Variable focus pipe non-destructive testing instrument and flaw detection method for coated metal walls

Abstract

This invention relates to the field of electromagnetic nondestructive testing, specifically a zoom-type pipeline nondestructive testing instrument and a method for detecting defects in coated metal walls. The instrument includes a probe, an excitation source, a signal receiver, and a controller. In the probe, each excitation coil and detection coil is connected to a support via an independent movable joint; the movable joint is used to adjust the orientation of the excitation coil or detection coil. The excitation source is electrically connected to each excitation coil and outputs an excitation signal to it; the signal receiver is electrically connected to the detection coil and acquires the induced signal from the detection coil. The controller adjusts the orientation of the movable joints according to the coating thickness, outer diameter, and wall thickness of the pipeline under test, so that the orientation of each excitation coil and detection coil intersects at the defect location on the pipeline wall under test, thereby enhancing the received induced signal. This invention solves the technical problem that existing pulsed eddy current testing technology cannot meet the requirements for detecting localized corrosion defects in coated pipelines and containers.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic nondestructive testing, and in particular to a zoom-type pipeline nondestructive testing instrument and the flaw detection method used for the coated metal wall surface. Background Technology

[0002] In industrial applications, localized radiation, cracks, or other defects in the walls of pipes or containers can lead to damage, resulting in leakage of contents and serious production safety accidents. To detect such risks promptly, technicians need to conduct regular inspections. To enable damage inspection of pipe or container walls while in service, technicians have developed various non-destructive testing (NDT) techniques.

[0003] Eddy current testing is a non-destructive testing method that utilizes the principle of electromagnetic induction to non-destructively evaluate certain properties of conductive materials and workpieces or detect defects by measuring changes in induced eddy currents within the workpiece. It is widely used in aerospace, metallurgy, machinery, power, chemical, and nuclear energy fields for non-contact inspection of internal damage in various metal workpieces. An eddy current testing-based non-destructive testing instrument includes an excitation coil and a detection coil. The excitation coil applies a detection alternating magnetic field to the target area of ​​the workpiece, while the detection coil receives the induced magnetic field generated in the target area under the alternating magnetic field. By monitoring the impedance change of the detection coil, defects in the target area of ​​the tested object can be analyzed. Besides detecting surface defects in conductive materials, it can also be widely used to measure the thickness of surface coatings and the electrical conductivity of materials.

[0004] While eddy current testing technology can efficiently perform non-destructive testing on metal containers or pipes, its detection depth is limited. It typically only analyzes surface and near-surface defects, making it difficult to inspect deep-seated defects within the pipe or container walls. For this reason, the accuracy of such non-destructive testing equipment is relatively poor in pipes or containers with cladding. To inspect clad pipes, technicians usually need to improve magnetic field penetration and enhance defect detection sensitivity by increasing excitation energy, optimizing coil structure, and introducing magnetic yokes or bias magnetic fields. Even so, a single flaw detector cannot be applied to diverse testing scenarios where pipe diameter, wall thickness, or cladding thickness varies. Summary of the Invention

[0005] To address the problem that existing pulsed eddy current testing technology cannot be applied to flaw detection of pipes or containers with coatings, this invention provides a zoom-type non-destructive testing instrument for pipes and a flaw detection method for coated metal walls.

[0006] The technical solution provided by this invention is as follows:

[0007] A zoom-type non-destructive testing instrument for pipelines includes: a probe, an excitation source, a signal receiver, and a controller. The probe includes a support with an inner surface conforming to the shape of the pipeline to be tested. Multiple excitation coils and at least one detection coil are spaced apart on the outer side of the support; each excitation coil and detection coil is connected to the support via an independent movable joint; the movable joint is used to adjust the orientation of the excitation coil or detection coil. The excitation source is electrically connected to each excitation coil and outputs an excitation signal to it. The signal receiver is electrically connected to the detection coil and acquires the induced signal from the detection coil.

[0008] The controller is electrically connected to the movable joints, excitation source, and signal receiver. The controller adaptively adjusts the posture of each movable joint based on the coating thickness, outer diameter, and wall thickness of the pipe under test, ensuring that the rotational symmetry axes of the excitation coils and detection coils intersect at any specified position on the pipe wall. This intersection point is designated as the focal point for non-destructive testing. The controller also controls the excitation source to output an excitation signal to this focal point to enhance the inductive signal at the corresponding position in the signal receiver, thereby retrieving the defect distribution near the focal point. During this process, the pipe under test can be scanned by adjusting the position of the focal point (which can be achieved by moving the probe radially or axially along the pipe, or by adjusting the orientation of the excitation coils and detection coils).

[0009] As a further improvement of the present invention, the support is semi-circular, and each excitation coil is evenly distributed along the outer periphery of the support. The movable joint is used to control the orientation of each excitation coil or detection coil to rotate in a space parallel to the plane of the semi-circular support.

[0010] As a further improvement of the present invention, the back of the bracket includes a semi-annular groove; in the two side walls of the groove, a set of through holes with opposite positions are provided at the mounting positions of each excitation coil or detection coil.

[0011] The movable joint includes an adjusting rod and a drive motor. The adjusting rod consists of a horizontal bar and a vertical bar connected in a T-shape or cross shape. Both ends of the horizontal bar are rotatably connected to a support through through holes, allowing the vertical bar to rotate about the horizontal bar as an axis in a plane parallel to the support. An excitation coil or detection coil is sleeved on the vertical bar. The drive motor is used to drive the horizontal bar to rotate.

[0012] As a further improvement of the present invention, the output shaft of the drive motor is keyed to the crossbar of the adjusting rod to achieve shaft transmission. Alternatively, a gear with teeth arranged circumferentially on the crossbar is provided, and the drive motor and the adjusting rod are connected by gear transmission.

[0013] As a further improvement of the present invention, the probe also includes a bias magnetic field generator, which is used to make a specified range around the focal point of the pipe under test in a bias magnetic field of preset intensity.

[0014] As a further improvement of the present invention, the bias magnetic field generator uses a detachable permanent magnet.

