bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical Approach for Vibration Analysis of an Axisymmetric Shell Structure With a Nonuniform Edge Constraint
Authors: Hwang Y. F.
Published: December 2011

A numerical approach for computing the eigenvalues and eigenfunctions of an axisymmetric shell with a nonaxisymmetric edge constraint is presented. The shell structures are modeled without constraint by an assemblage of axisymmetric shell elements. The constraint at any point along the edge circumference may be imposed by two linear springs acting against the axial and the radial degrees of freedom, and by a torque spring acting against the rotational degree of freedom. The nonuniform constraint is thus represented by the arbitrary distribution of these spring constants per unit length along the circumference. This arbitrary distribution of spring constants is then resolved by a Fourier series expansion. Utilizing the natural modes of the unconstrained shell as the generalized coordinates, the equations of motion which include the effects of a nonuniform constraint are derived. The mass and the stiffness matrices of these equations of motion are used as inputs for solving the linear numerical eigenvalue problem. A circular plate, which can be considered as an extreme case of an axisymmetric shell, is used as a numerical example. For a simply supported circular plate with a sinusoidal variation of rotational edge constraint, the computed results agree well with the data available in the literature.
Nondestructive Testing of Resin Mortar Using Ultrasonic Pulses
Authors: Morimitsu T. , Yabuta T. , Tsujimura T. , Nakayama T.
Published: December 2011

A quick-setting resin mortar has been developed to accomplish a new small diameter shield tunneling method. A nondestructive testing method employing ultrasonic pulses is used for estimating the strength of resin mortar. Young’s modulus, the density, the strength, and the ultrasonic velocity of resin mortar of varying contents are measured. The experimental and theoretical results show the possibility of nondestructive testing of resin mortar strength properties by using ultrasonic pulses.
Flow-Induced Vibrations of Mixing Vessel Internals
Authors: King R.
Published: December 2011

This paper draws together the results of research work undertaken at BHRA on cylinders excited to oscillate by flow within unbaffled mixing vessels. Oscillations of an anchor mixer and of dip tubes are described, including those cases in which the cylinders are mounted close to the vessel wall. The results are used to define guidelines for calculating safe operating limits of cylinders dipping into water, and for avoiding vortex excited oscillations of an anchor mixer by a device which actually improves its efficiency as a mixer.
Moving Harmonic Load on a Prestressed Thick Strip Plate
Authors: Chonan S. , Sugawara S.
Published: December 2011

This paper is a study of the steady-state response of an initially stressed, thick strip plate subjected to a sinusoidally oscillating moving line load. The problem is studied on the basis of a thick plate theory which takes into account the effect of the second-order increments of the normal stresses as well as the effect of the rotatory inertia and shear deformations. Critical speed for which a resonance effect occurs in the system is obtained. Further, the displacement of the plate is shown graphically for several values of the parameters included. The results are also compared with those from the classical thin plate theory.
The Finite Element Modeling of the Free Vibration of a Read/Write Head Floppy Disk System
Authors: Good J. K. , Lowery R. L.
Published: December 2011

The configuration of read/write head designs in floppy disk drive units is of import as some designs witness vibration phenomena which lead to signal loss and excessive wearing of the disk media. This paper presents finite element modeling, and results thereof of a read/write head floppy disk system in free vibration. The objective of this work, of which this study marks but the beginning, is to determine the design parameters of read/write head support structure which will reduce the vibration phenomena.
Dynamic Response of a Laminated Plate With Friction Damping
Authors: Han Shen Zhong
Published: December 2011

A sandwich-type plate with metal facings and felt core, fastened by bolts, was studied using both test and finite-element analysis. This type of plate is cheap, light, damping-effective and without pollution; therefore, it is widely used in astronautical engineering. The tests were conducted for different felt thicknesses, bolt numbers, and fastening forces. The results show that the damping depends on friction between the plates and the felt. As compared with an identical stiffness solid plate, the damping of laminated plates can be increased up to 30 times. A mesh with rectangular elements was adopted in the finite-element analysis. In accordance with the slipping mechanism, a rectangular plate clamped on one edge was analyzed with the foregoing elements to determine the resonant frequency and the damping. The difference between the calculated and tested results was within 5 percent for the resonant frequency.
A Contribution on Forced Periodic Oscillations With Piecewise Linear and Constant Damping
Authors: Karius D.
Published: December 2011

In control system design and precision mechanics it is important to know the precise motion of excited or self-excited vibration under the influence of dry friction. In this paper, the motion of such a nonlinear oscillator is analyzed with the aid of pointmappings. As an example, a nonlinear function of damping dependent on the velocity can be approximated by piecewise linear functions. For this example, the stability of periodic solutions of the type q (t+T/2) = −q(t), (T = period, t = time), is discussed. The case of “critical stability” leads to potential points of bifurcation (branching-off solutions) which are investigated. Calculated examples are compared with experiments.
Vibration and Shock Isolation Performance of a Semi-Active “On-Off” Damper
Authors: Rakheja S. , Sankar S.
Published: December 2011

