Dispersion wave compact array damage monitoring method under large range non-uniform environment temperature change

Abstract

The application discloses a dispersion wave dense array damage monitoring method under large-range non-uniform environmental temperature change, relates to the field of ultrasonic wave structure health monitoring, and comprises the following steps: S1: arranging a sensor; S2: establishing a reference database under different environmental temperatures; S3: collecting a current monitoring signal of a structure under a current environmental temperature; S4: performing compensation processing on the current monitoring signal; S5: reconstructing a reference signal; S6: obtaining a damage scattering signal; S7: performing beam synthesis processing on the damage scattering signal; and S8: calculating a dense array imaging graph. The dispersion wave dense array damage monitoring method under large-range non-uniform environmental temperature change is adopted, temperature compensation, dispersion compensation and the dense array are combined, and high-reliability dense array damage imaging under large-range non-uniform temperature change is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ultrasonic guided wave structure health monitoring, in particular to a dispersion guided wave dense array damage monitoring method under large range non-uniform environmental temperature change. BACKGROUND

[0002] The ultrasonic guided wave dense array damage monitoring method has become one of the most effective aviation structure health monitoring methods, and has gradually been put into engineering application. However, the ultrasonic guided wave has dispersion characteristics when propagating, which will change the wave packet waveform of the ultrasonic guided wave, cause the wave packet to expand, the amplitude to become smaller, the wave packet energy to disperse, and the farther the propagation distance, the more serious the wave packet expansion, which will seriously reduce the signal-to-noise ratio of the synthesized signal of the traditional ultrasonic guided wave dense array technology and the resolution ability to damage signal. On the other hand, in actual application, the temperature change of the aviation structure service environment will affect the properties of the sensor, the adhesive layer and the measured structure, causing the ultrasonic guided wave monitoring signal to change extra damage-irrelevant. This environmental temperature influence will disturb and even drown the real damage information in the monitoring signal, and ultimately reduce the reliability of the dense array damage imaging result.

[0003] In view of the above problems, there are currently a variety of dispersion compensation and temperature compensation methods. In the dispersion compensation method, they only solve the influence of dispersion on the ultrasonic guided wave dense array damage monitoring on one side, which will lead to the final dense array damage imaging resolution not high enough or even damage monitoring failure.

[0004] In actual application, as the temperature change range increases, the influence of temperature on amplitude gradually becomes serious, and the compensation ability of time domain bending to signal amplitude is limited, so the method limits the temperature compensation range of the ultrasonic guided wave. When the environmental temperature changes in a large range and non-uniformly, the amplitude of each wave packet of the ultrasonic guided wave signal changes non-uniformly, which leads to the traditional overall signal matching being unable to well compensate the amplitude difference of each wave packet, thereby limiting the application in a large range of non-uniform environment.

[0005] Therefore, it is necessary to provide a dispersion guided wave dense array damage monitoring method under large range non-uniform environmental temperature change to solve the above problems. SUMMARY

[0006] The application aims to provide a dispersion wave dense array damage monitoring method under a wide range of non-uniform environment temperature changes, combine frequency domain beam synthesis and dispersion compensation to solve the problems of interference of ultrasonic wave dispersion on the dense array beam synthesis process and resolution reduction caused by wave packet expansion, aim at the non-uniform problems of signal wave packet amplitude and phase change caused by a wide range of non-uniform temperature changes, compensate the non-uniform phase change through the powerful flexible regulation ability of time domain bending, match the signals at each temperature in the database with the current monitoring signal in segments to solve the non-uniform amplitude change problem, and finally realize the dispersion ultrasonic wave dense array damage monitoring under a wide range of non-uniform temperature changes.

[0007] To achieve the above-mentioned purpose, the application provides a dispersion wave dense array damage monitoring method under a wide range of non-uniform environment temperature changes, comprising the following steps:

[0008] S1: arranging sensors, arranging Q piezoelectric sheets on the surface of a structure to be monitored to form a linear dense array and numbering from 1 to Q;

[0009] S2: establishing a reference database under different environment temperatures, under the condition of uniform change of environment temperature, collecting reference signals v0 of the measured structure health state under different environment temperatures ij (T a ,t) to form a database;

[0010] Wherein, ij represents a piezoelectric sheet pair composed of the i-th piezoelectric sheet as an exciter and the j-th piezoelectric sheet as a sensor, and i≠j, 1≤i,j≤Q, T a is a temperature variable, and t is a time variable;

[0011] S3: collecting the current monitoring signal of the structure under the current environment temperature, under the condition of non-uniform change of the current environment temperature, collecting the current monitoring signal of the measured structure as v1 ij (T b ,t), wherein T b is the highest temperature of the measured structure under the condition of non-uniform change of the current environment temperature;

