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DETERMINATION OF VISCOELASTIC MATERIAL PROPERTIES USING TWO-DIMENSIONAL PLATE TESTING
Title
DETERMINATION OF VISCOELASTIC MATERIAL PROPERTIES USING TWO-DIMENSIONAL PLATE TESTING.
Creator
UHLAR, DAVID ANDREW., Florida Atlantic University, Dunn, Stanley E., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
A method of analysis is presented which employs a two-dimensional plate test to determine the dynamic modulus of elasticity and loss factor of viscoelastic damping materials. This method is based on an energy approach to the free vibration of plates. The results derived from the two-dimensional plate test procedure are compared to values from conventional beam tests. This comparison indicates that the material properties determined from the plate test method are in good agreement with values...
Show moreA method of analysis is presented which employs a two-dimensional plate test to determine the dynamic modulus of elasticity and loss factor of viscoelastic damping materials. This method is based on an energy approach to the free vibration of plates. The results derived from the two-dimensional plate test procedure are compared to values from conventional beam tests. This comparison indicates that the material properties determined from the plate test method are in good agreement with values determined from the beam test method. Thus, the dynamic modulus of elasticity and loss factor of viscoelastic damping materials can be determined from either beam or plate tests and these values can be used in the two-dimensional plate equations to evaluate the effectiveness of the damping material. In light of this study, it is suggested that beam tests be performed to derive viscoelastic material properties because of the simplicity of the beam test procedure compared to that of the plate test procedure.
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Date Issued
1982
PURL
http://purl.flvc.org/fcla/dt/14096
Subject Headings
Elastic plates and shells, Viscoelasticity
Format
Document (PDF)
Scattering of sound from a fluid-loaded cylindrical shell with a finite length mass inhomogeneity
Title
Scattering of sound from a fluid-loaded cylindrical shell with a finite length mass inhomogeneity.
Creator
Lefevre, Thierry Alain., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
The problem investigated in this thesis is that of an infinite, fluid-loaded, elastic cylindrical shell with an inhomogeneity of finite length excited by an acoustic plane wave. Seven inhomogeneities are considered to examine the parameters that influence the scattering. A full numerical approach and an iterative approach are developed to solve the shell and acoustic equations of motion expressed in the wavenumber domain. The response Green's function in the spatial domain is obtained using...
Show moreThe problem investigated in this thesis is that of an infinite, fluid-loaded, elastic cylindrical shell with an inhomogeneity of finite length excited by an acoustic plane wave. Seven inhomogeneities are considered to examine the parameters that influence the scattering. A full numerical approach and an iterative approach are developed to solve the shell and acoustic equations of motion expressed in the wavenumber domain. The response Green's function in the spatial domain is obtained using the hybrid analytical numerical technique, while the far-field scattered pressure is obtained by applying the Stationary Phase approximation. An analytical approach for the special case of a concentrated ring is developed, and the results compared to those from the full numerical solution. The range of applicability of the iterative approach is also investigated. The results show that the scattering pattern is a function of the spectral contents of the inhomogeneity distribution, and that the inhomogeneity mass influenced both the scattering pattern, and the scattering level. From the results it was also noted that an oblique angle of incidence steered the main lobe of the scattering pattern in the direction of the incoming acoustic wave. It is also demonstrated that the concentrated ring is usually a poor model to represent inhomogeneity of finite length.
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Date Issued
1997
PURL
http://purl.flvc.org/fcla/dt/15385
Subject Headings
Elastic plates and shells, Sound
Format
Document (PDF)
Multiple-period supply chain contract modeling with dynamic stochastic and price-elastic demand
Title
Multiple-period supply chain contract modeling with dynamic stochastic and price-elastic demand.
Creator
Gu, Qian-nong., Florida Atlantic University, Han, Chingping (Jim), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
In this study we developed a supply chain contract model for multiple scheduling period with dynamic demand patterns of stochastic nature, and with elastic price structures. The model presented here combined and enhanced several supply chain contract models developed previously. It is unique in that it considered multiple periods, dynamic, stochastic and price-elastic demand patterns, and flexible order quantities. Using a linear demand price-elastic relation and normal distribution pattern,...
Show moreIn this study we developed a supply chain contract model for multiple scheduling period with dynamic demand patterns of stochastic nature, and with elastic price structures. The model presented here combined and enhanced several supply chain contract models developed previously. It is unique in that it considered multiple periods, dynamic, stochastic and price-elastic demand patterns, and flexible order quantities. Using a linear demand price-elastic relation and normal distribution pattern, optimal solutions for minimum cost, maximum profit, price structure, and order policies for the entire supply chain were derived. Sensitivity analyses performed in this study gave a better understanding of relative importance of various system variables.
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Date Issued
2001
PURL
http://purl.flvc.org/fcla/dt/11964
Subject Headings
Stochastic processes, Elasticity (Economics), Business logistics
Format
Document (PDF)
Scattering and response Green's function modeling of a fluid-loaded coated cylindrical shell
Title
Scattering and response Green's function modeling of a fluid-loaded coated cylindrical shell.
