View All Items

Title: VIBRATION ANALYSIS OF RECTANGULAR PLATES WITH COMPLETE AND PARTIAL CONSTRAINED-LAYER DAMPING TREATMENTS.
Creator: HSU, HONG-YUAN., Florida Atlantic University, Stevens, Karl K.
Abstract/Description: A theoretical analysis for predicting the system loss factors and natural frequencies of rectangular plates with complete and partial constrained-layer damping treatments has been presented. This analysis is based upon an energy approach to the free vibration of plates. Results predicted were compared with those from experiments. Satisfactory agreement has been reached. Both the theoretical and the experimental results presented in this thesis indicate clearly that partial constrained-layer...
Show moreA theoretical analysis for predicting the system loss factors and natural frequencies of rectangular plates with complete and partial constrained-layer damping treatments has been presented. This analysis is based upon an energy approach to the free vibration of plates. Results predicted were compared with those from experiments. Satisfactory agreement has been reached. Both the theoretical and the experimental results presented in this thesis indicate clearly that partial constrained-layer damping treatments can provide effective, or even superior, amounts of damping, and that their use can lead to significant savings in material costs and weight.
Show less
Date Issued: 1983
PURL: http://purl.flvc.org/fcla/dt/14160
Subject Headings: Damping (Mechanics), Vibration, Plates (Engineering)--Vibration
Format: Document (PDF)

Title: Vibration of nonlocal carbon nanotubes and graphene nanoplates.
Creator: Hache, Florian, Elishakoff, Isaac, Challamel, Noël, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis deals with the analytical study of vibration of carbon nanotubes and graphene plates. First, a brief overview of the traditional Bresse-Timoshenko models for thick beams and Uflyand-Mindlin models for thick plates will be conducted. It has been shown in the literature that the conventionally utilized mechanical models overcorrect the shear effect and that of rotary inertia. To improve the situation, two alternative versions of theories of beams and plates are proposed. The first...
Show moreThis thesis deals with the analytical study of vibration of carbon nanotubes and graphene plates. First, a brief overview of the traditional Bresse-Timoshenko models for thick beams and Uflyand-Mindlin models for thick plates will be conducted. It has been shown in the literature that the conventionally utilized mechanical models overcorrect the shear effect and that of rotary inertia. To improve the situation, two alternative versions of theories of beams and plates are proposed. The first one is derived through the use of equilibrium equations and leads to a truncated governing differential equation in displacement. It is shown, by considering a power series expansion of the displacement, that this is asymptotically consistent at the second order. The second theory is based on slope inertia and results in the truncated equation with an additional sixth order derivative term. Then, these theories will be extended in order to take into account some scale effects such as interatomic interactions that cannot be neglected for nanomaterials. Thus, different approaches will be considered: phenomenological, asymptotic and continualized. The basic principle of continualized models is to build continuous equations starting from discrete equations and by using Taylor series expansions or Padé approximants. For each of the different models derived in this study, the natural frequencies will be determined, analytically when the closed-form solution is available, numerically when the solution is given through a characteristic equation. The objective of this work is to compare the models and to establish the eventual superiority of a model on others.
Show less
Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013019
Subject Headings: Carbon nanotubes, Graphene, Vibration
Format: Document (PDF)

