Non-equilibrium induction high-resolution eddy current detection sensor

Abstract

On the basis of an existing planar PCB exciting coil, five cylindrical copper coils are arranged at equal intervals to form a row of receiving parts, and the receiving parts are located in the center of the distance between two coils of the planar PCB exciting coil. The five copper coil connecting lines are parallel to the width of the planar PCB excitation coil, the central axes of the five copper coils are all perpendicular to the plane of the planar PCB excitation coil, the bottom surfaces of the five copper coils are all located on the plane of the planar PCB excitation coil, the middle copper coil is located in the center of the planar PCB excitation coil, and the middle copper coil is located in the center of the planar PCB excitation coil. Each copper coil is provided with an independent input interface and an independent output interface and is connected with a subsequent signal processing module through the two interfaces, and the inductance values of the two copper coils on the edge are larger than the inductance values of the three copper coils in the middle. The receiving capability of the edge coil is enhanced, so that the five copper coils have consistent output on eddy current disturbance with the same defect under a non-uniform excitation magnetic field, and the resolution ratio of the eddy current detection probe is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of non-destructive testing, and more specifically, relates to a non-equilibrium induction high-resolution eddy current testing sensor. Background Art

[0002] The increasing demand for energy in the new era has accelerated the exploitation of energy such as oil and natural gas, and promoted the rapid development of global pipeline transportation. my country's pipeline transportation network is also expanding rapidly, and the role of pipeline detection is becoming increasingly prominent, especially eddy current detection, which is based on the law of electromagnetic induction and uses induced current to detect changes in the secondary magnetic field to detect defects. It has the advantages of non-contact, fast detection speed, high detection efficiency, and low economic cost. It is easy to realize detection automation and can also play an advantage in the detection of small-diameter pipes.

[0003] The inner wall of the pipeline will produce corrosion defects of varying degrees due to the particularity of the transported materials, and fine cracks due to the load on the pipeline material, etc. These defects will have unpredictable and far-reaching impacts on the performance of the pipeline. Small defects such as cracks and dense pitting defects are difficult to detect due to their small size. Therefore, the resolution requirements for pipeline detection are becoming more and more stringent. To achieve high resolution, a receiving array is required. The smaller the receiving array element, the better the detection capability of tiny defects. However, at the same time, the receiving array element is more susceptible to disturbances from other signals and has low sensitivity. Therefore, the design of high-resolution probes requires a balance between resolution and sensitivity to maximize defect detection efficiency.

[0004] In the Chinese invention patent application published on June 9, 2020 with publication number CN111257410A, a multi-layer PCB differential eddy current detection sensor is disclosed, such as Figure 1As shown, it includes an excitation coil and a receiving coil, and the central axis of the excitation coil and the receiving coil are the same, wherein the excitation coil adopts a single-layer differential structure PCB rectangular coil, and the receiving coil is a multi-layer PCB rectangular coil; when alternating current is passed through the excitation coil, eddy currents are excited on the test piece, and the excited eddy currents generate secondary magnetic fields, which are then received by the receiving coil. When defects appear in the test piece, the eddy current flow direction on the test piece will change, causing the voltage amplitude or phase of the receiving coil to change, thereby detecting the relevant defect information of the test piece. In this invention, the excitation coil adopts a differential rectangular structure, and the differential structure is easy to distinguish the defective part, and the rectangular structure is easier to distinguish defects of different shapes than the circular structure. The receiving coil has a multi-layer structure, which can improve the detection sensitivity on the one hand, and reduce the optimal detection frequency on the other hand, effectively reducing the requirements for the excitation signal. However, it has been gradually discovered through various attempts that the basis for the array eddy current probe to achieve high-resolution detection is that under the excitation of the probe, the initial value of each receiving array element must be the same, so that defects can be detected based on the change. This requires the excitation magnetic field to be uniform, but in reality it is very difficult to design an excitation coil to generate a uniform magnetic field. Summary of the invention

[0005] The purpose of the present invention is to improve the resolution of the eddy current detection probe by using a receiving coil array, and at the same time compensate for the influence of the non-uniform excitation magnetic field on the receiving coil array, and provide a non-balanced induction high-resolution eddy current detection sensor. The principle of eddy current detection is adopted, and different receiving coil parameters are designed so that each receiving coil can have the same initial value under the non-uniform excitation magnetic field, so as to realize subsequent defect identification and imaging.