[0012] S4: compensating the current monitoring signal obtained in step S3, the collected current monitoring signal v1 ij (T b ,t) is first compensated to obtain Then, temperature compensation is performed to obtain

[0013] S5: according to the database established in step S2 and the current monitoring signal compensated in step S4, the reference signal v0(t) is reconstructed;

[0014] S6: based on the reconstructed reference signal v0(t) in step S5 and the current monitoring signal after compensation processing in step S4 to obtain the damage scattering signal s DC-TC (t);

[0015] S7: beamforming processing on the damage scattering signal: for each scanning angle θ, beamform all the damage scattering signals s DC-TC (t) to obtain the beamformed signal at each scanning angle

[0016] S8: according to the beamformed signals at each scanning angle obtained in step S7 to obtain the dense array damage monitoring imaging result.

[0017] Preferably, in step S2, the following steps are specifically included:

[0018] S21: collecting the ultrasonic guided wave reference signal v0 of each piezoelectric patch pair under the health state of the measured structure at different uniform temperatures ij (T a ,t);

[0019] S22: performing dispersion compensation processing on the reference signals at different uniform temperatures to obtain

[0020] S23: taking the normal temperature signal as the reference, performing temperature compensation processing on the signals at the remaining temperatures to obtain the reference signal database after compensation processing wherein T0 is the normal temperature;

[0021] S24: according to the wave packet distribution in performing segmentation processing to obtain the segmented reference signal database.

[0022] Preferably, the dispersion compensation processing in step S22 specifically includes:

[0023] S221: obtaining the linearized wave number curve: K1(ω) = K0(ω c )+1 / c g ·(ω-ω c )

[0024] wherein K1(ω) is the linearized wave number curve, K0(ω) is the wave number curve of the original dispersion of the ultrasonic guided wave signal in the structure at temperature T0, ω is the angular frequency, ω c is the center angular frequency of the ultrasonic guided wave signal, c g is the group velocity of the selected guided wave mode at ω c ;

[0025] S222: Calculate the frequency domain interpolation mapping sequence:

[0026] Where Ω1(ω) is the calculated frequency domain interpolation mapping sequence. It is the inverse function of K0(ω);

[0027] S223: For v0 ij (T a Frequency domain interpolation is performed on t):

[0028] in, V0 is the result of frequency domain interpolation. ij (T a ,ω) is v0 ij (T a The Fourier transform result of ,t);

[0029] S224: Yes Performing the inverse Fourier transform yields

[0030] Preferably, in step S23, the temperature compensation process specifically includes:

[0031] by For reference, Temperature compensation processing was performed to obtain Specifically as follows:

[0032] according to The various signal data points {x1,x2,...,x z ,...,x N}and Each signal data point {y1,y2,...,y z ,...,y N}, seeking and Distance matrix D between N×N Where N is and The number of data points, 1 ≤ z ≤ N;

[0033] Its matrix element D(i,j) is calculated as follows:

[0034] D(i,j)=||x i -y j ||2

[0035] Where || ||2 represents x i and y j The Euclidean distance between them;

[0036] Find the distance matrix D′ N×N The matrix element D′(i,j) is calculated as follows:

[0037]

[0038] Where max{} represents the maximum value selection operation, and w is the bending range adjustment parameter, with a value range of w≥0;

[0039] Determine according to the following recursive formula and The cumulative distance matrix A between them N×N :

[0040] A(i,j)=D′(i,j)+min[A(i-1,j),A(i-1,j-1),A(i,j-1)]

[0041] Where A(i,j) is A N×N The elements are A(1,1)=D′(1,1), and min[] represents the minimum value selection operation;

[0042] Will and The optimal time-bending path between them is defined as a representation and The sequence of ordered pairs representing the optimal matching mappings between data points is denoted as: P = {p1, p2, ..., p...} k ,…,p K};

[0043] Where 1≤k≤K, N≤K≤2N+1, and ordered pairs p k =(i k ,j k ) indicates that The i-th k Data points and The jth k Data points Pairing, 1≤i k ≤N, 1≤j k ≤N; in A N×N China and Israel p K Starting from (N,N) and ending at (1,1), the search is performed iteratively as follows:

[0044]

[0045] In reverse, we can determine P = {p1, p2, ..., p} k ,…,p K}, where, (a,b)∈[(0,1),(1,0),(1,1)], ik -a≥1,j k -b≥1;

[0046] In sequence, according to P = {p1, p2, ..., p...} k ,…,p K Each ordered pair p in} k =(i k ,j k ),Will The jth k Data points Assigned as the i-th in the new current signal k From the data points, we obtain:

[0047]

[0048] in, This is the reference signal in the temperature-compensated database.

