Abstract
As a new type of acoustic metamaterial, the pentamode material has extensive application prospect in controlling acoustic wave propagation because of its fluid properties. Firstly, a kind of pentamode material unit cell is designed, which is a two-dimensional honeycomb truss structure. Then, the asymptotic homogenization method is used to calculate static parameters of the unit cell, and also the influence of the geometric parameters and material composition of the unit cell on its mechanical properties is studied. Besides, based on transformation acoustics and the design method of the cylindrical cloak proposed by Norris, an acoustic cloak with isotropic density and gradient elastic modulus is constructed by periodically assembling the unit cell to guide the wave to bypass obstacles. Finally, the full displacement field analysis is carried out to prove the stealth effect of the acoustic cloak.
Highlights
IntroductionFluctuation is a common way of energy transmission. As an example, mechanical vibration is an elastic wave propagating in mechanical structures
In natural, fluctuation is a common way of energy transmission
The pentamode materials are classified as a new kind of acoustic metamaterials, and the main characteristic is that the ratio of shear modulus to bulk modulus is very small, so the coupling of shear wave and expansion wave can be broken up
Summary
Fluctuation is a common way of energy transmission. As an example, mechanical vibration is an elastic wave propagating in mechanical structures. Exploring the relationship between materials and wave propagation has an extraordinary significance for practical engineering and scientific researches. Some researchers have been trying to design a kind of acoustic cloak with stealth effect. Researchers mainly study the acoustic cloak based on inertial materials with isotropic stiffness and anisotropic density[1]. In order to overcome the problem, Norris proposes to use pentamode materials with anisotropic stiffness and isotropic density to design[2]. The pentamode materials have become an ideal choice for controlling the propagation path of acoustic waves. Aiming at unit cells of the pentamode materials or the two-dimensional honeycomb truss structures, the asymptotic homogenization method is applied to explore
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