阅读说明：本技术 一种可调声超材料及包括该可调声超材料的波导模式转换器 (tunable ultrasonic metamaterial and waveguide mode converter comprising same ) 是由 王振 吴大建 许恒毅 魏琦 于 2019-10-25 设计创作，主要内容包括：本发明提供了一种可调声超材料及包括所述可调声超材料的波导模式转换器。所述可调声超材料包括若干304不锈钢四棱柱散射体和铝板,所述304不锈钢四棱柱散射体沿垂直于铝板方向嵌套在铝板中；其中,相邻的4个304不锈钢四棱柱散射体组成一个单胞结构,所述单胞结构在铝板表面且呈周期性排列。通过四棱柱散射体沿平行于铝板方向上的倾斜角度的灵活调控,可以实现声超材料的拓扑相变。通过分层结构的设计,可以在较宽带隙范围内有选择的激发弹性体-边界-角模式。本发明的可调拓扑声学复合波导结构结合了声超构材料能带计算与拓扑相变理论。(The invention provides adjustable acoustic metamaterial and a waveguide mode converter comprising the same, wherein the adjustable acoustic metamaterial comprises a plurality of 304 stainless steel quadrangular scatterers and an aluminum plate, the 304 stainless steel quadrangular scatterers are embedded in the aluminum plate along the direction vertical to the aluminum plate, each 4 adjacent 304 stainless steel quadrangular scatterers form unit cell structures, the unit cell structures are arranged on the surface of the aluminum plate periodically, the topological phase change of the acoustic metamaterial can be realized through the flexible regulation and control of the inclination angles of the quadrangular prism scatterers along the direction parallel to the aluminum plate, and an elastomer-boundary-angle mode can be selectively excited in a wider band gap range through the design of a layered structure.)

The tunable acoustic metamaterial comprises a plurality of 304 stainless steel quadrangular scatterers and aluminum plates, wherein the 304 stainless steel quadrangular scatterers are embedded in the aluminum plates along the direction perpendicular to the aluminum plates, wherein unit cell structures are formed by 4 adjacent 304 stainless steel quadrangular scatterers, and the unit cell structures are arranged on the surfaces of the aluminum plates periodically.

2. The tunable acoustic metamaterial according to claim 1, wherein 4 304 stainless steel quadrangular diffusers that constitute unit cell structures are nested in an aluminum plate in a 2 x 2 arrangement, and the 4 304 stainless steel quadrangular diffusers are centrosymmetric.

3. The tunable acoustic metamaterial according to any one of claims 1-2 to , wherein the distance between adjacent 2 304 stainless steel quadrangular diffusers in a unit cell structure is a/2, where a is 25 μm.

4. The tunable acoustic metamaterial according to any of claims 1-3, wherein the distance between two adjacent unit cell structures is a-25 μm.

5. The tunable acoustic metamaterial according to any of claims 1-4, wherein straight lines are provided on the surface of the aluminum plate, and the 304 stainless steel quadrangular diffuser is adjustable in a direction perpendicular to the aluminum plate within a range of-45 ° to 50 °, such as-25 °, -45 °, and 50 °.

6. The tunable acoustic metamaterial according to any of claims 1-5, wherein the surface of the aluminum plate is provided with straight lines, the angle between the 1 304 stainless steel quadrangular diffuser forming unit cell structures and the straight line in the direction perpendicular to the aluminum plate is-25 °, the angle between the adjacent 1 304 stainless steel quadrangular diffuser and the straight line in the direction perpendicular to the aluminum plate is 50 °, or the angle between the 1 304 stainless steel quadrangular diffuser forming unit cell structures and the straight line in the direction perpendicular to the aluminum plate is-45 °, and the angle between the adjacent 1 304 stainless steel quadrangular diffuser and the straight line in the direction perpendicular to the aluminum plate is 45 °.

7. The tunable acoustic metamaterial according to of claims 1-6, wherein the unit cell structures are arranged in a two-dimensional 20 x 20-30 x 30 periodic arrangement, such as a two-dimensional 22 x 22 periodic arrangement, on the surface of the aluminum plate.