[0015] As a further improvement of the present invention, the bias magnetic field generator includes a U-shaped magnetic yoke and a first coil wound on it. The two ends of a support are fixedly connected to the inside of the U-shaped opening of the magnetic yoke, and the curved surface of the support is located on the side away from the magnetic yoke. The first coil is electrically connected to an excitation source, which outputs a DC signal to the first coil to generate a bias magnetic field.

[0016] As a further improvement of the present invention, the detection coil includes two sets, which are symmetrically distributed radially along the pipe where the focal point is located, so as to realize differential detection of defects at the focal point.

[0017] As a further improvement of the present invention, the variable-focus pipe non-destructive testing instrument also includes a carrier for loading the probe. The carrier is electrically connected to a controller, which controls the movement of the carrier along the surface of the object being tested, thereby enabling the scanning of the object.

[0018] As a further improvement of the present invention, the controller pre-stores a first mapping relationship F1 and a second mapping relationship F2 obtained through experimental calibration or numerical simulation.

[0019] The first mapping relationship F1 is used to characterize any coating layer thickness H. c Pipe outer diameter D o and pipe wall thickness T w Corresponding focus depth Z f Effective range D f :

[0020] D f =F1(H c D o ,T w ).

[0021] The second mapping relationship F2 is used to characterize each active joint in any posture A1~A2. n The corresponding focus depth Z f :

[0022] Z f =F2(A1~A n );

[0023] In the above formula, n represents the number of movable joints.

[0024] The controller uses a first mapping relationship and a second mapping relationship to adaptively adjust the posture of each movable joint according to the coating thickness, outer diameter and wall thickness of the pipe under test.

[0025] This invention also includes a flaw detection method for coated metal walls. As described above, the zoom-type pipe non-destructive testing instrument uses this method to perform non-destructive testing on coated pipes. In fact, the method of this invention can also be extended to the inspection of any non-pipeline metal wall surface.

[0026] The flaw detection method for coated metal walls provided by this invention includes the following steps:

[0027] Several excitation coils with different positions and orientations and at least one detection coil are set outside the object being tested.

[0028] The orientation of each excitation coil and detection coil is adjusted so that their respective axes of rotational symmetry intersect at any depth between the inner and outer walls of the metal surface under test; this intersection point is denoted as the focal point. A synchronous excitation source is sent to each excitation coil to generate a pulsed eddy current signal of the target intensity at the focal point; and the induced magnetic field generated by the pulsed eddy current signal at the focal point is received by the detection coil, so as to realize the defect distribution around the focal point based on the induced signal.

[0029] Based on this, this embodiment adjusts the orientation of each excitation coil and detection coil in combination, and / or adjusts the position of the combination of excitation coil and detection coil to change the position of the focal point, so that the focal point traverses the target area to be measured within the metal wall to achieve scanning, and visualizes the defect distribution within the target area in the metal wall based on the scanning results.

[0030] As a further improvement of the present invention, if the metal wall surface is magnetically conductive, a DC bias magnetic field covering the focal point and its visible range is generated simultaneously during the scanning process to overcome the skin effect of the magnetic field of the magnetically conductive material.

[0031] As a further improvement of the present invention, the scanning method for the target area in the metal wall surface to be tested includes:

[0032] The target area is divided into several target layers according to a preset depth. A dot matrix with preset intervals is generated on each target layer based on the visible range, and the spatial position of each point in the dot matrix is ​​determined. Then, the orientation of each excitation coil and detection coil is jointly adjusted so that the focal point sequentially traverses each point in each target layer to complete the scanning of the target area.

[0033] Alternatively, the target area can be divided into several target layers according to a preset depth; a dot matrix with preset intervals can be generated on each target layer based on the visible range, and the spatial position of each point in the dot matrix can be determined; then, the orientation of each excitation coil and detection coil can be jointly adjusted so that the depth of the focal point corresponds to the depth of one of the target layers; next, the position of the combination of excitation coil and detection coil can be moved outside the metal wall so that the focal point traverses all points in the target layer at the current depth in sequence, completing the scan of the current target layer; then, the orientation of each excitation coil and detection coil can be jointly adjusted so that the focal point is located at the depth corresponding to the next target layer, and the aforementioned scanning strategy can be repeated until the scanning task of all target layers is completed.

[0034] As a further improvement of the present invention, the maximum range of the defect distribution that can be inverted by the induction signal at any focal point is the visible range; the distance between adjacent points in the dot matrix is ​​less than the radius of the visible range.

[0035] As a further improvement of the present invention, by adjusting the number of activated excitation coils and the power of the excitation source, the intensity of the pulse eddy current signal at the furthest focal point that the probe can reach is still not less than the preset intensity when the spatial position of the probe remains fixed.

[0036] As a further improvement of the present invention, the method for visualizing the defect distribution within a target area in a metal wall includes:

[0037] The defect distribution information at the focal point can be retrieved based on the amplitude change of the induced signal, and / or the phase shift angle, and / or the signal rise time.

[0038] A planar image representing the layer-by-layer defect distribution of the target region of the metal wall at the corresponding depth can be synthesized based on the defect distribution inverted at each point in any target layer. Alternatively, a three-dimensional image representing the defect distribution within the target region of the metal wall can be synthesized based on the defect distribution inverted at each point in all target layers.

[0039] The present invention has the following beneficial effects:

[0040] This invention provides a zoom-type non-destructive testing instrument for pipelines and a method for testing coated metal walls. The probe of the non-destructive testing instrument integrates multiple sets of interconnected excitation coils and detection coils, and supports dynamic adjustment of the orientation of each coil through movable joints, thereby realizing "focused" flaw detection of any area inside the object being tested.

[0041] Based on the controllable focus position of the probe and the ability to flexibly adjust the magnetic field focusing position according to the target in the radial direction of the pipe, the solution of this invention can significantly improve the targeting of internal and external wall defects, avoiding the problem that a single probe cannot simultaneously measure different defects on both internal and external walls. In practical applications, the solution of this invention can adapt to cladding layers of different thicknesses and pipes of different specifications, and supports adaptive focusing adjustment based on parameter input via a controller, thereby improving the engineering applicability of the technical solution. Attached Figure Description

[0042] Figure 1 This is a system architecture diagram of the zoom-type pipeline non-destructive testing instrument provided in Embodiment 1 of the present invention.

