Guided wave phase velocity frequency dispersion reconstruction method based on spectral decomposition and phase spectrum enhancement

Abstract

The invention discloses a guided wave phase velocity frequency dispersion reconstruction method based on spectral decomposition and phase spectrum enhancement. The method comprises the following steps: measuring adjacent guided wave signals at two non-overlapping positions by using an oscilloscope; performing spectral decomposition on the guided wave signal to obtain a set number of filtered guided wave signal components; performing phase spectrum expansion processing on the guided wave signal components by using a phase spectrum enhancement technology to obtain a phase difference between the guided wave signals; and reconstructing the phase velocity and frequency of the guided wave mode to obtain a reconstructed frequency dispersion curve. Parameters representing the mechanical properties of the composite material are obtained, wherein the parameters comprise the layering direction, the elastic matrix and the material density; establishing a theoretical model of the propagation of the Lamb waves in the composite material plate by using a semi-analytical finite element method, and obtaining a theoretical frequency dispersion curve of the propagation of the Lamb waves in the composite material plate; and comparing the reconstructed frequency dispersion curve with the theoretical frequency dispersion curve to verify the effectiveness of the method. Certain support is provided for analysis and research of non-stationary guided wave signals.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic guided wave signal processing and ultrasonic guided wave nondestructive testing technology, and in particular to a guided wave phase velocity dispersion reconstruction method based on spectrum decomposition and phase spectrum enhancement. Background Art

[0002] Lamb waves have been widely used in nondestructive testing and structural health monitoring to locate and quantitatively detect structural damage of various objects. However, Lamb waves have special propagation characteristics, such as dispersion, multimodality, mode interleaving, and mode splitting caused by edges, which make the Lamb wave reception signal often very complex. Dispersion can be called one of the main characteristics of Lamb waves, which increases the difficulty of wave signal analysis and processing.

[0003] The Lamb wave signal packet consists of components of different frequencies propagating at different speeds, which are characterized by phase velocity and group velocity described by the dispersion curve. In general, dispersion affects the duration of signal extension and reduces the signal amplitude according to the distance. For Lamb waves used in applications, signal processing techniques that can evaluate dispersion phenomena and relate frequency to phase velocity and group velocity should be used. Most of the existing dispersion reconstruction methods require the arrangement of multiple sensor arrays to collect signals simultaneously, and then the dispersion reconstruction of Lamb waves is realized through spectrum analysis. This method is costly and complex to arrange, especially in large or irregular structures, where it is difficult to arrange and difficult to achieve efficient measurement. At the same time, the amount of calculation is large and the requirements for signal processing algorithms are high. To achieve broadband reconstruction of dispersion curves, it is often necessary to change the excitation signal for multiple excitations, which is cumbersome, complex, time-consuming and labor-intensive. Therefore, an improved method is urgently needed to improve the accuracy, bandwidth, efficiency and applicability of dispersion curve reconstruction so that it can be better applied to actual engineering detection. Summary of the invention

[0004] The purpose of the present invention is to provide a method for reconstructing the dispersion of guided wave phase velocity based on spectrum decomposition and phase spectrum enhancement. After improving the sensitivity of small-amplitude components by spectrum decomposition, the phase shift between signals is estimated, and the phase velocity is reconstructed on a specific frequency component corresponding to the peak of the amplitude spectrum, thereby realizing broadband reconstruction of the dispersion curve.

[0005] The present invention adopts the following technical solution:

[0006] A guided wave phase velocity dispersion reconstruction method based on spectrum decomposition and phase spectrum enhancement comprises the following steps:

[0007] S1. Use an oscilloscope to measure the adjacent waveguide signals u at two non-overlapping positions x1 and x2 at time t. x1 (t) and u x2 (t).

[0008] S2. Perform spectrum decomposition on the signal obtained in step S1 to obtain a set number of filtered waveguide signal components.

[0009] S3. Using phase spectrum enhancement technology, perform phase spectrum expansion processing on the signal components in step S2 to obtain the phase difference between the waveguide signals.

[0010] S4. Reconstruct the phase velocity and frequency of the guided wave mode to obtain the reconstructed dispersion curve.

