Underwater sound absorption superstructure reverse design method under multi-material system

Abstract

The invention discloses a reverse design method of an underwater sound absorption superstructure under a multi-material system in the technical field of vibration and noise control. The reverse design method of the underwater sound absorption superstructure under the multi-material system comprises the following steps: predicting the macroscopic sound absorption performance of the superstructure based on an equivalent medium theory; based on an energy homogenization theory of an SIMP interpolation function, establishing a superstructure topological optimization reverse design method under the multi-material system; and a proper material system is selected, and the multi-material superstructure is precisely designed by taking equivalent elastic parameters of the superstructure as targets. Compared with an existing underwater sound absorption superstructure design method, the method has the advantages that large-scale sound-solid coupling finite element calculation can be avoided, and efficient design of the superstructure and good low-frequency broadband sound absorption performance are achieved; in addition, the design method provided by the invention has universality under different multi-material systems.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration and noise control, and in particular to a reverse design method of an underwater sound-absorbing superstructure in a multi-material system. Background Art

[0002] With the development of modern sonar technology, the acoustic stealth problem of underwater equipment has become increasingly prominent, increasing the possibility of being hit by underwater weapons such as missiles and torpedoes, which seriously threatens the survivability of underwater equipment. Underwater sound-absorbing materials are the core technical means to improve the acoustic stealth performance of underwater equipment. At present, there are two main empirical design modes for underwater sound-absorbing superstructures. One is the cavity-type superstructure, which is composed of an acoustic cavity embedded in a rubber matrix. The other is the local resonance-type superstructure, which is composed of a local resonance unit embedded in a rubber matrix. The local resonance unit is usually a hard metal coated with soft silicone rubber. At the level of design methods, designers often rely on manual experience and use finite element analysis methods to compare and analyze different structures and then select a relatively better structure. However, such a design process is inefficient on the one hand, because the finite element calculation of underwater superstructures is a multi-physics field problem, which requires solving a large-scale acoustic-solid coupling stiffness matrix; on the other hand, it is greatly affected by the initial configuration, and the design scope and design effect are limited. Summary of the invention

[0003] In order to solve the above problems, the purpose of the present invention is to provide a reverse design method for underwater sound absorbing superstructures in a multi-material system, so as to solve the problems that the existing underwater superstructures have a narrow sound absorption frequency band, low-frequency realization is difficult, and the range of structures that can be conceived by humans is getting smaller and smaller, and the single-material topological optimization design space is limited. The underwater sound absorbing superstructure designed by this method is more reasonable, meets the high sound absorption performance requirements of the sound absorbing structure with a lower frequency and a wider bandwidth, can be universal in different multi-material systems, and improve the optimization efficiency at the same time.

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

[0005] The present invention provides a reverse design method for an underwater sound absorbing superstructure in a multi-material system, comprising the following steps:

[0006] S1. Prediction of macroscopic sound absorption performance of superstructures based on equivalent medium theory;

[0007] S2. Based on the energy homogenization theory of SIMP interpolation function, an inverse design method for superstructure topology optimization in multi-material system is established;

[0008] S3. Select appropriate material systems and take the equivalent elastic parameters of superstructures as the target to achieve precise design of multi-material superstructures.

[0009] As one aspect of the inverse design method of an underwater sound absorbing superstructure in a multi-material system of the present invention, S1 comprises the following steps:

[0010] S11. Construct an underwater sound absorption equivalent medium model and study the stress and strain of particles during sound wave propagation from the perspective of micromechanics;

[0011] S12. Calculate the equivalent elastic stiffness matrix of the superstructure layer, add the loss factor η, and analyze the sound absorption mechanism and parameter influence brought by the loss factor η.

[0012] As one aspect of the reverse design method of an underwater sound-absorbing superstructure in a multi-material system of the present invention, the micromechanical perspective in S11 studies the stress and strain of particles in the sound wave propagation process, including the boundary conditions between different media, derives the analytical relationship between the sound absorption performance of the superstructure model and the macroscopic equivalent mechanical parameters and elastic wave characteristics, and calculates the theoretical prediction sound absorption coefficient curve and prediction model of the underwater sound-absorbing superstructure.

