bluuebunny/crossref_metadata_2025_split huggingface dataset:
Progress in Applying the Surface Variational Principle to Analyze Acoustic Radiation From Slender Elastic Bodies
Authors: Wu Kuangcheng , Ginsberg Jerry H. 
Published: March 2021

Abstract
The surface variational principle (SVP) has been developed as a method for gaining analytical-type results for radiation and scattering from submerged bodies whose shape does not suit classical techniques for analyzing the Helmholtz equation. The approach employs Ritz series expansions for surface pressure and velocity in the frequency domain. The relation between the series coefficients is obtained by extremizing the SVP functional. The present work extends the earlier developments to the case of an axisymmetric elastic shell that is subjected to an arbitrary excitation. The surface pressure and normal velocity are represented as a sequence of surface waves that are the trace of the waves in the surrounding fluid medium. SVP is used to determine the wavenumber spectrum of pressure amplitudes generated by a specific wave having unit velocity amplitude. The structural displacement field is represented by Ritz expansions, and equations governing the generalized coordinates associated with these series are obtained by invoking Hamilton’s principle. Difficulties in satisfying the continuity conditions at the apexes are circumvented by mapping the eigenmodes for a spherical shell into the variable representing position along the meridian of the shape generator. The structural dynamic equations are coupled to the SVP equations by matching the normal velocity in the fluid to the time derivative of the normal displacement, as well as using the series expansion for surface pressure to form the contribution of the pressure to the generalized forces. Results for a spherical shell subjected to a trans erse point force at the equator, which is a nonaxisymmetric representation of the excitation, are compared with analytic results. Predictions for a hemi-capped cylindrical shell are compared to those obtained from SARA-2D (Allik, 1991), which is a finite/infinite element program. In addition to providing validation of the SVP implementation, each set of results is used to illustrate the convergence and error measures provided by an SVP analysis.
Incorporating Compressional and Shear Wave Types Into Fuzzy Structure Models for Plates
Authors: Rochat Judith L. , Sparrow Victor W. 
Published: March 2021

Abstract
Although realistic complex structures are usually difficult to model theoretically, fuzzy structure theory enables one to produce such a model without a detailed knowledge of the entire structure. Using the theory established by Pierce et al. [A. D. Pierce, V. W. Sparrow, and D. A. Russell, J. Vib. Acoust. (to be published), also ASME 93-WA/NCA-17.] regarding fundamental structural-acoustic idealizations for structures with imprecisely known or fuzzy internals, the effects that fuzzy attachments have on different wave types in a primary (or master) structure are examined in this paper. In the theory by Pierce et al., the primary structure that undergoes vibrations is a thin plate mounted in an infinite baffle. On one side of the plate are fuzzy attachments, represented as an array of attached mass-spring-dashpot systems, which are excited by an incident plane pulse. This known theory explains the effects of these attachments on bending waves in the plate. In this paper, the theory is extended to isolated compressional and shear waves in a plate. While studying this new problem, it is discovered that coupling effects occur when the plate and attachment properties are not uniform in the direction perpendicular to the wave propagation. Hence, unlike the bending wave theory which models a finite thin plate with point attached oscillators, the new wave type theory uses a thin plate infinite in one direction with line attached oscillators also infinite in the same direction. For both the compressional and shear waves, it is found that the fuzzy attachments add an apparent frequency dependent mass and damping to the plate. These results are similar to those for the bending wave theory.
Signature Features in Returned Echoes From Submerged Targets Insonified by Short, Broadband Pulses: Comparison of Experiments and Theory
Authors: Ståhlsten Torbjörn , Strifors Hans C. , Gaunaurd Guillermo C. 
Published: March 2021

