Design method of pressure immune underwater low-frequency broadband sound absorption sandwich metamaterial

Abstract

The invention discloses a design method of a pressure immune underwater low-frequency broadband sound-absorbing sandwich metamaterial, which comprises the following steps of: firstly, carrying out structural design on the sound-absorbing sandwich metamaterial which comprises an upper panel, a lower panel and a core layer positioned between the upper panel and the lower panel; wherein the core layer comprises a viscous-elastic material matrix, and a reinforcing member and a local resonance body which are embedded in the viscous-elastic material matrix, and then whether the structure meets pressure immunity or low-frequency broadband sound absorption conditions is judged by introducing mechanical property parameters and acoustic property parameters. And whether the structure meets the pressure immunity and low-frequency broadband sound absorption conditions at the same time or not is judged by introducing coupling performance parameters and coupling performance parameter thresholds. According to the designed sound absorption sandwich metamaterial, the mechanical property and the acoustic property of the structure are considered at the same time, the structure designed through the method can obtain the low-frequency broadband sound absorption capacity, deformation caused by hydrostatic pressure and internal stress of an internal base body can be effectively resisted at the same time, and therefore the sound absorption performance under the normal pressure is kept.

Description

Technical Field

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

[0002] Submarines and other underwater vehicles need to maintain a high degree of concealment when performing missions to avoid enemy detection and attack. Good acoustic stealth performance will ensure that underwater vehicles are not easily discovered by the enemy when performing missions in the deep sea, thereby improving the success rate and survivability of operations. As underwater vehicles develop in the direction of greater diving depth and quietness, composite structures with good mechanical and acoustic properties will become the future development trend of underwater acoustic stealth structures.

[0003] Although most underwater acoustic structures currently 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, designing a pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial has practical significance and application value. Summary of the invention

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

[0005] The technical solution adopted by the present invention is: A method for designing a pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial, the method comprising 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 , then the mechanical properties or acoustic properties of the structure do not meet the design requirements (the displacement must be less than the maximum displacement threshold And the average sound absorption coefficient within the measurement frequency range must be higher than the average sound absorption coefficient standard ), re-enter S3 to improve the type, material parameters and / or size parameters of the reinforcement component and / or the local resonator; otherwise, enter S8; S8. Introducing 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.

[0006] In the above scheme, the type of reinforcing component includes a grid corrugated plate, whose size parameters include the thickness of the grid plate and the angle between the grid plates, and the local resonant body is arranged in the grid; the type of reinforcing component also includes a right cylindrical lattice, whose size parameters include the lattice diameter, and the right cylindrical lattice is evenly distributed around the local resonant body.

[0007] In the above scheme, the local resonant body type includes a cylinder, and its size parameters include the radius and height of the cylinder; the local resonant body type also includes a cone, and its size parameters include the radius and height of the cone.

[0008] In the above solution, the size parameters of the upper panel and the lower panel include the thickness.

[0009] In the above scheme, the viscoelastic material matrix is ​​rubber or polyurethane, the material of the reinforcing component 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 fiberglass composite material or carbon fiber composite material.

[0010] In the above solution, 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.

[0011] In the above scheme, if the mechanical performance 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.

[0012] In the above scheme, 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.

[0013] In the above scheme, the coupling performance parameter 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.

[0014] In the above scheme, the weight coefficient of the mechanical performance parameter is , weight coefficient of acoustic performance parameter , indicating the importance of the two, and making a reasonable choice based on the design indicators.

[0015] The beneficial effects produced by the present invention are: The design method of the present invention first designs the structure of the sound-absorbing sandwich metamaterial, taking into account both the mechanical properties and acoustic properties of the structure. A reinforcing member is added inside the core layer as the main load-bearing component 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 absorption performance under normal pressure; then the mechanical performance parameters are introduced Acoustic performance parameters , and They respectively indicate the relative quality of mechanical properties and acoustic properties. and The closer the value is to 1, the better the mechanical or acoustic performance is. , The relative size to 0, when and When the mechanical properties or acoustic properties of the structure meet the design requirements (displacement is less than the maximum displacement threshold And the average sound absorption coefficient within the measurement frequency range is higher than the average sound absorption coefficient standard ); then introduce coupling performance parameters , 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. And the weight coefficient of mechanical performance parameters can be set according to different design indicators. Weighting coefficients of acoustic performance parameters , by comparison and coupling performance parameter thresholds The relative size of , indicating that the designed structure satisfies both pressure immunity and low-frequency broadband sound absorption conditions.