[0011] Further, in step S2, obtaining the waveguide signal component includes the following contents:

[0012] S201, calculate the spectrum of the signal, the specific formula is:

[0013] U x1 (f) = FT[u x1 (t)]

[0014] U x2 (f) = FT[u x2 (t)]

[0015] Among them, U x1 (f) represents u x1 The spectrum of (t), U x2 (f) represents u x2 FT stands for Fourier transform and f stands for frequency.

[0016] S202, filtering the spectrum obtained in step S201, the specific formula is:

[0017] U x1,i (f) = U x1 (f) B i (f)

[0018] U x2,i (f) = U x2 (f) B i (f)

[0019] Among them, U x1,i (f) represents U after filtering by the i-th Gaussian filter x1 (f) Sub-spectrum; U x2,i (f) represents the U after filtering by the i-th Gaussian filter x2 (f) Sub-spectrum of B i (f) represents the i-th Gaussian filter, i=1,2,...I, I represents the total number of Gaussian filters, f Lrepresents the minimum value of the sliding range of the center frequency of the Gaussian filter, ΔB represents the filter bandwidth, df represents the frequency domain moving step between the center frequencies of two adjacent Gaussian filters, df = (f H -f L ) / (I-1), f H Indicates the maximum value of the Gaussian filter center frequency sliding range.

[0020] S203, using inverse Fourier transform, reconstruct the sub-spectrum obtained in step S202 into the time domain, the specific formula is:

[0021] u x1,i (t) = IFT.U x1,i (f) /

[0022] u x2,i (t) = IFT.U x2,i (f) /

[0023] Where IFT represents the inverse Fourier transform, u x1,i (t) represents the i-th frequency domain component U x1,i (f) Reconstruct the signal components back to the time domain, u x2,i (t) represents the i-th frequency domain component U x2,i (f) Signal components reconstructed back into the time domain.

[0024] Further, in step S3, obtaining the phase difference between the waveguide signals includes the following contents:

[0025] S301. In the case of medium dispersion, u is calculated based on the maximum value of the Hilbert envelope. x1,i (t) and u x2,i The specific formula is:

[0026] e x1,i (t) = u x1,i (t+t m1 )

[0027] e x2,i (t) = u x2,i (t+t m2 )

[0028] Among them, e x1,i (t) represents u x1,i (t) time-shifted signal; e x2,i (t) represents u x2,i (t) is the time-shifted signal; t m1 Indicates u x1,i (t) is the offset time, represents the time corresponding to the maximum value of the Hilbert envelope, HT represents the Hilbert transform; t m2Indicates u x2,i (t) is the offset time,

[0029] S302, calculating the complex spectrum of the time-shifted signal, the specific formula is:

[0030] E x1,i (f) = FT[e x1,i (t)]

[0031] E x2,i (f) = FT[e x2,i (t)]

[0032] Among them, E x1,i (f) means e x1,i The complex spectrum of (t), E x2,i (f) means e x2,i (t) is the complex spectrum of

[0033] S303, calculating the phase difference between the time-shifted signals The specific formula is:

[0034]

[0035] Among them, α x1,i (f) means e x1,i The phase of (t), arctan[] represents the inverse tangent function, Im represents the real part of the spectrum, and Re represents the imaginary part of the spectrum; α x2,i (f) means e x2,i The phase of (t),

[0036]

[0037] Furthermore, in step S4, the reconstructed dispersion curve includes the following contents:

[0038] The calculation formula of phase velocity is:

[0039]

[0040] Among them, c p (i) represents the phase velocity; f i Represents the amplitude spectrum |E x1,i (f) |Peak-to-peak frequency; d represents the distance between two waveguide signals, d = x2-x1.

[0041] f i Corresponding to the amplitude spectrum |E x1,i (f)|The peak-to-peak frequency.

[0042] The reconstructed dispersion curve is the frequency and phase velocity. i ,c p (i) / Collection of scattered points.

[0043] Furthermore, the method further comprises step S5: verifying the accuracy of the dispersion curve reconstructed in step S4.

[0044] Furthermore, verification accuracy includes the following:

[0045] S501. Obtain parameters characterizing mechanical properties of composite materials, including ply direction, elastic matrix, and material density.