The concept of an “on-off” damper employing the feedback signals from directly measurable variables is proposed. A control scheme utilizing the directly measurable relative position and relative velocity signals to produce the command signal is configured. The on-off damping mechanism can be achieved through the modulation of orifice area in a conventional hydraulic damper, using a two position on-off valve driven by the command signal. The shock and vibration isolation characteristics of the proposed on-off damper are evaluated through computer simulations. The shock and vibration isolation performance characteristics of the proposed damper are compared to the performance characteristics of a passive and an on-off damper utilizing the feedback from absolute and relative velocity signals.
Calculation of Nonlinear Unbalance Response of Horizontal Jeffcott Rotors Supported by Ball Bearings With Radial Clearances
Authors: Saito S.
Published: December 2011

Nonlinear unbalance response of horizontal Jeffcott Rotors supported by ball bearings with radial clearances are investigated. First, the method to calculate the nonlinear vibration of the rotor as well as the expression of the nonlinear bearing force are given using the numerical harmonic balance technique. It is shown that there are 4 types to the unbalance response, which consist of the horizontal, the vertical, the intermediate, and the circular modes. The former three types of vibrations always take place, but the last appears only when the critical unbalance is exceeded. Moreover, the design technique to avoid the appearance of the last type of vibration is discussed, because the maximum amplitude of the last type may become quite large.
A Conical Beam Finite Element for Rotor Dynamics Analysis
Authors: Greenhill L. M. , Bickford W. B. , Nelson H. D.
Published: December 2011

The development of finite element formulations for use in rotor dynamics analysis has been the subject of many recent publications. These works have included the effects of rotatory inertia, gyroscopic moments, axial load, internal damping, and shear deformation. However, for most closed-form solutions, the element geometry has been limited to a cylindrical cross-section. This paper extends these previous works by developing a closed-form expression including all of the above effects in a linearly tapered conical cross-section element. Results are also given comparing the formulation to previously published examples, to stepped cylinder representations of conical geometry, and to a general purpose finite element elasticity solution. The elimination of numerical integration in the generation of the element matrices, and the ability of the element to represent both conical and cylindrical geometries, make this formulation particularly suited for use in rotor dynamic analysis computer programs.
Three New Methods of Modal Identification
Authors: Jezequel L.
Published: December 2011

The identification of linear systems based on their dynamic responses has been the object of a great number of studies. In this work, we propose three new identification procedures which can be programmed on a microcomputer. The first of these methods uses an analytical extension of the transfer function, the second method uses a special integral transformation based on the Cauchy-Weierstrass theorem and the last method uses orthogonalization of the experimental displacement shapes by the Ritz-Galerkin procedure. These methods allow rapid detection of the modal parameters. Presented separately, they are applied to identical structure models defined in the first part of this study.
The Accuracy of Frequency Response Function Measurements Using FFT-Based Analyzers With Transient Excitation
Authors: Cawley P.
Published: December 2011

The accuracy of the frequency response measurement obtained using impact excitation and a Fast Fourier Transform based spectrum analyzer has been investigated. It has been shown that with impact excitation, provided the impacts are reproducible and the extraneous noise level is low, the coherence estimates obtained from the analyzer are unity, irrespective of the frequency resolution employed. Hence the H1 (Sxy/Sxx) and H2 (Syy/Sxy*) frequency response function estimates are identical. However, these frequency response function estimates are affected by a bias error caused by inadequate frequency resolution so unity coherence does not necessarily imply accurate results. The results with impact excitation are compared with those obtained using random excitation where both the coherence and frequency response function estimates are affected by bias error. The bias error in the frequency response function estimates with impact excitation is intermediate between that in the H1 and H2 estimates when random excitation is used. The theoretical predictions have been verified by tests on an analogue computer and on a built-up structure.
Engineering Aspects of Ultrasonic Process Control—Flow, Temperature and Liquid Level Applications
Authors: Lynnworth L. C.
Published: December 2011

The interaction of ultrasonic waves with solid, liquid, gaseous, or multiphase media offers many opportunities for accurate process control, but users risk disappointment because of the influence of “unwanted” variables. The present paper illustrates the use of ultrasonic transit time or amplitude measurements as a basis for calculating flow, temperature, and liquid level. The interrogating wave types include longitudinal, extensional, Rayleigh, transverse shear and torsional modes, at frequencies on the order of 0.1 to 1 MHz. Buffer techniques, special paths, or other means are illustrated for minimizing, avoiding, or compensating for the influence of undesired variables.
Turbulent Buffeting of a Multispan Tube Bundle
Authors: Au-Yang M. K.
Published: December 2011

