Metamaterials and mechanical structures capable of passive acoustic wave redirection could allow unusual behaviour such as unidirectional sound transmission, enhanced acoustic isolation, and improved shocks mitigation. In this work, a carefully designed 2D nonlinear lattice is experimentally constructed to exhibit passive energy redirection following the Landau-Zener Tunnelling (LZT) in space. The metastructure consists of two nonlinear chain-like lattices coupled laterally by linear springs. Each of the two lattices is composed of a series of linear oscillators (unit-cells) with essential nonlinear couplers. One lattice is referred to as the ‚Äúexcited lattice‚Äù (forced by an impulse) and the other is referred to as the ‚Äúabsorbing lattice‚Äù (that is not directly forced). Based on a previous analytical study, the energy can be passively redirected from the excited to the absorbing lattice, an effect analogous to the LZT that originated in quantum mechanics in the context of linear parametric oscillators (in time). The realization of this effect necessitates linear coupling between the two lattices and spatial variation of the grounding stiffnesses in the excited lattice from its second unit-cell onward. Nonlinear coupling between the unit-cells within the same lattice allow for redirected energy to transfer irreversibly into the absorbing lattice in the form of a travelling breather (solitary wave). This system nonlinearity provides acoustic tunability (self-adaptiveness) with the excitation level resulting in three observed response regimes: energy localization in the first unit-cells of the two lattices for low excitation level, the intended LZT energy redirection for moderate excitation level, and energy localization in the excited lattice for large excitation level. Optimized designs, manufacturing and assembly procedures of the system‚Äôs components resulted in good agreement between the experiments and the model‚Äôs simulations. Particularly, these applied experimental practices reduced the setup‚Äôs damping allowing the formation and the visualization of the breather traveling through the metastructure. 

Experimental Realization of Passive Wave Redirection in a 2D Nonlinear Lattice due to Landau-Zener Tunnelling in Space

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