[0013] As one aspect of the reverse design method of an underwater sound absorbing superstructure in a multi-material system of the present invention, S12 comprises the following steps:

[0014] S121. Assume that each element of the equivalent elastic stiffness matrix of the superstructure layer has a loss factor η, and the η of each element is not necessarily equal. Study the effect of the change of parameter η on the sound absorption coefficient curve of the structure;

[0015] S122. Equivalent elastic stiffness matrix C of the superstructure in the global coordinate system M =RC l R T ,

[0016] Among them, R is the rotation matrix, which is related to the structural rotation angle α, and the equivalent elastic stiffness matrix C in the local coordinate system is l and anisotropy index γ 1 , deformation characteristic parameter γ 2 , deformation characteristic parameter γ 3 and elastic constant The elastic constant

[0017] S123. Study on the equivalent elastic parameters C of superstructures that achieve low-frequency broadband underwater sound absorption performance M , obtain the underwater sound absorption superstructure prediction model and the theoretical prediction sound absorption coefficient curve.

[0018] As one aspect of the inverse design method of an underwater sound absorbing superstructure in a multi-material system of the present invention, S2 comprises the following steps:

[0019] S21. The topology optimization is performed by using the energy homogenization theory solution algorithm based on SIMP interpolation function to obtain the macroscopic equivalent elastic stiffness matrix D of the superstructure layer. H ;

[0020] S22. The MMA optimization criterion is used to design multiple constraints and produce more structural details. The hyperbolic tangent projection filter is used to obtain a clear topological structure.

[0021] As one aspect of the reverse design method of an underwater sound absorbing superstructure in a multi-material system of the present invention, the S21 comprises the following steps:

[0022] S211. Topologically optimize the microscopic unit cell structure of each material point, where each unit cell structure is composed of different materials and holes;

[0023] S212. The design variables of multiple materials and their elastic moduli are combined under the SIMP interpolation function, and the objective function is set as the macroscopic equivalent elastic stiffness matrix D H Reach the set value;

[0024] S213. When using homogenization theory for topology optimization, the constraints on the boundaries are transformed into a certain number of explicit constraints between corresponding pairs of nodes on the relative surface of the RVE.

[0025] As one aspect of the reverse design method of an underwater sound absorbing superstructure in a multi-material system of the present invention, the S22 comprises the following steps:

[0026] S221.MMA optimization criterion designs multiple constraints and generates more structural details. The objective function is the macroscopic equivalent elastic stiffness matrix D H , the value of each element in the elastic stiffness is divided into real and imaginary parts;

[0027] S222. The values ​​that reach the set values ​​are taken as sub-constraints respectively, and then assembled into one constraint. Therefore, the orthogonal anisotropic superstructure layer has a total of six constraints, and each constraint has two sub-constraints of real and imaginary parts;

[0028] S223. Using hyperbolic tangent projection filtering, the density of each element is filtered to 0 or 1, thereby obtaining a clear topological structure.

[0029] As one aspect of the reverse design method of an underwater sound absorbing superstructure in a multi-material system of the present invention, S3 comprises the following steps:

[0030] S31. The topological structure obtained in S22 is processed with CAD software to form zigzag boundaries between different materials, and then imported into COMSOL Multiphysics software for simulation to obtain a sound absorption coefficient curve of the topological structure;

[0031] S32. Compare the sound absorption coefficient curve obtained in S31 with the theoretically predicted sound absorption coefficient curve in S123 to confirm the feasibility of multi-material topology optimization.

