Chiral super-lattice decoupling wave, design method and acoustic vibration control structure

Abstract

The present application relates to underwater vibration noise control technical field, disclose a kind of chiral superstructure decoupling tile, design method and acoustic vibration control structure, the acoustic performance of decoupling tile is jointly determined by including equivalent bulk modulus, equivalent shear modulus and equivalent density;Design goal is to make the shape preserving deformation eigenvalue of chiral metamaterial cell unit less than any one equivalent volume deformation eigenvalue of chiral metamaterial cell unit;Topology optimization, generate the optimized cell structure with chiral characteristics, the shape preserving deformation eigenvalue minimization is used as optimization goal in topology optimization, with the material volume fraction of chiral metamaterial cell unit as constraint condition, the optimal cell configuration is obtained by iterative calculation, and the bending rotary arm extends outward from the center node and has curvature and is rotationally symmetric around the center node;Homogenization calculation is carried out, and equivalent bulk modulus and equivalent shear modulus are extracted to verify whether the performance criterion is met;Periodic arrangement is carried out in two-dimensional plane, and chiral superstructure decoupling tile is formed.

Description

Technical Field

[0001] This invention relates to the field of underwater vibration and noise control technology, and in particular, to a chiral metastructure decoupling tile, its design method, and its acoustic and vibration control structure. Background Technology

[0002] In underwater operations and navigation, effectively controlling the vibration and noise radiation of underwater structures is crucial for improving acoustic concealment, ensuring the performance of acoustic equipment, and meeting increasingly stringent environmental requirements. Typically, applying a decoupling layer to the structural surface is a key technique for suppressing vibration transmission and reducing sound radiation. This type of decoupling layer introduces specific mechanical impedance matching or impedance mismatch between the structure and its surrounding fluid medium, thereby regulating the vibration energy transmission path and achieving noise reduction.

[0003] Currently, traditional decoupling layers used in engineering applications mainly fall into two categories: one is a cover layer made of homogeneous materials such as rubber and polymers; the other is a periodic structure with simple, regular cavities (such as a transversely penetrating cylindrical cavity). Compared with homogeneous materials, structures containing simple cavities can reduce equivalent stiffness to a certain extent, thus exhibiting better vibration isolation and decoupling performance in specific frequency bands. However, with the increasing demand for wideband, high-efficiency noise control, especially for vibration and noise control in the mid-to-low frequency bands, the performance bottlenecks of traditional structures are becoming increasingly apparent. Studies have shown that traditional decoupling layers based on simple configurations such as cylindrical cavities have limited decoupling effectiveness in the low-frequency band below 400Hz, and their ability to attenuate radiated sound power within the overall operating frequency band has an upper limit, making it difficult to meet the growing demand for high-performance acoustic and vibration control.

[0004] From the perspective of continuum mechanics, the core of decoupling performance lies in its macroscopic equivalent mechanical parameters, especially the equivalent bulk modulus. A lower equivalent bulk modulus means that the structure is more "flexible" when resisting hydrostatic pressure or volume deformation, effectively suppressing vibrational energy transmitted in the form of longitudinal waves. However, while pursuing low bulk modulus, existing decoupling layer structures (including structures with simple cavities) often fail to achieve deep optimization and reconstruction of the intrinsic deformation modes of the material in their structural form. This makes it difficult to further significantly reduce their equivalent bulk modulus, or it comes at the cost of excessively sacrificing the overall stiffness and stability of the structure, thus limiting their performance in a wide frequency band, especially in the low frequency range.

[0005] Therefore, there is an urgent need in this field for a novel decoupling structure design that can provide stronger vibration suppression and acoustic radiation control capabilities over a wide frequency band, especially in the mid-to-low frequency range. At the same time, through its structural design, it can achieve a lower equivalent bulk modulus without affecting the necessary structural stability, thereby breaking through the performance limitations of traditional designs and meeting the more stringent requirements of underwater acoustic and vibration control applications. Summary of the Invention

[0006] This invention provides a chiral metastructure decoupling tile, its design method, and its acoustic vibration control structure. By combining intrinsic mode modulation theory with topology optimization design, a chiral, rotationally symmetric curved spiral arm structure is constructed at the unit cell scale. This results in the equivalent bulk modulus of the unit cell being significantly lower than its equivalent shear modulus. Thus, in a wide frequency band, especially in the mid-to-low frequency range, an efficient structural deformation and energy dissipation mechanism is used to effectively suppress matrix vibration and strongly block longitudinal wave transmission. This solves the technical problem that traditional decoupling structures have insufficient decoupling performance in the low-frequency range and are difficult to achieve efficient acoustic vibration control in a wide frequency band.

[0007] According to one aspect of the present invention, a design method for a chiral metamaterial decoupling tile is provided, comprising the following steps: S100, establishing a mechanical model of the decoupling tile with the design goal of reducing the equivalent bulk modulus of the decoupling tile and suppressing the transmission of vibrational longitudinal waves, wherein the acoustic performance of the decoupling tile is jointly determined by multiple equivalent mechanical parameters including the equivalent bulk modulus, the equivalent shear modulus, and the equivalent density; S200, based on the intrinsic mode modulation theory, setting the design goal of the chiral metamaterial unit cell of the chiral metamaterial decoupling tile, wherein the design goal is to make the conformal deformation characteristic value of the chiral metamaterial unit cell... Less than any isochoric deformation eigenvalue of the chiral metamaterial unit cell S300: Based on the design goals set in step S200, perform topology optimization on the initial unit cell model to generate an optimized unit cell structure with chiral characteristics. Topology optimization uses conformal deformation eigenvalues. Minimization is the optimization objective, and the volume fraction of the chiral metamaterial unit cell is used as a constraint. The optimal unit cell configuration is obtained through iterative calculation. The cross-sectional shape of the optimized unit cell structure includes a central node and multiple curved spiral arms. The curved spiral arms extend outward from the central node and have curvature, and are arranged rotationally symmetrically around the central node. In step S400, the optimized unit cell structure obtained in step S300 is homogenized, and the equivalent bulk modulus is extracted. With equivalent shear modulus And verify whether it satisfies The performance criteria of step S400; S500, the optimized cell structure that meets the performance criteria of step S400 is periodically arranged in a two-dimensional plane to generate a cell array to form the overall structure of the chiral meta-decoupling tile.

[0008] According to another aspect of the present invention, a chiral metamaterial decoupling tile is also provided, which is designed and fabricated using the above-described chiral metamaterial decoupling tile design method. The tile comprises periodically arranged chiral metamaterial unit cells. The design of the chiral metamaterial unit cells is based on the intrinsic mode control theory. Topological optimization design is performed on the cell morphology of the chiral metamaterial unit cells to ensure that the eigenvalues ​​corresponding to the two isochoric deformations in the intrinsic modes of the cell morphology are unequal, and to ensure that the conformal deformation eigenvalues ​​are... Much smaller than one of the isochoric deformation eigenvalues ,Right now This reduces the equivalent bulk modulus of the decoupling tile, effectively suppressing matrix vibration and strongly blocking longitudinal wave transmission, thereby significantly improving the overall decoupling performance.

[0009] Furthermore, the structure of the chiral metamaterial unit cell is as follows: under standard homogenization calculation conditions, the conformal deformation eigenvalues ​​of the chiral metamaterial unit cell are... With one of the isochoric deformation eigenvalues The ratio between them satisfies ,in and The stiffness matrix of the chiral metamaterial unit cell under periodic boundary conditions is obtained by eigenmode decomposition. Corresponding to a unique conformal deformation mode that causes a change in unit cell volume, It is the mode with the largest eigenvalue among all isochoric deformation modes that do not cause volume change.

[0010] Furthermore, in order to achieve an extremely low equivalent bulk modulus in single-phase solid materials while maintaining a certain shear stiffness, a chiral rotationally symmetric curved spiral arm structure is used. Through the rotation-expansion coupled deformation mechanism of the curved spiral arm, the chiral metamaterial cell unit can achieve volume shrinkage under hydrostatic pressure through the bending and rotation of the curved spiral arm, corresponding to the conformal deformation characteristic value of the low expansion mode. In the preset shear mode, the bending arm mainly undergoes tensile deformation, requiring more energy and corresponding to a higher isochoric deformation characteristic value of the shear feature. By optimizing the curvature and rotational symmetry of the curved spiral arm, the degeneracy of the shearing mode is broken, thereby achieving... The goal is to ultimately achieve excellent longitudinal wave blocking and decoupling performance.

[0011] Furthermore, the cross-sectional shape of the chiral metamaterial unit cell consists of a central node and at least three curved spiral arms. One end of each curved spiral arm is connected to the central node, while the other end is a free end that extends away from the central node. The curved spiral arms have a preset, non-zero constant curvature or a gradually changing curvature along the extension path. The multiple curved spiral arms are arranged in a rotationally symmetrical manner around the central node so that when the chiral metamaterial unit cell is subjected to hydrostatic pressure, the coordinated bending and rotation of the curved spiral arms preferentially induces a low-stiffness expansion deformation mode, thereby achieving a chiral metamaterial unit cell with an equivalent bulk modulus that is significantly lower than the equivalent shear modulus.

