bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments on Pulse Propagation in an Obliquely Laminated Composite
Authors: Sve C. , Okubo S.
Published: November 2010

Experimental results are presented for the linear elastic dynamic response of periodically laminated composites. A shock tube-capacitive transducer technique is used to determine the rear surface velocity history of three laminated samples that have different lamination angles and are subjected to a step pressure loading. Viscosity effects are discussed, and comparisons are made with predictions based on previous theoretical work.
Pulse Propagation in Inhomogeneous Media
Authors: Longcope D. B. , Steele C. R.
Published: November 2010

Approximate solutions are developed for one-dimensional pulse propagation in a medium with an analytic wave speed when the ratio ε of the pulse length to a characteristic length of the wave speed variation is small. The solutions describe an 0(1) transmitted pulse, given by the WKB solution, and an 0(ε) reflection which may progress in the opposite direction. Two approximations for the reflection are given, one in terms of explicit integrals and the other, which may be uniformly valid, by a combination of explicit integrals and a slowly varying numerical term. Comparisons with the exact solution in several examples show the usefulness of the approximate solutions.
Displacement Thickness Effects on Inviscid Flow Past Cones
Authors: Ghia U. , Davis R. T. , Mikhail A. G.
Published: November 2010

The second-order inviscid flow past axisymmetric cones has been determined. The Legendre functions (of fractional degree) and their derivatives appearing in the solution have been accurately evaluated. This solution is used to determine the displacement thickness corrections to the boundary layer on the cone. It is found that this correction is not zero for the cone of general included angle, but vanishes as the cone approaches a vanishingly thin needle.
A Method for Quantifying Creep Strain Due to Cyclic Stress
Authors: Williams J. J. , Leckie F. A.
Published: November 2010

A method is proposed for isolating the two constants required to quantify the creep strains caused by cyclic histories of stress. These constants can be determined from the results of a single cyclic creep test together with data from constant stress tests.
Sensitivity Analysis of the Added Mass Computation for a Rod Vibrating in a Fluid-Filled Cavity
Authors: Krajcinovic D.
Published: November 2010

This paper considers influence of small geometrical imperfections, such as out-of-roundedness and eccentricity, on the magnitude of the added (apparent, virtual) mass for a rod vibrating in acoustic fluid contained within a rigid cavity. Using the perturbation of boundary conditions method derived are simple formulas allowing qualitative and quantitative analyses for several types of imperfections.
Turbulent Sediment Transport Over a Flat Bottom Using Momentum Balance
Authors: Drew D. A.
Published: November 2010

The turbulent flow of a sediment-fluid mixture over a flat bottom is studied using momentum balance. The in-the-small forces included are gravity, buoyancy, and a linear drag. A turbulent average is applied and mixing length theory is used for the resulting Reynolds stresses. Assuming small concentrations and small still water settling velocity, the resulting velocity profile is logarithmic; the sediment concentration profile is relatively constant near the bottom, and drops off rapidly above a certain level predicted by the theory. Numerical and asymptotic results are discussed.
Two-Dimensional Jet Mixing With a Pressure Gradient
Authors: Brink D. F. , Chow W. L.
Published: November 2010

An analytical study of nonsimilar jet mixing is made for compressible, nonisoenergetic flows. The conservation equations are solved for each of the streams above and below the dividing streamline by using Meksyn’s asymptotic method of integration for solving boundary-layer problems. The problem of laminar mixing between two parallel streams is investigated for the case of a constant pressure gradient. It is found that the velocity and temperature profiles from the exact solution to the nonsimilar governing equations can be well approximated by the locally similar solution.
The Dynamics of Javelin Throw
Authors: Soong Tsai-Chen
Published: November 2010

Wolferman of West Germany won the 1972 World Olympic javelin throw with a throw of 296 ft 10 in. (90.47m). Lusis of the USSR came in second with a throw of 1 in. (2.5cm) less. Had he paid a little more attention to technical details, he could have won. In the present paper, five nonlinear, dynamic differential equations which describe a javelin in flight, the wind effect included, are derived, and a numerical solution is proposed. A case study shows that 3.31m (10.9 ft) could be added to the 1972 record by using a throw angle and initial javelin axis angle of 42 and 35 deg, respectively, instead of the conventional angles of 35 deg. Slightly modifying the contour of the javelin profile, legitimate within current NCAA rules, to move the center of the pressure drag forward to 0.8cm behind its center of gravity, instead of the present 25.7cm, gives an additional gain in range of 16.13m (52.9 ft).
Brain Tissue Fragility–A Finite Strain Analysis by a Hybrid Finite-Element Method
Authors: Atluri S. N. , Kobayashi A. S. , Cheng J. S.
Published: November 2010

This paper deals with the finite-strain, finite-element analysis of the states of stress and strain in the vicinity of a blunt indenter applied to the exposed surface of the pia-arachnoid of an anesthetized rhesus monkey.
Thermoelasticity of Anisotropic Generally Laminated Slabs Subject to Spatially Periodic Thermal Loads
Authors: Padovan J.
Published: November 2010

