Current Search: Elastic plates and shells (x)
View All Items
 Title
 DETERMINATION OF VISCOELASTIC MATERIAL PROPERTIES USING TWODIMENSIONAL 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 twodimensional 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 twodimensional 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 twodimensional 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 twodimensional 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 twodimensional 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.
Show less  Date Issued
 1982
 PURL
 http://purl.flvc.org/fcla/dt/14096
 Subject Headings
 Elastic plates and shells, Viscoelasticity
 Format
 Document (PDF)
 Title
 Scattering of sound from a fluidloaded 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, fluidloaded, 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, fluidloaded, 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 farfield 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.
Show less  Date Issued
 1997
 PURL
 http://purl.flvc.org/fcla/dt/15385
 Subject Headings
 Elastic plates and shells, Sound
 Format
 Document (PDF)
 Title
 Scattering and response Green's function modeling of a fluidloaded 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 fluidloaded 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 fluidloaded 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 multilayer 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.
Show less  Date Issued
 2001
 PURL
 http://purl.flvc.org/fcla/dt/12775
 Subject Headings
 Green's functions, Elastic plates and shells
 Format
 Document (PDF)
 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 200250kHz 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.
Show less  Date Issued
 1997
 PURL
 http://purl.flvc.org/fcla/dt/15423
 Subject Headings
 Elastic plates and shells, Sonar, Frequency response (Dynamics)
 Format
 Document (PDF)