[0046] S502. Using a semi-analytical finite element method, obtain a theoretical dispersion curve of Lamb waves propagating in a composite material plate.

[0047] S503, comparing the dispersion curve reconstructed in step S4 with the theoretical dispersion curve in step S502, when the coincidence rate between the reconstructed dispersion curve and the theoretical dispersion curve reaches more than 90%, it indicates that the reconstructed dispersion curve meets the requirements.

[0048] Furthermore, in step S502, obtaining a theoretical dispersion curve includes the following contents:

[0049] The composite material is modeled, and the orthogonal three-dimensional global coordinate system xyz of the anisotropic composite laminate is established, where the axis x is parallel to the thickness direction of the plate, and the orthogonal material coordinate system x′y′z′ is established, where the axis y′ is parallel to the fiber orientation; the single-layer fiber orientation angle of the composite laminate relative to the global coordinate system is set to θ, and the viscoelasticity of the material is ignored. The elastic modulus of the composite material is expressed as:

[0050] in,

[0051] s = sin(θ), c = cos(θ);

[0052] C 11 , C 12 , C 13 , C 21 , C 22 , C 23 , C 31 , C 32 , C 33 , C 44 , C 55 , C 66 Both represent elastic constants, C 12 =C 21 , C 13 =C 31 , C 23 =C32 .

[0053] The wave vector K of the guided wave in the anisotropic plate structure is related to the propagation direction β of the guided wave, which can be specifically expressed as:

[0054]

[0055] Where k is the wave number, β is the wave propagation angle, and represents the corresponding unit direction vector.

[0056] The node displacement u is a function of time and space, which can be expressed as:

[0057] u(x,y,z,t)=Nq (e) exp{j[ωt+ksin(β)y-kcos(β)z]}

[0058] in, N represents the interpolation matrix composed of shape functions, represents the nth shape function, q (e) It represents the column vector of the internal node displacement components of the spectral unit, e represents the unit label, ω represents the angular frequency, exp{} represents the natural exponential function, and j represents the imaginary unit.

[0059] The strain field ε within the spectral unit is expressed as:

[0060] ε=[B1-jk y B2-jk z B3]q (e) exp[j(ωt+ksin(β)y-kcos(β)z)]

[0061] Where B1 = L x N x , N x represents the derivative of N in the x direction; B2 = L y N, B3=L z N, k y represents the component of the wave number in the y direction; k z represents the component of the wave number in the z direction.

[0062] C-based θ Get the mass matrix M and stiffness matrix K mn , the specific expression is:

[0063]

[0064] Among them, m (e) =∫(e) N T ρNdx,N T represents the transpose of N, ρ represents the material density; n e Indicates the number of spectral units;

[0065] Extending the Hamiltonian variation principle to the entire domain, combining the properties of all units into an overall property matrix, we get the global control equation, which is expressed as:

[0066] [A-γB]Q=0

[0067] in, ss=sin(β), cc=cos(β); Q=[q γq] T , γ=jk.

[0068] After the material-related parameters are given, the global control equation is solved to obtain the wave number changes in the corresponding frequency range of all waveguide modes, and then the theoretical phase velocity is obtained. The specific formula is:

[0069]

[0070] Among them, c p ′ represents the theoretical phase velocity; the phase velocity refers to the propagation velocity of the wave packet at a fixed phase point in the propagation direction.

[0071] Then the theoretical dispersion curve of guided waves propagating in composite materials is obtained.

[0072] Furthermore, the present invention also proposes an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the method for reconstructing the guided wave phase velocity dispersion based on spectral decomposition and phase spectrum enhancement are implemented.

[0073] Furthermore, the present invention also proposes a computer-readable storage medium, which stores a computer program. When the computer program is run by a processor, it executes the method for reconstructing the guided wave phase velocity dispersion based on spectral decomposition and phase spectrum enhancement.

[0074] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0075] 1. The present invention combines spectrum decomposition technology with enhanced phase spectrum technology to improve the sensitivity of small-amplitude components and realize broadband reconstruction of phase velocity dispersion curves.

[0076] 2. The reconstruction method of the present invention has high accuracy, is easy to use, and is low in cost, making it very suitable for industrial applications.