8. The tunable acoustic metamaterial according to any of claims 1-7 and , wherein the 304 stainless steel quadrangular diffuser has a density of 7903Kg/m³Young's modulus 219e9Pa, poisson's ratio 0.32;

the length, width and height of the 304 stainless steel quadrangular diffuser are 0.35a,0.15a and 0.35a respectively, wherein a is 25 mu m, and the lattice constant is the same as the length, width and height of the stainless steel quadrangular diffuser.

9. The tunable sonometamaterial according to any one of claims 1-8 to , wherein the aluminum sheet has a density of 2700Kg/m³Young's modulus of 70e9Pa, Poisson's ratio of 0.34;

the thickness of the aluminum plate is 0.4a, where a ═ 25 μm, which is the lattice constant.

10, waveguide mode converter comprising the tunable acoustic metamaterial of any of claims 1-9 to .

Technical Field

The invention relates to adjustable acoustic metamaterials with periodically-changed elastic modulus, in particular to flexibly-adjustable topological acoustic conversion circuits.

Background

In the traditional acoustic integrated device, improvement of signal fidelity and signal-to-noise ratio of a system is the focus of attention of researchers, but most of acoustic signals are scattered by defects in the acoustic device due to processing precision errors and interference of environmental noise, and meanwhile, the environmental noise can cover target signals needing to be measured.

The elastic body metamaterial is formed by compounding scatterers with elastic modulus and density changing along with periodicity, the lattice structure with translational periodicity can cause elastic energy to be distributed in a band shape due to Bragg scattering, the elastic energy corresponding to band gap frequency cannot be transmitted in the material, the propagation of sound waves can be effectively regulated and controlled by using the material, and the solving method of the elastic phonon energy band mainly comprises a plane wave expansion method and a multiple scattering method.

Due to the periodic lattice structure, parameters such as density, Lame constant and displacement in the elastomer wave equation can be expanded in the form of plane waves in the reciprocal lattice vector space, so that the solution of the partial differential equation is converted into the solution process of characteristic values in the characteristic equation.

In the elastic wave system, the wave equation is of the form:

the parameters of the Lame constant, the density and the like are periodic functions of a space vector R in the reciprocal lattice vector space, and satisfy the form of a system :

f(r+R)＝f(r) (2)

wherein r is [ x y z ] in the formula (2)]^T. Due to the periodic lattice structure, the function f (r) can be expanded in a fourier series:

since the periodicity of the lattice structure satisfies the bloch boundary condition, the solution of the displacement in formula (1) can be expressed as:

if equations (3) and (4) are substituted into the elastic wave fluctuation equation (1), the fluctuation equation can be expanded into a matrix form:

wherein:

wherein: g₃＝G₁+G₂(ii) a i. j and l are x, y and z. In formula (6), G₂And G₃The entire reciprocal lattice vector space can be traversed. If G is₂And G₃Take N points in the reciprocal lattice vector space, then equation (5) can be expanded into equations of 3N × 3N:

at this time, the solution process of the wave equation displacement is converted into the solution of the eigenvector in the characteristic equation, and the solution process of the equation (7) is essentially the solution matrix N^-1The solution of equation (7) can obtain the resonant frequency ω corresponding to each wave losses k in the reciprocal lattice vector space, i.e. the elastic propertyEnergy bands of the phononic crystal.

Solving the wave equation of elastic waves using the th principle, i.e., the unit cell shape of the daughter crystal of equation (7), is shown in the inset of fig. 1(a-c), and the corresponding elastic wave dispersion is shown in fig. 1 (d-f). full-wave calculations were performed by the th principle.

Disclosure of Invention

The above state of the art is analyzed in consideration of signal distortion and low signal-to-noise ratio caused by scattering of elastic energy in the conventional acoustic integrated device. Unilateral improvement in processing accuracy and environmental noise improvement have great limitations on improving the performance of conventional acoustic devices. The invention skillfully utilizes the topological energy band theory in condensed state physics to optimize the structural design of the traditional acoustic integrated device and improves the signal-to-noise ratio of the acoustic integrated device from the perspective of physical principles.

In order to achieve the purpose, the invention adopts the technical scheme that:

types of adjustable sound metamaterial, which comprises a plurality of 304 stainless steel quadrangular scatterers and aluminum plates, wherein the 304 stainless steel quadrangular scatterers are embedded in the aluminum plates along the direction perpendicular to the aluminum plates, wherein 4 adjacent 304 stainless steel quadrangular scatterers form unit cell structures, and the unit cell structures are arranged on the surfaces of the aluminum plates periodically.

