauschinger Effect
Authors: Rolfe S. T. , Haak R. P. , Gross J. H.
Published: November 2011

During fabrication, the cold forming of structural components may reduce the yield strength of a component if it is loaded in a direction opposite to that of the cold forming. This reduction in yield strength, referred to as the Bauschinger effect, is influenced by the state-of-stress under which the cold forming is performed, by the criterion used to determine the yield strength, and by the use of post-forming stress relief. To establish the importance and magnitude of these effects, specimens from 2 1/2-in-thick plates of HY-80 steel, cold-formed by plane strain bending, were tested along with specimens that were cold-formed by plane-stress axial straining. For material tested in a direction opposite to that of cold forming, the Bauschinger effect was observed both in tension and compression, whereas for material tested at 90 deg to the direction of cold forming in plane strain, both the tensile and compressive yield strengths increased and no Bauschinger effect was observed. Because of the difference in restraint, the Bauschinger effect was greater for plane-stress axial deformation than for plane-strain bending deformation. The Bauschinger effect was greater when the yield strength was determined at small offsets and was essentially eliminated at an offset greater than 0.5 percent. In addition, the Bauschinger effect was greatest for small amounts of cold deformation and was progressively decreased by strain hardening at large amounts of cold deformation. The reduction in secant modulus and in yield strength (Bauschinger effect) in cold-formed material was essentially eliminated by stress-relief treatment at 1025 deg. F. The results indicate the importance of knowing the cold-forming state-of-stress, the criterion used in determining yield strength, and the effects of stress relief when assessing the effects of cold deformation on mechanical properties.
A Study of Incompressible Turbulent Boundary Layers in Channel Flow
Authors: Clark J. A.
Published: November 2011

The fully developed incompressible turbulent boundary layer in a channel has been explored using constant-temperature hot-wire anemometry. Particular attention was paid to measurements well into the viscous sublayer, yielding results which are believed to be new. Frequency spectral analyses of the fluctuating velocity components have been obtained for the inner layers. The mean velocity distribution in the sublayer has been determined with sufficient accuracy for a reasonable estimate of skin friction to be made. The results are compared with those of Laufer [11] and Comte-Bellot [4].
A Study of the Response of Coupled Liquid Flow-Structural Systems Subjected to Periodic Disturbances
Authors: Wood Don J.
Published: November 2011

The dynamic response of liquid flow systems may be grossly affected by motion of the system’s structural supports. Pressure and flow perturbations within the flow system provide the driving forces for the structural supports, and the resulting motion induces further pressure and flow perturbations. In this type of closed-loop system, instabilities are possible. Analysis techniques are developed which enable the analyst to formulate distributed parameter, nonlinear solutions to unsteady flow problems including structural motion. These techniques are based on plane wave theory and require the use of a digital computer. For sinusoidal periodic inputs of small amplitudes, closed-form mathematical solutions are possible if nonlinearities are linearized, and these solutions are carried out. Examples show that resonance points and peak-to-peak pressure amplitudes may be very sensitive to structural properties of the supporting structure. Analytical results obtained with the closed-form linearized model and the nonlinear digital model are compared. It is also shown that the closed-form linearized model gives results which compare favorably with the nonlinear model for the case of sinusoidal inputs, but cannot be applied if the input perturbations are nonsinusoidal or are sufficiently large or if wave shapes are to be computed. Experimental results are shown to agree well with theoretical calculations.
Some Correlations of Theory and Experiment for Developing Turbulent Free Shear Layers
Authors: Lamb J. P. , Bass R. L.
Published: November 2011

