Array coil excitation coupling eddy current detection probe, system, method and related device

Abstract

The invention discloses an array coil excitation coupling eddy current detection probe, system and method and a related device, and relates to the technical field of nondestructive testing. The probe comprises a double-coil excitation module and a sensing module; the double-coil excitation module comprises two semicircular Helmholtz coils; the two semicircular Helmholtz coils are symmetrically arranged, are parallel and coaxial, and are electrified with alternating-current excitation current with the same direction, the same frequency and the same phase; the distance between the two semicircular Helmholtz coils is adjustable; and the sensing module is arranged in the central area of the two semicircular Helmholtz coils and is used for detecting the magnetic field change caused by the eddy current field at the defect. According to the invention, the detection precision of pipeline corrosion, cracks and composite defects can be improved.

Description

Technical Field

[0001] This application relates to the field of nondestructive testing technology, and in particular to an array coil excitation coupled eddy current testing probe, system, method and related apparatus. Background Technology

[0002] Eddy current testing technology has important applications in pipeline inspection due to its advantages such as non-contact operation, high efficiency, and no need for coupling agents. However, traditional eddy current probes suffer from weak signals, low signal-to-noise ratios, and significant susceptibility to lift-off effects when detecting complex composite defects (such as corrosion and cracks), making it difficult to meet the requirements of high sensitivity and high reliability for pipeline inspection. In existing technologies, the eddy current field intensity generated by a single-coil excitation structure is limited and easily affected by environmental noise; the eddy current fields in the central detection area of ​​the reverse-excitation dual-coil structure cancel each other out, resulting in insufficient detection capability.

[0003] Therefore, improving the detection accuracy of pipeline corrosion, cracks, and complex defects has become a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0004] The purpose of this application is to provide an array coil excitation coupled eddy current detection probe, system, method and related devices, which can improve the detection accuracy of pipeline corrosion, cracks and complex defects.

[0005] To achieve the above objectives, this application provides the following solution.

[0006] In a first aspect, this application provides an array coil excitation coupled eddy current detection probe, which includes: a dual-coil excitation module and a sensing module.

[0007] The dual-coil excitation module includes two semi-circular Helmholtz coils; the two semi-circular Helmholtz coils are symmetrically arranged, parallel and coaxial, and are supplied with AC excitation currents of the same direction, frequency and phase; the spacing between the two semi-circular Helmholtz coils is adjustable.

[0008] The sensing module is located in the central region of the two semi-circular Helmholtz coils and is used to detect the magnetic field changes caused by the eddy current field at the defect.

[0009] Secondly, this application provides an array coil excitation coupling eddy current detection system, which includes: a probe, a pipe detector, an excitation signal source, a signal conditioning circuit, and a data acquisition and processing module; the probe is the array coil excitation coupling eddy current detection probe described in the first aspect.

[0010] The probe is mounted on the detector inside the pipeline.

[0011] The in-pipe detector is located inside the pipe and moves along the pipe's axial direction.

[0012] The excitation signal source is connected to the two semi-circular Helmholtz coils of the probe respectively. A function generator generates a sinusoidal excitation signal, which is then amplified by a power amplifier and impedance matching circuit to drive the two semi-circular Helmholtz coils simultaneously.

[0013] The signal conditioning circuit is connected to the sensing module of the probe and is used to extract the magnetic field signal of the sensing module.

[0014] The data acquisition and processing module, connected to the signal conditioning circuit, is used to acquire the magnetic field signal in real time using a high-speed acquisition card, and extract defect features through processing algorithms in the host computer software; identify the defect type and evaluate the size based on the defect features; the processing algorithm includes: Hilbert transform to extract the signal envelope, local weighted regression smoothing, and wavelet threshold denoising; the defect features include: signal amplitude and waveform characteristics; the defect types include: cracks, corrosion, and composite defects.

[0015] Thirdly, this application provides a method for detecting eddy currents coupled to the excitation of an array coil. The method is implemented based on the array coil excitation coupling eddy current detection system described in the second aspect, and includes the following steps.

[0016] Acquire magnetic field signals; the magnetic field signals are obtained by installing the probe on the detector inside the pipe, moving it along the pipe axis inside the pipe, and passing an AC excitation current with the same direction, frequency and phase to two semi-circular Helmholtz coils, after inducing an enhanced eddy current field inside the pipe wall, and then detecting the signal caused by the distortion of the eddy current field in real time through the sensing module.

[0017] After conditioning and acquiring the magnetic field signal, defect features are extracted through processing algorithms. The processing algorithms include: Hilbert transform to extract the signal envelope, local weighted regression smoothing, and wavelet thresholding for denoising. The defect features include: the amplitude and waveform characteristics of the signal.

[0018] The defect type is identified and the size is evaluated based on the defect characteristics; the defect types include: cracks, corrosion and composite defects.

[0019] Fourthly, this application provides a computer device, including: a memory, a processor, and a computer program stored in the memory and capable of running on the processor, wherein the processor executes the computer program to implement the array coil excitation coupling eddy current detection method described in the third aspect.

[0020] Fifthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the array coil excitation coupling eddy current detection method described in the third aspect.

[0021] Based on the specific embodiments provided in this application, the following technical effects are disclosed.

