A high-precision and fast damage imaging method for anisotropic dispersive structures

Abstract

The present invention discloses a high-precision and rapid damage imaging method for anisotropic dispersive structures, comprising the following steps: S1, obtaining a complete wavenumber curve set; S2, obtaining a dispersion-compensated damage scattering signal database; S3, treating each point in the anisotropic structure to be monitored as a potential damage point, querying the dispersion-compensated damage scattering signal database, obtaining the dispersion compensation result that best matches any point therein, and calculating the pixel value of the point; S4, looping through step S3 until the pixel value calculation of all points in the monitored area of ​​the anisotropic structure to be monitored is completed. The present invention adopts the above-mentioned high-precision and rapid damage imaging method for anisotropic dispersive structures, and extracts the matching dispersion compensation result of the potential damage path from the database by optimizing the wavenumber difference at the center frequency, thereby avoiding performing a dispersion compensation process when calculating the pixel value of each potential damage point.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic guided wave structure health monitoring, and in particular to a high-precision rapid damage imaging method for anisotropic dispersion structures. Background Art

[0002] With the advancement of aircraft manufacturing technology, composite materials are widely used in modern advanced aircraft structures. However, the anisotropic properties of composite materials have brought huge challenges to current structural health monitoring technology.

[0003] In damage monitoring of anisotropic composite structures based on Lamb waves, the dispersion characteristics of Lamb waves cause the signal wave packet to expand and the amplitude to decrease, severely reducing the signal resolution and signal-to-noise ratio. Furthermore, the anisotropy of composite structures causes the propagation characteristics of Lamb waves to vary in all directions, making it more difficult to analyze the different wave packets in the Lamb wave signal and compensate for the dispersion, ultimately affecting the accuracy and reliability of damage monitoring.

[0004] Currently, the commonly used dispersion compensation methods are mainly divided into two categories: time reversal and Fourier domain signal processing methods.

[0005] Among them, the time reversal method can automatically compensate for dispersion without obtaining prior knowledge of the propagation characteristics of Lamb waves in the structure. However, the time information of the signal during propagation will be eliminated in this process, and additional wave packets will be generated when processing multi-wave packet signals, which will bring inconvenience to subsequent damage location or imaging.

[0006] Fourier domain signal processing methods can simultaneously compensate for multiple wave packets with the same propagation characteristics in Lamb wave signals, but they require prior knowledge of the wave number curve of Lamb waves in the structure.

[0007] However, the propagation characteristics of Lamb waves in different directions in anisotropic structures vary. Lamb wave damage scattering signals typically contain multipath propagation signal packets, each with different dispersion characteristics. Furthermore, the scattered signal path consists of multiple paths with different propagation directions, and the Lamb wave dispersion characteristics vary from path to path. Therefore, using a single-directional wavenumber curve to compensate for the dispersion of the damage scattered signal packet in anisotropic structures can lead to a mismatch between the wavenumber and the signal propagation characteristics. While calculating a comprehensive wavenumber curve based on the relative position of each potential damage point in the structure and the piezoelectric patch for dispersion compensation can address the wavenumber mismatch, the computational cost increases significantly. Summary of the Invention

[0008] To address the above problems, the present invention provides a high-precision and rapid damage imaging method for anisotropic dispersive structures. By optimizing the wavenumber difference at the center frequency, the matching dispersion compensation results of the potential damage path are extracted from the database, avoiding the need for dispersion compensation processing when calculating the pixel value of each potential damage point. While ensuring the best match between the wavenumber and the damage scattering signal, the computational cost is greatly reduced.

[0009] To achieve the above object, the present invention provides a high-precision and rapid damage imaging method for anisotropic dispersion structures, comprising the following steps:

[0010] S1. Obtaining a complete wavenumber curve in each propagation direction in the anisotropic structure to be monitored, that is, a complete wavenumber curve set;

[0011] S2. Based on the complete wave number curve set, a dispersion compensation damage scattering signal database corresponding to different directions is obtained;

[0012] S3, treating each point in the anisotropic structure to be monitored as a potential damage point, querying the dispersion compensation damage scattering signal database, obtaining the dispersion compensation result that best matches any point therein, and calculating the pixel value of the point;

[0013] S4, looping through step S3 until the pixel value calculations for all points in the monitored area of ​​the anisotropic structure are completed, thereby obtaining a high-resolution damage imaging result.