Based on 3-D thermoelasticity theory, the effects of mechanical and thermal material anisotropy on the local stationary fields of generally laminated plates are investigated. In particular, to model the stated problem, each individual lamina of the slab is considered to be composed of mechanically and thermally possibly fully anisotropic materials whose fields satisfy 3-D elasticity and conduction theory. Using complex series expansions, together with the properties of complex adjoint differential forms, a 3-D solution of the given model is obtained. Its generality is such that plates consisting of any number of distinct fully anisotropic lamina subject to arbitrary spatially periodic external and internal mechanical and thermal loads can be handled. In terms of the model and its solution, the results of several numerical experiments which emphasize the effects of material anisotropy on the governing fields of symmetric, alternating, and shingle-type laminates are reported.
Forced Transient Motion of a Rigid Body Bonded to a Deformable Continuum
Authors: Chilton P. D. , Achenbach J. D.
Published: November 2010

The dynamic response of a rigid mass supported by a deformable continuum is investigated, for the case that the mass is subjected to a load of arbitrary time-dependence. The motion of the mass generates waves in the supporting continuum. The accompanying radiation of energy provides a damping mechanism for the motion of the mass. In this paper two-dimensional problems are investigated for which the wave motion in the supporting continuum is governed by a single wave equation. Two examples to which the results apply are (a) normal motions of a rigid line element which is supported by a stretched membrane, and (b) antiplane motions of a rigid strip which is bonded to an elastic half space. The traction between the rigid body and the supporting continuum is determined in subsequent intervals of time, and the velocity and displacement of the mass are computed. Numerical results are presented for the case that the applied load is a step function with time.
An Elastic Half Plane Weakened by a Rectangular Trench
Authors: Keer L. M. , Chantaramungkorn K.
Published: November 2010

The problem of an elastic half plane loaded in tension and weakened by a rectangular trench is set up in a manner leading to a system of simultaneous singular integral equations. The method is to consider the superposition of solutions for two cracks perpendicular and one parallel to the surface of the half plane. The limiting case when the three cracks intersect appropriately leads to the geometry of a rectangular trench. A collocation scheme developed by Erdogan and Gupta leads to numerical solution of the equations to determine the stress intensity factors at the corners and the horizontal displacement of the trench wall.
The Three-Dimensional Hollow or Solid Truncated Cone Under Axisymmetric Torsionless End Loading
Authors: Klemm J. L. , Fernandes R.
Published: November 2010

The Saint-Venant problems of solid or hollow truncated cone are investigated under axisymmetric torsionless end loading with the ruled sides being free from stress. Total-stress problems are formulated in terms of a vector partial differential equation whose component variables are stresses or of stress-type. A biorthogonality condition is derived which permits the numerical solution of boundary-value problems, and the results of a sample application of the method are presented.
Unsteady Hydromagnetic Boundary Layer in a Rotating Medium
Authors: Puri P. , Kulshrestha P. K.
Published: November 2010

The three-dimensional flow of a viscous fluid in the presence of the transverse magnetic field past an infinite porous plate moving with a time-dependent velocity in a rotating medium is investigated. An exact solution is found by using the Laplace transform method. The order of Stokes, Ekman, and Stokes-Rayleigh layers arising in the problem are derived and the influence of the magnetic field and suction (blowing) is studied. The behavior of the drag and lateral stress on the plate is discussed and the power input required to keep the plate in motion calculated. It is also found that a normal solution exists at the resonant frequency for the problem investigated here.
Multiple Diffractions of Elastic Waves by a Rigid Rectangular Foundation: Plane-Strain Model
Authors: Dravinski M. , Thau S. A.
Published: November 2010

A rigid rectangular foundation embedded in an elastic half space moves in a direction perpendicular to the surface of the half space, Fig. 1. The model under consideration is of the plane-strain type. By application of the Laplace, Fourier, and Kontorovich-Lebedev (K-L) transforms, the equation of motion for the foundation is derived. The transient response of the foundation is exact during the period of time required for a longitudinal wave to traverse the base of the foundation twice. Thus the process of multiple diffractions at the corners of the foundation is taken into account.
Dynamic Stability of Isotropic or Composite-Material Cylindrical Shells Containing Swirling Fluid Flow
Authors: Chen T. L. C. , Bert C. W.
Published: November 2010

A linear stability analysis is presented for a thin-walled, circular cylindrical shell of orthotropic material conveying a swirling flow. Shell motion is modeled by using the dynamic orthotropic version of the Sanders shell theory and fluid forces are described by inviscid, incompressible flow theory. The critical flow velocities are determined for piping made of composite and isotropic materials conveying swirling water. Fluid rotation strongly degrades the stability of the shell/fluid system, i.e. increasing the fluid rotating speed severely decreases the critical flow velocity.
Stability of Poiseuille Flow in Elastic Tubes
Authors: Midvidy W. , Rouleau W. T.
Published: November 2010