This paper presents an extensive review of some recent experimental results for developing turbulent free shear layers in isoenergetic flow with free stream Mach numbers up to eight. Experimental longitudinal variations of a midprofile velocity and a characteristic layer width are compared with corresponding predictions from a recent theory for developing layers and from the well-known asymptotic theory. Using a recent theoretical specification for the variation of spread rate parameter σ with free stream Mach number, it was found that the predictions of the developing layer analysis were in general agreement with measurements. It was demonstrated that the asymptotic theory, in conjunction with the virtual origin technique, can also be utilized to predict developing layer growth. An experimental specification of σ yielded uncertainties ranging from 15 to 50 percent, although the results tended to confirm the general validity of some recent theoretical postulations for the spread rate parameter.
Short-Time Elevated Temperature Mechanical Properties of 2219-T87 and 2219-T6 Aluminum Alloy
Authors: Montano J. W.
Published: November 2011

The mechanical properties of 2219-T87 and 2219-T6 aluminum were determined after soak times from 0 to 300 sec at temperatures from 300 deg F (149 deg C) to 600 deg F (316 deg C). Specimens were tested also at ambient temperatures after a soaking period of 300 sec at temperatures of 200 deg F (93 deg C) to 700 deg F (371 deg C). In general, the tensile strength of the 2219 aluminum alloy decreased with increasing temperature. The tensile properties were not significantly influenced by variations in the soak times used through 500 deg F (260 deg C). At 600 deg F (316 deg C), increasing the soak time affected the strength slightly. For relatively short time exposures, this material can be recommended for load-bearing applications to 400 deg F (204 deg C), at which temperature 70 percent of the ambient temperature strength is still retained. When tested at ambient temperature after exposure to 400 deg F (204 deg C) for 300 sec, 2219-T87 retained approximately 97 percent of its original ambient temperature strength.
Stress Intensity Factors for Hollow Circumferentially Notched Round Bars
Authors: Harris D. O.
Published: November 2011

Stress intensity factors are presented for a hollow circumferentially notched round bar subjected to tension, torsion, bending, and transverse shear. These previously undetermined factors are calculated from the limiting values of stress concentration factors for a small notch root radius. The stress intensity factors obtained are compared with results obtained by other investigators, when possible, and a favorable correlation is observed. The accuracy is further indicated by the good agreement of the fracture toughness of 7075-T6 aluminum, determined in a series of tension and bending tests conducted on hollow notched round bars, with the corresponding value obtained by other investigators.
On the Relative Validity of Two Current Cold-Rolling Theories
Authors: Le May Iain , Nair K. D.
Published: November 2011

The paper compares the established cold-rolling theory of Ford, et al., with the more recent shear-plane theory. Recent experimental results obtained by the authors are used in the comparison and it is shown that, although the shear-plane theory is inherently more correct as it does not assume homogeneous compression of the strip, the effect of the usual assumption of a yield stress independent of deformation rate virtually negates any advantage in its use at present.
Stability Analysis of Reactor Systems Via Lyapunov’s Second Method
Authors: Hsu C.
Published: November 2011

This paper develops a technique for finding Lyapunov functions for the class of nonlinear partial differential equations arising from a reactor system which takes into account the coupling of heat transfer, hydrodynamics, and time-dependent neutron diffusion. As a first step, a generalized Lyapunov function was developed for the linearized reactor system. The result provides the sufficient conditions to system stability (and/or asymptotical stability) with respect to the distributed system parameters. A new Lyapunov function for the nonlinear reactor system was constructed by adding nonlinear terms to that of the linear system. The result enables one to determine the region of stability and indicates the proper feedback function which would insure the global stability of the system.
The Frequency Response of Pneumatic Lines
Authors: Karam J. T. , Franke M. E.
Published: November 2011

The amplitude frequency response (transfer gain curve) of 0.170-in-ID blocked pneumatic lines of the type used in fluidic systems was experimentally determined. Several lengths (20 ft and less) of tubing at several mean pressures (10 to 40 psig) were studied over the frequency range of 1-1000 cps. The electric-pneumatic analogy was used to develop theoretical predictions of the gain curves. Correlation with experiment showed that a frequency-dependent resistance and a frequency-dependent conductance were required in the analogy when the signal frequency was somewhat greater than a characteristic frequency of the line. A high-frequency model, based on the work of Nichols, was developed; it predicted the resonant gains within 2 db and the resonant frequencies within 10 percent.
Feedback Control of Linear Distributed Systems
Authors: Wiberg Donald M.
Published: November 2011

