Akanji, Omololu (2015) Sound bullets from nonlinear granular chains. PhD thesis, University of Warwick.

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Abstract

The propagation of ultrasound along chains of granular particles has some interesting characteristics. These have the potential to dramatically improve the performance of HIFU (High Intensity Focussed Ultrasound) for the use in therapeutic ultrasound treatments and medical imaging. This thesis has investigated a novel approach for the creation of ultrasonic focussed energy in chains composed of spheres. Within these highly sensitive chains, non-linear propagation is possible which leads to the formation of highly robust localised pulses known as sound bullets. Subject to the right conditions, the chain of spheres become a dynamically tunable system where slight changes to the nature of the Herzian contact between the spheres produce drastic changes in the propagation velocity of the solitary wave. The nature and resulting characteristics of the system to variations such as input excitation frequency, effect of loading, changes in length and diameter of the chain were studied. It was observed that the system was highly dependent of each of these factors, with each situation altering the behaviour of the chain of spheres.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Library of Congress Subject Headings (LCSH):	Ultrasonic waves, High-intensity focused ultrasound
Official Date:	September 2015
Dates:	Date Event September 2015 Submitted
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Hutchins, David A.
Extent:	xxiii, 182 leaves : illustrations, charts
Language:	eng

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