Title: Effects of an internal flow on the vibration of thin cylindrical shells.
Creator: Leyrat, Gilles F., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The response and the dynamic stability of thin cylindrical shells excited by a point force with an internal heavy medium (water) moving with a constant mean flow velocity are investigated. Two sets of analysis are discussed, one for infinitely long shells and one for shells of finite length. The infinite condition applies to shells which are sufficiently long to be considered infinite. In this case, the solution is obtained by means of a spatial Fourier transform in the axial direction and a...
Show moreThe response and the dynamic stability of thin cylindrical shells excited by a point force with an internal heavy medium (water) moving with a constant mean flow velocity are investigated. Two sets of analysis are discussed, one for infinitely long shells and one for shells of finite length. The infinite condition applies to shells which are sufficiently long to be considered infinite. In this case, the solution is obtained by means of a spatial Fourier transform in the axial direction and a modal decomposition in the circumferential direction. Using this solution, input and transfer accelerances are determined. The results of this part of this analysis show that input accelerances are globally preserved as the mean flow velocity changes. For the transfer accelerances, broadband peaks appear which are caused by the phase matching between propagating waves of different mode numbers. These broadband peaks are shifted and modified by the mean flow velocity. For shells of finite length, simply supported boundary conditions are assumed. In this case, the response is obtained by using a normal mode expansion of the in vacuo shell and the Kirchhof-Helmholtz equation derived for a fluid moving at constant flow velocity and bounded by a perfectly rigid cylinder. For finite shells, the main effect of the flow on the response is to decrease the natural frequencies of the shell. The extent of the change in frequency depends on the circumferential and axial mode numbers. Experimental results are also presented for a pipe shell of radius 0.025m and wall thickness 1.5mm. These results are compared with the analytical results for similar shell and flow condition and the agreement is very good. Using the analysis developed for the response, results are presented on the instabilities that can be induced by the flow. It is found that these instabilities are not restricted to finite pipes, but can also exist for cylindrical shells of infinite extent.
Show less
Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/12249
Subject Headings: Shells (Engineering)--Vibration
Format: Document (PDF)

Title: A STUDY OF FRICTION DAMPING AS APPLIED TO VIBRATING STRUCTURES.
Creator: DESAI, VIJAY R., Florida Atlantic University, Cuschieri, Joseph M.
Abstract/Description: Of the many methods of introducing damping in vibrating structures, the dissipation of energy due to interfacial slip can significantly increase the damping loss factor. However, because of the lack of understanding and other phenomena such as fretting corrosion and loss of structural rigidity, friction damping is rarely used. A study was thus undertaken to investigate this complex phenomenon, with emphasis on trying to gain a better understanding of friction damping with certain parameters...
Show moreOf the many methods of introducing damping in vibrating structures, the dissipation of energy due to interfacial slip can significantly increase the damping loss factor. However, because of the lack of understanding and other phenomena such as fretting corrosion and loss of structural rigidity, friction damping is rarely used. A study was thus undertaken to investigate this complex phenomenon, with emphasis on trying to gain a better understanding of friction damping with certain parameters such as clamping pressure, frequency, magnitude of excitation and surface finish. Although the non-linearities associated with friction makes this mechanism difficult to model mathematically, finite element (FE) analysis shows some promise. Although the results obtained using an FE model were not exactly comparable to the experimental results, these analytical results did show the same general trends as observed in the experiments.
Show less
Date Issued: 1987
PURL: http://purl.flvc.org/fcla/dt/14369
Subject Headings: Damping (Mechanics), Vibration
Format: Document (PDF)

Title: VIBRATION ANALYSIS OF RECTANGULAR PLATES UNDER FLUID LOADING.
Creator: LEE, TZER CHIA., Florida Atlantic University, Dunn, Stanley E., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: An energy method is presented for predicting the natural frequencies, radiation loss factor and system loss factor of simply supported rectangular plates under fluid loading. Both bare plates and plates with complete damping treatments are considered. Results obtained using the method developed are compared with two other theories. The agreement is generally good. The study points out the need for detailed analyses of plate vibration patterns and their associated radiation output under...
Show moreAn energy method is presented for predicting the natural frequencies, radiation loss factor and system loss factor of simply supported rectangular plates under fluid loading. Both bare plates and plates with complete damping treatments are considered. Results obtained using the method developed are compared with two other theories. The agreement is generally good. The study points out the need for detailed analyses of plate vibration patterns and their associated radiation output under various plate boundary conditions. There also exists a need for carefully conducted experimental work to verify the applicability of the current theory.
Show less
Date Issued: 1981
PURL: http://purl.flvc.org/fcla/dt/14086
Subject Headings: Plates (Engineering)--Vibration
Format: Document (PDF)