The optimum feedback control of controllable linear distributed stationary systems is discussed. A linear closed-loop system is assured by restricting the criterion to be the integral of quadratics in the state and control. Feedback is obtained by expansion of the linear closed-loop equation in terms of uncoupled modes. By incorporating symbolic functions into the formulation, one can treat boundary condition control and point observable systems that are null-delta controllable.
A Format Method for Generating Liapunov Functions
Authors: Peczkowski J. L. , Liu R. W.
Published: November 2011

A method is developed for generating Liapunov functions, V, which have the property that, along the trajectories of a system under consideration, the scalar functions V˙ or (V˙ − Vt) take on a preassigned or desired form. The method applies to both autonomous and nonautonomous systems and complements and extends other known methods and techniques for generating Liapunov functions. The method is called a format method since it is based upon a fundamental vector-matrix equation or format, v = [D + P]f, which mathematically represents every vector v which satisfies the scalar product v·f = (V˙ − Vt). The method is readily applied to very general classes of systems as well as to special and particular systems. The format method is illustrated by generating Liapunov functions for autonomous and nonautonomous systems. Three examples are given. An explicit expression for V and V˙ for second-order systems is given in terms of the components of a system x˙ = f and any, arbitrary real function p(x; t). A Liapunov function is generated for a more general class of third-order systems than any which has been given heretofore. Also, it is shown how the basic vector format may be applied to inverse Liapunov problems.
Numerical Analysis of Crack Propagation in Cyclic-Loaded Structures
Authors: Forman R. G. , Kearney V. E. , Engle R. M.
Published: November 2011

An improved theory is proposed for the crack-growth analysis of cyclic-loaded structures. The theory assumes that the crack tip stress-intensity-factor range, ΔK, is the controlling variable for analyzing crack-extension rates. The new theory, however, takes into account the load ratio, R, and the instability when the stress-intensity factor approaches the fracture toughness of the material, Kc. Excellent correlation is found between the theory and extensive experimental data. A computer program has been developed using the new theory to analyze the crack propagation and time to failure for cyclic-loaded structures.
The Influence of Nitrogen and Certain Other Elements on the Creep-Rupture Properties of Wholly Austenitic Type 304 Steel
Authors: Goodell P. D. , Cullen T. M. , Freeman J. W.
Published: November 2011

Experimental heats of Type 304 steel, compositionally balanced to be wholly austenitic and thus simulate the material used to produce seamless superheater tubing, were prepared to determine the influence of selected elements on the creep-rupture properties of this steel and thereby assess their possible contribution to the improvement in the elevated temperature properties which has been noted over the past years. Nitrogen is shown to increase the rupture strength at 1200 deg F of the wholly austenitic laboratory heats to a pronounced extent. Furthermore, almost the full effect of nitrogen was obtained after heat-treating at temperatures as low as 1750 deg F. Rupture strengths also increased with increasing carbon content although heat-treatment above 1750 deg F was necessary to obtain the maximum strengthening effect from the higher levels of this element. Nitrogen was a somewhat more effective strengthener than carbon, the rupture strengths correlating with (%C) + 1.25 × (%N). Small amounts of titanium, aluminum, boron, copper, and molybdenum had no or at most only minor effects on the properties. More than 0.1 percent manganese was necessary for good rupture properties but otherwise had little effect at levels up to at least 1.5 percent. Published data for commercial heats fitted the correlation developed from the laboratory heats. The generally higher level of the rupture strength data for Type 304 austenitic steel published since the early 1950’s appears to be closely related to higher levels of nitrogen. The data indicate that it is extremely important to control nitrogen content to obtain expected creep-rupture properties at 1200 deg F.
A Plastic Stress Analysis of Cylindrical Wafers Under Elastically Deformable Compression Plates
Authors: Davis R. L. , Jackson J. W.
Published: November 2011

