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Title

EXPERIMENTAL DETERMINATION OF NATURAL FREQUENCIES AND LOSS FACTORS OF A CLAMPED RECTANGULAR PLATE WITH PARTIAL CONSTRAINED LAYER DAMPING TREATMENTS.

Creator

BHAT, RAJENDRA AGHUT., Florida Atlantic University, Stevens, Karl K.

Abstract/Description

An experimental investigation to determine the effectiveness of partial constrained layer damping treatments for a clamped rectangular plate is described. The impulse testing technique was used with a Hewlett Packard '5423A structural Dynamics Analyzer' to determine modal parameters of the first five flexural modes. The results obtained are compared with theoretical results and they are in agreement. The results indicate that partial constrained layer damping treatments, if properly used, can...
Show moreAn experimental investigation to determine the effectiveness of partial constrained layer damping treatments for a clamped rectangular plate is described. The impulse testing technique was used with a Hewlett Packard '5423A structural Dynamics Analyzer' to determine modal parameters of the first five flexural modes. The results obtained are compared with theoretical results and they are in agreement. The results indicate that partial constrained layer damping treatments, if properly used, can be more effective than complete treatments.
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Date Issued

1983

PURL

http://purl.flvc.org/fcla/dt/14188

Subject Headings

Plates (Engineering)Vibration, Damping (Mechanics)

Format

Document (PDF)


Title

Dynamic stall and threedimensional wake effects on trim, stability and loads of hingeless rotors with fast Floquet theory.

Creator

Chunduru, Srinivas Jaya., Florida Atlantic University, Gaonkar, Gopal H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

This dissertation investigates the effects of dynamic stall and threedimensional wake on isolatedrotor trim, stability and loads. Trim analysis of predicting the pilot's control inputs and the corresponding periodic responses is based on periodic shooting with the fast Floquet theory and damped Newton iteration. Stability analysis, also based on the fast Floquet theory, predicts damping levels and frequencies. Loads analysis uses a forceintegration approach to predict the rotatingblade...
Show moreThis dissertation investigates the effects of dynamic stall and threedimensional wake on isolatedrotor trim, stability and loads. Trim analysis of predicting the pilot's control inputs and the corresponding periodic responses is based on periodic shooting with the fast Floquet theory and damped Newton iteration. Stability analysis, also based on the fast Floquet theory, predicts damping levels and frequencies. Loads analysis uses a forceintegration approach to predict the rotatingblade root shears and moments as well as the hub forces and moments. The blades have flap bending, lag bending and torsion degrees of freedom. Dynamic stall is represented by the ONERA stall models of lift, drag and pitching moment, and the unsteady, nonuniform downwash is represented by a threedimensional, finitestate wake model. Throughout, full bladestallwake dynamics is used in that all states are included from trim to stability to loads predictions. Moreover, these predictions are based on four aerodynamic theoriesquasisteady linear theory, quasisteady stall theory, dynamic stall theory and dynamic stall and wake theoryand cover a broad range of system parameters such as thrust level, advance ratio, number of blades and blade torsional frequency. The investigation is conducted in three phases. In phase one, the elastic flaplagtorsion equations are coupled with a finitestate wake model and with linear quasisteady airfoil aerodynamics. The investigation presents convergence characteristics of trim and stability with respect to the number of spatial azimuthal harmonics and radial shape functions in the wake representation. It includes a comprehensive parametric study over a broad range of system parameters. The investigation also includes correlation with the measured lagdamping data of a threebladed isolated rotor operated untrimmed. In the correlation, three structural models of the rootflexureblade assembly are used to demonstrate the strengths and the weaknesses of lagdamping predictions. Phase two includes dynamic stall in addition to threedimensional wake to generate trim and stability results over a comprehensive range of system parameters. It addresses the degree of sophistication necessary in blade discretization and wake representation under dynamically stalled conditions. The convergence and parametric studies isolate the effects of wake, quasisteady stall and dynamic stall on trim and stability. Finally, phase three predicts the rotating blade loads and nonrotating hub loads; the predictions are based on the blade, wake and stall models used in the preceding trim and stability investigations. Although an accurate evaluation of loads requires a more refined blade description, the results isolate and demonstrate the principal dynamic stall and wake effects on the loads.
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Date Issued