[0014] Preferably, step S1 specifically includes the following steps:

[0015] S11, arranging a piezoelectric array composed of piezoelectric sheets on the surface of the to-be-monitored region of the anisotropic structure to be monitored;

[0016] S12, measuring relative wave number curves of the selected ultrasonic guided wave mode in a finite number of propagation directions, i.e., a relative wave number curve set;

[0017] S13. Interpolate the relative wave number curve set to obtain a complete wave number curve set in each propagation direction.

[0018] Preferably, step S11 specifically includes the following steps:

[0019] A fan-shaped piezoelectric array composed of N piezoelectric sheets for measuring wave number is arranged on the surface of the anisotropic structure to be monitored;

[0020] At the same time, a sparse piezoelectric-guided wave array composed of M piezoelectric sheets for damage monitoring is arranged on the surface of the monitored area of ​​the anisotropic structure to be monitored.

[0021] Preferably, step S12 specifically includes the following steps:

[0022] In the fan-shaped piezoelectric array, the piezoelectric piece at the vertex of the fan is selected as the actuator, and the remaining piezoelectric pieces are used as sensors. The relative wave number curve set K in N-1 directions is measured. re (θ,ω), where θ is the measurement direction and ω is the angular frequency.

[0023] Preferably, step S13 specifically includes the following steps:

[0024] The relative wave number curve set K obtained by measurement re (θ, ω) is used as the benchmark for data interpolation, and the complete wave number curve set K in different directions is obtained. com (θ com ,ω), where θ com is the direction of equal intervals after interpolation.

[0025] Preferably, the damage scattering signals in the dispersion-compensated damage scattering signal database described in step S2 are collected by a sparse piezoelectric-guided wave array;

[0026] It specifically includes the following steps:

[0027] In a sparse piezoelectric-waveguide array, one piezoelectric patch is selected as an actuator and the other piezoelectric patches in the array are used as sensors. The sensing signals of each piezoelectric patch pair in the healthy and damaged state structures are collected and subtracted to obtain the damage scattering signal s of each piezoelectric patch pair. i-j (t), where ij represents a piezoelectric patch pair consisting of the i-th piezoelectric patch as an actuator and the j-th piezoelectric patch as a sensor, and i≠j; 1≤i,j≤M, and t is a time variable.

[0028] Preferably, step S2 specifically includes the following steps:

[0029] S21, linearization of wave number curve set:

[0030] With the complete wave number curve set K com (θ com ,ω) as prior knowledge, and according to the formula Perform linearization to obtain the linearized wave number curve set Where ω is the angular frequency, ω c is the central angular frequency of the ultrasonic guided wave signal, c g For the selected mode in ω c The group velocity under

[0031] S22. Calculate the interpolation mapping sequence set:

[0032] According to the function Ω(θ,ω)=K -1 [K lin (θ,ω)] to calculate the interpolation mapping sequence set Ω com(θ com ,ω), where K -1 (ω) is the inverse function of K(ω), K(θ,ω) and K lin (θ,ω) are the wave number curve set K com (θ com ,ω) and Wave number curve in the same θ direction;

[0033] S23, the damage to the scattered signal s i-j (t) Perform Fourier transform to obtain S i-j (ω), and according to Ω com (θ com ,ω) for S i-j (ω) is processed in the frequency domain to obtain That is S i-j (ω) Based on the wave number curve set K com (θ com ,ω)’s frequency domain interpolation result;

[0034] S24, yes Perform inverse Fourier transform to obtain the dispersion-compensated damage scattering signal database

[0035] Preferably, step S3 specifically includes the following steps:

[0036] S31, treating each point in the anisotropic structure to be monitored as a potential damage point, and calculating a comprehensive wavenumber curve of the potential damage scattering path based on the position of any point and each piezoelectric plate pair;

[0037] S32. Query the damage scattering signal database to obtain the dispersion-compensated damage scattering signal that best matches the integrated wavenumber curve, and calculate the pixel value of the point.

[0038] Preferably, step S32 specifically includes the following steps:

[0039] S321, assuming that there is an arbitrary potential damage point O in the anisotropic structure to be monitored h (x,y), where x and y are the point damage O h The horizontal and vertical coordinates are -Ma≤x≤+Ma, -Ma≤y≤+Ma, Ma is the set damage imaging area, the subscript h is the serial number of the potential damage point, and 0<h≤(2Ma) 2 ;

[0040] S322, according to point O h and the position of each piezoelectric pair, calculate the comprehensive wavenumber curve of the potential damage scattering path:

[0041]

