Mechanical Engineering Graduate Seminar
October 30 @ 1:10 pm - 2:25 pm
An event every week that begins at 1:10 pm on Friday, repeating until November 20, 2020
Please join us on Friday, October 23, as we host a new faculty member in Mechanical Engineering at the University of Vermont, Dr. Jihong Ma. Below you’ll find details on the talk, entitled “Topological Mechanical Metamaterials.” The seminar starts at 1:10 pm on MS Teams (see Event Website for link to meeting).
Acousto-elastic metamaterials and phononic crystals are artificially architected materials endowed with the capability of mechanical wave manipulation. In recent years, endeavors have been made to achieve desired waveguiding properties in finite lattices by engaging edge states that are intrinsic to the unit cell topological invariants. The concept originates in the realm of quantum physics, in which, in addition to their bulk bandgap behavior, topologically-protected edge states are created to progressively close the bandgap and enables edge wave propagation robust against a wide range of perturbations.
In the first part of my talk, a special class of topological phenomena occurring in Maxwell lattices will be introduced. Although the static behavior of ideal topological Maxwell lattices has been extensively studied theoretically, experimental proofs of the concept carried out on physical specimens that are realizable via simple fabrication techniques such as cutting, molding, or printing have been rare. We experimentally reveal how the zero-energy floppy edge modes predicted for ideal configurations morph into finite-frequency dynamic phonon modes that localize at edges of the physical lattice without the entanglement of low-frequency acoustic bulk modes. The experiments provide unequivocal evidence of the existence of strong asymmetric wave transport regimes at finite frequencies.
Next, I will discuss the design of elastodynamic logic circuits with unconventional wave transport capabilities at optical phonon modes comprising non-trivial waveguiding interfaces involving valley-Hall edge states that are robust against back-scattering at corners. We provide a rationale for the observed phenomena that blends topological considerations and mechanistic arguments, and we offer a criterion for the proper selection of the junction characteristics that are conducive to non-trivial interface modes.