Snowflake-shaped acoustic metamaterial

Abstract

The snowflake-shaped acoustic metamaterial comprises a plurality of snowflake-shaped cells which are periodically arranged in a two-dimensional plane, a cavity is designed in the center area of each snowflake-shaped cell, a plurality of identical solid connecting pieces are annularly arrayed on the periphery of each cavity, and snowflake-shaped structural bodies are connected between the adjacent solid connecting pieces. On the basis of a snowflake structure, an acoustic metamaterial structure with band gap characteristics is designed, the band gap frequency band is controlled within the range of 200Hz-5000Hz through the unique spatial configuration design of the structure, and the innovative structural design can flexibly adapt to vibration control requirements of different engineering scenes; a new technical approach is provided for solving the broadband vibration problem in practical engineering; through a unique geometric configuration and efficient space hollowing treatment, on the premise that the same size and thickness are kept, not only is the light weight of the structure and the economization of materials achieved, but also the overall stability of the structure is ensured.

Description

Technical Field

[0001] The present invention relates to an acoustic metamaterial, in particular to a snowflake-shaped acoustic metamaterial. Background Art

[0002] In high-end equipment fields like aerospace, marine vehicles, and other sectors, vibration and noise control remains a critical technical challenge that needs to be addressed. Traditional vibration and noise reduction technologies, primarily based on passive control principles, use mass blocks, damping layers, and isolators to block vibration propagation paths. While widely used in engineering practice, these technologies struggle to balance frequency control with lightweighting requirements, and they also suffer from inherent limitations such as a narrow effective frequency band and poor environmental adaptability.

[0003] Acoustic metamaterials, a recent development, offer a new approach to breaking through the bottlenecks of conventional technologies by enabling the artificial manipulation of elastic waves through ingeniously designed cellular structures. Their unique bandgap properties effectively suppress vibration propagation within a specific frequency range, demonstrating significant advantages such as excellent vibration damping performance and a compact and lightweight structure. This has become a new research direction in the field of vibration and noise control.

[0004] In recent years, acoustic metamaterials have shown great application potential in the field of vibration and noise reduction due to their unique bandgap characteristics. With the deepening of research, various types of innovative acoustic metamaterials have continued to emerge and have been successfully applied in key fields such as aerospace, civil engineering, and transportation. In response to the vibration and noise problems unique to urban rail transit, the local resonant acoustic metamaterial structure developed by Cai Yiping's team (CN119600982A) effectively suppressed the propagation of vibration noise in a specific frequency band; Gan Hu et al. (CN120126436A) designed a type of plate-cavity coupled resonant acoustic metamaterial containing an elastic layer, breaking through the limitations of traditional structures in frequency selection and significantly improving the noise control effect in the infrasonic frequency band. However, the existing technology generally adopts a multi-part assembly structure, which exposes obvious limitations in practical applications: on the one hand, the cumulative assembly error will cause the bandgap frequency to shift, affecting the vibration reduction effect; on the other hand, the complex assembly process increases the manufacturing cost. To address these issues, it is necessary to propose a type of integrated acoustic metamaterial structure to eliminate assembly errors, ensure precise control of bandgap characteristics, simplify the production process, and provide a new technical path for the engineering application of acoustic metamaterials. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to propose a snowflake-shaped acoustic metamaterial. The acoustic metamaterial cell adopts a hollow geometric configuration design, which can achieve lightweight while producing bandgap characteristics in a wide frequency range.

[0006] Technical solution: The present invention includes a number of snowflake-shaped cells periodically arranged in a two-dimensional plane. The central area of ​​a single snowflake-shaped cell is designed with a cavity, and a circular array around the cavity has multiple identical solid connectors, and adjacent solid connectors are connected by snowflake-shaped structures.

[0007] The snowflake-shaped structure is parameterized using cubic Bezier curves to achieve a continuous and smooth transition between the inner and outer contours.

[0008] The snowflake-shaped structure adopts a hollow structure, which not only achieves lightweight structure and economical material while maintaining the same volume and thickness, but also ensures the overall stability of the structure.

[0009] Each geometric mutation position of the snowflake configuration cell is rounded to eliminate stress concentration.