[0006] To achieve the above-mentioned purpose of the invention, the non-balanced induction high-resolution eddy current detection sensor of the present invention is characterized in that it includes: a planar PCB excitation coil, which is a single-layer planar PCB rectangular differential coil composed of two planar rectangular coils with a length distance of c1 and a differential area in the middle, an input interface input1 of an external excitation signal is provided, which is respectively connected to the input ends of the two planar rectangular coils, and an output interface output1 is respectively connected to the output ends of the two planar rectangular coils, the length of the single-layer planar PCB rectangular differential coil is a1, the width is b1, and the wire diameter of the middle differential area is d 11 The diameter of the remaining wires is d 12 , the line spacing is d 13 , and d 11 >d 12 ;

[0007] It is characterized by further comprising:

[0008] Five copper coils, each copper coil being a cylinder, are tightly wound with enameled copper wire and arranged equidistantly in a column as the receiving part. They are located at the center of the distance between two planar rectangular coils of the planar PCB exciting coil and are parallel to the width of the planar PCB exciting coil, that is, the connection line of the five copper coils is parallel to the width of the planar PCB exciting coil. The central axes of the five copper coils are all perpendicular to the plane of the planar PCB exciting coil, and their bottom surfaces are all located on the plane of the planar PCB exciting coil. The middle copper coil is located at the center of the planar PCB exciting coil;

[0009] The outer diameter of the middle three copper coils is l 11 , and the inner diameter is l 12 , the height is h1, and the wire diameter is d 21 The outer diameter of the two edge copper coils is l 21 , and the inner diameter is l 22 , the height is h2, and the wire diameter is d 22 , where, l 11 , l 21 <c1, and the total length of the entire receiving part is 3l 11 +2l 21 +4c2 ≤ b1, the width is max(l 11 , l 21 ), the height is max(h1, h2). Each copper coil is provided with an independent input interface and an output interface, and is connected to the subsequent signal processing module through the two interfaces. Among them, the inductance of the two edge copper coils is greater than that of the middle three copper coils to enhance the receiving ability of the edge copper coils so that the five copper coils have consistent receiving ability;

[0010] Each copper coil is provided with an independent input interface and an output interface, and is connected to the subsequent signal processing module through the input interface and the output interface;

[0011] Connect the input interface input1 and the output interface output1 of the planar PCB exciting coil to the excitation signal source. At the same time, connect the input and output interfaces of the five copper coils of the receiving part to the signal processing module. Then place the non-equilibrium induction high-resolution eddy current detection sensor on the test piece. The excitation signal source generates a sine signal of a certain frequency and amplifies it, and then drives the planar PCB exciting coil. Since the magnetic flux generated by driving the planar PCB exciting coil changes, according to the theory of Maxwell's equations, eddy currents are formed on the test piece. The flow direction of the eddy currents is a uniform band, and the flow direction of the eddy currents changes at the defect. Because the eddy currents change, the secondary magnetic field generated by the eddy currents changes, and the magnetic flux passing through the five copper coils changes. Furthermore, the amplitude and phase of the five copper coils change, so as to accurately detect the defect information.

[0012] The invention object of the present invention is achieved as follows:

[0013] The non-balanced induction high-resolution eddy current detection sensor of the present invention is based on the existing planar PCB excitation coil. Five cylindrical copper coils are equidistantly arranged as a row of receiving parts, and are located in the center of the distance between the two coils of the planar PCB excitation coil, parallel to the width of the planar PCB excitation coil, that is, the connection line of the five copper coils is parallel to the width of the excitation coil, the central axes of the five copper coils are perpendicular to the plane of the planar PCB excitation coil, the bottom surfaces are all located on the plane of the planar PCB excitation coil, the middle copper coil is located at the center of the planar PCB excitation coil, each copper coil is provided with an independent input interface and an output interface, and is connected to a subsequent signal processing module through the two interfaces, wherein the inductance of the two edge copper coils is greater than the inductance of the three middle copper coils, so as to enhance the receiving ability of the edge coils so that the five copper coils can have consistent output for the same defect eddy current disturbance under the non-uniform excitation magnetic field, thereby improving the resolution of the eddy current detection probe.