[0049] Preferably, step S5 specifically includes:

[0050] Based on the database reference signal after compensation processing The wave packet distribution is segmented to construct a segmented database, and then the current monitoring signal after compensation processing is used. The reference signals at different temperatures in the segmented database are segmented and matched. The reference signal with the highest correlation in the segment is used as the segment reference signal. The segment reference signals are then spliced ​​together to obtain the reconstructed reference signal v0(t).

[0051] Preferably, step S7 specifically includes the following steps:

[0052] S71: The obtained damage scattering signal Perform frequency domain pre-interpolation to obtain

[0053] S72: The result obtained in step S71 The time-domain beamforming signal is obtained by delaying and superimposing the signals according to the scanning angle θ, and then performing an inverse Fourier transform. The formula is as follows:

[0054]

[0055] S73: Yes Dispersion compensation processing is performed to obtain

[0056] Preferably, in step S71, the frequency domain pre-interpolation process specifically includes the following steps:

[0057] S711: Yes The Fourier transform is performed to obtain

[0058] S712: performing frequency domain pre-interpolation processing on

[0059] is the frequency domain pre-interpolation processing result, is the inverse function of Ω1(ω);

[0060] S713: performing inverse Fourier transform on

[0061] Preferably, in step S8, specifically comprising: dividing the region imaged by the dense array into 1mm*1mm squares, and one square is one pixel point in the damage imaging map.

[0062] Supposing each square is a potential damage point, the angle θ and the distance R of the square relative to the center of the dense array are determined, and the calculation formula of the angle θ is:

[0063] θ=arctan(y / x)

[0064] wherein arctan() is the inverse tangent function, θ is rounded when calculated, and x and y are the horizontal and vertical coordinates of the square in the Cartesian coordinate system, respectively.

[0065] The calculation formula of the distance R is:

[0066]

[0067] According to the distance R, the beam synthesis signal under the angle θ scattered from the square is determined, and the amplitude value is taken as the pixel value of the square, and finally the imaging result corresponding to the scanning region is obtained. When the amplitude value is determined according to the distance R, the position of the signal data point corresponding to the square needs to be calculated, and the calculation formula is:

[0068] n=Rf a / 0.5c g

[0069] wherein n∈[1,N] is the number of signal data points, f a is the signal sampling rate.

[0070] Preferably, the number Q of piezoelectric sheets is Q≥3.

[0071] Therefore, the damage monitoring method of the frequency-dispersive guided wave dense array under the large-range non-uniform environmental temperature change has the following beneficial effects:

[0072] ​​​(1) The present application combines frequency domain beam synthesis and dispersion compensation to solve the problem of interference of ultrasonic guided wave dispersion on the process of dense array beam synthesis and the problem of resolution reduction caused by wave packet expansion.

[0073] (2) The present application adopts a time domain bending method to solve the problem of non-uniform phase change under a wide range of non-uniform temperature changes, and solves the problem of non-uniform amplitude change by segmenting the matching of the reference signal at each temperature in the database with the current monitoring signal, thereby facilitating wide range temperature compensation in actual ultrasonic guided wave dense array damage monitoring.

[0074] The technical solutions of the present application will be described in further detail below with the help of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 is a flowchart of the dispersion guided wave dense array damage monitoring method of the present application under a wide range of non-uniform environmental temperature changes;

[0076] Figure 2 is a schematic diagram of the arrangement of piezoelectric sheets and simulated damage in the aluminum plate structure in the embodiment of the present application;

[0077] Figure 3 is a graph of the original healthy sensing signal at different temperatures in the database in the embodiment of the present application, taking P3-P7 piezoelectric sheets as an example;

[0078] Figure 4 is a graph of the healthy sensing signal at different temperatures in the database after the signal is processed by dispersion compensation in the embodiment of the present application, taking P3-P7 piezoelectric sheets as an example;

[0079] Figure 5 is a graph of the healthy sensing signal at different temperatures in the database after the signal is processed by dispersion compensation and temperature compensation in the embodiment of the present application, taking P3-P7 piezoelectric sheets as an example, and the black vertical lines in the graph are segmentation points;

[0080] Figure 6 is a waveform comparison graph of the current monitoring signal and the optimal reference segmented signal in the embodiment of the present application;

[0081] Figure 7 is a waveform comparison graph of the current monitoring signal and the normal temperature healthy reference signal in the embodiment of the present application under non-uniform 80℃;

[0082] Figure 8 is a waveform comparison graph of the damage scattering signal and the normal temperature damage scattering signal under a 65℃ temperature difference in the embodiment of the present application;

[0083] Figure 9This is an embodiment of the present invention. After temperature compensation processing The reference signal v0 reconstructed after segmentation matching 37 Waveform comparison chart of (t);

[0084] Figure 10 This is an embodiment of the present invention. With v0 37 (t) Damage scattering signal obtained by subtraction Damage scattering signal at room temperature Waveform comparison chart;

[0085] Figure 11 This is a waveform comparison diagram of the frequency domain beamforming result ss1(140°, 80°, t) under a damage angle of 140° and a temperature difference of 65° and room temperature of 15° in the embodiment of the present invention.