1995

PURL

http://purl.flvc.org/fcla/dt/12426

Subject Headings

Floquet theory, Helicopters, Rotors (Helicopters), Vibration (Aeronautics)

Format

Document (PDF)


Title

AN INVESTIGATION OF ENERGY FLOW AND ACOUSTIC RADIATION OF FLUIDLOADED PANELS USING THE ENERGY ACCOUNTANCY CONCEPT.

Creator

MAILLET, PHILIPPE LOUIS., Florida Atlantic University, Dunn, Stanley E., Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

The energy flow and the acoustic radiation of fluidloaded panels are investigated using the Energy Accountancy Concept. The various energy components of the systems are defined and studied. Each component is a function of the excitation, the structure, the medium and their coupling. An energy balance equation is written for the system. This method is applied to study the acoustic radiation from a pointexcited clamped plate placed on the free surface of a water tank. The radiation efficiency...
Show moreThe energy flow and the acoustic radiation of fluidloaded panels are investigated using the Energy Accountancy Concept. The various energy components of the systems are defined and studied. Each component is a function of the excitation, the structure, the medium and their coupling. An energy balance equation is written for the system. This method is applied to study the acoustic radiation from a pointexcited clamped plate placed on the free surface of a water tank. The radiation efficiency of the plate is measured and compared to previous works. The energy balance equation gives very good results at frequencies between 50 Hz and 12 kHz. An undefined source of energy dissipation is observed in one experiment. The results of this study have shown that the Energy Accountancy Concept can be used to describe the energy flow in a vibrating structure under waterloading.
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Date Issued

1986

PURL

http://purl.flvc.org/fcla/dt/14289

Subject Headings

Acoustic radiation pressure, VibrationMeasurement

Format

Document (PDF)


Title

Power flow analysis of a structure subjected to distributed excitation.

Creator

Cimerman, Benjamin Pierre., Florida Atlantic University, Cuschieri, Joseph M.

Abstract/Description

An analytical investigation based on the Power Flow Method is presented for the prediction of vibrational Power Flow in simple connected structures subjected to various forms of distributed excitations. The principle of the power flow method consists of dividing the global structure into a series of substructures which can be analyzed independently and then coupled through the boundary conditions. Power flow expressions are derived for an Lshaped plate structure, subjected to any form of...
Show moreAn analytical investigation based on the Power Flow Method is presented for the prediction of vibrational Power Flow in simple connected structures subjected to various forms of distributed excitations. The principle of the power flow method consists of dividing the global structure into a series of substructures which can be analyzed independently and then coupled through the boundary conditions. Power flow expressions are derived for an Lshaped plate structure, subjected to any form of distributed mechanical excitation or excited by an acoustic plane wave. In the latter case air loading is considered to have a significant effect on the power input to the structure. Fluidstructure interaction considerations lead to the derivation of a corrected mode shape for the normal velocity, and the determination of the scattered pressure components in the expressions for the Power Flow.
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Date Issued

1990

PURL

http://purl.flvc.org/fcla/dt/14578

Subject Headings

Structural dynamics, Plates (Engineering)Vibration

Format

Document (PDF)


Title

Vibrational analysis of a journal bearing.

Creator

Journeau, Franck Daniel., Florida Atlantic University, Cuschieri, Joseph M.

