Magnetic structure, probe, non-destructive testing device and non-destructive testing method

Abstract

The application belongs to the field of nondestructive testing, and relates to a magnetic concentration structure, a detector, a nondestructive testing device and a nondestructive testing method, comprising two oppositely arranged magnetic conductive discs, the centers of the two magnetic conductive discs are each provided with a through hole for a workpiece to be tested to pass through; at least two conical magnetic concentration protrusions are uniformly arranged on the opposite faces of the two magnetic conductive discs along the central axis of the through hole, and the conical magnetic concentration protrusions on the two magnetic conductive discs are arranged in one-to-one correspondence; the tips of the conical magnetic concentration protrusions are oppositely arranged, and a space for mounting a quantum magnetic sensor is left between the tips of the two opposite conical magnetic concentration protrusions. Through the design of the magnetic concentration structure, the performance of the magnetic flux leakage method for nondestructive testing is improved; the magnetic concentration structure adopts two oppositely arranged magnetic conductive discs and uniformly distributed conical magnetic concentration protrusions, can efficiently collect and homogenize the magnetic flux leakage field generated by the defects of the workpiece, guide the magnetic flux leakage field to the quantum magnetic sensor, and realize a magnetic field amplification multiple of 3-5 times.

Description

Technical Field

[0001] This invention belongs to the field of non-destructive testing, and relates to a magnetic focusing structure, a detector, a non-destructive testing device, and a non-destructive testing method. Background Technology

[0002] In the field of industrial non-destructive testing (NDT), the accurate detection of minute cracks and other defects within metallic materials is crucial. However, traditional NDT methods often face challenges in terms of sensitivity and resolution when addressing this need. For example, when inspecting metal components in aerospace and nuclear power equipment where safety requirements are extremely high, failure to detect minute cracks in a timely manner could lead to serious accidents, and traditional methods struggle to ensure comprehensiveness and accuracy. Simultaneously, research into the microscopic magnetic properties of materials also faces technological bottlenecks. Currently, there is an urgent need for a magnetic detection technology that can operate stably under normal conditions and possesses high precision to deeply explore the microscopic magnetic properties of materials, providing strong support for material performance optimization and the development of new materials.

[0003] Nitrogen-vacancy (NV) centers in diamond, as a unique quantum sensor, offer new hope for solving the aforementioned challenges. NV centers possess atomic-level dimensions, meaning they can penetrate deep into materials, acquiring information inaccessible to traditional sensors. More importantly, they exhibit extremely high sensitivity to weak magnetic fields, making them highly promising for detecting the weak leakage magnetic fields generated by minute defects within metallic materials. Although early NV center fabrication processes were complex and applications faced numerous limitations, significant progress has been made in recent years with the rapid development of quantum technology, and NV centers are gradually moving from the laboratory to industrial applications. Utilizing NV centers for magnetic flux leakage nondestructive testing has core advantages. First, it possesses unparalleled detection performance. Over a wide measurement range, NV centers are extremely sensitive to changes in magnetic fields, accurately detecting extremely weak leakage magnetic fields and precisely locating minute defects. Compared to traditional magnetic sensors, its detection accuracy and reliability are significantly improved, providing a more reliable technical means for nondestructive testing. Second, it exhibits excellent environmental adaptability. Its ability to operate stably in various complex industrial scenarios, unaffected by excessive environmental interference, greatly expands its application scope. This sensor, combining the advantages of quantum technology, undoubtedly brings a groundbreaking tool to the field of nondestructive testing, with enormous potential to improve equipment safety and extend equipment lifespan.

[0004] like Figure 1As shown, in magnetic flux leakage detection, the lift-off value refers to the distance between the sensing element and the workpiece. Since the magnetic field signal attenuates sharply as the lift-off value increases, the sensor probe typically needs to be in close contact with the workpiece. However, uneven workpiece surfaces can cause a series of problems: firstly, it can lead to sensor probe wear, increasing equipment maintenance costs; secondly, probe vibration caused by surface unevenness can affect the detection results. Furthermore, in NV color center quantum nondestructive testing, this unevenness can also induce noisy magnetic fields that deviate from the lattice axis, resulting in signal distortion or decreased sensitivity, thus affecting the accuracy of the detection. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a magnetic focusing structure, detector, non-destructive testing equipment and non-destructive testing method to improve the magnetic signal intensity and ensure the direction of the magnetic field to be measured under large lift-off values, thereby giving full play to the advantages of NV color centers in high sensitivity across the entire range.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A magnetic focusing structure includes two magnetically conductive disks arranged opposite each other, each of the two magnetically conductive disks having a through hole at its center for the workpiece to be tested to pass through; at least two tapered magnetic focusing protrusions are evenly distributed along the central axis of the through hole on the opposite surfaces of the two magnetically conductive disks, and the tapered magnetic focusing protrusions on the two magnetically conductive disks are arranged in a one-to-one correspondence. The tips of the conical magnetic protrusions are positioned opposite each other, and a space is left between the tips of the two opposing conical magnetic protrusions for mounting a quantum magnetic sensor.