[0086] Figure 12 This is the frequency domain beamforming result after temperature compensation processing at a damage angle of 140° in this embodiment of the invention. A waveform comparison of the frequency domain beamforming result ss1(140°, 15°, t) at the same temperature as 15°C.

[0087] Figure 13 This is the result obtained after performing dispersion compensation processing on ss1(140°, 80°C, t) and ss1(140°, 15°C, t) in the embodiments of the present invention. Comparison of signal waveforms with ss2(140°, 15℃, t);

[0088] Figure 14 This is an embodiment of the present invention. The result obtained after performing dispersion compensation processing on ss1(140°, 15℃, t) Comparison of signal waveforms with ss2(140°, 15℃, t);

[0089] Figure 15 This is the phased array imaging result at the same temperature of 15°C in the embodiment of the present invention;

[0090] Figure 16 This is the phased array imaging result under a temperature difference of 65°C in the embodiment of the present invention;

[0091] Figure 17 This is the phased array imaging result after temperature compensation processing in the embodiment of the present invention. Detailed Implementation

[0092] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0093] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the meanings as commonly understood by one of ordinary skill in the art to which this application pertains.

[0094] The terms "comprise", "comprising", "include", "including" and the like are meant to be interpreted broadly to encompass the elements listed after such terms. The terms "inner", "outer", "upper", "lower", and the like are used for convenience only and are not intended to convey any mandatory or restrictive meanings among the devices or elements to which they refer. The terms "attached", "connected" and the like are meant to encompass a direct connection between elements or an indirect connection between elements through other elements. The terms "attached", "connected" and the like are meant to encompass a connection between elements or an interaction between elements.

[0095] Embodiment

[0096] A typical ultrasonic guided wave propagating in a 2024 aluminum plate structure is taken as the research object. The aluminum plate has a size of 400mm×400mm×2mm. A 1.5-peak sinusoidal modulated signal with a center frequency of 100kHz is selected as the excitation signal, so that the guided wave signals collected are mainly in the A0 mode. In the embodiment, the guided wave health signals of the aluminum plate under uniform temperature fields at 15℃, 30℃, 50℃, 70℃ and 90℃ are first collected as a database, and then the damage signals of the aluminum plate under a non-uniform temperature field with a maximum temperature of 80℃ are collected. The signals at each temperature are subjected to frequency dispersion compensation processing, and then the guided wave health signals at 15℃ under normal temperature are taken as the reference signals, and the signals at other temperatures are subjected to temperature compensation processing. Then, the database health signals and the current monitoring signals are subjected to segmented processing, the current monitoring signals are matched with the database health signals in segments, and the scattering signals eliminating the temperature effect are reconstructed. Then, the scattering signals are subjected to inverse frequency dispersion compensation processing, and then subjected to frequency domain beam synthesis processing. The signals after the frequency domain beam synthesis are subjected to frequency dispersion compensation processing, and finally the energy of the frequency domain beam synthesis signals at each angle after the frequency dispersion compensation processing is plotted in the form of gray scale on the same graph according to the Cartesian rectangular coordinate system to obtain the dense array damage monitoring imaging result. The signals in P3-P7 are taken as examples to analyze the effect of frequency dispersion compensation and temperature compensation.

[0097] As Figure 1As shown, the present application provides a dispersion wave dense array damage monitoring method under a wide range of non-uniform ambient temperature changes, comprising the following steps:

[0098] S1: arranging sensors, arranging Q piezoelectric sheets on the surface of the structure to be monitored to form a linear dense array and numbering from 1 to Q; the value range of the number of piezoelectric sheets Q is Q≥3.

[0099] As shown Figure 2 , 9 piezoelectric sheets P1-P9 are arranged on the surface of the aluminum plate structure, the distance between adjacent piezoelectric sheets is 10mm, a Cartesian coordinate system is established with the center of the piezoelectric dense array (piezoelectric sheet P5) as the coordinate origin, the x-axis is 7mm away from the lower boundary of the aluminum plate, and the piezoelectric sheet coordinates are shown in Table 1:

[0100] Table 1

[0101]

[0102] S2: Establish a reference database under different ambient temperatures, under the condition of uniform change of ambient temperature, collect 36 piezoelectric sheet pairs under the uniform temperature field of 15℃, 30℃, 50℃, 70℃ and 90℃ respectively Health signal v0 ij (T a ,t) as a reference signal, taking the signal at 15℃ as the reference, the signals at other temperatures are temperature compensated to obtain and to build a database;

[0103] Wherein, ij represents a piezoelectric sheet pair composed of the ith piezoelectric sheet as an exciter and the jth piezoelectric sheet as a sensor, and i≠j, 1≤i, j≤Q, T a is the temperature variable, and t is the time variable;