Title: An application of perturbation techniques to the vibration analysis of structures with viscoelastic coating modifications.
Creator: Kelly, William Joseph, Jr., Florida Atlantic University, Stevens, Karl K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Proper application of matrix perturbation theory to the structural modification of vibrating systems yields accurate results without resolving the eigenvalue problem. For this reason it seems that the method may require less computer time and cost in performing iterative type design work. This thesis investigates the application of first-order perturbation techniques to a torsional shaft system subject to viscoelastic damping treatment modifications. The modifications are of general form in...
Show moreProper application of matrix perturbation theory to the structural modification of vibrating systems yields accurate results without resolving the eigenvalue problem. For this reason it seems that the method may require less computer time and cost in performing iterative type design work. This thesis investigates the application of first-order perturbation techniques to a torsional shaft system subject to viscoelastic damping treatment modifications. The modifications are of general form in that the coating length and thickness are not restricted. Large modifications are built up by a series of small first-order perturbations. In addition to developing a better understanding of the usefulness of this application of perturbation theory, the goal of this paper is also to understand the nonproportional damping effects of partial viscoelastic coatings.
Show less
Date Issued: 1988
PURL: http://purl.flvc.org/fcla/dt/14455
Subject Headings: Vibration, Perturbation (Mathematics)
Format: Document (PDF)

Title: Vibrational power flow in thick connected plates.
Creator: McCollum, Michele D., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The total vibrational power flow in connected plate structures is investigated using an analytical "Power Flow" approach. The effects of shear and rotary inertia on the flexural wave transmission and the influence of in-plane wave generation at structural discontinuities are included in the analytical model. In formulating a Power Flow model, the structure is divided into substructures whose responses may be determined analytically to obtain expressions for the input and transfer mobilities...
Show moreThe total vibrational power flow in connected plate structures is investigated using an analytical "Power Flow" approach. The effects of shear and rotary inertia on the flexural wave transmission and the influence of in-plane wave generation at structural discontinuities are included in the analytical model. In formulating a Power Flow model, the structure is divided into substructures whose responses may be determined analytically to obtain expressions for the input and transfer mobilities of the substructures. For the case of plate-type structures joined along a line, the mobilities are functions of both frequency and space. The power transmission between the individual plate substructures is then written as a function of these mobility expressions. The structure of concern in this dissertation consists of two plates connected in an L-configuration. In obtaining the expressions for the mobilities, the vibrational response of the individual plates is determined by solving the appropriate equations of motion. In this study the antisymmetric (flexural) motion is described using Mindlin's (1951) thick plate approximation to the three-dimensional equations of motion. The applicability of this thick plate formulation is limited to frequencies below the frequency of the first antisymmetric mode of thickness-shear vibration of the plate. The symmetric (in-plane) motion of the plates is described using the generalized theory of plane stress which neglects the direct coupling of the in-plane motion with the thickness vibration modes, and is therefore valid only for frequencies which are lower than the frequency of the first mode of pure thickness vibration of the plate. The results for the power transmission in the L-plate obtained using the Power Flow formulation are verified at high frequencies by comparison with the results obtained using the Statistical Energy Analysis (SEA) technique. The SEA formulation for the L-plate is based on Mindlin's equations for flexural motion and the theory of generalized plane stress for in-plane vibration. The results of the Power Flow formulation are verified at low frequencies by the results obtained using a Finite Element model of the L-shaped plate.
Show less
Date Issued: 1988
PURL: http://purl.flvc.org/fcla/dt/11929
Subject Headings: Plates (Engineering)--Vibration
Format: Document (PDF)

Title: VIBRATION ANALYSIS OF RECTANGULAR PLATES WITH COMPLETE CONSTRAINED-LAYER DAMPING TREATMENTS.
Creator: CO, CHI-MIN., Florida Atlantic University, Stevens, Karl K.
Abstract/Description: An energy method for predicting the natural frequencies and loss factors of Rectangular Plates with Complete Constrained-Layer Damping Treatments has been presented. Results obtained using the method developed were compared with those of two former theories. The agreement between the current theory and these two theories was generally good. There is a serious need for carefully conducted experimental work to verify the applicability of the current theory and of the various other laminated...
Show moreAn energy method for predicting the natural frequencies and loss factors of Rectangular Plates with Complete Constrained-Layer Damping Treatments has been presented. Results obtained using the method developed were compared with those of two former theories. The agreement between the current theory and these two theories was generally good. There is a serious need for carefully conducted experimental work to verify the applicability of the current theory and of the various other laminated plate theories in existence. It is believed that the method of analysis presented can be extended to handle plates with partial constrainedlayer damping treatments.
Show less
Date Issued: 1981
PURL: http://purl.flvc.org/fcla/dt/14085
Subject Headings: Plates (Engineering)--Vibration
Format: Document (PDF)