This paper presents a theoretical analysis of the temporal and spatial stability of Poiseuille flow in elastic tubes to infinitesimal axisymmetric disturbances. A cylindrical shell model which includes the effects of transverse shear and rotatory inertia is employed for the tube wall. The characteristic equation of the system is solved numerically and two sets of modes are obtained; one set has eigenvalues that are independent of the properties and dimensions of the tube wall, while the other set has eigenvalues that depend on the tube parameters. One mode of the “tube-dependent” set is shown to have a critical Reynolds number that depends on the elastic properties and dimensions of the tube and either wave number or frequency of the disturbance.
Analysis of Combined Pressure-Shear Waves in an Elastic/Viscoplastic Material
Authors: Abou-Sayed A. S. , Clifton R. J.
Published: November 2010

A numerical solution is presented for the case of symmetric impact of two skewed plates, modeled to represent 6061-T6 Aluminum. The main features of the solution are, except near the impact face, the same as in previous solutions based on a rate-independent theory. Free-surface velocity-time profiles are obtained for the target rear surface. These profiles indicate that the fine structure of the normal velocity should be resolvable by means of a laser velocity-interferometer.
Elastic Interface Waves Involving Separation
Authors: Comninou Maria , Dundurs J.
Published: November 2010

A bonded interface between two solids which have an appropriate mismatch in their mechanical properties can support Stoneley waves. The question investigated is whether an unbonded interface, which is unable to transmit tensile tractions, can sustain interface waves that involve localized separation. The answer is affirmative, and the following conclusions are reached: 1. The solids must be pressed together. 2. All combinations of materials can sustain interface waves involving separation. 3. The phase velocity of the interface waves is not fixed but lies within a range of values. For instance, in case of identical materials, the phase velocity may have any value falling between the velocities of Rayleigh and transverse waves (cR < c < cT). 4. The interface waves do not involve a free amplitude, and the wave form is fixed. However, the length of the separation zones remains arbitrary, so that energy can still be transmitted at greatly different rates. 5. The solids move apart in the sense of an average displacement. 6. The gaps are symmetric about the centers of the separation zones, and the interface tractions are symmetric about the centers of the contact zones. 7. The interface waves involving separation exhibit features that are similar to those encountered in dynamic fracture. The interface tractions are square-root singular at both leading and trailing ends of the gaps. The two solids pull apart at the leading ends of the gaps with infinite discontinuities in particle velocities. The solids slam together at the trailing ends with exactly the opposite velocity discontinuities.
The Transient Motion of a Cylindrical Shell of Arbitrary Cross Section in an Acoustic Medium
Authors: Berger B. S. , Palmer M. E.
Published: November 2010

A solution has been constructed for the transient motion of a viscoelastic cylindrical shell of the arbitrary cross section, surrounded by a fluid medium. The fluid region external to the shell is mapped into the interior of a rectangle. The transformed fluid equation together with the shell equations are expressed in finite-difference form and the time variable suppressed through the application of the Laplace transform. Shell displacements and acoustic pressures are found over the fluid field and at the fluid solid interface.
Longitudinal Waves in Fiber-Reinforced Composite at Low and High Frequency Ranges
Authors: Yew C. H. , Jogi P. N.
Published: November 2010

A method for studying the behavior of transient longitudinal waves in fiber-reinforced composites, both in high and low frequency ranges, is presented. The results agree well with the solutions obtained by means of the transform method. The dispersive effect of waves to the interpretation of experimental results is also demonstrated by comparing the results obtained from the ultrasonic pulse technique.
Small-Amplitude Wave Behavior in One-Dimensional Granular Solids
Authors: Nunziato J. W. , Walsh E. K.
Published: November 2010

In this paper we consider the dynamic behavior of granular solids in the context of a one-dimensional, linearized theory. Uniqueness of solutions for unbounded domains is established and two wave propagation problems are solved. In particular, the dispersion relations for small-amplitude sinusoidal progressive waves are obtained and the evolution of small-amplitude shock waves is exhibited.
Stresses in Nonhomogeneous Cylindrically Anisotropic Elastic Cylinder
Authors: Roy Subhas Chandra
Published: November 2010

The object of this Note is to determine the radial displacement and relevant stresses in a cylinder (plane strain) on the basis of three-dimensional linear theory of elasticity. The material of the structure is orthotropic with cylindrical anisotropy and, in addition, is continuously inhomogeneous with mechanical properties varying along the radius.
Stress-Intensity Factors for Arbitrarily Oriented Cracks in Shallow Shells
Authors: Simmonds J. G. , Bradley M. R. , Nicholson J. W.
Published: November 2010

The equations describing the stress and strain fields in an elastically isotropic shallow shell containing a crack are reduced, via Fourier transforms, to four coupled singular integral equations plus side conditions. A perturbation solution, useful for relatively short cracks, is constructed for a pressurized shell of revolution containing a stress-free crack that makes an arbitrary angle with a line of curvature of the midsurface. First-order corrections due to curvature and crack orientation of the mode I (opening) and mode II (shearing) stress-intensity factors for a plate are computed analytically.
Reflection of Acceleration Waves in an Elastic-Plastic Medium
Authors: Cizek J. C. , Ting T. C. T.
Published: November 2010