[0077] 3. The present invention can be used for ultrasonic nondestructive evaluation and structural health monitoring of industrial facilities, aerospace equipment, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 It is an overall implementation flow chart of the present invention.

[0079] Figure 2 It is a flow chart for implementing the guided wave phase velocity dispersion reconstruction of the present invention.

[0080] Figure 3 Schematic diagram of a COMSOL simulation model of an embodiment of the present invention.

[0081] Figure 4 It is a schematic diagram of a semi-analytical finite element model of a composite material of the present invention.

[0082] Figure 5 4 is a numerical simulation reconstruction result diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0083] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0084] To achieve the above purpose, the present invention proposes a guided wave phase velocity dispersion reconstruction method based on spectrum decomposition and phase spectrum enhancement, and verifies the reconstructed curve, which can realize the reconstruction of velocity value on broadband, and is divided into signal measurement, spectrum decomposition, phase spectrum enhancement, and dispersion reconstruction. Figure 1 As shown, the specific steps are as follows:

[0085] Among them, Figure 2 As shown, obtaining the reconstructed dispersion curve includes steps S1-S4:

[0086] S1. Use an oscilloscope to measure the adjacent waveguide signals u at two non-overlapping positions x1 and x2 at time t. x1 (t) and u x2 (t).

[0087] The simulation model established in the simulation software COMSOL is as follows Figure 3 As shown, it includes a composite laminate, an actuator and a sensor. Each layer of the composite laminate is connected together using a two-dimensional plane strain model, and each layer is modeled separately. The lower surface of the actuator and sensor is set to be grounded and connected to the composite plate through a thin linear elastic bonding layer. The actuator is used to load a voltage signal to excite the guided wave, and the two sensors are used to receive two adjacent guided wave signals.

[0088] The carbon fiber composite material plate used in this embodiment has orthotropic properties and its ply direction is [0°\90°]4s The main mechanical performance parameters are as follows:

[0089] Density: ρ = 1630.4 kg / m 3 ; Main elastic constants: C 11 =54.55GPa, C 12 =7.01GPa, C 13 =6.38GPa, C 22 =52.16GPa, C 23 =6.31GPa, C 33 =9.22GPa, C 44 =3.07GPa, C 55 =2.98GPa, C 66 =3.59GPa.

[0090] The model is used to simulate the generation of two signals received from the deployed piezoelectric sensors. The piezoelectric elements are connected to the composite laminate through linear elastic thin layer conditions. Each piezoelectric element is 5mm long and 0.5mm thick and is made of PZT-5H. In general, the accuracy of the numerical model depends on the temporal and spatial resolution of the analysis. The node spacing in the composite laminate model is set to ensure that there are at least 10 nodes on the minimum wavelength and the element growth rate is 1.25. For the time step resolution, the highest frequency is set to at least 20 points per cycle.

[0091] The excitation signal is a cosine pulse modulated by a Gaussian window, and the expression is as follows:

[0092]

[0093] Where G = 1, f c =200kHz, t0=12.5μs, σ=3.5×10 -6 .

[0094] S2, performing spectrum decomposition on the signal obtained in step S1 to obtain a set number of filtered waveguide signal components; the specific content is:

[0095] S201, calculate the spectrum of the signal, the specific formula is:

[0096] U x1 (f) = FT[u x1 (t)]

[0097] U x2 (f) = FT[u x2 (t)]

[0098] Among them, U x1 (f) represents u x1 The spectrum of (t), U x2(f) represents u x2 FT stands for Fourier transform and f stands for frequency.

[0099] S202, filtering the spectrum obtained in step S201, the specific formula is:

[0100] U x1,i (f) = U x1 (f) B i (f)

[0101] U x2,i (f) = U x2 (f) B i (f)

[0102] Among them, U x1,i (f) represents the U after filtering by the i-th Gaussian filter x1 (f) Sub-spectrum; U x2,i (f) represents the U after filtering by the i-th Gaussian filter x2 (f) Sub-spectrum of B i (f) represents the i-th Gaussian filter, i=1,2,...I, I represents the total number of Gaussian filters, f L represents the minimum value of the sliding range of the center frequency of the Gaussian filter, ΔB represents the filter bandwidth, df represents the frequency domain moving step between the center frequencies of two adjacent Gaussian filters, df = (f H -f L ) / (I-1), f H Indicates the maximum value of the Gaussian filter center frequency sliding range.