[0042] Where θ1, r1 and K(θ1,ω) are the excitation piezoelectric plate P i To the potential damage scattering point O h Signal propagation direction, path length and wave number curves, θ2, r2 and K(θ2,ω) are the potential damage scattering points O h To the sensing piezoelectric piece P j Signal propagation direction, path length and wave number curves;

[0043] S323. Calculate the slope of the comprehensive wavenumber curve and the complete wavenumber curve set at the center frequency, that is, and K com '(θ com ,ω c ), query With K com '(θ com ,ω c )The minimum value of the slope difference is obtained, and the complete wave number curve is concentrated on θ h Wave number curve K in the direction h (θ h ,ω)with Most similar;

[0044] S324, from the damage scattering signal database Extracted from As a potential damage point h The dispersion compensation damages the scattered signal;

[0045] S325, calculate O h The pixel value of the point.

[0046] Preferably, between step S325 and step S324, the process further includes the following steps: h Dispersion compensation of the damaged scattered signal Perform the following array signal enhancement processing:

[0047]

[0048] where t ij (x, y) is the scattered signal from the excited piezoelectric piece P i Warp Point O h Transmitted to the sensing piezoelectric piece P j The propagation time is calculated as

[0049]

[0050] where c io is the scattered signal from P i Pass to point O h The group velocity, cjo is the scattered signal from point O h Pass to P j The group velocity, (x i ,y i ) and (x j ,y j ) are the piezoelectric sheets P i and P j 's coordinates.

[0051] The present invention has the following beneficial effects:

[0052] 1. Complete wavenumber curves in all propagation directions are acquired in the anisotropic structure. A dispersion-compensated damage scattering signal database is established based on the complete wavenumber curve set. This avoids performing dispersion compensation processing when calculating the pixel value of each potential damage point. By comparing the similarity between the complete wavenumber curve set and the comprehensive wavenumber curve of the potential damage path, the most matching dispersion compensation result is extracted from the database. This ensures the best match between the wavenumber and the damage scattering signal while greatly reducing the computational cost.

[0053] 2. A two-stage imaging signal-to-noise ratio and resolution improvement mechanism: This method first enhances the contrast between pixel values ​​in damaged and non-damaged areas by achieving matched dispersion compensation for the damage scattering signal wave packets at damaged pixels and non-matched dispersion compensation for noise or other signal wave packets at non-damaged pixels. It then further improves the signal-to-noise ratio and resolution of the imaging results by performing in-phase superposition of the damage scattering signal at the damaged pixel and non-in-phase superposition of the signal at the non-damaged pixel, thereby effectively improving the accuracy of damage imaging in anisotropic structures.

[0054] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a principle flow chart of a high-precision and rapid damage imaging method for anisotropic dispersion structures according to the present invention;

[0056] Figure 2 Schematic diagram of the arrangement of piezoelectric plates used to measure relative wave number curves in an aluminum plate structure of an experimental example of the present invention;

[0057] Figure 3 Schematic diagram of the piezoelectric piece used for damage imaging and the simulated damage arrangement in the aluminum plate structure of the experimental example of the present invention;

[0058] Figure 4 This is a waveform diagram of a 1.5-peak narrow-band excitation signal with a center frequency of 50 kHz in an experimental example of the present invention;

[0059] Figure 510 directions of relative wave number curve comparison diagram obtained from field measurements of an experimental example of the present invention;

[0060] Figure 6 is a comparison diagram of the complete wave number curve after interpolation processing of the experimental example of the present invention;

[0061] Figure 7 The relative wave number curve K is measured at 0° in the experimental example of the present invention. re (0°,ω), comprehensive wave number curve and Comparison chart;

[0062] Figure 8 is the original scattered damage signal s of the experimental example of the present invention 5-8 (t) waveform diagram;

[0063] Figure 9 Based on the wave number curve K re The non-matching dispersion compensation damage scattering signal of (0°,ω) Waveform diagram;

[0064] Figure 10 The experimental example of the present invention is based on the comprehensive wave number curve Matched dispersion compensation damage scattering signal Waveform diagram;

[0065] Figure 11 The experimental example of the present invention is based on the comprehensive wave number curve Matched dispersion compensation damage scattering signal Waveform diagram;

[0066] Figure 12 is the damage imaging result of the original dispersion signal;

[0067] Figure 13 Based on the wave number curve K re Non-matching dispersion compensation damage imaging at (0°,ω);

[0068] Figure 14 This is a high-precision damage imaging image based on the matching dispersion compensation result described in the present invention. DETAILED DESCRIPTION

[0069] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0070] A high-precision and rapid damage imaging method for anisotropic dispersion structures comprises the following steps:

[0071] S1. Obtaining a complete wavenumber curve in each propagation direction in the anisotropic structure to be monitored, that is, a complete wavenumber curve set;

[0072] Preferably, step S1 specifically includes the following steps:

[0073] S11, arranging a piezoelectric array composed of piezoelectric sheets on the surface of the to-be-monitored region of the anisotropic structure to be monitored;

[0074] Preferably, step S11 specifically includes the following steps:

[0075] A fan-shaped piezoelectric array composed of N piezoelectric sheets for measuring wave number is arranged on the surface of the anisotropic structure to be monitored;

[0076] At the same time, a sparse piezoelectric-guided wave array composed of M piezoelectric sheets for damage monitoring is arranged on the surface of the monitored area of ​​the anisotropic structure to be monitored.

[0077] In this embodiment, N≥3, M≥3.

[0078] S12, measuring relative wave number curves of the selected ultrasonic guided wave mode in a finite number of propagation directions, i.e., a relative wave number curve set;

[0079] Preferably, step S12 specifically includes the following steps:

[0080] In the fan-shaped piezoelectric array, the piezoelectric piece at the vertex of the fan is selected as the actuator, and the remaining piezoelectric pieces are used as sensors. The relative wave number curve set K in N-1 directions is measured. re (θ,ω), where θ is the measurement direction and ω is the angular frequency.

[0081] S13. Interpolate the relative wave number curve set to obtain a complete wave number curve set in each propagation direction.

[0082] Preferably, step S13 specifically includes the following steps:

[0083] The relative wave number curve set K obtained by measurement re (θ, ω) is used as the benchmark for data interpolation, and the complete wave number curve set K in different directions is obtained. com (θ com ,ω), where θ com is the direction of equal intervals after interpolation.

[0084] S2. Based on the complete wave number curve set, a dispersion compensation damage scattering signal database corresponding to different directions is obtained;

[0085] Preferably, the damage scattering signals in the dispersion-compensated damage scattering signal database described in step S2 are collected by a sparse piezoelectric-guided wave array;

[0086] It specifically includes the following steps:

[0087] In a sparse piezoelectric-waveguide array, one piezoelectric patch is selected as an actuator and the other piezoelectric patches in the array are used as sensors. The sensing signals of each piezoelectric patch pair in the healthy and damaged state structures are collected and subtracted to obtain the damage scattering signal s of each piezoelectric patch pair. i-j (t), where ij represents a piezoelectric patch pair consisting of the i-th piezoelectric patch as an actuator and the j-th piezoelectric patch as a sensor, and i≠j; 1≤i,j≤M, and t is a time variable.

[0088] Preferably, step S2 specifically includes the following steps:

[0089] S21, linearization of wave number curve set:

[0090] With the complete wave number curve set K com (θ com ,ω) as prior knowledge, and according to the formula Perform linearization to obtain the linearized wave number curve set Where ω is the angular frequency, ω c is the central angular frequency of the ultrasonic guided wave signal, c g For the selected mode in ω c The group velocity under

[0091] S22. Calculate the interpolation mapping sequence set:

[0092] According to the function Ω(θ,ω)=K -1 [K lin (θ,ω)] to calculate the interpolation mapping sequence set Ω com (θ com ,ω), where K -1 (ω) is the inverse function of K(ω), K(θ,ω) and K lin (θ,ω) are the wave number curve set K com (θ com ,ω) and Wave number curve in the same θ direction;

[0093] S23, the damage to the scattered signal s i-j (t) Perform Fourier transform to obtain S i-j (ω), and according to Ω com (θ com ,ω) for S i-j (ω) is processed in the frequency domain to obtain That is S i-j (ω) Based on the wave number curve set K com (θ com ,ω)’s frequency domain interpolation result;

[0094] S24, yes Perform inverse Fourier transform to obtain the dispersion-compensated damage scattering signal database

[0095] S3, treating each point in the anisotropic structure to be monitored as a potential damage point, querying the dispersion compensation damage scattering signal database, obtaining the dispersion compensation result that best matches any point therein, and calculating the pixel value of the point;

[0096] Preferably, step S3 specifically includes the following steps:

[0097] S31, treating each point in the anisotropic structure to be monitored as a potential damage point, and calculating a comprehensive wavenumber curve of the potential damage scattering path based on the position of any point and each piezoelectric plate pair;

[0098] S32. Query the damage scattering signal database to obtain the dispersion-compensated damage scattering signal that best matches the integrated wavenumber curve, and calculate the pixel value of the point.