The reflected waves generated when an acceleration wave advancing into a quiescent region reaches the boundary of a prestressed elastic-plastic solid are determined. Depending on the nature of the incident wave, there may be one to four reflected waves generated. It is shown that one of eight reflected wave patterns is produced provided that the critical incident angle is not exceeded. When this angle is exceeded, a solution may still exist. However, the two reflected waves are then both associated with slow wave speeds rather than one with a fast wave speed and the other with a slow wave speed. Numerical examples are provided.
Effect of Stress-Free Edges in Plane Shear of a Rectangular Orthotropic Region
Authors: Nair S.
Published: November 2010

The plane elastic problem of a rectangular orthotropic region is considered; subject to the boundary conditions of prescribed equal and opposite tangential displacements and zero normal displacements on the upper and lower edges and zero stresses on the remaining edges. The effect of the stress-free edges on the stiffness coefficient relating the tangential displacement and the corresponding shearing force is estimated in the form of upper and lower bounds for this coefficient.
Elastic Dispersion, Homogeneous Dispersive Media and an Application to Periodic Elastic Media
Authors: Balanis G. N.
Published: November 2010

Wave dispersion that occurs without energy loss is examined and media capable of supporting waves with such dispersion are developed. The media are homogeneous and dispersive. The dispersion of the waves they generate shares many of the characteristics of the dispersion of waves propagating through inhomogeneities. Thus these media can be useful in modeling the propagation of waves in inhomogeneous media. An example supporting the utility of modeling applications is presented.
Nonlinear Wrinkling of Nonlinear Membranes of Revolution
Authors: Wu C.-H.
Published: November 2010

The general problem of nonlinear wrinkling of nonlinear membranes of revolution is considered. The theory is applicable to membranes made of any nonlinear material although only Mooney material is considered in this paper. A smooth psuedo deformed surface is introduced to give a gross representation of the true deformed surface, and a kinematic quantity called wrinkle strain is introduced to measure the wrinklyness of the surface. The wrinkly regions are determined by the usual assumption that a thin membrane cannot take any compressive stress. A stretching problem is solved as an example.
Determination of Admissible Temperature Increases to Prevent Vertical Track Buckling
Authors: Kerr A. D. , El-Aini Y. M.
Published: November 2010

An analysis is presented for the determination of the range of “safe” temperature increases in a railroad track, in order to prevent vertical buckling. A general nonlinear formulation of the problem is derived by using the theory of elasticity, the principle of virtual displacements and the variational calculus for variable matching points. In order to simplify the solution it is shown, on a closely related problem, that a number of highly nonlinear terms may be neglected without affecting the final results. The obtained nonlinear formulation for the railroad track is simplified accordingly. The resulting nonlinear equations are then solved, in closed form, and the obtained results are presented graphically.
Axisymmetric Banding of Annular Plates
Authors: Tielking J. T.
Published: November 2010

The potential energy formulation of von Karman plate theory and the Ritz method are utilized to obtain solutions for deformation and stress in a variable thickness annular plate with built-in edges. The plate is loaded by prescribing an axisymmetric offset of the edges; the external axial force is calculated by Castigliano’s theorem. Solutions are presented to illustrate the influence of the plate thickness profile on the surface stress distribution and to show the effect of large deflections on the surface and membrane stress distributions in a plate with hyperbolic taper. The computational procedure is competitive with other procedures, such as the finite-element method.
A Realistic Solution of the Symmetric Top Problem
Authors: Kane T. R. , Levinson D. A.
Published: November 2010

This paper contains the development of an algorithm for the solution of any initial value problem dealing with the motion of a symmetric top on a horizontal surface. No restrictions are made regarding the roughness of the surface, so that both rolling and sliding resisted by friction are accommodated. A computer program incorporating the algorithm is used to settle several issues long in dispute concerning classical top motions.
Clamped Beam Parametric Amplifer
Authors: Eisinger K. , Merchant H. C.
Published: November 2010

Parametric amplification of the transverse motion of a uniform, clamped beam with a center mass is investigated. The system inputs are a transverse harmonic motion and a compressive load (with harmonic and static components) applied at the beam supports. Secondary parametric amplification is considered by the application of end-loads at frequencies near the system characteristic frequency and transverse support motions at frequencies much lower than the characteristic frequency. An example of an inertial sensing element for a gravimeter is presented.
Laminar Fluid Flow Measurements Employing a White Light Fringe Image Velocimeter (WFIV)
Authors: Chan J. H. C. , Ballik E. A.
Published: November 2010

A compact white light fringe image velocimeter (WFIV) is used to measure laminar flow. It is demonstrated, by comparison with similar measurements employing a differential laser Doppler velocimeter (DLDV), that the WFIV is a practical and important technique for determining flow velocities.
Dynamic Analysis of Incompressible Viscous Liquids
Authors: Johnson G. R.
Published: November 2010