[0007] Furthermore, the number of the conical magnetic protrusions is four, and they are symmetrically distributed along the central axis of the through hole.

[0008] Furthermore, the magnetic disk and the tapered magnetic protrusion are made of a high magnetic permeability material.

[0009] Furthermore, the magnetic focusing structure is a detachable structure, including splicing components that are equally divided along the number of the conical magnetic focusing protrusions or split in half along the axial direction of the conical magnetic focusing protrusions.

[0010] On the other hand, the present invention also provides a detector, including the aforementioned magnetic focusing structure, magnetization device, and displacement system; the magnetization device includes a magnetic yoke and a magnetizing magnet for magnetizing the workpiece to be tested; the magnetic focusing structure and the quantum magnetic sensor are disposed inside the magnetization device, and the quantum magnetic sensor is installed in the magnetic focusing structure to form a magnetic focusing detection device; The magnetizing device has an opening that matches the through hole, and the through hole in the magnetic focusing structure is connected to the displacement system, so that the workpiece to be tested can move in the magnetic focusing structure through the displacement system.

[0011] Furthermore, it also includes a shielding device that surrounds the magnetic focusing structure and has an opening that matches the through hole to isolate the background magnetic field interference generated by the magnetizing device, while allowing the quantum magnetic sensor to detect the directional leakage magnetic field generated by the surface defects of the workpiece under test.

[0012] Furthermore, the quantum magnetic sensor is a diamond sensor with nitrogen-vacancy color centers, and the crystal axis direction of the NV color centers is aligned with the leakage magnetic field direction between the tips of the conical magnetic protrusions to minimize noise magnetic field interference and maximize sensitivity.

[0013] Furthermore, the displacement system includes a mechanism that drives the workpiece under test to move continuously along the axial direction of the through hole, and synchronously records the position signal and magnetic field signal of the workpiece under test at the quantum magnetic sensor to achieve precise positioning of defects.

[0014] On the other hand, the present invention also provides a non-destructive testing device, including the aforementioned detector, for detecting minute cracks and defects inside metallic materials by means of magnetic flux leakage.

[0015] On the other hand, the present invention also provides a non-destructive testing method, which uses the aforementioned detector and includes the following steps: (1) The workpiece to be tested is placed in a magnetizing device for magnetization to generate an initial magnetic flux; (2) The workpiece to be tested is driven to move along the through hole axially through the displacement system and pass through the magnetic concentrating structure; (3) Between the conical magnetic protrusions of the magnetic focusing structure, a quantum magnetic sensor is used to detect the leakage magnetic field generated by the defect in the workpiece under test. (4) Simultaneously record the position signal of the workpiece under test and the leakage magnetic field signal, and identify and locate the micro-crack defects inside the workpiece under test based on the changes in the intensity and direction of the leakage magnetic field.

[0016] The beneficial effects of this invention are as follows: 1. The technical solution of this invention significantly improves the performance of magnetic flux leakage nondestructive testing through an innovative magnetic focusing structure design. The magnetic focusing structure employs two opposing magnetic disks and uniformly distributed conical magnetic protrusions, which efficiently collect and homogenize the magnetic flux leakage generated by workpiece defects, guiding it to a quantum magnetic sensor (such as an NV color center diamond probe), achieving a magnetic field amplification of 3-5 times. This not only fully utilizes the high sensitivity of the NV color center across the entire measurement range, far superior to traditional magnetic sensors, but also ensures the uniform distribution and directional consistency of the magnetic field at the sensor, thereby accurately locating minute cracks and defects, improving detection accuracy and reliability.

[0017] 2. Addressing the challenges of industrial environments, this solution achieves stable detection at large lift-off values ​​(5-10 mm), avoiding wear caused by the sensor probe being in close contact with the workpiece surface and vibration noise caused by surface unevenness. Simultaneously, the symmetrical arrangement of the conical protrusions and the crystal axis alignment design strictly control the magnetic field direction, suppressing noise interference from deviations from the crystal lattice axis. A shielding device further isolates the background magnetic field of the magnetizing device, ensuring signal purity. This enables the system to maintain high environmental adaptability during high-speed displacement, making it suitable for rough-surface workpieces and significantly reducing the false positive rate.