[0014] At the same time, the present invention also has the following beneficial effects:

[0015] (1) The present invention is small in size and easy to install on a detection robot. The detection coil and the excitation coil are integrated, which is convenient for detection. The PCB planar coil used has a small size and high sensitivity to surface defects. It has broad prospects in eddy current detection. At the same time, due to the small effective lift-off amount, it is highly sensitive to cracks.

[0016] (2) Direct manufacturing using printed circuit board (PCB) technology makes it easy to permanently fix it to the part to be inspected. In addition, the PCB is flexible enough to allow the coil to be aligned with the surface, so the prospects for inspecting complex surface geometries are also very broad;

[0017] (3) It is easy to print multiple coils on the same board to create a multi-coil array, thereby increasing the inspection range and reducing the inspection time; in addition, the use of rectangular coils makes it easier to splice and combine when tiling into an array, and is less sensitive to edge effects;

[0018] (4) The excitation coil adopts a differential rectangular structure. The differential structure is easy to distinguish the defective part, and the rectangular structure is easier to distinguish defects of different shapes than the circular structure;

[0019] (5) The receiving part is composed of five copper coils arranged in an array. On the one hand, the copper coil has higher detection sensitivity than the PCB planar coil under the same base area. On the other hand, the five independently receiving copper coils can improve the sensor detection resolution and have a higher response to small defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1It is a structural schematic diagram of a specific implementation of the non-equilibrium induction high-resolution eddy current detection sensor of the present invention;

[0021] Figure 2 It is a front view of a specific implementation structure of the excitation coil;

[0022] Figure 3 It is a front view of the structure of a specific implementation of the receiving part;

[0023] Figure 4 It is a working schematic diagram of the non-equilibrium induction high-resolution eddy current detection sensor of the present invention;

[0024] Figure 5 It is a ferromagnetic X80 flat plate with artificial rectangular defects of different sizes;

[0025] Figure 6 It is a detection signal diagram of a ferromagnetic X80 plate 1 using the sensor of the present invention;

[0026] Figure 7 It is a ferromagnetic X80 flat plate with artificial rectangular defects of different sizes;

[0027] Figure 8 This is a detection signal diagram of a ferromagnetic X80 flat plate 2 using the sensor of the present invention. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is described below in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0029] Example

[0030] Figure 1 It is a structural schematic diagram of a specific implementation of the non-balanced induction high-resolution eddy current detection sensor of the present invention.

[0031] In this embodiment, if Figure 1 As shown, the non-equilibrium induction high-resolution eddy current detection sensor of the present invention comprises a planar PCB excitation coil 1 and five copper coils 2, wherein:

[0032] like Figure 2As shown in the figure, the planar PCB excitation coil 1 is a single-layer planar PCB rectangular differential coil composed of two planar rectangular coils 101 and 102 with a lengthwise distance of c1 and a differential region in the middle. The input interface input1 for the external excitation signal is respectively connected to the input ends of the two planar rectangular coils, and the output interface output1 is respectively connected to the output ends of the two planar rectangular coils 101 and 102. The length of the single-layer planar PCB rectangular differential coil is a1, the width is b1, and the wire diameter of the middle differential region is d 11 , and the wire diameter of the remaining wires is d 12 , and the wire spacing is d 13 , and d 11 >d 12 .