[0043] Figure 2 This is a schematic diagram of the probe portion of the zoom-type pipeline non-destructive testing instrument provided in Embodiment 1 of the present invention.

[0044] Figure 3 This is a disassembly diagram of the probe portion of Embodiment 1 of the present invention.

[0045] Figure 4 A schematic diagram of the structure of the adjusting rod in the probe of Embodiment 1 of the present invention.

[0046] Figure 5 The curves show the changes in the material's magnetic permeability and magnetic field strength as a function of the applied magnetic field strength.

[0047] Figure 6 This is a schematic diagram of the probe with a permanent magnet type bias magnetic field generator in Embodiment 1 of the present invention.

[0048] Figure 7 This is a schematic diagram of the probe with an electromagnet-type bias magnetic field generator in Embodiment 1 of the present invention.

[0049] Figure 8 This is a scene diagram showing the focus point at the center of the pipe in the external wall defect detection task of the simulation experiment.

[0050] Figure 9 This is a scene diagram showing the focus point on the pipe wall in the simulation experiment's task of detecting defects on the outer wall.

[0051] Figure 10 for Figure 8 Waveform of the sensing signal corresponding to the scene.

[0052] Figure 11 for Figure 8 Signal cloud field diagram corresponding to the scene.

[0053] Figure 12 for Figure 9 Waveform of the sensing signal corresponding to the scene.

[0054] Figure 13 for Figure 9 Signal cloud field diagram corresponding to the scene.

[0055] Figure 14 This is a scene diagram showing the focus point at the center of the pipe in the internal wall defect detection task of the simulation experiment.

[0056] Figure 15 This is a scene diagram showing the focus point on the inside of the pipe wall during the simulation experiment's internal wall defect detection task.

[0057] Figure 16 for Figure 14 Waveform of the sensing signal corresponding to the scene.

[0058] Figure 17 for Figure 14 Signal cloud field diagram corresponding to the scene.

[0059] Figure 18 for Figure 15 Waveform of the sensing signal corresponding to the scene.

[0060] Figure 19 for Figure 15 Signal cloud field diagram corresponding to the scene.

[0061] The diagram is marked as follows:

[0062] 1. Probe; 5. Bias magnetic field generator; 11. Support; 12. Excitation coil; 13. Detection coil; 14. Movable joint; 130. Adjusting rod; 1301. Vertical rod; 1302. Horizontal rod; 1303. Gear. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0065] Example 1

[0066] To address the problem that existing non-destructive testing (NDT) devices based on pulsed eddy current testing technology cannot achieve "efficient penetration" of coated metal materials, thus hindering the detection of deep-seated defects on the surface and within the material under test, this embodiment proposes a zoom-type pipeline NDT instrument based on the vector superposition effect of magnetic fields. In this embodiment, the excitation coil 12 and detection coil 13, which are fixedly installed and arranged in a planar array in the original pulsed eddy current testing probe, are designed to be directionally adjustable, and are arranged to be distributed circumferentially along the object under test.

[0067] In this state, the spatial range of the excitation magnetic fields generated by each excitation coil 12 is similar, and the direction of each excitation magnetic field is directional. In this embodiment, by adjusting the orientation of each excitation coil 12, the extension direction of its central rotational symmetry axis (hereinafter referred to as the coil orientation) intersects at a point. Based on the principle of magnetic field superposition, it can be known that the magnetic field strength of the excitation magnetic field at this point is the highest. In this embodiment, this point is denoted as the "focal point"; the distortion of the induced signal caused by the defect at the corresponding focal point is also the strongest.

[0068] Considering that the detection coil 13, when used as a signal receiving unit, has a certain directionality in receiving the induced signal, and that the detection coil 13 has the highest reception rate for induced signals in the direction directly facing itself, this embodiment further adjusts the orientation of the detection coil 13, based on the previously described adjustment of the orientation of the excitation coil 12, so that it faces the focal point, i.e., the orientation of the detection coil 13 intersects with the focal point. Therefore, the detection coil 13 can more efficiently receive the distortion of the induced signal caused by the defect at the focal point.

[0069] In summary, this embodiment, by jointly controlling the orientation of the excitation coil 12 and the detection coil 13, essentially achieves "focusing" and "seeing through" any point in the detection area near the probe 1. This lays the foundation for internal flaw detection of objects with cladding layers and uneven cladding layer thickness or uneven thickness of the metal wall to be tested.

[0070] Based on the above principles, such as Figure 1 As shown, the zoom-type pipeline non-destructive testing instrument provided in this embodiment includes a probe 1, an excitation source, a signal receiver, and a controller. The excitation source is electrically connected to each excitation coil 12 and is used to output excitation signals to them. The signal receiver is electrically connected to the detection coil 13 and is used to acquire the induced signals of the detection coil 13. The controller serves as the control center of the entire testing instrument and is used to control the operating status of other electrical control components.

[0071] Among them, such as Figure 2 and Figure 3As shown, probe 1 includes a support 11, an excitation coil 12, a detection coil 13, and a movable joint 14. The support 11 is preferably made of a non-magnetic material, such as ceramic, glass, or polymer. The movable joint 14 is used to mount the excitation coil 12 or detection coil 13 on the support 11, ensuring that the relative positions of each excitation coil 12 and detection coil 13 remain fixed, but allowing adjustment of the orientation of each excitation coil 12 or detection coil 13 on the support 11. This embodiment does not limit the structure of the support 11. In practical applications, to be suitable for detecting pipes (especially the most common circular pipes), the inner side of the support 11 in this embodiment has a curved surface that conforms to the shape of the pipe to be tested. The outer contour of this curved surface can be semi-circular or a minor arc with a curvature less than a semi-circle, so that the same probe 1 can be used to detect pipes with different diameters. Multiple excitation coils 12 and at least one detection coil 13 are spaced apart on the outer side of the support 11; each excitation coil 12 and detection coil 13 is connected to the support 11 through an independent movable joint 14.

