Abstract
The recent emergence of topological insulators in condensed matter physics has inspired analogous wave phenomena in mechanical systems. However, to date, the design of these mechanical systems has been limited mostly to discrete lattices or perforated structures. Here, we take a ubiquitous design of a bolted elastic plate and demonstrate that it can guide flexural waves crisply around sharp bends. We show that this continuum system eliminates unwanted in-plane plate modes and allows the manipulation of low-frequency flexural modes by exploiting the local resonance of the bolts. We report the existence of a pair of double Dirac cones near the resonant frequency of the bolts, one of which leads to the creation of a topological complete bandgap that forbids all the plate modes. These findings open new possibilities of managing multiple wave modes in elastic solids for applications in energy harvesting, impact mitigation, and structural health monitoring.
Highlights
The discovery of topological insulators in condensed matter physics has prompted a new notion of topology in association with the intrinsic dispersion behavior of a material[1,2]
We numerically investigate the opening of multiple topological bandgaps by manipulating the bolt arrangement on the plate, one of which is notably a complete bandgap that prevents the leakage of flexural waves into other modes
The plate is excited with a piezo actuator attached in the middle of the horizontal domain wall, and a laser Doppler vibrometer (LDV) scans the plate’s vibrations via a two-axis linear stage
Summary
The discovery of topological insulators in condensed matter physics has prompted a new notion of topology in association with the intrinsic dispersion behavior of a material[1,2] By using this concept, one can characterize the dispersion behavior of an infinite (i.e., “bulk”) material, which provides a tool to predict the response at the “boundaries” of a finite material. A natural question is whether there exists a way to manipulate elastic waves at low frequencies yet avoiding the wave leakage into other modes. Lowering the operating frequencies generally demands large lattice sizes due to the Bragg condition This can pose challenges especially under stringent size limitations of the wave medium. The efficient topological manipulation of low-frequency waves in elastic systems remains a formidable challenge to date
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