Creator
Treffot, Carole., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
An acoustic compliant coating is applied on a fluid-loaded structure to control the radiated pressure, by decoupling the fluid medium from the vibrating surface. In this thesis the problem of an infinite cylindrical shell immersed in a fluid and entirely covered with an acoustic compliant layer, excited either by a ring force or an incident acoustic plane wave is considered. To model this problem two different approaches are used. The first one, which is available in the literature, is based...
Show moreAn acoustic compliant coating is applied on a fluid-loaded structure to control the radiated pressure, by decoupling the fluid medium from the vibrating surface. In this thesis the problem of an infinite cylindrical shell immersed in a fluid and entirely covered with an acoustic compliant layer, excited either by a ring force or an incident acoustic plane wave is considered. To model this problem two different approaches are used. The first one, which is available in the literature, is based on multi-layer shell theory. In this approach the scalar and the vector potential formulation are used to solve for the response and the scattering from the cylinder. The second approach is based on modeling the compliant layer by a normally reacting impedance layer on the surface of the shell. The velocity response Green's function of the shell is found using the hybrid numerical/analytical method. Results for the radiated and scattered pressure from the shell are also presented. The advantage of this second approach is that it can be used to model complex coating geometries. The results obtained with both approaches are compared.
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Date Issued
2001
PURL
http://purl.flvc.org/fcla/dt/12775
Subject Headings
Green's functions, Elastic plates and shells
Format
Document (PDF)
Identification of support conditions on a beam using finite element analysis
Title
Identification of support conditions on a beam using finite element analysis.
Creator
Ramakrishna, Suresh Babu., Florida Atlantic University, Stevens, Karl K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
The equivalent end deflections and rotations for beams with integral, but dissimilar, elastic supports were determined. Finite element analysis was used to generate the midsurface deflection of the beam. Numerical results were then fit to the analytical solution for the deflection of a beam, yielding the equivalent end slope resulting from deformations in the support. The lateral deflection at the support was available directly from the finite element calculation. The approach used for...
Show moreThe equivalent end deflections and rotations for beams with integral, but dissimilar, elastic supports were determined. Finite element analysis was used to generate the midsurface deflection of the beam. Numerical results were then fit to the analytical solution for the deflection of a beam, yielding the equivalent end slope resulting from deformations in the support. The lateral deflection at the support was available directly from the finite element calculation. The approach used for modeling of the supports is discussed. It was found that the slope and deflection at the support increase as the relative stiffness of the support decreases, as would be expected. Results are presented for both cantilever and beams with fixed ends, are valid for slender beams with small deflection.
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Date Issued
1994
PURL
http://purl.flvc.org/fcla/dt/15021
Subject Headings
Girders, Finite element method, Elastic analysis (Engineering), Structural analysis (Engineering)
Format
Document (PDF)
Middle frequency target characteristics
Title
Middle frequency target characteristics.
Creator
Castagnet, Sabine., Florida Atlantic University, Cuschieri, Joseph M.
Abstract/Description
The problem of inverse scattering where the scattering structure is unknown, and the physical properties are predicted from the measured echo when the target is insonified with known waveforms, is investigated in this thesis. The scattering structure studied is a submerged, evacuated, spherical elastic shell. The formulation of the echo is carried out using thin shell theory for low and middle frequency range, which basically assumes that shear stresses are negligible. The echo is...
Show moreThe problem of inverse scattering where the scattering structure is unknown, and the physical properties are predicted from the measured echo when the target is insonified with known waveforms, is investigated in this thesis. The scattering structure studied is a submerged, evacuated, spherical elastic shell. The formulation of the echo is carried out using thin shell theory for low and middle frequency range, which basically assumes that shear stresses are negligible. The echo is characterized by the form function in the frequency domain, and the impulse response in the time domain. The results of this thesis show that when using a chirp signal with a 200-250kHz bandwidth as the incident waveform, both the material and size of the shell can be recovered. However, the exact thickness of the shell wall couldn't be extracted.
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Date Issued
1997
PURL
http://purl.flvc.org/fcla/dt/15423
Subject Headings
Elastic plates and shells, Sonar, Frequency response (Dynamics)
Format
Document (PDF)
Methodology for fault detection and diagnostics in an ocean turbine using vibration analysis and modeling
Title
Methodology for fault detection and diagnostics in an ocean turbine using vibration analysis and modeling.
Creator
Mjit, Mustapha., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
This thesis describes a methodology for mechanical fault detection and diagnostics in an ocean turbine using vibration analysis and modeling. This methodology relies on the use of advanced methods for machine vibration analysis and health monitoring. Because of some issues encountered with traditional methods such as Fourier analysis for non stationary rotating machines, the use of more advanced methods such as Time-Frequency Analysis is required. The thesis also includes the development of...