Abstract
Backscattered echoes are studied from submerged elastic targets in the frequency domain and combined time-frequency domain when the targets are insonified by short, broadband sound pulses. The targets are either an air-filled spherical shell or various solid brass or steel spheres. The incident waveform is generated by weighting a sinusoidal signal with a Blackman time-window of a few cycles width. The spectrum is computed from each recorded set of experimental data and the result is shown to agree well with the theoretical prediction for the corresponding target and interrogating waveform. An advantage of the time-frequency approach is that target signatures can show the time evolution of the resonance features that identify each target. Experimentally obtained data are processed in the time-frequency domain using a pseudo-Wigner distribution (PWD). The associated time-window is Gaussian, and its width is adjusted to suppress the interference of cross-terms in the PWD, yet retaining the desired property of time-frequency concentrating the extracted features.
Recent Developments in Numerical Modeling of Transduction Materials
Authors: Hladky-Hennion Anne-Christine , Bossut Régis , Debus Jean-Claude 
Published: March 2021

Abstract
Recent research work in sonar system performance, coupled with achievements in the field of acoustic quieting, has led to the development of new ceramics that are promising for both hydrophone and projector applications. Other materials have also been studied like piezoelectric composite materials, magnetostrictive and electrostrictive materials. To design transducers using these materials, the finite element method seems to be the best suited approach. Using this method, it is possible to analyze, characterize and tailor new materials as well as to design a full transducer or an array. Recent developments in the ATILA finite element code allow the modeling of new transduction materials. The aim of this paper is to present the theoretical formulation in numerical modeling of materials used either for hydrophone or active sonar applications.
Investigation of an OHC Valve Train With Respect to Sound Quality
Authors: Suh In-Soo , Debost Sophie 
Published: March 2021

Abstract
Although the vibration generated by high speed dynamic movement of a valve train (VT) in an overhead camshaft SI engine is not a major source of engine noise, it still affects the overall sound quality of the engine, which is important to the subjective response of the customer.
The purpose of this research is to determine the specific mechanism of the valve train dynamic behavior, which is responsible for noise generation, and the vibration transmission characteristic to engine surfaces. Dynamic simulation with a lumped mass model is developed to analyze the dynamic behavior of VT during operation, and reveal the resonance frequencies of VT modeshapes excited by the cam harmonics. Also, experimental measurements of the valve acceleration, transfer functions of vibration, and the structural response have been performed in the valve train rig.
Based on the spectral analysis, two distinct noise generating mechanisms are determined. Vibration from VT components’ interaction, which is mainly excited by the harmonics of the cam profile during valve opening period, is dominant in the frequency range less than 6 kHz. On the other hand, valve seating is the dominant source in the frequency range from 6 kHz to 20 kHz. The more vibration energy from these two sources is transmitted through the structure via the VT system, rather than directly via the valve seat to the surfaces where sound is radiated, especially around the frequency of 5 kHz and 11 kHz. This fundamental investigation on the vibration sources and its transmission characteristics provides a new insight on the VT noise, which is an essential step toward the design of an engine with better sound quality.
Experimental Study for Extraction of Normal Modes
Authors: Chen S. Y. , Ju M. S. , Tsuei Y. G. 
Published: March 2021

Abstract
A frequency-domain technique to extract the normal mode from the measurement data for highly coupled structures is developed. The relation between the complex frequency response functions and the normal frequency response functions is derived. An algorithm is developed to calculate the normal modes from the complex frequency response functions. In this algorithm, only the magnitude and phase data at the undamped natural frequencies are utilized to extract the normal mode shapes. In addition, the developed technique is independent of the damping types. It is only dependent on the model of analysis. Two experimental examples are employed to illustrate the applicability of the technique. The effects due to different measurement locations are addressed. The results indicate that this technique can successfully extract the normal modes from the noisy frequency response functions of a highly coupled incomplete system.
Vibroacoustical Analysis of Flow in Pipes
Authors: Charley J. , Carta F. , Caignaert G. 
Published: March 2021