Abstract/Description

A Statistical Energy Analysis (SEA) approach is used to investigate the vibrational behavior of a journal bearing. In developing the SEA model, consideration is given to the determination of coupling loss factors between nonconservatively coupled substructures. In the case of the journal bearing, the oil film between the rotating shaft and the bearing liner represents nonconservative coupling. The coupling loss factors are estimated using experimentally measured point mobility functions....
Show moreA Statistical Energy Analysis (SEA) approach is used to investigate the vibrational behavior of a journal bearing. In developing the SEA model, consideration is given to the determination of coupling loss factors between nonconservatively coupled substructures. In the case of the journal bearing, the oil film between the rotating shaft and the bearing liner represents nonconservative coupling. The coupling loss factors are estimated using experimentally measured point mobility functions. The internal loss factors are directly measured with the bearing structure disassembled. Additionally, estimates for the coupling and internal loss factors are obtained insitu using an energy ratio approach. Using the determined coupling and internal loss factors in an SEA model, estimates for the average mean square velocities on the surface of the bearing subcomponents are obtained for both static and dynamics conditions. The SEA estimates match well with directly measured results for the spatial average surface velocities at medium to high frequencies.
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Date Issued

1992

PURL

http://purl.flvc.org/fcla/dt/14786

Subject Headings

Journal bearings, MachineryNoise, Couplings, Vibration

Format

Document (PDF)


Title

An experimental study of the response of circular plates subjected to fluid loading.

Creator

Coulson, Robert Kenneth., Florida Atlantic University, Glegg, Stewart A. L.

Abstract/Description

The interaction between vibrating structures and fluids can have a profound influence upon the natural frequencies of the structure's vibration. This study examines one specific structure; a thin circular plate with the rarely studied free edge condition. It starts by considering a completely free plate in a vacuum and then, using receptance matching, utilises this result to determine the effects, on the natural frequencies, of a centrally located driving rod. Then, using the same technique,...
Show moreThe interaction between vibrating structures and fluids can have a profound influence upon the natural frequencies of the structure's vibration. This study examines one specific structure; a thin circular plate with the rarely studied free edge condition. It starts by considering a completely free plate in a vacuum and then, using receptance matching, utilises this result to determine the effects, on the natural frequencies, of a centrally located driving rod. Then, using the same technique, a result for the drive admittance of the fluid loaded plate is adapted to predict the natural frequencies of the same structure when subjected to significant fluid loading. All these results are then compared to those obtained from experiments.
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Date Issued

1990

PURL

http://purl.flvc.org/fcla/dt/14605

Subject Headings

Plates (Engineering)Vibration, Acoustical engineering

Format

Document (PDF)


Title

Free and random vibrations of shells of revolution with interior supports.

Creator

Xia, Zhiyong., Florida Atlantic University, Yong, Yan, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

A new analytical method based on the wave propagation scheme has been developed for the dynamic analysis of axially symmetric shells with arbitrary boundary conditions and interior supports. In this approach, a shell structure is considered as a waveguide and the response to external excitations is treated as a superposition of wave motions. To segregate the effect of the interior supports, the waveguide is first divided into several subwaveguides. Upon analyzing these subwaveguides...
Show moreA new analytical method based on the wave propagation scheme has been developed for the dynamic analysis of axially symmetric shells with arbitrary boundary conditions and interior supports. In this approach, a shell structure is considered as a waveguide and the response to external excitations is treated as a superposition of wave motions. To segregate the effect of the interior supports, the waveguide is first divided into several subwaveguides. Upon analyzing these subwaveguides separately, a composition scheme is adopted to relate them by connecting the wave components according to the continuity conditions for the state variables at each interior supports. Closed form solutions for free and random vibration are derived. The proposed method is presented in a general fashion and numerical examples are given to illustrate the application of the theory.
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Date Issued

1990

PURL

http://purl.flvc.org/fcla/dt/14659

Subject Headings

Shells (Engineering)Vibration, Wave guides

Format

Document (PDF)


Title

A METHOD OF ANALYSIS FOR EVALUATING THE EFFECTIVENESS OF PARTIAL DAMPING LAYER TREATMENTS FOR SQUARE PLATES.

Creator

KUNG, CHUNHUA., Florida Atlantic University, Stevens, Karl K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

An energy method for predicting the natural frequency and loss factor for square plates with partial and complete coatings is developed. Both simplysupported and edgefixed bonndary conditions are considered. An impulse testing technique is used to provide an experimental verification of the analysis for the case of an edgefixed square plate. The analytical and experimental results are in close agreement, and indicate that partial coatings can provide effective damping treatments.

