Sound absorbing metamaterials for near-boundary lesion ultrasound imaging detection, design methods and ultrasound imaging detection methods

Abstract

The present application relates to a kind of sound-absorbing metamaterials for near boundary damage ultrasonic imaging detection and design method and ultrasonic imaging detection method, sound-absorbing metamaterials are made of at least 1 sound-absorbing metamaterial unit, design method includes: according to ultrasonic detection frequency, the geometric parameter range and material parameter range of sound-absorbing metamaterial unit are determined;Establish near boundary defect ultrasonic lamb wave detection finite element model, the reflection phase and reflectivity of sound-absorbing metamaterial unit under different geometric parameters and material parameters are calculated;According to multiple scattering theory, the number of sound-absorbing metamaterial unit is determined, so that the diffraction propagation mode of sound-absorbing metamaterial only exists 0 order diffraction propagation mode;The optimal geometric parameter and material parameter of sound-absorbing metamaterial unit are determined.Compared with prior art, the present application has the advantages of reducing the influence of high-energy boundary reflected wave on imaging result, improving the sensitivity and imaging accuracy of near boundary defect ultrasonic lamb wave detection and the like.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic testing and imaging, specifically relating to a sound-absorbing metamaterial for ultrasonic imaging detection of near-boundary damage, its design method, and an ultrasonic imaging detection method. Background Technology

[0002] Ultrasonic Lamb waves are widely used in the non-destructive testing of plate structures due to their advantages such as long propagation distance, high sensitivity, and suitability for large-area rapid scanning. However, the excitation signal generates strong reflected waves after propagating to the structural boundary. The energy of these reflected waves is usually much higher than that of the scattered waves generated at the defect, and their arrival times are very close. This means that the defect scattered waves are often submerged in the high-energy boundary reflected waves, making it difficult for traditional ultrasonic imaging algorithms to accurately identify defects in the near-boundary region. This boundary effect is particularly prominent in practical engineering structures such as aircraft skin, ship hull plates, and pressure vessels, because many critical defects are often located at structural edges, connections, or confined spaces. Therefore, accurately and efficiently achieving near-boundary defect detection and imaging has become a major challenge in the field of ultrasonic non-destructive testing.

[0003] Therefore, how to suppress boundary reflected waves and enhance defect scattered waves has become an important research direction in the field of ultrasonic testing and imaging. Existing research often attempts to weaken the influence of boundary reflected waves by improving signal processing algorithms, optimizing array arrangements, or using absorbing materials. For example, patent CN119246692B discloses a composite material damage imaging method based on the spatiotemporal cross-correlation of ultrasonic guided wave fields, which uses a frequency wavenumber domain filtering algorithm to selectively suppress the wavenumber component of reflected waves in the frequency wavenumber domain. However, relying on algorithms to suppress boundary interference is susceptible to noise, and when the time overlap between scattered and reflected waves is severe, the imaging will be severely distorted. Conventional sound-absorbing materials are difficult to achieve efficient absorption at low frequencies and often require large thicknesses, making them unsuitable for the attached testing requirements of plate-like structures. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a sound-absorbing metamaterial and its design method for ultrasonic imaging detection of near-boundary damage, as well as an ultrasonic imaging detection method. Based on the principle of local resonance, a sound-absorbing metamaterial is designed, and multiple scattering theory is used to achieve absorption and wave packet delay of boundary reflected waves. This prevents the defect scattered waves generated by defects near the boundary from being submerged by boundary reflected waves, reduces the influence of high-energy boundary reflected waves on the imaging results, and improves the sensitivity and imaging accuracy of ultrasonic Lamb wave detection of defects near the boundary.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for designing a sound-absorbing metamaterial for near-boundary damage ultrasound imaging detection, wherein the sound-absorbing metamaterial is composed of at least one sound-absorbing metamaterial unit, the sound-absorbing metamaterial unit comprising stacked springs and mass blocks, and the design method includes:

[0007] The ultrasonic testing frequency is obtained, and the tensile resonance frequency of the sound-absorbing metamaterial unit is calculated using finite element simulation software. Then, the geometric parameter range and material parameter range of the sound-absorbing metamaterial unit are determined based on the ultrasonic testing frequency.

