Ultrasonic phased array-based method and system for fitting interlaminar bonding interface of wind turbine blade

Abstract

The application is based on the ultrasonic phased array wind power blade interlayer bonding interface fitting method and system, and belongs to the nondestructive testing technical field, comprising: configuring a detection system and initializing parameters; performing ultrasonic phased array full matrix data acquisition and preprocessing on the blade bonding part; calculating the ultrasonic wave propagation time delay based on the multilayer medium sound velocity distribution model and the ray tracing method, and generating a high-resolution glue layer-blade layer bonding interface image by using a full focusing imaging algorithm; adopting a multi-scale edge detection algorithm combining a Canny operator and a Zernike matrix to accurately extract a discrete feature point set of the bonding interface from the image; based on the feature point set, a continuous contour curve of the bonding interface is obtained by using a cubic polynomial curve fitting; and finally, the fitting curve is superimposed on the imaging result for visualization. The application effectively solves the imaging distortion problem caused by the sound velocity difference in the heterogeneous multilayer structure, and significantly improves the detection reliability of the wind power blade interlayer bonding quality.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing technology, specifically to the field of interlayer bonding quality testing of wind turbine blades, and particularly to a method and system for fitting the interlayer bonding interface of wind turbine blades based on an ultrasonic phased array. Background Technology

[0002] As the core load-bearing component of a wind turbine generator, the structural integrity of the wind turbine blade directly determines the operational safety and service life of the unit. Modern wind turbine blades mostly adopt a three-layer composite adhesive structure of "web-adhesive layer-blade layer". The web is made of industrial plastic material (such as PVC foam, PET foam), the adhesive layer is epoxy resin structural adhesive, and the blade layer is fiberglass (glass fiber reinforced composite material). The bonding interface between the adhesive layer and the blade layer is the weakest point in the mechanical structure.

[0003] During the fabrication of wind turbine blades, factors such as fluctuations in bonding process parameters and incomplete curing, or the application of fatigue loads and environmental erosion during long-term service, can easily lead to defects such as debonding, micro-voids, and interface peeling at the adhesive-blade layer bonding interface. These defects can cause stress concentration, and in severe cases, lead to interlayer failure or even overall fracture of the blade. Therefore, accurate detection and morphological fitting of the adhesive-blade layer bonding interface are crucial for evaluating the quality of wind turbine blades and ensuring the safe operation of the turbine unit.

[0004] Ultrasonic phased array full-focusing imaging technology can achieve high-resolution imaging through full-matrix data acquisition and point-by-point delay superposition. Furthermore, the multi-element collaborative operation of the phased array transducer allows for flexible adjustment of the acoustic beam direction, adapting to heterogeneous media and curved surface coupling scenarios. Based on this, a method for fitting the bonding interface of a three-layer wind turbine blade structure is proposed, combining multi-scale edge detection and curve fitting algorithms. This method effectively addresses the shortcomings of existing technologies, achieving precise quantification and quality grading of the interface morphology. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the detection of interlayer bonding interfaces of wind turbine blades, such as low imaging resolution, poor adaptability to heterogeneous media, insufficient interface fitting accuracy, and lack of quantitative quality assessment. This invention provides a method and system for fitting interlayer bonding interfaces of wind turbine blades based on ultrasonic phased array. It is applicable to wind turbine blades composed of industrial plastic web, epoxy resin structural adhesive layer, and fiberglass blade layer, and achieves accurate fitting and quality assessment of the micro-curvature bonding interface between the adhesive layer and the blade layer.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array, wherein the wind turbine blade is a three-layer composite bonding structure consisting of an industrial plastic web, an epoxy resin structural adhesive layer, and a fiberglass blade layer, the method includes the following steps: S1. Detection system configuration and parameter initialization: Configure the detection system including the ultrasonic phased array detector, array probe, robotic arm and coupling medium, and initialize the system parameters; S2. Full-matrix data acquisition and preprocessing: Control the array probe to perform full-matrix data acquisition on the interlayer bonding area of ​​the wind turbine blade, and preprocess the acquired ultrasonic echo signals; S3. Full-focus imaging and feature extraction: The ultrasonic propagation delay is calculated based on the multi-layer medium sound velocity distribution model and ray tracing method. The preprocessed full matrix data is then overlaid point by point to generate a full-focus image of the adhesive layer-blade layer bonding interface. Based on the full-focus image, a multi-scale edge detection algorithm is used to extract the discrete feature point set of the bonding interface. S4. Adhesive interface curve fitting: Based on the discrete feature point set, a curve fitting algorithm is used to fit the continuous curve of the adhesive interface. S5. Imaging visualization: The fitted bonding interface curve is superimposed onto the full-focus image for visualization display.

