CN111537610A - A sensor array optimization method for damage localization of metal curved plates - Google Patents

Abstract

The invention discloses a sensor array optimization method for damage location of a metal curved plate, comprising the following steps: step S1, designing a metal curved plate, and calculating the dispersion curve of the metal curved plate; step S2, designing at least two groups of Ultrasonic guided wave sensor array; step S3, obtain and record the center frequency and bandwidth of the ultrasonic guided wave sensor; step S4, the ultrasonic guided wave signal is transmitted to the metal curved plate through the signal generator and amplifier in turn, and different ultrasonic guided waves are saved through the oscilloscope The guided wave signal of the sensor array; Step S5, perform centralization and normalization preprocessing on the obtained guided wave signal; Step S6, perform bandpass filtering on the preprocessed guided wave signal to improve the signal-to-noise of the guided wave signal ratio; Step S7, determine the ultrasonic guided wave sensor array with the optimal damage location accuracy. According to the present invention, it combines the elliptical damage localization method and the data noise reduction processing technology to effectively improve the damage localization accuracy through the selection and optimization of the sensor array.

Description

A sensor array optimization method for damage localization of metal curved plates

technical field

The invention relates to the field of ultrasonic guided wave nondestructive testing, in particular to a sensor array optimization method for damage location of a metal curved plate.

Background technique

Pressure vessels are special equipment that is under pressure and has the risk of explosion. It is widely used in aerospace, underwater submarines and other important industrial fields of national defense and military industries. At the same time, this equipment is also widely involved in the field of people's livelihood and is in great demand. However, extreme working environments such as high/low temperature and high pressure can lead to leakage or rupture of pressure vessels, which greatly endangers the safety of people's lives and properties. After research and statistical analysis, the most likely part of the cylindrical pressure vessel to fail is its barrel, and the curved plate structure can be effectively analyzed as a simplified structure of the pressure vessel barrel. Therefore, it is necessary to study the health status of the metal curved plate structure. to simulate the failure analysis of cylindrical pressure vessels.

At present, the commonly used metal curved plate structural health testing methods can be divided into passive testing and active testing. The passive methods mainly include acoustic emission testing and infrared nondestructive testing. These two methods are not only susceptible to noise interference, but also rely on rich databases and On-site inspection experience, damage qualitative and quantitative rely on other non-destructive testing methods; active testing methods include ultrasonic testing, penetrant testing, optical fiber monitoring, magnetic particle testing, eddy current method and guided wave testing technology.

Compared with other active detection methods, ultrasonic guided wave detection technology has the advantages of long propagation distance, low attenuation, overall and large-scale detection, and online monitoring under the condition of equipment operation. The monitoring area is wide, so using the guided wave-based curved plate damage monitoring technology can effectively monitor the damage in real time.

In recent decades, ultrasonic guided wave detection technology has developed rapidly, and its dispersion characteristics and signal characteristics are important research objects for equipment damage detection. According to the structural characteristics of the curved plate, the Lamb wave-based damage identification method can be used in its damage monitoring. Lamb wave is a form of guided wave in the plate structure proposed by the British mechanician Lamb in 1917. During detection, the waveform is actively excited in the structure, and the signal received by the sensor contains information such as the damage location and degree of damage of the structure. By performing data analysis and feature extraction on the Lamb wave signal, the damage information can be obtained.

Due to the small size of the common damage and the small change of the guided wave signal received by the sensor, the damage information in the signal may be annihilated, which makes it difficult to determine the damage location. The guided wave signal is different, and the time of flight of the damaged signal wave packet can be obtained through the difference signal, and then its flight distance can also be obtained. Finally, an ellipse is drawn with the driver and sensor as the focus, and the damage location is located on the elliptical trajectory. By arranging multiple sensors, the intersection of multiple elliptical trajectories can be obtained, that is, the location of the damage. This is the ellipse damage localization algorithm. Therefore, the selection and arrangement of the number of sensors is the key to the research.

