An inverse design method for underwater acoustic superstructures in a multi-material system

Abstract

The present invention discloses a reverse design method for an underwater sound-absorbing superstructure in a multi-material system in the field of vibration and noise control technology. The reverse design method for the underwater sound-absorbing superstructure in the multi-material system comprises the following steps: predicting the macroscopic sound-absorbing performance of the superstructure based on the equivalent medium theory; establishing a reverse design method for the topology optimization of the superstructure in the multi-material system based on the energy homogenization theory of the SIMP interpolation function; selecting a suitable material system, and achieving precise design of the multi-material superstructure with the equivalent elastic parameters of the superstructure as the target. Compared with the existing design methods for underwater sound-absorbing superstructures, the present invention can avoid large-scale acoustic-solid coupling finite element calculations, realize the efficient design of the superstructure and good low-frequency broadband sound-absorbing performance; in addition, the design method proposed by the present invention is universal in different multi-material systems.

Description

Technical Field

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

[0002] With the development of modern sonar technology, the problem of acoustic stealth of underwater equipment has become increasingly prominent, increasing the possibility of being hit by underwater weapons such as missiles and torpedoes, and seriously threatening the survival ability 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 mainly two empirical design modes for underwater sound-absorbing superstructures. One is the cavity-type superstructure, which is composed of a rubber matrix embedded with an acoustic cavity. The other is the locally resonant-type superstructure, which is composed of a rubber matrix embedded with locally resonant units. The locally resonant units are usually hard metal-coated soft silicone rubber. At the design method level, designers often rely on artificial experience and use the finite element analysis method 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-physical field problem that requires solving a large-scale acoustic-solid coupling stiffness matrix; on the other hand, it is greatly affected by the initial configuration, and both the design range and the 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, which solves the problems that the existing underwater superstructures have a narrow sound-absorbing frequency band, it is difficult to achieve low frequencies, and the currently imaginable structure range relying solely on manual design is getting smaller and smaller, and the single-material topology optimization design space is limited. The underwater sound-absorbing superstructure designed by this method is more reasonable, meets the high sound-absorbing performance requirements of the sound-absorbing structure with lower frequency and wider bandwidth, can be universal in different multi-material systems, and improves the optimization efficiency at the same time.

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

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

[0006] S1. Predict the macroscopic sound-absorbing performance of the superstructure based on the equivalent medium theory;

[0007] S2. Establish a reverse design method for superstructure topology optimization in a multi-material system based on the energy homogenization theory of the SIMP interpolation function;

[0008] S3. Select a suitable material system and achieve precise design of the multi-material superstructure with the equivalent elastic parameters of the superstructure as the target.

[0009] As an aspect of the reverse design method of the underwater sound absorption superstructure in a multi-material system of the present invention, S1 includes the following steps:

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

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

[0012] As an aspect of the reverse design method of the underwater sound absorption superstructure in a multi-material system of the present invention, studying the stress and strain of particles during the sound wave propagation process from the perspective of micro mechanics in S11 includes the boundary conditions between different media, deducing the analytical relationship between the sound absorption performance of the superstructure model and the macroscopic equivalent mechanical parameters and elastic wave characteristics, and calculating the theoretical predicted sound absorption coefficient curve and prediction model of the underwater sound absorption superstructure.

[0013] As an aspect of the reverse design method of the underwater sound absorption superstructure in a multi-material system of the present invention, S12 includes 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, and study the influence of the change of the parameter η on the sound absorption coefficient curve of the structure;

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

[0016] where R is the rotation matrix, which is related to the structure rotation angle α, and the equivalent elastic stiffness matrix C in the local coordinate system l is related to the anisotropy index γ1, the deformation characteristic parameter γ2, the deformation characteristic parameter γ3 and the elastic constant is related, and the elastic constant

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

[0018] As an aspect of the reverse design method of the underwater sound absorption superstructure in a multi-material system of the present invention, S2 includes the following steps:

[0019] S21. Use the solution algorithm of the energy homogenization theory based on the SIMP interpolation function for topology optimization to obtain the equivalent elastic stiffness matrix D macroscopically of the superstructure layerH ;

[0020] S22. Design multiple constraints using the MMA optimization criterion, which generates more structural details. Then, use the hyperbolic tangent projection filter to obtain a clear topological structure.