An expression to calculate the buffeting response of a multispan tube bundle with nonconstant linear mass density is derived by generalizing Powell’s joint acceptance concept. Application of the equation to lock-in vortex-induced vibration analysis is also discussed.
Mechanical Power Flow Between Stiffened Plates and Viscoelastic Discrete Systems
Authors: Goldfracht E. , Rosenhouse G.
Published: December 2011

In this paper we primarily discuss a theory of power transmission and vibration energy distribution of dynamically loaded structures. The loads are random and the system comprises linked elements, which consist of machine-supported stiffened plates. Fundamentally, the theory is deterministic, but in addition it uses some features of the SEA. In fact, the analysis is intended to verify fundamental theorems of the Statistical Energy Analysis in the lower frequency range.
Detecting Fatigue Cracks in Gears by Amplitude and Phase Demodulation of the Meshing Vibration
Authors: McFadden P. D.
Published: December 2011

A digital signal processing technique is proposed for calculating the amplitude and phase modulation of the tooth meshing vibration of a gear from the signal average of the vibration with application to the early detection of local defects such as fatigue cracks. The importance of phase modulation in the detection of defects is confirmed.
An Improved Transfer Matrix-Direct Integration Method for Rotor Dynamics
Authors: Gu Jialiu
Published: December 2011

A transfer matrix-direct integration combined method is proposed, which employs the transfer matrix method to derive the equations of motion of a “characteristic disk,” and uses the direct integration method to determine the critical speeds, modes and unbalance response of a rotor-bearing system, and to analyze its stability. Despite the complexity of the system, the number of governing equations is not greater than eight. For a single-spool rotating system, the number of equations is only four. A transfer matrix for a uniform shaft is derived to consider its distributed mass, moment of inertia and the effect of shearing force. An impedance matrix iteration method is proposed to consider the effect of a complicated bearing-supporting system on the rotor dynamics. Two examples are given, and the results agree satisfactorily with the experiments.
Parameter Sensitivity in the Dynamics of Rotor-Bearing Systems
Authors: Rajan M. , Nelson H. D. , Chen W. J.
Published: December 2011

When designing a rotor system it is frequently desirable to have at hand a set of design sensitivity coefficients which quantitatively predict a change in specific system characteristics to changes in design parameters. This paper presents eigenvalue sensitivity coefficients for the damped natural frequencies of whirl of general linear rotor system modelled by finite element discretization. In addition, a simple and direct method for calculation of the damped critical speeds is presented, which utilizes the eigenvalue sensitivity with respect to the spin speed. It is shown that the combination of design parameter and spin speed whirl frequency sensitivity coefficients may be used to also evaulate the damped critical speed sensitivity coefficients.
Coupling Between Spans in the Vibration of Axially Moving Materials
Authors: Ulsoy A. Galip
Published: December 2011

Axially moving materials (e.g., belts, chains, bandsaws, paper and magnetic tapes, etc.) arise in various mechanical systems, and their vibration and stability are often of engineering significance. Previous work describing the transverse vibration of axially moving materials is extended in this paper to include the elastic coupling between spans. The equations of motion are derived, an approximate solution method is developed and simulation results are presented. The simulation results predict the presence of a beating phenomenon at low transport velocities which is destroyed by higher velocities and/or tension differences in the two spans. The coupling mechanism described could potentially be exploited for vibration control.
Damage Evaluation and Life Extension of Structural Components
Authors: Coffin L. F.
Published: December 2011

This paper describes an approach to life prediction in which critical elements of major structural components are continuously monitored by appropriate damage indicators for structural damage, and, based on the indicated damage state, an on-line assessment is made of the remaining life. Concurrently alternative corrective measures can then be assessed and, if the life has been found wanting, appropriate actions taken. The process is viewed as a continuous one whereby the current remaining life of critical elements is known as the plant ages. The need for applying such procedures becomes increasingly important as some of our major structures approach their design life and concerns arise regarding retirement and replacement versus life extension. Important elements of this approach include definitions of damage, appropriate damage monitors, damage assessment, life prediction, and conseqeunces of corrective action. This paper treats these elements in the context of past history and current programs associated with pipe cracking in nuclear power plants.
New Power Transmission Chain Design
Authors: Kin Y. , Dubrovsky R.
Published: December 2011

Precision multiple roller power transmissions are investigated in this work. These chains transfer significant power and move with very high velocity. They are subjected to variable loading with strong vibration and impact components, and require forced stream lubrication. Because of these severe working conditions, chain life is limited by the fatigue, and the chain plates are the weakest elements in many cases. It is shown that fatigue life is significantly decreased by fretting action, high stress concentration in the plates, and the impossibility of maintaining a uniform force distribution across the multiple lines of a chain. The results of the performed experimental stress analysis under static and variable loading are given for the different plate geometries. The plates with a variety of stress reducers located in different areas are investigated, and theoretical and effective stress concentration factors are determined. Based on that, new plate chain designs are proposed. These new designs use fewer lines to transfer the same power as conventional chains.
Calculation of Mixed Mode Fracture Stress Intensity Factors in an Orthotropic Plate Using Finite Element Technique
Authors: Hurlbut A. , Loo F. T. C.
Published: December 2011

