Faculty Advisor or Committee Member

Konstantin A. Lurie, Advisor

Faculty Advisor or Committee Member

Suzanne L. Weekes, Advisor

Faculty Advisor or Committee Member

Mayer Humi, Committee Member

Faculty Advisor or Committee Member

Homer F. Walker, Committee Member

Faculty Advisor or Committee Member

Daniel Onofrei, Committee Member

Identifier

etd-050117-154941

Abstract

This work is a numerical and analytical study of wave motion through dynamic materials (DM). This work focuses on showing several results that greatly extend the applicability of the checkerboard focusing effect. First, it is shown that it is possible to simultaneously focus dilatation and shear waves propagating through a linear elastic checkerboard structure. Next, it is shown that the focusing effect found for the original €œperfect€� checkerboard extends to the case of the checkerboard with smooth transitions between materials, this is termed a functionally graded (FG) checkerboard. With the additional assumption of a linear transition region, it is shown that there is a region of existence for limit cycles that takes the shape of a parallelogram in (m,n)-space. Similar to the perfect case, this is termed a €œplateau€� region. This shows that the robustness of the characteristic focusing effect is preserved even when the interfaces between materials are relaxed. Lastly, by using finite volume methods with limiting and adaptive mesh refinement, it is shown that energy accumulation is present for the functionally graded checkerboard as well as for the checkerboard with non-matching wave impedances. The main contribution of this work was to show that the characteristic focusing effect is highly robust and exists even under much more general assumptions than originally made. Furthermore, it provides a tool to assist future material engineers in constructing such structures. To this effect, exact bounds are given regarding how much the original perfect checkerboard structure can be spoiled before losing the expected characteristic focusing behavior.

Publisher

Worcester Polytechnic Institute

Degree Name

PhD

Department

Mathematical Sciences

Project Type

Dissertation

Date Accepted

2017-05-01

Accessibility

Unrestricted

Subjects

Dynamic Materials, Energy accumulation, Characteristic focusing, Functionally graded material, Elastic wave propagation, Dilatation and shear waves, Finite volume methods, Computational analysis, Parallel computing, Wave equation

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