A low-frequency sound-absorbing and broadband impact-resistant superstructure and its design method

Abstract

The present invention discloses a low-frequency sound-absorbing and broadband impact-resistant superstructure and a design method thereof, comprising: using a plurality of impact-resistant sound-absorbing units connected in sequence; the impact-resistant sound-absorbing units include two panels made of pressure-resistant composite materials, an impact-resistant lattice structure and a damping layer containing cavities, and a plurality of unit arrays are arranged to constitute a low-frequency sound-absorbing and broadband impact-resistant superstructure. A panel is provided at both the upper and lower ends of the damping layer, and the impact-resistant lattice structure is provided within the damping layer. The lattice structure is a simple cube of a hexahedral rod unit, including twelve rods with square cross-sections, and a rectangular frame composed of four upper and lower cross bars connects the upper and lower panels respectively. The design requires determining the impact load and sound absorption index, determining the material, and determining the size. The advantages of the present invention are: improving the overall mechanical properties, having high impact resistance, light weight, and excellent sound absorption performance.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic metamaterials, and in particular to a low-frequency sound-absorbing and broadband impact-resistant superstructure and a design method thereof. Background Art

[0002] In recent years, acoustic cladding technology has been key to achieving acoustic stealth for underwater vehicles, and the study of its acoustic properties has become a hot research area. With the advent of the concept of acoustic metamaterials, numerous acoustic metamaterials / structures with unique physical properties have emerged. However, due to the complexity and specificity of underwater sound wave propagation, the application of acoustic metamaterials in underwater sound absorption and insulation is limited, and research is relatively limited. Although underwater sound-absorbing structures designed using acoustic metamaterials can achieve a certain sound absorption effect in the low-frequency range, the resulting sound absorption band is relatively narrow, making it difficult to meet the acoustic technology requirements of underwater vehicles. Furthermore, to address the risk of underwater vehicles being attacked, improving their protective performance is particularly important, necessitating the continuous innovation and development of new impact-resistant protective structures. In summary, it is necessary to propose a metastructure design that combines sound absorption and impact resistance to meet the acoustic stealth and impact resistance requirements of underwater vehicles. Summary of the Invention

[0003] This invention addresses the shortcomings of existing technologies by providing a low-frequency sound-absorbing and broadband impact-resistant superstructure and its design method. By combining a rod lattice structure with sound-absorbing material, it replaces the traditional steel plate and sound-absorbing material structure. This balances mechanical and sound-absorbing properties, resolving the problems of the existing structure, such as its hydrostatic pressure resistance, impact resistance, and susceptibility to detachment.

[0004] In order to achieve the above object of the invention, the technical solution adopted by the present invention is as follows:

[0005] A low-frequency sound-absorbing and broadband impact-resistant superstructure, comprising a plurality of sequentially connected impact-resistant sound-absorbing units;

[0006] The impact-resistant sound-absorbing unit includes two panels made of pressure-resistant composite materials, an impact-resistant lattice structure and a damping layer containing cavities. Multiple unit arrays are arranged to form a low-frequency sound absorption and broadband impact-resistant superstructure.

[0007] A panel is arranged at both the upper and lower ends of the damping layer, and the impact-resistant lattice structure is arranged in the damping layer.

[0008] The lattice structure is a simple cube of hexahedral rod units, including twelve rods with square cross-sections, and a rectangular frame composed of four upper and lower horizontal rods connecting the upper and lower panels respectively.

[0009] Preferably, the panel is square with a side length of 30 to 50 mm and a thickness of 4 to 6 mm, and is made of fiberglass reinforced plastic or carbon fiber composite material.

[0010] Preferably, the cross-section side length of the rods of the lattice structure is 4 to 6 mm, and the rods are made of stainless steel, aluminum alloy or titanium alloy.

[0011] Preferably, the height of the lattice structure is 40 to 50 mm, and the width is consistent with the side length of the panel.

[0012] Preferably, the thickness of the damping layer is consistent with the distance between the upper and lower panels, and is made of rubber or polyurethane.

