Abstract
Unidirectional/asymmetric transmission of acoustic/elastic waves has recently been realized by linear structures. Research related to unidirectionality of wave propagation has received intense attention due to potentially transformative and unique wave control applications. However, asymmetric transmission performance in existing devices usually occurs only in a narrow frequency band, and the asymmetric frequencies are always within ultrasound range (above 20 kHz). In this work, we design and propose a linear diatomic elastic metamaterial using dual-resonator concept to obtain large asymmetric elastic wave transmission in multiple low frequency bands. All of these frequency bands can be theoretically predicted to realize one-way wave propagation along different directions of transmission. The mechanisms of multiple asymmetric transmission bands are theoretically investigated and numerically verified by both analytical lattice and continuum models. Dynamic responses of the proposed system in the broadband asymmetric transmission bands are explored and analyzed in time and frequency domains. The effect of damping on the asymmetric wave transmission is further discussed. Excellent agreements between theoretical results and numerical verification are obtained.
Highlights
Inspired by the remarkable development and extensive application of electrical diode, much effort has been devoted to challenge the one-way propagation of other forms of energy fluxes, such as electromagnetic/optical field[1,2,3], thermal flux[4,5,6] and solitary wave[7]
Based on the frequency conversion induced by nonlinear mediums and the filter effect of bandgap phononic crystals, the acoustic time-reversal symmetry is broken, resulting in nonreciprocal wave propagation
It is worth noting that in all of these passive linear structures, the acoustic reciprocity principle still holds and asymmetric transmission only occurs under specific directions or wave modes
Summary
Inspired by the remarkable development and extensive application of electrical diode, much effort has been devoted to challenge the one-way propagation of other forms of energy fluxes, such as electromagnetic/optical field[1,2,3], thermal flux[4,5,6] and solitary wave[7]. To overcome the application challenge in small wavelengths, this approach of fluid-motion-induced biasing was further replaced by an angular-momentum-induced biasing[14, 15] These biased linear devices can realize asymmetric wave transmission without distorting the wave frequency, but external energy is needed. Based on surficial localized vibrational modes, a linear diatomic metamaterial with large asymmetric wave transmission is realized[23]. We propose a linear diatomic acoustic/elastic metamaterial with dual resonator to realize large asymmetric wave transmission in multiple low frequency bands. These asymmetric transmission bands (ATBs) belong to different propagation directions, which are bi-directional tunable. Considering that damping is an intrinsic property of materials, we further investigate the asymmetric wave transmission in a dissipative diatomic system
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