A finite element technique using the eight-node quadrilateral isoparametric element is presented to calculate stress intensity factors in orthotropic plates. The procedure is general so as to include multilayered laminates with varying laminae directions and thicknesses. This method can easily solve problems with various loading conditions and plate geometry. Several examples with solutions available in literature are solved to examine the accuracy of the current approach. Solutions of more complicated and practical engineering fracture problems are also presented to demonstrate the versatility of this method.
Measurements of Fluctuating Wall Pressure for Separated/Reattached Boundary Layer Flows
Authors: Farabee T. M. , Casarella M. J.
Published: December 2011

Measurements were made of the wall pressure field beneath separated/reattached boundary layer flows. These flows consisted of two types; flow over a forward-facing step and flow over a backward-facing step. Wall pressure fluctuations from an equilibrium flat plate boundary layer flow were also measured and used as a baseline for comparative purposes. Values of the RMS fluctuating pressure as well as the frequency spectral density, phase velocity, and coherence of the surface pressure field were measured at various locations upstream and downstream of the steps. The experimental results show that the separation-reattachment process produces large-amplitude, low-frequency pressure fluctuations. The measured spectral statistics of the wall pressure fluctuations are consistent with the view that at reattachment there exists a region of coherent highly energized velocity fluctuations located near the wall which, as it convects downstream, decays and diffuses away from the wall. This energized region remains identifiable in the wall pressure statistics as far as 72 step heights downstream of the backward-facing step.
An Experimental Study of the Flow and Wall Pressure Field Around a Wing-Body Junction
Authors: Hasan M. A. Z. , Casarella M. J. , Rood E. P.
Published: December 2011

The flow and wall-pressure field around a wing-body junction has been experimentally investigated in a quiet, low-turbulence wind tunnel. Measurements were made along the centerline in front of the wing and along several spanwise locations. The flow field data indicated that the strong adverse pressure gradient on the upstream centerline causes three-dimensional flow separation at approximately one wing thickness upstream and this induced the formation of the horseshoe root vortex which wrapped around the wing and became deeply embedded within the boundary layer. The wall-pressure fluctuations were measured for their spectral content and the data indicate that the effect of the adverse pressure gradient is to increase the low-frequency content of the wall pressure and to decrease the high-frequency content. The wall pressure data in the separated region, which is dominated by the horseshoe vortex, shows a significant increase in the low-frequency content and this characteristic feature prevails around the corner of the wing. The outer edge of the horseshoe vortex is clearly identified by the locus of maximum values of RMS wall pressure.
Torsional Vibrations and Dynamic Loads in a Basic Planetary Gear System
Authors: August R. , Kasuba R.
Published: December 2011

An interative method has been developed for analyzing dynamic loads in a light weight basic planetary gear system. The effects of fixed, semi-floating, and fully-floating sun gear conditions have been emphasized. The load dependent variable gear mesh stiffnesses were incorporated into a practical torsional dynamic model of a planetary gear system. The dynamic model consists of input and output units, shafts, and a planetary train. In this model, the sun gear has three degrees of freedom; two transverse and one rotational. The planets, ring gear, and the input and output units have one degree of freedom, (rotation) thus giving a total of nine degrees of freedoms for the basic system. The ring gear has a continuous radial support. The results indicate that the fixed sun gear arrangement with accurate or errorless gearing offers in general better performance than the floating sun gear system.
Effect of Transmission Path on Measured Gear Vibration
Authors: McFadden P. D. , Smith J. D.
Published: December 2011

The transmission of gear tooth meshing vibration from the tooth contact region to the shaft, through rolling element bearings and then through the gearbox casing can have an important influence on the measured vibration sepctrum. In critical applications the measurement of the torsional vibration of the gear may be preferable.
The Adaptation of Kron’s Method for Use With Large Finite-Element Models
Authors: Turner G. L. , Milsted M. G. , Hanks P.
Published: December 2011

Kron’s method of dynamic substructure coupling is modified and extended to a form which is well suited for use with large finite-element substructure models. It is shown how both mass condensation and modal truncation can be applied at the substructure level in a manner compatible with the Kron coupling procedure. Either master or slave freedoms may be used as coupling coordinates in the system model, thereby allowing complete flexibility at the substructure analysis stage and in particular, allowing the use of automatic master selection procedures. Substructures may be coupled either directly or through a flexible interlayer. System damping may thus be represented in a fairly general way with each substructure having its own (uniform) damping level but with the further provision of additional damping at the joining surfaces between substructures. The theory is illustrated by examples with simple mass-spring systems.
Modeling General Hysteresis Behavior and Random Vibration Application
Authors: Baber Thomas T. , Noori Mohammed N.
Published: December 2011