This paper represents an analysis of the pressure distribution occurring in axially loaded cylindrical wafers with, and without, elastic radial constraints. The purpose of this report is to demonstrate the resulting stress patterns that occur in short compression specimens frequently used in determining material properties, and in the opposed-anvil, or Bridgman-type, high-pressure cells. The influence of radial constraints, material strain hardening, wafer diameter-to-height ratio, anvil or plate deflection, and the wafer-anvil interface friction on the resulting stress distributions have been examined. The integrated normal stress distribution across the specimen surface has been verified experimentally via numerous tests in which each of the subject parameters listed above was varied.
Turbulent Boundary Layers in Diffusers Exhibiting Partial Stall
Authors: Moses H. L. , Chappell J. R.
Published: November 2011

An investigation of turbulent boundary-layer separation in internal flow is presented, with experimental results for a variable angle, two-dimensional diffuser. A simple analytical model is adopted, which consists of wall boundary layers and a one-dimensional, inviscid core. By calculating the pressure simultaneously with the boundary-layer development, the approximate method is extended to include the separated region. With a limited amount of separated flow, the calculated pressure recovery agrees reasonably well with the experiments and gives a fair indication of maximum diffusion performance. The limitation of the model, as well as the possibility of singularities and downstream instability, are discussed in relation to the general problem of boundary-layer separation.
Poiseuille Flow With Variable Fluid Properties
Authors: Kettleborough C. F.
Published: November 2011

Flow of a fluid through a parallel channel is one of the simplest types of flow. However, the equations of flow and energy are far from simple and can only be solved in a closed form in the simplest cases when nonlinear effects such as the inertia and convective terms can be neglected (i.e., for zero Reynolds number) and when the energy and momentum equations are uncoupled. A numerical iterative method is described in which the coupled momentum and energy equations are solved when the viscosity, thermal conductivity and specific heat are functions of temperature, and the density a function of temperature and pressure; inertia terms are retained in the momentum equation and the convective terms, compression work term and the predominant dissipation term retained in the energy equation. Results are obtained for a variety of boundary temperatures up to about 2400 deg F and the effect of variable fluid properties and various terms in the energy and momentum equation are shown.
Theory of a Thin-Ring Airfoil in an Incompressible Inviscid Source Flow Field
Authors: Yang Tah-Teh
Published: November 2011

This analysis concerns itself with the loading calculation of a thin-ring airfoil symmetrically positioned in an unbounded spherical source flow field. A spherical source was used to replace the undisturbed, nonparallel, but axisymmetric, freestream. A ring vortex distribution was used to replace the thin-ring airfoil. The thin-airfoil theory not only limits the shape of the airfoil, but also applies only for a small angle σ, between the chord line and the relevant undisturbed source flow rays. With the latter restriction, the distance between the source origin and the midchord of the airfoil, roa of Fig. 2, is considered to be longer than the chord ca and the terms of 01roa/ca2 and higher-order terms were neglected in the analysis. The result of the analysis is a set of algebraic equations containing geometric parameters of the flow field. For a given geometry the strength of the ring vortex distribution can be calculated readily.
An Extension of the Woods Theory for Unsteady Cavity Flows
Authors: Kelly H. R.
Published: November 2011

One of the most useful theories for the design of hydrofoils for use in cavitating flow has been that of L. C. Woods. He solved the linearized problem for a two-dimensional hydrofoil in Helmholtz flow, at zero angle of attack, and tabulated the results. His theory is here extended to include nonzero cavitation number and nonzero angle of attack. The results are tabulated and some are compared with the original Woods theory.
Column Separation Accompanying Liquid Transients in Pipes
Authors: Baltzer R. A.
Published: November 2011