[0103] S203, using inverse Fourier transform, reconstruct the sub-spectrum obtained in step S202 into the time domain, the specific formula is:

[0104] u x1,i (t) = IFT.U x1,i (f) /

[0105] u x2,i (t) = IFT.U x2,i (f) /

[0106] Where IFT represents the inverse Fourier transform, u x1,i (t) represents the i-th frequency domain component U x1,i (f) Reconstruct the signal components back to the time domain, u x2,i (t) represents the i-th frequency domain component U x2,i (f) Signal components reconstructed back into the time domain.

[0107] S3, using phase spectrum enhancement technology, performing phase spectrum expansion processing on the signal components in step S2 to obtain the phase difference between the waveguide signals; the specific content is:

[0108] S301, signal time shift. In order to avoid uncertainty in the phase unwrapping process, each waveform u x1,i (t) and u x2,i (t) will be offset by t in the time domain m1 and t m2 In the case of moderate dispersion, u is calculated from the maximum value of the Hilbert envelope x1,i (t) and u x2,i The specific formula is:

[0109] e x1,i (t) = u x1,i (t+t m1 )

[0110] e x2,i (t) = u x2,i (t+t m2 )

[0111] Among them, e x1,i (t) represents u x1,i (t) time-shifted signal; e x2,i (t) represents u x2,i (t) is the time-shifted signal; t m1 Indicates u x1,i (t) is the offset time, represents the time corresponding to the maximum value of the Hilbert envelope, HT represents the Hilbert transform; t m2 Indicates u x2,i (t) is the offset time, The offset time corresponds to the maximum of the Hilbert envelope to compensate for the effect of the signal delay due to the phase velocity.

[0112] S302, calculate the spectrum of the time-shifted signal. Calculate the complex spectrum of the time-shifted signal, the specific formula is:

[0113] E x1,i (f) = FT[e x1,i (t)]

[0114] E x2,i (f) = FT[e x2,i (t)]

[0115] Among them, E x1,i (f) means e x1,i The complex spectrum of (t), E x2,i (f) means e x2,i (t) is the complex spectrum of

[0116] S303, phase difference calculation. Calculate the phase difference between the time-shifted signals The specific formula is:

[0117]

[0118] Among them, α x1,i (f) means e x1,i The phase of (t), arctan[] represents the inverse tangent function, Im represents the real part of the spectrum, and Re represents the imaginary part of the spectrum; α x2,i (f) means e x2,i The phase of (t),

[0119]

[0120] Phase α x1,i (f) and α x2,i (f) is calculated in the range [-π,π] radians, and some discontinuities will occur if the phase exceeds the limit of ±π radians. Therefore, the phase α x1,i (f) and α x2,i (f) must be expanded.

[0121] S4. Reconstruct the phase velocity and frequency of the guided wave mode to obtain the reconstructed dispersion curve; the specific content is:

[0122] The calculation formula of phase velocity is:

[0123]

[0124] Among them, c p (i) represents the phase velocity; f i Represents the amplitude spectrum |E x1,i (f) |Peak-to-peak frequency; d represents the distance between two waveguide signals, d = x2-x1.

[0125] f i Corresponding to the amplitude spectrum |E x1,i (f)|The peak-to-peak frequency.

[0126] The reconstructed dispersion curve is the frequency and phase velocity. i ,c p (i) / Collection of scattered points.

[0127] S5. Verify the accuracy of the dispersion curve reconstructed in step S4, specifically:

[0128] S501. Obtain parameters characterizing mechanical properties of composite materials, including ply direction, elastic matrix, and material density.

[0129] S502. Using the semi-analytical finite element method, obtain the theoretical dispersion curve of Lamb waves propagating in the composite material plate; the specific content is:

[0130] The composite material is modeled, and the orthogonal three-dimensional global coordinate system xyz of the anisotropic composite laminate is established, where the axis x is parallel to the thickness direction of the plate, and the orthogonal material coordinate system x′y′z′ is established, where the axis y′ is parallel to the fiber orientation; the single-layer fiber orientation angle of the composite laminate relative to the global coordinate system is set to θ, and the viscoelasticity of the material is ignored. The elastic modulus of the composite material is expressed as:

[0131] in,

[0132] s=sin(θ), c=cos(θ), C 12 =C 21 , C 13 =C 31 , C 23 =C 32 .