[0010] The snowflake configuration cell is symmetrical about the X axis and the Y axis.

[0011] The snowflake configuration cell is symmetrical about the cell center.

[0012] The snowflake-shaped cells are made of a single elastic material, breaking through the process limitations of traditional metamaterial multi-component assembly. This not only eliminates the impact of assembly errors on performance, but also ensures the integrity and consistency of the structure.

[0013] The snowflake-shaped cells are formed using an integrated 3D printing process. 3D printing technology allows for significant design freedom, enabling the precise realization of complex structural configurations while avoiding the technical challenges faced by traditional machining methods when manufacturing microstructures. This integrated manufacturing process not only improves production efficiency and reduces manufacturing costs, but more importantly, ensures the structural integrity and performance stability of the acoustic metamaterial, providing a reliable process guarantee for achieving the desired vibration and noise reduction performance.

[0014] The snowflake-shaped acoustic metamaterial has a consistent overall structural thickness.

[0015] The structural parameters of the snowflake-shaped acoustic metamaterial are highly adjustable, including key geometric dimensions such as the width of the connector, the cubic Bezier curve parameters of the snowflake profile, and the lattice constant.

[0016] Beneficial effects: The present invention has the following advantages:

[0017] (1) Based on the snowflake structure, the present invention designs a type of acoustic metamaterial structure with bandgap characteristics. The unique spatial configuration design of this structure enables the bandgap frequency band to be controlled within the range of 200Hz-5000Hz. This innovative structural design can flexibly adapt to the vibration control requirements of different engineering scenarios and provides a new technical approach to solving broadband vibration problems in practical engineering.

[0018] (2) The present invention is significantly innovative in structural design compared to traditional acoustic metamaterials. Through a unique geometric configuration and efficient spatial hollowing, while maintaining the same volume and thickness, it not only achieves lightweight structure and economical material use, but also ensures the overall stability of the structure. This innovative design concept significantly improves the vibration reduction performance of the present invention, demonstrating excellent vibration suppression effects over a wide frequency range.

[0019] (3) The acoustic metamaterial proposed in the present invention has significant advantages in terms of manufacturing process. It adopts advanced single-material integrated molding technology and realizes assembly-free manufacturing of the overall structure through high-precision 3D printing technology. This manufacturing method breaks through the process limitations of traditional metamaterial multi-component assembly, not only eliminating the impact of assembly errors on performance, but also ensuring the integrity and consistency of the structure. 3D printing technology gives the structure design great freedom, and can accurately realize complex structural configurations, while avoiding the process difficulties faced by traditional processing methods when manufacturing micro-fine structures. This one-piece molding manufacturing process not only improves production efficiency and reduces manufacturing costs, but more importantly, it ensures the structural integrity and performance stability of the acoustic metamaterial, providing a reliable process guarantee for achieving the expected vibration reduction and noise reduction functions;

[0020] (4) The present invention can also achieve flexible control of band gap characteristics through geometric parametric modeling of acoustic metamaterials. This parametric control method is mainly reflected in setting geometric parameters such as the width of the acoustic metamaterial connector, the parameters of the cubic Bezier curve for constructing the snowflake configuration, and the lattice constant as independent parameters, and making targeted adjustments according to the target frequency band requirements to achieve precise control of the band gap position and width. This parametric design method greatly improves the engineering applicability of acoustic metamaterials, enabling them to adapt to the vibration reduction needs of different scenarios. This control method is simple to operate and has significant effects. Without changing the material properties, the expected band gap characteristics can be achieved only by adjusting the geometric parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the cell structure of the acoustic metamaterial structure of the present invention;

[0022] Figure 2 Schematic diagram of the structure of the finite period sequence snowflake configuration acoustic metamaterial of the present invention;

[0023] Figure 3 : is the energy band structure diagram of Example 1 of the present invention;

[0024] Figure 4 is a vibration transmission curve diagram under Example 1 of the present invention;

[0025] Figure 52 is an energy band structure diagram of Example 2 of the present invention;

[0026] Figure 6 is a vibration transmission curve diagram under Example 2 of the present invention;

[0027] Figure 7 : is the energy band structure diagram of Example 3 of the present invention;

