A pressure-resistant broadband sound-absorbing anisotropic superstructure

Abstract

The present application provides a pressure-resistant broadband sound-absorbing anisotropic superstructure, comprising an impedance matching layer and a pressure-resistant sound-absorbing layer, wherein the impedance matching layer is attached above the pressure-resistant sound-absorbing layer; the pressure-resistant sound-absorbing layer is composed of M×N microstructure units embedded in a matrix material and periodically arranged along the x-direction; the microstructure unit size is composed of an upper frame, a lower frame, an upper connecting beam, a lower connecting beam, and a central unit, and a certain inclination angle between the upper and lower frames and the upper and lower connecting beams is maintained to ensure that the unit structure has various anisotropies to achieve mode conversion of sound waves. The operating frequency of the superstructure can be changed according to the size parameters of the microstructure unit and the parameters of the matrix material. By adjusting the material parameters of the matrix material and the microstructure unit, the deformation of the structure under high hydrostatic pressure can be reduced, thereby improving the mechanical bearing performance.

Description

Technical Field

[0001] The invention relates to the technical field of vibration noise control, in particular to a pressure-resistant broadband sound-absorbing anisotropic superstructure. Background Art

[0002] Currently, sonar detection technology is evolving toward low-frequency, broadband, and high-power technologies. Its positioning accuracy, detection range, and recognition precision are constantly improving, which in turn requires ever-increasing acoustic stealth capabilities. Acoustic materials reduce the reflection of incident waves, allowing them to penetrate as far as possible into the structure and dissipating the energy of the incident waves to the greatest extent possible, thereby minimizing the likelihood of detection by active sonar. However, existing acoustic materials are no longer sufficient to counteract this evolving sonar detection technology, necessitating the development of new stealth materials.

[0003] Underwater acoustic metamaterials, with their unusual acoustic properties, offer a novel approach to stealth technology. The field is currently experiencing rapid development, with a variety of novel properties and functions emerging as research deepens. However, traditional underwater acoustic metamaterials are limited by high hydrostatic pressure, resulting in narrow operating bandwidths and poor sound absorption. Summary of the Invention

[0004] In view of this, the present invention provides a pressure-resistant broadband sound-absorbing anisotropic superstructure, which is composed of an impedance matching layer, a matrix material, and microstructure units. The impedance matching layer is laid on the sound-absorbing structure composed of the matrix material and the microstructure units. Under high water pressure conditions, the matrix material is embedded in the microstructure units to enhance the structure's ability to resist pressure deformation. While maintaining excellent mechanical bearing properties, it is also necessary to have outstanding broadband and efficient sound absorption performance. When sound waves pass through the covering layer and smoothly enter the sound-absorbing structure, they are continuously scattered and reflected during propagation. A portion of the sound waves is converted from longitudinal waves to transverse waves through waveform conversion, while another portion consumes energy through resonance, further increasing the dissipation of sound energy. This effectively solves the problem in the prior art of being unable to balance broadband sound absorption and insufficient resistance to hydrostatic pressure.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention provides a pressure-resistant broadband sound-absorbing anisotropic superstructure, comprising an impedance matching layer and a pressure-resistant sound-absorbing layer, wherein the impedance matching layer is attached to the pressure-resistant sound-absorbing layer;

[0007] The pressure-resistant sound-absorbing layer is composed of M×N microstructure units embedded in a matrix material and arranged periodically along the x direction;

[0008] The size of the single microstructure unit is h × h, and it is composed of an upper frame, a lower frame, an upper connecting beam, a lower connecting beam, and a central unit. The upper connecting beam is used to connect and support the upper frame and the central unit, and the lower connecting beam is used to connect and support the lower frame and the central unit.