[0012] Furthermore, the structure of the chiral metamaterial unit cell is as follows: a square region with a side length of 8mm-15mm is established in a two-dimensional plane as a single unit cell design domain, and the geometric center of the square region is set as the origin of the coordinate system; a central node is set at the geometric center of the unit cell, and the central node is a square region with a side length of 4mm-8mm.

[0013] Furthermore, the curved spiral arm is formed by two circular arcs and a connecting line segment; in specific construction, a corner point of the square region of the central node is selected as the starting point of the first circular arc, and the offset point of the midpoint of the corresponding boundary of the unit cell design domain is selected as the ending point of the first circular arc. The radius of the first circular arc is 2mm-5mm; the starting point and ending point of the first circular arc are respectively along... x shaft or y The axis is translated by 1mm-3mm, and the starting point and ending point after translation are used as the starting point and ending point of the second arc, respectively. The radius of the second arc is the same as that of the first arc. The corresponding endpoints of the first arc and the second arc are connected by connecting line segments to form a two-dimensional solid cross section of a single spiral arm.

[0014] Furthermore, each single curved spiral arm is rotated 90°, 180°, and 270° around the geometric center of the cell design domain to obtain the remaining three curved spiral arms. Thus, the four curved spiral arms are circumferentially distributed around the central node, forming a two-dimensional cross-sectional structure of the chiral metamaterial cell unit. Each curved spiral arm has a consistent deflection direction, which makes the chiral metamaterial cell unit exhibit obvious unidirectional rotation characteristics as a whole. This unidirectional rotation characteristic geometric configuration defines the distribution boundary, spiral arm curvature trend, and internal pore region morphology of the chiral metamaterial within the cell design domain, thereby ensuring that the obtained chiral metamaterial cell unit structure has stable and repeatable geometric characteristics.

[0015] Furthermore, the periodically arranged chiral metamaterial cell units form periodically arranged chiral structural cavities.

[0016] According to another aspect of the present invention, an acoustic vibration control structure is also provided, comprising the aforementioned chiral meta-decoupling tile; comprising, arranged from bottom to top: a base structure for bearing external excitation force; a chiral meta-decoupling tile layer, laid on the surface of the base structure, with chiral meta-decoupling tiles arranged in an array inside; and a fluid medium layer located on the side of the chiral meta-decoupling tile layer away from the base structure, wherein an acoustic-structural boundary is formed between the fluid medium layer and the chiral meta-decoupling tile layer; when the base structure is subjected to point force excitation to generate vibration and radiate sound waves outward, the chiral meta-decoupling tile layer plays a role in vibration isolation and vibration suppression, and the chiral structural cavity of the chiral meta-decoupling tile layer will generate local rotation and waveform transformation when subjected to force, significantly increasing the energy loss of vibration in the transmission process, thereby reducing the radiated acoustic power transmitted to the fluid medium layer.

[0017] The present invention has the following beneficial effects:

[0018] 1. With reducing the equivalent bulk modulus as the core design objective and directly linking the design objective with the suppression of longitudinal wave transmission, the design process always addresses the key physical contradiction in underwater acoustic and vibration control, namely, that longitudinal waves are the main carrier of vibration energy transmission. By establishing a model based on equivalent mechanical parameters, a quantifiable and calculable engineering basis is provided for subsequent optimization, transforming the design process from traditional experience-based trial and error to forward design driven by a physical model.

[0019] 2. When setting specific design goals, the intrinsic mode control theory is introduced and transformed into specific, numerically operable microscopic design criteria. That is, the conformal deformation eigenvalue of the chiral metamaterial unit cell is required to be less than any of its isochoric deformation eigenvalues. This criterion defines the mechanical behavior of easy volume compression and resistance to shape change from the physical essence of the deformation mode. It provides a unique and accurate objective function for subsequent topology optimization. It is a deep-level control at the deformation mode level of the unit cell and is the theoretical basis for realizing anomalous mechanical properties. In turn, it guides the structure to evolve into a geometric configuration that can realize the predetermined intrinsic mode relationship.

[0020] 3. In the specific steps of structure generation, minimizing the conformal deformation eigenvalues ​​is taken as the goal of topology optimization, supplemented by material volume fraction constraints. This optimization goal directly drives the computational model to find a geometric configuration that minimizes the energy required for uniform volume deformation of the unit cell under hydrostatic pressure. This process naturally rejects symmetrical, solid, or simple cavity structures that exhibit high stiffness during volume deformation, thus spontaneously tending to generate chiral topologies that can absorb volume strain through complex movements such as bending and rotation of internal components. The optimized structure containing rotationally symmetric bending spiral arms is the inevitable result of this optimization process. As a result, its chirality and bending characteristics together constitute the geometric basis for achieving a low bulk modulus: the bending helical arm preferentially buckles and rotates under compression rather than undergoes axial compression, thereby transforming the macroscopic longitudinal compressive strain into local rotational and shear strain. This is the macroscopic structural manifestation of the microscopic mechanism of "conformal deformation characteristic value is less than isochoric deformation characteristic value". The homogenization calculation and performance criterion verification in step S400 play a role in closed-loop verification and quality control, ensuring that the generated microscopic cell structure does indeed have the property of "equivalent bulk modulus is less than equivalent shear modulus" on a macroscopic scale, thus guaranteeing the final realization of the design goal.

[0021] 4. The validated optimized unit cell structure is periodically arranged to extend and integrate the superior performance of individual unit cells on a macroscopic scale. The periodic arrangement ensures the uniformity and predictability of the overall structure, enabling the macroscopic decoupling tile, composed of thousands of microscopic chiral units, to exhibit the desired and significantly reduced equivalent bulk modulus. This complete method chain, from microscopic configuration design to macroscopic performance verification and then to macroscopic structure integration, ensures that the chiral metastructure decoupling tile of the final product can effectively dissipate the energy of the incident longitudinal wave in the high-damping matrix material inside the decoupling tile through the synergistic tension-torsion coupling and waveform conversion mechanism caused by the periodically arranged chiral units inside the structure.

[0022] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of a chiral metastructure decoupling tile according to a preferred embodiment of the present invention; Figure 2 This is one of the structural schematic diagrams of the acoustic vibration control structure of a preferred embodiment of the present invention; Figure 3This is a second schematic diagram of the acoustic vibration control structure of a preferred embodiment of the present invention; Figure 4 This is a comparison curve of the radiated acoustic power of the chiral metastructure decoupling tile, the smooth plate, and the cylindrical decoupling tile at different frequencies, according to a preferred embodiment of the present invention.

[0024] Legend: 1. Base structure; 2. Chiral metastructure decoupling layer; 3. Fluid medium layer.