Abstract
This paper is concerned with the study of pressure and flow rate fluctuations propagation within ducts. A new transfer matrix model for a pipe taking into account the fluid-structure interactions effects is presented and compared to other formulations; significant gains have been realized. An extension of acoustic intensity technique using four transducers is presented.
Modal Analysis Method for Determination of Elastic Constants
Authors: Marchand V. , Pouyet J. 
Published: March 2021

Abstract
The purpose of this paper is to present an original means to determine materials elastic constants using a free vibration method. This experimental device enables us to obtain the natural frequencies of a free circular plate subject to heating at temperatures ranging from 20 to 1000 °C. The vibrations of the sample are recorded by a microphone. The identification of experimental natural frequencies is obtained by comparison with frequency spectrum resulting from two experimental means. A grid method consists in determining the elastic constants of the materials by comparing the experimental frequency with the frequencies calculated analytically using Ritz method.
Calculation of Component Mode Synthesis Matrices From Measured Frequency Response Functions
Authors: Morgan Jeffrey A. , Pierre Christophe , Hulbert Gregory M. 
Published: March 2021

Abstract
This paper shows how to calculate Craig-Bampton component mode synthesis matrices from measured frequency response functions. The procedure is based on a modified residual flexibility method and the use of a Maclaurin series expansion to represent the residual effects of the omitted modes. It was developed as a base-band method for structures exhibiting normal modes of vibration determined from free boundary vibration tests. Of particular importance is the procedure developed for the estimation of the Maclaurin series expansion coefficients and for the recovery of the Craig-Bampton matrices from the residual flexibility formulation. This allows accurate dynamic models to be determined for measured systems that can be used to predict the effects of structural modifications and in substructure coupling analyses. The performance of the new method is demonstrated by comparison of experiment and analysis for two simple beams.
Modal Testing and Parameter Identification of Active Magnetic Bearing System
Authors: Lee Chong-Won , Ha Young-Ho , Kim Cheol-Soon , Joh Chee-Young 
Published: March 2021

Abstract
Complex modal testing is employed for parameter identification of a four-axis active magnetic bearing system. In the test, magnetic bearings are used as exciters while the system is in operation. The experimental results show that the directional frequency response function, which is properly defined in the complex domain, is a powerful tool for identification of bearing as well as modal parameters.
Adaptive Synchronization Control Design for High-Speed Magnetic Bearings
Authors: Yang Li-Farn , Tsao Jeen-Gwo 
Published: March 2021

Abstract
The performance of actively controlled magnetic bearings is greatly degraded if subjected to unpredictable disturbances or system dynamic variations. This paper present an adaptive synchronization control on a magnetically suspended rotor system for disturbance rejection and plant variation compensation. The rotor system consists of a rotating disk mounted on a shaft which is actively positioned in the radial directions via two magnetic bearings at both ends. Under the synchronizing control, four displacements of shaft along bearing axes are coordinated such that the disturbed displacement can promptly be recovered with those undisturbed in a complementary way. Such motion synchronization requires strict regulation and adaptation through four local controllers with an adaptive feedforward control scheme. The local controllers can be linked by the coupling law, in which an error along one bearing axis can affect overall control loop of four axes. Two control algorithms are developed under the biaxial and quadaxial synchronization conditions, and their adaptation laws are optimized in an attempt to minimize the adaptation errors. Simulations of disturbance rejection responses will also be presented.
Experimental Modal Analysis of Rotating Disk Systems
Authors: Irretier Horst , Reuter Frank 
Published: March 2021

Abstract
A completely non-contact testing technique is presented to perform experimental modal analysis on rotating disk systems to identify modal parameters as eigenfrequencies, modal damping ratios and mode shapes due to rotation. Theoretical frequency response functions of rotating structures are presented which form the basis of the modal analysis. Experimental results of a rotating circular disk and a rotating radial impeller are presented and the influence of rotation on the modal parameters due to centrifugal, gyroscopic and aerodynamic effects is shown.
Development of an Electromagnetic Impactor for Structures With Large Rigid Body Motions
Authors: Wassermann J. , Mokesch H. , Springer H. 
Published: March 2021