[0099] Preferably, step S32 specifically includes the following steps:

[0100] S321, assuming that there is an arbitrary potential damage point O in the anisotropic structure to be monitored h (x,y), where x and y are the point damage O h The horizontal and vertical coordinates are -Ma≤x≤+Ma, -Ma≤y≤+Ma, Ma is the set damage imaging area, the subscript h is the serial number of the potential damage point, and 0<h≤(2Ma) 2 ;

[0101] S322, according to point O h and the position of each piezoelectric pair, calculate the comprehensive wavenumber curve of the potential damage scattering path:

[0102]

[0103] Where θ1, r1 and K(θ1,ω) are the excitation piezoelectric plate P i To the potential damage scattering point O h Signal propagation direction, path length and wave number curves, θ2, r2 and K(θ2,ω) are the potential damage scattering points O h To the sensing piezoelectric piece P j Signal propagation direction, path length and wave number curves;

[0104] S323. Calculate the slope of the comprehensive wavenumber curve and the complete wavenumber curve set at the center frequency, that is, and K com '(θcom ,ω c ), query With K com '(θ com ,ω c )The minimum value of the slope difference is obtained, and the complete wave number curve is concentrated on θ h Wave number curve K in the direction h (θ h ,ω)with Most similar;

[0105] S324, from the damage scattering signal database Extracted from As a potential damage point h The dispersion compensation damages the scattered signal;

[0106] S325, calculate O h The pixel value of the point.

[0107] Preferably, between step S325 and step S324, the process further includes the following steps: h Dispersion compensation damage scattered signal Perform the following array signal enhancement processing:

[0108]

[0109] where t ij (x, y) is the scattered signal from the excited piezoelectric piece P i Warp Point O h Transmitted to the sensing piezoelectric piece P j The propagation time is calculated as

[0110]

[0111] where c io is the scattered signal from P i Pass to point O h The group velocity, c jo is the scattered signal from point O h Pass to P j The group velocity, (x i ,y i ) and (x j ,y j ) are the piezoelectric sheets P i and P j 's coordinates.

[0112] S4, looping through step S3 until the pixel value calculations for all points in the monitored area of ​​the anisotropic structure are completed, thereby obtaining a high-resolution damage imaging result.

[0113] Step S4 in this embodiment specifically includes the following steps:

[0114] Step S3 is executed in a loop until the pixel values ​​of all points in the area to be measured are calculated, and the loop is terminated. The pixel value matrix of all points is used to perform high-precision damage imaging of the structure.

[0115] Experimental example:

[0116] This example studies Lamb waves, a typical ultrasonic guided wave, propagating in anisotropic carbon fiber-reinforced composite structures. The carbon fiber-reinforced composite plate is constructed from 16 layers of T700 unidirectional carbon fiber prepreg laid in a 0° direction, with a single layer thickness of 0.125 mm. The resin matrix is ​​T85 material supplied by Bayer AG of Germany. The specimen dimensions are 600 mm × 600 mm × 2 mm. The excitation signal is a 1.5-peak sinusoidal modulated signal with a center frequency of 50 kHz, resulting in the collected Lamb wave signal being primarily in the A0 mode. In this example, a fan-shaped piezoelectric array and a rectangular sparse piezoelectric array are arranged on the front and back surfaces of the specimen for wave number measurement and damage monitoring, respectively.

[0117] Reference Figure 1 As shown, a high-precision damage rapid imaging method for anisotropic structures of the present invention comprises the following steps:

[0118] (1) Arranging fan-shaped and rectangular piezoelectric arrays composed of piezoelectric sheets on the front and back surfaces of the anisotropic structure to be monitored respectively;

[0119] like Figure 2 As shown, 11 piezoelectric sheets P are arranged on the front surface of the composite material plate structure. A1 ~P A11 The piezoelectric array is formed, and a polar coordinate system is established with the center of the composite material plate structure as the coordinate origin. The positions of each piezoelectric piece are shown in Table 1:

[0120] Table 1

[0121]

[0122] like Figure 3 As shown, nine piezoelectric sheets P1 to P9 are arranged on the back of the composite material plate structure to form a piezoelectric array. A Cartesian coordinate system is established with the center of the composite material plate structure as the coordinate origin. The positions of the piezoelectric sheets are shown in Table 2:

[0123] Table 2

[0124]

[0125] (2) Measure the relative wave number curve of the A0 mode Lamb wave signal in the direction of 0° to 90°

[0126] Scan the piezoelectric array to obtain Figure 4 The center frequency is 50kHz and the peak narrowband excitation signal is 1.5 A1 -P A2 、P A1 -P A3 …P A1 -P A11 The Lamb wave A0 mode sensing signals of ten paths are then measured using the Lamb wave narrowband spectrum measurement method to obtain the following: Figure 5 The relative wave number curve K in ten directions with an angular resolution of 10° from 0° to 90° is shown. re (θ,ω).