A simple constructive technique for the development of rate-type hysteresis models for general nonlinear system is presented. The technique is used to develop hysteresis models to incorporate time history-dependent postyield restorting forces, and general pinching behavior in smoothly varying deteriorating models. Applications of these models to random vibration analysis modeling via simulation and equivalent linearization techniques under Gaussian noise excitation is presented.
Structural Optimization of Cantilever Mechanical Elements
Authors: Rivin Eugene I.
Published: December 2011

Naturally limited stiffness of cantilever elements due to lack of constraint from other structural components, together with low structural damping, causes intensive and slow-decaying transient vibrations as well as low stability margins for self-excited vibrations. In cases of dimensional limitations (e.g., boring bars), such common antivibration means as dynamic vibration absorbers have limited effectiveness due to low mass ratios. This paper describes novel concepts of structural optimization of cantilever components by using combinations of rigid and light materials for their design. Two examples are given: tool holders (boring bars) and robot arms. Optimized boring bars demonstrate substantially increased natural frequencies, together with the possibility of greatly enhanced mass ratios for dynamic vibration absorbers. Machining tests with combination boring bars have been performed in comparison with conventional boring bars showing superior performance of the former. Computer optimization of combination-type robot arms has shown a potential of 10–60 percent reduction in tip-of-arm deflection, together with a commensurate reduction of driving torque for a given acceleration, and a higher natural frequencies (i.e., shorter transients). Optimization has been performed for various ratios of bending and joint compliance and various payloads.
Wave Propagation and Attenuation in Piping Systems
Authors: Nanayakkara Shiran , Perreira N. Duke
Published: December 2011

Results of an investigation on wave propagation in two-dimensional fluid-filled piping systems is reported. This phenomenon is studied by first developing a model for the transmission of solid-borne and fluid-borne vibrations in fluid-filled piping system elements, such as bends and straight sections. The aforementioned model, which is represented by an element transmission matrix, is used to determine the transfer and point impedances between the motion and forces of both the pipe and the fluid at any point within the element. It allows for longitudinal vibrations in the fluid, and longitudinal and bending vibrations in the solid portion of the system. The effects of both shear strains and rotary inertia within the pipe are included, while the effects of fluid flow and radial or angular modes in the fluid are neglected. Computer results for two-dimensional piping systems with modes of vibration in the plane of the pipes are considered. This method which is exact, except for possible computational errors, can be easily extended to the three-dimensional case.
Application of the Helmholtz Integral in Acoustics
Authors: Latcha M. A. , Akay A.
Published: December 2011

The solution of an isoparametric, overdetermined formulation of the Helmholtz Integral is presented and demonstrated in three examples of acoustic radiation from spherical sources. The placement of the interior, overdetermining points is discussed and guidelines concerning surface element size are developed and tested. The total radiated sound power and transient acoustic response of a dilating sphere are computed.
Stable Method for Active Cancellation of Duct Noise by Synthesized Sound
Authors: Kido K. , Morikawa S. , Abe M.
Published: December 2011

This paper describes an active noise cancellation system utilizing computer-synthesized sound. This computer-synthesized sound is generated by using a new method to estimate the impulse response of a system involving inverse transfer function of a loudspeaker. A loudspeaker is set close to the end of a duct to radiate sound for cancellation. The loudspeaker is driven by a signal which is synthesized by convoluting the estimated impulse response and the wave form of a noise picked up by a microphone set in the duct. The system is substantially stable. In our experiment, using a duct 8.5 m in length, the sound pressure at a point outside the duct is decreased by about 3 to 8 dB over a frequency range between 50 Hz and 200 Hz.
Transmission of SH Waves Through a Periodic Array of Elastic Cylinders
Authors: Varadan V. V. , Lakhtakia A. , Varadan V. K.
Published: December 2011

The reflection and transmission characteristics of a grating of identical, circular elastic cylinders, arranged periodically in an elastic slab, are investigated. Use is made of a simple approach synthesized from Fourier-Bessel expansions and the T-matrix method for the analysis of a two-dimensional problem involving SH waves only. It is observed that the nonspecular modes are generally very weak for such gratings in contrast with those for gratings made of periodic bimaterial interfaces. The presented analysis may be easily extened to the case of diffraction of incident P-and/or SV-waves, and should be useful for noise control applications.
Acoustic Radiation From Bending Waves of a Plate
Authors: Ingard K. Uno , Akay A.
Published: December 2011