[0033] As Figure 1 shown, each of the five copper coils 2 is a cylinder, made of tightly wound enameled copper wire, arranged equidistantly in a column as the receiving part, and located at the center of the distance between the two planar rectangular coils of the planar PCB excitation coil 1, parallel to the width of the planar PCB excitation coil 1, that is, the connection line of the five copper coils is parallel to the width of the planar PCB excitation coil 1. The central axes of the five copper coils are all perpendicular to the plane of the planar PCB excitation coil 1, and the bottom surfaces are all located on the plane of the planar PCB excitation coil 1. The copper wire of the middle 203 turns is located at the center position of the planar PCB excitation coil 1

[0034] In this embodiment, as Figure 3 shown, the outer diameter of the middle three copper coils 202, 203, and 204 is l 11 , the inner diameter is l 12 , the height is h1, and the wire diameter is d 21 , the outer diameter of the two edge copper coils 201 and 205 is l 21 , the inner diameter is l 22 , the height is h2, and the wire diameter is d 22 , where, l 11 ,l 21 <c1, the entire receiving part has a length of 3l 11 +2l 21 +4c2≤b1, the width is max(l 11 ,l 21 ), and the height is max(h1, h2). As Figure 3 shown, each of the copper coils 201 to 205 is provided with independent input and output interfaces, and is connected to the subsequent signal processing module through the two interfaces. Among them, the inductance of the two edge copper coils 201 and 205 is greater than that of the middle three copper coils 202, 203, and 204, so as to enhance the receiving ability of the edge copper coils 201 and 205 and make the five copper coils have consistent receiving ability

[0035] Since the winding direction of the excitation coil at both ends of the excitation coil inevitably changes, the excitation magnetic field at both ends is significantly different from the excitation magnetic field strength in the center of the detection area. In order to achieve high-resolution detection, the present invention increases the inductance of the two edge copper coils to enhance the receiving ability of the edge coils so that the five copper coils have consistent receiving ability, thereby achieving subsequent quantification and imaging. In this embodiment, the number of coil turns of the edge copper coils 201 and 205 is greater than the number of coil turns of the three middle copper coils 202, 203, and 204, so as to increase the inductance of the two edge copper coils.

[0036] like Figure 4 As shown, each copper coil 201-205 is provided with an independent input interface and an output interface, and is connected to a subsequent signal processing module 3 via the input interface and the output interface.

[0037] like Figure 4 As shown, the input interface input1 and the output interface output1 of the planar PCB excitation coil 1 are connected to the excitation signal source (in the signal processing module 3), and the input and output interfaces of the five copper coils of the receiving part are connected to the signal processing module 3. Then, the non-balanced induction high-resolution eddy current detection sensor is placed on the test piece, and the excitation signal source generates a sinusoidal signal of a certain frequency and amplifies it, and then drives the planar PCB excitation coil 1. Since the magnetic flux generated by the planar PCB excitation coil 1 changes, according to the theory of Maxwell's equations, an eddy current is formed on the test piece, and the eddy current flows in a uniform strip shape. The eddy current flows in a direction that changes at the defect. Because the eddy current changes, the secondary magnetic field generated by the eddy current changes, and the magnetic flux passing through the five copper coils 2 changes, and then the amplitude and phase of the five copper coils 2 change, thereby accurately detecting the defect information.

[0038] Figure 5 It is a ferromagnetic #45 steel plate with artificial rectangular defects of different sizes. Figure 6 FIG. 1 is a detection signal diagram of a ferromagnetic #45 steel plate using the sensor of the present invention. In this embodiment, Figure 5 , 6 As shown in the figure, the sensor is used to detect the ferromagnetic #45 steel plate at a lift of 4mm and a moving speed of 40mm / s. The probe size is much larger than the defect size. Figure 6 The detection signal diagram shown in the figure, where the horizontal axis is the number of sampling points and the vertical axis is the output voltage, Figure 6 The output voltage changes of the five copper coils are shown in turn, sharing the same horizontal axis. When the sensor passes through a non-defective position, the detection signal amplitude remains unchanged. When the sensor passes through a defective position, the detection signal amplitude changes. The amplitude and time of the change are related to the size of the defect, and the amplitude changes significantly, indicating that the resolution is high.