[0127] (3) Interpolate the measured relative wave number curve set to obtain the complete wave number curve set in the direction of 0° to 90°

[0128] Based on the relative wave number curves in ten directions, two-dimensional linear interpolation is performed to obtain the following: Figure 6 The complete wave number curve K with an angular resolution of 1° in the direction of 0° to 90° is shown com (θ com ,ω), it should be noted that the bold black curve in the figure is the relative wave number curve in a finite number of directions obtained by measurement.

[0129] (4) Using a rectangular piezoelectric array to collect damage scattering signals

[0130] In a rectangular array of 9 piezoelectric sheets, one piezoelectric sheet is selected as the actuator and the other piezoelectric sheets in the array are used as sensors. The sensing signals of each piezoelectric sheet pair in the healthy and damaged state structures are collected respectively, and the difference is processed to obtain The damage scattering signal s of a piezoelectric pair i-j (t), where ij represents a piezoelectric patch pair consisting of the i-th piezoelectric patch as an actuator and the j-th piezoelectric patch as a sensor, and i≠j; 1≤i,j≤9, and t is a time variable.

[0131] (5) Based on the complete wave number curve set, the damage scattering signals of all paths are subjected to dispersion compensation processing to obtain a damage scattering signal database corresponding to the wave number curves in different directions, which specifically includes the following steps:

[0132] The first step is to use the complete wave number curve set K com (θ com ,ω) as prior knowledge, and according to the formula Perform linearization to obtain the linearized wave number curve set Where ω is the angular frequency, ω c is the central angular frequency of the ultrasonic guided wave signal, c gFor the selected mode in ω c The group velocity under

[0133] Step 2: According to the function Ω(θ,ω)=K -1 [K lin (θ,ω)] to calculate the interpolation mapping sequence set Ω com (θ com ,ω), where K -1 (ω) is the inverse function of K(ω), K(θ,ω) and K lin (θ,ω) are the wave number curve set K com (θ com ,ω) and Wave number curve in the same θ direction;

[0134] The third step is to analyze the 36 scattered damage signals s i-j (t) Perform Fourier transform to obtain S i-j (ω), and according to Ω com (θ com ,ω) for S i-j (ω) is processed in the frequency domain to obtain That is S i-j (ω) Based on the wave number curve set K com (θ com ,ω)’s frequency domain interpolation result;

[0135] Step 4: Then Perform inverse Fourier transform to obtain the dispersion-compensated damage scattering signal database The database is a 36×n×181 matrix, where n is the length of the damage scattering signal and 181 is θ com The number of .

[0136] (6) Each point in the anisotropic structure to be monitored is regarded as a potential damage point and the comprehensive wave number curve of the potential damage scattering path is calculated based on the position of one point and each piezoelectric plate pair.

[0137] For the sake of simplicity, this embodiment uses damage D1, D2 and piezoelectric sheets P5-P8 as examples. According to the formula:

[0138]

[0139] The comprehensive wave number curves of the damage scattering paths corresponding to D1 and D2 are calculated respectively and

[0140] (7) Obtain the dispersion-compensated damage scattering signal that best matches the integrated wavenumber curve from the damage scattering signal database and calculate the pixel value of that point;

[0141] Step 1: Calculate the comprehensive wave number curve at the center frequency and the slope of the complete wave number curve set, that is, and K com '(θ com ,ω c ), query With K com '(θ com ,ω c ) The minimum value of the slope difference is obtained, and the wave number curve K at the 43° and 44° directions of the complete wave number curve is obtained. com (43°,ω),K com (44°,ω) and Most similar.

[0142] Step 2: From the database Extracted from and The corresponding matching dispersion compensation damage scattering signals of damage points D1 and D2 are used.