[0028] Figure 8 : is a vibration transmission curve diagram under Example 3 of the present invention;

[0029] Figure 9 : is the energy band structure diagram of Example 4 of the present invention;

[0030] Figure 10 is a vibration transmission curve diagram under Example 4 of the present invention;

[0031] Figure 1 In the figure: a is the lattice constant; d1 is the distance between the outer sides of the inner contours of adjacent snowflake configurations; d2 is the horizontal distance between the starting points of the inner contours of adjacent snowflake configurations; d3 is the vertical distance between the starting points of the inner contours of adjacent snowflake configurations; d4 is the horizontal distance between the starting points of the outer contours of adjacent snowflake configurations; d5 is the distance between the outer sides of the outer contours of adjacent snowflake configurations; b is the width of the rectangular connector; h is the thickness of the acoustic metamaterial. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] like Figure 2 As shown, the snowflake-shaped acoustic metamaterial of the present invention comprises a plurality of snowflake-shaped cells periodically arranged in a two-dimensional plane. A single snowflake-shaped cell is as shown in FIG. Figure 1 As shown, it exhibits fourfold symmetry: mirror symmetry about the mutually perpendicular X and Y axes, as well as symmetry about the cell center. A cavity is designed in the center of the snowflake-shaped cell, surrounded by a circular array of identical solid connectors 1. Adjacent solid connectors 1 are connected by hollow snowflake-shaped structures 2. The snowflake-shaped cell of this embodiment is composed of four identical rectangular solid connectors and four identical snowflake-shaped structures.

[0034] The snowflake-shaped structure 2 is parametrically designed using cubic Bezier curves, achieving a continuous and smooth transition between its inner and outer contours. All geometric transitions are rounded to eliminate stress concentrations. The snowflake-shaped cells are formed from a single elastic material through an integrated 3D printing process, offering the dual advantages of structural integrity and ease of manufacturing.

[0035] The structural parameters of the snowflake-shaped acoustic metamaterial of the present invention are highly adjustable, including key geometric dimensions such as connector width, cubic Bezier curve parameters of the snowflake profile, and lattice constant. This parametric design approach endows the metamaterial with excellent bandgap control capabilities: by precisely controlling the structural parameters, not only can the acoustic bandgap be precisely located in a specific frequency band to meet the frequency band requirements of engineering vibration reduction, but parameter adjustment can also significantly expand the bandgap range or induce the generation of multiple bandgaps, thereby significantly improving broadband vibration reduction performance. This design strategy, which combines theoretical guidance with engineering practicality, allows the acoustic metamaterial to be customized according to actual application scenarios, providing an innovative technical solution to address key issues in engineering vibration and noise control.

[0036] Example 1

[0037] In modern civil aircraft, the passing frequency of the low-pressure compressor rotor blades of jet engines is one of the main sources of cabin noise. When the engine is running under typical operating conditions (such as takeoff or cruising), the high-speed rotation of the low-pressure rotor blades will generate strong periodic aerodynamic excitation, and its fundamental frequency and harmonic components are often concentrated in the mid-frequency band of 400-600Hz. The noise energy in this frequency band is transmitted to the cabin through two paths: one is the structure-borne sound transmitted through the engine nacelle structure, and the other is the airborne sound transmitted through the intake and exhaust ducts. Traditional noise reduction methods often have limited control capabilities in this frequency band, resulting in obvious peaks in the cabin noise spectrum near 500Hz, which seriously affects passenger comfort. To this end, the present invention proposes a snowflake configuration acoustic metamaterial structure. By applying the acoustic metamaterial structure to the fuselage sound insulation structure, the vibration suppression effect of this frequency band can be significantly improved.

[0038] The geometrical parameters of the snowflake-shaped acoustic metamaterial structure cell in Example 1 are as follows: lattice constant a is 0.1 m; the outer distance d1 between the inner contours of adjacent snowflake structures is 0.0826 m; the horizontal distance d2 between the inner contour starting points is 0.024 m; the vertical distance d3 is 0.02 m; the horizontal distance d4 between the outer contour starting points is 0.036 m; the outer distance d5 between the outer contours of adjacent snowflake structures is 0.096 m; the thickness h of the acoustic metamaterial is 0.003 m; the width b of the rectangular connector is 0.014 m; and the fillet radius is 0.001 m. The acoustic metamaterial is made of a resin with a Young's modulus of 1.79 GPa and a density of 1.176×10 3 kg / m 3 , the Poisson's ratio is 0.38.