In view of the various damage forms in the metal curved plate structure, and the damage location is often difficult to determine, in order to achieve the accurate localization analysis of the curved plate damage, it is necessary to develop a sensor array optimization method for the metal curved plate damage location to reasonably optimize the ultrasonic guide. Wave sensor array form to solve the above shortcomings.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the main purpose of the present invention is to provide a sensor array optimization method for damage location of metal curved plates, which combines the elliptical damage location method and the data noise reduction processing technology. The screening optimization can effectively improve the accuracy of damage location. The present invention considers that both the number and position of the sensors will affect the damage localization accuracy, so multiple sensor arrays with different numbers and positions are considered.

In order to achieve the above objects and other advantages according to the present invention, there is provided a sensor array optimization method for damage localization of metal curved plates, comprising the following steps:

Step S1, design the physical parameters and geometric parameters of the metal curved plate, open a simulated damage hole on the metal curved plate, and calculate the frequency dispersion of the metal curved plate according to the physical parameters and geometric parameters of the metal curved plate curve;

Step S2, design at least two groups of ultrasonic guided wave sensor arrays on the side wall of the metal curved plate, each group of the ultrasonic guided wave sensor arrays includes at least three ultrasonic guided wave sensors arranged around the simulated damage hole, two by two. The number of ultrasonic guided wave sensors in the ultrasonic guided wave sensor array is different;

Step S3, sweeping the ultrasonic guided wave sensor of each group of the ultrasonic guided wave sensor array to obtain and record the center frequency and bandwidth of the ultrasonic guided wave sensor;

Step S4, the ultrasonic guided wave signal is transmitted to the metal curved plate through the signal generator and the amplifier in turn, and the guided wave signal of different ultrasonic guided wave sensor arrays is saved by the oscilloscope;

Step S5, performing centralization and normalization preprocessing on the obtained guided wave signal;

Step S6, performing bandpass filtering on the preprocessed guided wave signal, and further using wavelet noise reduction and SVD singular value decomposition noise reduction data processing methods to improve the signal-to-noise ratio of the guided wave signal;

Step S7, compiling a damage localization method for the metal curved plate, performing damage localization based on different ultrasonic guided wave sensor arrays, analyzing and comparing the damage localization accuracy under different ultrasonic guided wave sensor arrays, and finally determining the ultrasonic guide with the best damage localization accuracy. wave sensor array.

Optionally, the damage extension direction of the simulated damage hole forms an included angle with the axis of the metal curved plate, thereby increasing the influence of the axial and circumferential damage on the guided wave signal at the same time, and the angle of the included angle is 20. °～90°; the simulated damage hole penetrates the inner and outer side walls of the metal curved plate to increase the influence on the guided wave signal, and the metal curved plate without simulated damage hole is used as the damage location reference.

Optionally, the simulated damage hole is located at the geometric center of the metal curved plate.

Optionally, step S1 is to accurately calculate the dispersion curve of the metal curved plate, using the Lamb wave dispersion curve control equation in the metal curved plate, and its expression is:

和

Among them, u and v are the displacement components perpendicular to each other, η is the shortest distance from the observation point to the center line of the curved plate, ε is a small dimensionless parameter, σ is the arc length of the center line of the curved plate, and k _l is the symmetry equation Rayleigh -Solution of Lamb equation, ξ=εσ, α=α(ξ),

and

Optionally, in step S2, the ultrasonic guided wave sensors in each group of the ultrasonic guided wave sensor arrays are evenly distributed on a circumference with the simulated damage hole as the center.

Optionally, in step S3, the center frequency and bandwidth of the ultrasonic guided wave sensor are obtained by frequency sweep, which are used for signal excitation frequency selection, guided wave velocity selection and bandpass filtering parameter setting.

Optionally, the SVD singular value decomposition noise reduction method in step S6 includes:

Step T1, transform the guided wave signal to construct a matrix B of m*n;

Step T2, decompose the matrix B into the form of B=UΣV ^T ;

为：

以实现SVD奇异值分解降噪。Among them, U(m*r) is the left singular matrix, V(n*r) is the right singular matrix, r is the rank of matrix B, Σ is the diagonal matrix, and the singular value of matrix B on the diagonal is from the largest to a small arrangement; only the first k (k<r) larger singular value components of the matrix are retained, so that the denoised matrix can be reconstructed.

for:

In order to achieve SVD singular value decomposition noise reduction.