[0104] In step S2, it specifically comprises the following steps:

[0105] S21: Collecting ultrasonic wave reference signals v0 ij (T a ,t) of each piezoelectric sheet pair under different uniform temperatures under the health state of the measured structure;

[0106] S22: Dispersive compensation processing of the reference signals under each uniform temperature to obtain The dispersive compensation processing in step S22 specifically includes:

[0107] S221: Solving the linearized wave number curve: K1(ω)=K0(ω c )+1 / c g ·(ω-ω c )

[0108] Where K1(ω) is the linearized wavenumber curve, K0(ω) is the wavenumber curve of the original dispersion of the guided wave mode corresponding to the ultrasonic guided wave signal in the structure at temperature T0, and ω is the angular frequency. c c is the center angular frequency of the ultrasonic guided wave signal. g For the selected waveguide mode at ω c The group velocity below;

[0109] S222: Calculate the frequency domain interpolation mapping sequence:

[0110] Where Ω1(ω) is the calculated frequency domain interpolation mapping sequence. It is the inverse function of K0(ω);

[0111] S223: For v0 ij (T a Frequency domain interpolation is performed on t):

[0112] in, V0 is the result of frequency domain interpolation. ij (T a ,ω) is v0 ij (T a The Fourier transform result of ,t);

[0113] S224: Yes Performing the inverse Fourier transform yields

[0114] S23: Using a normal temperature signal Using this as a reference, temperature compensation processing is performed on signals at other temperatures to obtain a compensated reference signal database. Where T0 is room temperature; in step S23, the temperature compensation process specifically includes:

[0115] by For reference, Temperature compensation processing was performed to obtain Specifically as follows:

[0116] according to The various signal data points {x1,x2,...,x z ,…,x N}and Each signal data point {y1,y2,…,y z ,...,y N}, seeking and Distance matrix D between N×N Where N is and The number of data points, 1 ≤ z ≤ N;

[0117] Its matrix element D(i,j) is calculated as follows:

[0118] D(i,j)=||x i -y j ||2

[0119] Where || ||2 represents x i and y j The Euclidean distance between them;

[0120] Find the distance matrix D′ N×N The matrix element D′(i,j) is calculated as follows:

[0121]

[0122] Where max{} represents the maximum value selection operation, and w is the bending range adjustment parameter, with a value range of w≥0;

[0123] Determine according to the following recursive formula and The cumulative distance matrix A between them N×N :

[0124] A(i,j)=D′(i,j)+min[A(i-1,j),A(i-1,j-1),A(i,j-1)]

[0125] Where A(i,j) is A N×N The elements are A(1,1)=D′(1,1), and min[] represents the minimum value selection operation;

[0126] Will and The optimal time-bending path between them is defined as a representation and The sequence of ordered pairs representing the optimal matching mappings between data points is denoted as: P = {p1, p2, ..., p...} k ,…,p K};

[0127] Where 1≤k≤K, N≤K≤2N+1, and ordered pairs p k =(i k ,j k ) indicates that The i-th k Data points and The jth k Data points Pairing, 1≤i k ≤N, 1≤jk ≤N; in A N×N China and Israel p K Starting from (N,N) and ending at (1,1), the search is performed iteratively as follows:

[0128]

[0129] In reverse, we can determine P = {p1, p2, ..., p} k ,…,p K}, where, (a,b)∈[(0,1),(1,0),(1,1)], i k -a≥1,j k -b≥1;

[0130] In sequence, according to P = {p1, p2, ..., p...} k ,…,p K Each ordered pair p in} k =(i k ,j k ),Will The jth k Data points y jk Assigned as the i-th in the new current signal k From the data points, we obtain:

[0131]

[0132] in, This is the reference signal in the temperature-compensated database.

[0133] S24: According to The wave packet distribution in the signal is segmented to obtain a segmented reference signal database.

[0134] S3: Collect the current monitoring signal of the structure under the current ambient temperature. Under the condition of non-uniform change of the current ambient temperature, the current monitoring signal of the measured structure is collected as v1. ij (T b ,t), where T b This represents the highest temperature of the structure under test under the current non-uniform temperature change conditions.

[0135] S4: Perform compensation processing on the current monitoring signal obtained in step S3, and process the current monitoring signal v1 of the acquired structure under test. ij (T b First, dispersion compensation is performed to obtain... Then, temperature compensation processing is performed to obtain... The dispersion compensation process used is similar to steps S221-S224, and the temperature compensation process is similar to step S23.