[0022] This application provides an array coil excitation coupling eddy current detection probe, system, method, and related devices. The probe includes a dual-coil excitation module and a sensing module. The dual-coil excitation module includes two semi-circular Helmholtz coils. The design of the two semi-circular Helmholtz coils utilizes the magnetic field characteristics of the Helmholtz coils to form a relatively uniform basic excitation magnetic field in the surrounding space, providing a stable and controllable magnetic field environment for subsequent eddy current detection. The two semi-circular Helmholtz coils are symmetrically arranged, parallel, and coaxial, and are supplied with AC excitation currents of the same direction, frequency, and phase. This further improves the symmetry and uniformity of the magnetic field distribution, avoids magnetic field distortion caused by coil arrangement deviations, and ensures the consistency of the magnetic field in the detection area. The simultaneous application of AC excitation currents of the same direction, frequency, and phase to the two semi-circular Helmholtz coils allows the magnetic fields generated by the two coils to superimpose and enhance each other in space, improving the strength and stability of the excitation magnetic field while avoiding magnetic field interference caused by inconsistent current parameters, thus ensuring the purity of the excitation magnetic field. The spacing between the two semi-circular Helmholtz coils is adjustable; the coil spacing can be flexibly adjusted according to the actual needs such as the size of the workpiece to be inspected and the inspection depth, adapting to different inspection scenarios and expanding the applicability of the probe. The sensing module is set in the central area of ​​the two semi-circular Helmholtz coils and is used to detect the magnetic field changes caused by the eddy current field at the defect; it can accurately capture the magnetic field signal caused by the eddy current field changes at the defect. The magnetic field uniformity in this area is good and the signal strength is moderate, which can effectively improve the sensitivity and detection accuracy of the sensing module to the changes in the defect magnetic field and reduce the detection error caused by background magnetic field interference. This application achieves uniform, stable and adjustable excitation magnetic field by optimizing the structure and parameter settings of the dual-coil excitation module and combining it with the precise layout of the sensing module, thereby improving the detection sensitivity and accuracy of the changes in the defect magnetic field. At the same time, it has good scene adaptability, which can meet the eddy current inspection needs of different types of workpieces and ensure the accuracy and reliability of the inspection results. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the assembly of an array coil excitation coupling eddy current detection probe provided in one embodiment of this application.

[0025] Figure 2 This is a schematic diagram of the probe array arrangement in the circumferential direction provided in an embodiment of this application.

[0026] Figure 3 This is a flowchart illustrating an array coil excitation coupling eddy current detection method provided in one embodiment of this application.

[0027] Figure 4 This is a schematic diagram of the coil arrangement structure and parameter settings provided in an embodiment of this application.

[0028] Figure 5 This is a schematic diagram of a simulation model of a ferromagnetic specimen under different coil excitation modes provided in an embodiment of this application; wherein, Figure 5 (a) in the model is a simulation model of a single-coil excitation mode; Figure 5 (b) represents two cases of dual-coil excitation modes: co-current excitation and reverse current excitation.

[0029] Figure 6 This is a schematic diagram of the eddy current field distribution on the surface of a specimen under different excitation modes, as provided in an embodiment of this application; wherein, Figure 6 (a) in the figure is the vector distribution diagram of the eddy current field in the single-coil excitation model; Figure 6 (b) in the diagram is the vector distribution of the eddy current field in the reverse-excitation double coil; Figure 6 (c) in the diagram is the vector distribution of the eddy current field of the dual coil in the co-excitation model.

[0030] Figure 7 This is a schematic diagram of the vector distribution of the eddy current field under dual-coil excitation coupling conditions provided in an embodiment of this application; wherein, Figure 7 (a) in the figure is a vector diagram of a reverse-excited double-coil eddy current with a spacing of 5 mm; Figure 7 (b) in the figure is a vector diagram of a double-coil eddy current with a spacing of 5 mm.

[0031] Figure 8 This is a schematic diagram of the eddy current intensity on the surface of a specimen under different excitation models provided in an embodiment of this application.

[0032] Figure 9 This application provides an embodiment of a probe, including an internal component assembly diagram and a physical image of the probe after epoxy resin encapsulation; wherein... Figure 9 (a) in the diagram is a schematic diagram of the three-dimensional probe assembly structure; Figure 9 (b) in the diagram is a schematic diagram of the probe assembly; Figure 9 (c) in the image is a picture of the actual probe.

[0033] Figure 10 This is a schematic diagram of the test equipment and signal acquisition system provided in one embodiment of this application.

[0034] Figure 11 This is a schematic diagram of a defect photograph provided in an embodiment of this application; wherein, Figure 11 (a) in the diagram is a schematic diagram of a single crack defect; Figure 11 (b) in the diagram is a schematic diagram of a single corrosion defect; Figure 11 (c) in the diagram is a schematic diagram of a composite defect; Figure 11 (d) in the figure is a schematic diagram of cracked specimens at different depths; Figure 11 (e) in the figure is a schematic diagram of corrosion samples at different depths.

[0035] Figure 12 A flowchart of an experimental system and signal processing system provided in an embodiment of this application.

[0036] Figure 13 This is a schematic diagram showing the defect signal extraction results before and after signal preprocessing, according to an embodiment of this application; wherein, Figure 13 (a) in the diagram is a schematic of the signal before processing; Figure 13 (b) in the diagram is a schematic of the processed signal.

[0037] Figure 14 This is a schematic diagram of crack defect scanning experimental results based on different excitation models, provided as an embodiment of this application; wherein, Figure 14 (a) in the diagram is a schematic diagram of the crack detection results of a single coil excitation. Figure 14 (b) in the diagram is a schematic diagram of the crack detection results of the reverse-excitation dual-coil circuit; Figure 14 (c) in the diagram is a schematic diagram of the crack detection results of the dual-coil system with co-directional excitation.

[0038] Figure 15 This is a schematic diagram of corrosion defect scanning experimental results under different excitation models provided in an embodiment of this application; wherein, Figure 15 (a) in the diagram is a schematic diagram of the corrosion detection results of a single coil excitation. Figure 15 (b) in the diagram is a schematic diagram of the corrosion detection results of the reverse-excitation dual-coil circuit; Figure 15 (c) in the diagram is a schematic diagram of the corrosion detection results of the dual-coil system with co-directional excitation.