Optionally, in step 7, the wave velocity selection of the elliptical damage localization method is obtained according to the dispersion curve; the guided wave signal used for damage localization is a high signal-to-noise ratio guided wave signal that has undergone preprocessing and noise reduction data processing; the elliptical damage localization method requires The unit segmentation is adjusted according to the sensor array; the damage location error formula is as follows:

One of the above technical solutions has the following advantages or beneficial effects: the present invention comprehensively uses the elliptical damage localization method and the data noise reduction processing method to optimize the arrangement of the sensor array for damage localization of the metal curved plate. The curved plate with a certain angle in the plate axial direction is damaged, and metal curved plates with different curvature radii are designed; five kinds of ultrasonic guided wave sensor initial arrays are designed and arranged; after the centralization and normalization pretreatment, two kinds of The noise reduction method was used, and the defect localization research was carried out. Finally, the optimal sensor array was selected by comparing the damage localization accuracy. On the one hand, the method analyzes the damage localization ability of the sensor array to different degrees of damage and different curvature radii, and incorporates a complete data processing method to improve the signal-to-noise ratio of the signal; The influence of damage localization accuracy can be more reasonable and effective to obtain the optimal sensor array.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, rather than limit the present invention. in:

FIG. 1 is a flowchart of a sensor array optimization method for damage location of metal curved plates proposed according to an embodiment of the present invention;

2 is a schematic diagram of a metal curved plate and a damage form in a sensor array optimization method for damage location of a metal curved plate proposed according to an embodiment of the present invention;

3 is a graph of the dispersion curve of a metal curved plate in a sensor array optimization method for damage location of a metal curved plate proposed according to an embodiment of the present invention;

4 is a diagram of the first ultrasonic guided wave sensor array in the sensor array optimization method for damage location of metal curved plates proposed according to an embodiment of the present invention;

5 is a diagram of a second ultrasonic guided wave sensor array in the sensor array optimization method for damage location of metal curved plates proposed according to an embodiment of the present invention;

6 is a diagram of a third ultrasonic guided wave sensor array in the sensor array optimization method for damage location of metal curved plates proposed according to an embodiment of the present invention;

7 is a diagram of the fourth ultrasonic guided wave sensor array in the sensor array optimization method for damage location of metal curved plates proposed according to an embodiment of the present invention;

8 is a diagram of the fifth ultrasonic guided wave sensor array in the sensor array optimization method for damage location of metal curved plates proposed according to an embodiment of the present invention;

9 is a diagram of an ultrasonic guided wave signal before signal processing in a sensor array optimization method for damage location of a metal curved plate proposed according to an embodiment of the present invention;

10 is a diagram of an ultrasonic guided wave signal after signal processing in a sensor array optimization method for damage location of a metal curved plate proposed according to an embodiment of the present invention;

FIG. 11 is a schematic diagram of a device structure of an ultrasonic guided wave signal control system in a sensor array optimization method for damage location of a metal curved plate proposed according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the drawings, the shapes and dimensions may be exaggerated for clarity, and the same reference numerals will be used throughout the drawings to refer to the same or like parts.

Unless otherwise defined, technical or scientific terms used herein should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The terms "first", "second" and similar terms used in the description of the patent application and the claims of the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Likewise, words such as "a," "an," or "the" do not denote a limitation of quantity, but rather denote the presence of at least one. Words like "include" or "include" mean that the elements or items appearing before "including" or "including" cover the elements or items listed after "including" or "including" and their equivalents, and do not exclude other component or object. "Up", "Down", "Left", "Right", etc. are only used to represent the relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

In the following description, terms such as center, thickness, height, length, front, back, rear, left, right, top, bottom, upper, lower, etc. are defined relative to the configurations shown in the various figures. , in particular, "height" corresponds to the size from top to bottom, "width" corresponds to the size from left to right, "depth" corresponds to the size from front to back, they are relative concepts, so it is possible to These or other orientations should not be construed as limiting terms because they vary accordingly in different positions and different usage states.