[0007] A further improvement of the present invention is that the preprocessing in step S2 includes: S21. Use a bandpass filter to filter the echo signal; S22. Using the reference echo signal at the web-glue interface as a reference, perform time delay correction on the signal; S23. Use wavelet threshold denoising algorithm to denoise the signal; S24. Perform coherent weighting processing on the multi-channel echo signals of the same imaging point.

[0008] A further improvement of the present invention is that the generation of the fully focused image in step S3 specifically includes: S31. Divide the imaging area into a grid; S32. Based on the acoustic characteristics of each layer of materials in the web, rubber layer and blade layer, the propagation time of ultrasonic waves from the transmitting element to the imaging point and from the imaging point to the receiving element is calculated using the ray tracing method. S33. Based on the propagation time, the full matrix data is superimposed with a delay to obtain an initial pixel matrix; S34. Perform logarithmic normalization and dynamic range compression on the initial pixel matrix to obtain the fully focused image.

[0009] A further improvement of this invention is that the multi-scale edge detection algorithm in step S3 is an algorithm combining the Canny operator and Zernike moments, specifically including: S41. The Canny operator is used to perform preliminary edge extraction on the fully focused image; S42. Use Zernike moments to perform sub-pixel-level precise positioning of the initially extracted edges; S43. Based on the Otsu's method, edge points are screened to remove interference points belonging to the defect area, thus obtaining the discrete feature point set.

[0010] A further improvement of the present invention is that the spacing between the feature points of the discrete feature point set is controlled at 0.5 mm.

[0011] A further improvement of this invention is that the curve fitting algorithm in step S4 employs cubic polynomial fitting, specifically including: S51. Construct a two-dimensional fitting coordinate system, where the X-axis is parallel to the tangent direction of the web surface and the Z-axis is perpendicular to the web surface. S52. Based on the discrete feature point set, uniformly set the fitting nodes; S53. With the goal of minimizing the sum of squared Euclidean distances from feature points to the fitted curve, solve for the control points or coefficients of the fitted curve to complete the interface fitting.

[0012] A further improvement of the present invention is that the array probe in step S1 is a linear array probe with 128 array elements and a center frequency of 5MHz to 10MHz.

[0013] A further improvement of the present invention is that the coupling medium in step S1 is water, and the array probe is controlled by a robotic arm to scan underwater at a perpendicular and constant coupling distance with the surface of the wind turbine blade.

[0014] A wind turbine blade interlayer bonding interface fitting system based on ultrasonic phased array, wherein the wind turbine blade is a three-layer composite bonding structure consisting of an industrial plastic web, an epoxy resin structural adhesive layer, and a fiberglass blade layer, the system comprising: Detection system configuration and parameter initialization unit: Configures the detection system including ultrasonic phased array detector, array probe, robotic arm and coupling medium, and initializes the system parameters; Full-matrix data acquisition and preprocessing unit: controls the array probe to perform full-matrix data acquisition on the interlayer bonding area of ​​the wind turbine blade, and preprocesses the acquired ultrasonic echo signals; Full-focus imaging and feature extraction unit: Based on the multi-layer medium sound velocity distribution model and ray tracing method, the ultrasonic propagation delay is calculated, and the preprocessed full matrix data is superimposed point by point with delay to generate a full-focus image of the adhesive layer-blade layer bonding interface; based on the full-focus image, a multi-scale edge detection algorithm is used to extract the discrete feature point set of the bonding interface; Adhesive interface curve fitting unit: Based on the discrete feature point set, a curve fitting algorithm is used to fit the continuous curve of the adhesive interface. Imaging visualization unit: The fitted bonding interface curve is superimposed onto the full-focus image for visualization display.