[0009] Furthermore, the upper and lower frames are both concave structures;

[0010] Furthermore, the upper and lower connecting beams are trapezoidal structures;

[0011] Furthermore, the central unit is a rectangular structure;

[0012] Furthermore, the upper frame is composed of a first bending portion, a second bending portion and a first connecting portion in the middle; the lower frame is composed of a third bending portion, a fourth bending portion and a second connecting portion in the middle;

[0013] Furthermore, the thickness of the impedance matching layer is m, the length of the pressure-resistant sound-absorbing layer is k, which is determined by the number of arranged microstructure units, the thickness is n, and the stretched length along the y direction is t;

[0014] Furthermore, the length k, thickness n, and stretch length t can be determined according to actual usage;

[0015] Furthermore, the size parameters of the microstructure unit can be varied from d1 to d 16 , H1, H2 indicate that the size parameters satisfy the following relationship:

[0016]

[0017] Wherein, d1 is the outer length of the first bending portion of the upper frame, d2 is the width of the first bending portion of the upper frame, d5 is the outer length of the second bending portion of the upper frame, d6 is the width of the second bending portion of the upper frame, and d9 is the width of the first connecting portion of the upper frame;

[0018] d3 is the width of the third bending portion of the lower frame, d4 is the outer length of the third bending portion of the lower frame, d7 is the outer length of the fourth bending portion of the lower frame, d8 is the width of the fourth bending portion of the lower frame, d 10 is the width of the second connecting portion of the lower frame;

[0019] d 13 is the length of the lower base of the upper connecting beam, d 16 is the upper bottom length of the upper connecting beam, d 14 is the upper bottom length of the lower connecting beam, d 15 is the length of the lower bottom surface of the lower connecting beam;

[0020] d 11 d 12is the length and width of the center unit, H1 and H2 are the offset distances of the center unit in the x and y directions;

[0021] Furthermore, the size parameters of the microstructure units are all adjustable parameters;

[0022] Furthermore, the two included angles θ1 and θ2 at the connection between the upper connecting beam and the upper frame, and the two included angles θ3 and θ4 at the connection between the lower connecting beam and the lower frame, are obtained by the following formulas:

[0023]

[0024] Furthermore, the width and length of the impedance matching layer are the same as those of the pressure-resistant sound-absorbing layer;

[0025] Furthermore, the base material and the impedance matching layer are made of non-metallic materials, and the microstructure unit is made of metallic materials;

[0026] Furthermore, the non-metallic material is one of PDMS and rubber;

[0027] Furthermore, the metal material is one of aluminum alloy and titanium alloy;

[0028] Furthermore, the microstructure unit is manufactured using 3D printing or wire cutting technology.

[0029] The present invention adopts the above technical solution, which has at least the following beneficial effects:

[0030] 1. The structure of the present invention has excellent broadband sound absorption capacity and resistance to hydrostatic pressure deformation. Under a hydrostatic pressure of 5 MPa, the average sound absorption coefficient of the structure of the present invention reaches above 0.9 in the broadband frequency range of 4000 to 10000 Hz, and the sound absorption coefficient is higher than 0.8, which has the ability to maintain efficient broadband sound absorption under high hydrostatic pressure.

[0031] 2. The structure of the present invention uses mathematical means to perform multi-objective optimization on the sound-absorbing structure, thereby improving calculation efficiency and shortening the design cycle.

[0032] 3. The structural unit of the present invention is compact and stable and can be widely used in various load-bearing and sound-absorbing structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A stereoscopic diagram of a pressure-resistant, broadband, sound-absorbing anisotropic superstructure provided by the present invention;

[0034] Figure 2 A cross-sectional view of a pressure-resistant, broadband, sound-absorbing anisotropic superstructure provided by the present invention;

[0035] Figure 3A cross-sectional view of a microstructure unit in a pressure-resistant, broadband, sound-absorbing anisotropic superstructure provided by the present invention;

[0036] Figure 4 The sound absorption curve of Example 1 of a pressure-resistant broadband sound-absorbing anisotropic superstructure provided by the present invention under a pressure of 5 MPa;

[0037] Figure 5 This is the sound absorption curve of Example 2 of a pressure-resistant broadband sound-absorbing anisotropic superstructure provided by the present invention under a pressure of 5 MPa; DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below in conjunction with specific embodiments, clearly and completely describing the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] It should be noted that when a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component. The terms "top", "bottom", "upper", "lower", "left", "right", "front", "back", and similar expressions used herein are for illustrative purposes only.