Terms referring to attachment, coupling, etc. (eg, "connected" and "attached") refer to the fixed or attached relationship, as well as the movable or rigid attachment or relationship of these structures to each other, directly or indirectly, through intervening structures, unless The other way is explicitly stated.

1, it can be seen that the overall process of the sensor array optimization method for metal curved plate damage location according to the present invention is to design the curved plate damage, draw the dispersion curve, and arrange the initial sensor array. , Sensor frequency sweep, setting signal generator-amplifier-oscilloscope, centralization and normalization preprocessing, filtering and noise reduction processing, damage location based on high signal-to-noise ratio signals, and optimal formation selection. Specifically, the sensor array optimization method for metal curved plate damage location according to the present invention includes the following steps:

Step S1, design the physical parameters and geometric parameters of the metal curved plate, open a simulated damage hole on the metal curved plate, and calculate the frequency dispersion of the metal curved plate according to the physical parameters and geometric parameters of the metal curved plate curve. The damage extension direction of the simulated damage hole forms an included angle with the axis of the metal curved plate, thereby increasing the influence of the axial and circumferential damage on the guided wave signal at the same time, and the angle of the included angle is 20°～90° ; The simulated damage hole penetrates the inner and outer side walls of the metal curved plate to increase the influence on the guided wave signal, and the metal curved plate without simulated damage hole is used as the damage location reference.

In the embodiment shown in FIG. 2 , the pressure vessel adopts a 30CrMo steel metal curved plate with a thickness of 5 mm, the metal curved plate is at least partially bent into a cylindrical shape and the projection on the horizontal plane is a rectangle, and the simulated damage hole is opened in the metal The center of the curved plate is located on the center line of the metal curved plate, and the angle between the damage extension direction of the simulated damage hole and the axis of the curved plate is 45°. In the specific implementation process, according to the thickness of the metal curved plate, the A simulated damage hole with a damage depth of 5mm is designed on the curved plate. In order to accurately draw the dispersion curve of the curved plate as shown in Figure 3, the governing equation of the Lamb wave dispersion curve in the curved plate is used, and its expression is:

和

根据上述方程绘制得到图3所示的频散曲线，频散特性是指超声导波在在波导中传播时其波速随频率变化的现象，频散曲线常用于描述导波的频散特性，其通常以速度-频率曲线进行表述。从图3中可以看出，曲板中的频散特性曲线具有下列特点：图中每一条曲线均代表一种导波模态，对于同一模态的超声导波而言，其波速会随着频率的变化而发生改变，即存在着频散现象；曲板中传播的导波有两类模态：反对称模态A、对称模态S，而且随着频率的增加，导波的模态数量也逐渐增加，如：反对称模态由零阶A0，增加至A1、A2；对称模态由零阶S0，增加至S1、S2。where u and v are displacement components that are perpendicular to each other, η is the shortest distance from the observation point to the centerline of the curved plate, ε is a small dimensionless parameter, σ is the arc length of the centerline, and k _l is the Rayleigh-Lamb symmetry equation The solution of the equation, ξ=εσ, α=α(ξ),

and

The dispersion curve shown in Figure 3 is drawn according to the above equation. The dispersion characteristic refers to the phenomenon that the wave velocity of the ultrasonic guided wave changes with the frequency when it propagates in the waveguide. The dispersion curve is often used to describe the dispersion characteristic of the guided wave. Usually expressed as a speed-frequency curve. As can be seen from Figure 3, the dispersion characteristic curve in the curved plate has the following characteristics: each curve in the figure represents a guided wave mode, and for the ultrasonic guided wave of the same mode, the wave speed will vary with The frequency changes, that is, there is a dispersion phenomenon; the guided wave propagating in the curved plate has two modes: anti-symmetric mode A, symmetric mode S, and as the frequency increases, the mode of the guided wave The number also increases gradually, such as: the antisymmetric mode increases from zero-order A0 to A1 and A2; the symmetric mode increases from zero-order S0 to S1 and S2.