[0013] Preferably, a cylindrical cavity is provided in the upper and lower parts of the damping layer that contact the panel respectively. The height of the cavity is consistent with the side length of the rod of the lattice. The bottom surface of the cavity is the inscribed circle of the rectangular frame composed of the horizontal bars of the lattice structure. The cavity is formed by digging grooves in the contact surface of the upper and lower ends of the damping layer with the panel, and then covering the panel.

[0014] The present invention also discloses a design method of the above-mentioned low-frequency sound absorption and broadband impact resistance superstructure, which comprises the following steps:

[0015] S1: Determine the impact load faced by the low-frequency sound absorption and broadband impact resistance superstructure, and the sound absorption index to be achieved;

[0016] S2: Determine the materials used for the components of the low-frequency sound absorption and broadband impact resistance superstructures, and obtain constitutive equations for all material types;

[0017] S3: Determine the size of each component of the low-frequency sound absorption and broadband impact resistance superstructure according to the impact type and sound absorption index.

[0018] S4: Restore the finite element model of the low-frequency sound absorption and broadband impact resistance superstructure through numerical simulation, perform mechanical and acoustic calculations, and obtain parameters that best meet actual requirements.

[0019] Furthermore, in step S1, the impact of the underwater explosion is used as a reference as the impact load.

[0020] Furthermore, in step S1, underwater sound absorption and sound insulation are used as references as sound absorption indicators.

[0021] Furthermore, in step S2, the material constitutive equations of the components can be obtained through experiments.

[0022] The pathways include:

[0023] Commonly used metals and plastics are obtained from the corresponding material library.

[0024] If there is no ready-made constitutive equation for the selected material, it is necessary to conduct experiments on the material to obtain the material properties and use tensile tests to obtain the constitutive equation.

[0025] Furthermore, in step S4, the numerical simulation includes the following steps:

[0026] S41: Use SolidWorks software to model the impact-resistant sound-absorbing unit;

[0027] S42: Import Hypermesh software for meshing;

[0028] S43: Substitute the material constitutive equations collected in S2 into each model in Ls-Dyna software or Abaqus software, add the impact load determined in S1, perform numerical simulation, simulate the impact process of the impact-resistant sound-absorbing unit, perform parametric analysis on the geometric dimensions of each component, and select the optimal geometric parameters of each component.

[0029] S44 uses Comsol software to simulate and calculate the sound absorption coefficient, perform parametric analysis on the geometric dimensions of each component, and select the optimal geometric parameters of each component. The sound absorption coefficient calculation is based on the transfer matrix theory. The normal sound pressure p between the adjacent i-th layer medium and the i+1-th layer medium is z and normal vibration velocity u z The relationship between them is represented by a transfer matrix.

[0030] Furthermore, the transfer matrix in S44 is as follows:

[0031]

[0032] Where, ρ i is the density of medium i, c i is the speed of sound in medium i, k iL is the longitudinal wave number in medium i, d i is the thickness of medium i, A i is the transfer matrix of a single-layer medium, is the sound pressure in medium i+1, is the vibration velocity in medium i+1;

[0033] The pressure and vibration velocity at the interface between adjacent media are continuous, and the transfer matrix A i Perform cumulative multiplication to obtain the transfer matrix of the multi-layer medium, i.e., the multi-layer structure:

[0034]

[0035] Where A is the total transfer matrix. is the sound pressure in the last layer of the multilayer medium, is the vibration velocity in the last layer of the multilayer medium, a 11 、a 12 、a 21 、a 22 is the element of the transfer matrix A, n is the number of layers of the multilayer medium;

[0036] The incident input impedance of the sound wave is:

[0037]

[0038] Where Z out is the transmission end impedance, expressed as

[0039]

[0040] Under the hard backing condition, the particle vibration velocity is 0, that is, Z out →∞. Under soft backing conditions, the sound pressure is 0, that is, Z out →0. Then the sound pressure reflection coefficient R is

[0041]

[0042] When the backing is hard or soft, the transmission coefficient T→0, and the sound absorption coefficient is expressed as:

[0043] α=1-|R| 2

[0044] Where R is the sound pressure reflection coefficient.

