A Design Method of Pressure-Immune Underwater Low-Frequency Broadband Absorbing Sandwich Metamaterial

Abstract

The present invention discloses a design method for a pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial. First, the structure of the sound-absorbing sandwich metamaterial is designed, including an upper panel, a lower panel, and a core layer located between the upper panel and the lower panel. The core layer includes a viscoelastic material matrix, as well as reinforcing members and local resonators embedded inside the viscoelastic material matrix. Then, by introducing mechanical property parameters and acoustic property parameters, it is judged whether the structure meets the pressure-immune or low-frequency broadband sound-absorbing conditions, and by introducing coupling property parameters and coupling property parameter thresholds, it is judged whether the structure meets both the pressure-immune and low-frequency broadband sound-absorbing conditions at the same time. The sound-absorbing sandwich metamaterial designed by the present invention takes into account both the mechanical properties and acoustic properties of the structure. The structure designed by this method can obtain low-frequency broadband sound-absorbing ability while effectively resisting the deformation caused by hydrostatic pressure and the internal stress of the internal matrix, so as to maintain the sound-absorbing performance under normal pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater sound absorption structures, and in particular to a design method for a pressure-immune underwater low-frequency broadband sound absorption sandwich metamaterial. Background Art

[0002] Underwater vehicles such as submarines need to maintain a high degree of concealment during mission execution to avoid enemy detection and strikes. Good acoustic stealth performance will ensure that underwater vehicles are not easily detected by the enemy when performing missions in the deep ocean, thereby increasing the success rate and survivability of operations. With the development of underwater vehicles towards greater diving depths and quieter operation, composite structures with good mechanical and acoustic properties will become the future development trend of underwater acoustic stealth structures.

[0003] Although most current underwater acoustic structures have good sound absorption performance, their pressure resistance is poor. As the water pressure increases, the structure will undergo significant deformation, and the material parameters of the viscoelastic material in the structure will also change significantly after being compressed, so the sound absorption coefficient decreases sharply. Therefore, it is of practical significance and application value to design a pressure-immune underwater low-frequency broadband sound absorption sandwich metamaterial. Summary of the Invention

[0004] In view of the problem that the sound absorption coefficient of the existing underwater sound absorption structure significantly decreases with the increase of hydrostatic pressure, the present invention proposes a design method for a pressure-immune underwater low-frequency broadband sound absorption sandwich metamaterial. The structure designed by this method can obtain low-frequency broadband sound absorption ability while effectively resisting the deformation caused by hydrostatic pressure and the internal stress of the internal matrix, so as to maintain the sound absorption performance under normal pressure.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A design method for a pressure-immune underwater low-frequency broadband sound absorption sandwich metamaterial, the design method comprising the following steps:

[0007] S1. Conduct a structural design for the sound absorption sandwich metamaterial, including an upper panel, a lower panel, and a core layer located between the upper panel and the lower panel; the core layer includes a viscoelastic material matrix, as well as reinforcing members and local resonators embedded inside the viscoelastic material matrix, the upper end and the lower end of the reinforcing members are respectively in contact with the upper panel and the lower panel, and the local resonators and the reinforcing members are arranged in an alternating manner;

[0008] S2. Decompose the sound absorption sandwich metamaterial into a structure composed of a plurality of unit cells arranged periodically;

[0009] S3. Determine the types of the reinforcing members and the local resonators, and determine the material parameters and dimensional parameters of the upper panel, the lower panel, the viscoelastic material matrix, the reinforcing members, and the local resonators;

[0010] S4. In terms of mechanics, determine the maximum static pressure according to the actual conditions , and the maximum displacement threshold under the maximum static pressure ; in terms of acoustics, determine the measurement frequency range according to the actual conditions , and the average sound absorption coefficient standard within the measurement frequency range ;

[0011] S5. Calculate the maximum static pressure and the maximum displacement of a single cell , as well as the frequency range of the average sound absorption coefficient under normal pressure and the average sound absorption coefficient under the maximum static pressure through simulation; ;

[0012] S6. Introduce the mechanical property parameters and the acoustic property parameters , , ;

[0013] S7. Compare , with 0. If or , it means that the mechanical or acoustic performance of the structure does not meet the design requirements (the displacement should be less than the maximum displacement threshold and the average sound absorption coefficient within the measurement frequency range should be higher than the average sound absorption coefficient standard ). Re-enter S3 to improve the type of reinforcement members and / or local resonators, the material parameters of each part, and / or the size parameters; otherwise, enter S8;

