Method and device for extracting wave packet of dispersive Lamb wave response under single-mode condition

Abstract

The present invention discloses a method and device for extracting a dispersive Lamb wave response wave packet under a single-mode condition. In the field of structural health monitoring, a dispersive Lamb wave is usually used as a detection medium. Under low-frequency thick accumulation conditions, the excitation frequency parameters are controlled so that the excited response signal is single-mode. With the help of the constructed dispersive reference wave packet, the wave packet in the single-mode Lamb wave response signal is extracted, and a narrower Gaussian pulse is constructed at the original time axis of the extracted wave packet for reconstruction, thereby eliminating dispersion and wave packet aliasing, thereby improving the accuracy and stability of damage imaging monitoring.

Description

Technical Field

[0001] The present invention belongs to the technical field of Lamb wave response signal processing, and specifically relates to a method and device for extracting a dispersion Lamb wave response wave packet under a single mode condition, which is a method for extracting and reconstructing a dispersion Lamb wave response wave packet under a single mode condition. Background Art

[0002] Lamb waves are commonly used monitoring signals in the field of structural health monitoring. They are very sensitive to tiny damage on the surface of the structure and can propagate over long distances. However, the dispersion effect of Lamb waves is inevitable and significant during propagation. Moreover, as the dispersion effect intensifies, aliasing of wave packets may even occur, which leads to a serious decrease in the resolution and signal-to-noise ratio of the response signal, affecting the accuracy and stability of the detection.

[0003] Under low-frequency dispersion conditions, even if the propagation of Lamb waves is relatively controllable, there are still two modes of response signals, S0 and A0. And the dispersion of the A0 mode signal is greater than that of the S0 mode signal. Therefore, it is necessary to propose a solution that can suppress the A0 mode signal when exciting the response signal, so that the S0 mode signal is the main part of the response signal. And through signal processing, the S0 mode signal can be targeted for feature extraction, and finally a narrow pulse can be used to reconstruct the response signal. In this way, the dispersion problem of the original response signal can be solved. Summary of the invention

[0004] In order to achieve the above objectives, the technical solutions adopted are:

[0005] In a first aspect, a method for extracting a dispersive Lamb wave response wave packet under a single-mode condition is provided, comprising:

[0006] Obtain a single-mode Lamb wave response signal v(t); wherein the Lamb wave response signal is a narrow-band excitation signal v loaded on the exciter a (t), and collected on the sensor, the exciter and the sensor are installed on the plate structure object, and the distance between the exciter and the sensor is greater than the length of a single pulse of the excitation signal;

[0007] The constructed reference signal I(t) is obtained according to the excitation signal, and the wave packet of the response signal is decomposed using the reference signal:

[0008] The structural response signal and the reference signal are correlated in the time domain, and the time corresponding to the peak value of each wave packet in the response signal is obtained according to the correlation processing result, that is, the wave packet shift delay factor τ i ; Shift the wave packet by a delay factor τ iSubstitute the dispersion equation of the corresponding mode to obtain the reference wave packet I(t-τ i ), and calculate the amplitude coefficient a of the wave packet at this time point based on the correlation operation i ; According to τ i and a i The response signal is decomposed by wave packet to obtain the response wave packet (τ i ,a i ) and the residual signal e after the i-th decomposition i (t), repeat this process until the peak value of the residual signal is less than the set threshold, completing the decomposition of the response signal;

[0009] According to the decomposed response wave packet (τ i ,a i ), the original response signal is reconstructed using a narrow pulse, and the reconstructed response signal is Σa i ×v l (t-τ i ), where v l (t-τ i ) represents the narrow pulse constructed at the original time position of the response wave packet decomposed for the i-th time.

[0010] In some embodiments, a method for acquiring a single-mode Lamb wave response signal v(t) includes:

[0011] For a plate structure object, a coordinate system is established with the center of the plate as the origin, and at least two piezoelectric transducers are attached to the structure as actuators or sensors, and the spacing between any adjacent piezoelectric transducers is greater than the length of a single pulse of the excitation signal;

[0012] Select one of the piezoelectric transducers as the exciter and the other piezoelectric transducers as sensors; load a narrowband excitation signal v on the exciter. a (t), and collect the response signal on the sensor; under the condition of low-frequency thick accumulation, the exciter excites the excitation signal at a set excitation frequency to obtain a single-mode Lamb wave response signal collected on the sensor.