Abstract
A PC-controlled electromagnetic impactor (PCC-EMI) is developed that can be used for broad band excitation of rotating structures from a stationary system. Begin, magnitude and position of the force impact exerted to the moving structure are automatically and precisely controlled by a personal computer through a new electronic circuit device. Bouncing effects of the hammer tip are electronically suppressed and an impact can be aimed to any desired point on the rotating structure with high accuracy and high repeatability. Experiments are carried out to test the positioning and repeatability capabilities of the system. Common frequency response functions are measured for a rotating disk and natural bending frequencies are experimentally determined in terms of the speed of rotation of the disk.
A New Methodology for the Accurate and Consistent Identification of Modal Parameters Using Multi-FRF Analysis
Authors: Lin R. M. , Ling S.-F. 
Published: March 2021

Abstract
A new method for the estimation of modal parameters is presented in this paper. Unlike the majority of the existing methods which involve complicated curve fitting and interpolative procedures, the proposed method calculates the modal parameters by solving eigenvalue problem of an equivalent eigensystem derived from measured frequency response function (FRF) data. It is developed based on the practical assumption that only one incomplete column of the FRF matrix of the test structure has been measured in a frequency range of interest. All the measured FRFs are used simultaneously to construct the equivalent eigensystem matrices from which natural frequencies, damping loss factor and modeshape vectors of interest can be directly solved. Since the identification problem is reduced to an eigenvalue problem of an equivalent system, natural frequencies and damping loss factors identified are consistent. Further procedures for normalizing the identified eigenvectors so that they become mass-normalized are developed. Numerical case examples are given to demonstrate the practicality of the proposed method and results obtained are indeed very promising. It is believed that with the availability of such identification method, modal analysts’ dream of intelligent and full automatic modal analysis will become a reality.
A Generalized Treatment of the Energetics of Translating Continua
Authors: Lee Seung-Yop , Mote C. D. 
Published: March 2021

Abstract
The energetics of translating, one-dimensional continua, like uniform strings or tensioned beams, that travel between two supports is analyzed in this paper. The non-conservative interaction between the supports and the translating continua causes energy flux at the boundaries. The total mechanical energy is not conserved, and a periodic transfer of energy into and out of the system occurs. From the power flows in traveling waves, the energy flux for a string translating through fixed, free, elastic and viscous damping boundary conditions is obtained explicitly in terms of the transport speed and the ratio of the reflected to incident amplitudes. The time-dependent character of the total energy of a translating tensioned beam is complex because the beam is dispersive. The energy variation in the beam is represented in terms of the mechanical impedance and the amplitude ratio between the reflected and incident propagating waves. At low frequency, frequency-dependent energy ratios are identical to those of translating strings. The amount of energy flux at boundaries decreases with frequency, and increases with transport speed. Numerical simulations verify the analytically predicted energy variations for the different supports.
Vibration Analysis of Mindlin Plates by the Superposition-Galerkin Method
Authors: Gorman D. J. , Ding Wei 
Published: March 2021

Abstract
In the first part of this paper, it is demonstrated how the superposition of four judiciously selected forced vibration solutions to rectangular mindlin plate vibration problems permits the obtaining of an eigenvalue matrix from which the resonant frequencies of fully clamped mindlin plates can be extracted. Subsequently, it is shown how the same forced vibration solutions can be obtained much more efficiently by the Galerkin Method. After superposition of the latter solutions, it is shown how the same resonant frequencies are obtained. The vast advantages of exploiting this latter “Superposition-Galerkin” method are enumerated and discussed in detail.
On the Formulation and Solution of a Class of Magneto-Viscoelasto-Dynamics (MVD) Governing Equations of Motion
Authors: Wong Po Kee , Wong Adam , Wong Anita 
Published: March 2021