Date Issued

1981

PURL

http://purl.flvc.org/fcla/dt/14045

Subject Headings

Plates (Engineering)Vibration, Damping (Mechanics)

Format

Document (PDF)


Title

The vacuum ultraviolet magnetic circular dichroism of propylene: Elucidation of the electronic structure of propylene.

Creator

Atanasova, Sylvia T., Florida Atlantic University, Snyder, Patricia Ann

Abstract/Description

The purpose of this research is to investigate the electronic structure of propylene. The vacuumultraviolet absorption and magnetic circular dichroism (MCD) spectra of propylene were obtained by Professor Snyder at the National Synchrotron Radiation Center. The absorption and MCD spectra are presented in the region 52 00077 000 cm1. The spectra were examined in detail in the pi → pi* region from 52 000 cm1 to 58766 cm1. The MCD provides unique information about the electronic structure...
Show moreThe purpose of this research is to investigate the electronic structure of propylene. The vacuumultraviolet absorption and magnetic circular dichroism (MCD) spectra of propylene were obtained by Professor Snyder at the National Synchrotron Radiation Center. The absorption and MCD spectra are presented in the region 52 00077 000 cm1. The spectra were examined in detail in the pi → pi* region from 52 000 cm1 to 58766 cm1. The MCD provides unique information about the electronic structure of a molecule. The MCD spectrum clearly showed that there are at least three electronic transitions in the pi → pi* region of the propylene spectrum. The presently proposed assignments for these transitions are pi → 3s, pi → pi*, and pi → 3p. The first step in the vibrational analysis, which may aid in the assignments of the electronic transitions, was carried out. A theoretical calculation of the normal vibrational modes of ethylene and propylene has been done using Hyperchem software.
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Date Issued

2002

PURL

http://purl.flvc.org/fcla/dt/12875

Subject Headings

Magnetic circular dichroism, Propene, Vibrational spectra

Format

Document (PDF)


Title

Deterministic, stochastic and convex analyses of one and twodimensional periodic structures.

Creator

Zhu, Liping., Florida Atlantic University, Lin, Y. K., Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

The periodic structures considered in the dissertation are onedimensional periodic multispan beams, and twodimensional periodic grillages with elastic interior supports. The following specific topics are included: (1) Deterministic VibrationExact solutions are obtained for free vibrations of both multispan beams and grillages, by utilizing the wave propagation concept. The wave motions at the periodic supports/nodes are investigated and the dispersion equations are derived from which...
Show moreThe periodic structures considered in the dissertation are onedimensional periodic multispan beams, and twodimensional periodic grillages with elastic interior supports. The following specific topics are included: (1) Deterministic VibrationExact solutions are obtained for free vibrations of both multispan beams and grillages, by utilizing the wave propagation concept. The wave motions at the periodic supports/nodes are investigated and the dispersion equations are derived from which the natural frequencies of the periodic structures are determined. The emphasis is placed on the calculation of mode shapes of both types of periodic structures. The general expressions for mode shapes with various boundary conditions are obtained. These mode shapes are used to evaluate the exact dynamic response to a convected harmonic loading. (2) Stochastic VibrationA multispan beam under stochastic acoustic loading is considered. The exact analytical expressions for the spectral densities are derived for both displacement and bending moment by using the normal mode approach. Nonlinear vibration of a multispan beam with axial restraint and initial imperfection are also investigated. In the latter case, the external excitation is idealized as a Gaussian white nose. An expression for the joint probability density function in the generalized coordinates is obtained and used to evaluate the mean square response of a multispan beam system. (3) Convex Modeling of Uncertain Excitation FieldIt is assumed that the parameters of the stochastic excitation field are uncertain and belong to a multidimensional convex set. A new approach is developed to determine the multidimensional ellipsoidal convex set with a minimum volume. The most and least favorable responses of a multispan beam are then determined for such a convex set, corresponding to a stochastic acoustic field. The procedure is illustrated in several examples.
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Date Issued

1994

PURL

http://purl.flvc.org/fcla/dt/12366

Subject Headings

Grillages (Structural engineering), GirdersVibration, Wavemotion, Theory of, Vibration

Format

Document (PDF)


Title

Mobility power flow (MPF) approach applied to fluidloaded shells with ring discontinuities.