[0013] In some embodiments, the exciter excites an excitation signal at a set excitation frequency to obtain a single-mode Lamb wave response signal collected on the sensor, including:

[0014] The center frequency of the excitation signal starts from 5KHz and increases in steps of 5KHz until it reaches 200KHz; the amplitude of the S0 mode and A0 mode response signal wave packets is recorded as the frequency increases; at the same time, the amplitude ratio of the S0 mode signal wave packet to the A0 mode signal wave packet is recorded as the frequency increases; among them, the S0 mode signal wave packet is the first wave, and the A0 mode signal wave packet is the last wave; the center frequency corresponding to the maximum point of the amplitude ratio of the S0 mode signal wave packet to the A0 mode signal wave packet is selected, and this center frequency is the optimal frequency for exciting the single mode response signal.

[0015] In some embodiments, the excitation signal v a (t) is expressed as:

[0016]

[0017] Where: Heaviside is a step signal; t is a time variable; N is the number of cycles, f c is the center frequency of the signal, and A is the signal amplitude.

[0018] In some embodiments, decomposing the wave packet of the response signal using the reference signal includes:

[0019] The reference signal I(t) is initially constructed as an excitation signal with an amplitude of 1;

[0020] Calculate the reference signal I(t) and e i-1 (t), find the time corresponding to the maximum absolute value of the correlation function, that is, the wave packet shift delay factor τ i ;

[0021] The reference signal I(t) is subjected to a fast Fourier transform operation to obtain the spectrum function expression I(f) of the reference signal, and the wave packet is shifted by the delay factor τ i Substitute the dispersion equation of the corresponding mode and perform equidistant interpolation on the wave number k to obtain the new spectrum function I τi (f); for the new spectrum function I τi (f) Perform inverse fast Fourier transform to obtain the reference wave packet I(t-τ i );

[0022] Calculate e i-1 (t) and the reference wave packet I(t-τ i ), take the maximum absolute value of the correlation function, and find I(t-τ i ) and the maximum absolute value of the autocorrelation function. The two are divided to obtain the amplitude adjustment coefficient a. i :

[0023] The reference wave packet I(t-τi ) is adjusted to a i , and obtain the adjusted reference wave packet a i ×I(t-τ i ); e i-1 (t) and the adjusted reference wave packet a i ×I(t-τ i ) to obtain the response wave packet (τ i ,a i ) and the residual signal e after the i-th decomposition i (t):

[0024] e i (t) = e i-1 (t)-a i ×I(t-τ i )

[0025] Among them, e0(t)=v(t), e i (t) is the residual signal after the i-th decomposition,

[0026] Completes one iteration of signal decomposition.

[0027] Furthermore, in some embodiments, the wave packet shift delay factor τ i The calculation methods include:

[0028]

[0029] In the formula, <·> represents the correlation operation; where i is a positive integer, i is the number of decompositions, e0(t) = v(t), e i-1 (t) is the residual signal after the i-1th decomposition, and I(t) is the constructed reference signal.

[0030] In some embodiments, the reference wave packet I(t-τ i ) include:

[0031]

[0032]

[0033] Where j represents the imaginary unit; f(k) is the inverse function of the relationship between frequency f and wave number k, k(f); k(f) = f / C p (f), C p (f) is the phase velocity of a single mode.

[0034] In some embodiments, the adjustment factor a i The calculation methods include:

[0035]

[0036] In the formula, <·> represents a correlation operation.

[0037] In some embodiments, the residual signal e i The calculation methods of (t) include:

[0038] e i (t) = e i-1 (t)-a i ×I(t-τ i ).

[0039] The first signal decomposition is the initial response signal v(t), and the signal decomposition after the first decomposition is the residual signal e after the previous decomposition i-1 (t).

[0040] In some embodiments, the narrow pulse is constructed using a unit Gaussian function, and the pulse width of the narrow pulse is ≤ 1 / 2 of the pulse width of the excitation signal.