[0021] As an aspect of the underwater sound-absorbing metamaterial inverse design method with a multi-material system of the present invention, the S21 includes the following steps:

[0022] S211. Perform topological optimization on the micro unit cell structure of each material point. Each unit cell structure is composed of different materials and pores.

[0023] S212. Combine the design variables of multiple materials with their elastic moduli under the SIMP interpolation function, and set the objective function as the macroscopic equivalent elastic stiffness matrix D H to reach the set value;

[0024] S213. When using the homogenization theory for topological optimization, convert the boundary constraints into a certain number of explicit constraints between the corresponding node pairs on the relative surfaces of the RVE.

[0025] As an aspect of the underwater sound-absorbing metamaterial inverse design method with a multi-material system of the present invention, the S22 includes the following steps:

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

[0027] S222. Reach the set values respectively as sub-constraints, and then assemble them into one constraint. Therefore, the orthotropic metamaterial layer has a total of six constraints, and each constraint has two sub-constraints of real part and imaginary part;

[0028] S223. Use the hyperbolic tangent projection filter, and the density of each element is filtered to 0 or 1, so as to obtain a clear topological structure.

[0029] As an aspect of the underwater sound-absorbing metamaterial inverse design method with a multi-material system of the present invention, the S3 includes the following steps:

[0030] S31. Process the zigzag boundaries between different materials of the topological structure obtained in S22 using CAD software, and import it into the COMSOL Multiphysics software for simulation to obtain the 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 verify the feasibility of the multi-material topological optimization.

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

[0033] The present invention provides a reverse design method for underwater sound-absorbing superstructures in a multi-material system. Compared with the design of single-material superstructures, the design of multi-material superstructures aims to find the optimal material layout within a specified design domain by reasonably distributing multiple different materials in the structure, so as to maximize or minimize certain objectives while satisfying one or more design constraints. In this method, the design space is divided into multiple cells, and each cell can use different materials, thus achieving fine control of the structural performance. By flexibly adjusting the material distribution, underwater low-frequency broadband high sound-absorbing performance can be achieved. The reverse design method for underwater sound-absorbing superstructures in the multi-material system can realize the topological optimization design of the microstructure of multiple materials, obtain the macroscopic equivalent elastic stiffness matrix, and achieve a sound absorption coefficient curve with low-frequency broadband in the underwater sound-absorbing superstructure. Moreover, the reverse design method for underwater sound-absorbing superstructures in the multi-material system has good universality under different multi-material systems, and at the same time can avoid a large number of finite element calculations, improve the optimization efficiency and reduce the calculation cost. Description of the Drawings

[0034] Figure 1 Schematic diagram of a multi-material topology 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 the sound absorption coefficient curves between the structural theoretical prediction and the simulation calculation;

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

[0038] Figure 5 For Figure 4 Comparison of the sound absorption coefficient curves between the structural theoretical prediction and the simulation calculation. Detailed Embodiments

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

[0040] A reverse design method for an underwater sound-absorbing superstructure in a multi-material system provided in this embodiment, the research objects of which include: a rubber layer, a superstructure layer and a rubber layer. The frames are all columnar structures, and the superstructure layer is composed of soft material 1, hard material 2 and holes, specifically as Figure 1 shown. The energy homogenization method based on the SIMP interpolation function is used to perform topology optimization on the microscopic unit cell structures of each material, realizing a stable transition from one material to another until the required material properties are met. The reverse design method for the underwater sound-absorbing superstructure in the multi-material system includes the following steps:

[0041] S1. Predict the macroscopic sound-absorbing performance of the superstructure based on the equivalent medium theory;

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

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

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

[0045] Among them, S12 includes the following specific steps:

[0046] S121. Predict the macroscopic sound-absorbing performance of the superstructure based on the equivalent medium theory. 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, and study the influence of the change of the parameter η on the sound-absorbing coefficient curve of the structure;

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

[0048] where R is a rotation matrix, related to the structural rotation angle α, and the equivalent elastic stiffness matrix C in the local coordinate system l is related to the anisotropy index γ1, the deformation characteristic parameter γ2, the deformation characteristic parameter γ3, and the elastic constants along the main axis directions . After adding the assumed loss factor η, η becomes a newly added independent variable .