[0045] Compared with the prior art, the advantages of the present invention are:

[0046] The damping layer is a viscoelastic material such as rubber or polyurethane, which plays a major role in sound absorption in the structure. The rod lattice serves as the main load-bearing element to improve the overall mechanical properties.

[0047] The rod lattice structure consists of twelve rod units, all made of alloy materials, which use the higher stiffness and excellent toughness of metal to provide high impact resistance.

[0048] The panel is made of carbon fiber or fiberglass reinforced composite materials, taking advantage of the high rigidity and strength of composite materials; the thickness of the panel is 4 to 6 mm, and the weight is reduced as much as possible while meeting the rigidity and strength conditions.

[0049] The damping layer is made of rubber or polyurethane viscoelastic material, and the thickness of the damping layer is 40 to 50 mm, ensuring that the weight is reduced as much as possible while having a certain sound absorption effect.

[0050] Holes are opened in the damping layer to create a cylindrical cavity that fits the panel, and the vibration bending of the damping layer is used to further improve the sound absorption performance.

[0051] It has excellent mechanical properties. When the impact factor is 1.0, the maximum deformation is only 6mm, which meets the impact resistance requirements of underwater structures.

[0052] The invention has good underwater sound absorption performance. The simulation model of the test piece can achieve a sound absorption coefficient of more than 0.7 within a certain range of 1700 to 6000 Hz, and the sound absorption peak value at some positions can reach more than 0.9.

[0053] The panel thickness, damping layer thickness, material properties, lattice rod width, cavity diameter, and position of the sound-absorbing structure proposed in this invention are all adjustable parameters that can be reasonably selected and adjusted based on specific usage scenarios, such as requirements for mechanical properties or acoustic performance.

[0054] In summary, the present invention has excellent mechanical properties and good underwater sound absorption performance. In terms of design, it has more adjustable parameters, including structural parameters and material parameters, which can be adjusted accordingly according to actual working conditions. It has a simple structure and is easy to manufacture. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of a low-frequency sound absorption and broadband impact-resistant superstructure according to an embodiment of the present invention;

[0056] Figure 2 A schematic diagram of a model subjected to impact load according to an embodiment of the present invention;

[0057] Figure 3 This is a displacement diagram of the maximum deformation of the impact surface when the embodiment of the present invention is subjected to an impact load;

[0058] Figure 4 Schematic diagram of the sound absorption coefficient within 0-7000 Hz of an embodiment of the present invention;

[0059] Figure 5 The present invention is a flowchart of a method for designing an embodiment of the present invention.

[0060] In the figure: 1. Panel; 2. Matrix structure; 3. Damping layer; 4. Cavity. DETAILED DESCRIPTION

[0061] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0062] In the description of the present invention, it should be understood that the terms "center," "longitudinal," "lateral," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "one side," "one end," and "one side" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, in the description of the present invention, unless otherwise specified, "a plurality" means two or more.

[0063] like Figure 1 As shown, the present invention provides a low-frequency sound absorption and broadband impact resistance superstructure, comprising: a panel 1, a lattice structure 2, and a damping layer 3. The panel 1 comprises an upper and a lower panel with the same thickness. The damping layer 3 is arranged between the upper and lower panels 1, and the damping layer 3 contains a cavity 4. The lattice structure 2 is arranged in the damping layer 3, and its two ends are respectively connected to the upper and lower panels 1. The above combination forms a cell, and a plurality of cell arrays are arranged to constitute a low-frequency sound absorption and broadband impact resistance superstructure.

[0064] The panel 1 is made of glass fiber reinforced plastic composite material or carbon fiber composite material, and has a thickness of 4 to 6 mm.

[0065] The lattice structure 2 is made of titanium alloy or aluminum alloy. The height of the lattice structure 2 is 40-50 mm and the width is 30-50 mm.

[0066] The lattice structure 2 is a simple cube of hexahedral rod units, including twelve rods with square cross-sections, and a rectangular frame composed of four upper and lower horizontal rods connecting the upper and lower panels respectively.