[0025] 21. Center node; 22. Bending spiral arm. Detailed Implementation

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0027] The design method of the chiral metamaterial decoupling tile in this embodiment includes the following steps: S100, with the design goal of reducing the equivalent bulk modulus of the decoupling tile and suppressing the transmission of vibrational longitudinal waves, a mechanical model of the decoupling tile is established, wherein the acoustic performance of the decoupling tile is jointly determined by multiple equivalent mechanical parameters including equivalent bulk modulus, equivalent shear modulus, and equivalent density; S200, based on the intrinsic mode modulation theory, the design goal of the chiral metamaterial unit cell of the chiral metamaterial decoupling tile is set, the design goal being to make the chiral metamaterial unit cell exhibit conformal deformation characteristic values. Less than any isochoric deformation eigenvalue of the chiral metamaterial unit cell S300: Based on the design goals set in step S200, perform topology optimization on the initial unit cell model to generate an optimized unit cell structure with chiral characteristics. Topology optimization uses conformal deformation eigenvalues. Minimization is the optimization objective, and the volume fraction of the chiral metamaterial unit cell is used as a constraint. The optimal unit cell configuration is obtained through iterative calculation. The cross-sectional shape of the optimized unit cell structure includes a central node 21 and multiple curved spiral arms 22. The curved spiral arms 22 extend outward from the central node 21 and have curvature, and are arranged in a rotationally symmetric manner around the central node 21. S400: The optimized unit cell structure obtained in step S300 is homogenized, and the equivalent bulk modulus is extracted. With equivalent shear modulus And verify whether it satisfies The performance criteria of step S400 are used to periodically arrange the optimized cell structure that meets the performance criteria in step S400 in a two-dimensional plane to generate a cell array, thereby forming the overall structure of the chiral metastructure decoupling tile. The design method of the chiral metastructure decoupling tile of this invention takes reducing the equivalent bulk modulus as the core design goal and directly links the design goal with the suppression of longitudinal wave transmission. This ensures that the design process always addresses the key physical contradiction in underwater acoustic and vibration control, namely, that longitudinal waves are the main carrier of vibration energy transmission, and traditional decoupling structures are difficult to effectively block them. By establishing a model based on equivalent mechanical parameters, a quantifiable and computable engineering basis is provided for subsequent optimization, transforming the design process from traditional trial and error based on experience to forward design driven by a physical model. When setting specific design goals, the intrinsic mode control theory is introduced and transformed into a specific, numerically operable microscopic design criterion, which requires that the conformal deformation eigenvalue of the chiral metamaterial unit cell be less than any of its isochoric deformation eigenvalues. This criterion defines the mechanical behavior of easy volume compression and resistance to shape change from the physical nature of the deformation mode, providing a unique and accurate objective function for subsequent topology optimization. It is a deep-level control at the deformation mode level of the unit cell, and is the theoretical basis for achieving anomalous mechanical properties (decoupling of low bulk modulus and relatively high shear modulus), thereby guiding the structure to evolve into a geometric configuration that can realize the predetermined intrinsic mode relationship. In the specific steps of structure generation, minimizing the conformal deformation eigenvalues ​​is taken as the goal of topology optimization, supplemented by material volume fraction constraints. This optimization goal directly drives the computational model to find a geometric configuration that minimizes the energy required for uniform volume deformation of the unit cell under hydrostatic pressure. This process naturally rejects symmetrical, solid, or simple cavity structures that exhibit high stiffness during volume deformation, thus spontaneously tending to generate chiral topologies that can absorb volume strain through complex movements such as bending and rotation of internal components. The optimized structure containing rotationally symmetric bending spiral arms 22 is the inevitable result of this optimization process. Its chirality and bending characteristics together constitute the geometric basis for achieving low bulk modulus: the bending helical arm 22 preferentially buckles and rotates under pressure, rather than compressing axially, thereby transforming the macroscopic longitudinal compressive strain into local rotational and shear strain. This is the macroscopic structural manifestation of the microscopic mechanism of "conformal deformation characteristic value is less than isochoric deformation characteristic value". The homogenization calculation and performance criterion verification in step S400 play a closed-loop verification and quality control role, ensuring that the generated microscopic cell structure does indeed have the property of "equivalent bulk modulus is less than equivalent shear modulus" on a macroscopic scale, thus guaranteeing the final realization of the design goal.The validated optimized unit cell structure is periodically arranged, extending and integrating the superior performance of individual unit cells on a macroscopic scale. The periodic arrangement ensures the uniformity and predictability of the overall structure, enabling the macroscopic decoupling tile, composed of thousands of microscopic chiral units, to exhibit the desired and significantly reduced equivalent bulk modulus. This complete method chain, from microscopic configuration design to macroscopic performance verification and then to macroscopic structural integration, ensures that the chiral metastructure decoupling tile of the final product can effectively dissipate the energy of the incident longitudinal wave in the high-damping matrix material inside the decoupling tile through the synergistic tension-torsion coupling and waveform conversion mechanism caused by the periodically arranged chiral units inside the structure. This invention provides a systematic, theory-driven, and precisely achievable innovative design process for chiral metastructure decoupling tiles. Starting from the core problem of underwater acoustic vibration control, it sets disruptive microscopic performance targets through intrinsic mode modulation theory and automatically generates optimal unit cells with specific chiral spiral arm configurations to achieve these targets using topology optimization technology. Finally, through performance verification and arraying, macroscopic decoupling tiles are constructed. The implementation of this invention can directly and reliably obtain a chiral metastructure decoupling tile with low equivalent bulk modulus, thus providing a fundamental and designable structural solution for efficiently suppressing matrix vibration, blocking longitudinal wave transmission, and achieving wideband (especially low-frequency) acoustic radiation attenuation.

[0028] like Figure 1 As shown, the chiral metamaterial decoupling tile of this embodiment is designed and fabricated using the aforementioned chiral metamaterial decoupling tile design method. It comprises periodically arranged chiral metamaterial unit cells. The design of the chiral metamaterial unit cells is based on the intrinsic mode control theory. Through topological optimization design of the cell morphology of the chiral metamaterial unit cells, the eigenvalues ​​corresponding to the two isochoric deformations in the intrinsic mode of the cell morphology are made unequal, and the conformal deformation eigenvalues ​​are... Much smaller than one of the isochoric deformation eigenvalues ,Right now This reduces the equivalent bulk modulus of the decoupling tile, effectively suppressing matrix vibrations and strongly blocking longitudinal wave propagation, thus significantly improving the overall decoupling performance. The chiral metamaterial decoupling tile of this invention features periodically arranged chiral metamaterial unit cells. These unit cells are obtained through topology optimization design driven by a specific objective, based on intrinsic mode control theory. The eigenvalues ​​corresponding to the two isochoric deformation modes of the chiral metamaterial unit cells are unequal, breaking the degeneracy of shear modulus in traditional isotropic materials and endowing the structure with anisotropic deformation response potential. The conformal deformation eigenvalues ​​of the chiral metamaterial unit cells... Designed to be much smaller than one of the isochoric deformation eigenvalues These two features work together to form the fundamental mechanism by which this invention solves the performance bottleneck of traditional decoupling tiles. More specifically, the conformal deformation characteristic value... Much smaller than the eigenvalue of isochoric deformation This means that the energy required for the chiral metamaterial cell unit to undergo volumetric deformation (conformal deformation) in resistance to uniform hydrostatic pressure is much lower than the energy required for shear deformation (isochoric deformation) in resistance to shape change in a specific direction. This microscopic, intrinsic stiffness mismatch is the intrinsic reason for achieving the mechanical properties of low equivalent bulk modulus and relatively high equivalent shear modulus. The significant reduction in equivalent bulk modulus directly corresponds to the structure exhibiting extremely low dynamic stiffness when subjected to compression waves (longitudinal waves) along its thickness direction. This effectively reduces the resonant frequency of the coupling system "base layer-decoupling tile-fluid medium" and reflects or blocks most of the incident longitudinal wave energy before the decoupling tile layer, achieving a strong barrier to longitudinal wave transmission. The structure, composed of periodically arranged chiral metamaterial unit cells, possesses a unique non-centrosymmetric geometry formed by curved spiral arms 22, which excites a strong tension-torsion coupling effect under external excitation. When vibration is transmitted in the form of longitudinal waves, the longitudinal compressive strain forces the curved spiral arms 22 to produce coordinated bending and rotation, thereby inducing significant local shear deformation. This forced conversion mechanism from longitudinal strain to shear strain, determined by geometric chirality, efficiently converts the longitudinal waves, which originally have strong penetrating power and are difficult to attenuate in layered structures, into shear waves that are easily dissipated as heat energy in the damping matrix material. This process synergistically amplifies the vibration isolation effect brought about by the low bulk modulus, achieving effective suppression of matrix vibration. This invention relates to a chiral metastructure decoupling tile. Through a periodic cell structure with a specific chiral morphology designed based on intrinsic mode modulation theory, it achieves extreme decoupling of conformal deformation stiffness and isochoric deformation stiffness, thereby obtaining extremely low equivalent bulk modulus and controllable equivalent shear modulus. This unique combination of performance enables the decoupling tile to significantly suppress structural vibration and radiated noise in a wide frequency band, especially in the low-to-mid frequency band where traditional decoupling structures are ineffective, by using a dual synergistic mechanism of reducing system stiffness to isolate longitudinal waves and inducing waveform conversion to dissipate energy. This solves the technical problem of insufficient broadband acoustic vibration control performance.

[0029] like Figure 1 As shown, in this embodiment, the structure of the chiral metamaterial unit cell is: under standard homogenization calculation conditions, the conformal deformation characteristic value of the chiral metamaterial unit cell is... With one of the isochoric deformation eigenvalues The ratio between them satisfies ,in and The stiffness matrix of the chiral metamaterial unit cell under periodic boundary conditions is obtained by eigenmode decomposition. Corresponding to a unique conformal deformation mode that causes a change in unit cell volume, This is the mode with the largest eigenvalue among all isochoric deformation modes that do not cause volume change. A precise and quantifiable intrinsic mechanical property criterion is proposed for the structure of chiral metamaterial unit cells, requiring their conformal deformation eigenvalues ​​to be... With the largest isochoric deformation eigenvalue The ratio is less than 0.1; this specific ratio ( ( ) is a rigorous definition of the degree of anomalous mechanical behavior of chiral metamaterial unit cells. From the level of the inherent deformation mode stiffness (i.e., eigenvalues) of the cell, it directly and quantitatively ensures that the cell must macroscopically exhibit an extremely low equivalent bulk modulus; because the conformal deformation eigenvalues It directly dominates the volumetric stiffness of the material, and the largest isochoric deformation characteristic value This reflects the material's ability to resist shear deformation in the optimal direction; much smaller (The difference in magnitude is more than ten times), which means that compared to the optimal directional shear deformation of chiral metamaterial cell units, chiral metamaterial cell units are more likely to undergo uniform volume compression. This stiffness decoupling is a sufficient and necessary intrinsic condition for achieving the characteristic that the equivalent bulk modulus is significantly lower than the equivalent shear modulus. Quantitative structural characteristics provide a deterministic micromechanical guarantee for the extraordinary performance of decoupling tiles. Chiral metamaterial unit cells that meet this condition must be structured to efficiently convert externally applied hydrostatic pressure (or normal dynamic excitation) into other deformation modes of non-volume deformation within the structure, such as absorbing volumetric strain through bending, rotation, etc., rather than rigidly resisting it with the compressive stiffness of the material itself. This micro-deformation mechanism is the root cause of the low equivalent bulk modulus of chiral metamaterial unit cells. Periodically arranging these chiral metamaterial unit cells with specific intrinsic properties to form decoupling tiles can ensure that the entire decoupling tile inherits and amplifies this mechanical property, thereby exhibiting extremely low normal dynamic stiffness in the acoustic vibration system composed of the matrix and fluid medium, effectively reducing the natural frequency of the system, and creating a strong impedance mismatch for vibration energy propagating in the form of longitudinal waves, achieving efficient vibration isolation and acoustic wave blocking.