[0015] A further improvement of this invention is that the preprocessing in the detection system configuration and parameter initialization unit includes: S21. Use a bandpass filter to filter the echo signal; S22. Using the reference echo signal at the web-glue interface as a reference, perform time delay correction on the signal; S23. Use wavelet threshold denoising algorithm to denoise the signal; S24. Perform coherent weighting processing on the multi-channel echo signals of the same imaging point.

[0016] Compared with the prior art, the present invention has at least the following beneficial technical effects: The method and system for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array provided by this invention can accurately extract feature points of the bonding interface in complex image backgrounds containing noise, defect echoes, etc., thereby effectively eliminating interference and providing a clean and reliable data foundation for subsequent high-precision fitting.

[0017] Furthermore, this invention specifically defines the multi-scale edge detection algorithm as an algorithm combining the Canny operator and Zernike moments. First, the Canny operator, through Gaussian filtering smoothing, non-maximum suppression, and double threshold detection, quickly and accurately delineates the preliminary outline of the bonding interface from an image filled with material noise and false edges, narrowing the problem from a full-image search to a pixel-level range of candidate fine lines, laying a low-noise foundation for subsequent processing. Finally, the maximum inter-class variance method is used to adaptively and intelligently distinguish high-amplitude points belonging to continuous interfaces from interference points belonging to isolated defects based on echo amplitude differences, effectively eliminating abnormal echoes that may distort the fitting results and ensuring the purity and accuracy of the final discrete feature point set. Through the synergistic effect of the above methods, this invention not only achieves stable identification of real bonding interfaces in complex image backgrounds filled with material noise and defect echoes, but also ensures the purity and reliability of the data, thus fundamentally solving the problems of inaccurate interface feature point extraction and susceptibility to interference in existing technologies.

[0018] In summary, this invention effectively solves the imaging distortion problem caused by sound velocity differences in heterogeneous multilayer structures, achieves high-precision fitting and quantitative evaluation of the micro-curvature bonding interface morphology, and significantly improves the reliability of wind turbine blade interlayer bonding quality detection. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the full array acquisition of the present invention; Figure 2 This is a schematic diagram of the ultrasonic travel path of the present invention; Figure 3 This is a flowchart of the interlayer bonding interface fitting method for wind turbine blades based on ultrasonic phased array according to the present invention. Figure 4 This is a typical process diagram of the present invention, wherein... Figure 4 Image (a) shows the interface morphology at the adhesive layer-blade junction. Figure 4 (b) shows a fully focused image. Figure 4 (c) shows a comparison between the interface fitting and the actual contour; Figure 5 This is a block diagram of the interlayer bonding interface fitting system for wind turbine blades based on ultrasonic phased array according to the present invention. Detailed Implementation

[0021] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0022] In the description of this invention, it should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0023] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0024] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0025] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0026] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] Example 1 The present invention provides a method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array. The wind turbine blade is a three-layer composite bonding structure consisting of an industrial plastic web, an epoxy resin structural adhesive layer, and a fiberglass blade layer. The method includes the following steps: S1. Detection system configuration and parameter initialization: Configure the detection system including the ultrasonic phased array detector, array probe, robotic arm and coupling medium, and initialize the system parameters; S2. Full-matrix data acquisition and preprocessing: Control the array probe to perform full-matrix data acquisition on the interlayer bonding area of ​​the wind turbine blade, and preprocess the acquired ultrasonic echo signals; S3. Full-focus imaging and feature extraction: The ultrasonic propagation delay is calculated based on the multi-layer medium sound velocity distribution model and ray tracing method. The preprocessed full matrix data is then overlaid point by point to generate a full-focus image of the adhesive layer-blade layer bonding interface. Based on the full-focus image, a multi-scale edge detection algorithm is used to extract the discrete feature point set of the bonding interface. S4. Adhesive interface curve fitting: Based on the discrete feature point set, a curve fitting algorithm is used to fit the continuous curve of the adhesive interface. S5. Imaging visualization: The fitted bonding interface curve is superimposed onto the full-focus image for visualization display.