[0041] In a second aspect, a dispersion Lamb wave extraction device under single-mode conditions is provided, including a processor and a storage medium;

[0042] The storage medium is used to store instructions;

[0043] The processor is configured to operate according to the instructions to execute the steps according to the method.

[0044] In a third aspect, the present invention provides a storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the method described in the first aspect.

[0045] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects: under the condition of low-frequency thick accumulation, the excitation frequency parameters can be controlled to make the excited response signal single-mode. With the help of the constructed dispersion reference wave packet, the wave packet in the response signal is extracted, and a narrower Gaussian pulse is constructed at the original time axis of the extracted wave packet to reconstruct, thereby eliminating dispersion and wave packet aliasing, thereby improving the accuracy and stability of damage imaging monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is the arrangement of the excitation points and receiving points of the present invention.

[0047] Figure 2 It is a time domain diagram of the excitation signal of the present invention.

[0048] Figure 3 is the original response signal

[0049] Figure 4 is the contour of the original response signal

[0050] Figure 5 It is to align the constructed reference signal with the wave packet of the original response signal

[0051] Figure 6 is the residual signal obtained after decomposition once

[0052] Figure 7 is the decomposed wave packet

[0053] Figure 8 The wave packet is reconstructed at the original time of the decomposed wave packet.

[0054] Fig. 9 The original response signal diagram of the example

[0055] Fig.10 The original response signal contour diagram of the example

[0056] Fig.11 Shows the wave packets decomposed from the original response signal

[0057] Fig.12 Shows the reconstructed wave packet summation Specific implementation methods

[0058] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0059] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0060] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0061] Example 1

[0062] In a first aspect, a method for extracting a dispersive Lamb wave response wave packet under a single-mode condition comprises:

[0063] Obtain a single-mode Lamb wave response signal v(t); wherein the Lamb wave response signal is a narrow-band excitation signal v loaded on the exciter a (t), and collected on the sensor, the exciter and the sensor are installed on the plate structure object, and the distance between the exciter and the sensor is greater than the length of a single pulse of the excitation signal;

[0064] The constructed reference signal I(t) is obtained according to the excitation signal, and the wave packet of the response signal is decomposed using the reference signal:

[0065] The structural response signal and the reference signal are correlated in the time domain, and the time corresponding to the peak value of each wave packet in the response signal is obtained according to the correlation processing result, that is, the wave packet shift delay factor τ i ; Shift the wave packet by a delay factor τ i Substitute the dispersion equation of the corresponding mode to obtain the reference wave packet I(t-τ i ), and calculate the amplitude coefficient a of the wave packet at this time point based on the correlation operation i ; According to τ i and a i The response signal is decomposed by wave packet to obtain the response wave packet (τ i ,a i ) and the residual signal e after the i-th decomposition i (t), repeat this process until the peak value of the residual signal is less than the set threshold, completing the decomposition of the response signal;

[0066] According to the decomposed response wave packet (τ i ,a i ), the original response signal is reconstructed using a narrow pulse, and the reconstructed response signal is Σa i ×v l (t-τ i ), where v l (t-τ i ) represents the narrow pulse constructed at the original time position of the response wave packet decomposed for the i-th time.

[0067] In some specific embodiments, a method for extracting a dispersive Lamb wave response wave packet under a single-mode condition comprises the following steps:

[0068] Step 1: In this experiment, a thin aluminum plate is selected as the research object. The size of the aluminum plate is 1000mm×1000mm×3mm. With the center of the plate as the origin, a coordinate system is established. Piezoelectric transducers are pasted on the structure as exciters and sensors. The distance between the two is greater than the length of a single pulse of the excitation signal. The coordinates of transducer 1 are (0,250), the coordinates of transducer 2 are (0,-250), the coordinates of transducer 3 are (-250,0), and the coordinates of transducer 4 are (250,0). Figure 1 .

[0069] Step 2: Select one of the piezoelectric transducers as the excitation point and the other piezoelectric transducers as the response sensors. Load the narrowband excitation signal v on the exciter. a (t), and collect the response signal on the sensor. Under the condition of low-frequency thick accumulation, select excitation signals of various frequencies, and the selected excitation frequency is to stimulate the response signal dominated by the S0 mode without serious dispersion.

[0070] In this embodiment, under the condition of low frequency and thick accumulation, the exciter excites the excitation signal at a set excitation frequency to obtain a single-mode Lamb wave response signal collected on the sensor, including:

[0071] The center frequency of the excitation signal starts from 5KHz and increases in steps of 5KHz until it reaches 200KHz; the amplitude of the S0 mode and A0 mode response signal wave packets is recorded as the frequency increases; at the same time, the amplitude ratio of the S0 mode signal wave packet to the A0 mode signal wave packet is recorded as the frequency increases; among them, the S0 mode signal wave packet is the first wave, and the A0 mode signal wave packet is the last wave; the center frequency corresponding to the maximum point of the amplitude ratio of the S0 mode signal wave packet to the A0 mode signal wave packet is selected, and this center frequency is the optimal frequency for exciting the single mode response signal.

[0072] In some embodiments, the condition of low frequency thickness product is that the frequency thickness product is less than or equal to 2 MHz·mm, the signal frequency is less than or equal to 500 KHz, and the structure thickness is less than or equal to 5 mm.

[0073] The excitation signal expression of this experiment is as follows, and the signal waveform is as follows Figure 2 .

[0074]

[0075] in:

[0076] Heaviside is a step signal

[0077] N is the number of cycles, and in this paper N is 5.

[0078] f cis the center frequency of the signal, and in this article the center frequency is taken as 125KHz.

[0079] A is the signal amplitude, which is taken as 5 in this paper.

[0080] Step 3: Decomposition of response signal wave packets. Construct a unit reference signal I(t) based on the excitation signal. Perform time domain correlation operation on the structural response signal and the reference signal, and calculate the time corresponding to the peak value of each wave packet in the response signal based on the correlation processing results, that is, the wave packet shift delay factor τ i . Shift the wave packet by the delay factor τ i Substitute the dispersion equation of the corresponding mode to obtain the reference wave packet I(t-τ i ), and calculate the amplitude coefficient a of the wave packet at that moment based on the correlation operation i . Let e0(t) = v(t), e i (t) is the residual signal after the i-th decomposition, and the response signal is decomposed by wave packet using the following formula:

[0081] e i (t) = e i-1 (t)-a i ×I(t-τ i )

[0082] Step 4: According to the decomposed response wave packet (τ i ,a i ), using narrow pulse v l (t) Reconstruct the original response signal, and the reconstructed response is Σa i ×v li (t-τ i ).

[0083] As a preferred solution of the present invention, the specific process of step 3 is:

[0084] Step 31: Obtain dispersion curve data. The dispersion curve describes the relationship between the frequency-thickness product (the product of signal frequency and thickness), phase velocity, and group velocity. The structural parameters are constant and the dispersion curve is constant. The curve is approximated under the condition of low frequency-thickness product (frequency-thickness product is less than or equal to 2MHz·mm, signal frequency is less than or equal to 500KHz, and structure thickness is less than or equal to 5mm). Because the current structure thickness is constant, only the frequency f is used as the independent variable. Calculate the relationship between frequency f and single mode phase velocity C p (f) is a polynomial curve. According to the wave number calculation formula k(f) = f / C p (f) Find the relationship k(f) between frequency f and wave number k; find its inverse function f(k).

[0085] Step 32: construct a reference signal. The initial construction method of the reference signal I(t) is an excitation signal with an amplitude of 1; calculate the reference signal I(t) and e i-1 (t), find the time corresponding to the maximum absolute value of the correlation function, that is, the wave packet shift delay factor τ i ;

[0086]

[0087] In the formula, <·> represents the related operation; i is a positive integer, i is the number of decompositions;

[0088] Step 33: Perform FFT operation on the reference signal I(t) to obtain the reference signal spectrum function expression I(f), and then shift the wave packet obtained in step 32 by the delay factor τ i Substitute the following formula and perform equidistant interpolation on the wave number k to obtain the new spectrum function I τi (f); Finally, perform IFFT operation to obtain the time-shifted wave packet I(t-τ i ), where j represents the imaginary unit.