[0136] S5: Reconstruct the reference signal v0(t) according to the database established in step S2 and the current monitoring signal after compensation processing in step S4; take the piezoelectric sheet pair P3-P7 as an example, Figures 3 to 5 To establish a segmented database process, wherein Figure 3 is the original healthy sensing signal graph at each temperature in the database, Figure 4 is the healthy sensing signal graph after dispersion compensation, Figure 5 is the signal graph after temperature compensation of the signals at the remaining temperatures based on the signal at 15°C, and the segmented database is constructed according to the wave packet distribution of the reference signal of each piezoelectric sheet pair at different uniform temperatures, and the black vertical lines in the graph are the segmentation points;

[0137] A scatterer D is introduced at the randomly selected damage coordinates (-140, 118) on the aluminum plate, which is distributed as shown in Figure 2 , and the current monitoring signal v1 ij (80°C, t) of each piezoelectric sheet pair in the current structure under the non-uniform temperature field with the highest temperature of 80°C is collected, and dispersion compensation processing is performed to obtain Then, based on the signal at 15°C in the database, temperature compensation processing is performed to obtain

[0138] In step S5, it specifically includes:

[0139] According to the wave packet distribution of the database reference signal after temperature compensation processing, segmented processing is performed to construct a segmented database, and the current monitoring signal after compensation processing is segmented and matched with the reference signal at different temperatures in the segmented database, the reference signal with the maximum correlation in the segment is taken as the segment reference signal obtained by matching, and the segment reference signals are spliced to obtain the reconstructed reference signal v0(t).

[0140] S6: Perform signal difference processing based on the reconstructed reference signal v0(t) in step S5 and the current monitoring signal after compensation processing in step S4 to obtain the damage scattering signal s DC-TC (t);

[0141] As shown in Figure 6 , the current monitoring signal after compensation processing of each piezoelectric sheet pair is optimally segmented and matched with the reference signal in the database to reconstruct the optimal reference signal v0 ij (t), it can be seen that the database temperatures selected by each segment matching are inconsistent, and the current monitoring signal is subtracted from v0 ij (t) to obtain the damage scattering signal

[0142] The temperature compensation effect is shown by taking the signals in P3-P7 as an example. As shown in FIG. 6, due to the huge temperature difference of 65℃, Figure 7 As shown in FIG. 7, the amplitude and phase of the wave packets are greatly deviated, and the damage scattering signal obtained by directly subtracting the signals is As shown in FIG. 8, compared with The amplitude and phase of the wave packets are greatly deviated, and the damage scattering signal obtained by directly subtracting the signals is As shown in FIG. 9, compared with Figure 8 A huge residual boundary reflection occurs, which causes the damage information to be submerged. After the temperature compensation processing, as shown in FIG. 10, As shown in FIG. 11, the wave packets of the reference signal v0 Figure 9 (t) in the whole time domain segment are well matched, and the differences in the amplitude and phase of the wave packets caused by the temperature are effectively eliminated, as shown in FIG. 12, The damage scattering wave packets in FIG. 13 are effectively highlighted. 37 Figure 10

[0143] S7: Beam synthesis processing is performed on the damage scattering signals: for each scanning angle θ, the beam synthesis is performed on all the damage scattering signals s DC-TC (t) obtained in step S6 to obtain the beam synthesis signals of each scanning angle The frequency domain pre-interpolation processing is performed on the damage scattering signals of each piezoelectric patch pair to obtain The beam synthesis processing is performed on the damage scattering signals of each piezoelectric patch pair after the frequency domain pre-interpolation processing at all angles to obtain Figure 11 The comparison diagram of the beam synthesis results ss1(140°, 80℃, t) of the damage angle 140° and the temperature difference of 65℃ and the beam synthesis results ss1(140°, 15℃, t) of the same temperature of 15℃ at normal temperature can be observed. It can be observed that the difference between ss1(140°, 80℃, t) and ss1(140°, 15℃, t) is large, and there are multiple wave packets with huge amplitudes. After the temperature compensation processing, the frequency domain beam synthesis result is basically consistent with ss1(140°, 15℃, t), as shown in FIG. 18. An extended serious wave packet appears at the theoretical position of the D scattering wave packet. Figure 12 The frequency dispersion compensation processing is performed on the beam synthesis signals of each angle to obtain

[0144] Figure 13 ​​​​​For the comparison of the beam synthesis results ss2(140°, 80℃, t) after dispersion compensation and the beam synthesis results ss2(140°, 15℃, t) at normal temperature 15℃, it can be observed that ss2(140°, 80℃, t) appears larger noise near the theoretical position of D scattering wave packet. After temperature compensation processing, as shown in Figure 14 and ss2(140°, 15℃, t) are both in the theoretical position of D scattering wave packet, a significantly compressed wave packet appears.