[0032] By adopting the above technical solution, the present invention has the following advantages:

[0033] The present invention provides an inverse design method for underwater sound-absorbing superstructures in a multi-material system. Compared with the design of a single-material superstructure, the design of a multi-material superstructure aims to find the optimal material layout within a specified design domain by reasonably distributing a variety of different materials in the structure, thereby maximizing or minimizing certain goals while satisfying one or more design constraints. In this method, the design space is divided into a plurality of cells, each of which can use a different material, so as to achieve fine control of the structural performance, and by flexibly adjusting the material distribution, low-frequency broadband high sound absorption performance can be achieved underwater. The inverse design method for underwater sound-absorbing superstructures in a multi-material system can realize the topological optimization design of the microstructure of multiple materials, obtain a macroscopic equivalent elastic stiffness matrix, and realize a low-frequency broadband sound absorption coefficient curve in the underwater sound-absorbing superstructure. The inverse design method for underwater sound-absorbing superstructures in a multi-material system has good versatility in different multi-material systems, and can avoid a large number of finite element calculations, improve optimization efficiency and reduce calculation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of a multi-material topological optimization structure composed of soft rubber and glass fiber nylon resin matrix according to an embodiment of the present invention;

[0035] Figure 2 for Figure 1 Schematic diagram of the sound absorption model simulation;

[0036] Figure 3 for Figure 1 Comparison of sound absorption coefficient curves predicted by structural theory and calculated by simulation;

[0037] Figure 4 A schematic diagram of a multi-material topology optimization structure composed of soft rubber and a carbon fiber nylon resin matrix according to an embodiment of the present invention;

[0038] Figure 5 for Figure 4 Comparison of sound absorption coefficient curves predicted by structural theory and calculated by simulation. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is described in detail below in conjunction with the drawings in the specification. It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0040] This embodiment provides a reverse design method for underwater sound absorbing superstructure in a multi-material system, and its research objects include: rubber layer, superstructure layer and rubber layer. The frame is a column structure, in which the superstructure layer is composed of soft material 1, hard material 2 and holes. Figure 1 As shown in FIG. 1 , the energy homogenization method based on the SIMP interpolation function is used to perform topological optimization on the microscopic unit cell structure of each material, so as to achieve a stable transition from one material to another until the required material properties are met. The inverse design method of the underwater sound absorbing superstructure in the multi-material system includes the following steps:

[0041] S1. Prediction of macroscopic sound absorption performance of superstructures based on equivalent medium theory;

[0042] Among them, S1 includes the following specific steps:

[0043] S11. Construct an underwater sound absorption equivalent medium model, study the equivalent parameters of particles in the sound wave propagation process from the perspective of microscopic cellular structure and consider the actual boundary conditions including the boundary conditions between different media, derive the analytical relationship between the sound absorption performance of the superstructure model and the macroscopic equivalent mechanical parameters and elastic wave characteristics, and calculate the theoretical prediction sound absorption coefficient curve and prediction model of the underwater sound absorption superstructure.

[0044] S12. Calculate the equivalent elastic stiffness matrix of the superstructure layer, add the loss factor η, and analyze the sound absorption mechanism and parameter influence brought by the loss factor η.

[0045] Wherein, S12 includes the following specific steps:

[0046] S121. Based on the equivalent medium theory, the macroscopic sound absorption performance of the superstructure is predicted. It is assumed that each element of the equivalent elastic stiffness matrix of the superstructure layer has a loss factor η, and the η of each element is not necessarily equal. The effect of the change of parameter η on the sound absorption coefficient curve of the structure is studied.

[0047] S122. The underwater sound absorption superstructure model includes a water layer, a rubber layer, a superstructure layer, and a rubber layer. The thickness of the two rubber layers is 0.01m, and the thickness of the superstructure layer is 0.03m. The superstructure layer can be made of hard materials such as glass fiber nylon resin and carbon fiber nylon resin as the matrix. The equivalent elastic stiffness matrix C of the superstructure in the global coordinate system is M =RC l R T ,

[0048] Among them, R is the rotation matrix, which is related to the structural rotation angle α, and the equivalent elastic stiffness matrix C in the local coordinate system is l and anisotropy index γ 1 , deformation characteristic parameter γ 2 , deformation characteristic parameter γ 3 and the elastic constant along the principal axis The elastic constant along the principal axis is After adding the assumed loss factor η, η becomes a new independent variable.

