Abstract null null Broadband attenuation of low frequency acoustic waves in compact structure designs is a challenging issue, especially in the application to seismic waves. In this work, we propose a new seismic metamaterial constituted by a combination of two different attenuating structures, namely pillars above the ground and core-shell inclusions embedded in the soil. As compared to the two constituting parts, this structure enables us to broaden the bandgap while shifting it towards lower frequencies. Additionally, the analysis of the symmetry of the excited Rayleigh wave and the eigenmodes in the dispersion curves reveal that the frequency range of efficient wave attenuation in transmission is much wider than that of the corresponding bandgap. Finally, gradient combined metamaterial is designed to achieve wave attenuation in a broadband range of [4.3, 20.0] Ηz while the unit cell size keeps compact, of the order of 2 m. The results show practical and economic applications in ground surface vibration isolation to protect large infrastructures or civil engineering architectures.
Last. Yingjing Liang(GU: Guangzhou University)H-Index: 5
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Abstract In this work, we numerically investigate topological interface states for subwavelength in-plane waves in elastic metamaterials composed mainly of translational resonators. The relationships among bandgap, effective mass and effective stiffness are analyzed for the mass-spring and continuum models. Besides, the locations of stop-bands and negative effective parameters are manipulated by tuning the parameters of translational resonances. It is observed that the topological phase transiti...
In this paper, we investigate the acoustic flatbands (FBs) in phononic crystal (PnC) defect lattices. The defects are introduced into a PnC composed of periodic rigid rods in the air background. Since the acoustic energy is highly confined inside the PnC defects, the interaction between the defects can be described by the tight-binding model. We construct the PnC defects in two bipartite lattices, namely, the stub and Lieb lattices. The acoustic FBs can be observed for both of the lattices. More...
The development of seismic metamaterials has attracted much research interest in the past decade. Efforts have been made by using experimental and theoretical approaches to isolate buildings and structures susceptible to elastic surface wave damage. However, most seismic metamaterials were designed without considering the viscoelastic effect that widely exists in nature. In this work, we investigate the propagation and attenuation of the Rayleigh and pseudo surface waves (PSWs) in two types of v...
Last. Weiqiu Chen(ZJU: Zhejiang University)H-Index: 57
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Topological insulators have attracted intensive attention due to their robust properties of path defect immunity, with diverse applications in electromagnetic, acoustic, and elastic systems. The recent development of elastic topological insulators (ETIs), based on artificially structured phononic crystals, has injected new momentum into the manipulation of elastic waves. Earlier ETIs with unreconfigurable geometry and narrow frequency bandgaps hinder the exploration and design of adaptable devic...
Last. Timon Rabczuk(Bauhaus University, Weimar)H-Index: 101
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Abstract The mechanical analog to the topological insulators brings anomalous elastic wave properties which diversifies classic wave functions for potential broad applications. To obtain topological mechanical wave states with good quality at desired frequency ranges, it needs repetitive trials of different geometric parameters with traditional forward designs. In this work, we develop an inverse design of topological edge states for flexural wave using machine learning method which is promising...
ABSTRACT Elastic metamaterials with local resonance bandgaps are promising for low-frequency vibration mitigation. However, such locally resonant metamaterials inherently possess narrow bandgap width, and are usually achieved by multi-material structures, which are difficult to fabricate, limiting their potential in engineering practice. Here, we present a class of 3D single-phase elastic metamaterials exhibiting both locally resonant and Bragg scattering bandgaps. The local resonance of the sin...
We study numerically the potential of a multimodal elastic metamaterial to filter and guide Lamb waves in a plate. Using a sub-wavelength array of elongated beams attached to the plate, and combining the coupling effects of the longitudinal and flexural motion of these resonators, we create narrow transmission bands at the flexural resonances of the beams inside the wide frequency bandgap induced by their longitudinal resonance. The diameter of the beams becomes the tuning parameter for selectio...
The introduction of engineered resonance phenomena on surfaces has opened a new frontier in surface science and technology. Pillared phononic crystals, metamaterials, and metasurfaces are an emerging class of artificial structured media, featuring surfaces, that consist of pillars-or branching substructures-standing on a plate or a substrate. A pillared phononic crystal exhibits Bragg band gaps while a pillared metamaterial may feature both Bragg band gaps and local-resonance hybridization band ...
We consider the effect of an array of plates or beams over a semi-infinite elastic ground on the propagation of elastic waves hitting the interface. The plates/beams are slender bodies with fle-xural resonances at low frequencies able to perturb significantly the propagation of waves in the ground. An effective model is obtained using asymptotic analysis and homogenization techniques , which can be expressed in terms of the ground alone with effective dynamic (frequency-dependent) boundary condi...
Last. Yue-Sheng Wang(Beijing Jiaotong University)H-Index: 60
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Abstract The invisible cloak has attracted great attention due to its significant influences on science and engineering. Active elastic wave metamaterials provide superior controllable characteristics for the flexural wave cloak that is obviously different from the conventional structure. In this work, a broadband flexural wave cloak is designed and fabricated by the coordinate transformation method and active control system. The cloaking configuration consists of 16 alternative concentric layer...