[0143] This embodiment is based on the measurement relative wave number curve at 0° direction to calculate the original damage scattering signal s 5-8 (t) Perform dispersion compensation to obtain the non-matching dispersion compensation result s' 5-8 (t), and with and The comparison is made to measure the contrast effect of using non-matching and matching for dispersion compensation. Figure 7 Comparison of the measured relative wave number curve K at 0° direction re (0°,ω), comprehensive wave number curve and comprehensive wave number curve The difference between the original dispersion and the damage scattering signal s 5-8 (t) Figure 8 As shown in Figure 1, the secondary boundary reflection signals of damage D1, D2, and D2 are aliased, and the arrival position of the damage scattered signal cannot be identified. re The dispersion compensation damage scattering signal of (0°,ω) like Figure 9 As shown in Figure 2, the damage scattering signal wave packet has been partially recompressed, but the aliasing of the two damage signals D1 and D2 and the damage secondary boundary reflection signal is still serious and no separation occurs. and Matched dispersion compensation results and like Figure 10 and 11As shown in the figure, it can be clearly seen that the scattered wave packet is separated from the secondary boundary reflection signal of the damage. The amplitude of the D1 damage scattered signal is enhanced to 0.11V, and the amplitude of the D2 damage scattered signal is enhanced to 0.15V. Since the propagation characteristics of the two damage scattered wave packets are similar, and The compensation effect is close.

[0144] Step 3: Perform the following array signal enhancement processing on the matched dispersion compensation damage scattering signals of damage points D1 and D2:

[0145]

[0146] where t ij (x, y) is the scattered signal from the excited piezoelectric piece P i Warp Point O h Transmitted to the sensing piezoelectric piece P j The propagation time is calculated as:

[0147]

[0148] where c io is the scattered signal from P i Pass to point O h The group velocity, c jo is the scattered signal from point O h Pass to P j The group velocity, (x i ,y i ) and (x j ,y j ) are the piezoelectric sheets P i and P j coordinates of

[0149] Step 4: Calculate the pixel values ​​of the damage points D1 and D2

[0150] (8) Steps 6-7 are executed repeatedly until the pixel values ​​of all monitoring areas are calculated to obtain high-resolution damage imaging results.

[0151] The pixel values ​​of all points in the structure monitoring area are calculated, and the damage imaging results of the original dispersion signal are as follows: Figure 12 As shown, it can be seen that the damage points in the imaging results are divergent and the shape of the damage points is irregular, making it difficult to accurately determine the damage location. re The imaging results of the non-matching dispersion compensation damage at (0°,ω) are as follows Figure 13 As shown in Figure 1, it can be found that the imaging resolution has been effectively improved, the number of artifacts has been reduced, and a bright area appears near the actual damage location, but the two damages are not separated. The high-precision damage imaging results based on the matching dispersion compensation results are shown in Figure 1. Figure 14As shown in the image, the damage points are separated, the signal-to-noise ratio is significantly improved, the damage points are more focused, and the pixel values ​​are higher, allowing the locations of the two damages to be accurately determined. Analysis of the above imaging results shows that the proposed method for damage imaging of anisotropic structures can effectively improve the resolution and accuracy of the imaging results, thus demonstrating the effectiveness of the proposed method.

