Topics in diffuse field ultrasonics

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2020

Author dc:creator

• Yoritomo, John Yukio

Contributors dc:contributor

• Weaver, Richard L
• Dahmen, Karin
• Popovics, John
• Grosse Perdekamp, Matthias

• Ultrasonics
• Acoustics
• Physical Acoustics
• Elastodynamics
• 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

Statement dc:rights

• Copyright 2020 John Y. Yoritomo. All rights reserved.

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/108218

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/108218