Column separation is described and investigated in terms of the governing fluid dynamics. The partial differential equations of continuity and momentum, including nonlinear friction losses, are used to mathematically represent the transient movement of liquids in pipes under conditions of both full-pipe and free-surface flows. The complete systems of equations are programmed for numerical simulation of the column-separation phenomenon using a digital computer and the method of characteristics. Theoretical time-pressure information derived from mathematical simulation is compared with the corresponding experimental information obtained from laboratory investigation. Despite higher-than-anticipated energy losses in the prototype flow, the general comparison of the two sets of information is favorable.
On Real Fluid Flow Over Yawed Circular Cylinders
Authors: Chiu W. S. , Lienhard J. H.
Published: November 2011

The equations for both the boundary layer and the outer potential flow over a yawed cylinder can be resolved into equations for the crosswise and spanwise velocity components. These components of the boundary layer are evaluated using Sears’ method, and the separation point is found to be uninfluenced by the yaw angle. The potential-flow solutions for the spanwise and crosswise flows are added together to determine vortex patterns behind the cylinder. The approximate direct dependence of the Strouhal number upon the cosine of the yaw angle and/or the drag coefficient upon the square of the cosine, are verified. Experimental determinations of the Strouhal number and visualization of the flow pattern are consistent with the analysis.
Dynamic Strain Aging of a High Strength Steel
Authors: Goel V. , Busch R. , Zackay V. F.
Published: November 2011

The response of quenched and tempered, and ausform H-11 steel to strain aging was investigated. The straining temperature was the most important variable. Straining at elevated (up to 900 deg F) temperatures and retempering resulted in large increases (approximately 30 percent) in yield strength without the loss in ductility associated with static strain aging. The yield to ultimate strength ratio approached unity in the strain-aged steels, however, elongations of 8–12 percent were retained.
The Wall Effect in Cavity Flow
Authors: Ai D. K.
Published: November 2011

A nonlinear theory for the calculation of the flow field of an oblique flat plate under blockage condition is given using the techniques of integral equations. Numerical results are obtained with the aid of a high-speed digital computer for the plate situated midchannel at values of the angle of attack from 10 to 90 deg and the channel width-chord ratio from 3 to 20. Although the theory is developed for arbitrary plate location, the midchannel case is of great interest due to the fact that most of the tests are performed at this position.
A Radial Diffuser Using Incompressible Flow Between Narrowly Spaced Disks
Authors: Moller P. S.
Published: November 2011

Owing to the geometric limitations of certain internal flow systems, the use of a conical or rectangular diffuser for the recovery of kinetic energy as static pressure is often impossible. This paper describes a study of swirl-free, incompressible flow in a radial diffuser consisting of two components: A radial channel in which the flow diffusion occurs and an inlet bend which joins the radial channel to the supply pipe outlet. A design for an efficient inlet bend is described and a study made of other geometrical parameters. The experiments showed that the pressure recovery decreased with increasing inlet boundary-layer thickness and decreasing Reynolds number, both for the radial diffuser and a 7-deg conical diffuser of the same area ratio. In addition, the pressure recovery of the radial diffuser was comparable to that of the 7-deg conical diffuser at the high Reynolds numbers generally encountered in internal flow systems. At high Reynolds numbers, it was also possible to predict theoretically the pressure recovery for the radial diffuser.
A Theory of Lubrication by Microirregularities
Authors: Hamilton D. B. , Walowit J. A. , Allen C. M.
Published: November 2011

This paper describes a theory of liquid lubrication applicable to parallel surfaces, such as the surfaces of a rotary-shaft face seal. The lubrication mechanism presented is based on surface microirregularities and associated film cavities. Closed-form analytical solutions are obtained giving load capacity as a function of speed, viscosity, and surface-asperity dimensions. The theoretical results agree qualitatively with load capacity determined experimentally for three asperity distributions.
External Friction and Relationship Between Adhesion and Deformation Components
Authors: Kraghelsky I. V. , Mikhin N. M.
Published: November 2011