Step S2, design at least two groups of ultrasonic guided wave sensor arrays on the side wall of the metal curved plate, each group of the ultrasonic guided wave sensor arrays includes at least three ultrasonic guided wave sensors arranged around the simulated damage hole, two by two. The number of ultrasonic guided wave sensors in the ultrasonic guided wave sensor array is different. In the actual implementation process, piezoelectric ceramic sensors (PZT) can be used to arrange five ultrasonic guided wave sensor arrays with different numbers and positions of sensors as shown in Figures 4 to 8. Specifically, because the ultrasonic guided wave sensors The difference in the number and position has an impact on the accuracy of damage location, so there are five initial sensor arrays shown in the embodiments in Figures 4 to 8, namely: the first type - triangle array, the second type - quadrilateral array, The third type of pentagonal array, the fourth type - hexagonal array and the fifth type - octagonal array, all ultrasonic guided wave sensors have the same distance from the simulated damage hole, which is 125mm, that is, the ultrasonic guided wave sensor in each group has the same distance of 125mm. The ultrasonic guided wave sensors in the guided wave sensor array are evenly distributed on the circle with the simulated damage hole as the center and the radius of 125mm.

Step S3, sweep the frequency of each group of ultrasonic guided wave sensors of the ultrasonic guided wave sensor array to obtain and record the center frequency and bandwidth of the ultrasonic guided wave sensor. The center frequency and bandwidth of the ultrasonic guided wave sensor are obtained by sweeping frequency, which are used for signal excitation frequency selection, guided wave velocity selection and bandpass filtering parameter setting. The specific implementation process is to sweep the frequency of the selected PZT sensor, and obtain its center frequency as 210kHz, that is, the damage localization effect of the sensor is better at this frequency. And the bandwidth of the sensor is 160kHz-260kHz, and the signal outside the bandwidth needs to be filtered out.

Step S4, the ultrasonic guided wave signal is transmitted to the metal curved plate through the signal generator and the amplifier in sequence, and the guided wave signals of different ultrasonic guided wave sensor arrays are saved by the oscilloscope. Specifically, referring to the illustration in FIG. 11 , it can be seen that the ultrasonic guided wave signal control system includes: a function generator 1 , an amplifier 2 , an oscilloscope 3 , a computer 4 , a curved board 5 , and a sensor array 6 . The computer 4 stores a signal routing program, a data signal holding program and a loss diagnosis and positioning program, which realizes fully automatic signal excitation, reception, storage and processing.

In step S5, centering and normalizing preprocessing is performed on the obtained guided wave signal. The obtained guided wave signal often drifts due to equipment hardware, so it needs to be centralized. The equation used is: x←x-E(x), where E(x) is the mean value of the guided wave signal.

The maximum and minimum normalization equations used are:

Among them, x is the original data, y is the normalized transformed value, and Max and Min are the maximum and minimum values of the guided wave signal, respectively.

In step S6, band-pass filtering is performed on the preprocessed guided wave signal, and wavelet noise reduction and SVD singular value decomposition noise reduction data processing methods are further used to improve the signal-to-noise ratio of the guided wave signal. In the specific implementation process, the SVD singular value decomposition noise reduction method includes:

Step T1, transform the guided wave signal to construct a matrix B of m*n;

Step T2, decompose the matrix B into the form of B=UΣV ^T ;

为：

实现SVD奇异值分解降噪。根据扫频结果，通过高通、低通滤波处理保留带宽范围在160kHz–260kHz的信号，并通过小波降噪及SVD奇异值分解对信号进行降噪处理，提高导波信号信噪比。数据处理前后的对比如图9、图10所示，图9为实验获得的超声导波信号振幅-时间曲线，表示曲板结构中导波信号幅值随时间的变化趋势，该曲线通过示波器采集直接得到；对图9中的曲线进行SVD奇异值分解降噪数据处理后可获得图10曲线，可以发现经过降噪处理的曲线更加平滑，噪声信号得到了有效的抑制，由此可见，数据处理操作有效地滤除了信号噪声，提高了信号质量。Among them, U(m*r) is the left singular matrix, V(n*r) is the right singular matrix, r is the rank of matrix B, Σ is the diagonal matrix, and the singular value of matrix B on the diagonal is from the largest According to the results in the curved board, only the first 7 main components of the larger singular value of the matrix are retained, and the denoised matrix is reconstructed

for:

Implement SVD singular value decomposition noise reduction. According to the frequency sweep results, the signal with a bandwidth range of 160kHz-260kHz is retained by high-pass and low-pass filtering, and the signal is denoised by wavelet noise reduction and SVD singular value decomposition to improve the signal-to-noise ratio of the guided wave signal. The comparison before and after data processing is shown in Figure 9 and Figure 10. Figure 9 is the amplitude-time curve of the ultrasonic guided wave signal obtained in the experiment, which represents the change trend of the amplitude of the guided wave signal in the curved plate structure with time. The curve is collected by an oscilloscope. It can be directly obtained; the curve in Figure 9 can be obtained after SVD singular value decomposition noise reduction data processing, and the curve in Figure 10 can be obtained. It can be found that the curve after noise reduction processing is smoother, and the noise signal has been effectively suppressed. It can be seen that the data processing The operation effectively filters out signal noise and improves signal quality.

Step S7, compiling a damage localization method for the metal curved plate, performing damage localization based on different ultrasonic guided wave sensor arrays, analyzing and comparing the damage localization accuracy under different ultrasonic guided wave sensor arrays, and finally determining the ultrasonic guide with the best damage localization accuracy. wave sensor array.

Based on the principle of ellipse damage localization, the defect localization algorithm in the curved plate is compiled. The calculation formula is:

S=TD+DR=c _g t

where c _g is the group velocity of the guided wave signal, which is obtained from the dispersion curve drawn in step 1; when the excitation sensor T excites the guided wave signal and propagates to the defect D, it interacts with it, resulting in a scattering phenomenon, which is then captured by the receiving sensor R Scattered signal; t is the propagation time of the process, which can be obtained from the guided wave time domain signal received by the oscilloscope. Then the defect is located on an elliptical trajectory with T and R as the foci and S as the major axis. An elliptical trajectory can be determined by any pair of sensors, and multiple elliptical trajectories can be determined through multiple pairs of sensor networks in the sensor array. The intersection of these elliptical trajectories is the location of the defect. Since five sensor arrays with different numbers and positions are used in this example, the algorithm needs to be adjusted according to the array. Then, the curved plates with different depth damage and different curvatures in this example are positioned, and the positioning error formula is as follows:

The damage location errors shown in Table 1 can be obtained. According to the average value of the axial and axial positioning errors, the average positioning error can be obtained. It can be seen that when the sensor array is hexagonal, the circumferential error and the axial error are the smallest, and the average error is only 1.27%. On this basis, the optimal sensor formation is selected as the hexagonal formation. This example points out that it is not that the more the number of sensors, the higher the damage location accuracy. When the number of sensors is too large, it will affect the propagation of the guided wave signal, which in turn affects the damage location accuracy. Therefore, the number and location of the sensors need to be comprehensively considered.

Table 1 Damage location error

The number of apparatuses and processing scales described here are intended to simplify the description of the present invention. Applications, modifications and variations to the present invention will be apparent to those skilled in the art.

Although the embodiment of the present invention has been disclosed as above, it is not limited to the application listed in the description and the embodiment, it can be applied to various fields suitable for the present invention, and those skilled in the art can easily Additional modifications are implemented, therefore, the invention is not limited to the specific details and illustrations shown and described herein without departing from the general concept defined by the appended claims and the scope of equivalents.