[0049] S123. Study the equivalent elastic parameters C of the superstructure for realizing low-frequency broadband underwater acoustic absorption performance M , and obtain the prediction model of the underwater acoustic absorption superstructure and the theoretical predicted acoustic absorption coefficient curve

[0050] S2. Based on the energy homogenization theory of the SIMP interpolation function, establish a reverse design method for the topology optimization of the superstructure in a multi-material system; among them, the multi-materials can be composed of soft material rubber, hard material resin holes, and metal materials

[0051] S2 includes the following specific steps

[0052] S21. Use the solution algorithm based on the energy homogenization theory of the SIMP interpolation function for topology optimization to obtain the equivalent elastic stiffness matrix D of the superstructure layer macroscopically H ;

[0053] S21 includes the following specific steps

[0054] S211. Use the energy homogenization theory to perform topology optimization on the microscopic unit cell structure of each material point. Each cell structure is composed of different materials and holes

[0055] S212. Combine the design variables of multiple materials with their elastic moduli under the SIMP interpolation function. At the same time, the repetition of such cells with holes in space causes the anisotropic characteristics of the macroscopic properties of the materials. Set the objective function as the macroscopic equivalent elastic stiffness matrix D H to reach the set value

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

[0057] Among them, the multi-material topology optimization structure is specifically as Figure 1 shown, 1 is soft rubber material, and 2 is hard glass fiber nylon resin matrix material; the present invention has universality under a multi-material system, and the same equivalent elastic stiffness matrix D H Under the target, the multi-material topology optimization structure composed of soft rubber 5 and carbon fiber nylon matrix 6 is specifically as Figure 4 shown, and can achieve a wide sound absorption performance curve with an average sound absorption coefficient > 0.8 in the range of 300 - 3000H.

[0058] S22. Using the MMA optimization criterion to design multiple constraints and generating more structural details, and using hyperbolic tangent projection filtering to obtain a clear topological structure.

[0059] S22 includes the following steps:

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

[0061] S222. Reach the set values respectively as sub-constraints, and then assemble them into a constraint. Therefore, the orthotropic superstructure layer has a total of four constraints, and each constraint has two sub-constraints of real part and imaginary part. Coupled with the volume constraint of the multi-material system, six constraints or even more can be achieved;

[0062] S223. Using hyperbolic tangent projection filtering, the density of each element is filtered to 0 or 1, avoiding problems such as checkerboards, intermediate densities, and grayscales in the optimization, so as to obtain a clear topological structure.

[0063] S3. Select a suitable material system, and take the equivalent elastic parameters of the superstructure as the target to achieve precise design of the multi-material superstructure.

[0064] S3 includes the following steps:

[0065] S31. Process the zigzag boundary between different materials for the topological structure obtained in step S22 using CAD software, and import it into the COMSOL Multiphysics software for simulation to obtain the sound absorption coefficient curve of the topological structure;

[0066] Since the structural topology is determined by the pseudo-density defined by elements, a zigzag boundary representation will be generated. Therefore, it is necessary to import the topology structure obtained by S22 into AutoCAD for boundary processing, and convert it into a microstructure unit with a smooth structural boundary and a clear material interface, so as to avoid the failure to convert into solid materials due to the lack of a closed curve when imported into the COMSOL simulation software;

[0067] In the COMSOL Multiphysics software, the total sound pressure P of surface I as shown in Figure 2 is obtained through frequency-domain simulation calculation. Among them, the total sound pressure P includes the incident sound pressure P i and the reflected sound pressure P r . Among them, the incident sound pressure P i is a known condition, and thus the sound absorption coefficient α can be determined:

[0068] Figure 2 The established simulation model from top to bottom is the water area 3, the rubber layer 2, and the superstructure layer. Among them, the superstructure layer consists of a multi-material system topology optimization structure composed of a soft material 1 and a hard material 2. Taking the fiberglass nylon resin hard material in the superstructure layer as an example, the elastic modulus E1 = 6e9 Pa, the density is 1250 kg / m 3 , and the Poisson's ratio is 0.3; the elastic modulus of the soft material E2 = (1 + 0.8i) * 30e6 Pa, the density is 1300 kg / m 3 , and the Poisson's ratio is 0.495. The soft material provides a loss factor η to enhance the dissipation of the reflected sound wave entering it. The density of the rubber layer is 1160 kg / m 3 , the longitudinal wave velocity is (1500 + 75i) m / s, and the transverse wave velocity is (98 + 27i) m / s. The superstructure layer is specifically as shown in Figure 2 . Its unit periodic structure rotates 60°, and it needs to be accurately intercepted into a continuous structure. Multiple Bloch-Floquet periodic boundary conditions need to be established in the solid mechanics physical field of COMSOL Multiphysics to ensure the consistency of the displacement field changes on both sides of the structure. The topology structure obtained by S22 is simulated and calculated to obtain its sound absorption coefficient curve.

