Dissertation
I. Harmonic Stress excitation of modes of solid objects II. Analysis and scattering of focused acoustic beams III. High frequency scattering by truncated solid cylinders
Doctor of Philosophy (PhD), Washington State University
01/2019
Handle:
https://hdl.handle.net/2376/111572
Abstract
This work covers three main topics. First is the excitation of elastic modes of solid object using localized harmonic stresses. Both radiation and Maxwell stresses were used as an exciting mechanism. These are analogous techniques taking advantage of either amplitude modulated focused acoustic fields or oscillating magnetic fields to produce harmonic stresses on various objects. The oscillation frequency and spatial location of the resulting stresses is tuned to selectively excite the elastic modes in various objects. This technique can be used to investigate the mode shape of the target, information that is not available with typical techniques like plane wave sonar. The second part of this work focuses on methods of describing, analytically, focused sound fields and the scattering of objects in these fields. Using a geometric propagation model close to the source of sound facilitates the calculation of expansion coefficients. The coefficients allow the focused sound field to be represented by a superposition of Bessel beams. We can use this representation to solve, analytically the scattering by spheres in a focused field. This description provides a frame work for future work in analytically describing the force on an object in a focused beam. The final part of this thesis discusses high frequency scattering by solid cylinders with material junction. Solid cylinders have enhanced back scattering associated with a merdional wave, a Rayleigh wave launched down the axis of the cylinder. We investigate how a material junction changes this back scattering signature. This change is investigated in the time, frequency, and image domains.
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Details
- Title
- I. Harmonic Stress excitation of modes of solid objects II. Analysis and scattering of focused acoustic beams III. High frequency scattering by truncated solid cylinders
- Creators
- Timothy Daniel
- Contributors
- Philip L Marston (Advisor)Fred Gittes (Committee Member)Matthew D Duez (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Physics and Astronomy, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 292
- Identifiers
- 99900581616501842
- Language
- English
- Resource Type
- Dissertation