A Lagrangian finite-element analysis technique is presented for two-dimensional plane strain problems involving time-dependent incompressible flow of viscous liquids. The incompressibility feature is obtained with an iterative procedure which adjusts the nodal velocities until the anticipated volumetric strains are within specified limits. By eliminating the compressibility, it is possible to determine the integration time increment from the rate of distortion, rather than the sound speed transit time, as is required with various numerical methods involving wave propagation in compressible materials. This paper includes the formulation of the numerical method and illustrative examples.
The Effect of Substantial Pretwist on the Stiffness Properties of Thin Beams of Cambered Section
Authors: Downs B.
Published: November 2010

A theoretical analysis is made of the changes in torsional and bending stiffnesses of beams, of asymmetric section, caused by pretwist. Results are presented for a limited range of elliptical sections possessing camber. Significant reduction in minimum bending stiffness is predicted for cambered sections.
Postbuckling Analysis of Continuous, Elastic Systems Under Multiple Loads—Part 1: Theory
Authors: Plaut R. H.
Published: November 2010

The stability of continuous, elastic systems subjected to multiple independent loads is considered. The analysis includes nonconservative loads as well as conservative loads, provided that instability is of the static, type. Systems exhibiting prebuckling deformations are included. A multiple-parameter perturbation technique is applied to the nonlinear equilibrium equation in the neighborhood of a critical point, and the postbuckling behavior and imperfection-sensitivity of the system are investigated. Critical points are classified as “general” or “special”, in analogy with Huseyin’s definitions for finite-degree-of-freedom, conservative systems. The results can be applied to study the interaction effects of the independent loads on stability. The theory is given in the present paper, while applications to columns and arches will be presented in the sequel.
Wide-Band Random Axisymmetric Vibration of Cylindrical Shells
Authors: Elishakoff I. , van Zanten A. Th. , Crandall S. H.
Published: November 2010

Analytical and numerical results are reported for the random vibrations of a uniform circular cylindrical shell excited by a ring load which is uniform around the circumference and random in time. The time history of loading is taken to be a stationary wide-band random process. The shell response is essentially one-dimensional but differs qualitatively and quantitatively from the response distributions for point-excited uniform strings and beams because of the large modal overlaps at the low end of the spectrum of shell natural frequencies. The contributions from the modal cross-correlations (which can usually be neglected for strings and beams) introduce an asymmetry into the distribution of mean-square response and can alter the magnitude of the local response considerably. For example, in a thin shell with a radius-to-length ratio of 0.5 the contribution to the mean-square velocity at the driven section due to the modal cross-correlations can be more than three times that due to the modal autocorrelations when the excitation is a band-limited white noise which includes 81 modes.
A Simplified Stability Criterion for Nonconservative Systems
Authors: Fawzy I.
Published: November 2010

Dynamic stability of a general nonconservative system of n degrees of freedom is investigated. A sufficient and necessary condition for the stability of such a system is developed. It represents a simplified criterion based on the famous Lyapunov’s theorem which is proved afresh using λ-matrix methods only. When this criterion is adopted, it reduces the number of equations in Lyapunov’s method to less than half. A systematic procedure is then suggested for the stability investigation and its use is illustrated through a numerical example at the end of the paper.
Stability of Shock Waves of Arbitrary Strength With Viscosity and Heat Conduction
Authors: Morduchow M. , Valentino J. V.
Published: November 2010

The problem of the stability of shock waves with viscosity and heat conduction has been previously formulated as an eigenvalue problem involving a set of linear ordinary differential equations in a finite domain with what are shown to be regular singular points at the ends of the domain. By means of a computer-aided Frobenius type of analysis, it is shown that the (continuous) eigenvalue spectrum is such that the shock waves will be stable for all values of the shock-strength parameter. Some actual solutions of the disturbance equations are shown.
Small Reynolds Number Electro-Hydrodynamic Flow Around Drops and the Resulting Deformation
Authors: Stewart M. B. , Morrison F. A.
Published: November 2010

Low Reynolds number flow in and about a droplet is generated by an electric field. Because the creeping flow solution is a uniformly valid zeroth-order approximation, a regular perturbation in Reynolds number is used to account for the effects of convective acceleration. The flow field and resulting deformation are predicted.
Bifurcation of Elastic-Plastic Circular Cylindrical Shells Under Internal Pressure
Authors: Chu C.-C.
Published: November 2010

The bifurcation of long elastic-plastic cylindrical shells subject to internal pressure is investigated. It is assumed that the end conditions are such that plane strain conditions prevail. For thin shells, simple approximate bifurcation criteria are obtained analytically. The finite-element method is then employed, in conjunction with separation of variables, to obtain the bifurcation conditions for cylindrical shells with arbitrary thickness to radius ratios. For sufficiently thin shells, the numerical and the analytical results are in good agreement for the critical pressure at bifurcation. The numerical and analytical results both indicate that, for sufficiently thin shells, a variety of bifurcation modes are available virtually simultaneously at this critical pressure. However, for thicker shells, the numerical results reveal that there is a single preferred bifurcation mode. The mode number associated with this preferred bifurcation mode depends on the thickness to radius ratio. The possibility of bifurcation occurring before the attainment of the maximum pressure is also explored. For the specific cases investigated here, bifurcation always occurs after the maximum pressure point.
Stability of a Rotor Partially Filled With a Viscous Incompressible Fluid
Authors: Hendricks S. L. , Morton J. B.
Published: November 2010

