Research On The Design And Properties Of A 3D Space Coiling Acoustic Metamaterial

Acoustic metamaterial is a kind of artificial composite with intriguing acoustic physical properties,which has wide application potentials in various industries and defenses.In this thesis,a spherical metamaterial structure based on space coiling is designed,and its acoustic characteristics are systematically analyzed and studied through theoretical analysis,FEM simulation and experimental verification.The main contents of this study include:Firstly,a 3D space coiling acoustic metamaterial ball is designed based on the analysis of physical properties of acoustic metamaterial.This novel 3D structure originates from the regular icosahedron with the high symmetry,consisting of 20 identical tetrahedral.The tetrahedral evolves to the cone with a three-dimensional zigzag channel.The resulting metamaterial ball with isotropic characteristics is established by 3D modeling software and manufactured by 3D printing technique.Secondly,a series of numerical analysis is carried out by imputing the model into the finite element software,including eigenstate analysis,extraction of equivalent parameters,calculation of transmission coefficient in different azimuth,simulation of various functions and the parameter study on sound insulation.Finally,to verify the theoretical analysis and simulation,the experimental study of metamaterial ball is conducted.The complex transmission coefficient,complex reflection coefficient and equivalent parameters of the metamaterial ball are measured based on the method of four microphones with impedance tube.The experiment results are compared with the simulation results,and they agree well with each other.Importantly,the proposed 3D metamaterial ball in this paper demonstrates two important resonances,monopole and dipole resonances,with negative equivalent bulk modulus and negative equivalent mass density near monopole and dipole,respectively;and this particular property characterizes as three dimensional isotropy.The proposed structure can be used for blocking the noise,sound cloaking and acoustic tunneling.Combined with the tunability of the structure,it will have great application potential in engineering.