[0152] Therefore, the present invention adopts the above-mentioned high-precision and rapid damage imaging method for anisotropic dispersive structures. By optimizing the wavenumber difference at the center frequency, the matching dispersion compensation results of the potential damage path are extracted from the database, avoiding the need to perform dispersion compensation processing when calculating the pixel value of each potential damage point. While ensuring the best match between the wavenumber and the damage scattering signal, the calculation cost is greatly reduced.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-precision and rapid damage imaging method for anisotropic dispersive structures, characterized by: The following steps are involved: S1. Obtaining a complete wavenumber curve in each propagation direction in the anisotropic structure to be monitored, that is, a complete wavenumber curve set; S2. Based on the complete wave number curve set, a dispersion compensation damage scattering signal database corresponding to different directions is obtained; The damage scattering signals in the dispersion-compensated damage scattering signal database described in step S2 are collected by a sparse piezoelectric-guided wave array; It specifically includes the following steps: In a sparse piezoelectric-waveguide array, one piezoelectric patch is selected as an actuator and the other piezoelectric patches in the array are used as sensors. The sensing signals of each piezoelectric patch pair in the healthy and damaged state structures are collected and subtracted to obtain the damage scattering signals of each piezoelectric patch pair. ,in, Indicates the The piezoelectric piece is used as the actuator, A piezoelectric pair consisting of a piezoelectric piece as a sensor, and , is the time variable; Indicates the number of piezoelectric sheets; Step S2 specifically includes the following steps: S21, linearization of wave number curve set: Complete wave number curve set The wave number curve in is taken as prior knowledge, and according to the formula Perform linearization to obtain the linearized wave number curve set ,in is the angular frequency, is the central angular frequency of the ultrasonic guided wave signal, For the selected mode The group velocity under is the direction of equal intervals after interpolation; S22. Calculate the interpolation mapping sequence set: According to the function Calculate the interpolation mapping sequence set ,in for The inverse function of and Wave number curve sets and In the same Wave number curve under direction; S23, damage to the dispersion of scattered signals Perform Fourier transform to get , and follow right Perform frequency domain interpolation to obtain , That is Based on wave number curve set Frequency domain interpolation result of ; S24, yes Perform inverse Fourier transform to obtain the dispersion-compensated damage scattering signal database ; S3, treating each point in the anisotropic structure to be monitored as a potential damage point, querying the dispersion compensation damage scattering signal database, obtaining the dispersion compensation result that best matches any point therein, and calculating the pixel value of the point; Step S3 specifically includes the following steps: S31, treating each point in the anisotropic structure to be monitored as a potential damage point, and calculating a comprehensive wavenumber curve of the potential damage scattering path based on the position of any point and each piezoelectric plate pair; S311. Assume that there is an arbitrary potential damage point in the anisotropic structure to be monitored. ,in and Point damage The horizontal and vertical coordinates of , , is the set damage imaging area, subscript is the sequence number of the potential damage point, and ; S312, according to the point and the position of each piezoelectric pair, calculate the comprehensive wavenumber curve of the potential damage scattering path: ； in 、 and Excite the piezoelectric piece To the potential damage scattering point Signal propagation direction, path length and wave number curve, 、 and Potential damage scattering points To the sensing piezoelectric piece Signal propagation direction, path length and wave number curves; S32, querying the damage scattering signal database to obtain the dispersion-compensated damage scattering signal that best matches the integrated wavenumber curve, and calculating the pixel value of the point; S4, looping through step S3 until the pixel value calculations for all points in the monitored area of ​​the anisotropic structure are completed, thereby obtaining a high-resolution damage imaging result.

2. The high-precision rapid damage imaging method for anisotropic dispersive structures according to claim 1, characterized in that: Step S1 specifically includes the following steps: S11, arranging a piezoelectric array composed of piezoelectric sheets on the surface of the to-be-monitored region of the anisotropic structure to be monitored; S12, measuring relative wave number curves of the selected ultrasonic guided wave mode in a finite number of propagation directions, i.e., a relative wave number curve set; S13. Interpolate the relative wave number curve set to obtain a complete wave number curve set in each propagation direction.

3. The high-precision rapid damage imaging method for anisotropic dispersive structures according to claim 2, characterized in that: Step S11 specifically includes the following steps: The surface of the anisotropic structure to be monitored is arranged by A fan-shaped piezoelectric array composed of piezoelectric sheets for measuring wave number; At the same time, a plurality of A sparse piezoelectric-guided wave array composed of piezoelectric plates for damage monitoring.

4. The high-precision rapid damage imaging method for anisotropic dispersive structures according to claim 3, characterized in that: Step S12 specifically includes the following steps: In the fan-shaped piezoelectric array, the piezoelectric piece at the vertex of the fan is selected as the actuator, and the remaining piezoelectric pieces are used as sensors. The measurement results are relative wave number curves in different directions ,in is the measurement direction, is the angular frequency.

5. The high-precision rapid damage imaging method for anisotropic dispersive structures according to claim 4, characterized in that: Step S13 specifically includes the following steps: The relative wave number curve set obtained by measurement Data interpolation is performed based on the benchmark to obtain a complete set of wave number curves in different directions. .

6. The high-precision rapid damage imaging method for anisotropic dispersive structures according to claim 1, characterized in that: Step S32 specifically includes the following steps: S321. Calculate the slope value of the comprehensive wavenumber curve and the complete wavenumber curve set at the center frequency, that is, and , query and The minimum value of the slope difference is obtained, and the complete wave number curve is concentrated Wave number curve under direction Comprehensive wave number curve of potential damage scattering path Most similar; S322, from the damage scattering signal database Extracted from As a potential damage point The dispersion compensation damages the scattered signal; S323, calculated The pixel value of the point.

7. The high-precision rapid damage imaging method for anisotropic dispersive structures according to claim 6, characterized in that: Between step S322 and step S323, the potential damage point is also included. Dispersion compensation damage scattered signal Perform the following array signal enhancement processing: ； in The scattered signal is from the excited piezoelectric piece Warp Point Transmitted to the sensing piezoelectric piece The propagation time is calculated as ； in The scattered signal from Transfer to point The group velocity, is the scattered signal from point Transmit to The group velocity, and Piezoelectric sheets and 's coordinates.

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