In the commonly used definition of acoustic “radiation efficiency” of a plate, it is assumed that the amplitude of a traveling harmonic wave on the plate is kept constant, independent of the acoustic radiation load on the plate. As a result, this definition leads to an infinite value of the radiation efficiency when there is coincidence between the speed U of the traveling wave and the sound speed c in the surrounding fluid. The result of infinite radiation efficiency can be avoided if we consider the more realistic situation in which the plate is driven by a traveling force distribution, in which the amplitude of the force rather than the displacement is independent of the radiation load. This situation is considered here, and a modified definition of radiation efficiency is proposed. The displacement amplitude of the plate will have a maximum when the speed U of the force distribution equals the speed cb of free running bending wave on the plate. Then, if U < c, there is no power in the radiated wave and the power transferred from the plate to the fluid goes into heat as a result of viscothermal losses in the fluid. On the other hand, if U > c, the bulk of the power goes into the plane wave radiated from the plate. Finally, if U → c, the displacement and radiated power → 0 since the radiation impedance → ∞. In regard to the role of the viscothermal effects, it is interesting to find that at the coincidence frequency the contributions to the reactive part of the load impedance on the plate from the viscothermal boundary layer and the viscothermal losses in the bulk of the surrounding fluid almost cancel each other and the contributions to the resistive load are approxiamtely equal when U ∼ c.
Estimating Fatigue Due to Cyclic Multiaxial Stress
Authors: Orthwein W. C.
Published: December 2011

A new expression similar to the Huber-von-Mises-Hencky criterion for multiaxial stresses, also known as the distortional energy theory, is derived from the second order stress invariants of the stress tensor, rather than from the deviatoric stress tensor, as in the derivation of the Huber-von Mises-Hencky criterion. It is proposed as a mutually constant design criterion for fatigue resistance under the action of multiaxial cyclic stresses which may be used with either the Gerber-yield criterion or the Goodman-yield (modified Goodman) criterion. As is shown in the following paragraphs, neither of these criteria may be used with the Huber-von Mises-Hencky criterion; it is suited only for the Soderberg criterion which does not involve the ultimate stress.
Trends in Eigenvalues of Straight and Bent Beams on Elastic Supports
Authors: Bourne F. R. , Dixon M. W.
Published: December 2011

Singular value analysis is used to develop eigenvalue and eigenvector trends for beams supported by periodically-spaced, elastic elements. These trends are illustrated for both straight and bent beams as a function of the number of spans in the system, the boundary conditions, and the ratio of support to beam stiffness. As might be speculated, the effect of boundary conditions decreases as the number of spans increases. Also the effect of a bend becomes more pronounced as the bend is moved nearer the center of the beam. Simplified models are presented which provide excellent approximations of the first natural frequency for certain values of the ratio of support to beam stiffness.
On the Vibration Damping of a Plate by Means of a Viscous Fluid Layer
Authors: Ingard K. Uno , Akay Adnan
Published: December 2011

Vibration damping of a plate by means of a fluid layer is investigated. First, the frequency-dependent flow resistance of a fluid layer is explained with a simple illustration of the damping mechanism. Then, the vibration response of a plate is examined when it is backed by a rigid plane or another flexible plate with a fluid layer constricted in-between. Effects of the plate motion and acoustic radiation on the damping mechanism are also considered. The numerical results are presented in terms of frequency response of the plates.
Vibration and Damping Analysis of Rectangular Plate With Partially Covered Constrained Viscoelastic Layer
Authors: Lall A. K. , Asnani N. T. , Nakra B. C.
Published: December 2011

The Rayleigh-Ritz method is applied for the damping analysis offlexural vibrations of a simply supported plate, partially covered with constrained viscoelastic damping treatment. The anaysis is carried out in terms of resonant frequencies and associated modal system loss factors. Single-term solutions for respective modes are assumed for the longitudinal displacements of the constraining layer and the transverse displacement of the plate. The variations of the resonant frequency and the associated modal loss factor with the coverage percentage, the coverage location, the core shear modulus and the thickness of the constrained and the constraining layers have been reported.
A Linear, Frequency Domain Filter for Parameter Identification of Vibrating Structures
Authors: Mottershead John E. , Lees Arthur W. , Stanway Roger
Published: December 2011

In this paper the authors present a linear, least-squares, frequency domain filter for the identification of structural vibration parameters, such as mass, stiffness, and damping, from observed forces and responses. The method is based on an equation error formulation which produces a measurement equation which is linear in the unknown parameters. Convergence of the parameter estimates is achieved rapidly and the period required to obtain convergence is indicated by the CPU time measured on an IBM 3083 computer. Results obtained using simulated data are used to compare the linear filter with alternative filter formulations. Experimental results from a portal frame rig are given to demonstrate the application of the method to physical measurements.
Vibration Control of Flexible Multibody Aircraft During Touchdown Impacts
Authors: Shabana A. A. , Patel R. D. , DebChaudhury A. , Ilankamban R.
Published: December 2011

