Rotating electromagnetic field full wall thickness crack classification and depth quantification system, method and apparatus

Abstract

The present application relates to a kind of rotating electromagnetic field full-wall thickness crack classification and depth quantification system, method and equipment, belong to nondestructive testing technical field;Multiple frequency excitation signals are used, and the frequency component of the multiple frequency excitation signals covers the full-wall thickness range of the measured structure skin depth;X, Y direction magnetic field intensity data under different frequencies are collected;The X, Y direction magnetic field intensity data of same frequency are vector fused to obtain fusion magnetic field data, and the magnetic field signal distortion rate of different frequencies is calculated based on the fusion magnetic field data;For surface crack, the distortion rate of highest frequency and second highest frequency is calculated to obtain comprehensive distortion rate, and for non-surface crack, the distortion rate of lowest frequency and second lowest frequency is calculated to obtain comprehensive distortion rate.Multiple frequency signals are introduced into rotating electromagnetic field, and the response magnetic field signals of X and Y two directions are fused, to obtain surface and non-surface crack magnetic field response separation characteristics, the distortion rate of multiple frequencies is comprehensively analyzed, and then the classification and quantification of full-wall thickness crack are realized.

Description

Technical Field

[0001] This invention relates to a system, method, and equipment for classifying and quantifying the depth of full-wall-thickness cracks using rotating electromagnetic fields, belonging to the field of nondestructive testing technology. Background Technology

[0002] Rotating electromagnetic field testing technology, as an innovative electromagnetic non-destructive testing technology, inherits the advantages of non-contact testing and high precision in defect quantification, while overcoming the directional sensitivity limitations of conventional electromagnetic testing technologies. It can achieve high-precision detection of cracks in any direction. However, existing technologies still have many limitations:

[0003] 1. Inherent defects of traditional rotating electromagnetic field technology

[0004] Traditional rotating electromagnetic field detection technology uses single-frequency excitation, which can only detect surface cracks and cannot distinguish between surface and non-surface crack types. Single-frequency signal quantization of crack depth has a large error, making it difficult to meet the requirements for accurate crack assessment across the entire wall thickness. For ferromagnetic materials, due to their inherent ferromagnetic properties, crack detection involves complex magnetic fields composed of leakage and perturbation fields, posing challenges to crack quantification using rotating electromagnetic field detection technology.

[0005] 2. Limitations of existing technology

[0006] The existing patent application, CN115586245A, proposes a method for quantifying cracks in ferromagnetic materials based on pulsed rotating electromagnetic fields. It uses an FPGA platform to implement pulse excitation and signal processing, which can distinguish between surface and buried cracks and quantify their size. However, this method depends on a specific hardware platform and is designed for ferromagnetic materials. Its applicability to non-ferromagnetic materials is not explicitly mentioned.

[0007] The existing patent application publication number is CN117665092A, which proposes a method for reconstructing the surface contour of bifurcated cracks in metal parts. The method reconstructs the contour of bifurcated cracks by orthogonal scanning and gradient fusion. However, this method only targets the contour reconstruction of surface cracks and does not involve the quantification of crack depth and the differentiation of crack types within the entire wall thickness.

[0008] Existing technologies have significant shortcomings in the field of full-thickness crack detection: there is a lack of a universal method that can be applied to both ferromagnetic and non-ferromagnetic materials and can accurately quantify the crack type and depth across the entire wall thickness range in a single scan. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a rotating electromagnetic field system, method, and device for classifying and quantifying the depth of full-thickness cracks. It introduces multi-frequency signals into a rotating electromagnetic field, fuses the response magnetic field signals in the X and Y directions, derives the separation characteristics of the magnetic field responses of surface and non-surface cracks, and comprehensively analyzes the distortion rates of multiple frequencies, thereby achieving the classification and quantification of full-thickness cracks.

[0010] The rotating electromagnetic field full-thickness crack classification and depth quantification method of the present invention includes:

[0011] A multi-frequency excitation signal is used, wherein the skin depth of the frequency components of the multi-frequency excitation signal covers the entire wall thickness range of the structure under test;

[0012] The multi-frequency excitation signal is divided into multiple phase difference signals and loaded onto a rotating electromagnetic field probe. The probe is driven by a scanning device to perform a surface scan on the structure under test and collect magnetic field strength data in the X and Y directions at different frequencies.