[0133] The wave vector K of the guided wave in the anisotropic plate structure is related to the propagation direction β of the guided wave, which can be specifically expressed as:

[0134]

[0135] Where k is the wave number, β is the wave propagation angle, and represents the corresponding unit direction vector.

[0136] The node displacement u is a function of time and space, which can be expressed as:

[0137] u(x,y,z,t)=Nq (e) exp{j[ωt+ksin(β)y-kcos(β)z]}

[0138] in, N represents the interpolation matrix composed of shape functions, represents the nth shape function, where the shape function uses the Lagrange interpolation polynomial of the Gauss-Lobatto-Legendre node, q (e) It represents the column vector of the internal node displacement components of the spectral unit, e represents the unit label, ω represents the angular frequency, exp{} represents the natural exponential function, and j represents the imaginary unit.

[0139] The strain field ε within the spectral unit is expressed as:

[0140] ε=[B1-jk yB2-jk z B3]q (e) exp[j(ωt+ksin(β)y-kcos(β)z)]

[0141] Where B1 = L x N x , N x represents the derivative of N in the x direction; B2 = L y N, B3=L z N, k y represents the component of the wave number in the y direction; k z represents the component of the wave number in the z direction.

[0142] C-based θ Get the mass matrix M and stiffness matrix K mn , the specific expression is:

[0143]

[0144] Among them, m (e) =∫ (e) N T ρNdx,N T represents the transpose of N, ρ represents the material density; n e Indicates the number of spectral units;

[0145] Extending the Hamiltonian variation principle to the entire domain, combining the properties of all units into an overall property matrix, we get the global control equation, which is expressed as:

[0146] [A-γB]Q=0

[0147] in, ss=sin(β), cc=cos(β); Q=[q γq] T , γ=jk.

[0148] After the material-related parameters are given, the global control equation is solved to obtain the wave number changes in the corresponding frequency range of all waveguide modes, and then the theoretical phase velocity is obtained. The specific formula is:

[0149]

[0150] Among them, c p ′ represents the theoretical phase velocity; the phase velocity refers to the propagation velocity of the wave packet at a fixed phase point in the propagation direction.

[0151] Then the theoretical dispersion curve of guided waves propagating in composite materials is obtained.

[0152] S503, comparing the dispersion curve reconstructed in step S4 with the theoretical dispersion curve in step S502, when the coincidence rate between the reconstructed dispersion curve and the theoretical dispersion curve reaches more than 90%, it indicates that the reconstructed dispersion curve meets the requirements.

[0153] Figure 4 This is a schematic diagram of the semi-analytical finite element model. The semi-analytical finite element method is used to obtain the phase velocity dispersion curve of the guided wave propagation theory.

[0154] Compare the theoretical curve with a series of scattered points reconstructed by the method proposed in the present invention, such as Figure 5 As shown, the theoretical dispersion curve is very close to the reconstructed dispersion curve, and the overlap rate is high, which indicates the correctness and feasibility of the method.

[0155] The embodiment of the present invention further provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. It should be noted that when the processor executes the computer program, the specific steps of the method provided in the embodiment of the present invention are corresponding to the specific steps of the method provided in the embodiment of the present invention, and the processor has the functional modules and beneficial effects corresponding to the execution method. For technical details not described in detail in this embodiment, please refer to the method provided in the embodiment of the present invention.

[0156] The embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program. It should be noted that when the computer program is executed by the processor, it corresponds to the specific steps of the method provided in the embodiment of the present invention, and has the functional modules and beneficial effects corresponding to the execution method. For technical details not described in detail in this embodiment, please refer to the method provided in the embodiment of the present invention.

[0157] 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 technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A guided wave phase velocity dispersion reconstruction method based on spectrum decomposition and phase spectrum enhancement, characterized in that: include: S1. Use an oscilloscope to measure the adjacent waveguide signals u at two non-overlapping positions x1 and x2 at time t. x1 (t) and u x2 (t); S2, performing spectrum decomposition on the signal obtained in step S1 to obtain a set number of filtered waveguide signal components; S3, using phase spectrum enhancement technology, performing phase spectrum expansion processing on the signal components in step S2 to obtain the phase difference between the waveguide signals; S4. Reconstruct the phase velocity and frequency of the guided wave mode to obtain the reconstructed dispersion curve.