[0040] The following embodiments of the present application are described in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0041] like Figure 1-2 As shown, the present invention proposes a pressure-resistant broadband sound-absorbing anisotropic superstructure, comprising an impedance matching layer 1 and a pressure-resistant sound-absorbing layer, wherein the impedance matching layer 1 is attached above the pressure-resistant sound-absorbing layer; wherein the thickness of the impedance matching layer 1 is m, and the characteristic impedance Z=Z 水 =ρ 水 c 水 The pressure-resistant sound-absorbing layer is composed of M×N microstructure units embedded in the matrix material 2 and arranged periodically along the x direction. Its length is k, which is determined by the number of arranged microstructure units. Its thickness is n. The microstructure unit is stretched along the y direction, and the stretching length is t.

[0042] The incident direction of the sound wave is above the impedance matching layer 1, and enters the interior of the pressure-resistant sound-absorbing layer through the impedance matching layer. At the same time, the impedance matching layer is in contact with the external water area to withstand water pressure; the impedance matching layer is laid on the pressure-resistant sound-absorbing layer composed of a matrix material and a microstructure unit. Under high water pressure conditions, the ability of the structure to resist pressure deformation can be improved by embedding the matrix material inside the microstructure unit; when the sound wave enters the interior of the pressure-resistant sound-absorbing layer through the impedance matching layer, it is continuously scattered and reflected. A part of it is converted from a longitudinal wave to a shear wave through waveform conversion, and the other part will consume energy through resonance, further increasing the dissipation of sound energy, thereby achieving the effect of consuming the incident sound energy.

[0043] like Figure 3 As shown, the size of a single microstructure unit is h×h, and it consists of an upper frame 3, a lower frame 4, an upper connecting beam 5, a lower connecting beam 6 and a central unit 7, wherein the upper and lower frames are both concave structures, consisting of bent portions at both ends and a connecting portion in the middle; the two connecting beams are both trapezoidal structures, and the central unit 7 is a rectangular structure.

[0044] Specifically, the microstructure unit size parameters include:

[0045] The outer length d1 of the first bending portion of the upper frame 3, the width d2 of the first bending portion of the upper frame 3, the outer length d5 ​​of the second bending portion of the upper frame 3, the width d6 of the second bending portion of the upper frame 3, and the width d9 of the first connecting portion of the upper frame 3;

[0046] The third bending portion width d3 of the lower frame 4, the outer length d4 of the third bending portion of the lower frame 4, the outer length d7 of the fourth bending portion of the lower frame 4, the fourth bending portion width d8 of the lower frame 4, the second connecting portion width d 10 ;

[0047] The length d of the bottom surface of the upper connecting beam 5 13 , the upper bottom length of the upper connecting beam is d 16 ; The upper bottom surface length d of the lower connecting beam 6 14 , the length of the lower bottom surface of the lower connecting beam is d 15 ;

[0048] Length d of the central unit 7 11 , width d 12 The center unit 7 has an x-direction offset distance H1 and a y-direction offset distance H2.

[0049] The microstructure unit size parameters satisfy the following relationship:

[0050]

[0051] The upper connecting beam 5 is used to connect the upper frame 3 and the central unit 7, and the lower connecting beam 6 is used to connect the lower frame 4 and the central unit 7; a certain inclination angle is required between the upper connecting beam 5 and the upper frame 3, and between the lower connecting beam 6 and the lower frame 4 to maintain the anisotropy of the unit structure and realize the mode conversion of the sound wave.