A method is presented for the dynamic analysis and vibration control of large scale flexible multibody aircraft during the touchdown impacts and rollover motion. The rollover motion is simulated by modeling the uneven runway profile as a stationary zero mean space dependent random process defined by its spectral shape. The prescribed motions at the two landing gears will then represent a different time dependent random process with spectral shapes changing with the change in velocity of the aircraft. Composite materials which provide higher stiffness-to-weight ratios are used as a passive control system to reduce the aircraft vibration. The results of the numerical example presented showed that the use of composites can have a significant effect on attenuating the vibration of the aircraft during the touchdown impact and rollover motion. The numerical results are obtained using the general purpose computer program DAMS (Dynamic Analysis of Multibody System).
Stresses in a Helical Spring of Arbitrary Cross Section With Consideration of End Effects
Authors: Nagaya K.
Published: December 2011

This paper presents expressions for stresses in the spring due to compression or tension in the direction of the axis of the cylindrical coil. In deriving stresses in the spring, it is necessary to first obtain resultant forces and resultant moments which occur in the coil spring. Then the analysis first derives exact results based on three-dimensional curved beam theory in which all displacements and all forces in three orthogonal directions of the coil spring are included with consideration of the constraints of the ends of the spring. Since the boundary shape of the spring is irregular, it is also difficult to satisfy stress-free boundary conditions along the surface of the coil, so that this paper applies the Fourier expansion collocation method and obtains stresses in the coil spring based on the theory of elasticity.
A Semi-Analytical Investigation of Fatigue Stresses in a Bolted Headplate by Finite Elements and Classical Plate Theory
Authors: McPhate A. J. , Gipson G. Steven , Ortiz J. C.
Published: December 2011

A semi-analytical analysis involving finite elements in conjunction with classical plate theory is used to determine the stress state in a concentrated region of the headplate on an industrial ball mill. The study illustrates the practical benefits of combining analysis techniques. With this procedure, manufacturing errors in the mill design and construction are confirmed to be a facing cut and a series of nonstructural welds on a wrapper plate between the headplate and its bearing bell mounting. The early failure of the ball mill is shown to arise from the combined detrimental effects of the residual stresses formed in the welds and groupings of broken bolts in the headplate assembly. The result, confirmed by actual site examinations, is an emphatic positive verification of the merits of hybrid analysis methods, when applied in a rational manner.
The Control of Parametric Vibration in a Simply Supported Beam
Authors: Burdess J. S.
Published: December 2011

The paper shows how unstable parametric vibrations of a uniform beam can be controlled. A control law is proposed and it is shown that the beam can be made to vibrate at a present amplitude at its natural frequency. The beam is modelled by its first mode and a solution to the governing equation of motion is derived by applying the multiple scales perturbation method. The results of the theoretical analysis are verified by a numerical simulation.
A Nonlinear Oscillator Lanchester Damper
Authors: Asfar K. R. , Nayfeh A. H. , Barrash K. A.
Published: December 2011

The method of multiple scales is used to investigate the effect of a nonlinear spring in the main system on the performance of Lanchester-type absorbers. A second-order uniform expansion is obtained for the response of the system to a harmonic excitation. Numerical results for steady-state solutions illustrating the influence of the nonlinearity and damping factors on the response are presented. A softening-type effective nonlinearity dominates the system and considerably improves its damping.
Using Transfer Matrices for Parametric System Forced Response
Authors: David J. W. , Mitchell L. D. , Daws J. W.
Published: December 2011

For many years, engineers and scientists have sought to deal with the many phenomena exhibiting parametric characteristics. While many approximate techniques are available for the analysis of such systems, the harmonic balance technique can be used to accurately model the response of systems where the coefficient variation is large. Also, in analyzing complex physical systems, analysts have sought to develop efficient computational techniques that are sufficiently general for the analysis of arbitrary systems. In this paper, it is shown that combining the harmonic balance technique with transfer matrices produces an efficient computational technique for the analysis of parametric systems where the coefficient variations can be large. The technique is demonstrated by considering a single-degree-of-freedom system with time varying stiffness. The harmonic balance technique is used to frequency-branch the transfer matrices, thus allowing multifrequency response calculations to be done simultaneously. The results are compared with direct numerical integrations of the equations. Lastly, this technique is applied to a simple gear coupled rotor system to demonstrate the application of this technique to large order systems of more engineering relevance.
Dynamic Stability and Response of a Beam Subject to a Deflection Dependent Moving Load
Authors: Katz R. , Lee C. W. , Ulsoy A. G. , Scott R. A.
Published: December 2011

The dynamic stability and transverse vibration of a beam subject to a deflection dependent moving load is considered. The deflection dependent moving load is motivated by the cutting forces in machining operations. Galerkin’s method is used to obtain a set of ordinary differential equations with periodic coefficients. It is found that parametric instability can be expected for a continuous sequence of moving loads. The response under the moving deflection dependent load is also calculated.
Safety Factor in Fatigue Under Fluctuating Stresses
Authors: Avakov V. A.
Published: December 2011