According to the invention, 4 304 stainless steel quadrangular diffusers constituting unit cell structures are nested in an aluminum plate in a 2 × 2 arrangement, and the 4 304 stainless steel quadrangular diffusers are centrosymmetric.

According to the invention, the distance between the adjacent 2 304 stainless steel quadrangular diffusers in the unit cell structure is a/2, wherein a is 25 μm.

According to the invention, the distance between two adjacent unit cell structures is 25 μm.

In the invention, the nesting means that the 304 stainless steel quadrangular scattering body penetrates through the aluminum plate.

According to the invention, straight lines were provided on the surface of the aluminum plate, and the 304 stainless steel quadrangular diffuser was adjustable in the range of-45 to 50 from this line in the direction perpendicular to the aluminum plate, for example, -25, -45 and 50.

Illustratively, straight lines are arranged on the surface of the aluminum plate, the included angle between the 1 304 stainless steel quadrangular diffuser forming unit cell structures and the straight line in the direction perpendicular to the aluminum plate is-25 degrees, the included angle between the adjacent 1 other 304 stainless steel quadrangular diffuser forming unit cell structures and the straight line in the direction perpendicular to the aluminum plate is-45 degrees, and the included angle between the adjacent 1 other 304 stainless steel quadrangular diffuser forming unit cell structures and the straight line in the direction perpendicular to the aluminum plate is 45 degrees.

According to the invention, the unit cell structures are arranged in two dimensions of 20 × 20 to 30 × 30 periods, for example 22 × 22 periods, on the surface of the aluminum plate.

According to the invention, the density of the 304 stainless steel quadrangular diffuser is 7903Kg/m³Young's modulus 219e9Pa, Poisson's ratio 0.32.

According to the invention, the length, width and height of the 304 stainless steel quadrangular diffuser are respectively 0.35a,0.15a and 0.35a, wherein a is 25 μm, and the lattice constant is shown.

According to the invention, the density of the aluminium sheet is 2700Kg/m³Young's modulus was 70e9Pa, and Poisson's ratio was 0.34.

According to the invention, the thickness of the aluminum plate is 0.4a, where a ═ 25 μm, which is the lattice constant.

The invention also provides waveguide mode converters comprising the tunable acoustic metamaterial described above.

In the invention, th principle calculation is carried out on the converter, in order to ensure the calculation accuracy, the maximum grid size is 1/10 of a lattice constant in the calculation process, the three-dimensional model has 500000 degrees of freedom, a solid mechanics calculation module is used in the calculation, theoretically, an elastic wave fluctuation equation is solved through th principle full wave, and the energy band distribution of the elastic wave metamaterial in an inverted lattice vector space is obtained, and steps are carried out, and the absorption boundary conditions are adopted around the waveguide structure to prevent additional boundary modes in a band gap from being generated.

The invention also provides a preparation method of the adjustable sound metamaterial, which comprises the following steps:

the adjustable sound metamaterial is prepared in a metal 3D printing mode.

The invention has the beneficial effects that:

the invention provides tunable sonoultrasonic materials and a waveguide mode converter comprising the tunable sonoultrasonic materials, wherein the topological phase change of the sonoultrasonic materials can be realized by flexibly regulating and controlling the inclination angle of a quadrangular prism scatterer along the direction parallel to an aluminum plate, and an elastomer-boundary-angle mode can be selectively excited in a wider band gap range through the design of a layered structure.

Drawings

FIG. 1 is a schematic diagram of the unit cell structure and band diagram of the tunable acoustic metamaterial of the present invention.

FIG. 2 is a projected band diagram of the tunable sonometamaterial of the present invention.

FIG. 3 is a performance test chart of the tunable acoustic metamaterial according to the present invention.

FIG. 4 shows the defective immune characteristics of the tunable acoustic metamaterial according to the present invention.

FIG. 5 is a performance test chart of the tunable acoustic metamaterial waveguide mode converter of the present invention.

Detailed Description

The preparation method of the present invention will be further described in with reference to specific examples, it should be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention.