S0 mode selectable acoustic metamaterial structure and optimization and application thereof

Abstract

The invention discloses an S0 mode selectable acoustic metamaterial structure and optimization and application thereof. The waveguide layer adopts a stepped cuboid unit cell structure and is used for sound wave propagation; the regulation and control layer is used for selecting S0 modal waves and inhibiting other sound waves; the regulation and control layer comprises a first regulation and control layer and a second regulation and control layer; the waveguide layer, the first regulation and control layer and the second regulation and control layer are sequentially stacked from top to bottom. The optimization method comprises the steps of obtaining regulation and control layer structure parameters, carrying out parameter setting and population initialization, then simulating a calculation model to solve characteristic frequency, then obtaining single S0 modal area bandwidth, calculating a fitness function, and finally carrying out iterative calculation until a stop condition is met. The definition of the fitness function is related to the reciprocal of the bandwidth of the single S0 modal area, and the larger the bandwidth is, the smaller the fitness function is, and the better the optimization effect is. The optimized metamaterial array is arranged on a regulation and control structure and is matched with an excitation transducer to realize selective propagation of S0 modal waves.

Description

Technical Field

[0001] The present invention relates to the fields of acoustic metamaterials and structural acoustics, and particularly to an S 0 -mode selectable acoustic metamaterial structure and its optimization and application. Background Art

[0002] There are usually multiple modes in the sound waves propagating in a structure. In the processes of using sound waves for material property testing, structural health monitoring, etc., extracting effective modes for analysis is a difficult problem. Simplifying the sound wave modes and thus simplifying the signal interpretation helps to improve the accuracy and efficiency of the above-mentioned tests.

[0003] Currently, acoustic metamaterials are a new type of acoustic material or structure composed of periodically arranged specially designed artificial acoustic microstructure units in an elastic medium. They have extraordinary physical properties such as negative mass density, negative refraction, and negative elastic modulus that are not possessed by natural materials, and can control the propagation characteristics of sound waves. Therefore, they have great potential for realizing the simplified extraction of modes. In the field of acoustics, the S 0 -mode wave is an important type of LAMB wave and has application value in fields such as damage detection by ultrasonic guided wave technology. However, in practical applications, it is often necessary to effectively obtain the propagating S 0 -mode wave from sound waves of multiple modes, and then analyze the structure. Acoustic metamaterials provide a new way to obtain the S 0 -mode wave. How to design an acoustic metamaterial structure with high-efficiency S 0 -mode selectivity, how to optimize the performance of acoustic metamaterials to meet the actual application requirements, etc. still need further research and solution. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings and deficiencies of the prior art, and provide an S 0 -mode selectable acoustic metamaterial structure and its optimization and application.

[0005] The present invention is realized through the following technical solutions:

[0006] An S 0 -mode selectable acoustic metamaterial structure, comprising:

[0007] A waveguide layer T1 for sound wave propagation;

[0008] A regulation layer for selecting the S 0 -mode wave and suppressing other sound waves;

[0009] The regulation layer includes a first regulation layer T2 and a second regulation layer T3;

[0010] The waveguide layer T1, the first regulation layer T2, and the second regulation layer T3 are stacked in sequence from bottom to top.

[0011] The waveguide layer T1 is made of the same material as the structure to be measured; the length and width of the waveguide layer T1 are equal, and the thickness is the same as that of the structure to be measured;

[0012] The length of the regulation layer is the same as that of the waveguide layer T1, and the width b of the second regulation layer T3 3 ≤ the width b of the first regulation layer T2 2 < the width a of the waveguide layer T1.

[0013] The frequency of the propagating wave in the structure to be measured is within the frequency range of a single S 0 mode region, and the order of magnitude of the frequency is above 10 4 above.

[0014] The present invention S 0 An optimization method for a modal optional acoustic metamaterial structure includes the following steps:

[0015] S1 Obtain N structural parameters in the regulation layer for optimization;

[0016] S2 Perform parameter setting and population initialization according to the N structural parameters;

[0017] S3 Apply the parameter amplitude to the simulation calculation model to solve the eigenfrequency of the new model;

[0018] S4 Calculate the bandwidth of a single S 0 mode region according to the eigenfrequency;

[0019] S5 Calculate the fitness function according to the current bandwidth;

[0020] S6 The fitness conditions are as follows:

[0021] If the fitness does not meet the stop condition, perform population selection, crossover and mutation, and extract the optimized offspring to start a new round of iterative calculation;

[0022] If the fitness meets the stop condition, output the optimal structural parameters and stop the calculation.

[0023] The N structural parameters in step S1 at least include the width and thickness of the second regulation layer T3, and the width and thickness of the first regulation layer T2.

[0024] The structural parameters in step S1 are used to automatically update the metamaterial unit model in real time. In each unit model, the eigenfrequency in the Γ-X direction of the parametric scanning unit cell Brillouin zone is adopted to obtain the band structure.

[0025] Obtain the modal distributions according to the band structure, and then calculate the bandwidth of the single S0 mode region of the acoustic metamaterial under the current structural parameters.

[0026] The definition of the fitness function described in step S5 is as follows:

[0027]

[0028] W is the bandwidth of a single S 0 modal region. The larger the bandwidth, the smaller the fitness function and the better the optimization effect. The optimization iteration calculation is stopped according to the value of the fitness function F ≤ θ, where θ is the set expected optimization effect value.

[0029] The S 0 modal optional acoustic metamaterial structure optimized by the above optimization method: The optimized S 0 modal optional acoustic metamaterial structure is arranged on the structure to be measured through an array, and the structure to be measured is used as the waveguide layer of the S 0 modal optional acoustic metamaterial structure; the excitation transducer is arranged on one side of the S 0 modal optional acoustic metamaterial structure. After the initial propagating wave with multiple modes excited passes through the S 0 modal optional acoustic metamaterial structure, the wave of the selectable S 0 mode can propagate through, and the propagation of other mode waves is suppressed.

[0030] The present invention has the following advantages and effects compared with the prior art:

[0031] The S 0 modal optional acoustic metamaterial designed by the present invention has a single S 0 modal region, which can realize the selection of the S 0 mode propagation among multiple acoustic modes and suppress other modes, thereby improving the transmission efficiency and quality of acoustic signals.

[0032] Through the stepped cuboid unit cell design, the S 0 modal optional acoustic metamaterial structure is divided into a waveguide layer, a first regulation layer T2 and a second regulation layer T3, and the structural parameters (such as thickness, width, etc.) of the first regulation layer T2 and the second regulation layer T3 can be flexibly adjusted, so as to regulate the propagation characteristics of sound waves and broaden the single S 0 modal region and optimize the performance of the acoustic metamaterial.

[0033] The S 0 modal optional acoustic metamaterial structure optimization method of the present invention can automatically update the metamaterial unit model in real time by adjusting the structural parameters of the regulation layer, and calculate the energy band structure and the bandwidth of the single S0 modal region, making the design of the acoustic metamaterial more flexible and intelligent, and significantly improving the regulation performance of the metamaterial. Description of the Drawings

[0034] Figure 1 is S0 Modal optional acoustic metamaterial structure and its Brillouin zone diagram;

[0035] Figure 2 is the initialized S 0 Energy band diagram of modal optional acoustic metamaterials;

[0036] Figure 3 is S 0 Flow chart of the optimization method for modal optional acoustic metamaterial structure;

[0037] Figure 4 Among them, Figure (a) is the variation diagram of the optimal fitness with the number of iterations; Figure (b) is the optimal b 2 and b 3 Variation diagram of the value with the number of iterations; Figure (c) is the optimized energy band structure diagram;

[0038] Figure 5 is the response diagram of the structure to be measured at a frequency of 50 kHz; Figure (a) is the response diagram of the regulation structure without metamaterials; Figure (b) is the x-direction response diagram of the regulation structure of the model with metamaterials, (c) is the y-direction response diagram of the regulation structure of the model with metamaterials; Figure (d) is the z-direction response diagram of the regulation structure of the model with metamaterials;

[0039] Figure 6 is the signal diagram received at the signal acquisition point under the excitation of a 50 kHz frequency; Figure (a) without metamaterials; Figure (b) with metamaterials;

[0040] Figure 7 is the frequency-wavenumber analysis diagram under the excitation of a 50 kHz frequency; Figure (a) without metamaterials; Figure (b) with metamaterials. Specific implementation mode

[0041] The present invention will be further described in detail below with reference to specific embodiments.

[0042] As Figure 1 shown. The S of the present invention 0 Design of modal optional acoustic metamaterial structure, stepped cuboid unit cell, with a three-layer structure;

[0043] Waveguide layer T1 for acoustic wave propagation;

[0044] Regulation layer for selecting S0 mode waves and suppressing other acoustic waves;

[0045] The regulation layer includes a first regulation layer T2 and a second regulation layer T3;

[0046] The waveguide layer T1, the first regulation layer T2 and the second regulation layer T3 are stacked in sequence from bottom to top;

[0047] The S of the present invention 0The modal - selectable acoustic metamaterial structure has a metallic material, which is the same as the material of the structure to be measured where the waveguide layer is located. In this example, the material used is aluminum, and the material parameters are density ρ = 2680 kg / m 3 , Young's modulus E = 72 GPa, and Poisson's ratio υ = 0.34.

[0048] Preferably, the length and width of the waveguide layer T1 are equal, and the thickness is the same as the thickness of the regulation structure (the structure to be measured); in this example, the length and width of the waveguide layer T1 are both the lattice constant a = 10 mm, and the thickness h 1 = 1 mm.

[0049] The length of the regulation layer is the same as the length of the waveguide layer, and the width b of the second regulation layer T3 3 ≤ the width b of the first regulation layer T2 2 < the width a of the waveguide layer T1. Set the initialized parameters as: the width b of the first regulation layer T2 2 = 4 mm, and the width b of the second regulation layer T3 3 = 3 mm; the thickness h of the first regulation layer T2 2 = 1 mm, and the thickness h of the second regulation layer T3 3 = 2 mm.

[0050] The S 0 modal - selectable acoustic metamaterial has a single S 0 modal region; the frequency of the propagating wave in the structure to be measured is within the frequency range of the single S 0 modal region, and the order of magnitude of the frequency is above 10 4 . Figure 2 For the S 0 modal - selectable acoustic metamaterial under the initialized structural material and geometric parameters, the energy - band diagram is shown. From Figure 2 it can be clearly seen that in the range of 24.9 kHz - 61.7 kHz, there is a dispersion region with a bandwidth of 36.8 kHz. In this region, the LAMB wave only has the S 0 mode. And set the excitation frequency of the sound wave f = 50 kHz. On this basis, the S0 modal - selectable acoustic metamaterial structure will be further optimized.

[0051] Preferably, by adjusting the structural parameters of the regulation layer, the equivalent mass density of the stepped cuboid unit cell can be changed, and then the single S 0 modal region can be broadened and optimized.

[0052] As Figure 3 shown, the optimization method of the S 0 modal - selectable acoustic metamaterial structure can be realized through the following steps:

[0053] S1 Obtain N structural parameters in the regulation layer for optimization;

[0054] S2 performs parameter setting and population initialization according to N structural parameters;

[0055] S3 inputs the parameter amplitudes into the simulation calculation model and solves the characteristic frequencies of the new model;

[0056] S4 calculates the bandwidth of a single S 0 modal region based on the characteristic frequencies;

[0057] S5 calculates the fitness function according to the current bandwidth;

[0058] S6 If the fitness does not meet the stop condition, perform population selection, crossover, and mutation, extract the optimized offspring, and start a new round of iterative calculation; if the fitness meets the stop condition, output the optimal structural parameters and stop the calculation.

[0059] The N structural parameters at least include the width b 3 and thickness h 3 of the upper regulation layer, and the width b 2 and thickness h 2 of the middle regulation layer. In this example, only the width b 2 of the middle regulation layer and the width b 3 of the upper regulation layer are optimized.

[0060] The structural parameters can automatically update the metamaterial unit model in real time. In each unit model, the characteristic frequencies in the Γ-X direction of the cell Brillouin zone are scanned parametrically to obtain the band structure.

[0061] Based on the band structure, the modal distributions are obtained, and then the bandwidth of the single S 0 modal region of the acoustic metamaterial under the current structural parameters is calculated.

[0062] The fitness function is defined as:

[0063]

[0064] W is the bandwidth of the single S 0 modal region. The larger the bandwidth, the smaller the fitness function, and the better the optimization effect. The optimization iterative calculation is stopped according to the value of the fitness function F ≤ θ, where θ is the set expected optimization effect value. Figure 4 (a) shows the change process of the optimal fitness with the number of iterations in each generation. The fitness is related to the reciprocal of the bandwidth of the single S0 modal region. Therefore, the larger the bandwidth, the smaller the value of the fitness, and it gradually converges. Figure 4 (b) shows the corresponding change process of the optimal structural parameters. The final structural parameters are [b 2 , b 3 = [7.35 mm, 6.51 mm]. S 0Optimize the structural parameters of the mode-selectable acoustic metamaterial. The optimized band structure is as shown in Figure 4 (c). After optimization, the range of the single S 0 mode region is 22.9 kHz - 83.7 kHz, and the bandwidth is 60.8 kHz. It can be seen that after optimization, the bandwidth of the single S 0 mode region has been greatly improved, which is 65.2% higher than the bandwidth before optimization.

[0065] Arrange the optimized S 0 mode-selectable acoustic metamaterial structure on the structure to be measured through an array, and use the structure to be measured as the waveguide layer of the S 0 mode-selectable acoustic metamaterial structure; arrange the excitation transducer on one side of the S 0 mode-selectable acoustic metamaterial structure. After the initial propagating wave with multiple modes is excited and passes through the S 0 mode-selectable acoustic metamaterial structure, the wave of the S 0 mode can be selected to propagate, and the propagation of waves of other modes can be suppressed.

[0066] In this example, the structure to be measured (regulation structure) is a thin aluminum plate with a length, width and thickness of 500 mm × 10 mm × 1 mm, and the metamaterial array is 5 × 1. Use a piezoelectric transducer PZT to excite a 10-cycle signal modulated by a Hanning window at 50 kHz to generate S 0 and A 0 mode LAMB waves. And set a series of signal acquisition points on the aluminum plate to collect wave signals for modal analysis.

[0067] Next, show the mode selection effect of the S 0 mode-selectable acoustic metamaterial structure in this example. Figure 5 (a) shows the response results of the regulation structure without metamaterial under the excitation of a 50 kHz frequency. It can be seen that there are 2 different modes of LAMB waves propagating in the aluminum plate regulation structure. Add the S 0 mode-selectable acoustic metamaterial to the model, and detect the equivalent displacement in different directions to analyze its waveform. Among them, the displacement in the x direction is the most obvious, because the wave propagates along the x direction. From Figure 5 (b), it can be seen that after the LAMB wave passes through the metamaterial, the A 0 mode is suppressed, and only the wave of the S 0 mode can propagate. In addition, the SH 0 wave in the plate mainly provides the displacement in the y direction. Figure 5 (c) shows that there is almost no deformation in the y direction after the action of the metamaterial, indicating that the wave of the SH 0 mode is also suppressed. Therefore, the S 0 mode-selectable acoustic metamaterial can well select the S0 The modal LAMB wave propagates while suppressing the propagation of other waves.