[0028] In this embodiment, the preprocessing in step S2 includes: S21. Use a bandpass filter to filter the echo signal; S22. Using the reference echo signal at the web-glue interface as a reference, perform time delay correction on the signal; S23. Use wavelet threshold denoising algorithm to denoise the signal; S24. Perform coherent weighting processing on the multi-channel echo signals of the same imaging point.

[0029] In this embodiment, generating a fully focused image in step S3 specifically includes: S31. Divide the imaging area into a grid; S32. Based on the acoustic characteristics of each layer of materials in the web, rubber layer and blade layer, the propagation time of ultrasonic waves from the transmitting element to the imaging point and from the imaging point to the receiving element is calculated using the ray tracing method. S33. Based on the propagation time, the full matrix data is superimposed with a delay to obtain an initial pixel matrix; S34. Perform logarithmic normalization and dynamic range compression on the initial pixel matrix to obtain the fully focused image.

[0030] In this embodiment, the multi-scale edge detection algorithm in step S3 is an algorithm combining the Canny operator and Zernike moments, specifically including: S41. The Canny operator is used to perform preliminary edge extraction on the fully focused image; S42. Use Zernike moments to perform sub-pixel-level precise positioning of the initially extracted edges; S43. Based on the Otsu's method, edge points are screened to remove interference points belonging to the defect area, thus obtaining the discrete feature point set.

[0031] In this embodiment, the feature point spacing of the discrete feature point set is controlled at 0.5 mm.

[0032] In this embodiment, the curve fitting algorithm in step S4 uses cubic polynomial fitting, specifically including: S51. Construct a two-dimensional fitting coordinate system, where the X-axis is parallel to the tangent direction of the web surface and the Z-axis is perpendicular to the web surface. S52. Based on the discrete feature point set, uniformly set the fitting nodes; S53. With the goal of minimizing the sum of squared Euclidean distances from feature points to the fitted curve, solve for the control points or coefficients of the fitted curve to complete the interface fitting.

[0033] In this embodiment, the array probe mentioned in step S1 is a linear array probe with 128 array elements and a center frequency of 5MHz to 10MHz.

[0034] In this embodiment, the coupling medium in step S1 is water, and the array probe is controlled by a robotic arm to scan underwater at a perpendicular and constant coupling distance to the surface of the wind turbine blade.

[0035] Example 2 The core equipment of the detection system used in this invention is the NovaScan V2 portable ultrasonic phased array detector produced by Guangzhou Duopule Electronic Technology Co., Ltd., which, together with a water tank, a six-axis robotic arm, a height-adjustable support, and a main control computer, forms a complete detection system.