Creator

McCain, Thomas Scott., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

The vibrational and acoustic characteristics of fluidloaded, cylindrical shells with single or multiple, aperiodicallyspaced ring discontinuities are studied using an approach based on the mobility power flow (MPF) method and a hybrid numerical/analytical method for the evaluation of the velocity Green's function of the shell. The discontinuities are associated with internal structures coupled to the shell via ring junctions. The approach is a framework allowing alternative shell and/or...
Show moreThe vibrational and acoustic characteristics of fluidloaded, cylindrical shells with single or multiple, aperiodicallyspaced ring discontinuities are studied using an approach based on the mobility power flow (MPF) method and a hybrid numerical/analytical method for the evaluation of the velocity Green's function of the shell. The discontinuities are associated with internal structures coupled to the shell via ring junctions. The approach is a framework allowing alternative shell and/or internal structure models to be used. The solution consists of the net vibrational power flow between the shell and internal structure(s) at the junction(s), the shell's velocity Green's function, and the farfield acoustic pressure. Use of the MPF method is advantageous because the net power flow solution can be used as a diagnostic tool in ascertaining the proper coupling between the shell and internal structure(s) at the junction(s). Results are presented for two canonical problems: an infinite, thin cylindrical shell, externally fluidloaded by a heavy fluid, coupled internally to: (1) a single damped circular plate bulkhead, and (2) a double bulkhead consisting of two identical damped circular plates spaced a shell diameter apart. Two excitation mechanisms are considered for each model: (1) insonification of the shell by an obliquelyincident, acoustic plane wave, and (2) a radial ring load applied to the shell away from the junction(s). The shell's radial velocity Green's function and farfield acoustic pressure results are presented and analyzed to study the behavior of each model. In addition, a comparison of these results accentuates the qualitative difference in the behavior between the single and multiple junction models. When multiple internal structures are present, the results are strongly influenced by interjunction coupling communicated through the shell and the fluid. Results are presented for circumferential modes n = 0 & 2. The qualitative differences in the results for modes n = 0 and n = 2 (indicative of all modes n > 0ified in the farfield acoustic pressure and velocity Green's function response with the characteristics of the shell and internal plate bulkhead. The results for the single junction model demonstrate the significance of the shell's membrane waves on the reradiation of acoustic energy from the shell; however, when multiple junctions are present, interjunction coupling results in a significant broad acoustic scattering pattern. Using the results and analysis presented here, a better understanding can be obtained of fluidloaded shells, which can be used to reduce the strength of the acoustic pressure field produced by the shell.
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Date Issued

1996

PURL

http://purl.flvc.org/fcla/dt/12490

Subject Headings

Shells (Engineering)Vibration, CylindersVibration, Fluid dynamics, SoundTransmission

Format

Document (PDF)


Title

A perturbation method for the vibration analysis of beams and plates with freelayer damping treatments.

Creator

Shen, Sueming, Florida Atlantic University, Stevens, Karl K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