Abstract
The paper is to provide the formulation and solution of a class of linear viscoelastic, isotropic, homogeneous, three-dimensional, magnetic conducting materials’ governing displacement equations of motion by means of the spectral operator theory in order to find the answers for the perplexing phenomena of plasma instabilities in those materials.
Dynamic Response of Soil Under S.H.P.B. Loading
Authors: Semblat J. F. , Gary G. , Luong M. P. 
Published: March 2021

Abstract
Soil dynamic response has been little investigated under fast loading conditions. Split Hopkinson Pressure Bar method leads to the determination of dynamic behaviour of various materials. A special experimental device called three-dimensional S.H.P.B provides dynamic response of soil specimens in both axial and radial directions (oedometric tests). Comparisons with other loading paths (mean and deviatoric stresses) give usefull elements on granular soil behaviour under high strain rates. The results are also analysed at grain-size scale (grain-size distribution, fracture energy). Experimental results show that 3D-Split Hopkinson Pressure Bar is a promising tool for laboratory dynamic testing on soils.
Modal Loss Factors of Thick Three-Layer Cylinders With Viscoelastic Core
Authors: Hamidzadeh Hamid R. , Jiang Yanfei 
Published: March 2021

Abstract
An analytical solution to the free vibration of a damped three-layer thick sandwiched cylinder of infinite extend is presented. The constrained layer damping is accomplished by sandwiching a linear viscoelastic material between two isotropic elastic cylinders with the same properties. The governing equation is derived based on elasto-dynamic theory utilizing complex elastic moduli. Dimensionless natural frequencies and modal loss-factors are extracted.
Special case for a three-layer sandwiched cylinder with similar elastic properties is considered. The computed dimensionless frequencies are compared with previously established results. The comparison indicates the validity of the proposed mathematical procedures. In addition, the effects of various values of material damping for the core layer and ratio of the core shear modulus to the shear modulus of the elastic cylinders on natural frequencies and modal loss-factors are studied. For a given configuration, modal information for the first two modes for n = 0, 1, 2, 3 and 4 are presented for a wide range of core material damping and G2/G1 ratio.
Transient Vibration Reduction Through the Use of Dual Absorbers
Authors: Bursal Faruk H. 
Published: March 2021

Abstract
The dual absorber configuration is shown to exhibit considerable improvements with respect to transient vibration over the conventional, single-absorber design for the same amount of total absorber mass. The term transient as used in this paper refers to monotonic changes in frequency during the start-up and shut-down of rotating machinery. The use of the frequency response as a design tool for this kind of transient is motivated by a quasi-staticity argument, which presumes the change in the operating frequency to be slow relative to the natural period of the oscillations. New tuning rules for dual absorbers are presented that yield near-optimal levels of transient vibration reduction along with significant steady-state attenuation. The improvements obtainable by using dual absorbers become more pronounced when the system changes its speed of rotation more slowly. The dual absorber design appears to exhibit the best overall vibration reduction characteristics among all passive absorbers tested and can also be installed retroactively onto an existing absorber setup. Because the design shares the simplicity of construction and maintenance of other passive absorbers, it is believed to be an excellent alternative to more complicated active or semi-active absorbers in many situations.
System Identification of Torsionally-Coupled Structures
Authors: Lin Chi-Chang , Ueng Jin-Min , Lin Pao-Lung 
Published: March 2021

Abstract
In this paper, the Ibrahim Time Domain technique is employed to calculate the modal frequencies and damping ratios of torsionally-coupled buildings based only on partial free vibration response measurements. To obtain the complete mode shapes, an interpolation method is developed to calculate the mode shape value for the locations without measurement. All mode shapes obtained are mutually orthogonal. The structural seismic responses are also estimated. Numerical results show that the proposed method is able to identify structural dominant modal parameters accurately even with highly coupled modes and noise contaminations. Small number of response measurements (no need of input measurement) and simple on-line calculation make the proposed method favorable to real implementation.