2. The guided wave phase velocity dispersion reconstruction method based on spectrum decomposition and phase spectrum enhancement according to claim 1 is characterized in that: In step S2, the waveguide signal components are obtained including the following contents: S201, calculate the spectrum of the signal, the specific formula is: U x1 (f)=FT[u x1 (t)] U x2 (f)=FT[u x2 (t)] Among them, U x1 (f) represents u x1 The spectrum of (t), U x2 (f) represents u x 2(t) spectrum, FT stands for Fourier transform, and f stands for frequency; S202, filtering the spectrum obtained in step S201, the specific formula is: U x1，i (f)=U x1 (f)·B i (f) U x2，i (f)=U x2 (f)·B i (f) Among them, U x1，i (f) represents U after filtering by the i-th Gaussian filter x1 (f) Sub-spectrum; U x2，i (f) represents the U after filtering by the i-th Gaussian filter x2 (f); Bi(f) represents the i-th Gaussian filter, I represents the total number of Gaussian filters, f L represents the minimum value of the sliding range of the center frequency of the Gaussian filter, ΔB represents the filter bandwidth, df represents the frequency domain moving step between the center frequencies of two adjacent Gaussian filters, df = (f H -f L ) / (I-1), f H Indicates the maximum value of the sliding range of the center frequency of the Gaussian filter; S203, using inverse Fourier transform, reconstruct the sub-spectrum obtained in step S202 into the time domain, the specific formula is: u x1，i (t)=IFT(U x1，i (f)) u x2，i (t)=IFT(U x2，i (f)) Where IFT represents the inverse Fourier transform, u x1，i (t) represents the i-th frequency domain component U x1，i (f) Reconstruct the signal components back to the time domain, u x2，i (t) represents the i-th frequency domain component U x2，i (f) Signal components reconstructed back into the time domain.

3. The method for reconstructing guided wave phase velocity dispersion based on spectrum decomposition and phase spectrum enhancement according to claim 2, characterized in that: In step S3, obtaining the phase difference between the waveguide signals includes the following: S301. In the case of moderate dispersion, u is calculated based on the maximum value of the Hilbert envelope. x1，i (t) and u x2，i The specific formula is: e x1,i (t)=u x1,i (t+t m1 ) e x2,i (t)=u x2,i (t+t m2 ) Among them, e x1，i (t) represents u x1，i (t) time-shifted signal; e x2，i (t) represents u x2，i (t) is the time-shifted signal; t m1 Indicates u x1，i (t) is the offset time, represents the time corresponding to the maximum value of the Hilbert envelope, HT represents the Hilbert transform; t m2 Indicates u x2,i (t) is the offset time, S302, calculating the complex spectrum of the time-shifted signal, the specific formula is: E x1，i (f)=FT[e x1，i (t)] E x2，i (f)=FT[e x2，i (t)] Among them, E x1，i (f) means e x1，i The complex spectrum of (t), E x2，i (f) means e x2，i The complex spectrum of (t), FT represents Fourier transform; S303, calculating the phase difference between the time-shifted signals The specific formula is: Among them, α x1，i (f) means e x1，i The phase of (t), arctan[] represents the inverse tangent function, Im represents the real part of the spectrum, and Re represents the imaginary part of the spectrum; α x2，i (f) means e x2，i The phase of (t), 4. The method for reconstructing guided wave phase velocity dispersion based on spectrum decomposition and phase spectrum enhancement according to claim 1, characterized in that: In step S4, the reconstructed dispersion curve includes the following contents: The calculation formula of phase velocity is: Among them, c p (i) represents the phase velocity; f i Represents the amplitude spectrum |E x1,i (f)|peak-to-peak frequency; d represents the distance between two waveguide signals, d=x2-x1; f i Corresponding to the amplitude spectrum |E x1,i (f) The peak-to-peak frequency of |, i = 1, 2, ... I, I represents the total number of Gaussian filters; The reconstructed dispersion curve is the frequency and phase velocity. i ,c p (i) / Collection of scattered points.

5. The method for reconstructing guided wave phase velocity dispersion based on spectrum decomposition and phase spectrum enhancement according to claim 1, characterized in that: The method further comprises step S5: verifying the accuracy of the dispersion curve reconstructed in step S4.

6. The method for reconstructing guided wave phase velocity dispersion based on spectrum decomposition and phase spectrum enhancement according to claim 5, characterized in that: Verification accuracy includes the following: S501, obtaining parameters characterizing mechanical properties of composite materials, the parameters including ply direction, elastic matrix and material density; S502, using a semi-analytical finite element method, obtaining a theoretical dispersion curve of Lamb waves propagating in a composite material plate; S503, comparing the dispersion curve reconstructed in step S4 with the theoretical dispersion curve in step S502, when the coincidence rate between the reconstructed dispersion curve and the theoretical dispersion curve reaches more than 90%, it indicates that the reconstructed dispersion curve meets the requirements.

7. The method for reconstructing guided wave phase velocity dispersion based on spectrum decomposition and phase spectrum enhancement according to claim 6, characterized in that: In step S502, obtaining a theoretical dispersion curve includes the following contents: The composite material is modeled, and the orthogonal three-dimensional global coordinate system xyz of the anisotropic composite laminate is established, where the axis x is parallel to the thickness direction of the plate, and the orthogonal material coordinate system x′y′z′ is established, where the axis y′ is parallel to the fiber orientation; the single-layer fiber orientation angle of the composite laminate relative to the global coordinate system is set to θ, and the viscoelasticity of the material is ignored. The elastic modulus of the composite material is expressed as: in, s=sin(θ), c=cos(θ); C 11 , C 12 , C 13 , C 21 , C 22 , C 23 , C 31 , C 32 , C 33 , C 44 , C 55 , C 66 Both represent elastic constants, C 12 =C 21 , C 13 =C 31 , C 23 =C 32 ; The wave vector K of the guided wave in the anisotropic plate structure is related to the propagation direction β of the guided wave, which can be specifically expressed as: Where k is the wave number, β is the wave propagation angle, and represents the corresponding unit direction vector; The node displacement u is a function of time and space, which can be expressed as: u(x,y,z,t)=Nq (e) exp{j[ωt+ksin(β)y-kcos(β)z]} in, N represents the interpolation matrix composed of shape functions, represents the nth shape function, q (e) represents the column vector of the internal node displacement components of the spectral unit, e represents the unit label, ω represents the angular frequency, exp{} represents the natural exponential function, and j represents the imaginary unit; The strain field ε within the spectral unit is expressed as: ε=[B1-jk y B2-jk z B3]q (e) exp[j(ωt+ksin(β)y-kcos(β)z)] Where B1 = L x N x , N x represents the derivative of N in the x direction; B2 = L y N, B3=L z N, k y represents the component of the wave number in the y direction; k z represents the component of the wave number in the z direction; C-based θ Get the mass matrix M and stiffness matrix K mn , the specific expression is: Among them, m (e) =∫ (e) N T ρNdx,N T represents the transpose of N, ρ represents the material density; n e Indicates the number of spectral units; Extending the Hamiltonian variation principle to the entire domain, combining the properties of all units into an overall property matrix, we get the global control equation, which is expressed as: [A-γB]Q=0 Among them, ss=sin(β), cc=cos(β); Q=[q γq] T ,γ=jk; After the material-related parameters are given, the global control equation is solved to obtain the wave number changes in the corresponding frequency range of all waveguide modes, and then the theoretical phase velocity is obtained. The specific formula is: Among them, c p ′ represents the theoretical phase velocity; the phase velocity refers to the propagation velocity of the wave packet at a fixed phase point in the propagation direction; Then the theoretical dispersion curve of guided waves propagating in composite materials is obtained.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the guided wave phase velocity dispersion reconstruction method based on spectrum decomposition and phase spectrum enhancement as described in any one of claims 1 to 7 are implemented.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the guided wave phase velocity dispersion reconstruction method based on spectrum decomposition and phase spectrum enhancement according to any one of claims 1 to 7 is executed.

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