[0145] Step S7 specifically includes the following steps:

[0146] S71: performing frequency domain pre-interpolation processing on the obtained damage scattering signals to obtain

[0147] In step S71, the frequency domain pre-interpolation processing specifically includes the following steps:

[0148] S711: performing Fourier transform on to obtain

[0149] S712: performing frequency domain pre-interpolation processing on

[0150] wherein, is the frequency domain pre-interpolation processing result, is the inverse function of Ω1(ω);

[0151] S713: performing inverse Fourier transform on to obtain

[0152] S72: performing delay stacking according to the scanning angle θ on the obtained in step S71, and then performing inverse Fourier transform to obtain the time domain beam synthesis signal The formula is as follows:

[0153]

[0154] S73: performing dispersion compensation processing on to obtain

[0155] S8: calculating the dense array damage monitoring imaging result according to the beam synthesis signals at each scanning angle obtained in step S7. The dense array damage monitoring imaging result is calculated according to the beam synthesis signals at each angle after dispersion compensation processing.​​

[0156] Figure 15 For the result of the damage imaging of the phased array at the same temperature of 15℃, the "△" in the figure is the real damage position. It can be seen that a clear focus bright spot appears at the real damage position. Figure 16 For the result of the damage imaging of the phased array with a temperature difference of 65℃, it can be seen that no focus point can be seen at the real damage position, but at the positions of (200, 0) and (-200, 0), due to the influence of temperature on the boundary reflection, a clear focus and pixel value huge false image appears, thereby causing the damage information to be submerged. Figure 17 For the result of the damage imaging of the phased array after temperature compensation processing, it can be observed that the huge false image at the boundary caused by temperature is obviously suppressed, and similar to the result of the damage imaging of the phased array at the same temperature of 15℃, a clear and focused bright spot appears at the real damage position.

[0157] In step S8, specifically, the region imaged by the dense array is divided into 1mm x 1mm squares, and each square is a pixel point in the damage imaging image;

[0158] Each square is assumed to be a potential damage point, the angle θ and the distance R of the square relative to the center of the dense array are determined, and the calculation formula of the angle θ is:

[0159] θ = arctan(y / x)

[0160] wherein arctan() is the inverse tangent function, θ is rounded when calculated, and x and y are the horizontal and vertical coordinates of the square in the Cartesian coordinate system;

[0161] The calculation formula of the distance R is:

[0162]

[0163] The beam synthesis signal at the angle θ is determined according to the distance R The wave packet amplitude scattered from the square, and the amplitude is taken as the pixel value of the square, and finally the imaging result corresponding to the scanning region is obtained. When the wave packet amplitude is determined according to the distance R, the data point position of the ultrasonic guided wave signal corresponding to the square needs to be calculated, and the calculation formula is:

[0164] n = Rf a / 0.5c g

[0165] wherein n ∈ [1, N] is the number of signal data points, f a is the signal sampling rate.

[0166] Therefore, the present application adopts the above-mentioned dispersion wave dense array damage monitoring method under large-range non-uniform temperature variation, combines frequency domain beam synthesis and dispersion compensation to solve the problems of interference of ultrasonic wave dispersion on the process of dense array beam synthesis and resolution reduction caused by wave packet expansion, and solves the non-uniform problems of amplitude and phase variation of each wave packet caused by large-range non-uniform temperature variation, compensates the non-uniform phase variation through the powerful flexible regulation ability of time domain bending, matches the signals at each temperature in the database with the current monitoring signals in segments to solve the non-uniform problem of amplitude variation, and finally realizes the dispersion ultrasonic wave dense array damage monitoring under large-range non-uniform temperature variation.