[0030] like Figure 1 As shown, in this embodiment, in order to achieve an extremely low equivalent bulk modulus in a single-phase solid material while maintaining a certain shear stiffness, starting from the chiral rotationally symmetric curved spiral arm 22 structure, the chiral metamaterial cell unit can achieve volume shrinkage under hydrostatic pressure through the bending and rotation of the curved spiral arm 22 via the rotation-expansion coupled deformation mechanism of the curved spiral arm 22, corresponding to the low expansion mode conformal deformation characteristic value. In the preset shear mode, the bending arm 22 mainly undergoes tensile deformation, requiring more energy and corresponding to a higher isochoric deformation characteristic value of the shear feature. By optimizing the curvature and rotational symmetry of the bending spiral arm 22, the degeneracy of the shearing mode is broken, thereby achieving... The goal is to ultimately achieve excellent longitudinal wave blocking and decoupling performance. Utilizing a designable micro-deformation mechanism determined by a specific geometric configuration, a chiral rotationally symmetric curved spiral arm 22 structure is employed. Relying on the rotation-expansion coupling deformation mechanism of the curved spiral arms 22, the chiral metamaterial cell unit can achieve its predetermined mechanical function. More specifically, under hydrostatic pressure, external compression is accommodated through the coordinated bending of multiple curved spiral arms 22 and rotation around the central node 21, using overall structural topological deformation. This deformation mode corresponds to macroscopic volume shrinkage. However, since its energy is mainly consumed in the low-stiffness bending deformation of the spiral arms rather than the high-stiffness compression of the material, the intrinsic eigenvalue corresponding to this deformation mode, i.e., the conformal deformation eigenvalue, is... The curvature and rotational symmetry of the bending helical arm 22 were designed to be extremely low, directly resulting in a significant reduction in the macroscopic equivalent bulk modulus of the unit cell. Precise control of the shear deformation response was achieved by optimizing the curvature and rotational symmetry of the bending helical arm 22. The optimization goal was to break the degeneracy of the shear mode, that is, to allow the unit cell to exhibit different resistance to shear deformation in different directions, thereby enabling targeted enhancement of the shear stiffness in a specific preset direction (or mode). Under the preset shear mode, the deformation mechanism of the bending helical arm 22 changed from "bending-rotation" under compression to "tension" dominance. Since solid materials typically require more energy to resist tension than to resist bending, the isochoric deformation characteristic value corresponding to this specific isochoric deformation mode is... This allowed it to be maintained at a relatively high level; thus, through geometric design, the difference between low volumetric deformation stiffness and high specific shear deformation stiffness was manufactured and amplified in a single material system, ultimately achieving... much smaller The design goal is to create chiral metamaterial unit cells based on the macroscopic technical effects resulting from the microstructural mechanism. When these chiral metamaterial unit cells are periodically arranged to form macroscopic decoupling tiles, the decoupling tiles will possess extremely low equivalent bulk modulus. This makes the decoupling tiles highly sensitive to longitudinal wave excitations that induce volume changes and can provide very low impedance, thereby effectively blocking the transmission of longitudinal waves. The relatively high shear stiffness retained by the decoupling tiles ensures the necessary morphological stability and load-bearing capacity of the structure in the in-plane direction. This anomalous combination of extremely soft longitudinal and relatively stiff transverse mechanical properties enables the decoupling tiles to efficiently solve the technical problem of reconciling the contradiction between low-frequency vibration isolation and structural load-bearing capacity, which is difficult to achieve with traditional homogeneous or simple cavity decoupling materials.

[0031] like Figure 1As shown, in this embodiment, the cross-sectional shape of the chiral metamaterial cell unit is composed of a central node 21 and at least three curved spiral arms 22. One end of the curved spiral arm 22 is connected to the central node 21, and the other end is a free end that extends away from the central node 21. It has a preset, non-zero constant curvature or a gradually changing curvature on the extension path. The multiple curved spiral arms 22 are arranged in rotational symmetry around the central node 21 so that when the chiral metamaterial cell unit is subjected to hydrostatic pressure, the coordinated bending and rotation of the curved spiral arms 22 preferentially stimulates the low-stiffness expansion deformation mode, thereby achieving a chiral metamaterial cell unit with an equivalent bulk modulus that is significantly lower than the equivalent shear modulus. The configuration of "center node 21 - bending free arm" allows the normal load applied to the structure to be evenly distributed to each arm when subjected to axial hydrostatic pressure, due to the rotational symmetry of multiple arms around center node 21. The free end design of the arms means that they are not subject to bending moment constraints at the ends, greatly reducing the constraints on bending deformation of the arms and making them more prone to deflection under pressure. The pre-set, non-zero curvature of the bending arm 22 pre-gives the bending arm 22 a bending geometry, determining its instability mode and deformation path under pressure, so that the bending deformation of the arm can proceed in a coordinated and orderly manner. The combination of the above-mentioned geometric features jointly contributes to the core deformation mechanism described in the technical solution: the coordinated bending and rotation of the bending spiral arms 22. Under hydrostatic pressure, each bending spiral arm 22 does not simply translate independently towards the central node 21, but rather undergoes further bending deformation and synchronous rotation around the central node 21, with its connection point to the central node 21 as the pivot. This coordinated, large-scale geometric deformation can effectively absorb the macroscopic strain caused by external pressure, which attempts to reduce the total volume of the unit cell. Since the volume shrinkage is mainly achieved through the low-energy-cost bending and rotation of the spiral arms, rather than through the high-energy-cost compression of the matrix material itself or the axial compression of the spiral arms, the force or energy (i.e., its equivalent stiffness) required to excite the expansion deformation mode (actually the volume shrinkage mode) is very low, directly resulting in the chiral metamaterial unit cell exhibiting an extremely low equivalent bulk modulus. When resisting shear deformation in certain specific directions, the deformation mechanism of this structure will be fundamentally changed. For example, in certain in-plane shear modes, the load may mainly cause the helical arm to be stretched or compressed, while the stiffness of solid materials against axial deformation is usually much higher than that against bending. The equivalent shear modulus of the chiral metamaterial cell unit can be kept at a level significantly higher than its equivalent bulk modulus. By optimizing the curvature, length and rotational symmetry of the bending helical arm 22, the stiffness ratio between volumetric deformation and shear deformation can be further controlled, thereby accurately achieving the design goal that the equivalent bulk modulus is significantly lower than the equivalent shear modulus. This enables the decoupling tile to efficiently block longitudinal waves (dependent on low bulk modulus) while maintaining the necessary in-plane stiffness (dependent on a certain shear modulus).

[0032] like Figure 1 As shown, in this embodiment, the structure of the chiral metamaterial unit cell is as follows: a square region with a side length of 8mm-15mm is established in a two-dimensional plane as a single unit cell design domain, and the geometric center of the square region is set as the origin of the coordinate system; a central node 21 is set at the geometric center of the unit cell, and the central node 21 is a square region with a side length of 4mm-8mm. The unit cell design domain is a square region with a side length of 8mm to 15mm, which defines the size of the unit cell from a structural scale perspective, and establishes a reasonable correlation with the physical wavelength of the target operating frequency band; in the field of acoustic vibration control, the structural feature size directly affects its effective operating frequency range. The setting of this size range enables the final periodic structure to effectively regulate elastic waves of a specific wavelength (corresponding to the mid-low frequency band), ensuring the physical meaning and engineering practicality of the design; setting the geometric center of the unit cell design domain as the origin of the coordinate system provides a unified and accurate geometric reference for subsequent structural design, parametric modeling and mechanical analysis, which is a prerequisite for realizing the rotational symmetry arrangement of the spiral arms and performing standardized calculations. The central node 21 is a square region with a side length of 4mm to 8mm. This gives the central node 21 a defined physical size and a specific area, transforming it from an ideal geometric point into a solid structural region with load-bearing and connecting functions. This allows the central node 21 to physically stably connect multiple bending arms 22 and provides the necessary torque support and deformation fulcrum for the "cooperative bending and rotation" of the bending arms 22. The proportional relationship between the size range of the central node 21 (4mm-8mm) and the size of the unit cell design domain (8mm-15mm) defines the central node 21. The relative area ratio within the unit cell is beneficial for balancing various properties of the unit cell. A sufficiently large central node 21 helps ensure the connection strength and overall stability of the structure, while an excessively large central node 21 will overly compress the design space of the spiral arm, limiting its bending deformation capability and hindering the achievement of a low bulk modulus. This size limit ensures that the central node 21 has the necessary mechanical function while reserving crucial structural space for the effective design and topology optimization of the bending spiral arm 22. It is an important geometric constraint to ensure that the final unit cell achieves the performance goals of low bulk modulus and high shear stiffness. The limitation of the specific size range of the unit cell design domain and the central node 21 provides a clear, engineering-based dimensional framework and spatial constraints for the design of chiral metamaterial unit cells. This ensures that the unit cell structure has a manufacturable physical scale and matches the target operating frequency band. At the same time, through the reasonable setting of the size of the central node 21, a balance is achieved between structural stability and deformation flexibility, enabling the generation of units with specific mechanical properties (such as...) through topology optimization within this unit cell design domain. The curved helical arm 22 chiral structure provides the necessary and optimized geometric foundation, thereby ensuring the practicality and performance reliability of the final product.