Title: FLIGHT TESTS OF AN OPEN LOOP HIGHER HARMONIC CONTROL SYSTEM ON AN S-76A HELICOPTER.
Creator: WALSH, DAVID M., Florida Atlantic University, Goankar, Gopal, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Flight tests of an open loop higher harmonic vibration control system were conducted on an S-76A helicopter during the early part of 1985. This paper discusses the design, conduct and results of those tests. The flight tests included evaluations of Higher Harmonic Control (HHC) inputs in the longitudinal, lateral and collective axes at varying amplitudes and phases. These flight tests have demonstrated the feasibility of HHC on a medium size, high speed helicopter. Significant vibration...
Show moreFlight tests of an open loop higher harmonic vibration control system were conducted on an S-76A helicopter during the early part of 1985. This paper discusses the design, conduct and results of those tests. The flight tests included evaluations of Higher Harmonic Control (HHC) inputs in the longitudinal, lateral and collective axes at varying amplitudes and phases. These flight tests have demonstrated the feasibility of HHC on a medium size, high speed helicopter. Significant vibration reductions throughout the aircraft were demonstrated at forward speeds up to 150 knots. The capability of HHC to reduce vibrations was also demonstrated at varying rotor speeds and during maneuvers. Structural data obtained during testing, showed a general increase in control system loads during HHC operation. However, no loads were above structural limits and it appears that a control system could be designed with sufficient strength to accept all HHC loads.
Show less
Date Issued: 1986
PURL: http://purl.flvc.org/fcla/dt/14341
Subject Headings: Vibration (Aeronautics), Helicopters
Format: Document (PDF)

Title: Mobility power flow analysis of connected thick plates with a step discontinuity.
Creator: Faivre d'Arcier, Eric., Florida Atlantic University, Cuschieri, Joseph M.
Abstract/Description: In this thesis the flow of vibration power between two coupled, finite plates of arbitrary thicknesses is considered using a Mobility Power Flow (MPF) approach. The plate structure is divided into substructures and mobility functions are determined for the independent substructures. Power flow expressions are derived based on continuity of forces and displacements. The solution presented here considers the effects of both in-plane waves and out-of-plane waves. The solution is applicable to...
Show moreIn this thesis the flow of vibration power between two coupled, finite plates of arbitrary thicknesses is considered using a Mobility Power Flow (MPF) approach. The plate structure is divided into substructures and mobility functions are determined for the independent substructures. Power flow expressions are derived based on continuity of forces and displacements. The solution presented here considers the effects of both in-plane waves and out-of-plane waves. The solution is applicable to frequencies below the first mode of thickness-shear vibration. The results obtained show that at low frequencies, the out-of-plane waves dominate in the transmission of vibrational power. However, at high frequencies or for thick plates, the in-plane waves play a significant role in the power transmission through the plate.
Show less
Date Issued: 1991
PURL: http://purl.flvc.org/fcla/dt/14705
Subject Headings: Vibration--Measurement
Format: Document (PDF)

Title: ANALYSIS OF FREE VIBRATIONS OF BEAMS WITH VARYING DEGREES OF UNCONSTRAINED VISCOELASTIC DAMPING LAYER COVERAGE.
Creator: DE AGUIAR, JOAO BATISTA., Florida Atlantic University, Dunn, Stanley E.
Abstract/Description: A method of analysis addressing the problem of predicting the performance of beams with viscoelastic damping layer coating of varying degrees of coverage undergoing free vibrations is presented. Results based on this analysis and using mechanical properties of selected materials are generated for five different boundary conditions. The analytical results are verified experimentally for the case of a clamped-free beam. Also the main hypotheses employed in the theoretical approach are verified....
Show moreA method of analysis addressing the problem of predicting the performance of beams with viscoelastic damping layer coating of varying degrees of coverage undergoing free vibrations is presented. Results based on this analysis and using mechanical properties of selected materials are generated for five different boundary conditions. The analytical results are verified experimentally for the case of a clamped-free beam. Also the main hypotheses employed in the theoretical approach are verified. Finally, an analysis of the results leads to a discussion of the dynamic properties of coated beams.
Show less
Date Issued: 1982
PURL: http://purl.flvc.org/fcla/dt/14097
Subject Headings: Viscoelasticity, Girders--Vibration
Format: Document (PDF)