[0039] Through systematic finite element analysis, the band structure of the snowflake-shaped acoustic metamaterial was obtained. Figure 3The calculated results of the energy band structure clearly show that the structure forms a significant band gap feature in the frequency range of 400-590Hz. This physical property means that the propagation of elastic waves in this frequency band is effectively suppressed, thus achieving excellent vibration isolation. To further verify the accuracy of the energy band structure, the vibration transmission curve is also Figure 4 The results are listed in the table, showing that the in-plane vibration mode exhibits obvious attenuation characteristics in the range of 408-708Hz, while the out-of-plane vibration mode exhibits excellent vibration isolation performance in the range of 242-605Hz. It is particularly noteworthy that the attenuation frequency bands of the two vibration modes completely overlap in the range of 408-605Hz, forming a complete band gap as wide as 197Hz. This result is highly consistent with the band structure analysis. Even more noteworthy is that the maximum attenuation amplitude of the structure within the band gap range exceeds 200dB, fully demonstrating its excellent vibration reduction performance. The analysis results of these systems strongly prove that the snowflake-shaped acoustic metamaterial designed in this embodiment has an outstanding vibration reduction effect in the frequency band of 400-600Hz, providing an innovative solution to the engineering problem of engine blade passing noise.

[0040] Example 2

[0041] Strong winds can cause significant high-frequency vibration noise in building glass curtain walls, with frequencies primarily concentrated in the 600-900 Hz range. This noise is primarily caused by two mechanisms: first, when wind speeds exceed 10 m / s, the turbulent pressure fluctuations generated on the curtain wall surface excite high-order modal vibrations in the glass panels; second, the periodic shedding of Karman vortexes formed as air flows around the curtain wall edges causes bending vibrations in the glass. These vibrations propagate through the air, creating an unpleasant "whistling" sound that can even disrupt the work and rest of building occupants. Furthermore, the widespread trend of large glass curtain wall designs in modern buildings has exacerbated the problem of wind-induced noise. Furthermore, with the increasing height of urban buildings and the intensification of the "urban canyon effect," the wind loads and resulting noise problems faced by high-rise buildings are becoming increasingly severe. Traditional methods, such as increasing glass thickness or using interlayers, are unable to effectively suppress vibrations in this frequency range. Therefore, this paper proposes a snowflake-shaped acoustic metamaterial structure that effectively addresses the problem of high-frequency wind-induced noise.

[0042] The geometrical parameters of the snowflake-shaped acoustic metamaterial structure cell in Example 2 are as follows: lattice constant a is 0.064 m; the outer distance d1 between the inner contours of adjacent snowflake structures is 0.0442 m; the horizontal distance d2 between the inner contour starting points is 0.02 m; the vertical distance d3 is 0.01 m; the horizontal distance d4 between the outer contour starting points is 0.024 m; the outer distance d5 between the outer contours of adjacent snowflake structures is 0.0564 m; the thickness h of the acoustic metamaterial is 0.002 m; the width b of the rectangular connector is 0.008 m; and the fillet radius is 0.001 m. The acoustic metamaterial is made of a resin with a Young's modulus of 1.79 GPa and a density of 1.176×10 3 kg / m 3 , the Poisson's ratio is 0.38.

[0043] Through finite element analysis, the band structure of the acoustic metamaterial is shown as Figure 5 shown. Figure 5 It is clearly shown that the structure successfully opens a significant band gap in the frequency range of 655-1119 Hz. Figure 6 The results of the vibration transmission analysis are presented: for the in-plane vibration mode, there is a clear band gap in the range of 716-1365Hz; while the out-of-plane vibration mode shows excellent band gap characteristics in the range of 633-1188Hz. It is worth noting that the band gaps of the two vibration modes completely overlap in the range of 716-1188Hz, forming a complete band gap with a width of 472Hz. This result is in good agreement with the band structure calculation. Of particular note is that the structure exhibits excellent vibration attenuation performance within the band gap range, with a maximum attenuation of up to 250dB. These results fully demonstrate that the acoustic metamaterial can effectively suppress high-frequency wind vibration noise in the frequency band of 600-900Hz, providing an innovative technical solution to the problem of wind noise in building curtain walls.