[0016] Therefore, the present invention takes into account the mechanical properties and acoustic properties of the structure respectively. The sound-absorbing sandwich metamaterial designed by the present invention can obtain low-frequency broadband sound absorption capability while maintaining the sound absorption performance under normal pressure under high hydrostatic pressure conditions, that is, the characteristic of pressure immunity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 is a flow chart of the design method of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial of the present invention; Figure 2 Schematic diagram of the overall structure of the sound-absorbing sandwich metamaterial designed in an embodiment of the present invention; Figure 3(a) is Figure 2 Schematic diagram of the unit cell structure of the sound absorbing sandwich metamaterial shown; Figure 3(b) is Figure 2 Schematic diagram of the structure of the reinforcement component of a unit cell of the sound-absorbing sandwich metamaterial shown; Figure 3(c) is Figure 2 Schematic diagram of the local resonance structure of a unit cell of the sound-absorbing sandwich metamaterial; Figure 4 is a schematic diagram of the overall structure of a sound-absorbing sandwich metamaterial designed in other embodiments of the present invention; Figure 5 It is a schematic diagram of the calculation results of the sound absorption coefficient of the sound-absorbing sandwich metamaterial designed in an embodiment of the present invention under different hydrostatic pressures.

[0019] In the figure: 11, upper panel; 12, lower panel; 21. Viscoelastic material matrix; 22. Reinforcement member; 23. Local resonator. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with 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.

[0021] It should be noted that the illustrations provided in the embodiments of the present invention are only used to illustrate the basic concept of the present invention in a schematic manner. Therefore, the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout type may also be more complicated.

[0022] In the present invention, it is also necessary to explain that, if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, if the terms "first" and "second" appear, they are only used for description and distinction purposes, and cannot be understood as indicating or implying relative importance.

[0023] like Figure 1 As shown, the present invention proposes a design method for a pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial, comprising the following steps: S1. Structural design is performed on a sound-absorbing sandwich metamaterial, wherein the sound-absorbing sandwich metamaterial comprises 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 comprises a viscoelastic material matrix 21, and a reinforcing member 22 and a local resonator 23 tightly embedded in the viscoelastic material matrix 21, wherein the upper end and the lower end of the reinforcing member 22 are respectively abutted against the upper panel 11 and the lower panel 12 for supporting the upper and lower panels, and the local resonator 23 and the reinforcing member 22 are alternately arranged.

[0024] The sound absorbing sandwich metamaterial designed in this embodiment is as follows Figure 2 As shown, the reinforcing member 22 is a grid corrugated plate, the local resonator 23 is a cylinder, and the local resonator 23 is arranged in the grid.

[0025] S2. Decompose the sound-absorbing sandwich metamaterial into a structure composed of multiple periodically arranged unit cells.

[0026] The unit cell of the sound-absorbing sandwich metamaterial of this embodiment is shown in FIG3 (a); the reinforcing member in the unit cell structure is shown in FIG3 (b), and the reinforcing member is a grid corrugated plate, and the two wall panels are perpendicular to and connected to the upper panel and the lower panel; the local resonator in the unit cell structure is shown in FIG3 (c), and the local resonator is a cylinder, which is arranged between the two wall panels of the grid corrugated plate.

[0027] S3. Determine the types of the reinforcing member and the local resonant body, and determine 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.

