Phononic crystals and acoustic metamaterials exhibit unique wave propagation properties rising from periodicity and the heterogeneity in material/structure design. One important property is tailoring the propagation of elastic waves from band gaps in such systems – frequency ranges of strong wave attenuation. This thesis first explores the idea of gaining control over the band gap frequencies through intentionally buckling of thin silicon strips made structures. We explored the effect of buckling as well as post-buckling strain softening properties of silicon strips. And we used numerical analysis to show the evolution of band gap frequency, fully accounting for the effect of nonlinear deformation. An explicit method is employed to show the wave propagation behavior subject to mechanical tuning, opening avenues for the design of adaptive wave filter or switches. In addition, we report on the topological insulation properties of phononic crystals, distinguishing the differences between a trivial defect mode and a topologically protected valley mode. A continuum structure that use soft pillars and beams as building blocks, was designed with a band structure that has a two-fold degeneracy at lower frequency and four-fold degeneracy at higher frequency Dirac points. The coexistence of such degeneracies was exploited to achieve the mechanical analogue of Quantum Valley Hall Effect and Quantum Spin Hall Effect in the same lattice design. We demonstrated the waveguiding behavior through numerical simulations. The considered design defines a framework for the implementation of topological concepts on continuum structures for potential engineering applications.

Creator

• Han, Jialun

DOI

• https://doi.org/10.21985/n2-ztnt-4z44

Subject

• Mechanics
• Civil engineering

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:14471
• etdadmin_upload_627248

Date created

• 2018-01-01

Resource type

• Dissertation

Rights statement

• In Copyright