[0052] The two included angles θ1 and θ2 at the connection between the upper connecting beam 5 and the upper frame 3 and the two included angles θ3 and θ4 at the connection between the lower connecting beam 6 and the lower frame 4 are obtained by the following formula:

[0053]

[0054] For the two-dimensional case, the stress-strain relationship can be obtained using Hook's law:

[0055]

[0056] in, 、 Represents the principal strains in the x-direction and z-direction, and the calculation formula is 、 ; represents the shear strain in the xz plane, and the calculation formula is ; 、 、 Represents principal stress and shear stress; elastic tensor ( ) represents the coupling between the x (z) direction and the shear deformation; represents the coupling amount of deformation in the x and z directions; 、 represents the relationship between strain and stress along the direction; Represents the relationship between shear strain and stress.

[0057] The microstructure unit has strong anisotropy, and its elastic matrix C satisfies , which can realize the mode conversion of sound waves;

[0058] To ensure that the sound waves can enter the sound absorption structure smoothly, an impedance matching layer is attached to the upper surface of the microstructure unit, with a thickness of m and the same width and length as the microstructure unit;

[0059] The impedance matching layer 1 and the base material 2 are made of PDMS or rubber. The upper frame 3, the lower frame 4, the upper connecting beam 5, the lower connecting beam 6, and the central unit 7 are made of aluminum alloy or titanium alloy.

[0060] The microstructure units are manufactured using processes such as 3D printing or wire cutting.

[0061] The operating frequency of the pressure-resistant broadband anisotropic superstructure of the present invention changes according to the size parameters of the microstructure unit and the parameters of the matrix material, showing its potential for broadband sound absorption;

[0062] By adjusting the material parameters of the matrix material and the microstructure unit, the deformation of the structure under high hydrostatic pressure can be reduced and the mechanical bearing performance can be improved.

[0063] The following examples using different parameters are given to further illustrate the present invention.

[0064] Example 1

[0065] This embodiment provides a pressure-resistant, broadband, sound-absorbing anisotropic superstructure. The impedance matching layer 1 has a thickness of m = 2.5 mm, and the pressure-resistant sound-absorbing layer has a thickness of n = 2.0 mm. The upper frame 3 and lower frame 4, upper connecting beam 5 and lower connecting beam 6, and central unit 7 of the microstructure unit are made of titanium alloy TC4. The microstructure unit is integrally cut using wire cutting technology. Material parameters are: elastic modulus E = 110 GPa, Poisson's ratio = 0.34, density ρ = 4500 kg / m3, and yield strength 980 MPa.

[0066] The size parameters of the microstructure unit are h=10mm, d1=5.3mm, d2=2.3mm, d3=2.1mm, d4=2.5mm, d5=4.6mm, d6=3.1mm, d7=3.9mm, d8=1.8mm, d9=1mm, d 10 =1.7mm, d 11 =1.8mm, d 12 =1.2mm, d 13 =0.5mm, d 14 =0.5mm, d 15 =0.5mm, d 16 =0.7mm.

[0067] The angles between the connecting beam and the frame are θ1=35°, θ2=55°, θ3=50°, and θ4=47°, and the offset distances of the central unit are H1=0 mm and H2=0.1 mm.

[0068] The material of the impedance matching layer 1 is rubber, and its material parameters are: elastic modulus E = 0.14 GPa, Poisson's ratio = 0.49, and density ρ = 950 kg / m 3 , the isotropic loss factor is 0.2.

[0069] The matrix material 2 is PDMS: elastic modulus E = 4.8 MPa, Poisson's ratio = 0.49, density ρ = 890 kg / m 3, the isotropic loss factor is 0.5. The simulation model is established by the acoustic-solid coupling module in the finite element simulation software to calculate the sound absorption performance. Figure 4 As shown, the calculation formula of the sound absorption coefficient α is:

[0070]

[0071] Where R is the reflection coefficient, T is the transmission coefficient, and p i is the incident sound wave, p r is the reflected sound wave, p t For transmitted sound waves. Under the condition of overall structure thickness of 4.5mm, the frequency range of incident sound waves is 4000Hz-10000Hz. Figure 4 As shown in the figure, when there is no hydrostatic pressure, the average sound absorption coefficient is 0.94; under a water pressure of 5 MPa, the maximum stress borne by the microstructure unit is 543 MPa, and the average sound absorption coefficient is 0.95.