[0008] Based on the aforementioned range of geometric and material parameters, a finite element model for ultrasonic Lamb wave detection of near-boundary defects is established, and the reflection phase and reflectivity of the sound-absorbing metamaterial unit under different geometric and material parameters are calculated.

[0009] Determine the Lamb wave number of the test plate, and based on the multiple scattering theory, determine the number of the sound-absorbing metamaterial units so that the diffraction propagation mode of the sound-absorbing metamaterial only has the 0th order diffraction propagation mode.

[0010] Based on the number of sound-absorbing metamaterial units, the reflection phase and reflectivity of different sound-absorbing metamaterial units, and the requirement for uniform distribution of sound-absorbing metamaterial units, the optimal geometric parameters and material parameters of the sound-absorbing metamaterial units are determined.

[0011] Furthermore, the difference between the tensile resonance frequency and the ultrasonic detection frequency is less than a set threshold.

[0012] Furthermore, the Lamb wavenumber is calculated based on the frequency-thickness product of the tested plate.

[0013] Furthermore, the structure of the spring and the mass block is a cuboid with the same length and width, and the geometric parameters include the length, width, and height of the spring and the length, width, and height of the mass block.

[0014] Furthermore, the spring is made of polyurethane;

[0015] The material of the mass block includes aluminum.

[0016] Furthermore, the conditional formula for the existence of only the 0th order diffraction propagation mode in the diffraction propagation mode of the sound-absorbing metamaterial is expressed as follows:

[0017] ,

[0018] In the formula, roundup means rounding up. n The number of sound-absorbing metamaterial units. w p For the width of the spring and the mass block, k 0 represents the Lamb wavenumber of the board under test.

[0019] Furthermore, when establishing the finite element model for ultrasonic Lamb wave detection of near-boundary defects, the test plate is used as the substrate, and the sound-absorbing metamaterial is installed at the boundary of the substrate.

[0020] Secondly, the present invention also provides a sound-absorbing metamaterial for ultrasound imaging detection of near-boundary damage, which is designed and obtained using the sound-absorbing metamaterial design method described above.

[0021] Thirdly, the present invention also provides a method for detecting near-boundary damage using ultrasound imaging, the method comprising the following steps:

[0022] The sound-absorbing metamaterial designed based on the sound-absorbing metamaterial design method described above is installed at the boundary of the plate under test.

[0023] An excitation signal with an ultrasonic detection frequency is incident on the plate under test, and the reflected wave signal is collected.

[0024] The reflected wave signal is processed and imaged using a full-focusing imaging algorithm, and defect detection is achieved based on the imaging results.

[0025] Furthermore, the sound-absorbing metamaterial is installed at the boundary of the test plate by adhesive bonding.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention designs a sound-absorbing metamaterial. By adjusting the geometric and material parameters of the sound-absorbing metamaterial unit, the absorption and wave packet delay of boundary reflected waves can be achieved. Thus, when the sound-absorbing metamaterial is combined with ultrasonic Lamb wave detection, the detection sensitivity and imaging accuracy of defects near the boundary can be improved.

[0028] 2. This invention can change the operating frequency by adjusting the geometric and material parameters of the sound-absorbing metamaterial to meet different application requirements;

[0029] 3. The sound-absorbing metamaterial of the present invention adopts an adhesive structure, which is easy to install and avoids damage to the structure to be tested, and has high application potential in the field of non-destructive testing. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the design process of the sound-absorbing metamaterial in this invention;

[0031] Figure 2 This is a schematic diagram of the principle of ultrasonic imaging detection of near-boundary damage based on sound-absorbing metamaterials in this invention. In this diagram, (2a) shows the reflected echo without sound-absorbing metamaterials, and (2b) shows the reflected echo with sound-absorbing metamaterials.

[0032] Figure 3This is a schematic diagram of the sound-absorbing metamaterial unit in this embodiment;

[0033] Figure 4 The reflection phase and reflectivity of the sound-absorbing metamaterial unit under different geometric parameters are shown in (4a) and (4b). The horizontal and vertical axes represent different geometric parameters, and the colors represent the phase shift or reflectivity under different geometric parameters.

[0034] Figure 5 The echo signal at the same location on the aluminum plate with / without sound-absorbing metamaterial;

[0035] Figure 6 The images show the imaging results with / without defects when there is no sound-absorbing metamaterial. (6a) is the imaging result when there is no defect in the sound-absorbing metamaterial, and (6b) is the imaging result when there is defect in the sound-absorbing metamaterial. The white circles in the images represent the size and location of the defects.

[0036] Figure 7 The images show the imaging results with and without defects when there is a sound-absorbing metamaterial. (7a) is the imaging result when there is no defect in the sound-absorbing metamaterial, and (7b) is the imaging result when there is a defect in the sound-absorbing metamaterial. The white circles in the images represent the size and location of the defects. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0038] In recent years, sound-absorbing metamaterials based on local resonance mechanisms have provided a novel technical approach for wavefield manipulation. Through structural design, these metamaterials can absorb, modulate, or delay elastic waves at specific frequencies, achieving precise adjustment of wave propagation paths and energy distribution without altering the matrix structure. Applying these metamaterials to ultrasonic testing allows for effective modification of wavefield characteristics near boundaries without damaging the tested structure, through attachment. Particularly near the operating frequency, local resonance structures can generate significant energy dissipation and phase delay, weakening and delaying the arrival of originally strong boundary reflection waves. This provides a valuable time window for the manifestation of near-boundary defect scattered waves, thereby improving the effectiveness of imaging algorithms.

[0039] Based on the aforementioned advantages, this invention combines sound-absorbing metamaterials with ultrasonic Lamb wave detection, providing a novel, efficient, and engineering-feasible technical solution to address the difficulty in identifying near-boundary defects. By rationally designing the geometric parameters of the sound-absorbing metamaterial unit to operate near the detection frequency, the energy of the boundary reflected wave can be significantly reduced, and a controllable delay can be generated in the wave packet, allowing the defect-scattered wave to "appear" from the boundary reflected wave, thereby improving imaging quality and defect identification capabilities. This concept provides a new technical direction for near-boundary defect detection and imaging, possessing significant theoretical and engineering application value.

[0040] Example 1

[0041] This embodiment provides a method for designing a sound-absorbing metamaterial for near-boundary damage ultrasound imaging detection. The sound-absorbing metamaterial consists of at least one sound-absorbing metamaterial unit, which includes stacked springs and a mass block. (Refer to...) Figure 1 As shown, the design method includes the following steps:

[0042] S1. Obtain the ultrasonic testing frequency, calculate the tensile resonance frequency of the sound-absorbing metamaterial unit using finite element simulation software, and then determine the range of geometric parameters and material parameters of the sound-absorbing metamaterial unit based on the ultrasonic testing frequency. Specifically, the difference between the tensile resonance frequency and the ultrasonic testing frequency is less than a set threshold, that is, the sound-absorbing metamaterial can work near the ultrasonic testing frequency.

[0043] S2. Based on the range of geometric parameters and the range of material parameters, establish a finite element model for ultrasonic Lamb wave detection of near-boundary defects, and use the principle of local resonance to calculate the reflection phase and reflectivity of the sound-absorbing metamaterial unit under different geometric and material parameters;

[0044] S3. Determine the Lamb wave number of the test plate, and determine the number of the sound-absorbing metamaterial units according to the multiple scattering theory, so that the diffraction propagation mode of the sound-absorbing metamaterial only has the 0th order diffraction propagation mode.

[0045] S4. Based on the number of sound-absorbing metamaterial units, the reflection phase and reflectivity of different sound-absorbing metamaterial units, and the uniform distribution requirements of the sound-absorbing metamaterial units, determine the optimal geometric parameters and material parameters of the sound-absorbing metamaterial units.

[0046] The sound-absorbing metamaterial unit is designed based on the principle of local resonance and consists of a spring-mass structure. The spring and mass are stacked cuboids with consistent length and width. In the finite element model for ultrasonic Lamb wave detection of near-boundary defects, the test plate is used as the substrate, and the sound-absorbing metamaterial is mounted at the boundary of the substrate for simulation experiments. Figure 2 The image shows ultrasonic imaging with and without sound-absorbing metamaterials. Figure 2(2a) shows the reflection echo situation without sound-absorbing metamaterial. It can be seen that the energy of the boundary reflection wave generated by the interaction of the excitation signal with the boundary without sound-absorbing metamaterial is much greater than that of the defect reflection wave, and the generation time is similar. Therefore, the defect reflection wave is submerged in the boundary reflection wave, which affects the imaging. Figure 2 (2b) shows the reflected echo when the sound-absorbing metamaterial is present. It can be seen that the excitation signal interacts with the bonded sound-absorbing metamaterial, causing some of the boundary reflected wave energy to be absorbed. At the same time, the boundary reflected wave packet is delayed, making the defect reflected wave more significant, thereby improving the imaging detection sensitivity and accuracy of near-boundary defects. The above results demonstrate the effectiveness of the sound-absorbing metamaterial.