[0044] Example 3

[0045] In everyday life, mechanical vibrations are a common problem for various common devices, with their frequencies primarily concentrated in the low- to medium-frequency range of 200-500Hz. For example, the vibration frequency generated by the motor of a household range hood is typically 250-350Hz. The structural vibrations caused by the compressor of an air conditioner outdoor unit are mostly in the 300-450Hz range. And the vibrations generated by the traction motor and guide rail system during elevator operation are concentrated in the 200-400Hz range. These persistent mechanical vibrations not only produce uncomfortable low-frequency noise but, over time, can also cause structural fatigue in the equipment, shortening its service life. To address this widespread engineering problem, the snowflake-shaped acoustic metamaterial proposed in this invention demonstrates excellent adaptability. By adjusting the metamaterial's geometric parameters, its bandgap characteristics can be precisely controlled to effectively cover the target frequency range of 200-500Hz, providing a new technical approach for vibration control in household appliances and building equipment.

[0046] The geometrical parameters of the snowflake-shaped acoustic metamaterial structure cell in Example 3 are as follows: lattice constant a is 0.12 m; the outer distance d1 between the inner contours of adjacent snowflake structures is 0.0914 m; the horizontal distance d2 between the inner contour starting points is 0.024 m; the vertical distance d3 is 0.02 m; the horizontal distance d4 between the outer contour starting points is 0.036 m; the outer distance d5 between the outer contours of adjacent snowflake structures is 0.1046 m; the thickness h of the acoustic metamaterial is 0.0045 m; the width b of the rectangular connector is 0.015 m; and the fillet radius is 0.001 m. The acoustic metamaterial is made of a resin with a Young's modulus of 1.79 GPa and a density of 1.176×10 3 kg / m 3 , the Poisson's ratio is 0.38.

[0047] Through systematic finite element calculations, the band structure characteristics of the snowflake-shaped acoustic metamaterial were obtained. Figure 7 The energy band structure diagram clearly shows that the metamaterial structure exhibits two significant band gap characteristics: the first band gap is located in the frequency range of 267-470Hz, and the second band gap is located in the frequency range of 493-591Hz. To further verify these band gap characteristics, Figure 8Vibration transmission analysis curves were presented, showing that for the in-plane vibration mode, significant vibration attenuation regions were observed in the 274-505Hz and 522-669Hz ranges, respectively. In the out-of-plane vibration mode, a wider attenuation frequency range of 258-622Hz was observed. Both vibration modes formed complete band gaps in the 274-505Hz and 522-622Hz ranges, respectively, a result that generally agrees with band structure calculations. The metamaterial exhibited excellent vibration attenuation within the band gap range, with a maximum attenuation approaching 250dB. This excellent physical property means that when the vibration frequency falls within the aforementioned band gap range, elastic wave propagation is significantly suppressed. This property makes it valuable for addressing low- and medium-frequency vibration issues in household appliances and building equipment, thereby extending equipment life and improving user comfort.

[0048] Example 4

[0049] Taking high-speed railways and subway systems as an example, when a train brakes when entering a station, it generates high-frequency vibration noise of 2000-5000Hz. According to measured data from the Institute of Occupational Hygiene of the Ministry of Railways, the vibration sound pressure level generally reaches above 80dB within 30 meters of the centerline of the track. This continuous high-frequency noise not only seriously affects the quality of life of residents along the line, but long-term exposure can also lead to health problems such as hearing loss and sleep disorders. In response to this engineering challenge, the present invention proposes a snowflake-configured acoustic metamaterial solution. Through its unique bandgap characteristic design, the acoustic metamaterial can effectively attenuate vibration energy in a specific high-frequency band, providing a new technical approach to solving high-frequency noise pollution in rail transit.