[0072] Example 2

[0073] This embodiment provides a pressure-resistant, broadband, sound-absorbing anisotropic superstructure. The impedance matching layer 1 has a thickness of m = 2.0 mm, and the pressure-resistant sound-absorbing layer has a thickness of n = 2.0 mm. The upper frame 3 and lower frame 4, upper connecting beam 5 and lower connecting beam 6, and central unit 7 of the microstructure unit are made of aluminum alloy 7051. The microstructure unit is integrally cut using wire cutting technology. Material parameters are: elastic modulus E = 71 GPa, Poisson's ratio = 0.33, density ρ = 2700 kg / m3, and yield strength = 400 MPa.

[0074] The size parameters of the microstructure unit are h=10mm, d1=5mm, d2=2.5mm, d3=2.4mm, d4=3.7mm, d5=5mm, d6=2.5mm, d7=3.9mm, d8=2.7mm, d9=1.5mm, d10=1.4mm, d11=1.9mm, d12=1.5mm, d13=0.4mm, d14=0.3mm, d15=0.3mm, d16=0.4mm.

[0075] The angles between the connecting beam and the frame are θ1=32°, θ2=58°, θ3=34°, θ4=57°, and the center unit offset distances are H1=0.4mm and H2=0.9mm.

[0076] The material of the impedance matching layer 1 is rubber, and its material parameters are: elastic modulus E=140MPa, Poisson's ratio=0.49, density ρ=950 kg / m3, and isotropic loss factor of 0.2.

[0077] The matrix material 2 is PDMS: elastic modulus E = 2.5MPa, Poisson's ratio = 0.493, density ρ = 890kg / m3, isotropic loss factor is 0.5. The simulation model is established by the acoustic-solid coupling module in the finite element simulation software to calculate the sound absorption performance. Figure 5 As shown in the figure, under the condition of overall thickness of 4mm, the frequency range of incident sound waves is 4000Hz-10000Hz, and the average sound absorption coefficient is 0.95 without hydrostatic pressure; under 5MPa water pressure, the maximum stress borne by the microstructure unit is 341Mpa, and the average sound absorption coefficient is 0.97.

[0078] The working principle of the present invention is as follows: under a high hydrostatic pressure environment, the surface of the impedance matching layer can withstand the hydrostatic pressure and transfer the pressure to the internal pressure-resistant sound-absorbing layer. Since the internal filling material enhances the overall stiffness, the maximum stress it bears is much smaller than the yield strength of the structure, so the overall deformation is small, thereby ensuring the safety of the structure. When underwater sound waves are incident on the broadband sound-absorbing surface, since the surface impedance of the impedance matching layer is close to that of water, no obvious reflection phenomenon will occur at the interface in contact with water. Therefore, the vast majority of sound waves can carry the wave energy into the underwater broadband sound-absorbing anisotropic superstructure. The sound waves entering the underwater sound-absorbing metamaterial structure propagate in the form of longitudinal waves. Due to the tilting movement of the anisotropic superstructure in the pressure-resistant sound-absorbing layer, the impedance matching layer is driven to undergo lateral displacement and deformation, causing the original longitudinal wave to be converted into a transverse wave propagation, thereby losing part of the sound energy through the lateral movement of the impedance matching layer. Since the pressure-resistant sound-absorbing layer is filled with polymer elastomer, the vibration mode of the anisotropic superstructure will resonate with the polymer elastomer at a specific frequency, thereby further increasing the displacement deformation in the matrix material and consuming more wave energy in the underwater broadband sound-absorbing anisotropic superstructure.