[0039] Figure 16 This is a schematic diagram illustrating the test results of crack detection performance under different lift-off conditions according to an embodiment of this application; wherein, Figure 16 (a) in the figure is a schematic diagram of the scanning test results of specimens with crack depth under different lift-off conditions; Figure 16 (b) in the figure is a schematic diagram of the signal-to-noise ratio change of the crack depth test specimen under different lift-off conditions.

[0040] Figure 17 This is a schematic diagram illustrating corrosion detection performance test results under different lift-off conditions according to an embodiment of this application; wherein, Figure 17 (a) in the figure is a schematic diagram of the scanning experimental results of specimens with different corrosion depths under different lift-off conditions; Figure 17 (b) in the figure is a schematic diagram of the signal-to-noise ratio change of the corrosion depth test specimen under different lift-off conditions.

[0041] Figure 18 This is a schematic diagram of the comparative scanning test results of a corrosion crack sample provided in an embodiment of this application.

[0042] Figure 19 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] This application designs a pipe inner surface defect detection probe and signal processing system that uses dual-excitation coils to couple and enhance eddy currents, and an array magnetic sensor to acquire signals. The dual-excitation coils excite a coupled and enhanced eddy current field with the same phase on the pipe inner surface. When defects exist on the pipe inner surface, the distortion of the coupled eddy current field can be increased. The array magnetic sensor occupies less space and can acquire the distortion of the true magnetic field value in space. Compared to coil signal acquisition, the array magnetic sensor is easier to integrate, smaller in size, and allows for a smaller sampling interval along the pipe circumference, reducing the detection blind zone in the circumferential direction. Furthermore, the spatial magnetic field signal acquired by the array magnetic sensor uses a filtering and amplification circuit and a phase-sensitive detector to obtain the amplitude and phase changes of the magnetic field signal, which can improve the detection accuracy of pipe corrosion, cracks, and complex defects.

[0046] In one exemplary embodiment, such as Figure 1 As shown, an array coil excitation coupled eddy current detection probe is provided, which includes: a dual-coil excitation module and a sensing module.

[0047] The dual-coil excitation module includes two semi-circular Helmholtz coils; the two semi-circular Helmholtz coils are symmetrically arranged, parallel and coaxial, and are energized with AC excitation currents of the same direction, frequency and phase; the spacing between the two semi-circular Helmholtz coils is adjustable (preferably 1-10mm).

[0048] The sensing module is located in the central region of the two semi-circular Helmholtz coils and is used to detect the magnetic field changes caused by the eddy current field at the defect.

[0049] As an optional implementation, each semicircular Helmholtz coil is made of copper wire with 100-200 turns, an excitation frequency of 5kHz-30kHz, and a current amplitude of 1A.

[0050] As an optional implementation, the sensing module is a TMR linear magnetic sensor, which is used to detect the magnetic field change caused by the eddy current field at the defect. The sensitive direction of the TMR sensor is perpendicular to the direction of the eddy current field, and preferably arranged along the axial direction (Z direction) of the pipe.

[0051] As an optional implementation, the dual-coil excitation module and the sensing module are fixed inside a 3D-printed resin shell and encapsulated with epoxy resin to form an integrated probe.

[0052] As an optional implementation, the array coil excitation coupled eddy current detection probe has a wear-resistant plate at its bottom to adapt to sliding detection of the inner wall of the pipe. A schematic diagram of the probe array arrangement in the circumferential direction is shown below. Figure 2 As shown.

[0053] In one exemplary embodiment, an array coil excitation coupling eddy current detection system is provided, the array coil excitation coupling eddy current detection system comprising: a probe, a pipe in-situ detector, an excitation signal source, a signal conditioning circuit, and a data acquisition and processing module; the probe is the array coil excitation coupling eddy current detection probe described above.

[0054] The probe is mounted on the detector inside the pipeline.

[0055] The in-pipe detector is located inside the pipe and moves along the pipe's axial direction.

[0056] The excitation signal source is connected to the two semi-circular Helmholtz coils of the probe respectively. A function generator generates a sinusoidal excitation signal, which is then amplified by a power amplifier and impedance matching circuit to drive the two semi-circular Helmholtz coils simultaneously.

[0057] The signal conditioning circuit is connected to the sensing module of the probe and is used to extract the magnetic field signal of the sensing module.

[0058] The data acquisition and processing module, connected to the signal conditioning circuit, is used to acquire the magnetic field signal in real time using a high-speed acquisition card, and extract defect features using processing algorithms in host computer software (such as LabVIEW); identify the defect type and evaluate the size based on the defect features; the processing algorithm includes: Hilbert transform to extract the signal envelope, local weighted regression smoothing, and wavelet thresholding for noise reduction; the defect features include: signal amplitude and waveform characteristics; the defect types include: cracks, corrosion, and composite defects.

[0059] As an optional implementation, the signal conditioning circuit includes: a differential amplifier circuit, a bandpass filter circuit (e.g., 5-30kHz), and a programmable gain amplifier circuit. The signal conditioning circuit is used to extract weak defect signals output by the TMR sensor.

[0060] In one exemplary embodiment, such as Figure 3 As shown, an array coil excitation coupling eddy current detection method is provided. The array coil excitation coupling eddy current detection method is implemented based on the array coil excitation coupling eddy current detection system described above. The array coil excitation coupling eddy current detection method includes the following steps.

[0061] S1: Acquire magnetic field signal; The magnetic field signal is obtained by installing the probe on the detector inside the pipe, moving it along the pipe axis inside the pipe, and passing AC excitation current with the same direction, frequency and phase to two semi-circular Helmholtz coils to induce an enhanced eddy current field inside the pipe wall, and then detecting the signal caused by the distortion of the eddy current field in real time through the sensing module.

[0062] S2: After conditioning and acquiring the magnetic field signal, the defect features are extracted through a processing algorithm; the processing algorithm includes: Hilbert transform to extract the signal envelope, local weighted regression smoothing, and wavelet threshold denoising; the defect features include: the amplitude and waveform characteristics of the signal.