[0049] S123. Study on the equivalent elastic parameters C of superstructures that achieve low-frequency broadband underwater sound absorption performance M , obtain the underwater sound absorption superstructure prediction model and the theoretical prediction sound absorption coefficient curve.

[0050] S2. Based on the energy homogenization theory of SIMP interpolation function, an inverse design method for superstructure topology optimization in a multi-material system is established; wherein the multi-material can be composed of soft material rubber, hard material resin pores, and metal material.

[0051] S2 includes the following specific steps:

[0052] S21. The topology optimization is performed by using the energy homogenization theory solution algorithm based on SIMP interpolation function to obtain the macroscopic equivalent elastic stiffness matrix D of the superstructure layer. H ;

[0053] S21 includes the following specific steps:

[0054] S211. Energy homogenization theory performs topological optimization on the microscopic unit cell structure of each material point, where each unit cell structure is composed of different materials and holes;

[0055] S212. The design variables of multiple materials and their elastic moduli are combined under the SIMP interpolation function. At the same time, the repetition of the cells with holes in space causes the anisotropic characteristics of the macroscopic properties of the material. The objective function is set as the macroscopic equivalent elastic stiffness matrix D H Reach the set value;

[0056] S213. When using energy homogenization theory for topology optimization, the constraints on the boundaries are converted into a certain number of explicit constraints between corresponding node pairs on the relative surface of RVE. The boundary conditions set in this way can meet the periodicity and continuity requirements of displacement-based finite element analysis and realize periodic boundary conditions.

[0057] Among them, the multi-material topology optimization structure is as follows Figure 1 As shown, 1 is a soft rubber material, and 2 is a glass fiber nylon resin matrix hard material; the present invention has the versatility under a multi-material system, and the same equivalent elastic stiffness matrix D H The multi-material topological optimization structure composed of the soft rubber 5 and the carbon fiber nylon matrix 6 is as follows: Figure 4 As shown, a wide sound absorption performance curve with an average sound absorption coefficient of >0.8 from 300 to 3000H can be achieved.

[0058] S22. The MMA optimization criterion is used to design multiple constraints and produce more structural details. The hyperbolic tangent projection filter is used to obtain a clear topological structure.

[0059] S22 includes the following steps:

[0060] S221.MMA optimization criterion designs multiple constraints and generates more structural details. It has a constant optimization efficiency and good convergence effect for multiple design variables and multi-material systems. The objective function is the macroscopic equivalent elastic stiffness matrix D H , the value of each element in the elastic stiffness is divided into real and imaginary parts;

[0061] S222. The values ​​that reach the set values ​​are taken as sub-constraints respectively and then assembled into one constraint. Therefore, the orthotropic superstructure layer has a total of four constraints. Each constraint has two sub-constraints of real and imaginary parts. In addition, the volume constraint of the multi-material system can reach six constraints or even more.

[0062] S223. Using hyperbolic tangent projection filtering, the density of each element is filtered to 0 or 1, avoiding problems such as checkerboard, intermediate density and grayscale that appear in the optimization, thereby obtaining a clear topological structure.

[0063] S3. Select appropriate material systems and take the equivalent elastic parameters of superstructures as the target to achieve precise design of multi-material superstructures.

[0064] S3 includes the following steps:

[0065] S31. The topological structure obtained in step S22 is processed by CAD software to form a zigzag boundary between different materials, and then imported into COMSOL Multiphysics software for simulation to obtain a sound absorption coefficient curve of the topological structure;

[0066] Because the structural topology is determined by the pseudo-density defined by the elements, a jagged boundary representation will be generated. Therefore, the topological structure obtained by S22 needs to be imported into AutoCAD for boundary processing and converted into a microstructure unit with smooth structural boundaries and clear material interfaces to avoid the inability to convert solid materials into solid materials due to the lack of a closed curve when imported into the COMSOL simulation software.