[0047] In step S2, frequency domain analysis is used to study the reflection phase and reflectivity of sound-absorbing metamaterial units with different geometric and material parameters at the detection frequency.

[0048] In step S3, the Lamb wavenumber is calculated based on the frequency-thickness product of the tested plate, and then the number of sound-absorbing metamaterial units is determined based on the multiple scattering theory. Specifically:

[0049] Let the thickness of the test board, i.e., the substrate, be... h p The length and width of the cuboid that acts as both the spring and the mass are respectively... l w and w p The heights are respectively h s and h m The Lamb wavenumber of the substrate is k 0, the number of units constituting the sound-absorbing metamaterial is n To ensure that only one diffraction propagation mode exists in the designed sound-absorbing metamaterial, the following condition must be met:

[0050] ,

[0051] In the formula, roundup means rounding up.

[0052] In step S4, the uniform distribution requirement of the sound-absorbing metamaterial units is specifically determined based on the reflection phase and reflectivity distribution of the sound-absorbing metamaterial units under different geometric and material parameters.

[0053] For example, the reflection phases of multiple sound-absorbing metamaterial units can be uniformly distributed between 0 and 2π based on the reflection phases and reflectivities obtained from simulation calculations. Specifically, based on the determined number of sound-absorbing metamaterial units, the phase gradient of the reflection phases of these units between 0 and 2π is calculated, thus ensuring a uniform distribution of the reflection phases between 0 and 2π. Then, from the reflection phases of the sound-absorbing metamaterial units under previously obtained parameters, the parameters of the units that conform to the calculated phase gradient are selected, and the units are sorted according to the calculated phase gradient to obtain the final sound-absorbing metamaterial, achieving both sound absorption and time delay.

[0054] Specifically, the sound-absorbing metamaterial unit designed in this embodiment is as follows: Figure 3 As shown, it includes a spring 1 and a mass block 2 stacked together. When in use, it is placed at the boundary of the substrate 3 (i.e. the test plate), with the spring 1 close to the substrate 3. Figure 3 middle, h p For substrate thickness, w p For unit width, l w For unit length, h s To serve as the thickness of the spring material, h m The thickness of the material serving as the mass block.

[0055] In this example, the center frequency of the excitation signal is 30 kHz. h p =2 mm, w p =2 mm, l w =10 mm, h s The range is 1-2.4 mm. h m The range is 1-6.4 mm. The substrate material is aluminum, the spring material is polyurethane, and the mass block material is aluminum alloy. Polyurethane is commonly used as a vibration damping material and has a certain loss, which helps to absorb ultrasonic Lamb waves. At the same time, both of these materials are easy to obtain and easy to process.

[0056] The reflection phase and reflectivity of the sound-absorbing metamaterial element with different geometric parameters were calculated using finite element simulation software, as shown below. Figure 4 As shown. From Figure 4It can be observed that the designed sound-absorbing metamaterial unit can achieve a reflection phase shift of 0-2π under different geometric parameters, with a reflectivity between 0.6 and 0.8. Based on multiple scattering theory, it can be calculated that when the number of metamaterial units is 6, the diffraction propagation mode of the sound-absorbing metamaterial can only have the 0th order mode. In order to make the reflection phase of these metamaterial units uniformly distributed between 0-2π, its phase gradient is calculated to be π / 3. To satisfy this phase gradient, from Figure 4 In the reflection phase diagram of (4a), a reflection phase sequence that satisfies this requirement can be obtained, such as 35π / 18, 29π / 18, 23π / 18, 17π / 18, 11π / 18, and 5π / 18. These sequences are not unique; as long as they satisfy a phase gradient of π / 3, they are acceptable. Based on the example reflection phases, the corresponding geometric parameters can be obtained from the diagram for the 6 elements. h s The thicknesses are 1 mm, 1 mm, 1 mm, 1.5 mm, 1.5 mm, and 2 mm, respectively. h m The thicknesses are 1 mm, 2.4 mm, 4.2 mm, 2.4 mm, 5.8 mm, and 7 mm, respectively.