[0018] 3. Overall, this invention represents a quantum technology breakthrough in the field of non-destructive testing, not only extending equipment lifespan and improving safety, but also expanding application scenarios, such as continuous inspection on production lines. Compared to traditional unidirectional magnetizers, it offers superior magnetic field uniformity and directional consistency, demonstrating significant overall potential and contributing to the advancement of intelligent transformation.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the lift-off value in the background art; Figure 2 This is a schematic diagram of the magnetic field detection device in the embodiment; Figure 3 This is a schematic diagram of the disk layout in the embodiment; Figure 4 This is a schematic diagram of the detector structure in the embodiment; Figure 5 This is a cross-sectional schematic diagram of the detector in the embodiment.

[0021] Reference numerals: 1. Conductor disk; 101. Through hole; 2. Conical magnetic protrusion; 3. Quantum magnetic sensor; 4. Magnetic yoke; 5. Magnetized magnet. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0024] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0025] The magnetic focusing structure, detector, non-destructive testing equipment, and non-destructive testing method of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the embodiments described below are only for explaining the present invention and are not intended to limit the invention.

[0026] This embodiment provides a magnetic flux leakage non-destructive testing system based on a nitrogen-vacancy (NV) color center quantum sensor. This system is suitable for detecting defects such as micro-cracks inside metal workpieces, including surface and internal damage to steel pipes or mechanical parts. The entire system design emphasizes magnetic field uniformity and directional consistency at large lift-off values ​​to avoid wear and noise interference to the sensor caused by uneven workpiece surfaces. Specifically, the lift-off value is defined as the distance between the quantum magnetic sensor and the surface of the workpiece being tested. In this embodiment, a stable lift-off value of 5-10 mm can be achieved, far exceeding the 1-2 mm limitation of traditional magnetic sensors, thereby improving the safety and applicability of the detection.

[0027] like Figure 2 and Figure 3As shown, the magnetic detection device of this embodiment includes two opposing magnetic disks 1. Each magnetic disk 1 has a disk-shaped structure and is made of a high-permeability material, such as permalloy, to ensure a low magnetic resistance path. A through-hole 101 is provided at the center of each magnetic disk 1 for the workpiece to be tested (whose diameter is smaller than the inner diameter of the through-hole 101) to pass through and move. The two magnetic disks 1 are fixed at intervals by a non-magnetic support frame (e.g., an aluminum alloy bracket) to accommodate the quantum magnetic sensor 3.

[0028] On the opposing surfaces of the two conductive disks 1, four conical magnetic focusing protrusions 2 are evenly distributed along the central axis of the through hole 101. These conical magnetic focusing protrusions 2 are arranged symmetrically, with an included angle of 90° between every two adjacent protrusions to achieve uniform collection of the magnetic field. The bottom diameter of each conical magnetic focusing protrusion 2 is larger than the front diameter. This conical design with a larger bottom and a smaller front can concentrate and amplify the leakage magnetic field generated by workpiece defects, with an amplification factor of 3-5 times. The conical magnetic focusing protrusions 2 are also made of permalloy and are integrally formed with the conductive disks 1 or fixed by welding. The conical magnetic focusing protrusions 2 on the upper and lower conductive disks 1 correspond one-to-one, that is, the four protrusions of the upper conductive disk 1 are axially aligned with the four protrusions of the lower conductive disk 1, and the distance between their tips is used to install the quantum magnetic sensor 3.

[0029] When the workpiece under test passes through the through hole 101, the leakage magnetic field generated by its surface defects (such as cracks less than 1 mm in length) is collected by the magnetic disk 1 and guided to the tip region through the tapered magnetic focusing protrusion 2. A quantum magnetic sensor 3 is installed between the tips. This quantum magnetic sensor is a diamond block with NV color centers. The crystal axis direction of the NV color centers (e.g., a four-axis configuration of the (100) plane) is aligned with the magnetic field direction between the tips of the tapered magnetic focusing protrusion 2, ensuring that the projection of the magnetic field in the Z direction relative to the NV color center axis is consistent, thereby minimizing noise deviating from the lattice axis. This configuration makes the leakage magnetic field uniformly distributed at the probe (uniformity error less than 5%), with the direction perpendicular to the protrusion surface, improving the sensitivity of the sensor.

[0030] For ease of installation and maintenance, the magnetic focusing structure in this embodiment adopts a detachable design. Specifically, each magnetic disk 1 can be split in half along the axial direction of the conical magnetic focusing protrusion 2 (i.e., cut into two semi-circular parts along the diameter line) and fixed by bolts or clips. Alternatively, it can be divided equally according to the number of the four conical magnetic focusing protrusions 2 (i.e., divided into four fan-shaped parts) to accommodate workpieces of different sizes. This modular structure allows for the replacement of the quantum magnetic sensor 3 without disassembling the entire device.