[0067] The damping layer 3 is made of viscoelastic material rubber or polyurethane, has a Young's modulus of 6 to 15 MPa, a loss factor greater than 0.3, and its thickness and width are determined by the size of the lattice structure 2 .

[0068] The present invention comprises a lattice structure, a viscoelastic damping layer, and embedded scatterers. Its mechanical properties are primarily determined by the lattice structure, including the diameter and length of the lattice diagonal rods, and the thickness of the panel. Sound absorption performance is primarily determined by factors such as the thickness, Young's modulus, and loss factor of the damping layer, and the size and position of the embedded cavity. Because these material and structural parameters are adjustable, they can be adjusted to meet the corresponding mechanical or acoustic requirements. The following describes the technical solution of the present invention through specific embodiments.

[0069] Materials for the examples:

[0070] Carbon fiber composite material: its characteristic density is 1320kg / m3 , Young's modulus 42.7GPa, Poisson's ratio 0.485.

[0071] Rubber: Its characteristic is density 1100kg / m 3 , Young's modulus 6~15MPa, Poisson's ratio 0.49, and equivalent isotropic loss factor 0.3.

[0072] Titanium alloy: its characteristic density is 4500kg / m 3 , Young's modulus 123GPa, Poisson's ratio 0.3, yield strength 932MPa.

[0073] Water: Its characteristic is its density of 1000 kg / m 3 , the speed of sound is 1500m / s.

[0074] Example structure size selection:

[0075] The panel thickness is 6mm, the lattice height is 45mm, the lattice rod width is 4.5mm, and the cavity radius is 18mm.

[0076] like Figure 2 As shown, the impact resistance simulation model used in the embodiment of the present invention is a cylindrical array of cells, the impact factor is 1.0, and the acoustic-solid coupling algorithm is used to verify the impact resistance performance of the present invention under underwater conditions.

[0077] like Figure 3 As shown, the deflection curve at the maximum deformation of the impact surface of the embodiment of the present invention first increases and then decreases, and the peak value does not exceed 6mm, which proves that the impact resistance of the present invention is very good.

[0078] like Figure 4 As shown, the structure with symmetrical cavities and a reinforced frame can effectively absorb sound wave energy within a certain frequency range. At low frequencies, sound waves excite bending vibrations on the cavity surface, changing the direction of sound wave propagation and thus improving absorption of sound wave energy. The peak at high frequencies is primarily due to the lattice structure. The bending vibrations of the rear panel and core layer cause the sound waves to transform into waveforms, resulting in excellent sound absorption even at high frequencies.

[0079] The sound absorption coefficient of the embodiment is greater than 0.7 at 1700-6000 Hz, and reaches a maximum value at 5000 Hz, with the maximum value of the sound absorption coefficient being 0.98.

[0080] It can be seen from the simulation results that the present invention can achieve good sound absorption performance within a certain frequency range, and the acoustic performance can be adjusted by setting different structural parameters.

[0081] like Figure 5As shown, a method for designing a low-frequency sound-absorbing and broadband impact-resistant superstructure provided by an embodiment of the present invention includes the following steps:

[0082] S1: determining the impact load faced by the low-frequency sound absorption and broadband impact resistance superstructure, and the sound absorption coefficient to be achieved;

[0083] S2 determining the materials used for the components of the low-frequency sound absorption and broadband impact resistance superstructures, and obtaining constitutive equations for all material types;

[0084] S3 determines the size of each component of the low-frequency sound absorption and broadband impact resistance superstructure according to the load and sound absorption index.

[0085] S4 restores the finite element model of the low-frequency sound absorption and broadband impact-resistant superstructure through numerical simulation, performs mechanical and acoustic calculations, and thus obtains the parameters that best meet actual requirements.

[0086] In step S1 , the impact of underwater explosion is mainly used as the impact type referenced by the low-frequency sound absorption and broadband impact-resistant superstructure.

[0087] In step S1, underwater sound absorption and sound insulation are mainly used as reference acoustic coefficients for evaluating the environment for the low-frequency sound absorption and broadband impact-resistant superstructure.