The feasibility of using structural modification techniques to determine the effect of added viscoelastic damping treatments on the modal properties of a distinct eigenvalue system and a degenerate system is investigated. Linear perturbation equations for the changes introduced into the system eigenproperties are derived and applied to several examples involving the flexural vibration of beams and square plates with varying degrees of damping treatment. Both large and small perturbations are...
Show moreThe feasibility of using structural modification techniques to determine the effect of added viscoelastic damping treatments on the modal properties of a distinct eigenvalue system and a degenerate system is investigated. Linear perturbation equations for the changes introduced into the system eigenproperties are derived and applied to several examples involving the flexural vibration of beams and square plates with varying degrees of damping treatment. Both large and small perturbations are considered. An FEM code has been developed to compute the dynamic system parameters which are subsequently used in an iterative method to determine the modal properties. The perturbation approach described can accommodate temperature and frequencydependent material properties, and the procedures involved are illustrated in the examples considered. Results obtained for these examples are compared with those available from closed form or finite element solutions, or from experiments. Excellent agreement of the results of the present method with those of other contemporary methods demonstrates the validity, overall accuracy, efficiency and convergence rate of this technique. The perturbation approach appears to be particularly well suited for systems with temperature and frequency dependent material properties, and for design situations where a number of damping configurations must be investigated.
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Date Issued

1989

PURL

http://purl.flvc.org/fcla/dt/12239

Subject Headings

GirdersVibration, Plates (Engineering)Vibration, Perturbation (Mathematics), Damping (Mechanics)

Format

Document (PDF)


Title

Detection, localization, and identification of bearings with raceway defect for a dynamometer using high frequency modal analysis of vibration across an array of accelerometers.

Creator

Waters, Nicholas., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

This thesis describes a method to detect, localize and identify a faulty bearing in a rotating machine using narrow band envelope analysis across an array of accelerometers. This technique is developed as part of the machine monitoring system of an ocean turbine. A rudimentary mathematical model is introduced to provide an understanding of the physics governing the vibrations caused by a bearing with a raceway defect. This method is then used to detect a faulty bearing in two setups : on a...
Show moreThis thesis describes a method to detect, localize and identify a faulty bearing in a rotating machine using narrow band envelope analysis across an array of accelerometers. This technique is developed as part of the machine monitoring system of an ocean turbine. A rudimentary mathematical model is introduced to provide an understanding of the physics governing the vibrations caused by a bearing with a raceway defect. This method is then used to detect a faulty bearing in two setups : on a lathe and in a dynamometer.
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Date Issued

2012

PURL

http://purl.flvc.org/FAU/3359156

Subject Headings

Marine turbines, Mathematical models, Vibration, Measurement, Fluid dynamics, Dynamic testing

Format

Document (PDF)


Title

Numerical models to simulate underwater turbine noise levels.

Creator

Lippert, Renee'., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

This work incorporates previous work done by Guerra and the application of fluid dynamics. The structure attached to the turbine will cause unsteady fluctuations in the flow, and ultimately affect the acoustic pressure. The work of Guerra is based on a lot of assumptions and simplifications to the geometry of the turbine and structure. This work takes the geometry of the actual turbine, and uses computational fluid dynamic software to numerically model the flow around the turbine structure....
Show moreThis work incorporates previous work done by Guerra and the application of fluid dynamics. The structure attached to the turbine will cause unsteady fluctuations in the flow, and ultimately affect the acoustic pressure. The work of Guerra is based on a lot of assumptions and simplifications to the geometry of the turbine and structure. This work takes the geometry of the actual turbine, and uses computational fluid dynamic software to numerically model the flow around the turbine structure. Varying the angle of the attack altered the results, and as the angle increased the noise levels along with the sound pulse, and unsteady loading increased. Increasing the number of blades and reducing the chord length both reduced the unsteady loading.
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Date Issued

2012

PURL

http://purl.flvc.org/FAU/3355622

Subject Headings

Underwater acoustics, Mathematical models, Turbines, Vibration, Mathematical models, Fluid dynamics

Format

Document (PDF)


Title

Design and implementation of an adaptive control system for active noise control.

Creator

Duprez, Adrien Eric., Florida Atlantic University, Cuschieri, Joseph M.