[0069] S32. Compare the sound absorption coefficient curve obtained in S31 with the theoretically predicted sound absorption coefficient curve in S123. The results are basically the same, which verifies the feasibility of multi-material topology optimization. The topology optimization takes five minutes, and the simulation calculation takes one and a half hours, which greatly reduces the calculation cost compared with the traditional topology optimization method.

[0070] The comparison of the two groups of simulation results shows that the inverse design method of the underwater sound absorption superstructure under this multi-material system can successfully design the underwater sound absorption superstructure with low-frequency broadband sound absorption performance under different multi-material systems.

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

[0072] Finally, it should be noted that although the present invention has been described with reference to the current specific embodiments, those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present invention and are not intended to limit 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 of the above embodiments are within the scope of the spirit of the present invention, they will fall within the scope of the claims of the present invention.

Claims

1. An inverse design method for underwater sound absorption superstructures in a multi-material system, characterized in that, It includes the following steps: S1. Predict the macroscopic sound absorption performance of the superstructure based on the equivalent medium theory; S1 includes the following steps: S11. Construct an underwater sound absorption equivalent medium model and study the equivalent parameters of the particles during the acoustic wave propagation process from the perspective of the 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; S2. Based on the energy homogenization theory of the SIMP interpolation function, establish an inverse design method for the topology optimization of the superstructure under a multi-material system; S2 includes the following steps: S21. Perform topology optimization using a solution algorithm based on the energy homogenization theory of the SIMP interpolation function to obtain the equivalent elastic stiffness matrix D of the superstructure layer macroscopically H ; S22. Use the MMA optimization criterion to design multiple constraints and generate more structural details, and use the hyperbolic tangent projection filtering to obtain a clear topological structure; S3. Select a suitable material system, take the equivalent elastic parameters of the superstructure as the target, achieve precise design of the multi-material superstructure, and obtain a high sound absorption performance with an average sound absorption coefficient > 0.8 in the low-frequency band of 300 - 3000 Hz.

2. The reverse design method of an underwater sound absorption superstructure in a multi-material system according to claim 1, characterized in that Studying the equivalent parameters of the particles during the acoustic wave propagation process from the perspective of the microscopic cell structure in S11 and considering the actual boundary conditions including the boundary conditions between different media, deriving the analytical relationship between the sound absorption performance of the superstructure model and the macroscopic equivalent mechanical parameters and elastic wave characteristics, and calculating the theoretical predicted sound absorption coefficient curve and prediction model of the underwater sound absorption superstructure.

3. A reverse design method for an underwater sound absorption superstructure in a multi-material system according to claim 1, characterized in that, The S12 includes 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, and study the influence of the change of the parameter η on the sound absorption coefficient curve of the structure; S122. Equivalent Elastic Stiffness Matrix C in the Global Coordinate System of the Superstructure M = RC l R T , wherein, R is a rotation matrix, related to the structural rotation angle α, and the equivalent elastic stiffness matrix C in the local coordinate system l is related to the anisotropy index γ1, the deformation characteristic parameter γ2, the deformation characteristic parameter γ3, and the elastic constants and the elastic constants S123. Research on the equivalent elastic parameter C of the superstructure for realizing low-frequency broadband underwater sound absorption performance M , and obtain the prediction model of the underwater sound absorption superstructure and the theoretical predicted sound absorption coefficient curve.

4. A reverse design method for an underwater sound absorption superstructure in a multi-material system according to claim 1, characterized in that The S21 includes the following steps: S211. Conduct topology optimization on the microscopic unit cell structure of each material point, and each 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 the energy homogenization theory for topology optimization, convert the boundary constraints into a certain number of explicit constraints between the corresponding node pairs on the relative surfaces of the cells to form periodic boundary conditions.

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

6. A reverse design method for an underwater sound absorption superstructure in a multi-material system according to claim 1, characterized in that The S3 includes the following steps: S31. Process the zigzag boundary between different materials of the topological structure obtained in S22 through CAD software, import it into the COMSOL Multiphysics software for simulation, and obtain the sound absorption coefficient curve of the topological structure; S32. Compare the sound absorption coefficient curve obtained in S31 with the theoretical predicted sound absorption coefficient curve in S123 to confirm the feasibility of the multi-material topology optimization.

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