[0088] In step S2, the material constitutive equations of each component can be obtained through experiments or other methods. The methods include: for commonly used metals and plastics, Ansys and Altair have corresponding material libraries containing stress-strain curves and various parameters, which have been made into solver files and can be directly used. If the selected material does not have a ready-made constitutive equation, it is necessary to conduct experiments on the material to obtain the material properties. The materials selected in the present invention are mostly common isotropic elastic-plastic materials, and the constitutive equation is usually obtained by tensile testing.

[0089] In step S3, the size design should be repeatedly verified, taking into account acoustic performance, mechanical performance and lightweight.

[0090] In step S4, the numerical simulation includes the following steps:

[0091] S41 uses SolidWorks software to model the impact-resistant sound-absorbing unit.

[0092] S42 imports Hypermesh software for mesh division

[0093] S43 substitutes the material constitutive model collected by S2 into each model in Ls-Dyna software or Abaqus software, adds the impact load determined by S1, performs numerical simulation, simulates the impact process of the impact-resistant and sound-absorbing unit, performs parametric analysis on the geometric dimensions of each component, and selects the optimal geometric parameters of each component.

[0094] S44 uses Comsol software to simulate and calculate the sound absorption coefficient, perform parametric analysis on the geometric dimensions of each component, and select the optimal geometric parameters of each component. The sound absorption coefficient calculation is based on the transfer matrix theory. The normal sound pressure p between the adjacent i-th layer medium and the i+1-th layer medium is z and normal vibration velocity u z The relationship between can be expressed by the transfer matrix, that is,

[0095]

[0096] Where, ρ i is the density of medium i, c i is the speed of sound in medium i, k iL is the longitudinal wave number in medium i, d i is the thickness of medium i, A i That is the transfer matrix of a single-layer medium. The pressure and vibration velocity at the interface between adjacent media are continuous, and the transfer matrix A i By multiplying, we can get the transfer matrix of multi-layer medium or multi-layer structure:

[0097]

[0098] Where A is the total transfer matrix. The incident input impedance of the acoustic wave is

[0099]

[0100] Where Z out is the transmission end impedance, expressed as

[0101]

[0102] Under the hard backing condition, the particle vibration velocity is 0, that is, Z out →∞. Under soft backing conditions, the sound pressure is 0, that is, Z out →0. Then the sound pressure reflection coefficient R is

[0103]

[0104] When the backing is hard or soft, the transmission coefficient T→0, and the sound absorption coefficient can be expressed as:

[0105] α=1-|R| 2

[0106] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the implementation methods of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the present invention.

Claims

1. A low-frequency sound absorption and broadband impact resistance superstructure, characterized by: It includes a plurality of anti-impact and sound-absorbing units connected in sequence; The impact-resistant sound-absorbing unit includes two panels made of pressure-resistant composite materials, an impact-resistant lattice structure, and a damping layer containing cavities. Multiple unit arrays are arranged to form a low-frequency sound absorption and broadband impact-resistant superstructure. A panel is provided at both the upper and lower ends of the damping layer, and the impact-resistant lattice structure is provided in the damping layer; The lattice structure is a simple cube of hexahedral rod units, consisting of twelve rods with square cross-sections, and a rectangular frame composed of four upper and lower crossbars connecting the upper and lower panels respectively; A cylindrical cavity is set in the upper and lower parts of the damping layer that contact the panel respectively. The height of the cavity is consistent with the side length of the lattice rod. The bottom surface of the cavity is the inscribed circle of the rectangular frame composed of the horizontal bars of the lattice structure. The cavity is formed by digging grooves on the contact surface of the upper and lower ends of the damping layer with the panel, and then covering the panel.

2. The low-frequency sound absorption and broadband impact-resistant superstructure according to claim 1, characterized in that: The panel is square with a side length of 30 to 50 mm and a thickness of 4 to 6 mm, and is made of fiberglass or carbon fiber composite material panels.