[0036] Combination Figure 1 , Figure 2 , Figure 3 This invention describes a method for fitting the interlayer bonding interface of wind turbine blades based on an ultrasonic phased array. The specific steps of this fitting method are as follows: Step 1: Fix the blade workpiece in the water tank using the liftable bracket, maintaining a 50mm gap between the workpiece and the bottom of the water tank; inject deionized water into the water tank as a coupling medium to ensure good coupling between the probe and the workpiece surface; Step 2: The motion control system sends a signal to control the robotic arm to move the array probe to the designated origin position of the blade workpiece, and adjusts the posture of the robotic arm to keep the array probe horizontal and perpendicular to the blade workpiece; Step 3: As Figure 1 As shown, the NovaScan V2 instrument collects full matrix data in FMC-TFM mode, and the data storage adopts dual storage of EMMC (128G) + SSD (512G), with the number of sampling points set to 16384 and PRF selected as "optimal" mode; Step 4: Move the array probe along the horizontal direction (X direction) using a robotic arm to perform interval-by-interval motion scanning; Step 5: As Figure 4 As shown, after each movement of the robotic arm, the probe collects data according to step 3 and transmits it to the computer. The computer reconstructs the ultrasound image, extracts interface feature points, fits the interface, and records the relative position (x,z). In some embodiments of the present invention, step 3 uses a 128-element linear array ultrasonic probe with a center frequency of 7.5MHz, an element spacing of 0.3mm, 128 main axis elements, an element width of 0.5mm, an element length of 10mm, and a reference point of 2.2mm; the sound wave type is longitudinal wave, and the height of the first element is 20mm.

[0037] In some embodiments of the present invention, the process of performing ultrasonic imaging of the blade workpiece array by computer in step 4 is as follows: Figure 3 As shown, the specific steps are as follows: S31: The computer filters the echo signals received by each element of the array probe to remove unnecessary noise components and performs envelope detection. S32: Divide the imaging area into a grid and determine the acoustic parameters of the workpiece; The x-axis is parallel to the surface of the workpiece and points to the right along the array direction, while the z-axis is perpendicular to the array surface and points inward into the workpiece. By setting the resolution of the x and z axes, the measured area is meshed to obtain the coordinates of each pixel. The pixel resolution is set to 0.1 mm. The web-adhesive layer interface is discretized into nodes with a certain interval, and the nodes of each layer are linearly connected to the nodes of adjacent layers according to a specified rule. Assuming that each interface layer has Q nodes, the shortest time is taken as the actual ultrasonic wave propagation time. S33: Calculate the travel time ti(x,z) from the transmitting element to the imaging point: The horizontal coordinate of the array element is xi, the vertical coordinate is zi, the distances from the j-th discrete point to the transmitting element and the imaging point are d1j and d2j, respectively, and the sound velocities of the web layer and the adhesive layer are c1 and c2, respectively. The time ti(x,z) from the i-th transmitting element to the imaging point P(x,z) is:

[0038] S34: The flight time tj(x,z) of the backscattered echo to the receiving array element is calculated as follows:

[0039] S35: Total travel time of the ultrasonic wave in the blade workpiece: The ultrasonic wave emitted from the i-th element propagates inside the blade, and the total travel time to reach the j-th element is:

[0040] S36: The blade workpiece is imaged using the TFM imaging method. An array probe with N elements is used, and the pixel matrix of the imaging area calculated by the TFM imaging method is represented as follows:

[0041] In the formula: sij(t) represents the ultrasonic echo signal transmitted by the i-th array element and received by the j-th array element.

[0042] S37: The pixel matrix after logarithmic normalization is:

[0043] Where max(I(x,z)) is the maximum amplitude of the entire imaging region; after normalization, dB(x,z)∈[ [80,0], interface reflection signals are usually concentrated in [ The interval is [20,0].

[0044] In some embodiments of the present invention, step 5 involves extracting interface feature points and fitting the interface. The specific steps are as follows: S51: Based on the theoretical location of the adhesive layer-blade layer interface (z=20mm), define the ROI range: x∈[0,50]mm, z∈[19.5,20.5]mm, and exclude noise interference from non-interface areas; S52: Using a combination of the Canny operator and Zernike moments to locate the edge of the interface: S521, Canny operator threshold, high threshold Th= 10dB, low threshold Tl= 30dB, extract initial edge contours; S522. Calculate the sub-pixel position of the edge using the 3rd order Zernike moment, as shown in the following formula (sub-pixel offset Δz):