[0014] S8. Introduce the coupling performance parameter and the coupling performance parameter threshold , where the coupling performance parameter is , is the weight coefficient of the mechanical property parameters, is the weight coefficient of the acoustic property parameters, and there is ;

[0015] S9. Compare with . If , it means that the designed structure does not simultaneously meet the pressure immunity and low-frequency broadband sound absorption conditions. Re-enter S3 to improve the type of reinforcement members and / or local resonators, the material parameters of each part, and / or the size parameters; if , it means that the designed structure simultaneously meets the pressure immunity and low-frequency broadband sound absorption conditions.

[0016] In the above solution, the types of the reinforcing members include grid corrugated plates, and the dimensional parameters thereof include the grid plate thickness and the included angle between the grid plates. The local resonators are arranged within the grids. The types of the reinforcing members also include upright cylindrical lattices, and the dimensional parameter thereof includes the lattice diameter. The upright cylindrical lattices are uniformly distributed around the local resonators.

[0017] In the above solution, the types of the local resonators include cylinders, and the dimensional parameters thereof include the radius and height of the cylinders. The types of the local resonators also include cones, and the dimensional parameters thereof include the cone radius and height.

[0018] In the above solution, the dimensional parameters of the upper panel and the lower panel include the plate thickness.

[0019] In the above solution, the viscoelastic material matrix is rubber or polyurethane, the material of the reinforcing members is metal or carbon fiber composite material, the material of the local resonators is metal material, and the materials of the upper panel and the lower panel are glass fiber reinforced plastic composite material or carbon fiber composite material.

[0020] In the above solution, the material parameters of each component include elastic modulus, Poisson's ratio and density. Among them, the material parameters of the viscoelastic material matrix further include loss factor.

[0021] In the above solution, if the mechanical property parameters , it indicates that the mechanical parameters do not meet the design requirements, and it is necessary to improve the type, material parameters and / or dimensional parameters of the reinforcing members.

[0022] In the above solution, if the acoustic property parameters , it indicates that the acoustic parameters do not meet the design requirements, and it is necessary to improve the material parameters of the viscoelastic material matrix, and / or the type, material parameters and / or dimensional parameters of the local resonators.

[0023] In the above solution, the coupling performance parameter represents the stability of the overall performance of the structure, and the value range is [0, 1]. The closer the value is to 1, the better the overall performance.

[0024] In the above solution, the weight coefficient of the mechanical property parameters , and the weight coefficient of the acoustic property parameters , indicating the importance degree of the two, and are reasonably selected according to the design indexes.

[0025] The beneficial effects produced by the present invention are:

[0026] The design method of the present invention first designs the structure of the sound-absorbing sandwich metamaterial. When designing, the mechanical properties and acoustic properties of the structure are considered simultaneously. Reinforcing members are added inside the core layer as the main load-bearing components of the structure, which can effectively resist the deformation caused by hydrostatic pressure and the internal stress of the internal matrix, so that the structure has the ability to maintain the sound-absorbing performance under normal pressure; then the mechanical property parameters are introduced. and acoustic property parameters , and respectively indicate the relative quality of mechanical properties and acoustic properties. The closer the values of and are to 1, the better the mechanical properties or acoustic properties. First, compare the relative magnitudes of , and 0. When and , it indicates that the mechanical properties or acoustic properties of the structure meet the design requirements (the displacement is less than the maximum displacement threshold and the average sound absorption coefficient within the measured frequency range is higher than the average sound absorption coefficient standard ); then the coupling performance parameter is introduced. The coupling performance parameter represents the stability of the overall performance of the structure, and its value range is [0,1]. The closer the value of is to 1, the better the overall performance. And the weight coefficient of the mechanical property parameter and the weight coefficient of the acoustic property parameter can be set according to different design indicators. By comparing the relative magnitudes of and the coupling performance parameter threshold , if , it indicates that the designed structure simultaneously meets the conditions of pressure immunity and low-frequency broadband sound absorption.