[0013] Vector fusion is performed on X and Y direction magnetic field intensity data of the same frequency to obtain fused magnetic field data, and the distortion rate of magnetic field signals of different frequencies is calculated based on the fused magnetic field data;

[0014] A first-order polynomial fitting was performed with frequency as the independent variable and distortion rate as the dependent variable. The positive and negative values ​​of the fitting coefficients were used to distinguish between surface cracks and non-surface cracks.

[0015] For surface cracks, the combined distortion rate is calculated using the highest and second-highest frequency distortion rates. For non-surface cracks, the combined distortion rate is calculated using the lowest and second-lowest frequency distortion rates. The combined distortion rate is then substituted into the pre-calibrated crack depth calculation formula to obtain the crack depth.

[0016] Preferably, the calculation method for the fused magnetic field data is as follows:

[0017] For the same frequency Bx fi and By fi The matrices are fused to obtain N fused magnetic field matrices B with different frequencies. fi ;

[0018] ;

[0019] Among them, Bx fi Let X be the magnetic field strength in the X direction at the i-th frequency. fi Let be the magnetic field strength in the Y direction at the i-th frequency. Both the X and Y directions are parallel to the surface of the structure being measured and perpendicular to each other. i is an integer not greater than N and not less than 1.

[0020] Preferably, the multi-channel phase difference signal consists of three frequency components and signals with equal amplitude and a phase difference of 120°.

[0021] Preferably, the magnetic field signal distortion rate is calculated as follows:

[0022] Get B fi The largest distorted variable Bmax in the matrix is ​​the one that indicates the location of the crack. fi And the base value B0 where there is no crack. fi The distortion rate Q at different frequencies was calculated. fi ,

[0023] .

[0024] The expression for the first-order polynomial fitting is:

[0025] frequency f i As the independent variable X, the distortion rate Q fi As the dependent variable Y, perform a first-order polynomial fitting.

[0026] Y = aX + b;

[0027] Obtain the coefficient 'a' of the first-order polynomial. If 'a' is positive, it is determined to be a surface crack; if 'a' is negative, it is determined to be a non-surface crack.

[0028] Preferably, the overall distortion rate is calculated as follows:

[0029] If it is a surface crack, then take the distortion rate Q with the highest frequency. fN And the second highest distortion rate Q f（N-1） Calculate the overall distortion rate Q f ,

[0030] ;

[0031] The overall distortion rate Q f Substitute the values ​​into the pre-calibrated surface crack depth calculation formula to calculate the surface crack depth;

[0032] If the crack is not a surface crack, then the distortion rate Q with the lowest frequency is taken. f1 And the second lowest distortion rate Q f2 Calculate the overall distortion rate Q f ,

[0033] ;

[0034] The overall distortion rate Q f Substitute the values ​​into the pre-calibrated formula for calculating the depth of non-surface cracks to obtain the depth of the non-surface cracks.

[0035] Preferably, the frequencies of the multi-frequency excitation signals, from smallest to largest, are f1, f2, ..., f... NN is an integer greater than 2 and less than 10, the skin depth of the minimum frequency f1 is not less than the thickness of the structure being measured, and the maximum frequency f N The skin depth is less than 1mm, and other frequencies are integer multiples of the minimum frequency f1; N different frequencies of Bx fi and By fi The matrix magnetic field value is obtained by Fourier transforming the multi-frequency magnetic field signal acquired by the rotating electromagnetic field probe acquisition module.

[0036] Preferably, the excitation module of the rotating electromagnetic field probe includes three sets of coils, each set of coils being 120° apart, and the magnetic field acquisition module is located at the center of the three sets of coils.

[0037] The rotating electromagnetic field full-thickness crack classification and depth quantification system of the present invention, based on the rotating electromagnetic field full-thickness crack classification and depth quantification method, includes:

[0038] The rotating electromagnetic field probe includes three sets of excitation coils distributed at 120° and a magnetic field acquisition module located in the center, which is used to load multi-frequency excitation signals and acquire the magnetic field strength in the X and Y directions of the surface of the structure under test.

[0039] A scanning device is used to hold the rotating electromagnetic field probe to complete a surface scan of the structure under test.

[0040] The control module is used to generate three frequency components and multi-frequency excitation signals with equal amplitude and 120° phase difference, and to control the movement of the scanning device;

[0041] The signal processing module is used to fuse the acquired magnetic field signals, calculate the distortion rate, classify cracks, and quantize the depth.

[0042] The electronic device of the present invention includes:

[0043] Memory, used to store executable instructions;

[0044] A processor is configured to execute the executable instructions to implement the rotating electromagnetic field full-wall-thickness crack classification and depth quantification method.