[0028] In this embodiment, the length and width of the unit cell are both 40 mm. The panel material is glass fiber reinforced plastic 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 material of the viscoelastic material matrix is ​​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 reinforcing member is a grid corrugated plate with a thickness of 1 mm, a height equal to the core layer height, an internal angle of 53°, 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 distance between the cylinder and the upper and lower panels is 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.

[0029] It should be noted that, in other embodiments of the present invention, the reinforcing member 22 may also be of other structural types, such as Figure 4 The vertical cylindrical lattice is evenly distributed around the local resonator 23. In other embodiments of the present invention, the local resonator 23 may also be of other structural types, such as a cone, etc. The design method of the sound-absorbing sandwich metamaterial of different structural types is the same as the process of this embodiment, and will not be repeated here.

[0030] 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 .

[0031] In this embodiment, in terms of mechanics, the maximum static pressure is determined The maximum displacement threshold of the unit cell under the maximum static pressure is 3 MPa. =1mm; Acoustics: Determine the measurement frequency range , the average sound absorption coefficient standard within the measurement frequency range =0.7.

[0032] S5. Calculate the maximum static pressure through simulation The maximum displacement of the lower unit cell , and the measurement frequency Average sound absorption coefficient at normal pressure within the range and maximum static pressure The average sound absorption coefficient under .

[0033] In this example, the average sound absorption coefficient under normal pressure is obtained through simulation calculation: =0.857, average sound absorption coefficient at 3MPa =0.853, maximum displacement u =0.045mm.

[0034] S6. Introduction of mechanical properties parameters Acoustic performance parameters , and They respectively indicate the relative quality of mechanical properties and acoustic properties. and The closer the value is to 1, the better the mechanical or acoustic performance.

[0035] Mechanical properties parameters for:

[0036] In the formula, Maximum static pressure The maximum displacement of the lower unit cell is Maximum static pressure Lower maximum displacement threshold .

[0037] Acoustic performance parameters for:

[0038] In the formula, for The average sound absorption coefficient at normal pressure within the range, for Maximum static pressure within the range The average sound absorption coefficient under It is the average sound absorption coefficient standard.

[0039] S7. Comparison , The relative size of 0, if the mechanical properties parameter , or acoustic performance parameters , then the mechanical properties or acoustic properties of the structure do not meet the design requirements (the displacement must be less than the maximum displacement threshold And the average sound absorption coefficient within the measurement frequency range must be higher than the average sound absorption coefficient standard ), re-enter S3 to improve the type of the reinforcing component and / or the local resonator, the material parameters of each part and / or the size parameters; otherwise, enter S8.

[0040] In this example, the mechanical properties parameters obtained by simulation calculation are =0.955, acoustic performance parameters =0.975, both parameters are greater than 0, the structure meets the pressure immunity or low-frequency broadband sound absorption conditions, and proceed to step 8.

[0041] S8. Introducing 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 . 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. Weight coefficient of mechanical performance parameters , weight coefficient of acoustic performance parameter , indicating the importance of the two, and making a reasonable choice based on the design indicators.

[0042] In this example, acoustic performance is more important, and the coupling performance parameter threshold is set =0.8, weight coefficient =0.4, =0.6. Then the coupling performance parameter =0.967.

[0043] 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.

[0044] In this embodiment, the coupling performance parameters =0.967>0.8= , indicating that the structure designed in this example satisfies both the pressure immunity and low-frequency broadband sound absorption conditions. This example successfully designed a pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial.

[0045] In order to verify the effectiveness of the method of the present invention, the present invention also calculated the sound absorption coefficient of the pressure-immune underwater low-frequency broadband sound-absorbing sandwich metamaterial designed above under different hydrostatic pressures. The results are as follows: Figure 5 As shown, from Figure 5 It can be seen that the average sound absorption coefficients of the structure at normal pressure and 3MPa are 0.857 and 0.853 respectively, indicating that the structure has good low-frequency broadband sound absorption performance and the acoustic performance is immune to pressure.

[0046] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, and 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.

[0047] The order of execution of each step in the above embodiment does 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 on the implementation process of the embodiment of the present application.

[0048] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection 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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