A hollow circular cylinder rotating with constant angular velocity and partially filled with a viscous incompressible fluid has been analyzed for stability. The analysis can be extended to apply to many different rotor geometries. The results of this analysis predict that over a range of operating speeds, the system is unstable. The extent of this unstable region is determined by the system parameters. The interplay between viscosity of the fluid and damping on the rotor is especially important in determining stability boundaries. A parametric study is presented for a rotor modeled as a cup in the middle of a symmetrically supported massless shaft. The rotor is subject to a linear spring and a linear damper. Rotor unbalance, gravity, and axial effects are considered negligible.
Nonstationary Narrow-Band Response and First-Passage Probability
Authors: Krenk S.
Published: November 2010

The notion of a non-stationary narrow-band stochastic process is introduced without reference to a frequency spectrum, and the joint distribution function of two consecutive maxima is approximated by use of an envelope. Based on these definitions the first passage problem is treated as a Markov point process. The theory is applied to the response of a linear oscillator excited by a stationary process from t = 0, and a simple algebraic relation between the non-stationary and stationary correlation functions of the response is derived.
Relationship Between the Creep of Solid and Foam Polyurethane Resulting From Combined Stresses
Authors: Nolte K. G. , Findley W. N.
Published: November 2010

A multiple integral representation was used to describe the constant stress creep of solid (full density) polyurethane under compression and combined tension and torsion. Also, the modified superposition principle was used to predict the material’s response to abrupt changes in stress with very satisfactory results. The functions found to describe the solid polyurethane were then used to predict the response of foam polyurethane with a specific gravity of 0.33 to similar stress histories. This was achieved by multiplying the stresses for the foam by 15.5, which was the ratio of the stiffness of the solid to that of the foam. This procedure satisfactorily predicted the creep behavior of the foam for constant stresses and abrupt changes in stress. Two models were considered for correlating the stiffness of a foam and its associated full-density material. One model, a close-packed array of spherical voids, was found to predict the correct density for the foam considered here. The observed stiffness of the foam fell within the bounds for the stiffness found for this model. The other model considered was a cubical space frame. This model was found to predict reasonably well the stiffness of the polyurethane foam and the stiffness of polystyrene foams of several densities. The space frame model also predicted several other observed features of the behavior of polyurethane foam.
Experimental Investigation of a Fluidic Volume Flowmeter
Authors: Wilson M. P. , Coogan C. H. , Southall K.
Published: November 2010

Tests were conducted on a fluidic oscillator for the purpose of determining its potential use as a flowmeter. Water, Bayol 35, and an ethylene glycol-water mixture were used as the test fluids. The effects of setback, aspect ratio, splitter distance, and feedback inlet location on oscillation frequency were investigated. Tests show that the oscillation frequency, when using liquids, is linearly related to volume flow rate. The tests show that the oscillation frequency was insensitive to both density and viscosity in the range investigated.
Two-Phase Eccentric Interface Laminar Pipeline Flow
Authors: Bentwich M. , Kelly D. A. I. , Epstein N.
Published: November 2010

The laminar velocity profiles of Bentwich [1] are integrated to give the volumetric flow rates in a tube of two immiscible liquids with an eccentric circular interface. By setting the viscosity of the core liquid equal to infinity, the velocity profiles and corresponding volumetric flow rates become those of a long free-flowing solid cylinder and its eccentrically annular liquid. Sample plots are given of nondimensionalized flow rates of both phases as a function of diameter ratio, eccentricity, and viscosity ratio. Flow enhancement (or pressure-drop reduction) and power reduction factors are also presented for typical cases.
A Computer-Simulated Method of Phase-Plane Displacements
Authors: Scharf Louis L.
Published: November 2010

A well-known graphical phase-plane technique for solving a wide variety of ordinary second-order differential equations is shown to satisfy a relatively simple set of iterative relationships which are easily programmed on a digital computer. The only restriction on the differential equation of interest is that it can be written as ax¨ + G(x, x˙, t) = 0, where G(x, x˙, t) = g(x, x˙, t) + kx. Consequently, many linear and nonlinear differential equations, with or without forcing functions, which may also have (explicit) time-variable coefficients, are easily solved with the method.
Dynamics of a Proportional Fluidic Amplifier: Part 2
Authors: Brown F. T. , Humphrey R. A.
Published: November 2010

