Sound bullets from nonlinear granular chains

Doctoral thesis English OPEN
Akanji, Omololu
  • Subject: TA
    mesheuropmc: sense organs

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.
  • References (12)
    12 references, page 1 of 2

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    1. D.A. Hutchins, J. Yang, O. Akanji, P. J. Thomas, L.A.J. Davis, S. Freear, S. Harput, N. Saffari and P. Gelat, (2014, September). The study of chain-like materials for use in biomedical ultrasound. In Ultrasonics Symposium (IUS), 2014 IEEE International (pp. 2607-2610). IEEE.

    2. D.A. Hutchins, J. Yang, O. Akanji, P. J. Thomas, L.A.J. Davis, S. Freear, S. Harput, N. Saffari and P. Gelat, (2015). “Evolution of ultrasonic impulses in chains of spheres using resonant excitation), EPL, 109, 54002.

    3. D.A. Hutchins, J. Yang, O. Akanji, P. J. Thomas, L.A.J. Davis, S. Freear, S. Harput, N. Saffari and P. Gelat, (2015). Evolution of ultrasonic impulses in chains of spheres using resonant excitation. EPL (Europhysics Letters), 109(5), 54002.

    4. J. Yang, D. A. Hutchins, O. Akanji, P. J. Thomas, L. A. J. Davis, S. Harput, P. Gelat, S. Freear, and N. Saffari, (2015). An analysis of solitary wave impulses in granular chains using ultrasonic excitation. [Accepted August 2015 for publication in Physics Procedia].

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