[0067] The following is obtained by frequency domain simulation in COMSOL Multiphysics software: Figure 2 The total sound pressure P of the surface I shown, where the total sound pressure P includes the incident sound pressure P i and reflected sound pressure P r , where the incident sound pressure P i As a known condition, the sound absorption coefficient α can be determined:

[0068] Figure 2 The established simulation model consists of water area 3, rubber layer 2, and superstructure layer from top to bottom. The superstructure layer is composed of soft material 1 and hard material 2 to form a multi-material system topology optimization structure. Taking the glass fiber nylon resin hard material in the superstructure layer as an example, the elastic modulus E 1 =6e9Pa, density 1250kg / m 3 , Poisson's ratio 0.3; elastic modulus E of soft material 2 =(1+0.8i)*30e6Pa, density 1300kg / m 3 , Poisson's ratio 0.495. The soft material provides loss factor η, which strengthens the dissipation of the reflected sound waves. The density of the rubber layer is 1160kg / m 3 , longitudinal wave velocity (1500+75i)m / s, transverse wave velocity (98+27i)m / s. The specific structure of the superstructure layer is as follows Figure 2 As shown in the figure, the unit periodic structure is rotated 60° and accurately intercepted into a continuous structure. It is necessary to establish multiple Bloch-Floquet periodic boundary conditions in the COMSOL Multiphysics solid mechanics physical field to ensure the consistency of the displacement field changes on both sides of the structure. The topological structure obtained by S22 is simulated and its sound absorption coefficient curve is calculated.

[0069] S32. The sound absorption coefficient curve obtained in S31 was compared with the theoretically predicted sound absorption coefficient curve in S123. The results were basically consistent, confirming the feasibility of multi-material topology optimization. The topology optimization took five minutes and the simulation calculation took one and a half hours, which greatly reduced the calculation cost compared with the traditional topology optimization method.

[0070] Comparison between the two sets of simulation results shows that the inverse design method of underwater sound-absorbing superstructures under multi-material systems can successfully design underwater sound-absorbing superstructures with low-frequency and broadband sound absorption performance under different multi-material systems.

[0071] In two specific embodiments, Figure 1 and Figure 4 As shown in the figure, the soft rubber, glass fiber nylon resin holes and carbon fiber nylon resin holes respectively form two multi-material systems. After finite element calculation verification, both can achieve the target equivalent elastic stiffness matrix and obtain high sound absorption performance with an average sound absorption coefficient of > 0.8 in the low frequency band of 300-3000Hz. Figure 3 and Figure 5 As shown, even in different multi-material systems, the inverse design method of underwater sound absorbing superstructure in this multi-material system has good versatility.

[0072] Finally, it should be pointed out that although the present invention has been described with reference to the current specific embodiments, ordinary technicians in this technical field should realize that the above embodiments are only used to illustrate the present invention and are not used as a limitation of the present invention. Various equivalent changes or substitutions can be made without departing from the concept of the present invention. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present invention, they will fall within the scope of the claims of the present invention.

Claims

1. A reverse design method for underwater sound-absorbing superstructures in a multi-material system. It is characterized in that The following steps are involved: S1. Prediction of macroscopic sound absorption performance of superstructures based on equivalent medium theory; S2. Based on the energy homogenization theory of SIMP interpolation function, an inverse design method for superstructure topology optimization in multi-material system is established; S3. Select appropriate material systems and take the equivalent elastic parameters of superstructures as the target to achieve precise design of multi-material superstructures.

2. The method for inverse design of underwater sound absorbing superstructure in a multi-material system according to claim 1, It is characterized in that The S1 comprises the following steps: S11. Construct an underwater sound absorption equivalent medium model and study the equivalent parameters of particles in the sound wave propagation process from the perspective of microscopic cell structure; S12. Calculate the equivalent elastic stiffness matrix of the superstructure layer in the superstructure model, add the loss factor η, and analyze the sound absorption mechanism and parameter influence brought by the loss factor η.