This paper deals with the friction coefficient for a plastic contact with due regard to the volume deformation of the plastic material and adhesion at the contact. Equations are derived which express the relation of friction coefficient with mechanical and geometrical characteristics as well as external factors. The value of penetration at which the adhesion and plowing components remain similar is found by qualitative analysis. The commonly known relation between load and friction coefficients is restated. The theoretical results are compared with the experimental ones which have been reported both in the USSR and other countries. This comparison shows little or no disparity.
Theory and Experiments of Squeeze-Film Gas Bearings: Part 1—Cylindrical Journal Bearing
Authors: Pan C. H. T. , Malanoski S. B. , Broussard P. H. , Burch J. L.
Published: November 2011

An asymptotic analysis for the cylindrical squeeze-film gas journal bearing has been formulated. An approximate analytical solution is presented. Load-deflection experiments have been performed on a double-film, squeeze-film gas journal bearing. The experimental data confirm the theoretical predictions. Design curves are given for the steady-state radial load capacity and radial stiffness of the cylindrical gas journal bearing.
An Experimental Study of the Response of a Small Porous Chamber to Forced Oscillations
Authors: Martinez E. , Peskin R. L.
Published: November 2011

An experimental program was undertaken to evaluate the theoretical relation between pressure phase angle and frequency for forced oscillations of a small porous chamber. The data were found to be in agreement with the predictions of the theory.
Cavitation Tests in Pipe Bends
Authors: Kamiyama S.
Published: November 2011

A series of experiments on the square-section bends was performed for determining the effects of the following shape differences of the surface-pressure distributions on cavitation inception. (a) Difference of the lengths of minimum pressure region; (b) difference of the pressure gradients. The effects of those differences were clarified. Also, in these bends, the appearances of the increase of head loss and limiting flow condition due to the cavitation occurrence were clarified.
Quadrant-Edge Orifice and Performance at Very High Reynolds Numbers
Authors: Ramamoorthy M. V. , Seetharamiah K.
Published: November 2011

This paper presents the results of an experimental investigation on the discharge coefficient of a quadrant-edge orifice meter at high Reynolds numbers (in the range of 20,000 to 600,000). Results show that the coefficient of discharge can be related qualitatively with the drag of a cylinder in an infinite fluid medium. Results regarding upper constancy limit and reproducibility are also furnished.
Analysis of Pneumatic Controllers
Authors: Hind E. C. , Dollar W.
Published: November 2011

The concept of hydraulic capacitance is applied to pneumatic bellows assemblies. This concept is then used in the analysis of a number of different basic types of pneumatic controllers in common use. Its application allows the effect of the bellows system used for delaying the derivative action, and the effect of bellows movement generally, to be conveniently included in the analyses. Numerical values determined for a particular controller show that the effect of bellows movement can change the transfer function constants by as much as 20 percent.
A Paper and Pencil Control System Design
Authors: Gustafson R. D.
Published: November 2011

This paper describes an algebraic method of control system design using the system characteristic equation and the Routh array. This technique does not require finding roots of the characteristic equation and therefore is suitable for pencil and paper analysis. In addition, since no graphical steps are required, large system trade-off studies can be easily programmed for digital computer optimization. The method is based on the idea of validating a simple response approximation formed by truncating the characteristic equation. This validation is performed by placing a constraint on the ratio between the integrated square of the system impulse response and the corresponding integral of the approximation. The values of these integrals are obtained quite easily from the Routh array. Additional ratios and a generalized damping ratio are also defined. The design of a hydraulic control system is presented as an example problem illustrating the use of this method.
The Design of Nonlinear Multivariable Control Systems From State Dependent Linear Models
Authors: Fertik H. A. , Schoeffler J. D.
Published: November 2011

A technique is presented for the design of a continuous nonlinear multivariable control algorithm from a set of simple, linear control models. The coefficients of the linear control models are dependent on the steady state operating point. The technique makes use of line integration and the method of least squares to bridge the gap between the sets of linear coefficients and the continuous nonlinear functions of the nonlinear algorithm. In general, the nonlinear control algorithm is nonunique. The method permits the extension of linear design procedures to the design of nonlinear control systems. It can be used to design a control system for a nonlinear process to maintain the dynamics of the entire system invariant with respect to changes in the operating point.
On the Global Stability of a Class of Nonlinear Time-Varying Systems
Authors: Puri N. N.
Published: November 2011