[0027] Therefore, the present invention separately considers the mechanical properties and acoustic properties of the structure. The sound-absorbing sandwich metamaterial designed by the present invention can obtain low-frequency broadband sound absorption ability and maintain the sound-absorbing performance under normal pressure under high hydrostatic pressure conditions, that is, the characteristic of pressure immunity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1It is the flowchart of the design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial of the present invention;

[0030] Figure 2 It is the overall structural schematic diagram of the sound-absorbing sandwich metamaterial designed in the embodiment of the present invention;

[0031] Figure 3a is Figure 2 The schematic diagram of the unit cell structure of the shown sound-absorbing sandwich metamaterial;

[0032] Figure 3b is Figure 2 The schematic diagram of the reinforcement member structure of the unit cell of the shown sound-absorbing sandwich metamaterial;

[0033] Figure 3c is Figure 2 The schematic diagram of the local resonator structure of the unit cell of the shown sound-absorbing sandwich metamaterial;

[0034] Figure 4 It is the overall structural schematic diagram of the sound-absorbing sandwich metamaterial designed in other embodiments of the present invention;

[0035] Figure 5 It is the schematic diagram of the sound absorption coefficient calculation results of the sound-absorbing sandwich metamaterial designed in the embodiment of the present invention under different hydrostatic pressures.

[0036] In the figure: 11, upper panel; 12, lower panel;

[0037] 21, viscoelastic material matrix; 22, reinforcement member; 23, local resonator. Detailed implementation manners

[0038] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] It should be noted that the diagrams provided in the embodiments of the present invention only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation. The types, quantities and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0040] In the present invention, it should also be noted that, when terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or positional relationship indicated thereby is based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application. In addition, when terms such as "first" and "second" appear, they are only used for descriptive and differentiating purposes and cannot be construed as indicating or implying relative importance.

[0041] As Figure 1 shown, the present invention proposes a design method for a pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial, including the following steps:

[0042] S1. Conduct a structural design on the sound-absorbing sandwich metamaterial. The sound-absorbing sandwich metamaterial includes an upper panel 11, a lower panel 12, and a core layer located between the upper panel 11 and the lower panel 12; the core layer includes a viscoelastic material matrix 21, as well as a reinforcing member 22 and a local resonator 23 closely embedded inside the viscoelastic material matrix 21. The upper and lower ends of the reinforcing member 22 are respectively in contact with the upper panel 11 and the lower panel 12 for supporting the upper and lower panels, and the local resonators 23 and the reinforcing members 22 are arranged in an alternating manner.

[0043] The sound-absorbing sandwich metamaterial designed in this embodiment is as Figure 2 shown. The reinforcing member 22 is a grid corrugated plate, and the local resonator 23 is a cylinder, and the local resonator 23 is arranged inside the grid.

[0044] S2. Decompose the sound-absorbing sandwich metamaterial into a structure composed of a plurality of unit cells arranged periodically.

[0045] The unit cell of the sound-absorbing sandwich metamaterial in this embodiment is as Figure 3a shown; the reinforcing member in the unit cell structure is as Figure 3b shown. The reinforcing member is a grid corrugated plate, and the two side plates are perpendicular to and connected to the upper panel and the lower panel; the local resonator in the unit cell structure is as Figure 3c shown. The local resonator is a cylinder and is arranged between the two side plates of the grid corrugated plate.

[0046] S3. Determine the types of the reinforcing member and the local resonator, and determine the material parameters and dimensional parameters of the upper panel, the lower panel, the viscoelastic material matrix, the reinforcing member, and the local resonator.

[0047] In this embodiment, the length and width of the unit cell are both 40 mm. The panel material is fiberglass, with a thickness of 5 mm, an elastic modulus of 20 GPa, a Poisson's ratio of 0.3, and a density of 1500 kg / m^3. The core layer thickness is 45 mm. The viscoelastic material matrix is made of rubber, with an elastic modulus of 20 MPa, a Poisson's ratio of 0.49, a density of 1100 kg / m^3, and a loss factor of 0.6. The reinforcement member is a grid corrugated plate, with a plate thickness of 1 mm, a height equal to the height of the core layer, an internal angle of 53° in the grid, an elastic modulus of 100 GPa, a Poisson's ratio of 0.3, and a density of 1400 kg / m^3. The local resonator is a lead cylinder, with a radius of 8 mm and a height of 30 mm. The distances from the cylinder to the upper and lower panels are both 7.5 mm, located in the middle of the core layer, with an elastic modulus of 210 GPa, a Poisson's ratio of 0.3, and a density of 7850 kg / m^3.