A sixth-order lumped model is formed to represent the internal behavior of the fluidic amplifier tested in Part 1 up to over 800 Hz. Correlation with experiment is good for zero-load pressure, but an observed resonance or instability at elevated-load pressures is not properly predicted. Flow-visualization experiments are described from which four possible mechanisms are proposed for such resonances and instabilities observed in this and similar amplifiers. The study can be used to explain the successes of various design innovations tried earlier by others, to suggest further changes and associated performance limits, and to guide further needed research.
A Trace Method for Directly Synthesizing Liapunov Functions of Aperiodic Systems
Authors: Chen C. F. , Shieh L. S.
Published: November 2010

A direct synthesis technique is established for constructing the Liapunov function of a completely aperiodic system without assuming elements and solving simultaneous equations. By inspecting the traces of the state matrix and its products, a Liapunov function and its derivative can be immediately written. The determinant which has the same elements of the Liapunov function so obtained turns out to be a new criterion for testing whether or not a system involves repeated roots. This determinant for an aperiodic system is closely analogous to the Hurwitz determinant for a stable system.
Further Experiments With Suction at a Sudden Enlargement in a Pipe
Authors: Heskestad Gunnar
Published: November 2010

Previously reported experiments on incompressible flow through a step expansion in a pipe, as influenced by suction at the smaller diameter of the step, have been extended to examine effects of inlet flow on suction requirements and performance of the device as a (short) diffuser. Here the performance for a fully developed turbulent pipe flow is considered and compared to previous results for an inlet flow with thin boundary layer. Whenever overall diffuser length is restricted to values less than some upper limit for a given expansion ratio, then for either inlet flow condition, the present device is shown to produce higher pressure recoveries (adjusted for suction power) than conical diffusers.
The Natural Frequency of a Bubble Oscillating in a Viscous Compressible Liquid
Authors: Shima A.
Published: November 2010

The natural frequency of a spherical gas-filled bubble oscillating in a viscous compressible liquid is derived. Surface tension is also included in this solution, but gravity, gas diffusion and thermal conduction are neglected. The solutions of Minneart Richardson, Neppiras and Noltingk, Hirose and Okuyama, and Houghton are shown to be special cases of this solution. The effects of liquid compressibility, surface tension, and viscosity on the natural frequency of a bubble in water is determined as a function of the static radius. The effect of ratio of specific heats of gas in a bubble is also examined.
An Analytical Investigation of the Cavitation Hypothesis of Brain Damage
Authors: Benedict J. V. , Harris E. H. , von Rosenberg D. U.
Published: November 2010

An analytic investigation of the cavitation hypothesis of brain injury is performed by designing a mathematical model of the skull and brain subjected to an impact load. The skull is characterized as a thin, homogeneous, isotropic, elastic spherical shell, and the brain is assumed to be an ideal acoustic fluid. Using extensional shell theory, the skull-brain system is described by three coupled, simultaneous, linear partial differential equations with variable coefficients. The equations are solved by finite difference techniques. Results demonstrate that two prime focal points of reduced pressure occur within the fluid shortly after the onset of impact. These are located at the impact pole and at the counter pole or “contrecoup” site.
A Method of Measuring Relaxation of Stress for Aluminum Alloys
Authors: Holt Marshall , Bogardus K. O. , Jacobus P. H.
Published: November 2010

A method of measuring stress relaxation by the use of stressing frames, wherein a constant strain is maintained on the specimen, is discussed. The elastic strain introduced into the specimen during loading, at the start of the exposure, and the elastic strain relieved during unloading, at the end of the exposure, are measured. The difference in elastic strains can be used to determine the amount of stress relaxation that has taken place. The method seems to produce reliable measurements and has the advantages that it requires no very costly equipment, and the tests require little or no attention during the exposure periods. Although each test yields only one stress-time data point, many tests can be run simultaneously.
A Multiple Critical Flow Venturi Airflow Metering System for Gas Turbine Engines
Authors: Varner C. R.
Published: November 2010

An air metering system has been constructed using an array of critical flow venturis. By plugging individual venturis, the total metering area is varied to provide an airflow range from 25 lb per sec to 1200 lb per sec. A unique flow control valve and air straightening section provides low air velocity distortion at the entrance to the meter.
A High Precision Axisymmetric Triangular Element Used in the Analysis of Hydraulic Turbine Components
Authors: Chacour S.
Published: November 2010

A structural analysis program (Axibody) using conforming triangular finite elements is developed and applied to the study of composite axi-symmetric structures. Two types of elements are used: a novel axi-symmetric ring element and a two-dimensional plain stress element of varying thickness. The displacements in both cases are represented by a complete third-degree polynomial. The derivation of the stiffness and the consistent equivalent load matrices of the elements are described as well as a brief note on the program. Several examples are treated and the results are compared with the theoretical solution. A direct comparison with the results of a strain gauge test performed on a large stay ring—spiral case assembly is also made. Excellent agreement is obtained in all cases.
A Generalized Static Model for Fluidic Impact Modulators
Authors: Katz S. , Reid K. N.
Published: November 2010