[0068] Furthermore, time-domain analysis is performed on the signals received at the signal acquisition points. From Figure 6 (a), it can be seen that there are obviously two modes in the waves propagating in the aluminum plate regulation structure without the metamaterial. By solving the wave numbers of these signals, a frequency-wave number distribution field is obtained, as shown in Figure 7 (a). It can be seen that most of the two modes are located in the S 0 and A 0 regions. Therefore, there are S 0 and A 0 two modes in the waves propagating in the aluminum plate regulation structure without the metamaterial. When the S 0 mode-selectable acoustic metamaterial is added to the aluminum plate, there is only an obvious single mode in the signal, as shown in Figure 6 (b). In addition, due to the effect of the metamaterial, the following tail wave signals are brought. In actual detection, these tail wave signals can be ignored due to their insignificant amplitudes. Figure 7 (b) shows the frequency-wave number analysis of the received signals of the regulation structure with the metamaterial. It can be seen that the mode is distributed in the S 0 region. In summary, the S 0 mode-selectable acoustic metamaterial can well select the S 0 mode LAMB wave to propagate in the aluminum plate regulation structure.

[0069] As described above, the present invention can be preferably realized.

[0070] The implementation modes of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An S0 mode selectable acoustic metamaterial structure, characterized in that include: Waveguide layer T1 for sound wave propagation; A control layer for selecting S0 mode waves and suppressing other sound waves; The regulating layer includes a first regulating layer T2 and a second regulating layer T3; The waveguide layer T1, the first regulating layer T2 and the second regulating layer T3 are stacked in sequence from bottom to top.

2. The S0 mode selectable acoustic metamaterial structure according to claim 1, characterized in that: The waveguide layer T1 is made of the same material as the structure to be measured; the length and width of the waveguide layer T1 are equal, and the thickness is consistent with the thickness of the structure to be measured; The length of the regulating layer is consistent with the length of the waveguide layer T1, and the width b3 of the second regulating layer T3 ≤ the width b2 of the first regulating layer T2 < the width a of the waveguide layer T1.

3. The S0 mode selectable acoustic metamaterial structure according to claim 1, characterized in that: The frequency of the propagating wave in the structure to be tested is within the frequency range of the single S0 mode region, and the frequency order of magnitude is 10 4 Above.

4. The optimization method of the S0 mode selectable acoustic metamaterial structure according to any one of claims 1 to 3, characterized in that The steps include: S1 obtains N structural parameters in the control layer for optimization; S2 performs parameter setting and population initialization according to N structural parameters; S3 transfers the parameter amplitude to the simulation calculation model and solves the characteristic frequency of the new model; S4 calculates the bandwidth of a single S0 mode region based on the characteristic frequency; S5 calculates the fitness function according to the current bandwidth; S6 fitness conditions are as follows: If the fitness does not meet the stopping condition, population selection, crossover and mutation are performed, and the optimized offspring are extracted to start a new round of iterative calculation; If the fitness meets the stopping condition, the optimal structural parameters are output and the calculation stops.

5. The optimization method according to claim 4, characterized in that: The N structural parameters in step S1 at least include the width and thickness of the second regulating layer T3 and the width and thickness of the first regulating layer T2.

6. The optimization method according to claim 5, characterized in that: The structural parameters described in step S1 are used to automatically assign and update the metamaterial unit model in real time. In each unit model, a parameterized scan of the characteristic frequency in the Γ-X direction of the Brillouin zone of the unit cell is used to obtain the band structure.

7. The optimization method according to claim 6, characterized in that: The distribution of each mode is obtained according to the band structure, and then the bandwidth of a single S0 mode region of the acoustic metamaterial under the current structural parameters is calculated.

8. The optimization method according to claim 4, characterized in that: The fitness function in step S5 is defined as: W is the bandwidth of a single S0 modal region. The larger the bandwidth, the smaller the fitness function and the better the optimization effect. The optimization iteration calculation is stopped according to the value of the fitness function F≤θ, where θ is the expected optimization effect value set.

9. An application of an S0 mode-selective acoustic metamaterial structure optimized by the optimization method according to any one of claims 4 to 8, wherein the optimized S0 mode-selective acoustic metamaterial structure is arranged on a structure to be tested through an array, and the structure to be tested is used as a waveguide layer of the S0 mode-selective acoustic metamaterial structure; an excitation transducer is arranged on one side of the S0 mode-selective acoustic metamaterial structure, and after the excited initial propagation wave with multiple modes passes through the S0 mode-selective acoustic metamaterial structure, the wave of the S0 mode can be selected to propagate, and the propagation of other mode waves is suppressed.

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