In this paper the problem of the stability of motion of the equilibrium solution x1 = x2… = xn = 0 is studied, in the sense of Lyapunov, for a class of systems represented by a system of differential equations dxi/dt = Fi (x1, x2…xn, t), i = 1, 2…n or x˙ = A (x,t)x. Various x1 are known as state variables and Fi (0, 0…0, ∞) = 0. The various elements of square matrix A (x, t) are functions of time as well as functions of state variables x. Two different methods for generating Lyapunov functions are developed. In the first method the differential equation is multiplied by various state variables and integrated by parts to generate a proper Lyapunov function and a number of matrices α, α1…αn, S1, S2…Sn. The second method assumes a quadratic Lyapunov function V = [x′S(x,t)x], x′ being the transpose of x. The elements of S(x,t) may be functions of time and the state variables or constants. The time derivative V˙ is given by V˙ = x′[B′A + S˙]x = x′T(t,x)x where B x gives the gradient ∇V, and S˙ is defined as ∂S/∂t. For the equilibrium solution x1 = x2… = xn = 0 to be stable it is required that V˙ should be negative definite or negative semidefinite and V should be positive definite. These considerations determine the sufficient conditions of stability.
Identification of Systems Described by Partial Differential Equations
Authors: Perdreauville F. J. , Goodson R. E.
Published: November 2011

A method is given for the identification of distributed parameter systems. Normal operating records or experimental data may be used. The method involves the determination of arbitrary parameters in an assumed partial differential-equation model of the system. The method applies equally well to linear and nonlinear equations, and equations with varying coefficients. The accuracy of the results depends upon the exactness of the model, the amount of data used, the error in numerical integration, and the amount of noise which is present in the data. Examples are given which illustrate the application of the method. Results using the method for the identification of a physical system are given.
The Bauschinger Effect in a High-Strength Steel
Authors: Milligan R. V. , Koo W. H. , Davidson T. E.
Published: November 2011

The object of this work was to evaluate quantitatively the Bauschinger effect in a 4330 modified steel as a function of strength level and structure as derived from variations in heat-treatment. Material having martensitic, pearlitic, and bainitic structures was studied utilizing a uniaxial tension-compression specimen. Various ways of defining the magnitude of the Bauschinger effect are explained. One is a conventional approach as suggested by Welter, the other a technique which takes strain-hardening into account. The results show the Bauschinger effect to be independent of yield strength for three different strength levels of the martensitic material. It is only mildly influenced by material structure and independent of the direction of overstrain. The Bauschinger effect increases with increasing permanent strain up to approximately 2 percent and thereafter remains essentially constant.
Hot-Gas Actuators: Some Limits on the Response Speed
Authors: Vaughan D. R.
Published: November 2011

A third-order model of a hot-gas position actuation system is studied in this paper. The model is assumed linear except for gas-flow saturation which is shown to place certain limits on step-response speed. First, the limitations of a linear controller are established; next, the same limits are shown to apply to a bistable control scheme utilizing a linear combination of stale variables as a switching criterion. Finally, the step-response time required by a system utilizing time-optimal control is established. The results indicate that significant improvements in response time can be achieved through the use of intentionally nonlinear feedback compensation.
Creep and Rupture Behavior of Low Alloy Steels in High Pressure Hydrogen Environment
Authors: Coombs J. W. , Allen R. E. , Vitovec F. H.
Published: November 2011

The creep and rupture properties of steels were investigated at 1000 deg F in an environment of argon at 50 psig pressure and hydrogen at 900 psig pressure. An SAE 1020 steel, a 0.5 percent Mo-steel, and a 1 percent Cr-0.5 percent Mo steel were used as test materials. The strength of the steels was lower and the creep rate higher in hydrogen than in argon. The data are discussed in respect to the effect of stress on the rate of hydrogen attack.