3. The low-frequency sound-absorbing and broadband impact-resistant superstructure according to claim 1, characterized in that: The side length of the cross section of the rod of the lattice structure is 4 to 6 mm, and it is made of stainless steel, aluminum alloy or titanium alloy. The height of the lattice structure is 40 to 50 mm, and the width is 30 to 50 mm.

4. The low-frequency sound absorption and broadband impact-resistant superstructure according to claim 1, characterized in that: The thickness of the damping layer is consistent with the distance between the upper and lower panels and is made of rubber or polyurethane.

5. A method for designing a low-frequency sound-absorbing and broadband impact-resistant superstructure according to any one of claims 1 to 4, comprising the following steps: S1: Determine the impact load faced by the low-frequency sound absorption and broadband impact resistance superstructure, and the sound absorption index to be achieved; S2: Determine the materials used for the components of the low-frequency sound absorption and broadband impact resistance superstructures, and obtain constitutive equations for all material types; S3: Determine the size of each component of the low-frequency sound absorption and broadband impact resistance superstructure according to the impact type and sound absorption index; S4: Restore the finite element model of the low-frequency sound absorption and broadband impact resistance superstructure through numerical simulation, perform mechanical and acoustic calculations, and obtain parameters that best meet actual requirements.

6. The design method according to claim 5, characterized in that: In step S1 , the impact of the underwater explosion is used as a reference as the impact load, and the underwater sound absorption and sound insulation are used as a reference as the sound absorption index.

7. The low-frequency sound-absorbing and broadband impact-resistant superstructure according to claim 5, characterized in that: In step S2, the material constitutive equations of the components are obtained through an experimental approach; the experimental approach includes: For commonly used metals and plastics, obtain them from the corresponding material library; If there is no ready-made constitutive equation for the selected material, it is necessary to conduct experiments on the material to obtain the material properties and use tensile tests to obtain the constitutive equation.

8. The low-frequency sound-absorbing and broadband impact-resistant superstructure according to claim 5, characterized in that: In step S4, the numerical simulation includes the following steps: S41: Use SolidWorks software to model the impact-resistant sound-absorbing unit; S42: Import Hypermesh software for meshing; S43: Substitute the material constitutive equations collected in S2 into each model in Ls-Dyna software or Abaqus software, add the impact load determined in S1, perform numerical simulation, simulate the impact process of the impact-resistant sound-absorbing unit, perform parametric analysis on the geometric dimensions of each component, and select the optimal geometric parameters of each component; S44 uses Comsol software to simulate and calculate the sound absorption coefficient, conducts parametric analysis on the geometric dimensions of each component, and selects the optimal geometric parameters of each component; the sound absorption coefficient calculation is based on the transfer matrix theory, and the normal sound pressure p between the adjacent i-th layer medium and the i+1-th layer medium is z and normal vibration velocity u z The relationship between them is represented by a transfer matrix.

9. The low-frequency sound-absorbing and broadband impact-resistant superstructure according to claim 8, characterized in that: The transfer matrix in S44 is as follows: Where, ρ i is the density of medium i, c i is the speed of sound in medium i, k iL is the longitudinal wave number in medium i, d i is the thickness of medium i, A i is the transfer matrix of a single-layer medium, is the sound pressure in medium i+1, is the vibration velocity in medium i+1; The pressure and vibration velocity at the interface between adjacent media are continuous, and the transfer matrix A i Perform cumulative multiplication to obtain the transfer matrix of the multi-layer medium, i.e., the multi-layer structure: Where A is the total transfer matrix; is the sound pressure in the last layer of the multilayer medium, is the vibration velocity in the last layer of the multilayer medium, a 11 、a 12 、a 21 、a 22 is the element of the transfer matrix A, n is the number of layers of the multilayer medium; The incident input impedance of the sound wave is: Where Z out is the transmission end impedance, expressed as Under the hard backing condition, the particle vibration velocity is 0, that is, Z out →∞; Under soft backing conditions, the sound pressure is 0, that is, Z out →0; then the sound pressure reflection coefficient R is When the backing is hard or soft, the transmission coefficient T→0, and the sound absorption coefficient is expressed as: α＝1-|R| 2 Where R is the sound pressure reflection coefficient.

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