[0057] In this embodiment, the designed sound-absorbing metamaterial has a width on the same order of magnitude as the wavelength, a small volume, and is easy to use.

[0058] In other implementations, the tensile resonance frequency of the metamaterial unit can be changed by adjusting its geometric parameters and material properties, so that its tensile resonance frequency is close to the ultrasonic Lamb wave detection frequency, thereby meeting different application requirements.

[0059] If the above methods are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0060] Example 2

[0061] This embodiment introduces the sound-absorbing metamaterial designed in Embodiment 1 into ultrasonic Lamb wave imaging detection of near-boundary defects, proposing a method for ultrasonic imaging detection of near-boundary damage. Finite element models for ultrasonic Lamb wave detection of near-boundary defects are constructed under four different conditions, simulating 8-element transceiver scenarios with and without sound-absorbing metamaterial, with and without sound-absorbing metamaterial, with and without sound-absorbing metamaterial, and with and without sound-absorbing metamaterial, respectively, to verify that the sound-absorbing metamaterial can improve the detection sensitivity and accuracy of near-boundary defects. In this embodiment, time-domain analysis is used to study the diffraction propagation process of the excitation signal after passing through the sound-absorbing metamaterial, and the received signal is directly used for imaging.

[0062] In this embodiment, the substrate size is set to 1 m × 0.2 m × 0.002 m, the defect radius is set to 0.006 m, and the distance from the defect center to the boundary is set to 0.03 m. In each case, a 3-cycle Hanning window modulated sinusoidal pulse signal is excited at (0.4749,0) m, (0.48745,0) m, (0.5,0) m, (0.51255,0) m, (0.5251,0) m, (0.53765,0) m, (0.5502,0) m, and (0.56275,0) m, with a center frequency of 30 kHz. The signal is received at these 8 array element positions, so that there are 64 sets of signals in each case.

[0063] Figure 5 The graph shows a comparison of the signals received at (0.48745,0) m when excited at (0.4749,0) m with and without metamaterials, with and without defects. The solid line in the graph represents the received signal when there are no defects and no metamaterials, and the dashed line represents the received signal when there are no defects and with metamaterials. The first wave packet is the direct wave of the excitation signal reaching the receiving point, and the second wave packet is the reflected wave of the excitation signal incident on the structural boundary or metamaterial. It can be seen from the graph that the amplitude of the boundary reflected wave signal is significantly reduced and there is a certain time delay.

[0064] The Total Focusing Method (TFM) algorithm was used to image the signals obtained in these four cases. First, the imaging results of the cases with and without defects and without metamaterial were compared. Then, the imaging results of the cases with and without defects and with metamaterial were compared. Finally, the imaging results of the cases with defects and without metamaterial were compared.

[0065] like Figure 6 and Figure 7 As shown, Figure 6 (6a) shows the imaging results under the condition of no metamaterial and no defects. It can be seen that the energy of the boundary reflected wave is dominant and the energy is focused at the bottom boundary. Figure 6(6b) shows the imaging results under the condition of defects without metamaterials. The white circles represent the true size and location of the defects. As can be seen from the figure, without metamaterials, the defect reflection wave is submerged by the boundary reflection wave, and the energy of the boundary reflection wave is much greater than that of the defect reflection wave, so the energy is still focused at the bottom boundary, and the defects near the boundary cannot be effectively imaged.

[0066] Figure 7 (7a) shows the imaging results under the condition of defect-free metamaterials, compared with... Figure 6 Compared to (6a), the area of ​​the light spot caused by boundary reflection waves is significantly reduced; Figure 7 (7b) shows the imaging results under the condition of defects in metamaterials, compared with... Figure 7 Compared to (7a), a light spot appeared at the white circle, effectively imaging the defect near the boundary. Although the focusing energy was not higher than that caused by the boundary reflection wave, it still proved that the sound-absorbing metamaterial significantly reduced the energy of the boundary reflection wave and delayed its wave packet, thus making the defect reflection wave stand out. And compared to... Figure 6 Compared to (6b), Figure 7 The imaging results of (7b) further demonstrate that the proposed sound-absorbing metamaterial can improve the detection sensitivity and accuracy of near-boundary defects.