[0045] Compared with existing technologies, the rotating electromagnetic field full-wall-thickness crack classification and depth quantification system, method, and apparatus of the present invention have the following advantages:

[0046] 1. By optimizing the frequency, this invention can generate induced currents with different penetration depths and layers on the structure under test, thereby achieving high-sensitivity detection of cracks in the entire wall thickness of the structure.

[0047] 2. This invention loads three multi-frequency signals onto a rotating electromagnetic field probe, which can generate rotating currents with different penetration depths on the structure under test, thus achieving high-sensitivity detection of surface and non-surface cracks of arbitrary directions at different depths.

[0048] 3. By establishing a fused magnetic field matrix, this invention can fuse magnetic field information in the X and Y directions, and obtain information about cracks at different angles.

[0049] 4. This invention uses frequency f i As the independent variable X, the distortion rate Q fi Using Y as the dependent variable, a first-order polynomial fitting is performed to obtain the first-order polynomial coefficients a, which can distinguish between surface and non-surface cracks. This can be achieved with a single scan, making it simple and fast, and can provide accurate crack types for structural safety assessment.

[0050] 5. This invention integrates the distortion rates of two frequencies by combining the distortion rates, which can reduce measurement errors and retain the distortion rate of the signal with the largest response to the greatest extent, thus solving the problem of large crack depth error in single-frequency distortion rate quantization. Attached Figure Description

[0051] Figure 1 This is a flowchart of the method for classifying and quantifying the depth of full-wall-thickness cracks in an embodiment of the present invention;

[0052] Figure 2 This is the rotating electromagnetic field probe structure in an embodiment of the present invention;

[0053] Figure 3 This refers to the 200Hz fusion magnetic field matrix in this embodiment of the invention.

[0054] Figure 4 This refers to the 600Hz fusion magnetic field matrix in this embodiment of the invention.

[0055] Figure 5 This refers to the 1kHz fusion magnetic field matrix in this embodiment of the invention.

[0056] Figure 6 This refers to the 5kHz fused magnetic field matrix in this embodiment of the invention.

[0057] Figure 7 This is the 10kHz fusion magnetic field matrix in this embodiment of the invention.

[0058] In the diagram: 1. First-layer excitation coil; 2. Second-layer excitation coil; 3. Third-layer excitation coil; 4. Magnetic field acquisition module. Detailed Implementation

[0059] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0060] Example 1:

[0061] like Figure 1 As shown, this embodiment discloses a method for classifying and quantifying the depth of full-thickness cracks using a rotating electromagnetic field, including the following steps:

[0062] S1: Select the excitation signal frequency based on the characteristics of the structure under test;

[0063] Based on the material, thickness, conductivity, and other characteristics of the structure under test, select N excitation signals of different frequencies (N is an integer greater than 2 and less than 10). The frequency selection must meet the following requirements:

[0064] The skin depth of the minimum frequency f1 is not less than the thickness of the structure being measured, ensuring that the signal can penetrate to the full wall thickness of the structure.

[0065] Maximum frequency f N The skin depth is less than 1mm, ensuring the sensitivity for detecting minute surface cracks;

[0066] The intermediate frequency is an integer multiple of the minimum frequency f1, which facilitates the synthesis and decomposition of multi-frequency signals.

[0067] For example, the thickness of the structure being tested is 6 mm, the material is aluminum alloy, its relative permeability is 1, and its electrical conductivity is 3 × 10⁻⁶. 7 S / m, according to the skin effect formula:

[0068] ;

[0069] μ Permeability, σ For electrical conductivity, ω The frequency corresponding to a 6mm skin depth is 234.8Hz. In order to ensure that the lowest frequency can fully cover the entire wall thickness, the lowest frequency is selected as 200Hz.

[0070] A skin depth of 0.5mm corresponds to a frequency of 8.44kHz, therefore the highest frequency is chosen to be 10kHz.

[0071] Other frequencies are integer multiples of the lowest frequency. N is chosen as 5, and the 5 frequencies are f1=200Hz, f2=600Hz, f3=1Hz, f4=5kHz, and f5=10kHz respectively.