[0089]

[0090]

[0091] Step 34: Calculate the dispersion wave packet I(t-τ i ) and calculate e as follows i-1 (t) and I(t-τ i ), take the maximum absolute value of the correlation function, and find I(t-τ i )'s autocorrelation function, and also take its maximum absolute value, and divide the two to get the amplitude adjustment coefficient a i .

[0092]

[0093] Step 35: Calculate the amplitude adjustment coefficient as a i Then, the dispersion wave packet is amplitude modulated, as Figure 5 After amplitude modulation, the original response signal is used to perform a subtraction, completing a signal decomposition iteration to obtain the residual signal e i (t), such as Figure 6 .

[0094] e i (t) = e i-1 (t)-a i ×I(t-τ i )

[0095] Step 36: Reconstruct the original decomposed time point with a new narrower wave packet. One signal decomposition iteration is completed. Figure 7 and Figure 8 .

[0096] Step 37: When e i When (t) is small enough, that is, the energy of the residual signal is very small, it can be considered that the key signal wave packets have been separated, and the residual signal will not affect the decomposed signal wave packets. At this time, the decomposition is stopped. In the present invention, it is assumed that there is only one mode in the response signal and no serious dispersion occurs. Therefore, the above steps are repeated until the peak value of the residual signal is less than a threshold. In this experiment, the threshold is selected as a1 / 4.

[0097] As a preferred solution of the present invention, the narrow pulse v in step 4 l (t) is constructed using a unit Gaussian function, whose pulse width is ≤ 1 / 2 of the excitation signal pulse width. In this experiment, a Gaussian pulse with a pulse width equal to the original excitation signal pulse width is constructed for reconstruction.

[0098] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0099] The above embodiments are only for illustrating the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

[0100] Next, an example of signal processing is used to illustrate the advantages of the present invention. Fig. 9 is the response signal collected during the test, such as Fig.10 is the contour diagram of the response signal, such as Fig.11 This is the distribution diagram of the decomposed wave packet on the time axis, such as Fig.12 As shown in the figure, only the S0 mode is dominant in the original response signal, and its dispersion effect is not serious. The response wave packet can be extracted relatively well by using this technology, and there is no aliasing phenomenon between the wave packets after reconstruction.

[0101] Example 2

[0102] In a second aspect, the present embodiment provides a dispersion Lamb wave extraction device under single-mode conditions, including a processor and a storage medium;

[0103] The storage medium is used to store instructions;

[0104] The processor is used to operate according to the instructions to execute the steps of the method according to embodiment 1.

[0105] Example 3

[0106] In a third aspect, this embodiment provides a storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described in Example 1 are implemented.

[0107] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0108] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0109] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0110] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0111] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for extracting dispersive Lamb wave response packets under single-mode conditions, characterized in that: include: Obtain a single-mode Lamb wave response signal v(t); wherein the Lamb wave response signal is a narrow-band excitation signal v loaded on the exciter a (t), and collected on the sensor, the exciter and the sensor are installed on the plate structure object, and the distance between the exciter and the sensor is greater than the length of a single pulse of the excitation signal; The constructed reference signal I(t) is obtained according to the excitation signal, and the wave packet of the response signal is decomposed using the reference signal: The structural response signal and the reference signal are correlated in the time domain, and the time corresponding to the peak value of each wave packet in the response signal is obtained according to the correlation processing result, that is, the wave packet shift delay factor τ i ; Shift the wave packet by a delay factor τ i Substitute the dispersion equation of the corresponding mode to obtain the reference wave packet I(t-τ i ), and calculate the amplitude coefficient a of the wave packet at this time point based on the correlation operation i ; According to τ i and a i The response signal is decomposed by wave packet to obtain the response wave packet (τ i ,a i ) and the residual signal e after the i-th decomposition i (t), repeat this process until the peak value of the residual signal is less than the set threshold, completing the decomposition of the response signal; According to the decomposed response wave packet (τ i ,a i ), the original response signal is reconstructed using a narrow pulse, and the reconstructed response signal is Σa i ×v l (t-τ i ), where v l (t-τ i ) represents the narrow pulse constructed at the original time position of the response wave packet decomposed for the i-th time.

2. The method for extracting dispersed Lamb waves under single-mode conditions according to claim 1, characterized in that: The method for obtaining the single-mode Lamb wave response signal v(t) includes: For a plate structure object, a coordinate system is established with the center of the plate as the origin, and at least two piezoelectric transducers are attached to the structure as actuators or sensors, and the spacing between any adjacent piezoelectric transducers is greater than the length of a single pulse of the excitation signal; Select one of the piezoelectric transducers as the exciter and the other piezoelectric transducers as sensors; load a narrowband excitation signal v on the exciter. a (t), and collect the response signal on the sensor; under the condition of low-frequency thick accumulation, the exciter excites the excitation signal at a set excitation frequency to obtain a single-mode Lamb wave response signal collected on the sensor.

3. The method for extracting dispersive Lamb waves under single-mode conditions according to claim 1, characterized in that: Excitation signal v a (t) is expressed as: Where: Heaviside is a step signal; t is a time variable; N is the number of cycles, f c is the center frequency of the signal, and A is the signal amplitude.

4. The method for extracting dispersed Lamb waves under single-mode conditions according to claim 1, characterized in that: The wave packet of the response signal is decomposed using the reference signal, including: The reference signal I(t) is initially constructed as an excitation signal with an amplitude of 1; Calculate the reference signal I(t) and e i-1 (t), find the time corresponding to the maximum absolute value of the correlation function, that is, the wave packet shift delay factor τ i ; The reference signal I(t) is subjected to a fast Fourier transform operation to obtain the spectrum function expression I(f) of the reference signal, and the wave packet is shifted by the delay factor τ i Substitute the dispersion equation of the corresponding mode and perform equidistant interpolation on the wave number k to obtain a new spectrum function For the new spectral function Perform inverse fast Fourier transform operation to obtain the reference wave packet I(t-τ i ); Calculate e i-1 (t) and the reference wave packet I(t-τ i ), take the maximum absolute value of the correlation function, and find I(t-τ i ) and the maximum absolute value of the autocorrelation function. The two are divided to obtain the amplitude adjustment coefficient a. i : The reference wave packet I(t-τ i ) is adjusted to a i , and obtain the adjusted reference wave packet a i ×I(t-τ i ); i-1 (t) and the adjusted reference wave packet a i ×I(t-τ i ) to obtain the response wave packet (τ i ,a i ) and the residual signal e after the i-th decomposition i (t): e i (t)=e i-1 (t)-a i ×I(t-τ i ) Among them, e0(t)=v(t), e i (t) is the residual signal after the i-th decomposition, Completes one signal decomposition iteration.

5. The method for extracting dispersive Lamb waves under single-mode conditions according to claim 1, characterized in that: Wave packet shift delay factor τ i The calculation methods include: In the formula, <·> represents the correlation operation; where i is a positive integer, i is the number of decompositions, e0(t) = v(t), e i-1 (t) is the residual signal after the i-1th decomposition, and I(t) is the constructed reference signal.

6. The method for extracting dispersed Lamb waves under single-mode conditions according to claim 1, characterized in that: Reference wave packet I(t-τ i ) include: Where j represents the imaginary unit; f(k) is the inverse function of the relationship between frequency f and wave number k, k(f); k(f) = f / C p (f), C p (f) is the phase velocity of a single mode.

7. The method for extracting dispersive Lamb waves under single-mode conditions according to claim 1, characterized in that: Adjustment factor a i The calculation methods include: In the formula, <·> represents a correlation operation.

8. The method for extracting dispersed Lamb waves under single-mode conditions according to claim 1, characterized in that: Residual signal e i The calculation method of (t) includes: e i (t)=e i-1 (t)-a i ×I(t-τ i )。 9. The method for extracting dispersive Lamb waves under single-mode conditions according to claim 1, characterized in that: The narrow pulse is constructed by using a unit Gaussian function, and the pulse width of the narrow pulse is ≤ 1 / 2 of the pulse width of the excitation signal.

10. A dispersion Lamb wave extraction device under single mode condition, characterized in that: including processor and storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 9.

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