[0033] like Figure 1 As shown, in this embodiment, the curved spiral arm 22 is formed by two circular arcs and connecting line segments. Specifically, a corner point of the square region of the central node 21 is selected as the starting point of the first circular arc, and the offset point of the midpoint of the corresponding boundary of the unit cell design domain is selected as the ending point of the first circular arc. The radius of the first circular arc is 2mm-5mm. The starting and ending points of the first circular arc are respectively... x shaft or y The first and second arcs are translated 1-3 mm along the axis, and the starting and ending points after translation are used as the starting and ending points of the second arc, respectively. The radius of the second arc is the same as that of the first arc. The corresponding endpoints of the first and second arcs are connected by connecting line segments to form a two-dimensional solid cross-section of a single spiral arm. The curved spiral arm 22 is formed by two arcs with specific radii and connecting line segments, ensuring that the spiral arm has a continuous and smooth profile in the cross-section, avoiding stress concentration caused by sharp corners or abrupt changes, thereby enhancing the structural integrity and fatigue life of the spiral arm under repeated deformation, and enabling the decoupling tile to withstand dynamic loads. By specifying the offset points of the corner point of the center node 21 and the midpoint of the boundary of the unit cell design domain as references to locate the start and end points of the first circular arc, and giving a radius range of 2mm to 5mm, the basic skeleton of the bending spiral arm 22 is defined. The bending spiral arm 22 starts from the edge of the center node 21 and extends outward with an arc of moderate curvature (determined by the radius range). This curvature range determines the degree of bending of the bending spiral arm 22, which in turn profoundly affects its mechanical behavior. If the curvature radius is too small (too curved), the spiral arm may become fragile in manufacturing and load-bearing capacity. If the curvature radius is too large (too straight), it will weaken its easy bending and deformation characteristics, which is not conducive to achieving a low bulk modulus. Therefore, this radius range is a parameterized embodiment of the balance between structural flexibility and strength. A second arc is generated by translating the start and end points of the first arc within a specified range (1mm-3mm), and the corresponding endpoints are connected by line segments, thus constructing a solid spiral arm with a finite width and a curved strip shape. The translation amount (i.e., the width of the curved spiral arm 22) and the radius of the arc together determine the shape of the spiral arm's cross-section and its bending moment of inertia. The curved spiral arm 22 generated by this construction method has its inner and outer contours defined by two parallel curves (arcs), ensuring that the curved spiral arm 22 can be uniformly stretched into a three-dimensional solid in the thickness direction (perpendicular to the two-dimensional plane). At the same time, it also allows the entire cross-section to participate in bending deformation more uniformly when subjected to in-plane compression, rather than being supported by a single line. Compared with simple line segments or variable cross-section beams, this uniformly wide curved strip structure provides the necessary in-plane bending compliance to achieve a low bulk modulus, while also providing a certain in-plane tensile / compressive stiffness through its cross-sectional area, which helps to maintain a high eigenvalue under specific shear modes. The abstract curved helical arm 22 with curvature is transformed into a parameterized, precisely manufacturable solid geometric model with controllable mechanical behavior. By limiting geometric parameters such as the radius of the arc and the amount of translation, the curved helical arm 22 is made easy to bend in order to reduce the shape-preserving deformation eigenvalue. To maintain a certain tensile stiffness in the bending helical arm 22 in order to maintain a high isochoric deformation characteristic value This provides a specific design trade-off; the resulting curved helical arm 22 is the final realization of the unit cell. much smaller This goal, in turn, provides a reliable and optimized physical basis for achieving decoupling tiles with low equivalent bulk modulus and high decoupling performance.

[0034] like Figure 1As shown, in this embodiment, a single curved spiral arm 22 is rotated around the geometric center of the cell design domain by 90°, 180° and 270° respectively to obtain the remaining three curved spiral arms 22. Thus, the four curved spiral arms 22 are distributed circumferentially around the central node 21 to form a two-dimensional cross-sectional structure of the chiral metamaterial cell unit. Each curved spiral arm 22 has a consistent deflection direction, so that the chiral metamaterial cell unit exhibits obvious co-rotation characteristics as a whole. This co-rotation characteristic geometric configuration defines the distribution boundary, spiral arm curvature trend and internal pore region morphology of the chiral metamaterial in the cell design domain, thereby ensuring that the obtained chiral metamaterial cell unit structure has stable and repeatable geometric characteristics. The remaining three curved spiral arms 22 were generated using a rotational replication method. This involved rotating each pre-designed curved spiral arm 22 around the cell center by 90°, 180°, and 270° respectively, ensuring that all four curved spiral arms 22 were geometrically identical. This consistency is fundamental to functionality, ensuring that under hydrostatic pressure, the load shared, deformation experienced, and stiffness contribution provided by each spiral arm are strictly symmetrical and equal. This symmetry between force and deformation is a prerequisite for activating the "cooperative bending and rotation" low-stiffness volumetric deformation mode. If the curved spiral arms 22 are geometrically inconsistent, their deformation under compression will be asynchronous, potentially leading to localized stress concentration or distortion. This would not only fail to efficiently achieve a low bulk modulus but could also compromise structural stability. By rotating and replicating the spiral arms 22 and specifying a consistent deflection direction, the final chiral metamaterial cell unit is forced to exhibit a clear and consistent chiral characteristic, i.e., a unidirectional rotational characteristic. The deflection direction refers to the bending orientation of the spiral arm; for example, the convex surfaces of all spiral arms should face clockwise or counterclockwise. This chiral configuration with co-rotation is the geometric root of the tension-torsion coupling effect. When compressed axially, all the co-rotating bending arms 22 tend to rotate in the same direction, thus coupling the axial compression into a total torque around the central node 21. The directional, cooperative deformation mechanism efficiently converts macroscopic volumetric strain into local rotational and shear strain, thereby achieving an extremely low equivalent bulk modulus. Conversely, if the bending directions of the bending arms 22 alternate (exhibiting centrosymmetry rather than chirality), this cooperative rotational effect will be canceled out.The unidirectional rotational characteristic defines the distribution boundaries, spiral arm curvature trends, and internal pore region morphology of chiral metamaterials within the cellular design domain. By following this construction rule, the spatial distribution of material within the cell, the bending paths of the spiral arms, and the resulting pore shapes are uniquely determined, forming a highly ordered, non-random, and asymmetric periodic pattern. This determinism brings stable and repeatable geometric features, ensuring predictability and repeatability of performance. Any chiral metamaterial cellular unit fabricated based on this rule has the exact same mechanical response, ensuring the performance consistency of the decoupled tiles composed of chiral metamaterial cellular units. It optimizes the load-bearing and deformation efficiency of the structure. The ordered pore distribution and the trend of the curved spiral arms allow the structure to achieve a low bulk modulus while making the most efficient use of material, forming a clear force flow path, thereby maintaining high shear stiffness in a specific direction. It provides a clear geometric standard for large-scale engineering manufacturing and quality control.

[0035] like Figure 1 and Figure 2 As shown, in this embodiment, periodically arranged chiral metamaterial unit cells form periodically arranged chiral structural cavities. Multiple chiral metamaterial unit cells with identical geometric and mechanical properties are repeatedly arranged in a two-dimensional plane according to a strict lattice order (such as a square lattice); this arrangement encapsulates the unique mechanical properties of each individual chiral metamaterial unit cell (i.e., determined by...). The guaranteed extremely low equivalent bulk modulus is linearly superimposed and extended on a macroscopic scale; the periodic array of a single chiral metamaterial unit cell constitutes a macroscopic functional set with uniform and consistent performance, enabling the entire decoupling tile layer to make a uniform, low-stiffness mechanical response to external excitation (especially normal excitation) at any position and in any direction, thereby ensuring the spatial uniformity and reliability of vibration suppression and sound wave blocking effects, and avoiding performance fluctuations or local failures caused by structural inhomogeneity. The chiral structural cavity formed by the periodic arrangement is the medium for realizing the function of the decoupling tile. It is a complex network of connected or quasi-connected pores with specific chiral geometry, enclosed by the bent spiral arms 22 in each chiral metamaterial unit cell; this periodic chiral structural cavity provides the physical space for the structure to achieve large volume deformation, so that the spiral arms have sufficient deformation margin when rotated under pressure, which is a geometrically necessary condition for achieving low bulk modulus; the periodically arranged chiral structural cavities constitute a periodic scattering array of sound waves and elastic waves propagating inside the material; when elastic waves When longitudinal waves (especially longitudinal waves) are introduced, complex scattering, interference, and mode conversion (longitudinal wave to shear wave) occur at the interface of each chiral cavity. This periodic scattering effect can further attenuate the energy of the wave and broaden the effective isolation frequency band. The coordinated deformation of all chiral metamaterial cell units means that these chiral structural cavities will exhibit coordinated and periodic volume pulsations and shape changes under dynamic loads. This collective and ordered deformation mode can more effectively convert macroscopic wave energy into microscopic strain energy of the material and dissipate it through damping. Its efficiency is much higher than that of disordered or isolated cavities. By periodically arranging chiral metamaterial cell units to form periodic chiral cavity structures, a highly efficient, uniform, and reliable scale transition from superior microscopic performance to outstanding macroscopic functionality is achieved. This not only ensures the uniformity and predictability of the overall mechanical properties of the decoupling tile, but also enables the final decoupling tile to achieve more effective and stable suppression of structural vibration and radiated acoustic power over a wide frequency range, especially in the mid-to-low frequency band, through the synergistic deformation and wave scattering effect of the periodic chiral cavity array. This solves the problem of insufficient broadband performance of traditional decoupling structures.