[0072] S2: Forms three multi-frequency signals and loads them onto the rotating electromagnetic field probe;

[0073] The selected frequencies are combined into three multi-frequency signals. Each multi-frequency signal has equal frequency components and amplitude, and a phase difference of 120°. These three multi-frequency signals are then applied to the rotating electromagnetic field probe. Figure 2 As shown, the excitation module of the rotating electromagnetic field consists of three sets of coils: the first excitation coil 1, the second excitation coil 2, and the third excitation coil 3. The positions of each set of coils are 120° apart, and the magnetic field acquisition module 4 is located at the center of the three sets of coils.

[0074] S3: Complete the surface scan of the structure under test and acquire N Bx values ​​at different frequencies. fi and By fi matrix;

[0075] A scanning device holds a rotating electromagnetic field probe to complete a surface scan of the structure under test, acquiring five Bx values ​​at different frequencies. fi and By fi matrix.

[0076] S4: For Bx of the same frequency fi and By fi The matrices are fused to obtain N fused magnetic field matrices B with different frequencies. fi ;

[0077] For the same frequency Bx fi and By fi The matrices are merged according to the following formula.

[0078] ;

[0079] Five fused magnetic field matrices B with different frequencies were obtained. f1 B f2 B f3 B f4 B f5 ,like Figures 3-7 As shown.

[0080] S5: Calculate the distortion rate of the fused magnetic field matrix at different frequencies. Q fi ;

[0081] get B fi The largest distortion variable in the matrix where the crack is located Bmax fi and the base value without crack locations B0 fi The distortion rate at different frequencies was calculated. Q fi ,

[0082] ;

[0083] Taking 200Hz as an example, the maximum distortion in the cracked area is 2.76V, and the base value in the crack-free area is 2.18V. The calculated distortion rate is 0.26. Following the same method, the distortion rates for 600Hz, 1kHz, 5kHz, and 10kHz are 0.22, 0.16, 0.03, and 0.01, respectively.

[0084] S6: With frequency as the independent variable X and distortion rate as the dependent variable Y, perform a polynomial fitting to obtain the coefficients and determine the crack type.

[0085] Using frequencies of 200Hz, 600Hz, 1kHz, 5kHz, and 10kHz as independent variables X, and distortion rates of 0.26, 0.22, 0.16, 0.03, and 0.01 as dependent variables Y, a first-order polynomial fitting was performed.

[0086] Y = aX + b

[0087] The coefficients of the first-order polynomial are obtained as a = -2.42 × 10⁻⁶. -5 ;

[0088] A negative value for 'a' indicates that the distortion rate decreases as the frequency increases, classifying it as a non-surface crack. This is because the lower the frequency, the greater the skin depth, the larger the interaction area between the non-surface crack and the induced current, and the more significant the disturbance to the magnetic field.

[0089] S7: Calculate the overall distortion rate Q based on the crack type. f Then, the crack depth is calculated;

[0090] The distortion rate Q is calculated by taking the lowest frequency (200Hz) with a distortion rate of 0.26 and the second lowest frequency (600Hz) with a distortion rate of 0.22. f ,

[0091] ;

[0092] The overall distortion rate Q f Substituting 0.185 into the pre-calibrated formula for calculating the depth of non-surface cracks, the depth of the non-surface crack is calculated to be 0.9 mm from the surface.

[0093] Example 2:

[0094] The structure under test is scanned again. The operation steps for S1-S5 are the same as in Implementation Case 1, and will not be repeated here.

[0095] S6: With frequency as the independent variable X and distortion rate as the dependent variable Y, perform a polynomial fitting to obtain the coefficients and determine the crack type.

[0096] Using frequencies of 200Hz, 600Hz, 1kHz, 5kHz, and 10kHz as independent variables X, and distortion rates of 0.17, 0.19, 0.23, 0.28, and 0.32 as dependent variables Y, a first-order polynomial fitting was performed.

[0097] Y = aX + b

[0098] The coefficients of the first-order polynomial are obtained as a = 1.4 × 10⁻⁶. -5 ;

[0099] A positive 'a' indicates that the distortion rate increases with increasing frequency, classifying it as a surface crack. This is because the higher the frequency, the smaller the skin depth, and the more significant the disturbance of the magnetic field by the surface crack.

[0100] S7: Calculate the overall distortion rate Q based on the crack type. f Then, the crack depth is calculated;

[0101] The distortion rate of 0.32 at the highest frequency (10kHz) and 0.28 at the second highest frequency (5kHz) are used to calculate the combined distortion rate Q. f ;

[0102] ;

[0103] The overall distortion rate Q f Substituting 0.23 into the pre-calibrated formula for calculating the surface crack depth, the depth of the non-surface crack is calculated to be 1.5 mm.