Abstract/Description

This thesis describes the design and implementation of an adaptive control system for active noise control. The main approaches available for implementing an active noise controller are presented and discussed. A Least Mean Squares (LMS) based algorithm, the FilteredX LMS (FXLMS) algorithm, is selected for implementation. The significance of factors, such as delays, system output noise, system complexity, type and size of adaptive filter, frequency bandwidth, etc..., which can limit the...
Show moreThis thesis describes the design and implementation of an adaptive control system for active noise control. The main approaches available for implementing an active noise controller are presented and discussed. A Least Mean Squares (LMS) based algorithm, the FilteredX LMS (FXLMS) algorithm, is selected for implementation. The significance of factors, such as delays, system output noise, system complexity, type and size of adaptive filter, frequency bandwidth, etc..., which can limit the performance of the adaptive control, is investigated in simulations. For hardware implementation, a floatingpoint DSP is selected to implement the adaptive controller. The control program and its implementation on the DSP are discussed. The program is first tested with a hardwareintheloop setup and then implemented on a physical system. Active Noise Control in a duct is finally successfully demonstrated. The hardware and the results are discussed.
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Date Issued

2001

PURL

http://purl.flvc.org/fcla/dt/12771

Subject Headings

Adaptive control systems, Active noise and vibration control

Format

Document (PDF)


Title

Dynamic response of plate structures to external excitations.

Creator

Mani, George., Florida Atlantic University, Yong, Yan, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

The dynamic response of plate structures composed of rigidly connected thin plates subjected to point loads is studied. The finite strip method combined with a new approach for analyzing periodic structures is utilized to obtain substantial reduction in computational efforts. Each strip with various boundary conditions is treated as a waveguide capable of transmitting different wave motions. Wave scattering matrices are defined to characterize wave motions at boundaries, intersection of...
Show moreThe dynamic response of plate structures composed of rigidly connected thin plates subjected to point loads is studied. The finite strip method combined with a new approach for analyzing periodic structures is utilized to obtain substantial reduction in computational efforts. Each strip with various boundary conditions is treated as a waveguide capable of transmitting different wave motions. Wave scattering matrices are defined to characterize wave motions at boundaries, intersection of plates and where type of wave guides are changed. The results obtained from the application of the approach on various plate configurations are presented and discussed.
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Date Issued

1990

PURL

http://purl.flvc.org/fcla/dt/14661

Subject Headings

Plates (Engineering)Vibration, Finite strip method, Structural analysis (Engineering)

Format

Document (PDF)


Title

Computeraided design of speed humps.

Creator

Joseph, Philip Puthooppallil., Florida Atlantic University, Wong, TinLup

Abstract/Description

A sixdegreeoffreedom model of a vehicle was simulated over different hump profiles with a computer program and the results were verified. The resulting vibration characteristics were analyzed to calculate a discomfort index. The discomfort index considered is the equivalent root mean square acceleration specified by the proposal for the revision of ISO 2631. A parametric study was conducted to find the sensitivity of different hump and vehicular parameters on the ride comfort. The optimal...
Show moreA sixdegreeoffreedom model of a vehicle was simulated over different hump profiles with a computer program and the results were verified. The resulting vibration characteristics were analyzed to calculate a discomfort index. The discomfort index considered is the equivalent root mean square acceleration specified by the proposal for the revision of ISO 2631. A parametric study was conducted to find the sensitivity of different hump and vehicular parameters on the ride comfort. The optimal hump parameters were obtained for different limiting speeds. Two field humps were simulated and modification of the humps is suggested for optimum performance.
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Date Issued

1993

PURL

http://purl.flvc.org/fcla/dt/14920

Subject Headings

Speed reducersData processing, Traffic engineering, AutomobilesVibration

Format

Document (PDF)


Title

Dynamic stability of fluidconveying pipes on uniform or nonuniform elastic foundations.