It is common to assume identical allowable safety factors in static strength [m], defined by mean stress (Sm), and in fatigue [a], defined by stress amplitude (Sa), in order to find the full safety factor (F) under asymmetrical cycles, or to plot any type of the Sm–Sa diagram of allowable stresses. Here additional modification is considered to generalize expression of the full factor of safety in fatigue under asymmetrical stresses, utilizing unequal allowable safety factors in static strength (by mean stress) and in fatigue (by stress amplitude): ([a] ≠ [m]). We assume that loading is stationary, and cumulated number of cycles is large enough to consider high cycle fatigue.
A Numerical Investigation of the Influence of Heating on the Excitation of High and Low Mach Number Jet Flows
Authors: Scott J. N. , Hoo E. A.
Published: December 2011

The influence of heating and velocity on the unsteady nature of jet mixing layers is investigated by solving the time-dependent compressible Navier-Stokes equations using MacCormack’s explicit finite difference algorithm. The computations are performed for jet Mach numbers of 0.3 and 0.8 with flow total temperatures up to 800K. The Reynolds number ranges from 3 × 105 to 1.3 × 106. Excitation is accomplished by imposing an acoustic pressure signal inside the jet duct. The objective of this effort is to compare the response of heated and unheated jets with acoustic excitation at high and low subsonic Mach Numbers. The preliminary results indicate that without acoustic excitation the mixing in the heated jet is greater than in the unheated case. It has also been found that for the low speed heated jets (M= 0.3, Tt = 672K) acoustic excitation causes the production of large scale vortex structures to occur in a regular periodic manner with organized periodic pairing at some Strouhal numbers. These results are in agreement with experimental data.
Optimal Control Deconvolution for Velocity Meter Signals
Authors: Clarkson P. M. , Hammond J. K.
Published: December 2011

A method of deconvolution has been developed which uses the techniques of optimal control. The application of the technique to velocity meter signals is presented. It is shown that provided a state-space model of the transducer dynamics can be obtained the method can provide effective deconvolution even when the data are corrupted by measurement noise. As well as the deconvolution method and the control of the measurement noise the formation of the state-space model and the effects of inaccurate estimation of system parameters are considered. Results are presented using both simulated and experimental data.
An Analysis of Rivet Die Design in Electromagnetic Riveting
Authors: Reinhall P. G. , Ghassaei S. , Choo V.
Published: December 2011

This paper presents the findings of a numerical and experimental study of the quality of 7050-T73 aluminum rivets formed by an extremely fast electromagnetic riveting process. It is found that without careful design of the rivet forming die large strains are produced which cause crack formation in the rivet heads. By the use of finite element and experimental techniques, it is shown that control of the radial component of the flow of material in the rivet head is essential in avoiding crack formation. A rivet die design which is effective in producing high quality, crack free, rivets is proposed.
Radial-Interradial Spring Tire Models
Authors: Badalamenti J. M. , Doyle G. R.
Published: December 2011

Two radial-interradial spring tire models are developed to predict vertical and drag forces produced by a tire as it rolls over an obstacle. Interradial springs are used to interconnect radial linear or quadratic springs to make each tire element’s deflection dependent upon its adjacent element’s deflections. Forces predicted by these two models are compared with a previously developed quadratic radial spring tire model and test data. The newly developed quadratic radial-linear interradial spring tire model predicts vertical and drag forces that are in close agreement with the test data.
Improvements in Lightly Loaded Rotor/Bearing and Rotor/Seal Models
Authors: Muszynska A.
Published: December 2011

A model for lightly loaded steadily rotating shaft/bearing/seal systems is proposed in this paper. The model is based on modal characteristics for the rotor, and rotational characteristics for the fluid dynamic forces generated in bearings and/or seals. The fluid average circumferential velocity ratio as a nonlinear function of shaft eccentricity represents a key factor in the model. The model is extremely useful for rotor stability analysis. The model adequacy was proved for one and two lateral mode models of rotors.
Experiments and Calculations on the Vibrations of Rotating Radial Impellers
Authors: Irretier Horst
Published: December 2011

Experimental and numerical results on the vibrations of a rotating radial impeller are presented. They show natural frequencies as a function of rotational speed, the mode shapes, the resonance excitation frequencies of the forward and backward rotating waves, and a response diagram during a run-up of the impeller.
Rotor Active “Anti-Swirl” Control
Authors: Muszynska A. , Franklin W. D. , Bently D. E.
Published: December 2011

Rotor self-excited vibrations due to solid/fluid interaction, such as occurring in seals, can easily be reduced or eliminated by controlling fluid circumferential velocity. This is known as “anti-swirl” technique. An active “anti-swirl” control system for rotating machines is described in the paper. While mainly controlling rotor self-excited vibrations, this active control system reduces also rotor lateral vibrations caused by other factors (such as unbalance), by increasing the system effective damping.