[0104] The calibration formula can be established by experimentally measuring the distortion rate of surface cracks at different depths, thus establishing the relationship between the distortion rate and the crack depth.

[0105] Through the above steps, it is possible to distinguish the types of cracks and accurately quantify their depths across the entire wall thickness of the tested structure, providing reliable data support for structural safety assessment.

[0106] Example 3:

[0107] Based on Example 1, the rotating electromagnetic field full-wall-thickness crack classification and depth quantification system provided by the present invention includes:

[0108] Rotating electromagnetic field probe: It includes three sets of excitation coils distributed at 120° and a magnetic field acquisition module 4 located in the center, which is used to load multi-frequency excitation signals and acquire the magnetic field intensity in the X and Y directions of the surface of the structure under test.

[0109] Scanning device: A robotic arm or automatic scanning platform is used to hold a rotating electromagnetic field probe to complete a full-coverage scan of the structure under test.

[0110] Control module: Used to generate three frequency components and multi-frequency excitation signals with equal amplitude and 120° phase difference, and to control the movement trajectory and speed of the scanning device.

[0111] Signal processing module: Performs Fourier transform, fusion processing, distortion rate calculation, polynomial fitting, crack classification, and depth quantization calculation on the acquired magnetic field signals.

[0112] Parameter settings: Set the parameters of the structure under test (material, thickness, conductivity, etc.), excitation signal frequency, scanning step distance, etc. in the control module.

[0113] System workflow:

[0114] Signal generation: The control module generates three multi-frequency signals with a phase difference of 120°, which are then applied to the excitation coil of the rotating electromagnetic field probe.

[0115] Scanning and data acquisition: The scanning device drives the probe to perform a surface scan of the structure under test according to a preset trajectory. The magnetic field acquisition module 4 collects magnetic field intensity data in the X and Y directions in real time and transmits it to the signal processing module.

[0116] Signal processing: The signal processing module performs Fourier transform, fusion processing, distortion rate calculation, polynomial fitting, crack classification, and depth quantization calculation on the acquired magnetic field signals.

[0117] The results show that the display module displays the detection results in real time, including magnetic field intensity cloud map, crack location, type and depth quantitative data, and generates a detection report.

[0118] Example 4:

[0119] Based on Embodiment 1, the electronic device provided by the present invention includes a memory and a processor:

[0120] Memory: Used to store executable instructions and pre-calibrated data such as crack depth calculation formulas and magnetic field base values.

[0121] Processor: Used to execute executable instructions to implement the rotating electromagnetic field full-thickness crack classification and depth quantification method described in Example 1, and can output crack classification results and depth quantification data through the display module.

[0122] Electronic device workflow:

[0123] Power on / off: Turn on the power of the electronic device, start the detection software, and enter the main interface.

[0124] Parameter settings: Set the parameters of the structure under test, excitation signal frequency, scan step distance, etc. in the main interface.

[0125] Signal acquisition: Place the rotating electromagnetic field probe close to the surface of the structure being tested, click the "Start Detection" button, and the signal acquisition unit will collect the magnetic field strength data in the X and Y directions in real time.

[0126] Signal processing: The signal processing unit performs real-time processing on the acquired magnetic field signals, including Fourier transform, fusion processing, distortion rate calculation, polynomial fitting, crack classification, and depth quantization calculation.

[0127] Results show that the display unit displays the test results in real time, including magnetic field strength curves, crack type identification, depth quantification data, etc.; after the test is completed, a test report can be generated and exported.

