Imaging surface acoustic waves in anisotropic and periodic media
type: CreativeWork
description: A new technique has been developed for studying surface acoustic wave propagation. The technique, which uses non-contact immersion transducers to excite and detect ultrasound with frequencies between 1 and 20 MHz, allows convenient examination of surface waves traveling in arbitrary directions on a sample. Coupling the easy scanning of ultrasound propagation with time-resolved detection of the surface-wave amplitude makes this method particularly suited to examining anisotropic materials. The first section of this thesis deals with surface waves on crystals and other homogeneous solids. The general theory describing surface-wave behavior on anisotropic materials is adapted to our technique. In anisotropic materials, two types of surface waves, designated Rayleigh surface waves and pseudo-surface waves, satisfy the boundary conditions for a free surface. The experimental design is then described, and images obtained on a variety of crystalline samples are examined. Discrepancies between the calculations and the observed results have led to an investigation of the effects of fluid loading on the surface waves. It is found that coupling between the surface waves and the loading liquid will attenuate the propagating surface waves, with high frequencies showing stronger attenuation. In addition, the loading will affect the velocities of the surface waves, and in some cases will support additional surface-wave modes. The remainder of the thesis examines surface-wave propagation on a variety of periodic structures. Carbon-fiber/epoxy composites are first examined, and the elastic properties of a homogeneous sample are used to determine the surface-wave velocities of layered samples in the long-wavelength limit. Two systems are then examined in the dispersive regime, where the wavelength of the surface waves is comparable to the periodicity of the sample. The first, a multilayer sample constructed from layers of aluminum and a low-density polymer, has one-dimensional symmet…
abstract: A new technique has been developed for studying surface acoustic wave propagation. The technique, which uses non-contact immersion transducers to excite and detect ultrasound with frequencies between 1 and 20 MHz, allows convenient examination of surface waves traveling in arbitrary directions on a sample. Coupling the easy scanning of ultrasound propagation with time-resolved detection of the surface-wave amplitude makes this method particularly suited to examining anisotropic materials. The first section of this thesis deals with surface waves on crystals and other homogeneous solids. The general theory describing surface-wave behavior on anisotropic materials is adapted to our technique. In anisotropic materials, two types of surface waves, designated Rayleigh surface waves and pseudo-surface waves, satisfy the boundary conditions for a free surface. The experimental design is then described, and images obtained on a variety of crystalline samples are examined. Discrepancies between the calculations and the observed results have led to an investigation of the effects of fluid loading on the surface waves. It is found that coupling between the surface waves and the loading liquid will attenuate the propagating surface waves, with high frequencies showing stronger attenuation. In addition, the loading will affect the velocities of the surface waves, and in some cases will support additional surface-wave modes. The remainder of the thesis examines surface-wave propagation on a variety of periodic structures. Carbon-fiber/epoxy composites are first examined, and the elastic properties of a homogeneous sample are used to determine the surface-wave velocities of layered samples in the long-wavelength limit. Two systems are then examined in the dispersive regime, where the wavelength of the surface waves is comparable to the periodicity of the sample. The first, a multilayer sample constructed from layers of aluminum and a low-density polymer, has one-dimensional symmet…
author: Vines, Robert Ellsworth
language: en
keywords: surface acoustic waves, surface-wave propagation, anisotropic materials, periodic structures
date published: 2012-05-17T19:12:58Z
date modified: 2026-07-22T22:25:29Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois - Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/30859