[0036] like Figure 2 and Figure 3As shown, the acoustic vibration control structure of this embodiment includes the aforementioned chiral metastructure decoupling tiles, and the chiral metastructure decoupling tile array is arranged to form a chiral metastructure decoupling tile layer 2; it includes, from bottom to top, the following components: a base structure 1, used to withstand external excitation force; a chiral metastructure decoupling tile layer 2, laid on the surface of the base structure 1, with chiral metastructure decoupling tiles arranged in an array inside; and a fluid medium layer 3, located on the side of the chiral metastructure decoupling tile layer 2 away from the base structure 1, forming an acoustic-structural boundary between the fluid medium layer 3 and the chiral metastructure decoupling tile layer 2; when the base structure 1 is subjected to point force excitation to generate vibration and radiate sound waves outward, the chiral metastructure decoupling tile layer 2 plays a role in vibration isolation and vibration suppression. The chiral structure cavity of the chiral metastructure decoupling tile layer 2 will generate local rotation and waveform transformation when subjected to force, significantly increasing the energy loss of vibration in the transmission process, thereby reducing the radiated sound power transmitted to the fluid medium layer 3. The present invention discloses an acoustic vibration control structure, which constructs a sandwich-like laminated system consisting of a "base structure 1, a chiral meta-decoupling tile layer 2, and a fluid medium layer 3". The chiral meta-decoupling tile is the core functional layer, which is laid between the base structure 1 (vibration source) and the fluid medium layer 3 (acoustic radiation medium). The base structure 1 is used to withstand external excitation force and defines the boundary conditions of vibration input. The acoustic-structural boundary is formed between the fluid medium layer 3 and the chiral meta-decoupling tile layer 2, which clarifies the coupling interface at which vibration energy is ultimately converted into acoustic radiation. This clear hierarchical relationship allows the analysis and evaluation of decoupling performance to be carried out in a complete "excitation-transmission-radiation" physical model, thereby enabling a comprehensive and objective evaluation of the actual effectiveness of the chiral meta-decoupling tile. When the base structure 1 is excited by a point force and vibrates, radiating sound waves outward, the chiral metastructure decoupling tile 2 plays a role in vibration isolation and vibration suppression. Its working mode is active vibration isolation. Vibration isolation is achieved by using the extremely low equivalent bulk modulus of the chiral metastructure decoupling tile 2 to introduce a very low stiffness elastic buffer layer between the base structure 1 and the upper structure, thereby significantly reducing the vibration energy transmitted from the base structure 1 to the fluid medium layer 3. In particular, it has a significant attenuation effect on vibrations that are excited above the resonant frequency of the "spring-mass" system. Vibration suppression is achieved through the mechanism that the chiral structure cavity will generate local rotation and waveform transformation when subjected to force. When the vibration (especially in the form of longitudinal waves) is transmitted to the interior of the decoupling tile, the periodic chiral cavity array forces the vibration wave to undergo a forced waveform transformation from longitudinal wave to shear wave during propagation. Because the matrix material constituting the decoupling layer (such as a high-damping polymer) has high internal friction for shear deformation, this waveform conversion mechanism can efficiently convert the difficult-to-dissipate longitudinal wave energy into shear strain energy that is easily dissipated in the form of heat within the material, thereby achieving active consumption in the transmission path of vibration energy.The dual mechanisms of vibration isolation (reducing transmission) and vibration suppression (energy consumption) work synergistically in the acoustic vibration control structure, significantly increasing energy loss during vibration transmission and thus reducing the radiated acoustic power transmitted to the fluid medium layer 3. The significant blocking and consumption of energy in the transmission path directly leads to a reduction in the acoustic energy ultimately coupled into the fluid and radiated outwards, manifested as a significant reduction in radiated acoustic power. This solves the technical problem of insufficient attenuation of radiated acoustic power in traditional decoupling structures. The acoustic vibration control structure of this invention, by integrating the chiral meta-decoupling tile layer 2 between the excitation source and the acoustic radiation medium, constructs a complete vibration and noise control system. It fully utilizes the low equivalent bulk modulus characteristics and waveform conversion mechanism of the chiral meta-decoupling tile, synergistically achieving the dual effects of blocking transmission and consuming energy at the system level. This effectively suppresses the conversion of vibration generated from the base structure 1 into acoustic radiation in the fluid medium, ultimately achieving the system-level engineering goal of significantly reducing radiated noise power. This verifies the effectiveness and application value of the chiral meta-decoupling tile in solving practical engineering acoustic vibration problems.

[0037] In practice, a chiral metamaterial decoupling tile and acoustic vibration control structure are provided, belonging to the field of underwater acoustics and vibration noise control technology. Addressing the limitation of traditional cylindrical cavity decoupling tiles in broadband (especially mid-to-low frequency) acoustic radiation control capabilities, this invention proposes a chiral metamaterial decoupling tile and acoustic vibration control structure, comprising a base structure 1, a chiral metamaterial decoupling tile layer 2, and a fluid medium layer 3. The chiral metamaterial decoupling tile layer 2 contains periodically arranged chiral metamaterial unit cells. The cross-section of each chiral metamaterial unit cell consists of a central node 21 and outwardly extending curved spiral arms 22. When subjected to external excitation forces, the chiral metamaterial unit cell, with its unique tension-torsion coupling and local resonance mechanism, can more efficiently dissipate vibrational energy. Compared with traditional homogeneous or simple cavity decoupling layers, this invention can significantly enhance vibration transmission loss and greatly reduce radiated sound power in a wide frequency band of 200Hz-1000Hz, and has superior low-frequency broadband noise reduction performance and extremely high structural design freedom.

[0038] Compared with the prior art, the beneficial effects of the chiral metastructure decoupling tile and acoustic vibration control structure of the present invention are as follows: 1. Superior Broadband Noise Reduction Performance: The unique deformation mechanism of the chiral structure enables more efficient dissipation of vibrational energy. Under the same excitation conditions, the radiated acoustic power of the chiral metastructure decoupling tile of this invention is significantly lower than that of the uncoated bare plate, and its noise reduction effect is significantly better than that of traditional cylindrical cavity decoupling tiles in the 200Hz to 1000Hz frequency band. Specific simulation data show that the radiated acoustic power drops to about 55dB at 300Hz and further decreases to about 44dB at 1000Hz, while the traditional cylindrical decoupling tile achieves approximately 60dB and 54dB at the same frequencies, respectively.

[0039] 2. A dual mechanism of vibration suppression and isolation based on intrinsic mode modulation: The unit cell of this invention is topologically optimized, and the conformal deformation eigenvalue is much smaller than the isochoric deformation eigenvalue. The properties of the structure give it an extremely low equivalent bulk modulus, enabling effective suppression of matrix vibration and strong blocking of longitudinal wave transmission, resulting in a significant improvement in overall decoupling performance.

[0040] Example 1: After rotating 90 degrees around the central node 21, the curved helical arm 22 can completely coincide with the original structure, but it does not possess mirror symmetry. Specifically, a square region with a side length of 11 mm is established in a two-dimensional plane as the cell design domain of a single chiral metamaterial unit cell, and the geometric center of the square region is set as the origin (0, 0). A central node 21 is set at the geometric center of the chiral metamaterial unit cell, preferably a square region with a side length of 6 mm. The curved helical arm 22 can be formed by enclosing two circular arcs and connecting line segments. In specific construction, the corner point (3, 3) of the square region of the central node 21 is selected as the starting point of the first circular arc, and the point (1, 5, 5) offset to one side by 1 mm from the midpoint of the upper boundary of the cell design domain is selected as the ending point of the first circular arc, and the radius of the first circular arc is 3 mm. The starting and ending points of the first arc are translated 2 mm along the negative x-axis to obtain points (1, 3) and (-1, 5.5), respectively. These two points are then used as the starting and ending points of the second arc, which also has a radius of 3 mm. Subsequently, the corresponding endpoints of the first and second arcs are connected by line segments to form a two-dimensional solid cross-section of a single curved spiral arm 22. After forming the single curved spiral arm 22, it is rotated 90°, 180°, and 270° around the geometric center of the cell's design domain to obtain the remaining three curved spiral arms 22. Thus, the four curved spiral arms 22 are circumferentially distributed around the central node, forming a complete two-dimensional cross-sectional structure of the chiral metamaterial unit. Each curved spiral arm 22 formed by the above construction method has a consistent deflection direction, causing the unit cell to exhibit a clear unidirectional rotation characteristic overall. This geometric configuration defines the distribution boundary of the material in the unit cell design domain, the curvature trend of the curved spiral arm 22, and the morphology of the internal pore region, thus ensuring that the resulting unit cell structure has stable and repeatable geometric features.