Claims (8)

1. A sensor array optimization method for damage positioning of a metal curved plate is characterized by comprising the following steps:

step S1, designing physical parameters and geometric parameters of a metal bent plate, forming simulated damage holes on the metal bent plate, and calculating a frequency dispersion curve of the metal bent plate according to the physical parameters and the geometric parameters of the metal bent plate;

step S2, designing at least two groups of ultrasonic guided wave sensor arrays on the side wall of the metal curved plate, wherein each group of ultrasonic guided wave sensor arrays comprises at least three ultrasonic guided wave sensors arranged around the simulated damage hole, and the number of the ultrasonic guided wave sensors in every two ultrasonic guided wave sensor arrays is different;

step S3, sweeping frequency of the ultrasonic guided wave sensors of each group of ultrasonic guided wave sensor array, and obtaining and recording the center frequency and bandwidth of the ultrasonic guided wave sensors;

step S4, the ultrasonic guided wave signals are conducted to the metal curved plate through the signal generator and the amplifier in sequence, and the guided wave signals of different ultrasonic guided wave sensor arrays are stored through the oscilloscope;

step S5, the obtained guided wave signal is processed with centralization and normalization pretreatment;

step S6, performing band-pass filtering processing on the preprocessed guided wave signals, and further improving the signal-to-noise ratio of the guided wave signals by adopting a wavelet de-noising and SVD singular value decomposition de-noising data processing method;

and step S7, compiling a damage positioning method of the metal curved plate, carrying out damage positioning based on different ultrasonic guided wave sensor arrays, analyzing and comparing damage positioning accuracy under different ultrasonic guided wave sensor arrays, and finally determining the ultrasonic guided wave sensor array with the optimal damage positioning accuracy.

2. The sensor array optimization method for metal curved plate damage positioning as claimed in claim 1, wherein the damage extending direction of the simulated damage hole forms an included angle with the axis of the metal curved plate, thereby increasing the influence of axial and circumferential damages on the guided wave signal, and the angle of the included angle is 20-90 °; the simulation damage hole penetrates through the inner side wall and the outer side wall of the metal curved plate to increase the influence on the guided wave signal, and the metal curved plate without the simulation damage hole is used as a damage positioning reference.

3. The sensor array optimization method for metal curved plate damage localization as claimed in claim 1, wherein the simulated damage hole is located at a geometric center of the metal curved plate.

4. The sensor array optimization method for damage localization of a metal curved plate as claimed in claim 1, wherein the step S1 is to accurately calculate the dispersion curve of the metal curved plate by using Lamb wave dispersion curve control equation in the metal curved plate, and the expression is:

u；

v；

wherein u and v are displacement components perpendicular to each other, η is the shortest distance from the observation point to the center line of the curved plate, which is a small dimensionless parameter, σ is the arc length of the center line of the curved plate, and k is_lIs a solution of the symmetric equation Rayleigh-Lamb equation, ξ σ, α α (ξ),

and

5. the method for optimizing the sensor array used for positioning the damage of the metal curved plate as claimed in claim 1, wherein the ultrasonic guided wave sensors in each group of the ultrasonic guided wave sensor array in the step S2 are uniformly distributed on a circumference with a simulated damage hole as a center.

6. The method for optimizing the sensor array for positioning the damage to the metal curved plate as claimed in claim 1, wherein in step S3, the center frequency and the bandwidth of the ultrasonic guided wave sensor are obtained by frequency sweeping for signal excitation frequency selection, guided wave velocity selection and bandpass filtering parameter setting.

7. The sensor array optimization method for metal curved plate damage localization as claimed in claim 1, wherein the SVD singular value decomposition noise reduction method in step S6 includes:

step T1, converting the guided wave signals to form a matrix B of m x n;

step T2, decomposing the matrix B into B ═ U Σ V^TIn the form of (a);

wherein, U (m r) is a left singular matrix, V (n r) is a right singular matrix, r is the rank number of the matrix B, sigma is a diagonal matrix, and singular values of the matrix B are arranged from large to small on the diagonal; only the first k (k) of the matrix is retained<r) are largerSingular value component, such that the de-noised matrix is reconstructed

Comprises the following steps:

to achieve SVD singular value decomposition noise reduction.

8. The sensor array optimization method for metal curved plate damage localization as claimed in claim 1, wherein in step 7, the wave velocity selection of the elliptical damage localization method is obtained according to a dispersion curve; the guided wave signal adopted by the damage positioning is a high signal-to-noise ratio guided wave signal which is subjected to preprocessing and noise reduction data processing; the ellipse damage positioning method needs to be divided according to the sensor array type adjusting unit; the lesion localization error formula is as follows:

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