[0063] S3: Identify the defect type and evaluate the size based on the defect characteristics; the defect types include: cracks, corrosion and composite defects.

[0064] This application utilizes dual-excitation coils to generate a coupled and enhanced eddy current field with the same phase on the inner surface of a pipe. When defects exist on the inner surface of the pipe, the distortion of the coupled eddy current field can be increased. The array magnetic sensor occupies less space and can acquire the distortion of the true magnetic field value in space. Compared to coil-based signal acquisition, the array magnetic sensor is easier to integrate, smaller in size, and allows for a smaller sampling interval along the pipe circumference, reducing the detection blind zone in that direction. Furthermore, the spatial magnetic field signal acquired by the array magnetic sensor uses a filtering and amplification circuit and a phase-sensitive detector to obtain the amplitude and phase changes of the magnetic field signal, which can improve the detection accuracy of pipe corrosion, cracks, and complex defects.

[0065] Specifically, this application proposes a novel probe design that integrates a Helmholtz coil and a TMR magnetic sensor. It adopts a dual-coil enhanced excitation method and achieves high-precision detection of complex composite defects in the inner wall of ferromagnetic pipes by detecting the magnetic field strength generated by eddy currents on the surface of ferromagnetic materials.

[0066] The dual-coil electromagnetic coupling enhancement method proposed in this application can be based on a mathematical model established using Helmholtz coils. A traditional Helmholtz coil consists of two identical circular or square coils connected in series, with parallel and coaxial coil planes, and carrying currents in the same direction and at equal speeds. This application investigates the eddy current coupling characteristics in the central region of the coil when alternating current is applied. To reduce the influence of the excitation coil on the lift-off effect in eddy current detection, the excitation coil is designed as a semi-circle, with its plane parallel to the detection surface. Alternating current of a specific frequency generates a time-varying axial magnetic field through the coil, inducing an alternating electric field in the metal pipe, thereby generating eddy currents.

[0067] According to the Biot-Savart law, the magnetic flux density on the surface of a defect-free region of a ferromagnetic specimen can be calculated. (Current element) Idl At any point in space Q The generated magnetic field is shown in equation (1).

[0068] (1).

[0069] in, μ 0 = 4π × 10 −7 T·m / A is the free permeability. r Current element Idl arrive Q Distance between points For the current element The unit vector pointing to point Q.

[0070] The distance from the center point on the axis of each turn of a single complete circular coil O for a of P The magnetic flux density generated by the point is shown in equation (2).

[0071] (2).

[0072] in, I The coil current; R The radius of the semicircular coil is given.

[0073] For the single-turn semi-circular coil designed in this application, its magnetic flux density can be approximated as half that of a circular coil, and its magnetic field strength is half that of a complete coil.

[0074] (3).

[0075] When two semicircular coils are placed symmetrically, the magnetic field in the central region is the resultant magnetic field generated by the magnetic fields of the two coils. To simplify the calculation method, according to equation (3), any point on the axis of the two coils... P The composite magnetic flux density is shown in equation (4).

[0076] (4).

[0077] in, a Test points on the axis P To the center origin O The distance; N d is the number of coil turns; d / 2 is the distance from each coil to the common center point of the two coils. The coil arrangement and parameter settings are as follows: Figure 4 As shown, this equation gives the calculation expression for the magnetic flux density in the central coupling region under dual-coil excitation. In actual testing, alternating excitation induces eddy currents in ferromagnetic materials, and defects cause eddy current distortion, generating defect magnetic field signals. Therefore, to study the field coupling characteristics of the dual-coil detection system, it is necessary to investigate the distribution and variation law of the induced eddy current field on the surface of the ferromagnetic specimen.

[0078] During the testing process, the calculation of the induced eddy currents in the metal specimen below the excitation coil can consider a radius of [missing information - likely a value]. r The circular annular region. According to Faraday's law of electromagnetic induction, the induced electric field is as shown in equation (5).

[0079] (5).

[0080] in, r The radius of the annular region is calculated based on the assumption. The axial magnetic flux density passing through the annular region is denoted as .

[0081] Calculating the eddy current field from the induced electric field requires combining Ohm's law. ), thus obtaining the eddy current density vector.

[0082] (6).

[0083] (7).

[0084] Eddy currents generate a skin effect on the surface of metal specimens, which is a key factor in determining the penetration depth of eddy current testing and therefore must be considered. When the required penetration depth exceeds the skin depth, the attenuation of the magnetic field with depth can be expressed as equation (8).

[0085] (8).

[0086] Among them, skin depth , The angular frequency of alternating current. The permeability of a ferromagnetic material Let be the electrical conductivity of the material being tested. Substituting it into equation (7), the induced eddy current density is obtained as shown in equations (9) and (10).

[0087] (9).

[0088] (10).

[0089] In summary, a complete mathematical model for the dual-coil electromagnetic coupling enhancement method was established. Based on electromagnetic theory, the magnetic flux density distribution in the central sensing region and the eddy current density distribution on the specimen surface were derived. These analytical results provide a foundation for subsequent finite element simulations, enabling more intuitive visualization and quantitative analysis of the vector field.

[0090] This application uses Ansys Maxwell software for three-dimensional finite element analysis and simulation modeling to simulate the magnetic field distribution of a ferromagnetic specimen under a dual-coil excitation model.