Show moreThis thesis describes a methodology for mechanical fault detection and diagnostics in an ocean turbine using vibration analysis and modeling. This methodology relies on the use of advanced methods for machine vibration analysis and health monitoring. Because of some issues encountered with traditional methods such as Fourier analysis for non stationary rotating machines, the use of more advanced methods such as Time-Frequency Analysis is required. The thesis also includes the development of two LabVIEW models. The first model combines the advanced methods for on-line condition monitoring. The second model performs the modal analysis to find the resonance frequencies of the subsystems of the turbine. The dynamic modeling of the turbine using Finite Element Analysis is used to estimate the baseline of vibration signals in sensors locations under normal operating conditions of the turbine. All this information is necessary to perform the vibration condition monitoring of the turbine.
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Date Issued
2009
PURL
http://purl.flvc.org/FAU/369198
Subject Headings
Marine turbines, Mathematical models, Fluid dynamics, Structural dynamics, Composite materials, Mathematical models, Elastic analysis (Engineering)
Format
Document (PDF)
Convex identification and nonlinear random vibration analysis of elastic and viscoelastic structures
Title
Convex identification and nonlinear random vibration analysis of elastic and viscoelastic structures.
Creator
Fang, Jianjie, Florida Atlantic University, Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
This dissertation deals with the identification of boundary conditions of elastic structures, and nonlinear random vibration analysis of elastic and viscoelastic structures through a new energy-based equivalent linearization technique. In the part of convex identification, convex models are utilized to represent the degree of uncertainty in the boundary condition modification. This means that the identification is actually the identification of the convex model to which the actual boundary...
Show moreThis dissertation deals with the identification of boundary conditions of elastic structures, and nonlinear random vibration analysis of elastic and viscoelastic structures through a new energy-based equivalent linearization technique. In the part of convex identification, convex models are utilized to represent the degree of uncertainty in the boundary condition modification. This means that the identification is actually the identification of the convex model to which the actual boundary stiffness profile belongs. Two examples are presented to illustrate the application of the method. For the beam example the finite element analysis is performed to evaluate the frequencies of a beam with any specific boundary conditions. For the plate example, the Bolotin's dynamic edge effect method, generalized by Elishakoff, is employed to determine the approximate natural frequencies and normal modes of elastically supported isotropic, uniform rectangular plates. In the part of nonlinear random analysis, first a systematic finite element analysis procedure, based on the element's energy formulation, through conventional stochastic linearization technique, is proposed. The procedure is applicable to a wide range of nonlinear random vibration problem as long as element's energy formulations are presented. Secondly, the new energy-based stochastic linearization method in finite element analysis setting is developed to improve the conventional stochastic linearization technique. The entire formulation is produced in detail for the first time. The theory is applied to beam problem subjected to space-wise and time-wise white noise excitations. Finally, the new energy-based stochastic linearization technique is applied to treat nonlinear vibration problems of viscoelastic beams.
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Date Issued
1996
PURL
http://purl.flvc.org/fcla/dt/12467
Subject Headings
Elasticity, Viscoelasticity, Structural dynamics--Mathematical models, Vibration--Mathematical models
Format
Document (PDF)
Mechanical characterization of woven fabric composite materials
Title
Mechanical characterization of woven fabric composite materials.
Creator
Alif, Nidal M., Florida Atlantic University, Carlsson, Leif A., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
The mechanical behavior of woven fabric composites is presented in this study through modeling of the elastic properties and experimental studies on the failure behavior and fracture analysis. A two-dimensional laminate theory based elastic model for the prediction of the elastic constants of satin weave fabric composites is developed. The predicted elastic constants are compared with results from other models and correlated with the experimental data. An experimental study is presented on...
Show moreThe mechanical behavior of woven fabric composites is presented in this study through modeling of the elastic properties and experimental studies on the failure behavior and fracture analysis. A two-dimensional laminate theory based elastic model for the prediction of the elastic constants of satin weave fabric composites is developed. The predicted elastic constants are compared with results from other models and correlated with the experimental data. An experimental study is presented on mechanical response in tension, compression and shear and on damage development in tension of two woven fabric composite systems viz. carbon/epoxy and glass/epoxy. Damage inspection of the carbon/epoxy composite under tension revealed that the initial failure was cracking of pure matrix regions followed by transverse bundle cracking. Fill/warp debonding and longitudinal splits of the fill bundles occurred close to ultimate failure of the composite. The glass/epoxy composite displayed damage in the form of fill/warp debonding and longitudinal splits, but no transverse yarn cracking. Interlaminar fracture behavior of a five-harness satin orthogonal woven fabric carbon/epoxy composite laminate loaded in mode I, mode II and mixed mode has been investigated. Special emphasis was put on microscopic details of crack growth, and their relation to the fracture resistance. For all fracture mode combinations it was found that crack growth occurred in a nonplanar region of topology determined by the weave pattern and relative positioning of the plies adjacent to the crack plane. The woven fabric structure constrains fiber bridging, but partial debonding of transversely oriented fiber bundles led to occasional crack branching, stick-slip behavior leading to variations in the mode I fracture resistance. Slow stable crack growth occurred in the mode I and mode II fracture specimens prior to unstable fracture and resulted in nonlinear load-displacement response.
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Date Issued
1996
PURL
http://purl.flvc.org/fcla/dt/12481
Subject Headings
Composite materials--Mechanical properties, Textile fabrics--Mechanical properties, Elastic fabrics
Format
Document (PDF)