[0048] It should be noted that in other embodiments of the present invention, the reinforcement member 22 can also be of other structural types, such as Figure 4 the upright cylindrical lattice shown, and the upright cylindrical lattice is evenly distributed around the local resonator 23. In other embodiments of the present invention, the local resonator 23 can also be of other structural types, such as a cone, etc. The design methods of the sound-absorbing sandwich metamaterials with different structural types are the same as the process of this embodiment, and will not be elaborated here.

[0049] S4. In terms of mechanics, according to the actual conditions, determine the maximum static pressure , and the maximum displacement threshold under the maximum static pressure; in terms of acoustics, according to the actual conditions, determine the measurement frequency range , and the average sound absorption coefficient standard within the measurement frequency range.

[0050] In this embodiment, in terms of mechanics, determine the maximum static pressure to be 3 MPa, and the maximum displacement threshold of the unit cell under the maximum static pressure = 1 mm; in terms of acoustics, determine the measurement frequency range , and the average sound absorption coefficient standard within the measurement frequency range = 0.7.

[0051] S5. Through simulation, calculate the maximum displacement of the unit cell under the maximum static pressure , and the average sound absorption coefficient under normal pressure within the measurement frequency range and the average sound absorption coefficient under the maximum static pressure .

[0052] In this example, the average sound absorption coefficient under normal pressure obtained through simulation is = 0.857, average sound absorption coefficient at 3 MPa = 0.853, maximum displacement u = 0.045 mm.

[0053] S6. Introduce mechanical property parameters and acoustic property parameters , and respectively indicate the relative quality of mechanical properties and acoustic properties. and The closer the value is to 1, the better the mechanical properties or acoustic properties.

[0054] Mechanical property parameters are:

[0055]

[0056] In the formula, is the maximum static pressure the maximum displacement of the unit cell under is the maximum static pressure the maximum displacement threshold under .

[0057] Acoustic property parameters are:

[0058]

[0059] In the formula, is the average sound absorption coefficient under normal pressure within the range of is the maximum static pressure within the range of the average sound absorption coefficient under is the average sound absorption coefficient standard.

[0060] S7. Compare , with 0. If the mechanical property parameter , or the acoustic property parameter , then the mechanical property or acoustic property of the structure does not meet the design requirements (the displacement needs to be less than the maximum displacement threshold and the average sound absorption coefficient within the measurement frequency range needs to be higher than the average sound absorption coefficient standard ), and re-enter S3 to improve the type of reinforcement members and / or local resonators, the material parameters of each part, and / or the size parameters; otherwise, enter S8.

[0061] In this example, the mechanical property parameter = 0.955 is obtained through simulation calculation, and the acoustic property parameter = 0.975. Since both parameters are greater than 0 and the structure meets the conditions of pressure immunity or low-frequency broadband sound absorption, proceed to step 8.

[0062] S8. Introduce the coupling performance parameter and the coupling performance parameter threshold , where the coupling performance parameter is , is the weight coefficient of the mechanical performance parameter, is the weight coefficient of the acoustic performance parameter, and there is . The coupling performance parameter represents the stability of the overall performance of the structure, and its value range is [0, 1]. The closer the value is to 1, the better the overall performance. The weight coefficient of the mechanical performance parameter and the weight coefficient of the acoustic performance parameter indicate their importance levels, and they are reasonably selected according to the design indicators.

[0063] In this example, more importance is attached to the acoustic performance. Set the coupling performance parameter threshold = 0.8, the weight coefficient = 0.4, = 0.6. Then the coupling performance parameter = 0.967.

[0064] S9. Compare with . If , it means that the designed structure does not simultaneously meet the conditions of pressure immunity and low-frequency broadband sound absorption. Re-enter S3 to improve the type of reinforcement members and / or local resonators, the material parameters of each part, and / or the size parameters. If , it means that the designed structure simultaneously meets the conditions of pressure immunity and low-frequency broadband sound absorption.

[0065] In this embodiment, the coupling performance parameter = 0.967 > 0.8 = , indicating that the structure designed in this example simultaneously meets the conditions of pressure immunity and low-frequency broadband sound absorption. In this example, a pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial is successfully designed.

[0066] To verify the effectiveness of the method of the present invention, the present invention also calculated the sound absorption coefficients of the above-designed pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial under different hydrostatic pressures. The results are as Figure 5 shown. It can be seen from Figure 5 that the average sound absorption coefficients of this structure under normal pressure and 3 MPa are 0.857 and 0.853 respectively, indicating that this structure has good low-frequency broadband sound absorption performance and its acoustic performance is immune to pressure.