[0167] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application rather than limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for monitoring damage to a dissipative guided wave compact array under large-scale non-uniform environmental temperature variations, characterized in that: Includes the following steps: S1: Deploy sensors on the surface of the structure to be monitored. Several piezoelectric elements are arranged in a linear dense array and numbered from 1 to... ; S2: Establish a reference database under different ambient temperatures. Under conditions of uniform temperature variation, collect reference signals of the health status of the tested structure at different ambient temperatures. Build a database; in, Indicates the first The first piezoelectric element acts as an exciter, the second... A pair of piezoelectric elements, consisting of individual piezoelectric elements used as sensors, and , , , For temperature variables, It is a time variable; Step S2 specifically includes the following steps: S21: Acquire ultrasonic guided wave reference signals of each piezoelectric pair under the healthy state of the structure under test at different uniform temperatures. ; S22: Obtained by performing dispersion compensation processing on the reference signals at each uniform temperature. ; The dispersion compensation process in step S22 specifically includes: S221: Obtain the linearized wavenumber curve: in, For linearized wavenumber curves, For temperature The wavenumber curve of the original dispersion of the guided wave mode corresponding to the ultrasonic guided wave signal in the lower structure. Angular frequency, The center angular frequency of the ultrasonic guided wave signal. For the selected waveguide mode in The group velocity below; S222: Calculate the frequency domain interpolation mapping sequence: in, For the calculated frequency domain interpolation mapping sequence, for The inverse function; S223: Yes Perform frequency domain interpolation: in, This is the result of frequency domain interpolation. for The Fourier transform result; S224: Yes Performing the inverse Fourier transform yields ; S23: Using a normal temperature signal Using this as a reference, temperature compensation processing is performed on signals at other temperatures to obtain a compensated reference signal database. ,in At room temperature; In step S23, the temperature compensation process specifically includes: by For reference, Temperature compensation processing was performed to obtain The details are as follows: according to Each signal data point and Each signal data point Seeking and Distance matrix between ,in, for and Number of data points ; Its matrix elements The calculation is as follows: in, express and The Euclidean distance between them; Find the distance matrix Its matrix elements The calculation is as follows: in, This indicates the maximum value selection operation. This is a parameter for adjusting the bending range, and its value range is [value range missing]. ; Determine according to the following recursive formula and Cumulative distance matrix between : in, for elements, , This indicates the minimum value selection operation; Will and The optimal time-bending path between them is defined as a representation and The sequence of ordered pairs representing the optimal matching mappings between data points is represented as: ; in, , ordered pairs Indicates will The Middle Data points and The Middle Data points Matching , ;exist China and Israel Starting point The endpoint is determined by the following iterative search method: Reverse determination ,in, , , ; In order each ordered pair ,Will The Middle Data points Assigned as the first in the new current signal From the data points, we obtain: in, This serves as the reference signal in the temperature-compensated database. S24: According to The wave packet distribution in the signal is segmented to obtain a segmented reference signal database. S3: Collect the current monitoring signal of the structure under the current ambient temperature. Under the condition of non-uniform change of the current ambient temperature, the current monitoring signal of the measured structure is collected as follows: ,in, This represents the highest temperature of the structure under test under the current non-uniform temperature change conditions. S4: Perform compensation processing on the current monitoring signal obtained in step S3, and adjust the current monitoring signal of the acquired structure under test. First, dispersion compensation is performed to obtain... Then, temperature compensation processing is performed to obtain... ; S5: Based on the database established in step S2 and the current monitoring signal after compensation processing in step S4, reconstruct the reference signal. ; Based on the database reference signal after compensation processing The wave packet distribution is segmented to construct a segmented database, and then the current monitoring signal after compensation processing is used. The reference signal is segmented and matched with reference signals at different temperatures in the segmented database. The reference signal with the highest correlation in each segment is used as the segment reference signal. The segment reference signals are then concatenated to obtain the reconstructed reference signal. ; S6: Based on the reference signal reconstructed in step S5 and the current monitoring signal after compensation processing in step S4 Damage scattering signal is obtained by performing signal difference processing. ; S7: Beamforming processing of the damage scattering signal: for each scanning angle All damage scattering signals are obtained using step S6. Beamforming is performed to obtain beamformed signals at various scanning angles. ; Step S7 specifically includes the following steps: S71: The obtained damage scattering signal Perform frequency domain pre-interpolation to obtain ; S72: The result obtained in step S71 According to the scanning angle Delay superposition and then inverse Fourier transform are performed to obtain the time-domain beamforming signal. The formula is as follows: S73: Yes Dispersion compensation processing is performed to obtain ; S8: Based on the beamforming signals at each scanning angle obtained in step S7 The results of dense array damage monitoring imaging were calculated. Step S8 specifically includes dividing the dense array imaging area into 1mm×1mm squares, where each square is a pixel in the damage imaging map. Assuming each square represents a potential damage point, determine the angle of each square relative to the center of the compact matrix. and distance ,angle The calculation formula is: in, It is the arctangent function. Rounding is performed during calculation. and These are the x and y coordinates of the square in the Cartesian coordinate system; distance The calculation formula is: According to distance Determine the angle Lower beam synthesis signal The amplitude of the wave packet scattered from the grid is used as the pixel value of the grid to obtain the final imaging result corresponding to the scanned area, based on the distance. Determining the wave packet amplitude requires finding the location of the ultrasonic guided wave signal data point corresponding to that square. The calculation formula is as follows: in, For the number of signal data points, This represents the signal sampling rate.

2. The method for monitoring damage to a dissipative guided wave compact array under large-scale non-uniform environmental temperature variations according to claim 1, characterized in that: In step S71, the frequency domain pre-interpolation process specifically includes the following steps: S711: Yes Perform Fourier transform to obtain ; S712: Yes Perform frequency domain pre-interpolation: ; in, This is the result of frequency domain pre-interpolation. for The inverse function; S713: Yes Performing the inverse Fourier transform yields .

3. The method for monitoring damage to a dissipative guided wave compact array under large-scale non-uniform environmental temperature variations according to claim 1, characterized in that: The range of values ​​for the number of piezoelectric elements Q is as follows: .

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