Title: The measurement of structural power flow in thin plate structures.
Creator: Padiyar, Satish., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: An analytical and experimental investigation of the flow of vibrational power in a thin, L-shaped, finite plate structure subjected to mechanical and acoustic excitation is presented. In the analytical approach, mobility functions are used to determine the structural intensity vectors at various locations on the plate structure. Simulation results of intensity vectors estimated using three different measurement schemes are compared. The experimentally measured intensity vectors, for the case...
Show moreAn analytical and experimental investigation of the flow of vibrational power in a thin, L-shaped, finite plate structure subjected to mechanical and acoustic excitation is presented. In the analytical approach, mobility functions are used to determine the structural intensity vectors at various locations on the plate structure. Simulation results of intensity vectors estimated using three different measurement schemes are compared. The experimentally measured intensity vectors, for the case of mechanical excitation, using a four accelerometer array, are presented. They are found to match well with the results from the corresponding simulation. Similar results are obtained for the case of acoustic excitation of the L-shaped plate. The general pattern of the structural intensity vectors is found to be in agreement with the expected results.
Show less
Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/14678
Subject Headings: Plates (Engineering)--Vibration
Format: Document (PDF)

Title: Structural intensity measurements in thick structures.
Creator: Vallory, Joelle., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Structural intensity is propagated through a thick structure by both in-plane and out-of-plane (transverse) waves. These waves propagate at different phase speeds and therefore it is important to distinguish the components of the structural intensity associated with each wave type. To show the presence of these different wave components, experimental results are performed on a thick beam. Using a frequency-wavenumber analysis, the different waves and contributions to the structural intensity...
Show moreStructural intensity is propagated through a thick structure by both in-plane and out-of-plane (transverse) waves. These waves propagate at different phase speeds and therefore it is important to distinguish the components of the structural intensity associated with each wave type. To show the presence of these different wave components, experimental results are performed on a thick beam. Using a frequency-wavenumber analysis, the different waves and contributions to the structural intensity are identified. The significance of the contributions to the structural intensity are a function of both frequency and thickness of the structure. Using simulated measurements on a thick L-shaped plate, the relative importance between the in-plane and out-of-plane contributions to structural intensity as a function of frequency and thickness is demonstrated. It is shown that in-plane wave contributions increase in importance as frequency or thickness increases.
Show less
Date Issued: 1991
PURL: http://purl.flvc.org/fcla/dt/14697
Subject Headings: Structural dynamics, Noise, Vibration
Format: Document (PDF)

Title: Transmission of vibrational power in joined structures.
Creator: Gibert, Thierry M., Florida Atlantic University, Cuschieri, Joseph M.
Abstract/Description: The objective of this thesis is the investigation of the transmission of vibrational power between beam-like and plate-like structures with joints using Statistical Energy Analysis (SEA) and an experimental approach. In the case of the L-shaped plate the influence of different structure parameters is investigated to determine possible ways to reduce both the transmitted power and the noise radiated by the receiver structure. The total transmitted power is measured and compared to theoretical...
Show moreThe objective of this thesis is the investigation of the transmission of vibrational power between beam-like and plate-like structures with joints using Statistical Energy Analysis (SEA) and an experimental approach. In the case of the L-shaped plate the influence of different structure parameters is investigated to determine possible ways to reduce both the transmitted power and the noise radiated by the receiver structure. The total transmitted power is measured and compared to theoretical predictions. Also power maps are generated which show the transmission of vibrational power from the source beam to the receiver beam. In the power flow measurements three different techniques are implemented with similar results which all match the analytical results.
Show less
Date Issued: 1988
PURL: http://purl.flvc.org/fcla/dt/14436
Subject Headings: Vibration, Power transmission
Format: Document (PDF)