[0091] Figure 5 Simulation models of ferromagnetic specimens under different coil excitation modes are shown: Figure 5 (a) in the model is a simulation model of a single-coil excitation mode; Figure 5 (b) represents two cases of dual-coil excitation modes: unidirectional current excitation and reverse current excitation. The structural geometric parameters of the finite element analysis model and the electromagnetic parameters of the excitation coil material are shown in Table 1. The coil dimensions and electromagnetic parameters of the three excitation models are kept consistent. The finite element simulation specimen is a defect-free steel plate, used only for intuitive analysis of the eddy current field morphology and intensity generated on the specimen surface under different excitation models. The simulation model precisely sets the air domain size to achieve a balance between shortening computation time and ensuring computational accuracy. The research material is 45# steel, which has nonlinear relative permeability characteristics. The relevant magnetization parameters of this material are configured separately in the simulation software by importing an external BH curve. The excitation current provides the same excitation conditions, with a frequency set to 5kHz and a sinusoidal current amplitude of 0.25A. The simulation calculation time is set to 400μs, corresponding to two cycles of the alternating current.

[0092] Table 1 Geometric and electromagnetic parameters of the finite element analysis model

[0093] Figure 6 This demonstrates the eddy current vector distribution induced on the specimen surface by a copper hollow coil under different excitation modes. To facilitate intuitive observation and comparison of the differences between the various scenarios, all... Figure 6 All scales in the text are standardized to a uniform scale. Figure 6As shown in (a), under single-coil excitation, the fundamental eddy current field in the undisturbed state consists of symmetrical eddy currents closely distributed on both sides of the coil, with an average eddy current density of J A 2×10 4 A / m 2 . Figure 6 (b) and Figure 6 Figure (c) shows the eddy current field distribution of the dual coils in parallel (co-directional) and anti-parallel (reverse) modes, with a coil spacing of 80 mm (weak coupling state). The above phenomenon indicates that under weak coupling conditions, when the dual coils are excited in opposite directions, the eddy current fields in the central detection region cancel each other out, resulting in a lower average eddy current density. J A Approaching zero eddy currents makes it difficult to generate eddy currents with sufficient detection capability; however, it is reasonable to infer that when the centers of the eddy current fields within the two coils overlap, a stronger coupling state may be induced. Conversely, when excited in the same direction, the eddy current field in the central detection region exhibits a completely opposite phenomenon. The eddy current fields within the two coils generate direct and beneficial coupling, manifesting as a uniformly distributed eddy current field in the y-direction with an average eddy current density of... J A Reaching 1.8×10 4 A / m 2 The intensity is close to that of a single-coil excitation. This phenomenon originates from the mutual cancellation of the internal vortex fields in the x-direction, while the vortex fields in the y-direction are superimposed.

[0094] Gradually decrease the distance between the two coils until the centers of the eddy current fields of the inner coils coincide (e.g.) Figure 7 As shown in the figure, the eddy current field distribution on the surface of the specimen is displayed when the coil spacing is 5 mm (fully coupled state) under two excitation modes. Figure 7 (a) in the figure successfully verified the hypothesis of reverse excitation coupling: when fully coupled, the superposition of the eddy current fields in the central region of the two coils forms a single magnetic field with significantly enhanced intensity. Figure 7 (b) depicts the vector distribution of the eddy current field under fully coupled, co-directional excitation, showing a significant increase in eddy current density. It is noteworthy that, compared to... Figure 6 Compared to the weakly coupled state in (c), the direction of the uniform field is reversed when fully coupled. This is because the vector superposition is transferred from the outer region to the inner region of the vortex field, resulting in a stable and uniform vortex field. Figure 8 The eddy current field intensity extracted along the coil central axis, within a linear region 30 mm directly below the specimen surface, is shown. The peak eddy current values ​​for both dual-coil excitation methods appear at 13 mm and 18 mm along the axis, precisely below the coils. The peak eddy current density reaches its highest value of 1.6 × 10⁻⁶ for the reverse dual-coil configuration. 6 A / m 2However, to minimize the lift-off distance of the magnetic sensor, the sensor must be installed in the gap between the two sides of the coil. The average eddy current density JA in the central region of the unidirectional dual-coil device reaches 6 × 10⁻⁶. 5 A / m 2 , and the eddy current field density induced by a single coil (1.5×10 5 A / m 2 Compared to the previous method, the induced eddy current density in the co-directional dual-coil detection region was increased by three times. Therefore, the TMR magnetic sensor was mounted at the lowest point in the center of the co-directional dual-coil probe to measure the induced magnetic field along the Z-axis.

[0095] Figure 9 The diagram shows the internal component assembly of the designed probe and a physical image of the probe after epoxy resin encapsulation. The probe mainly consists of two hollow copper coils, a PCB circuit board with a TMR magnetic sensor soldered on, and a 3D-printed resin shell. The excitation coil uses 0.15mm diameter copper wire with 160 turns. The coil arrangement follows the simulation model, with the chip located at the center of the two coils. The advantage of this configuration is that the magnetic sensor mounting method minimizes the lift-off height generated by the excitation coil.

[0096] The magnetic sensor used in this embodiment is the TMR2901 manufactured by Multidimensional Technology. This is a high-sensitivity TMR linear magnetic sensing chip with a unique push-pull Wheatstone bridge structure, consisting of four unshielded TMR sensor elements. This sensor is sensitive to magnetic fields in the Y-axis direction, outputs a differential signal, has a sensitivity of up to 25mV / V / Gs, a nonlinearity of 2%FS, and low background noise.

[0097] like Figure 10As shown, a probe-based experimental testing system was constructed, comprising a three-axis motion platform, a signal generator, a DC regulated power supply, a computer, a data acquisition module, a signal acquisition and conditioning circuit, a dual-coil probe, and various ferromagnetic planar test specimens. The three-axis motion platform ensures that the probe performs defect scanning experiments on the specimen surface at a uniform and stable speed. The signal generator produces a sinusoidal signal with a frequency range of 1-250MHz. Impedance matching is achieved through a specially designed power divider circuit board, ensuring that the simulated sinusoidal signal generated by the signal generator is evenly distributed to the dual excitation coils within the probe. To acquire the output signal of the TMR2901 chip, a two-stage RC differential filter amplifier circuit consisting of a high-pass filter and a low-pass filter is used. This device can filter out various noises in the defect signal while amplifying the weak magnetic field signal of the TMR2901, thereby improving the identification accuracy of the defect signal. This module processes signals with a frequency range of 5kHz-30kHz, with an amplification gain of approximately 70 times. A 5V DC regulated power supply powers the magnetic sensor circuit board and the signal conditioning circuit. Finally, the test results were monitored and stored in real time on a computer using the NI USB-6211 data acquisition card and LabVIEW data acquisition program.