[0050] The geometrical parameters of the snowflake-shaped acoustic metamaterial structure cell in Example 4 are as follows: lattice constant a is 0.018 m; the distance d1 between the inner and outer contours of adjacent snowflake structures is 0.01026 m; the horizontal distance d2 between the inner contour starting points is 0.0026 m; the vertical distance d3 is 0.0024 m; the horizontal distance d4 between the outer contour starting points is 0.004 m; the distance d5 between the outer contours of adjacent snowflake structures is 0.01162 m; the thickness h of the acoustic metamaterial is 0.0005 m; the width b of the rectangular connector is 0.0016 m; and the fillet radius is 0.0001 m. The acoustic metamaterial is made of a resin with a Young's modulus of 1.79 GPa and a density of 1.176×10 3 kg / m 3 , the Poisson's ratio is 0.38.

[0051] The snowflake-shaped acoustic metamaterial designed in the present invention can exhibit excellent high-frequency vibration control performance. Figure 9The calculated results of the energy band structure clearly reveal that the material has significant band gap characteristics in three characteristic frequency bands: 2558-2904Hz, 3066-4859Hz and 4941-5765Hz. To verify this characteristic, Figure 10 Vibration transmission analysis curves were further presented, showing that the in-plane vibration mode exhibited significant attenuation in the frequency bands of 2665-2971Hz, 3097-5158Hz, and 5212-6094Hz, while the out-of-plane vibration mode exhibited excellent vibration isolation performance across a wide frequency range of 2323-6049Hz. Cross-comparison analysis revealed that the metamaterial formed complete band gaps in the frequency bands of 2665-2971Hz, 3097-5158Hz, and 5212-6049Hz, a result that was generally consistent with the band structure predictions. Of particular note, the maximum attenuation exceeded 300dB in the in-plane vibration mode and over 200dB in the out-of-plane vibration mode, fully demonstrating its superior performance in controlling high-frequency vibrations in transportation. This snowflake-shaped acoustic metamaterial provides an innovative technical solution to address the major public health issue of noise pollution in urban rail transit.

[0052] The acoustic metamaterial cell of this invention utilizes a hollow geometric design, achieving both lightweight performance and bandgap characteristics across a wide frequency range. The geometric parameters of this acoustic metamaterial can be precisely controlled, and by varying its key dimensional characteristics, efficient control of vibrations within specific frequency bands can be achieved, thereby meeting the vibration and noise reduction requirements of various engineering scenarios. This innovative structural design maintains the material's lightweight properties while also providing excellent broadband vibration suppression capabilities, providing a novel solution for engineering vibration reduction.

Claims

1. A snowflake-shaped acoustic metamaterial, characterized in that: It includes several snowflake-shaped cells arranged periodically in a two-dimensional plane. The central area of ​​a single snowflake-shaped cell is designed with a cavity. There are multiple identical solid connectors in a circular array around the cavity, and snowflake-shaped structures are connected between adjacent solid connectors.

2. The snowflake-shaped acoustic metamaterial according to claim 1, characterized in that: The snowflake-shaped structure is parameterized using a cubic Bezier curve.

3. The snowflake-shaped acoustic metamaterial according to claim 1 or 2, characterized in that: The snowflake-shaped structure adopts a hollow structure.

4. The snowflake-shaped acoustic metamaterial according to claim 1, wherein: Each geometric mutation portion of the snowflake configuration cell is rounded.

5. The snowflake-shaped acoustic metamaterial according to claim 1 or 4, characterized in that: The snowflake configuration cell is symmetrical about the X axis and the Y axis.

6. The snowflake-shaped acoustic metamaterial according to claim 5, characterized in that: The snowflake configuration cell is symmetrical about the cell center.

7. The snowflake-shaped acoustic metamaterial according to claim 1, wherein: The snowflake-shaped cells are made of a single elastic material.

8. The snowflake-shaped acoustic metamaterial according to claim 7, wherein: The snowflake-shaped cells are formed by an integrated 3D printing process.

9. The snowflake-shaped acoustic metamaterial according to claim 1, wherein: The snowflake-shaped acoustic metamaterial has a consistent overall structural thickness.

10. The snowflake-shaped acoustic metamaterial according to claim 1 or 9, characterized in that: The structural parameters of the snowflake-shaped acoustic metamaterial are highly adjustable.

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