Creator

Vittori, Pablo J., Florida Atlantic University, Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

The dynamic behavior of straight cantilever pipes conveying fluid is studied, establishing the conditions of stability for systems, which are only limited to move in a 2Dplane. Internal friction of pipe and the effect of the surrounding fluid are neglected. A universal stability curve showing boundary between the stable and unstable behaviors is constructed by finding solution to equation of motion by exact and highdimensional approximate methods. Based on the BoobnovGalerkin method, the...
Show moreThe dynamic behavior of straight cantilever pipes conveying fluid is studied, establishing the conditions of stability for systems, which are only limited to move in a 2Dplane. Internal friction of pipe and the effect of the surrounding fluid are neglected. A universal stability curve showing boundary between the stable and unstable behaviors is constructed by finding solution to equation of motion by exact and highdimensional approximate methods. Based on the BoobnovGalerkin method, the critical velocities for the fluid are obtained by using both the eigenfunctions of a cantilever beam (beam functions), as well as the utilization of Duncan's functions. Stability of cantilever pipes with uniform and nonuniform elastic foundations of two types are considered and discussed. Special emphasis is placed on the investigation of the paradoxical behavior previously reported in the literature.
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Date Issued

2004

PURL

http://purl.flvc.org/fcla/dt/13167

Subject Headings

Strains and stresses, Structural dynamics, Structural stability, Fluid dynamics, Vibration

Format

Document (PDF)


Title

Impact analysis of a piezotransducervibrator.

Creator

Karabiyik, Necati., Florida Atlantic University, Tsai, ChiTay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

PiezoTransducerVibrators are miniature devices that emit both audio and silent signals and are currently targeted for use as an integral part of wristwatch technology. Utilizing nonlinear finite element analysis is essential for obtaining a greater understanding of the system response under varying conditions. Dyna3D nonlinear finite element code is applied in this analysis with the focus on the mechanical aspects of the vibrator. Four impact variables, the velocity, the plate gap, the...
Show morePiezoTransducerVibrators are miniature devices that emit both audio and silent signals and are currently targeted for use as an integral part of wristwatch technology. Utilizing nonlinear finite element analysis is essential for obtaining a greater understanding of the system response under varying conditions. Dyna3D nonlinear finite element code is applied in this analysis with the focus on the mechanical aspects of the vibrator. Four impact variables, the velocity, the plate gap, the weight and the velocity angle are studied to determine the effects on the system response. Each impact variable is assigned three separate values, creating twelve programs for analysis. For each program, responses to impact conditions are studied demonstrating the deformed mode shapes, maximum principal stresses and maximum displacements using state database plots and timehistory plots.
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Date Issued

1994

PURL

http://purl.flvc.org/fcla/dt/15008

Subject Headings

Piezoelectric transducers, Finite element method, Wrist watches, Vibrators

Format

Document (PDF)


Title

GALLOPING OF AN ELASTICALLY SUPPORTED BLUFF BODY IN TURBULENT FLOW.

Creator

Li, Qiang, Florida Atlantic University, Lin, Y. K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering

Abstract/Description

The phenomenon of flowinduced vibration is found in many engineering systems. The fluid flow generates forces on the structure that cause motion of the structure. In turn, the structural motion changes the angle of attack between the flow and the structure, hence the forces on the structure. Furthermore, turbulence generally exists in a natural fluid flow; namely, the fluid velocity contains a random part. Thus, the problem is formulated as a nonlinear system under random excitations. This...
Show moreThe phenomenon of flowinduced vibration is found in many engineering systems. The fluid flow generates forces on the structure that cause motion of the structure. In turn, the structural motion changes the angle of attack between the flow and the structure, hence the forces on the structure. Furthermore, turbulence generally exists in a natural fluid flow; namely, the fluid velocity contains a random part. Thus, the problem is formulated as a nonlinear system under random excitations. This thesis is focused on one type of motion known as galloping. A mathematical model for the motion of an elastically supported square cylinder in turbulent flow is developed. The physical nonlinear equation is converted to ideal stochastic differential equations of the Ito type using the stochastic averaging method. The probability density for the motion amplitude and the values for the most probable amplitudes are obtained for various mean flow velocities and turbulence levels.
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Date Issued

1987

PURL

http://purl.flvc.org/fcla/dt/14361

Subject Headings

Random vibrationMathematical models, Turbulence, Fluid dynamics

Format

Document (PDF)
Pages