[0098] Figure 11 All the ferromagnetic specimens used in the experiment were displayed, including specimens with various single typical defects, composite defects, and defects of different sizes. Figure 11 (a) and Figure 11 The basic defect specimen shown in (b) is used to verify the conclusions of the finite element simulation analysis in the previous section; Figure 11 (c) Figure 11 (d) and Figure 11 The defect specimen shown in (e) is used to test the performance of the designed probe under normal and complex defect conditions. Table 2 details the defect dimensions of each specimen: Specimen (c) is a composite defect specimen with cracks in the corrosion pit; Specimen (d) is a crack specimen with different depths, all with a width of 0.5 mm and a depth increasing from 2 mm to 5 mm; Specimen (e) is a corrosion pit specimen with different depths, all with dimensions of 15 mm × 15 mm and a depth increasing from 0.8 mm to 3.2 mm.

[0099] Table 2 Dimensions of specimens with different defects

[0100] Since the raw signal transmitted from the acquisition card to the computer is a continuous high-frequency sinusoidal signal, it is necessary to separate the defect signal curve from the raw signal. Therefore, an envelope extraction, smoothing, and noise reduction process was designed to extract the defect signal. Figure 12The flowchart shown illustrates the overall workflow of the experimental system and the data processing system. The signal processing algorithms used include Hilbert envelope extraction, Loess local weighted regression smoothing algorithm, and wavelet transform denoising algorithm.

[0101] (1) The Hilbert envelope algorithm uses the Hilbert transform to extract the envelope of a defect signal in order to obtain the instantaneous amplitude characteristics of the defect signal. The Hilbert transform is a commonly used signal analysis method that extracts the envelope of a real signal. x ( t Convert to analytic signal z ( t An analytic signal is defined as both the amplitude and phase of a signal.

[0102] (11).

[0103] in, for x ( t Hilbert transform of ) j The imaginary unit is used. This transformation effectively introduces a 90° phase shift in the frequency domain, thus constructing an imaginary part signal orthogonal to the original signal. The amplitude of the analytic signal corresponds to the instantaneous amplitude of the signal.

[0104] (12).

[0105] instantaneous amplitude This is the envelope of the signal, which reflects the energy change characteristics of the signal in the time domain, and thus yields the curve of magnetic field strength changing with time.

[0106] (2) Loess smoothing algorithm: In order to reduce the impact of signal noise on subsequent feature extraction, the Loess (locally weighted scatter smoothing) local weighted regression algorithm is used to smooth the original signal. The Loess algorithm is a non-parametric regression method. Its basic calculation idea is: select data points within a specified range near each sampling point of the signal; use the weighted least squares method to perform low-order polynomial fitting on the local dataset; and use the fitting result as the smoothed output value.

[0107] (3) Wavelet Transform Denoising Algorithm: To improve the signal-to-noise ratio and suppress random noise interference, a wavelet transform (WT)-based denoising algorithm is used to preprocess the original signal. Its basic principle is to decompose the original signal into multiple scales using wavelet basis functions, obtaining approximate components and detail components in different frequency bands. Noise mainly exists in the high-frequency detail components, while the effective signal is mainly distributed in the low-frequency region. By thresholding the coefficients of the high-frequency detail components (i.e., wavelet threshold denoising), noise components can be effectively removed while preserving the main characteristic information of the signal.

[0108] Figure 13 The results of defect signal extraction before and after signal preprocessing are shown. Figure 13 (a) in the diagram is a schematic of the signal before processing; Figure 13 (b) is a schematic diagram of the processed signal. The processed data not only retains the main characteristics of the defective signal in the original data, but also filters out the signal noise components in the original signal. To evaluate the signal error before and after preprocessing, the root mean square error (RMSE) method is used for quantitative calculation, and the calculation formula is shown below.

[0109] (13).

[0110] in, For the true value, This is an estimated value. N The total number of samples is represented by . The smaller the root mean square error (RMSE), the better the estimation result fits the true signal, reflecting better algorithm accuracy. The calculation results show that the RMSE after signal preprocessing is only 0.0763, indicating that the algorithm effectively extracts defect signals from the original signal while significantly reducing noise in the signal.

[0111] To verify the reliability of the finite element simulation results, actual scanning tests were conducted on multiple simulation scenarios. Figure 14 and Figure 15 The results of scanning typical cracks and corrosion defects using single-coil and dual-coil probes under two excitation conditions are presented. (Comparison) Figure 14 (a) and Figure 14 As shown in result (b), the defect signal characteristics of single-coil excitation and reverse-excitation dual-coil are similar, but the peak-to-peak amplitude of the signal from the dual-coil probe is higher. The baseline signal of the reverse-excitation dual-coil is about 0.5V higher than that of the single-coil probe. The crack detection results of the co-excitation dual-coil probe are as follows: Figure 14 As shown in (c) above. Similarly, Figure 15 (a) and Figure 15 Similar results were obtained in (b) of the above, consistent with the eddy field distribution observed in finite element simulations of both excitation models. However, Figure 15 (c) in the basic defect scan shows the same characteristics as Figure 15 (a) and Figure 15 The signal characteristics in (b) are completely different because, unlike the excitation model described above, the in-phase excitation of the dual coils generates a uniform unidirectional eddy current field in the magnetic sensor region, which significantly reduces the baseline value of the scan signal to 2.5V. This result also reduces the background noise of the sensor, thereby improving the signal-to-noise ratio.