A static model for predicting the input-output characteristics of direct and transverse impact modulators is presented. The model is based on the position and shape of the dividing streamsurface between the impacting jets. The streamsurface permits the separation and identification of the individual flow processes within the devices. Empirical relations are developed for each of the flow processes and combined to formulate the static model. Input-output characteristics calculated from the model are generally within 25 percent of measured characteristics. The pressure gain predicted by the model is shown to be highly sensitive to jet spreading characteristics and nozzle spacing.
An Axial Compressor End-Wall Boundary Layer Theory
Authors: Mellor G. L. , Wood G. M.
Published: November 2010

The essential ingredient missing in existing prediction methods for the performance of multistage axial compressors is that which would account for the effect of end-wall boundary layers. It is, in fact, believed that end-wall boundary layers play a major role in compressor performance and the absence of an adequate theory represents a handicap to turbomachinery designers that might be likened to the handicap that designers of wings, for example, would face if Prandtl had not introduced the idea of a boundary layer. In this paper a new theory is developed which retains all elements of classical boundary layer theory; for example, we discuss variables such as momentum thickness and wall shear stress. However, the present theory introduces new concepts such as axial and tangential defect force thickness, a rotor exit-stator inlet “jump condition” and the importance of these concepts is demonstrated. Inherent in the derivation is an identification of the role of secondary flow and tip clearance flow. A proper means of matching the boundary layer calculations to conventional main stream calculations is suggested. Independent of empirical parametization it appears that the theory is capable of correctly modeling boundary layer blockage, losses, and end-wall stall. Near stall, the main stream-boundary layer interaction is very strong.
Cyclic Plasticity: Some Properties of the Hysteresis Curve of Structural Metals at Room Temperature
Authors: Krempl E.
Published: November 2010

The hysteresis curve in the transient and steady-state stage is characterized by inequalities and periodicity conditions for the tangent to the hysteresis curve (dσ/dε) and its derivative (d2σ/dε2). Cyclic creep and cycle dependent stress relaxation are considered. Evidence exists that structural metals have a nonfading memory for two discrete items, the maximum stress amplitude of the cyclic steady state and the sign of dσ during the last unloading. The dσ-part of the memory can be erased by a gradual reduction in amplitude.
An Analysis of Vane-in-Rotor Pump
Authors: Somayajulu K. D. S. R.
Published: November 2010

Theoretical analysis of the vanes-in-rotor pump is presented in this paper. The interspace between the eccentric circles formed by the rotor and stator is expressed as a function of the angle. The annulus area variation and then the variation of the area between two adjacent vanes are used to find the pressure variation. Several ratios of rotor radius to stator radius, several number of vanes, different indices of compression, and different inlet and outlet port openings are considered for the investigation. Graphs presenting the variation of torque, frictional torque, output, mass flow, and efficiency are given. The analysis simplifies the design of the pump.
Linearized Potential Flow Models for Hydrofoils in Supercavitating Flows
Authors: Nishiyama Tetsuo , Ota Terukazu
Published: November 2010

A number of linearized models of fully cavitating flow about hydrofoils are investigated. Specifically, the cavity closure and wake behind the closure are examined and their effects on the characteristics of a symmetrical wedge, a base-vented hydrofoil, and a supercavitating hydrofoil of arbitrary shape are considered. By comparing theoretical and experimental results, the suitability of various flow models is examined and the one which gives the best results is explored in detail. A method based on the later model for calculating the characteristics of a hydrofoil with a cavity of finite length is presented.
An Instrument for Skin-Friction Measurements in Thin Boundary Layers
Authors: Nash-Webber J. L. , Oates G. C.
Published: November 2010

A simple instrument for skin-friction measurements in adiabatic turbulent compressible boundary-layers is described. Its small size makes its use possible in very thin boundary layers. A universal calibration relation is given. A method of applying the instrument to obtain hitherto unavailable measurements of skin-friction in flows with finite pressure-gradient is proposed.
Two-Phase, Two-Component Critical Flow in a Venturi
Authors: Smith R. V.
Published: November 2010

This paper reports the results of an analytical and experimental investigation whose object was to test the hypothesis that the flow of the gas phase controls critical and near critical two-phase flow for cases where the gas flow is essentially in separate streams. The results substantiate the hypothesis. The analytical results also indicate that one dimensional flow equations with reasonably accurate estimates for the droplet size and for the drag and heat transfer coefficients will adequately describe critical and near critical flow over a wide range of flow conditions.
Development of a New Laboratory Test Method for Spring Steels
Authors: Furr S. T.
Published: November 2010

Existing methods for evaluating spring steels in terms of load-loss resistance for automotive coil spring applications are very time-consuming and require special spring-making and spring-testing equipment. Over the years, the impracticalness of these methods has been an obstacle to the development of better spring steels. The present study shows how the torsional Bauschinger test can be used to predict the relative loadloss resistance of spring steels through correlations which were worked out during the laboratory investigation. Advantages of the torsional Bauschinger test are: (a) small, straight specimens are used, (b) the test takes only a few minutes, and (c) standard equipment is employed (a standard torsion tester). Results to date indicate that this test method will serve as a practical tool for providing the kind of information needed to develop improved spring steels.