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Title:Topics in diffuse field ultrasonics
Author(s):Yoritomo, John Yukio
Director of Research:Weaver, Richard L
Doctoral Committee Chair(s):Dahmen, Karin
Doctoral Committee Member(s):Popovics, John; Grosse Perdekamp, Matthias
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Physical Acoustics
Elastic Waves
Diffuse fields
Diffuse field theory
Diffuse field ultrasonics
diffuse ultrasound
Wave physics
Green's function retrieval
seismic interferometry
passive imaging
spurious arrivals
enhanced backscatter
dynamical Anderson localization
dynamical localization
axisymmetric elastic bodies
slow dynamics
slow dynamic nonlinearity
non-classical nonlinear elasticity
nonlinear acoustics
coda wave interferometry
granular media
resonant transmission
glass bead packs
thermal activation
Abstract:Random wave fields that have explored large volumes over long times contain much information. Studying these diffuse fields and extracting the information contained in them are the primary aims of Diffuse Field Theory. When the waves of interest are elastic waves at frequencies above 20kHz, the subject can be called Diffuse Field Ultrasonics. Here, three topics of Diffuse Field Ultrasonics are presented. The first concerns the identification of the Green’s function with the cross-correlation produced from a diffuse wave field. This has been termed Green’s Function Retrieval. Of particular concern is the accurate retrieval of amplitude when the wave field fails to be fully diffuse. The second topic involves the study of diffuse fields in nearly axisymmetric elastic bodies. The distribution of energy within such a body and subsequent transport is predicted and then compared with experimental measurements on an aluminum cylinder with a hole in its side. Appeals to Enhanced Backscatter and Dynamical Anderson Localization are needed for full agreement of theory and experiment. The third topic is Slow Dynamics, a remarkable non-classical nonlinear elastic behavior found in a wide-range of materials that possess a cracked microstructure and at various length scales. Two new experimental venues and a variety of preliminary studies are presented in the hope of elucidating the micro-physics behind slow dynamics. Before discussing these three topics, the concept of a diffuse field is introduced. The conclusion summarizes the central results of each preceding chapter.
Issue Date:2020-01-29
Rights Information:Copyright 2020 John Y. Yoritomo. All rights reserved.
Date Available in IDEALS:2020-08-27
Date Deposited:2020-05

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