[0112] For eddy current probes using different excitation configurations, the response signals acquired for different defect types typically exhibit different amplitude and phase characteristics. To objectively quantify the performance of each excitation model and evaluate the detectability of the designed probe, this embodiment uses the detection signal-to-noise ratio (SNR) as the primary evaluation metric. The detection SNR reflects the ratio of the effective signal change induced by the defect during scanning to the background noise level, thus directly measuring the probe's sensitivity and robustness under actual detection conditions. The SNR calculation formula used in this embodiment is shown below.

[0113] (14).

[0114] in, V aD and V aN These represent the average voltage changes in the defective and non-defective regions of the test specimen, respectively.

[0115] As shown in Table 3, the signal-to-noise ratio (SNR) results for the baseline defects under different excitation configurations reveal significant performance differences among the designed probes. Although the reverse-current-excited dual-coil probe exhibits a slight increase in the original signal amplitude compared to the single-coil configuration, the calculated SNR indicates that the single-coil probe possesses superior noise suppression and overall detectability. Conversely, the co-current-driven dual-coil probe demonstrates the best detection performance across all models, achieving an SNR of 27.6 dB for crack defects and 39.46 dB for corrosion defects. These results highlight the significant advantage of constructive magnetic field superposition in enhancing defect-induced perturbations while minimizing background noise.

[0116] Table 3. Signal-to-noise ratio of defect detection under different excitation modes

[0117] Based on the aforementioned experimental comparisons, the co-directional excitation dual-coil configuration was determined as the optimal excitation scheme due to its superior signal-to-noise ratio performance. To further verify the robustness of this configuration under actual testing conditions, a series of lift-off-related scanning experiments were conducted using ferromagnetic steel specimens containing cracks of varying depths. Figure 16 As shown, the probe was tested within a lift-off range of 0 mm to 3 mm, with increments of 0.5 mm.

[0118] Figure 16 As shown in (a), the crack response exhibits a characteristic peak-valley waveform at all lift-off heights. Furthermore, the peak-to-peak amplitude continuously increases as the crack depth changes from 2 mm to 5 mm, indicating that the dual-coil probe maintains strong detectability for both shallow and deeper surface cracks within a 3 mm lift-off tolerance. This also demonstrates that the probe can detect crack depth differences based on amplitude variations.

[0119] Figure 16 Figure (b) shows the calculated signal-to-noise ratio (SNR) at each lift-off height, which decreases almost linearly from approximately 26 dB at zero lift-off to approximately 16 dB at 3 mm. This behavior reflects the expected attenuation of the induced magnetic field and the increased influence of ambient noise as the probe distance from the surface increases, but the SNR remains sufficient to ensure reliable crack detection throughout the test lift-off range.

[0120] like Figure 17 As shown, additional lift-off correlation experiments were conducted to evaluate the probe's response to corrosion defects of gradually increasing depth. From Figure 17 As can be seen in (a), compared to crack detection, the dual-coil probe produces a slightly larger peak-to-peak response when scanning the corroded area, indicating that the defect features are more obvious. However, this enhanced response comes at the cost of a reduced ability to distinguish deeper corrosion. Specifically, when the corrosion depth exceeds approximately 2.4 mm (corresponding to defect #10), the peak-to-peak amplitude no longer increases with further defect depth, indicating a saturation effect in the magnetic field disturbance generated by volumetric corrosion.

[0121] Figure 17 Figure (b) shows the calculated signal-to-noise ratio (SNR) for corrosion detection at different lift-off heights. The SNR drops sharply as the probe transitions from zero lift-off to finite lift-off conditions, reflecting the rapid attenuation of the defect-induced magnetic signal during probe separation from the specimen surface. After the initial drop, the SNR continues to decrease almost linearly with increasing lift-off, consistent with the gradual attenuation of the effective excitation field and the increasing influence of ambient noise. Despite this attenuation, the SNR remains sufficient to ensure reliable identification of corrosion defects within the tested lift-off range.

[0122] To further evaluate the capabilities of the proposed dual-coil probe in complex detection scenarios, composite defect specimens containing surface corrosion pits and buried cracks were fabricated and tested. For conventional eddy current probes employing coil receiving structures, such composite defects (especially those involving large-area corrosion) typically lead to significant changes in lift-off, which severely attenuate the acquired defect signal, resulting in a blurred corrosion response and difficulty in detecting cracks within the corroded area.

[0123] The dual-coil excited eddy current probe integrating a TMR magnetic sensing chip significantly mitigates these limitations. For example... Figure 18As shown, the probe produced a clear and distinguishable response when scanning the composite defect specimen. For comparison, corrosion specimens of the same size but without cracks were also measured. The results indicate that for composite defects, the signal retains the characteristic boundary transitions associated with corrosion pits, while the overall amplitude within the corroded area is slightly lower than the baseline level of the defect-free surface. More importantly, distinct peak-valley features corresponding to buried cracks can be clearly observed within the corroded area, indicating successful detection of both defect components.

[0124] These findings confirm that the proposed probe maintains robust sensitivity even under large lift-off perturbations and exhibits strong detectability for corrosion-crack composite defects, highlighting its significant performance advantages in complex testing environments.

[0125] In summary, this application proposes a novel dual-excitation coil eddy current probe integrating a TMR magnetic sensor, aiming to improve the detection sensitivity and signal-to-noise ratio of complex composite defects. From the perspective of excitation source design, the configuration of the excitation coils is optimized to enhance the electromagnetic coupling effect. Vector expressions for magnetic induction intensity and eddy current density are derived, and various excitation models are evaluated through finite element simulation, followed by experimental verification through scanning tests. The results show that the proposed dual-coil excitation scheme provides an effective means to enhance electromagnetic coupling and strengthen defect-induced magnetic response. The main conclusions of this application are as follows.