3. The inverse design method of underwater sound absorbing superstructure in a multi-material system according to claim 2, It is characterized in that The S11 studies the equivalent parameters of particles in the sound wave propagation process from the perspective of the microscopic cellular structure and takes into account the actual boundary conditions including the boundary conditions between different media, derives the analytical relationship between the sound absorption performance of the superstructure model and the macroscopic equivalent mechanical parameters and elastic wave characteristics, and calculates the theoretical prediction sound absorption coefficient curve and prediction model of the underwater sound absorbing superstructure.

4. The method for reverse design of underwater sound absorbing superstructure in a multi-material system according to claim 2, It is characterized in that The S12 comprises the following steps: S121. Assume that each element of the equivalent elastic stiffness matrix of the superstructure layer has a loss factor η, and the η of each element is not necessarily equal. Study the effect of the change of parameter η on the sound absorption coefficient curve of the structure; S122. Equivalent elastic stiffness matrix C of the superstructure in the global coordinate system M =RC i R i , Among them, R is the rotation matrix, which is related to the structural rotation angle α, and the equivalent elastic stiffness matrix C in the local coordinate system is l and anisotropy index γ 1 , deformation characteristic parameter γ 2 , deformation characteristic parameter γ 3 and elastic constant The elastic constant S123. Study on the equivalent elastic parameters C of superstructures that achieve low-frequency broadband underwater sound absorption performance M , obtain the underwater sound absorption superstructure prediction model and the theoretical prediction sound absorption coefficient curve.

5. The method for reverse design of underwater sound absorbing superstructure in a multi-material system according to claim 4, It is characterized in that The S2 comprises the following steps: S21. The topology optimization is performed by using the energy homogenization theory solution algorithm based on SIMP interpolation function to obtain the macroscopic equivalent elastic stiffness matrix D of the superstructure layer. H ; S22. The MMA optimization criterion is used to design multiple constraints and produce more structural details. The hyperbolic tangent projection filter is used to obtain a clear topological structure.

6. The method for inverse design of underwater sound absorbing superstructure in a multi-material system according to claim 5, It is characterized in that The S21 comprises the following steps: S211. Topological optimization of the microscopic unit cell structure of each material point, each unit cell structure is composed of different materials and holes; S212. The design variables of multiple materials and their elastic moduli are combined under the SIMP interpolation function, and the objective function is set as the macroscopic equivalent elastic stiffness matrix D H Reach the set value; S213. When using energy homogenization theory for topology optimization, the constraints on the boundaries are converted into a certain number of explicit constraints between corresponding pairs of nodes on the relative surfaces of the cells to form periodic boundary conditions.

7. The method for reverse design of underwater sound absorbing superstructure in a multi-material system according to claim 5, It is characterized in that The S22 comprises the following steps: S221.MMA optimization criterion designs multiple constraints and generates more structural details. The objective function is the macroscopic equivalent elastic stiffness matrix D H , the value of each element in the elastic stiffness matrix is ​​divided into real and imaginary parts; S222. The real and imaginary parts of each element reach the set value as sub-constraints, and then assembled into one constraint. Therefore, the orthotropic superstructure layer has a total of four constraints, and the multi-material system volume constraints are two; S223. Using hyperbolic tangent projection filtering, the density of each element is filtered to 0 or 1, thereby obtaining a clear topological structure.

8. The method for reverse design of underwater sound absorbing superstructure in a multi-material system according to claim 5, It is characterized in that The S3 comprises the following steps: S31. The topological structure obtained in S22 is processed with CAD software to form zigzag boundaries between different materials, and then imported into COMSOL Multiphysics software for simulation to obtain a sound absorption coefficient curve of the topological structure; S32. Compare the sound absorption coefficient curve obtained in S31 with the theoretically predicted sound absorption coefficient curve in S123 to confirm the feasibility of multi-material topology optimization.

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