[0041] The chiral structure formed in the above manner can coincide with itself when rotated 90° around the center of the unit cell, but cannot coincide with itself after being mirrored along any straight line. Therefore, this structure has definite chiral characteristics. Based on the unit cell obtained according to the above geometric construction rules, the expected mechanical response characteristics can also be achieved while meeting the preset porosity requirements. Structural mechanism and effects: Its core design mechanism lies in breaking the mirror symmetry of traditional decoupled cavities (such as cylindrical cavities) and introducing geometric chirality and specific bending morphology into the structure. The bending spiral arms 22 with specific curvature play a core role as a "mechanical mode converter" in the entire chiral decoupling tile. When the structure is subjected to longitudinal excitation force along the direction of sound wave propagation, since each bending spiral arm 22 has the same bending orientation and cannot provide rigid resistance, the longitudinal compressive strain is forcibly converted into local shear strain. At this time, the bending spiral arms 22 with the same rotation direction produce coordinated deformation, transforming the external longitudinal compressive load into a tangential moment driving the rotation of the central node 21. This tension-torsion coupling mechanism based on geometric morphology ensures that the structure no longer generates pure volumetric rigid resistance under compression, thus successfully achieving a conformal deformation characteristic value much smaller than one of the isochoric deformation characteristic values ​​without changing the intrinsic properties of the matrix material. This significantly reduced the equivalent bulk modulus of the chiral metastructure decoupled tile layer 2.

[0042] Dynamic working principle (waveform conversion and energy dissipation): When the base structure 1 vibrates under external excitation and radiates energy outward in the form of longitudinal waves, the chiral metastructure decoupling layer 2 plays a role in vibration suppression and decoupling. Specifically, due to the non-centrosymmetric curved spiral arm 22 structure of the chiral unit, the structure will produce a significant tensile-torsional coupling effect when subjected to longitudinal stress perpendicular to the surface. This effect forces the central node 21 of the chiral unit to rotate locally, resulting in not only axial compression but also strong shear deformation of the structure.

[0043] During this process, a waveform transformation occurs from longitudinal wave to transverse wave (shear wave): the incident longitudinal wave energy is largely converted into localized rotational kinetic energy and shear strain energy. Because the matrix of the chiral metastructure decoupling layer 2 is made of a highly damped polymer material, it exhibits an extremely high internal dissipation rate for shear deformation. Therefore, this waveform transformation mechanism precisely converts the originally highly penetrating and difficult-to-attenuate longitudinal vibration into shear deformation, which is easily dissipated as heat energy by the damping material. This significantly increases the energy loss during vibration transmission and ultimately significantly reduces the radiated acoustic power transmitted to the fluid medium layer 3.

[0044] Example 2: Detailed design principles and derivation process of unit cells.

[0045] The design of the chiral metamaterial unit cell in this invention breaks through the stiffness limitations of traditional decoupling materials. The specific mechanical derivation and structural design process are as follows: (1) Mechanical mechanism analysis and design target positioning: The equipment shell vibrates under internal mechanical excitation, radiating noise underwater, a typical acoustic-structure interaction problem. The shell-decoupling tile-water area can be considered an active vibration isolation system, where the decoupling tile acts as a "spring-damper". According to the laws of vibration transmission, to achieve better low-frequency noise reduction, the natural frequency of the entire vibration isolation system must be reduced, requiring the decoupling tile to have the lowest possible equivalent stiffness. Further analysis from the perspective of continuum mechanics reveals that under vertical excitation, vibration is primarily transmitted as longitudinal waves. The bulk modulus of the material is the key parameter determining low-frequency noise reduction performance, while shear modulus and density have relatively little impact. Therefore, finding or designing material structures with extremely low bulk modulus is the core design objective.

[0046] (2) Intrinsic mode regulation theory: In conventional isotropic homogeneous materials, the conformal deformation characteristic value ( ) is usually greater than the isochoric deformation characteristic value ( To overcome the limitations of this natural material, this invention proposes to achieve a "form-preserving deformation characteristic value that is much smaller than the isochoric deformation characteristic value" through structural design. or The idea of ​​").

[0047] (3) Cell design and mechanical deduction based on intrinsic mode modulation: In continuum mechanics, the intrinsic modes of a material can be decomposed into a conformal deformation mode (where volume or area changes while shape remains constant, and its corresponding eigenvalues ​​are...). Reflects the material's volumetric stiffness) and two independent isochoric deformation modes (shear deformation occurring while the volume or area remains constant, with corresponding eigenvalues). and It reflects the shear stiffness of the material. The magnitude of the eigenvalue directly characterizes the material's ability to resist deformation in the corresponding mode.

[0048] For traditional isotropic homogeneous materials (such as ordinary rubber coatings), their two isochoric deformation eigenvalues ​​are equal ( Furthermore, the conformal deformation eigenvalue is often greater than the isochoric deformation eigenvalue. This means that traditional materials are extremely difficult to compress in volume, exhibiting a very high equivalent bulk modulus when facing underwater longitudinal waves (which mainly cause volume compression), essentially acting as a "stiff spring," resulting in poor decoupling and noise reduction performance in the low-frequency range. While ordinary cylindrical cavity decoupling tiles introduce porosity to reduce stiffness (…),… Slightly smaller However, it still cannot completely change its deformation mode, and its ability to reduce noise at extremely low frequencies remains limited.

[0049] This invention utilizes topology optimization to design a chiral metastructure consisting of a central node 21 and a curved spiral arm 22. This structure breaks through the deformation limitations of traditional materials, enabling precise control of intrinsic modes. First, the eigenvalues ​​corresponding to the two isochoric deformations are no longer equal. This chiral structure exhibits macroscopic isotropy, but in terms of microscopic deformation mechanism, it produces different resistance distributions for two different shear deformation modes.

[0050] Second, the conformal deformation eigenvalue was made much smaller than one of the isochoric deformation eigenvalues. The introduction of this feature yielded drastically different vibration isolation results. On the one hand, " much smaller This means that the structure is highly susceptible to conformal shrinkage when subjected to longitudinal excitation forces, exhibiting characteristics of an "extremely soft spring"; on the other hand, larger... This value ensures that the structure still has sufficient load-bearing capacity and morphological stability when under pressure.

[0051] because and There are significant numerical differences between them. When subjected to longitudinal excitation by external sound waves, the structure no longer generates pure volumetric resistance. Instead, it transforms compressive deformation into localized rotational and shear deformation (i.e., tension-torsion coupling effect) through the bending helical arm 22. This special energy dissipation and deformation mechanism enables the structure to achieve an extremely low equivalent bulk modulus on a macroscopic scale without requiring the material itself to be absolutely soft.

[0052] Final result: The extremely low equivalent bulk modulus significantly reduces the natural frequency of the "shell-decoupling tile-water area" active vibration isolation system, effectively cutting off the transmission path of longitudinal waves. Compared to traditional cylindrical decoupling tiles (initial noise reduction frequency 440Hz), the starting operating frequency of the chiral metastructure decoupling tile of this invention is significantly reduced to around 120Hz, achieving significant attenuation of radiated acoustic power in a wide frequency band of 200Hz-1000Hz.

[0053] Example 3: Structural parameters of chiral metamaterial units.

[0054] To achieve optimal acoustic vibration control, this embodiment... Figure 1 The core geometric parameters of the chiral metamaterial unit cell shown were designed, and the specific parameters are as follows: Overall thickness of chiral metastructure decoupling tile layer 2: 30mm.

[0055] Chiral metamaterial cell unit size: determines the arrangement density of chiral structures inside the decoupled tile, set to 11 mm.

[0056] Center node 21 dimensions: Center node 21 is the core hub connecting the chiral metamaterial cell unit to each curved spiral arm 22, and its characteristic dimension side length is set to 6mm.

[0057] Thickness of bending swivel arm 22: The thickness of bending swivel arm 22 determines the equivalent stiffness of the chiral structure and the strength of the tension-torsion coupling effect. The average thickness is set to 2mm.

[0058] Porosity: The porosity, determined by the above geometric dimensions, is set at 46%.

[0059] Example 4: Simulation verification and acoustic-vibration characteristic analysis.

[0060] To verify the superiority of the chiral metastructure decoupling tile of this invention compared with the traditional structure, numerical verification was performed using finite element simulation software.

[0061] In the finite element model, to control for variables, the same material parameter settings were used for all comparison groups. The specific material parameters are as follows: Material parameters of base structure 1: density is 7890kg / m³, Young's modulus is 210GPa, Poisson's ratio is 0.273, and thickness is set to 10mm.

[0062] Material parameters for chiral metastructure decoupling layer 2: The matrix is ​​made of a high-damping polymer material. Considering the complexity of the underwater acoustic and vibration environment, the material parameters take into account the physical properties that fluctuate with frequency. Its Young's modulus E increases slightly with increasing frequency f, satisfying the fitting relationship: (Unit: MPa); its loss factor It is described using a third-order polynomial: ;in, The excitation frequency is expressed in Hz. These are the material characteristic coefficients. In the specific simulation, the values ​​of the above coefficients are respectively: , , , The density of the material is set at 1160 kg / m³, and the Poisson's ratio is 0.498.

[0063] External excitation conditions: A simple harmonic point force of 1N is applied to the center of the base structure 1.