[0072] In practical applications, considering that a circular pipe is a tensile body with a circular cross-section, when performing pipe wall flaw detection, the orientation of the excitation coil 12 and the detection coil 13 can be adjusted so that the focal points are located at different depths in any radial direction within the pipe cross-section. Then, by translating and rotating the support 11 circumferentially and radially within the pipe, detection can be performed at any position on the inner wall of the pipe. Therefore, this embodiment simplifies the degrees of freedom and control strategy of the movable joint 14 connecting the various excitation coils 12 and detection coils 13 mounted on the support 11.

[0073] Specifically, in a typical solution of this embodiment, such as Figure 2 As shown, the support 11 can be semi-circular, with each excitation coil evenly distributed along the outer periphery of the support 11. Each movable joint 14 has only one degree of freedom and can control the orientation of each excitation coil 12 or detection coil 13 to rotate in space parallel to the plane of the semi-circular support 11. When the support 11 is positioned aligned with the pipe, by adjusting the orientation of all excitation coils 12 and detection coils 13, the focal point can move freely radially along the circular pipe section below the support 11.

[0074] Of course, it should be noted that, given the available technical conditions, manufacturing costs, and the ability to manipulate the movable joint 14, the movable joint 14 in this embodiment can also be a multi-degree-of-freedom micro-joint. This allows for the joint adjustment of the orientation of all excitation coils 12 and detection coils 13 via the various movable joints 14, ensuring the focal point falls at any position on the lower pipe wall. This enables spatial scanning of different positions on the pipe wall without relying on the translation and rotation of the support 11.

[0075] In practical applications, to facilitate the installation of the excitation coil 12 and the detection coil 13, the back of the bracket 11 in this embodiment includes a semi-annular groove; in the two side walls of the groove, a set of through holes with opposite positions are provided corresponding to the installation positions of each excitation coil 12 or detection coil 13. Correspondingly, the movable joint 14 in this embodiment includes an adjusting rod 130 and a drive motor. Figure 4 As shown, the adjusting rod 130 includes a horizontal rod 1302 and a vertical rod 1301 connected in a T-shape or cross shape. The two ends of the horizontal rod 1302 are rotatably connected to the bracket 11 through through holes, allowing the vertical rod 1301 to rotate about the horizontal rod 1302 as an axis along a plane parallel to the bracket 11. In this embodiment, the excitation coil 12 or detection coil 13 is sleeved on the vertical rod 1301 of the movable joint 14. The horizontal rod 1302 is driven to rotate by a drive motor to adjust the orientation of each excitation coil 12 or detection coil 13 within the same plane. The output shaft of the drive motor can be keyed to the horizontal rod 1302 of the adjusting rod 130 to achieve shaft transmission; in this case, the drive motor should be placed outside the groove in the bracket 11. In a more optimized solution, such as... Figure 4 As shown, a gear 1303 with teeth arranged circumferentially on the crossbar 1302 can be provided, and the drive motor and the adjusting rod 130 are connected by the gear 1303. In this case, as long as the transmission gear 1303 is set on the inner side near the vertical bar 1301, the drive motor can be installed in the groove, thereby achieving a more efficient space integration and protection effect.

[0076] In this embodiment, the controller is electrically connected to the movable joint 14, the excitation source, and the signal receiver. The controller in this embodiment has the following functions: First, it issues attitude control commands to each movable joint 14, adjusting the orientation of each excitation coil 12 and detection coil 13 so that the focusing depth of the probe 1's focal point is at its proper position. Second, it controls the excitation source to synchronously output corresponding excitation signals to each activated excitation coil 12, thereby generating the required alternating magnetic field at the focal point. Third, while the excitation source controls the generation of the alternating magnetic field at the focal point, it controls the signal receiver to receive the induced magnetic field generated by the eddy currents in the target material at the focal point under the excitation of the alternating magnetic field through the detection coil 13. Fourth, it performs signal analysis on the induced signal obtained by the signal receiver, thereby retrieving the defect distribution at the focal point in the metal tube under test.

[0077] In practical applications, to automate the detection process, the controller in this embodiment adaptively adjusts the posture of each movable joint 14 based on the coating thickness, outer diameter, and wall thickness of the pipe under test, so that the rotational symmetry axes of each excitation coil 12 and detection coil 13 intersect at any specified position on the wall surface of the pipe under test. The strategy for the controller to adaptively adjust the posture of each movable joint 14 is as follows:

[0078] First, the controller pre-stores a first mapping relationship F1 and a second mapping relationship F2 obtained through experimental calibration or numerical simulation. The first mapping relationship F1 is used to characterize any coating layer thickness H. c Pipe outer diameter D o and pipe wall thickness T w Corresponding focus depth Z f Effective range D f :

[0079] D f =F1(H c D o ,T w ).

[0080] In the non-destructive testing instrument provided in this embodiment, the effective range of the focusing depth of probe 1 during actual testing should exactly cover all solid areas of the pipe wall composed of metallic material between the inner and outer walls of the pipe. The corresponding depth range is determined by the pipe wall thickness T. w The decision is made. However, in actual testing, the spatial coordinates of this section are affected by the thickness of the protective layer and the outer diameter of the pipe. Therefore, this embodiment can pre-determine the focusing depth Z under the current measurement conditions of probe 1 through simulation. f Effective range D f With any coating thickness H c Pipe outer diameter D o and pipe wall thickness T w The mapping relationship between the ternary parameters. This allows for the direct output of D once the parameters of the three parameters are determined. f In later measurements, it is only necessary to control the depth of the focal point to be within the range of the upper and lower limits.

[0081] Correspondingly, in order to ensure the focusing depth Z of probe 1 during actual detection... f To effectively cover this range, this embodiment also requires prior simulation or experimental determination to ensure that the focusing depth of probe 1 reaches the effective range D. fThe pose of each movable joint 14 is defined by any value within the range. In this embodiment, when the position of the movable joint 14 is fixed and it rotates only in one direction, there is only one feasible solution for the pose (i.e., the corresponding rotation angle value) of each movable joint 14 at any depth of focus.