[0067] This invention proposes an attached sound-absorbing metamaterial based on the principle of local resonance and multiple scattering theory. It aims to achieve the manipulation of elastic waves using a simple structure, effectively reducing the energy of boundary reflected waves in ultrasonic testing and inducing a time delay. This allows for effective separation of boundary reflected waves from near-boundary defect scattered waves, improving the detection sensitivity and imaging accuracy of near-boundary defects. This method provides an efficient technical means for near-boundary defect imaging detection and has significant application prospects.

[0068] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for acoustic metamaterial design for near-boundary damage ultrasound imaging detection, characterized in that, The sound absorption metamaterial is composed of at least one sound absorption metamaterial unit, the sound absorption metamaterial unit comprises a spring and a mass block arranged in a stack, the design method comprises: An ultrasonic detection frequency is obtained, a tensile resonance frequency of the sound absorption metamaterial unit is calculated by using finite element simulation software, and then a geometric parameter range and a material parameter range of the sound absorption metamaterial unit are determined according to the ultrasonic detection frequency; Based on the geometric parameter range and the material parameter range, a near-boundary defect ultrasonic Lamb wave detection finite element model is established, and the reflection phase and the reflectivity of the sound absorption metamaterial unit under different geometric parameters and material parameters are calculated; The Lamb wave number of the measured plate is determined, the number of the sound absorption metamaterial units is determined according to the multiple scattering theory, so that the diffraction propagation mode of the sound absorption metamaterial only exists in the 0th diffraction propagation mode; Based on the number of the sound absorption metamaterial units, the reflection phase and the reflectivity of different sound absorption metamaterial units, and the uniform distribution requirement of the sound absorption metamaterial units, the optimal geometric parameters and material parameters of the sound absorption metamaterial units are determined.

2. The acoustic metamaterial design method for near-boundary lesion ultrasound imaging detection of claim 1, wherein, The difference between the tensile resonance frequency and the ultrasonic detection frequency is less than a set threshold value.

3. The acoustic metamaterial design method for near-boundary lesion ultrasound imaging detection of claim 1, wherein, The Lamb wave number is calculated according to the frequency-thickness product of the measured plate.

4. The acoustic metamaterial design method for near-boundary lesion ultrasound imaging detection of claim 1, wherein, The structure of the spring and the mass block is a cuboid with consistent length and width, and the geometric parameters include the length, width and height of the spring and the length, width and height of the mass block.

5. The acoustic metamaterial design method for near-boundary lesion ultrasound imaging detection of claim 1, wherein, The material of the spring comprises polyurethane. The material of the mass block comprises aluminum.

6. The acoustic metamaterial design method for near-boundary lesion ultrasound imaging detection of claim 4, wherein, The condition formula corresponding to the condition that the diffraction propagation mode of the sound absorption metamaterial only exists in the 0th diffraction propagation mode is represented as: wherein, roundup denotes rounding up, n N is the number of sound-absorbing metamaterial units, w p W is the width of the spring and mass, k 0 is the Lamb wave number of the measured plate.

7. The method of claim 1, wherein, When the near-boundary defect ultrasonic Lamb wave detection finite element model is established, the measured plate is taken as a substrate, and the sound absorption metamaterial is installed at the boundary of the substrate.

8. An acoustic metamaterial for near-boundary lesion ultrasound imaging detection, characterized in that, The sound absorption metamaterial is designed by using the design method of any one of claims 1-7.

9. A near-boundary lesion ultrasound imaging detection method, characterized in that, The method comprises the following steps: The sound absorption metamaterial designed by using the design method of any one of claims 1-7 is installed at the boundary of the measured plate. An excitation signal with an ultrasonic detection frequency is incident on the measured plate, and a reflected wave signal is collected. The reflected wave signal is processed and imaged by using a full-focus imaging algorithm, and defect detection is realized according to the imaging result.

10. The near-boundary damage ultrasonic imaging detection method of claim 9, wherein, The sound absorption metamaterial is installed at the boundary of the measured plate by means of adhesive attachment.

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