Title: EXPERIMENTAL MODAL ANALYSIS OF A DISCMILL FIBERIZER DISC (VIBRATION, PLATES, RESONANCES).
Creator: FREEZE, WILLIAM PRESTON., Florida Atlantic University, Stevens, Karl K.
Abstract/Description: Modal analysis testing techniques were used to determine the modal parameters and mode shapes for flexural vibration of a Fiberizer Discmill disc to help define a safe operating speed range. The modal parameters and mode shapes were determined for the first six diametral modes, the first concentric mode, and the first rigid body shaft mode. The disc consisted of a circular aluminum plate with eight equally and symmetrically spaced radial cutters on one face of the disc and eight equally...
Show moreModal analysis testing techniques were used to determine the modal parameters and mode shapes for flexural vibration of a Fiberizer Discmill disc to help define a safe operating speed range. The modal parameters and mode shapes were determined for the first six diametral modes, the first concentric mode, and the first rigid body shaft mode. The disc consisted of a circular aluminum plate with eight equally and symmetrically spaced radial cutters on one face of the disc and eight equally spaced peripheral cutters located on the rim of the disc midway between the angular locations of the radial cutters. All cutters were of tool steel. The safe area of operation is determined to be between 3000 rpm and 3600 rpm. The experimental setup and procedure Is described in detail with particular emphasis on validation of assumptions required for the analytical approaches used in calculating the modal data.
Show less
Date Issued: 1986
PURL: http://purl.flvc.org/fcla/dt/14329
Subject Headings: Milling machinery, Vibration--Measurement
Format: Document (PDF)

Title: Concurrent engineering design of a miniature piezo-transducer-vibrator.
Creator: Hedayatnia, Mostafa., Florida Atlantic University, Mazouz, Abdel Kader, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: A state-of-the-art Piezo-Transducer-Vibrator suitable for a wristwatch has been developed based on a "Customer Comprehension" program: To look at the product from the customer point of view and try to satisfy those needs simultaneously using computer simulation leading to a reliable design in a shorter cycle time. This device is a miniature integrated compact form of both audio and silent alerts which uses less than 8 mA current; desirable to be used in equipments with very small power...
Show moreA state-of-the-art Piezo-Transducer-Vibrator suitable for a wristwatch has been developed based on a "Customer Comprehension" program: To look at the product from the customer point of view and try to satisfy those needs simultaneously using computer simulation leading to a reliable design in a shorter cycle time. This device is a miniature integrated compact form of both audio and silent alerts which uses less than 8 mA current; desirable to be used in equipments with very small power sources. A new ergonomic study was conducted in comprehending the minimum acceptable shake and frequency on human wrist. The complete Piezo-bender structure, its driving format, and its vibration has been modeled accurately to obtain an optimum geometry design for the best possible shake, satisfying all constraints.
Show less
Date Issued: 1994
PURL: http://purl.flvc.org/fcla/dt/12358
Subject Headings: Piezoelectric transducers, Wrist watches, Vibrators
Format: Document (PDF)

Title: Mobility power flow analysis of an infinite cylindrical shell with an enclosed plate discontinuity.
Creator: Buchmann, Patrick Pierre., Florida Atlantic University, Cuschieri, Joseph M.
Abstract/Description: A mobility power flow approach is used to study the response of an infinitely-long cylindrical shell with an internal plate discontinuity. The shell is excited by either a ring radial force or by a plane acoustic wave. The junction between the shell and the internal plate is assumed to be radially pinned such that in-plane waves of the plate can be neglected. The junction forces are expressed in terms of the mobility functions of the plate and the shell. From knowledge of the junction forces...
Show moreA mobility power flow approach is used to study the response of an infinitely-long cylindrical shell with an internal plate discontinuity. The shell is excited by either a ring radial force or by a plane acoustic wave. The junction between the shell and the internal plate is assumed to be radially pinned such that in-plane waves of the plate can be neglected. The junction forces are expressed in terms of the mobility functions of the plate and the shell. From knowledge of the junction forces and velocities, the power input, the power flow from the shell to the plate, the shell response and the radiated far-field scattered pressure are determined for the circumferential mode n = 0. The results show how the energy propagates from one structure to the other, and present a very clear picture of the characteristics of the scattering pattern from the junction forces.
Show less
Date Issued: 1994
PURL: http://purl.flvc.org/fcla/dt/15113
Subject Headings: Shells (Engineering)--Vibration, Plates (Engineering)--Vibration, Structural dynamics, Vibration
Format: Document (PDF)