[0082] In a more optimized scheme, when the degrees of freedom of the movable joint 14 are higher, even allowing adjustment of the spatial position of each coil, the space of feasible solutions for the attitude (and position) of each movable joint 14 at any focusing depth will be much larger. To improve real-time performance in practical applications, this embodiment can select several sets of feasible solutions as effective solutions and construct a second mapping relationship. Based on this, when the controller performs attitude control, it does not need to solve the attitude of each movable joint 14 at the target focusing depth in real time; it only needs to output any feasible solution according to the pre-established second mapping relationship.

[0083] In summary, this embodiment can directly establish a second mapping relationship between the pose and focus depth values ​​of each key activity. In this embodiment, the second mapping relationship F2 is used to characterize each active joint 14 in any pose A1~A2. n The corresponding focus depth Z f :

[0084] Z f =F2(A1~A n );

[0085] In the above formula, n represents the number of movable joints 14.

[0086] In this embodiment, the number of excitation coils 12 involved in the excitation can be adjusted when the focusing depth is at different positions; that is, n is a variable related to Z. f The value of the variable is related to the value of the variable. For example, in the detection of surface or shallow defects of the object under test (Z). f When the value is smaller, fewer excitation coils 12 can be used; at this time, the output power of the excitation source is lower. However, when detecting deep defects in the object under test (Z...),... f When the value is larger, more or all of the excitation coils 12 are activated to participate in the operation; at this time, the output power of the excitation source is higher. In this embodiment, the intensity of the pulse eddy current signal at the farthest focal point that the probe 1 can reach is still not less than the preset intensity when the spatial position of the probe 1 is kept fixed.

[0087] Based on pre-built and stored first and second mapping relationships, when measuring pipes with specified coating thickness, outer diameter, and wall thickness, technicians can pre-input H into the controller.c D o and T w The controller first determines the focusing depth Z during the detection process through the first mapping relationship. f Effective range D f Then for D f The values ​​are discretized to obtain the values ​​of each focusing depth to be measured, which can be denoted as Z. f 0, Z f 1, ..., Z f There are m values ​​in total. Finally, based on the second mapping relationship, the pose of each active joint 14 is determined when performing the detection task corresponding to each focusing depth value, and thus adaptively adjusted.

[0088] Next, the controller also controls the excitation source and signal receiver to output excitation signals and receive induction signals respectively at any focal point, so as to realize the defect distribution near the focal point based on the induction signals. In this process, the position of the focal point can be further adjusted to complete the scanning of the pipeline under test. In this embodiment, the position of the focal point can be adjusted by moving the probe 1 radially or axially along the pipeline, or by adjusting the orientation of each excitation coil 12 and detection coil 13. The former is mainly for scanning defects in different areas of the pipeline wall at the same focal depth, while the latter is mainly used to adjust the focal depth to scan defects at different depths in the pipe wall. By combining the two adjustment strategies, "directional" detection of defects at any position in the pipeline wall can be achieved.

[0089] In this embodiment, the focusing depth can be adjusted automatically by the controller through the movable joint 14; while the movement (including translation and radial rotation) of the probe 1 along the pipe wall can be manually performed by the operator. In a further optimized embodiment, the provided zoom-type pipe non-destructive testing instrument may also include a carrier for carrying the probe 1. This carrier can be a pipe-climbing robot with autonomous walking capabilities. This embodiment does not limit the structure of the pipe-climbing robot, as long as it has the ability to move along the pipe extension direction and rotate radially along the pipe. In this case, by electrically connecting the carrier to the controller, motion control commands can be issued to the carrier through the controller to manipulate the carrier to move along the surface of the object being tested, thereby achieving scanning of the object being tested; that is, achieving full automation of the detection process.

[0090] In the technical solution provided in this embodiment, the more excitation coils 12, the better, provided that they do not interfere with each other's motion or the excitation magnetic field. However, under the condition of achieving basic detection performance, only one detection coil 13 is required at most. For example, in this embodiment, the detection coil 13 can be placed in the middle of each excitation coil 12, so that the number of excitation coils 12 on both sides is the same, thus making the surrounding magnetic field more uniform. In a further optimized solution, the detection coil 13 can also include two sets, which are symmetrically distributed radially along the pipeline where the focal point is located; this can achieve differential detection of defects at the focal point. In differential detection mode, the induced signals collected by the two sets of detection coils 13 are output in differential form; the controller can effectively suppress common-mode interference such as lift-off noise and environmental drift based on the differential signal, amplify the defect feature signal, and improve the signal-to-noise ratio and defect identification accuracy.

[0091] In practical applications, when using the eddy current detection probe 1 with "zoom" function to perform non-destructive testing on magnetically permeable pipes (such as cast iron pipes), the alternating magnetic field generated by the excitation coil 12 tends to remain on the surface of the pipe under test due to the skin effect, failing to penetrate deep into the pipe wall. To address this issue, in a further optimized solution of this embodiment, the probe 1 can also include a bias magnetic field generator 5. The bias magnetic field generator 5 is used to ensure that a specified range around the focal point of the pipe under test is within a bias magnetic field of preset strength. This bias magnetic field is a DC magnetic field, which can significantly reduce the relative permeability of the pipe under test, thereby alleviating the skin effect of the eddy current and allowing the eddy current field to penetrate deeper into the inner wall of the pipe. The specific principle can be explained as follows: In the detection, the eddy current penetration depth can be expressed as... :

[0092] ;

[0093] in, f For the excitation frequency, For electrical conductivity, is the magnetic permeability.

[0094] Because the high permeability of ferromagnetic materials significantly enhances the skin effect, electromagnetic fields are more easily concentrated in the near-surface region. The skin effect affects not only the detection depth but also the uniformity of the response to defects on both the inner and outer walls. For example, Figure 5 As shown, the magnetic properties of ferromagnetic materials are not ideally linear, but rather vary with the magnetic field strength. B The change in magnetic permeability exhibits a significantly nonlinear pattern. With the applied magnetic field HThe changes in permeability typically involve a rapid rise, a peak, a gradual decline, and a stabilization. This means that under pulsed eddy current excitation, the effective magnetic response of a material varies with the operating point, thus affecting the waveform morphology, response amplitude, and defect distinguishability. Especially when no bias magnetization is applied, higher effective permeability not only reduces penetration depth but may also introduce additional magnetic nonlinear perturbations.