[0045] in

[0046] S53: On the refined edge, extract the point with the maximum amplitude corresponding to each x-coordinate as a feature point. S54: Outlier removal, the specific steps are as follows: S541. Calculate the mean μ and standard deviation σ of the depth coordinates Zk of the feature point; ,

[0047] S542, Eliminate those that satisfy the condition. Interface feature points; S543. Calculate the depth difference between adjacent feature points. Value, set threshold ; like If the amplitude of a point is less than 50% of the average of its adjacent points, it is considered an outlier and removed. S55. Use cubic polynomial fitting, with the fitting function in the following form:

[0048] Therefore, the blade bonding interface function Z(X) can be obtained, and the bonding quality can be determined.

[0049] Example 3 like Figure 5 As shown, the present invention provides a wind turbine blade interlayer bonding interface fitting system based on ultrasonic phased array. The wind turbine blade is a three-layer composite bonding structure consisting of an industrial plastic web, an epoxy resin structural adhesive layer, and a fiberglass blade layer. The system includes: Detection system configuration and parameter initialization unit: Configures the detection system including ultrasonic phased array detector, array probe, robotic arm and coupling medium, and initializes the system parameters; Full-matrix data acquisition and preprocessing unit: controls the array probe to perform full-matrix data acquisition on the interlayer bonding area of ​​the wind turbine blade, and preprocesses the acquired ultrasonic echo signals; Full-focus imaging and feature extraction unit: Based on the multi-layer medium sound velocity distribution model and ray tracing method, the ultrasonic propagation delay is calculated, and the preprocessed full matrix data is superimposed point by point with delay to generate a full-focus image of the adhesive layer-blade layer bonding interface; based on the full-focus image, a multi-scale edge detection algorithm is used to extract the discrete feature point set of the bonding interface; Adhesive interface curve fitting unit: Based on the discrete feature point set, a curve fitting algorithm is used to fit the continuous curve of the adhesive interface. Imaging visualization unit: The fitted bonding interface curve is superimposed onto the full-focus image for visualization display.

[0050] The preprocessing in the detection system configuration and parameter initialization unit of this embodiment includes: S21. Use a bandpass filter to filter the echo signal; S22. Using the reference echo signal at the web-glue interface as a reference, perform time delay correction on the signal; S23. Use wavelet threshold denoising algorithm to denoise the signal; S24. Perform coherent weighting processing on the multi-channel echo signals of the same imaging point.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0052] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array, characterized in that, The wind turbine blade is a three-layer composite adhesive structure consisting of an industrial plastic web, an epoxy resin structural adhesive layer, and a fiberglass blade layer. The method includes the following steps: S1. Detection system configuration and parameter initialization: Configure the detection system including the ultrasonic phased array detector, array probe, robotic arm and coupling medium, and initialize the system parameters; S2. Full-matrix data acquisition and preprocessing: Control the array probe to perform full-matrix data acquisition on the interlayer bonding area of ​​the wind turbine blade, and preprocess the acquired ultrasonic echo signals; S3. Full-focus imaging and feature extraction: The ultrasonic propagation delay is calculated based on the multi-layer medium sound velocity distribution model and ray tracing method. The preprocessed full matrix data is then overlaid point by point to generate a full-focus image of the adhesive layer-blade layer bonding interface. Based on the full-focus image, a multi-scale edge detection algorithm is used to extract the discrete feature point set of the bonding interface. S4. Adhesive interface curve fitting: Based on the discrete feature point set, a curve fitting algorithm is used to fit the continuous curve of the adhesive interface. S5. Imaging visualization: The fitted bonding interface curve is superimposed onto the full-focus image for visualization display.

2. The method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array according to claim 1, characterized in that, The preprocessing described in step S2 includes: S21. Use a bandpass filter to filter the echo signal; S22. Using the reference echo signal at the web-glue interface as a reference, perform time delay correction on the signal; S23. Use wavelet threshold denoising algorithm to denoise the signal; S24. Perform coherent weighting processing on the multi-channel echo signals of the same imaging point.