[0039] Figure 7 It is a ferromagnetic X80 carbon steel plate with artificial rectangular defects of different sizes. Figure 8 1 is a detection signal diagram of a ferromagnetic X80 carbon steel plate 2 using the sensor of the present invention. Figure 7 , 8 As shown in the figure, the defect of the ferromagnetic X80 carbon steel plate 2 is a small rectangular defect contained in a large rectangular defect. The sensor is used to detect the ferromagnetic X80 carbon steel plate 2 under the conditions of a lift of 4mm and a moving speed of 40mm / s. The probe size is smaller than the large rectangular defect size but larger than the small rectangular defect size. Figure 8 As shown in the detection signal diagram, the horizontal axis is the number of sampling points and the vertical axis is the output voltage; when the sensor passes through a non-defective position, the detection signal amplitude remains unchanged, and when the sensor passes through a defective position, the detection signal amplitude changes. Among them, the five copper coils, namely coils 1 to 5, all send large changes (the amplitude and time are related to the size of the defect), indicating that the resolution is high.

[0040] Although the above describes the illustrative specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A non-equilibrium induction high-resolution eddy current detection sensor, characterized in that: include: The planar PCB excitation coil is a single-layer planar PCB rectangular differential coil composed of two planar rectangular coils with a length distance of c1 and a differential area in the middle. An input interface input1 of an external excitation signal is provided to be connected to the input ends of the two planar rectangular coils respectively, and an output interface output1 is connected to the output ends of the two planar rectangular coils respectively. The length of the single-layer planar PCB rectangular differential coil is a1, the width is b1, and the wire diameter of the differential area in the middle is d 11 The diameter of the remaining wires is d 12 , the line spacing is d 13 , and d 11 >d 12 ; It is characterized by further comprising: Five copper coils, each of which is a cylinder, made of tightly wound enameled copper wire, are equidistantly arranged in a row as the receiving part, and are located in the center of the distance between the two planar rectangular coils of the planar PCB excitation coil, parallel to the width of the planar PCB excitation coil, that is, the connection line of the five copper coils is parallel to the width of the planar PCB excitation coil, the central axes of the five copper coils are all perpendicular to the plane of the planar PCB excitation coil, the bottom surfaces are all located on the plane of the planar PCB excitation coil, and the middle copper coil is located at the center of the planar PCB excitation coil; The outer diameter of the middle three copper coils is l 11 , and the inner diameter is l 12 , the height is h1, and the wire diameter is d 21 , the outer diameter of the two edge copper coils is l 21 , and the inner diameter is l 22 , the height is h2, and the wire diameter is d 22 , where, l 11 , l 21 <c1, and the total length of the entire receiving part is 3l 11 + 2l 21 + 4c2 ≤ b1, the width is max(l 11 , l 21 ), the height is max(h1, h2), each copper coil is provided with an independent input interface and an output interface, and the subsequent signal processing module is connected through the two interfaces. Among them, the inductance of the two edge copper coils is greater than that of the middle three copper coils to enhance the receiving ability of the edge copper coils so that the five copper coils have consistent receiving ability; Each copper coil is provided with an independent input interface and an output interface, and is connected to a subsequent signal processing module through the input interface and the output interface; The input interface input1 and the output interface output1 of the planar PCB excitation coil are connected to the excitation signal source, and the input and output interfaces of the five copper coils of the receiving part are connected to the signal processing module. Then the non-balanced induction high-resolution eddy current detection sensor is placed on the test piece. The excitation signal source generates a sinusoidal signal of a certain frequency and amplifies it, and then drives the planar PCB excitation coil. Since the magnetic flux generated by driving the planar PCB excitation coil changes, according to the theory of Maxwell's equations, eddy currents are formed on the test piece. The eddy current flow direction is uniform and strip-shaped. The eddy current flow direction changes at the defect. Because the eddy current changes, the secondary magnetic field generated by the eddy current changes, and the magnetic flux passing through the five copper coils changes, and then the amplitude and phase of the five copper coils change, so that the defect information can be accurately detected.

2. The non-equilibrium induction high-resolution eddy current detection sensor according to claim 1, characterized in that: The number of turns of the edge copper coil is greater than the number of turns of the three middle copper coils, so as to increase the inductance of the two edge copper coils.

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