[0095] By applying a stable DC bias magnetic field to the detection region, the material's operating point can be pushed into or near the saturation region. At this point, the change in magnetic flux density corresponding to the transient field increment superimposed by the pulse excitation will decrease significantly. When the material enters the near-saturation operating region, the incremental permeability will decrease significantly and tend towards a low and stable level. The skin effect will weaken accordingly, and the effective propagation conditions of the excitation magnetic field along the wall thickness direction will also be improved.

[0096] The bias magnetic field generator 5 in this embodiment can be implemented in various forms. For example, such as Figure 6 As shown, the bias magnetic field generator 5 can use a detachable permanent magnet. Technicians can select the appropriate model of permanent magnet according to the specifications of the pipe to be tested; install it near the pipe or probe 1, and fix the relative position of probe 1 and the permanent magnet, so that the permanent magnet can always magnetize the pipe wall surface of the local area detected by probe 1. In a further optimized scheme, an electromagnet can also be used as the bias magnetic field generator 5. Specifically, as shown... Figure 7 As shown, the bias magnetic field generator 5 in this embodiment includes a U-shaped magnetic yoke and a first coil wound on it. The two ends of a support 11 are fixedly connected to the inside of the U-shaped opening of the magnetic yoke. The curved surface of the support 11 is located on the side away from the magnetic yoke. The first coil is electrically connected to an excitation source, which outputs a DC signal required to generate the bias magnetic field to the first coil. Compared to the permanent magnet solution, the electromagnet solution is more flexible and allows the bias magnetic field to be removed by directly cutting off the DC signal to the first coil after detection. Alternatively, the current output to the first coil can be increased as needed to enhance the magnetic field strength of the generated bias magnetic field.

[0097] Example 2

[0098] The variable-focus pipe non-destructive testing instrument in Example 1 is designed based on the variable-focus eddy current detection probe 1 first proposed by the technicians of this example. The variable-focus eddy current detection probe 1 is essentially a novel eddy current detection probe 1 that includes multiple excitation coils 12 and at least one detection coil 13; and the orientation and / or spatial position of each excitation coil 12 and detection coil 13 can be flexibly adjusted; and in any orientation adjustment state, the orientation of each coil can always point to the same focal point.

[0099] In practical applications, this novel eddy current testing probe 1 can not only be used to measure different types of coated pipes, but also extended to the testing of any non-pipeline metal wall surface. It can be used for non-destructive testing of metal walls of any shape, especially various coated metal walls, such as metal containers of different shapes, curved or flat metal plates, etc.

[0100] Based on this, this embodiment further provides a flaw detection method for coated metal walls. The zoom-type pipeline non-destructive testing instrument provided in Embodiment 1 essentially employs this flaw detection method for coated metal walls to perform non-destructive testing on coated pipelines during actual operation. Specifically, the flaw detection method for coated metal walls provided in this embodiment includes the following process:

[0101] Several excitation coils 12 and at least one detection coil 13 are set outside the object under test at different positions and orientations.

[0102] The orientations of each excitation coil 12 and detection coil 13 are jointly adjusted so that their respective axes of rotational symmetry intersect at any depth between the inner and outer walls of the metal surface to be tested; this intersection point is denoted as the focal point. A synchronous excitation source is sent to each excitation coil 12 to generate a pulsed eddy current signal of target intensity at the focal point; and the induced magnetic field generated by the pulsed eddy current signal at the focal point is received by the detection coil 13, thereby enabling the inversion of the defect distribution around the focal point based on the induced signal.

[0103] Based on this, this embodiment adjusts the orientation of each excitation coil 12 and detection coil 13 in combination, and / or adjusts the position of the combination of excitation coil 12 and detection coil 13 to change the position of the focal point, so that the focal point traverses the target area to be measured in the metal wall to achieve scanning, and visualizes the defect distribution in the target area in the metal wall according to the scanning results.

[0104] Furthermore, as described in Example 1, if the metal wall of the object to be tested has magnetic permeability, in order to improve the detection accuracy, a DC bias magnetic field covering the focal point and its visible range can be generated simultaneously during the scanning process to overcome the skin effect of the magnetic permeable material.

[0105] In practical applications of this embodiment, the scanning method for any target area on any metal wall surface to be tested (including the coated pipe in Embodiment 1) includes the following two scanning modes:

[0106] In the first scanning mode, this embodiment divides the target area into several target layers according to a preset depth; a dot matrix with preset intervals is generated on each target layer in combination with the visible range, and the spatial position of each point in the dot matrix is ​​determined. The maximum range of defect distribution (i.e., the visible range) that can be inferred from the induction signal at any focal point; the distance between adjacent points in the dot matrix is ​​less than the radius of the visible range. Then, by jointly adjusting the orientation of each excitation coil 12 and detection coil 13, the focal point sequentially traverses each point in each target layer to complete the scanning of the target area.

[0107] In another scanning mode, this embodiment can further divide the target area into several target layers according to a preset depth; generate a dot matrix with preset intervals on each target layer based on the visible range, and determine the spatial position of each point in the dot matrix; then, jointly adjust the orientation of each excitation coil 12 and detection coil 13 so that the depth of the focal point corresponds to the depth of one of the target layers; then, move the position of the combination of excitation coil 12 and detection coil 13 outside the metal wall so that the focal point sequentially traverses all points in the target layer at the current depth, completing the scan of the current target layer; then, jointly adjust the orientation of each excitation coil 12 and detection coil 13 so that the focal point is located at the depth corresponding to the next target layer, and repeat the aforementioned scanning strategy until the scanning task of all target layers is completed. As can be seen from the above, the scanning method of this embodiment essentially transforms the flaw detection task in continuous space into a detection task that traverses multiple discretely distributed points in space, based on the visible range of the probe 1 when performing flaw detection at each point. This ensures that the total visible range when detecting each point can completely cover the entire target area to be tested.