[0064] Fluid medium layer (3): set to a water environment with a density of 1000 kg / m³ and a sound velocity of 1500 m / s.

[0065] Based on the above structural parameters (Example 2) and material parameters, the bare plate without decoupling tiles and the plate with traditional cylindrical decoupling tiles (structure as shown) were respectively tested. Figure 4As shown in the figure, simulation calculations were performed on the structure with the chiral metastructure decoupling tile of the present invention, and the resulting radiated acoustic power comparison curve is shown in the figure. Figure 4 As shown.

[0066] like Figure 4 As shown, within the 0-1000Hz frequency band: The bare board (solid line) without decoupling tiles has the highest radiated sound power, which is stable at 65dB.

[0067] After laying traditional cylindrical decoupling tiles (thick dashed line), they begin to play a noise reduction role in the frequency band above 150Hz, and the radiated sound power drops to 54dB at 1000Hz.

[0068] After the chiral metastructure decoupling tile (dotted line) of the present invention is laid, its radiated acoustic power drops rapidly after 150 Hz, drops to 55 dB at 300 Hz, and drops further to 44 dB at 1000 Hz.

[0069] Simulation data fully demonstrate that, under the same thickness, material, and excitation conditions, the chiral metastructure decoupling tile proposed in this invention has extremely excellent acoustic and vibration decoupling performance in a wide frequency range (especially in the mid-low frequency band of 200Hz-1000Hz), and its noise reduction effect is significantly superior to that of traditional cylindrical structures.

[0070] Matters not covered in this invention are common knowledge.

[0071] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A design method for chiral metastructure decoupling tiles, characterized in that, Includes the following steps: S100. With the design goal of reducing the equivalent bulk modulus of the decoupling tile and suppressing the transmission of vibration longitudinal waves, a mechanical model of the decoupling tile is established. The acoustic performance of the decoupling tile is determined by multiple equivalent mechanical parameters, including the equivalent bulk modulus, the equivalent shear modulus, and the equivalent density. S200. Based on the intrinsic mode modulation theory, the design objective of the chiral metamaterial unit cell of the chiral metamaterial decoupling tile is set. The design objective is to make the conformal deformation eigenvalue of the chiral metamaterial unit cell equal to the form-preserving deformation eigenvalue. Less than any isochoric deformation eigenvalue of the chiral metamaterial unit cell ; S300: Based on the design goals set in step S200, topology optimization is performed on the initial unit cell model to generate an optimized unit cell structure with chiral characteristics. Topology optimization uses conformal deformation eigenvalues. Minimization is the optimization objective, and the material volume fraction of the chiral metamaterial unit cell is used as the constraint. The optimal unit cell configuration is obtained through iterative calculation. The cross-sectional shape of the optimized unit cell structure includes a central node and multiple curved spiral arms. The curved spiral arms extend outward from the central node and have curvature, and are arranged in rotational symmetry around the central node. S400. Perform homogenization calculations on the optimized cell structure obtained in step S300 and extract the equivalent bulk modulus. With equivalent shear modulus And verify whether it satisfies Performance criteria; S500: The optimized cell structure that meets the performance criteria of step S400 is periodically arranged in a two-dimensional plane to generate a cell array, thereby forming the overall structure of the chiral meta-decoupling tile.

2. A chiral metastructure decoupling tile, characterized in that, The chiral metamaterial decoupling tile, designed and fabricated using the design method described in claim 1, comprises periodically arranged chiral metamaterial unit cells. The design of the chiral metamaterial unit cells is based on the intrinsic mode control theory. Topological optimization is performed on the cell morphology of the chiral metamaterial unit cells to ensure that the eigenvalues ​​corresponding to the two isochoric deformations in the intrinsic modes of the cell morphology are unequal, and to ensure that the conformal deformation eigenvalues ​​are... Much smaller than one of the isochoric deformation eigenvalues ,Right now This reduces the equivalent bulk modulus of the decoupling tile, effectively suppressing matrix vibration and strongly blocking longitudinal wave transmission, thereby significantly improving the overall decoupling performance.

3. The chiral metastructure decoupling tile according to claim 2, characterized in that, The structure of the unit cell of a chiral metamaterial is as follows: Under standard homogenization calculation conditions, the conformal deformation eigenvalues ​​of chiral metamaterial unit cells With one of the isochoric deformation eigenvalues The ratio between them satisfies ,in and The stiffness matrix of the chiral metamaterial unit cell under periodic boundary conditions is obtained by eigenmode decomposition. Corresponding to a unique conformal deformation mode that causes a change in unit cell volume, It is the mode with the largest eigenvalue among all isochoric deformation modes that do not cause volume change.

4. The chiral metastructure decoupling tile according to claim 3, characterized in that, To achieve extremely low equivalent bulk modulus in single-phase solid materials while maintaining a certain shear stiffness, a chiral rotationally symmetric curved spiral arm structure is used. Through the rotation-expansion coupled deformation mechanism of the curved spiral arms, the chiral metamaterial cell unit can achieve volume shrinkage under hydrostatic pressure through the bending and rotation of the curved spiral arms, corresponding to the conformal deformation characteristic value of the low expansion mode. In the preset shear mode, the bending arm mainly undergoes tensile deformation, requiring more energy and corresponding to a higher isochoric deformation characteristic value of the shear feature. ; By optimizing the curvature and rotational symmetry of the curved spiral arm, the degeneracy of the shearing mode is broken, thereby achieving... The goal is to ultimately achieve excellent longitudinal wave blocking and decoupling performance.

5. The chiral metastructure decoupling tile according to claim 4, characterized in that, The cross-sectional shape of the chiral metamaterial unit cell consists of a central node and at least three curved spiral arms. One end of the curved spiral arm is connected to the central node, and the other end is a free end that extends away from the central node. The curved spiral arm has a preset, non-zero constant curvature or a gradual curvature along the extension path. Multiple curved spiral arms are arranged in a rotationally symmetrical manner around the central node. When the chiral metamaterial cell unit is subjected to hydrostatic pressure, the coordinated bending and rotation of the curved spiral arms preferentially induces a low-stiffness expansion deformation mode, thereby achieving a chiral metamaterial cell unit with an equivalent bulk modulus that is significantly lower than the equivalent shear modulus.

6. The chiral metastructure decoupling tile according to claim 5, characterized in that, The specific structure of the unit cell of chiral metamaterials is as follows: A square region with a side length of 8mm-15mm is established in a two-dimensional plane as the design domain of a single unit cell, and the geometric center of the square region is set as the origin of the coordinate system; a central node is set at the geometric center of the unit cell, and the central node is a square region with a side length of 4mm-8mm.

7. The chiral metastructure decoupling tile according to claim 6, characterized in that, The curved spiral arm is formed by two circular arcs and a connecting line segment; In the specific construction, a corner point of the square region of the central node is selected as the starting point of the first arc, and the offset point of the midpoint of the boundary of the unit cell design domain is selected as the ending point of the first arc. The radius of the first arc is 2mm-5mm. The starting and ending points of the first arc are respectively along... x shaft or y The axis is translated by 1mm-3mm, and the starting point and ending point after translation are used as the starting point and ending point of the second arc, respectively. The radius of the second arc is the same as that of the first arc. The corresponding endpoints of the first and second circular arcs are connected by connecting line segments to form a two-dimensional solid cross-section of a single spiral arm.

8. The chiral metastructure decoupling tile according to claim 7, characterized in that, A single curved spiral arm is rotated and replicated by rotating it by 90°, 180° and 270° respectively, with the geometric center of the unit cell design domain as the rotation center, to obtain the other three curved spiral arms; Thus, the four curved spiral arms are distributed circumferentially around the central node, forming a two-dimensional cross-sectional structure of the chiral metamaterial unit cell; Each curved spiral arm has a consistent deflection direction, which makes the chiral metamaterial unit cell exhibit obvious co-rotation characteristics as a whole. This co-rotation characteristic geometry defines the distribution boundary, spiral arm curvature trend and internal pore region morphology of the chiral metamaterial in the unit cell design domain, thereby ensuring that the obtained chiral metamaterial unit cell structure has stable and repeatable geometric characteristics.

9. The chiral metastructure decoupling tile according to any one of claims 2 to 8, characterized in that, Periodically arranged chiral metamaterial cell units form periodically arranged chiral structural cavities.

10. A sound and vibration control structure, characterized in that, Includes the chiral metastructure decoupling tile as described in any one of claims 2 to 9; Including those arranged from bottom to top: The base structure is used to withstand external vibration forces; Chiral metamorphic decoupling tile layer is laid on the surface of the base structure, with chiral metamorphic decoupling tiles arranged in an array inside; The fluid medium layer is located on the side of the chiral meta-decoupling tile layer away from the base structure, and an acoustic-structural boundary is formed between the fluid medium layer and the chiral meta-decoupling tile layer; When the base structure is subjected to point force excitation to generate vibration and radiate sound waves outward, the chiral metastructure decoupling tile layer plays a role in vibration isolation and vibration suppression. When the chiral structure cavity of the chiral metastructure decoupling tile layer is subjected to force, it will generate local rotation and waveform transformation, which significantly increases the energy loss of vibration in the transmission process, thereby reducing the radiated sound power transmitted to the fluid medium layer.

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