[0079] The pressure-resistant broadband sound-absorbing anisotropic superstructure provided by the present invention effectively solves the problems of broadband high-efficiency underwater sound absorption and hydrostatic pressure resistance in the frequency range of 4000-10000 Hz. It can maintain high-efficiency broadband sound absorption under high hydrostatic pressure. In addition, mathematical methods can be combined to perform multi-objective optimization of the sound-absorbing structure, improving computational efficiency and shortening the design cycle. The geometric structure is compact and stable, and can be widely used in various load-bearing and sound-absorbing structures, with broad application prospects.

[0080] The above specific description further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pressure-resistant broadband sound-absorbing anisotropic superstructure, characterized in that: The device comprises an impedance matching layer and a pressure-resistant sound-absorbing layer, wherein the impedance matching layer is attached to the pressure-resistant sound-absorbing layer; the pressure-resistant sound-absorbing layer is composed of M×N microstructure units embedded in a matrix material and periodically arranged along the x-direction; the microstructure unit has a size of h×h and is composed of an upper frame, a lower frame, an upper connecting beam, a lower connecting beam, and a central unit; the upper connecting beam is used to connect and support the upper frame and the central unit, and the lower connecting beam is used to connect and support the lower frame and the central unit; The upper and lower frames are both concave structures, the upper and lower connecting beams are both trapezoidal structures, and the central unit is a rectangular structure; The upper frame is composed of a first bending portion, a second bending portion and a first connecting portion in the middle; the lower frame is composed of a third bending portion, a fourth bending portion and a second connecting portion in the middle; The size parameters of the microstructure unit are d1~d 16 , H1, H2 indicate that the size parameters satisfy the following relationship: Wherein, d1 is the outer length of the first bending portion of the upper frame, d2 is the width of the first bending portion of the upper frame, d5 is the outer length of the second bending portion of the upper frame, d6 is the width of the second bending portion of the upper frame, and d9 is the width of the first connecting portion of the upper frame; d3 is the width of the third bending portion of the lower frame, d4 is the outer length of the third bending portion of the lower frame, d7 is the outer length of the fourth bending portion of the lower frame, d8 is the width of the fourth bending portion of the lower frame, d 10 is the width of the second connecting portion of the lower frame; d 13 is the length of the lower base of the upper connecting beam, d 16 is the upper bottom length of the upper connecting beam, d 14 is the upper bottom length of the lower connecting beam, d 15 is the length of the lower bottom surface of the lower connecting beam; d 11 d 12 are the length and width of the center unit, H1 and H2 are the offset distances of the center unit in the x and y directions.

2. The pressure-resistant broadband sound-absorbing anisotropic superstructure according to claim 1, characterized in that: The thickness of the impedance matching layer is m, the length of the pressure-resistant sound-absorbing layer is k, which is determined by the number of arranged microstructure units, the thickness is n, and when stretched along the y direction, the stretched length is t.

3. The pressure-resistant broadband sound-absorbing anisotropic superstructure according to claim 1, characterized in that: The size parameters of the microstructure units are all adjustable parameters.

4. The pressure-resistant broadband sound-absorbing anisotropic superstructure according to claim 3, characterized in that: The two included angles θ1 and θ2 at the connection between the upper connecting beam and the upper frame, and the two included angles θ3 and θ4 at the connection between the lower connecting beam and the lower frame are obtained by the following formula: 。 5. The pressure-resistant broadband sound-absorbing anisotropic superstructure according to claim 2, characterized in that: The width and length of the impedance matching layer are the same as those of the pressure-resistant sound-absorbing layer.

6. The pressure-resistant broadband sound-absorbing anisotropic superstructure according to claim 5, characterized in that: The base material and the impedance matching layer are made of non-metallic materials, and the microstructure unit is made of metallic materials.

7. The pressure-resistant broadband sound-absorbing anisotropic superstructure according to claim 6, characterized in that: The non-metallic material is one of PDMS and rubber, and the metal material is one of aluminum alloy and titanium alloy.

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