Title: Estimates of water turbine noise levels.
Creator: Guerra, Julian., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This work seeks to understand water turbine noise generation and to make preliminary estimations of the noise levels. Any structure attached to a turbine upstream its blades will generate unsteady fluctuating loads on the blade's surface, which are proportional to the radiated acoustic pressure. The noise levels of a simplified turbine based on existing designs surpass the ambient noise levels of the ocean at low frequencies ( 30 Hz).
Show moreThis work seeks to understand water turbine noise generation and to make preliminary estimations of the noise levels. Any structure attached to a turbine upstream its blades will generate unsteady fluctuating loads on the blade's surface, which are proportional to the radiated acoustic pressure. The noise levels of a simplified turbine based on existing designs surpass the ambient noise levels of the ocean at low frequencies (< 20 Hz) by approximately 50 dB ref 1 μPa and stay under the ambient noise levels at higher frequencies for a blade-passing frequency of 0.83 Hz and point of observation (100 m, 45 degrees, 45 degrees) from the hub. Streamlining the cross-section of the upstream structure as well as reducing its width decrease the noise levels by approximately 40 dB ref 1 μPa, at low frequencies and moderately increase them at higher frequencies. Increasing the structure-rotor distance decreases the noise levels with increasing frequencies (> 30 Hz).
Show less
Date Issued: 2011
PURL: http://purl.flvc.org/FAU/3170958
Subject Headings: Turbines, Vibration, Testing, Underwater acoustics, Fluid dynamics
Format: Document (PDF)

Title: ANALYSIS OF DAMPING LAYER TREATMENTS FOR PLATES USING EXPERIMENTALLY DETERMINED MODE SHAPES.
Creator: JAISING, VINOD R., Florida Atlantic University, Stevens, Karl K.
Abstract/Description: A method of analysis is presented to determine the natural frequencies and loss factors of a plate covered with viscoelastic coating, using experimentally obtained mode shapes. The mode shapes for a square plate clamped on all edges are determined using an HP 5423 A Structural Dynamics Analyzer. A computer program, based on the method of analysis, is developed to determine the natural frequencies and loss factors of a rectangular plate covered with viscoelastic material, and clamped on all...
Show moreA method of analysis is presented to determine the natural frequencies and loss factors of a plate covered with viscoelastic coating, using experimentally obtained mode shapes. The mode shapes for a square plate clamped on all edges are determined using an HP 5423 A Structural Dynamics Analyzer. A computer program, based on the method of analysis, is developed to determine the natural frequencies and loss factors of a rectangular plate covered with viscoelastic material, and clamped on all edges. It was found that, for a fully coated plate, and for a mesh with twenty-five mesh points, the error in the fundamental frequency was approximately 5 percent. A comparison between the mode shapes for the bare plate and for the fully coated plate revealed no significant difference. It was also found that increasing the number of measurement points would not significantly improve the results.
Show less
Date Issued: 1981
PURL: http://purl.flvc.org/fcla/dt/14050
Subject Headings: Plates (Engineering)--Vibration, Damping (Mechanics)
Format: Document (PDF)

Title: Adaptive control of vibration in flexible smart structures.
Creator: Gopinathan, Murali., Florida Atlantic University, Pajunen, Grazyna, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
Abstract/Description: This dissertation is concerned with the relevant research in developing finite dimensional indirect adaptive schemes to control vibrations in flexible smart structures based on the finite element approximation of the infinite dimensional system. The advantage of this type of modeling is that the dominant modes of vibrations wherein the total energy is concentrated are accommodated thereby avoiding the so-called "spillover" phenomenon. Further, the mass, stiffness and damping coefficients...
Show moreThis dissertation is concerned with the relevant research in developing finite dimensional indirect adaptive schemes to control vibrations in flexible smart structures based on the finite element approximation of the infinite dimensional system. The advantage of this type of modeling is that the dominant modes of vibrations wherein the total energy is concentrated are accommodated thereby avoiding the so-called "spillover" phenomenon. Further, the mass, stiffness and damping coefficients associated with each element appear explicitly in the model facilitating the derivation of the ARMA parametric representation which is suitable for on-line estimation of the structural parameters. The state-space representation of the finite dimensional model is used to design an indirect linear quadratic self tuning regulator algorithm using the parameter estimation, indicated above. Further, a method to choose the control and state weighting matrices (required to design the controller) to yield a stable closed-loop system, is presented. Simulation results demonstrating the performance of the adaptive control system are presented. Another algorithm based on the model reference technique is also developed by considering the discrete time approximation of the finite dimensional model. This control algorithm in conjunction with the parameter estimation constitute an indirect model reference adaptive control system. Simulation results are presented to demonstrate the effect of the reference model parameters, which may impose certain constraints on the force requirements causing actuator saturation and thereby affecting the stability of the closed-loop system. In order to overcome the problem of using bulky and expensive sensors to measure transverse displacement and velocity, a new spatial recursive technique to estimate these variables alternatively by using a distributed set of (measured) strain data, is developed. Relevant algorithm enables the use of smart materials to sense the strain developed at various locations along the length of the structure leading to the development of flexible smart structures. Experimental results on the personal computer based control of vibrations in an aluminum beam using patches of polyvinyldene fluoride (PVDF), and lead zirconate titanate (PZT) as sensors and control actuators respectively, are furnished to demonstrate the feasibility of real-time implementation of the above mentioned control algorithms.
Show less
Date Issued: 1995
PURL: http://purl.flvc.org/fcla/dt/12418
Subject Headings: Adaptive control systems, Smart structures, Vibration
Format: Document (PDF)