[0108] In practical applications, to more intuitively display the flaw detection results, this embodiment can also visualize the flaw detection results of the target area of ​​the object under test. For example, in Embodiment 1, a display can be connected to the controller to display a visualized image or video of the flaw detection results. In this embodiment, the method for visualizing the defect distribution within the target area of ​​a metal wall includes the following process:

[0109] First, the defect distribution information at the focal point is retrieved based on the amplitude change of the induced signal, and / or the phase shift angle, and / or the signal rise time. Then, a planar image representing the layer-by-layer defect distribution of the target area of ​​the metal wall at the corresponding depth is synthesized based on the defect distribution retrieved at each point in any target layer. Alternatively, a three-dimensional image representing the defect distribution within the target area of ​​the metal wall is synthesized based on the defect distribution retrieved at each point in all target layers.

[0110] Simulation test

[0111] To verify the feasibility of the zoom-type pipe non-destructive testing instrument and its corresponding flaw detection method for coated metal walls provided by this invention, technicians conducted simulation tests on the process of detecting defects on the outer and inner walls of pipes using the zoom-type pipe non-destructive testing instrument. The signal strength of the induced signal collected by the detection coil and the corresponding cloud field diagrams of the detection results were compared when the focal point was at different depths of the pipe under test. The experimental process is as follows:

[0112] I. External Wall Defect Detection

[0113] First, in the task of detecting defects on the outer wall, this experiment uses the following methods respectively: Figure 8 and Figure 9 Using two test scenarios—one where the focal point is at the center of the pipe and the other where the focal point is on the pipe wall—as examples, we simulate the detection of defects on the outer wall. Figure 8 The waveform and cloud field diagram of the induced signal obtained when the focal point is at the center of the pipe are shown below. Figure 10 and Figure 11 As shown. In Figure 9 The waveform and cloud field diagram of the induced signal obtained when the focal point is at the center of the pipe are shown below. Figure 12 and Figure 13 As shown.

[0114] In scenarios where the defect is located on the outer wall of a pipe with a cladding layer, an array pulsed eddy current sensor with three excitation probes is used for detection. When the focal point of the three excitation probes is located at the center of the pipe cross-section, the peak detection signal is only 2.4266 × 10⁻⁶. -4 The output response was weak at V; however, when the focusing points of the three excitation probes were adjusted to the location of the defect on the outer wall of the pipe, the peak detection signal increased to 0.6914 V, and the signal response was significantly enhanced. This result indicates that when the focusing position of the excitation probe matches the location of the defect on the outer wall, the sensor can effectively concentrate the excitation energy on the target area, thereby significantly improving the detection effect of the outer wall defect.

[0115] II. Internal Wall Defect Detection

[0116] Next, in the task of detecting defects on the inner wall, this experiment will use the following methods respectively: Figure 14 and Figure 15 Using two test scenarios—one where the focal point is at the center of the pipe and the other where the focal point is on the inside of the pipe wall—as examples, we simulate the detection of defects on the outer wall. Figure 14 The waveform and cloud field diagram of the induced signal obtained when the focal point is at the center of the pipe are shown below. Figure 16 and Figure 17 As shown. In Figure 15 The waveform and cloud field diagram of the induced signal obtained when the focal point is at the center of the pipe are shown below. Figure 18 and Figure 19 As shown.

[0117] Analysis of the above data shows that, under the condition that the defect is located on the inner wall of the pipe with a cladding layer, the same array pulsed eddy current sensor with three excitation probes is used for detection. When the focal point of the three excitation probes is located at the center of the pipe cross-section, the peak detection signal is only 5.1567 × 10⁻⁶. -5 At V, the defect response was not obvious; however, when the focusing points of the three excitation probes were adjusted to the defect location on the inner wall of the pipe, the peak detection signal increased to 0.2334 V, resulting in a clear and significantly enhanced defect response signal. This result demonstrates that even for defects on the inner wall of pipes with cladding layers, by appropriately controlling the focusing positions of the three excitation probes, the electromagnetic response at the defect location can still be effectively enhanced, improving the detectability of the inner wall defects.

[0118] The results of the two sets of simulation experiments show that the focusing position has a significant impact on the detection results when detecting defects in pipes with cladding layers. When the focusing points of the three excitation probes are deviated from the defect location, the detection signal is weak; when the focusing point is aligned with the defect location, the detection signal is significantly enhanced regardless of whether the defect is located on the outer or inner wall of the pipe. Therefore, the variable-focus pipe non-destructive testing instrument provided by this invention, through the collaborative focusing of multiple excitation coils, can effectively improve the electromagnetic field strength in the defect area, enhance the defect response signal, and improve the detection sensitivity and capability for defects on the outer and inner walls of pipes with cladding layers. This experiment verifies the effectiveness and applicability of the non-destructive testing instrument structure and focusing detection method.

[0119] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A variable-focus pipe non-destructive testing instrument, characterized in that, It includes: The probe includes a support, the inner side of which has a curved surface that conforms to the shape of the pipe to be measured; Multiple excitation coils and at least one detection coil are spaced apart on the outer side of the support; each excitation coil and detection coil is connected to the support via an independent movable joint; the movable joint is used to adjust the orientation of the excitation coil or detection coil. An excitation source, which is electrically connected to each excitation coil and is used to output excitation signals to them; A signal receiver, which is electrically connected to the detection coil and is used to acquire the induced signal from the detection coil; The controller is electrically connected to the movable joints, excitation source, and signal receiver. It is used to adaptively adjust the posture of each movable joint according to the coating thickness, outer diameter, and wall thickness of the pipe under test, so that the rotational symmetry axes of each excitation coil and detection coil intersect at any specified position on the wall of the pipe under test, denoted as the focal point. The controller controls the excitation source to output an excitation signal to any focal point to enhance the induction signal at the corresponding position in the signal receiver, thereby retrieving the defect distribution near the focal point. The controller adjusts the position of the focal point to complete the scanning of the pipe under test.

2. The variable-focus pipeline non-destructive testing instrument as described in claim 1, characterized in that: The support is semi-circular, and each excitation coil is evenly distributed along the outer periphery of the support. The movable joint is used to control the orientation of each excitation coil or detection coil to rotate in a space parallel to the plane of the semi-circular support.