[0126] (1) Finite element simulation comparisons of single-coil excitation, reverse current double-coil excitation, and co-current double-coil excitation show that the co-current double-coil configuration achieves significant field enhancement. Specifically, the magnetic induction intensity in the central detection region is increased by more than three times compared to single-coil excitation and by more than 2.5 times compared to reverse double-coil excitation.

[0127] (2) The proposed co-directional dual-coil probe provides significantly improved detection sensitivity and signal-to-noise ratio in eddy current testing. For typical crack defects, the signal-to-noise ratio of the co-directional dual-coil probe is 10.1 dB higher than that of the single-coil probe and 16.4 dB higher than that of the reverse dual-coil probe; for corrosion defects, the signal-to-noise ratio is improved by 15.8 dB compared with the single-coil model and by 11.4 dB compared with the reverse model.

[0128] (3) The probe demonstrates strong ability to detect complex defects (such as buried cracks in corrosion pits), even under large lift-off disturbances. Experimental results show that the probe can clearly distinguish corrosion boundaries and crack-induced peak-valley features.

[0129] In one exemplary embodiment, a computer device is provided, which may be a server or a terminal, and its internal structure diagram may be as follows. Figure 19As shown, the computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores magnetic field signals. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a method for detecting eddy currents through arrayed coil excitation coupling.

[0130] Those skilled in the art will understand that Figure 19 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0131] In one exemplary embodiment, a computer device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-described method embodiments.

[0132] In one exemplary embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the above-described method embodiments.

[0133] In one exemplary embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the above-described method embodiments.

[0134] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0135] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0136] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0137] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0138] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An array coil excitation coupled eddy current detection probe, characterized in that, The array coil excitation coupling eddy current detection probe includes: Dual-coil excitation module and sensing module; The dual-coil excitation module includes two semi-circular Helmholtz coils; the two semi-circular Helmholtz coils are symmetrically arranged, parallel and coaxial, and are energized with AC excitation current of the same direction, frequency and phase; the spacing between the two semi-circular Helmholtz coils is adjustable. The sensing module is located in the central region of the two semi-circular Helmholtz coils and is used to detect the magnetic field changes caused by the eddy current field at the defect.

2. The array coil excitation coupling eddy current detection probe according to claim 1, characterized in that, Each semi-circular Helmholtz coil is made of copper wire with 100-200 turns, an excitation frequency of 5kHz-30kHz, and a current amplitude of 1A.

3. The array coil excitation coupling eddy current detection probe according to claim 1, characterized in that, The sensing module is a TMR linear magnetic sensor.

4. The array coil excitation coupling eddy current detection probe according to claim 1, characterized in that, The dual-coil excitation module and the sensing module are fixed inside a 3D-printed resin shell, and the outside is encapsulated with epoxy resin to form an integrated probe.

5. The array coil excitation coupling eddy current detection probe according to claim 1, characterized in that, The array coil excitation coupled eddy current detection probe is equipped with a wear-resistant plate at the bottom to adapt to the sliding detection of the inner wall of the pipeline.

6. An array coil excitation coupling eddy current detection system, characterized in that, The array coil excitation coupling eddy current detection system includes: The device comprises a probe, an in-pipe detector, an excitation signal source, a signal conditioning circuit, and a data acquisition and processing module; the probe is the array coil excitation coupled eddy current detection probe according to any one of claims 1-5. The probe is installed on the detector inside the pipeline; The pipe detector moves along the pipe axis inside the pipe. The excitation signal source is connected to the two semi-circular Helmholtz coils of the probe respectively. A function generator generates a sinusoidal excitation signal, which is then amplified and impedance matched by a power amplifier circuit to drive the two semi-circular Helmholtz coils simultaneously. The signal conditioning circuit is connected to the sensing module of the probe and is used to extract the magnetic field signal of the sensing module. The data acquisition and processing module, connected to the signal conditioning circuit, is used to acquire the magnetic field signal in real time using a high-speed acquisition card, and extract defect features through processing algorithms in the host computer software; identify the defect type and evaluate the size based on the defect features; the processing algorithm includes: Hilbert transform to extract the signal envelope, local weighted regression smoothing, and wavelet threshold denoising; the defect features include: signal amplitude and waveform characteristics; the defect types include: cracks, corrosion, and composite defects.

7. The array coil excitation coupling eddy current detection system according to claim 6, characterized in that, The signal conditioning circuit includes: a differential amplifier circuit, a bandpass filter circuit, and a programmable gain amplifier circuit.

8. A method for detecting eddy currents coupled to excitation in an array coil, characterized in that, The array coil excitation coupling eddy current detection method is implemented based on the array coil excitation coupling eddy current detection system according to claim 6 or 7, and the array coil excitation coupling eddy current detection method includes: Acquire magnetic field signal; the magnetic field signal is obtained by installing the probe on the detector inside the pipe, moving it along the pipe axis inside the pipe, and passing an AC excitation current with the same direction, frequency and phase to two semi-circular Helmholtz coils to induce an enhanced eddy current field inside the pipe wall, and then detecting the signal caused by the distortion of the eddy current field in real time through the sensing module. After conditioning and acquiring the magnetic field signal, defect features are extracted through a processing algorithm. The processing algorithm includes: Hilbert transform to extract the signal envelope, local weighted regression smoothing, and wavelet thresholding for denoising. The defect features include: the amplitude and waveform characteristics of the signal. The defect type is identified and the size is evaluated based on the defect characteristics; the defect types include: cracks, corrosion and composite defects.

9. A computer device, comprising: A memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that the processor executes the computer program to implement the array coil excitation coupling eddy current detection method of claim 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the array coil excitation coupling eddy current detection method as described in claim 8.

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