Vibration (17)	+ -
Plates (Engineering)--Vibration (13)	+ -
Fluid dynamics (9)	+ -
Damping (Mechanics) (7)	+ -
Structural dynamics (7)	+ -

Mathematical models (6)	+ -
Shells (Engineering)--Vibration (4)	+ -
Girders--Vibration (3)	+ -
Helicopters (3)	+ -
Marine turbines (3)	+ -
Vibration (Aeronautics) (3)	+ -
Vibration--Measurement (3)	+ -
Acoustical engineering (2)	+ -
Adaptive control systems (2)	+ -
Aerodynamics (2)	+ -
Bridges--Vibration (2)	+ -
Buckling (Mechanics) (2)	+ -
Measurement (2)	+ -
Perturbation (Mathematics) (2)	+ -
Piezoelectric transducers (2)	+ -
Rotors (Helicopters) (2)	+ -
Structural analysis (2)	+ -
Turbines (2)	+ -
Underwater acoustics (2)	+ -
Vibration (Aerodynamics) (2)	+ -
Vibration (Marine engineering) (2)	+ -
Vibrators (2)	+ -
Viscoelasticity (2)	+ -
Wrist watches (2)	+ -
Acoustic radiation pressure (1)	+ -

Florida Atlantic University (46)	+ -
College of Engineering and Computer Science (36)	+ -
Department of Ocean and Mechanical Engineering (32)	+ -
Cuschieri, Joseph M. (15)	+ -
Stevens, Karl K. (8)	+ -

Elishakoff, Isaac (5)	+ -
Dunn, Stanley E. (3)	+ -
Department of Civil, Environmental and Geomatics Engineering (2)	+ -
Department of Computer and Electrical Engineering and Computer Science (2)	+ -
Lin, Y. K. (2)	+ -
Pentaras, Demetris. (2)	+ -
Yong, Yan (2)	+ -
Abdelahad, Firas A. (1)	+ -
Ackermann, Lloyd E. J. (1)	+ -
Atanasova, Sylvia T. (1)	+ -
BHAT, RAJENDRA AGHUT. (1)	+ -
Buchmann, Patrick Pierre. (1)	+ -
CO, CHI-MIN. (1)	+ -
Calle, Oscar F. (1)	+ -
Cava, Peter (1)	+ -
Challamel, Noël (1)	+ -
Chunduru, Srinivas Jaya. (1)	+ -
Cimerman, Benjamin Pierre. (1)	+ -
Coulson, Robert Kenneth. (1)	+ -
DE AGUIAR, JOAO BATISTA. (1)	+ -
DESAI, VIJAY R. (1)	+ -
Dorothy F. Schmidt College of Arts and Letters (1)	+ -
Duprez, Adrien Eric. (1)	+ -
FREEZE, WILLIAM PRESTON. (1)	+ -
Faivre d'Arcier, Eric. (1)	+ -

Search In

Pages

Pages

Sort Results By:

Narrow results by:

Collection

Topical Subject

Genre

Type of Resource

Language

Creator

Format

Owner