[0067] It should be noted that, according to the needs of implementation, each step / component described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0068] The magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0069] It should be understood that those of ordinary skill in the art can make improvements or transformations according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A design method for a pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial, characterized in that: The design method comprises the following steps: S1. Structural design of the sound-absorbing sandwich metamaterial, comprising an upper panel, a lower panel and a core layer located between the upper panel and the lower panel; the core layer comprises a viscoelastic material matrix and a reinforcing member and a local resonant body embedded in the viscoelastic material matrix, the upper end and the lower end of the reinforcing member are respectively abutted against the upper panel and the lower panel, and the local resonant body and the reinforcing member are arranged in a staggered manner; S2, decomposing the sound-absorbing sandwich metamaterial into a structure consisting of a plurality of periodically arranged unit cells; S3, determining the types of the reinforcing member and the local resonant body, and determining the material parameters and size parameters of the upper panel, the lower panel, the viscoelastic material matrix, the reinforcing member and the local resonant body; S4. In terms of mechanics, determine the maximum static pressure based on actual conditions. , and the maximum displacement threshold at maximum static pressure ; In terms of acoustics, determine the measurement frequency range based on actual conditions , and the average sound absorption coefficient standard within the measurement frequency range ; S5. Calculate the maximum static pressure through simulation The maximum displacement of the lower unit cell , and the frequency Average sound absorption coefficient at normal pressure within the range and maximum static pressure The average sound absorption coefficient under ; S6. Introduction of mechanical properties parameters Acoustic performance parameters , , ; S7. Comparison , The relative size to 0, if or , the mechanical properties or acoustic properties of the structure do not meet the design requirements, and the process goes back to S3 to improve the type, material parameters and / or size parameters of the reinforcement components and / or local resonance bodies; otherwise, the process goes to S8; S8. Introduction of coupling performance parameters and coupling performance parameter thresholds , where the coupling performance parameters for , is the weight coefficient of mechanical performance parameters, is the weight coefficient of the acoustic performance parameter, and ; S9. Comparison and Size, if , it means that the designed structure does not meet the pressure immunity and low-frequency broadband sound absorption conditions at the same time, and re-enter S3 to improve the type of reinforcement components and / or local resonance bodies, material parameters of each part and / or size parameters; if , indicating that the designed structure satisfies both pressure immunity and low-frequency broadband sound absorption conditions.

2. The design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial according to claim 1 is characterized in that: The type of reinforcement member includes a grid corrugated plate, and its size parameters include the thickness of the grid plate and the angle between the grid plates, and the local resonance body is arranged in the grid; The type of reinforcing component also includes a right cylindrical lattice, whose size parameters include a lattice diameter, and the right cylindrical lattice is evenly distributed around the local resonator.

3. The design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial according to claim 1 is characterized in that: The local resonator type includes a cylinder, and its size parameters include the radius and height of the cylinder; The local resonator type also includes a cone, whose size parameters include the cone radius and height.

4. The design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial according to claim 1 is characterized in that: The size parameters of the upper panel and the lower panel include the thickness.

5. The design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial according to claim 1 is characterized in that: The viscoelastic material matrix is ​​rubber or polyurethane, the material of the reinforcing member is metal or carbon fiber composite material, the material of the local resonance body is metal material, and the material of the upper panel and the lower panel is glass fiber reinforced plastic composite material or carbon fiber composite material.

6. The design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial according to claim 1 is characterized in that: The material parameters of each component include elastic modulus, Poisson's ratio and density, wherein the material parameters of the viscoelastic material matrix also include loss factor.

7. The design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial according to claim 1 is characterized in that: If the mechanical properties parameters , it means that the mechanical parameters do not meet the design requirements and the type, material parameters and / or size parameters of the reinforced components need to be improved.

8. The design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial according to claim 1 is characterized in that: If the acoustic performance parameters , it means that the acoustic parameters do not meet the design requirements, and it is necessary to improve the material parameters of the viscoelastic material matrix and / or the type, material parameters and / or size parameters of the local resonator.

9. The design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial according to claim 1, characterized in that: The coupling performance parameters Indicates the stability of the overall performance of the structure, with a value range of [0,1], The closer the value is to 1, the better the overall performance.

10. The design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial according to claim 1, characterized in that: Weight coefficient of the mechanical performance parameter , weight coefficient of acoustic performance parameter , indicating the importance of the two, and making a reasonable choice based on the design indicators.

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