3. The method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array according to claim 1, characterized in that, The generation of the full-focus image in step S3 specifically includes: S31. Divide the imaging area into a grid; S32. Based on the acoustic characteristics of each layer of materials in the web, rubber layer and blade layer, the propagation time of ultrasonic waves from the transmitting element to the imaging point and from the imaging point to the receiving element is calculated using the ray tracing method. S33. Based on the propagation time, the full matrix data is superimposed with a delay to obtain an initial pixel matrix; S34. Perform logarithmic normalization and dynamic range compression on the initial pixel matrix to obtain the fully focused image.

4. The method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array according to claim 1, characterized in that, The multi-scale edge detection algorithm described in step S3 is an algorithm that combines the Canny operator and Zernike moments, specifically including: S41. The Canny operator is used to perform preliminary edge extraction on the fully focused image; S42. Use Zernike moments to perform sub-pixel-level precise positioning of the initially extracted edges; S43. Based on the Otsu's method, edge points are screened to remove interference points belonging to the defect area, thus obtaining the discrete feature point set.

5. The method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array according to claim 1, characterized in that, The spacing between the feature points in the discrete feature point set is controlled at 0.5 mm.

6. The method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array according to claim 1, characterized in that, The curve fitting algorithm described in step S4 uses cubic polynomial fitting, specifically including: S51. Construct a two-dimensional fitting coordinate system, where the X-axis is parallel to the tangent direction of the web surface and the Z-axis is perpendicular to the web surface. S52. Based on the discrete feature point set, uniformly set the fitting nodes; S53. With the goal of minimizing the sum of squared Euclidean distances from feature points to the fitted curve, solve for the control points or coefficients of the fitted curve to complete the interface fitting.

7. The method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array according to claim 1, characterized in that, The array probe mentioned in step S1 is a linear array probe with 128 array elements and a center frequency of 5MHz to 10MHz.

8. The method for fitting the interlayer bonding interface of wind turbine blades based on ultrasonic phased array according to claim 1, characterized in that, In step S1, the coupling medium is water, and the array probe is controlled by a robotic arm to scan underwater at a constant and perpendicular coupling distance to the surface of the wind turbine blade.

9. A wind turbine blade interlayer bonding interface fitting system based on ultrasonic phased array, characterized in that, The wind turbine blade is a three-layer composite adhesive structure consisting of an industrial plastic web, an epoxy resin structural adhesive layer, and a fiberglass blade layer. The system includes: Detection system configuration and parameter initialization unit: Configures the detection system including ultrasonic phased array detector, array probe, robotic arm and coupling medium, and initializes the system parameters; Full-matrix data acquisition and preprocessing unit: controls the array probe to perform full-matrix data acquisition on the interlayer bonding area of ​​the wind turbine blade, and preprocesses the acquired ultrasonic echo signals; Full-focus imaging and feature extraction unit: Based on the multi-layer medium sound velocity distribution model and ray tracing method, the ultrasonic propagation delay is calculated, and the preprocessed full matrix data is superimposed point by point with delay to generate a full-focus image of the adhesive layer-blade layer bonding interface; based on the full-focus image, a multi-scale edge detection algorithm is used to extract the discrete feature point set of the bonding interface; Adhesive interface curve fitting unit: Based on the discrete feature point set, a curve fitting algorithm is used to fit the continuous curve of the adhesive interface. Imaging visualization unit: The fitted bonding interface curve is superimposed onto the full-focus image for visualization display.

10. The wind turbine blade interlayer bonding interface fitting system based on ultrasonic phased array according to claim 9, characterized in that, The preprocessing described in the detection system configuration and parameter initialization unit includes: S21. Use a bandpass filter to filter the echo signal; S22. Using the reference echo signal at the web-glue interface as a reference, perform time delay correction on the signal; S23. Use wavelet threshold denoising algorithm to denoise the signal; S24. Perform coherent weighting processing on the multi-channel echo signals of the same imaging point.

Images