[0128] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for classifying and quantifying the depth of full-wall-thickness cracks using a rotating electromagnetic field, characterized in that, include: A multi-frequency excitation signal is used, wherein the skin depth of the frequency components of the multi-frequency excitation signal covers the entire wall thickness range of the structure under test; The multi-frequency excitation signal is divided into multiple phase difference signals and loaded onto a rotating electromagnetic field probe. The probe is driven by a scanning device to perform a surface scan on the structure under test and collect magnetic field strength data in the X and Y directions at different frequencies. Vector fusion is performed on X and Y direction magnetic field intensity data of the same frequency to obtain fused magnetic field data, and the distortion rate of magnetic field signals of different frequencies is calculated based on the fused magnetic field data; A first-order polynomial fitting was performed with frequency as the independent variable and distortion rate as the dependent variable. The positive and negative values ​​of the fitting coefficients were used to distinguish between surface cracks and non-surface cracks. For surface cracks, the distortion rates of the highest and second-highest frequencies are used to calculate the overall distortion rate. For non-surface cracks, the distortion rates of the lowest and second-lowest frequencies are used to calculate the overall distortion rate. The overall distortion rate is then substituted into the pre-calibrated crack depth calculation formula to obtain the crack depth. The magnetic field signal distortion rate is calculated as follows: Obtain the fused magnetic field matrix B fi The largest distortion Bmax at the location of the crack fi And the base value B0 where there is no crack. fi The distortion rate Q at different frequencies was calculated. fi , ； The expression for the first-order polynomial fitting is: Let frequency fi be the independent variable X, and distortion rate Q be... fi As the dependent variable Y, perform a first-order polynomial fitting. Y = aX + b; Obtain the coefficient 'a' of the first-order polynomial. If 'a' is positive, it is determined to be a surface crack; if 'a' is negative, it is determined to be a non-surface crack. The calculation method for the overall distortion rate is as follows: If it is a surface crack, then take the distortion rate Q with the highest frequency. fN And the second highest distortion rate Q f（N-1） Calculate the overall distortion rate Q f , ； The overall distortion rate Q f Substitute the values ​​into the pre-calibrated surface crack depth calculation formula to calculate the surface crack depth; If the crack is not a surface crack, then the distortion rate Q with the lowest frequency is taken. f1 And the second lowest distortion rate Q f2 Calculate the overall distortion rate Q f , ； The overall distortion rate Q f Substitute the values ​​into the pre-calibrated formula for calculating the depth of non-surface cracks to obtain the depth of the non-surface cracks.

2. The method for classifying and quantifying the depth of full-wall-thickness cracks using a rotating electromagnetic field according to claim 1, characterized in that, The calculation method for the fused magnetic field data is as follows: For the same frequency Bx fi and By fi The matrices are fused to obtain N fused magnetic field matrices B with different frequencies. fi ; ； Among them, Bx fi Let X be the magnetic field strength in the X direction at the i-th frequency. fi Let be the magnetic field strength in the Y direction at the i-th frequency. Both the X and Y directions are parallel to the surface of the structure being measured and perpendicular to each other. i is an integer not greater than N and not less than 1.

3. The method for classifying and quantifying the depth of full-wall-thickness cracks using a rotating electromagnetic field according to claim 1, characterized in that, The multi-channel phase difference signal consists of three frequency components and signals with equal amplitude and a phase difference of 120°.

4. The method for classifying and quantifying the depth of full-wall-thickness cracks using a rotating electromagnetic field according to claim 2, characterized in that, The frequencies of the multi-frequency excitation signals, from smallest to largest, are f1, f2, ..., f... N N is an integer greater than 2 and less than 10, the skin depth of the minimum frequency f1 is not less than the thickness of the structure being measured, and the maximum frequency f N The skin depth is less than 1mm, and other frequencies are integer multiples of the minimum frequency f1; N different frequencies of Bx fi and By fi The matrix magnetic field value is obtained by Fourier transforming the multi-frequency magnetic field signal acquired by the rotating electromagnetic field probe acquisition module.

5. The method for classifying and quantifying the depth of full-wall-thickness cracks using a rotating electromagnetic field according to claim 1, characterized in that, The excitation module of the rotating electromagnetic field probe contains three sets of coils, each set of coils being 120° apart, and the magnetic field acquisition module (4) is located at the center of the three sets of coils.

6. A rotating electromagnetic field full-thickness crack classification and depth quantification system, based on the rotating electromagnetic field full-thickness crack classification and depth quantification method according to any one of claims 1-5, characterized in that, include: The rotating electromagnetic field probe includes three sets of excitation coils distributed at 120° and a magnetic field acquisition module (4) located in the center, which is used to load multi-frequency excitation signals and acquire the magnetic field strength in the X and Y directions of the surface of the structure under test. A scanning device is used to hold the rotating electromagnetic field probe to complete a surface scan of the structure under test. The control module is used to generate three frequency components and multi-frequency excitation signals with equal amplitude and 120° phase difference, and to control the movement of the scanning device; The signal processing module is used to fuse the acquired magnetic field signals, calculate the distortion rate, classify cracks, and quantize the depth.

7. An electronic device, characterized in that, include: Memory, used to store executable instructions; A processor for executing the executable instructions to implement the rotating electromagnetic field full-wall-thickness crack classification and depth quantification method according to any one of claims 1-5.

Images