3. The variable-focus pipeline non-destructive testing instrument as described in claim 2, characterized in that: The back of the bracket includes a semi-annular groove; in the two side walls of the groove, a set of through holes with opposite positions are provided at the installation positions of each excitation coil or detection coil. The movable joint includes an adjusting rod and a drive motor. The adjusting rod includes a horizontal bar and a vertical bar connected in a T-shape or cross shape. The two ends of the horizontal bar are rotatably connected to the bracket through through holes, so that the vertical bar can rotate about the horizontal bar as an axis in a plane parallel to the bracket. The excitation coil or detection coil is sleeved on the vertical bar. The drive motor is used to drive the horizontal bar to rotate.

4. The variable-focus pipeline non-destructive testing instrument as described in claim 3, characterized in that: The output shaft of the drive motor is connected to the crossbar key of the adjusting rod to realize shaft transmission; Alternatively, the crossbar may be provided with gears whose teeth are arranged circumferentially, and the drive motor and the adjusting rod may be connected by gear transmission.

5. The variable-focus pipeline non-destructive testing instrument as described in claim 1, characterized in that: The probe includes a bias magnetic field generator, which is used to make a specified range around the focal point of the pipe under test in a bias magnetic field of preset intensity. Alternatively, the probe may include a bias magnetic field generator that employs a detachable permanent magnet. Alternatively, the probe includes a bias magnetic field generator, which includes a U-shaped magnetic yoke and a first coil wound on it; the two ends of the bracket are fixedly connected to the inside of the U-shaped opening of the magnetic yoke, and the curved surface of the bracket is located on the side away from the magnetic yoke; the first coil is electrically connected to the excitation source, which is used to output a DC signal to the first coil for generating a bias magnetic field. And / or, the detection coil includes two sets and is symmetrically distributed radially along the pipe where the focal point is located, so as to achieve differential detection of defects at the focal point.

6. The variable-focus pipeline non-destructive testing instrument as described in claim 5, characterized in that: It also includes a carrier for carrying the probe; the carrier is electrically connected to the controller, which controls the carrier to move along the surface of the object being measured, thereby enabling scanning of the object being measured.

7. The variable-focus pipeline non-destructive testing instrument as described in claim 1, characterized in that: The controller pre-stores a first mapping relationship F1 and a second mapping relationship F2 obtained through experimental calibration or numerical simulation. The first mapping relationship F1 is used to characterize any coating layer thickness H c Pipe outer diameter D o and pipe wall thickness T w Corresponding focus depth Z f Effective range D f : D f = F1(H c ,D o ,T w ); The second mapping relationship F2 is used to characterize each active joint in any posture A1~A n The corresponding focus depth Z f : Z f = F2(A1~A n (); In the above formula, n represents the number of movable joints; The controller uses the first and second mapping relationships to adaptively adjust the posture of each movable joint based on the coating thickness, outer diameter, and wall thickness of the pipe under test.

8. A method for flaw detection of a coated metal wall, characterized in that, The zoom-type pipeline non-destructive testing instrument as described in any one of claims 1-7 uses the aforementioned flaw detection method for coated metal walls to perform non-destructive testing on coated pipelines; The flaw detection method includes: Several excitation coils at different positions and orientations and at least one detection coil are set outside the object being tested; The orientation of each excitation coil and detection coil is adjusted so that their respective axes of rotational symmetry intersect at any depth between the inner and outer walls of the metal surface to be tested, and the intersection point is recorded as the focal point. A synchronous excitation source is sent to each excitation coil to generate a pulsed eddy current signal of the target intensity at the focal point. The detection coil receives the induced magnetic field generated by the pulsed eddy current signal at the focal point to realize the defect distribution around the focal point based on the induced signal. By jointly adjusting the orientation of each excitation coil and detection coil, and / or adjusting the position of the combination of excitation coil and detection coil to change the position of the focal point, the focal point traverses the target area to be measured within the metal wall to achieve scanning, and the defect distribution within the target area in the metal wall is visualized based on the scanning results.

9. The flaw detection method for a coated metal wall according to claim 8, characterized in that: If the metal wall surface is magnetic, a DC bias magnetic field covering the focal point and its visible range is generated simultaneously during the scanning process to overcome the skin effect of the magnetic field of the magnetic material. And / or, the scanning method for the target area in the metal wall to be measured includes: The target area is divided into several target layers according to a preset depth; A dot matrix with a preset interval is generated on each target layer based on the visible range, and the spatial position of each point in the dot matrix is ​​determined; then, the orientation of each excitation coil and detection coil is jointly adjusted so that the focal point traverses each point in each target layer in sequence to complete the scanning of the target area. Alternatively, the target area can be divided into several target layers according to a preset depth; a dot matrix with a preset interval can be generated on each target layer in combination with the visible range, and the spatial position of each point in the dot matrix can be determined; then, the orientation of each excitation coil and detection coil can be jointly adjusted so that the depth of the focal point corresponds to the depth of one of the target layers; then, the position of the combination of excitation coil and detection coil can be moved outside the metal wall so that the focal point traverses all points in the target layer at the current depth in sequence, completing the scanning of the current target layer; then, the orientation of each excitation coil and detection coil can be jointly adjusted so that the focal point is located at the depth corresponding to the next target layer, and the aforementioned scanning strategy can be repeated until the scanning task of all target layers is completed.

10. The flaw detection method for a coated metal wall according to claim 9, characterized in that: The maximum range of defect distribution that can be inferred from the induced signal at any focal point is the visible range; the distance between adjacent points in the dot matrix is ​​less than the radius of the visible range; And / or, by adjusting the number of activated excitation coils and the power of the excitation source, the intensity of the pulsed eddy current signal at the furthest focal point is still not less than the preset intensity. And / or, methods for visualizing the distribution of defects within a target area on a metal wall include: The defect distribution information at the focal point can be retrieved based on the amplitude change of the induced signal, and / or the phase shift angle, and / or the signal rise time. A planar image representing the layer-by-layer defect distribution of the target area of ​​the metal wall at the corresponding depth is synthesized based on the defect distribution inverted at each point in any target layer; or, a three-dimensional image representing the defect distribution within the target area of ​​the metal wall is synthesized based on the defect distribution inverted at each point in all target layers.

Images