[0031] like Figure 4 and Figure 5As shown, the detector in this embodiment includes the aforementioned magnetic detection device, magnetization device, displacement system, and shielding device. The magnetization device consists of a magnetic yoke 4 and magnetizing magnets 5. The magnetic yoke 4 is an annular iron ring used to close the magnetic circuit. The magnetizing magnets 5 are two annular neodymium iron boron permanent magnets, respectively installed at both ends of the magnetic yoke 4, thus allowing the magnetization device to have an opening that matches the through hole. The workpiece to be tested enters the magnetization device through the opening and connects to the through hole 101, receiving uniform magnetization (magnetization intensity of approximately 1000 Oe) to excite the leakage magnetic field at the defect location.

[0032] The magnetic focusing detection device is located in the middle of the magnetization device; that is, the workpiece to be tested is magnetized in the magnetization device before entering the magnetic focusing zone. The displacement system includes a linear guide rail driven by a stepper motor, used to continuously push the workpiece to be tested along the axial direction of the through hole 101. The displacement system can be equipped with a position encoder for real-time recording of the workpiece position.

[0033] To prevent noise from the vibration of the yoke 4 and the magnetizing magnet 5 during the operation of the magnetization device from interfering with the detection results, a shielding device is installed outside the magnetic focusing detection device. This shielding device is a cylindrical metal cover that surrounds the magnetic focusing structure, but leaves an opening of through-hole 101. The shielding device can attenuate the background magnetic field to the microtesla level without affecting the transmission of the defect leakage magnetic field. The quantum magnetic sensor 3 is located between the tips of the conical magnetic focusing protrusions 2 inside the shielding device, where the magnetic field is strongest and most uniform, for vector detection of the main magnetic flux.

[0034] The non-destructive testing equipment in this embodiment includes the aforementioned detector and is integrated into a portable housing. It is equipped with a data acquisition module and a display interface for real-time output of defect location and severity.

[0035] The non-destructive testing method in this embodiment is as follows: First, the workpiece to be tested (such as a 200mm long steel bar) is placed on the displacement system, and the magnetization device is activated to uniformly magnetize the workpiece. Then, the workpiece is driven to move along the through-hole 101, passing through the magnetic focusing area. Between the tips of the conical magnetic focusing protrusions 2 in the magnetic focusing area, the quantum magnetic sensor 3 continuously detects the leakage magnetic field signal, while the displacement system records the corresponding position. The data processing software identifies defects based on the peak value and direction changes of the leakage magnetic field intensity; for example, the magnetic field gradient at a crack can reach 100 T / mm. The pure signal isolated by the shielding device ensures that the detection sensitivity is not affected by surface unevenness (roughness Ra 6.3), making it suitable for continuous inspection on the production line.

[0036] Through the above embodiments, the present invention achieves high-precision defect detection under large lift-off values, significantly improving the reliability and efficiency of industrial non-destructive testing.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A magnetic focusing structure, characterized in that, It includes two magnetically conductive disks arranged opposite each other, and each of the two magnetically conductive disks has a through hole in the center for the workpiece to be tested to pass through; at least two conical magnetically focusing protrusions are evenly distributed along the central axis of the through hole on the opposite surfaces of the two magnetically conductive disks, and the conical magnetically focusing protrusions on the two magnetically conductive disks are arranged one-to-one. The tips of the conical magnetic focusing protrusions are arranged opposite each other, and a space for installing a quantum magnetic sensor is left between the tips of the two opposite conical magnetic focusing protrusions. The number of the conical magnetic protrusions is four, and they are symmetrically distributed along the central axis of the through hole; The quantum magnetic sensor is a diamond sensor with nitrogen-vacancy color centers. The crystal axis of the nitrogen-vacancy color centers is aligned with the leakage magnetic field direction between the tips of the conical magnetic protrusions to minimize noise magnetic field interference and maximize sensitivity.

2. The magnetic focusing structure according to claim 1, characterized in that, The magnetic disk and the tapered magnetic protrusion are made of a high magnetic permeability material.

3. The magnetic focusing structure according to claim 1, characterized in that, The magnetic focusing structure is a detachable structure, including splicing components that are equally divided along the number of the conical magnetic focusing protrusions or split in half along the axial direction of the conical magnetic focusing protrusions.

4. A detector, characterized in that, Includes the magnetic focusing structure, magnetization device, and displacement system as described in any one of claims 1 to 3; the magnetization device includes a magnetic yoke and a magnetizing magnet for magnetizing the workpiece to be tested; the magnetic focusing structure and the quantum magnetic sensor are disposed inside the magnetization device, and the quantum magnetic sensor is installed in the magnetic focusing structure to form a magnetic focusing detection device; The magnetizing device has an opening that matches the through hole, and the through hole in the magnetic focusing structure is connected to the displacement system, so that the workpiece to be tested can move in the magnetic focusing structure through the displacement system.

5. The detector according to claim 4, characterized in that, It also includes a shielding device that surrounds the magnetic focusing structure and has an opening that matches the through hole to isolate the background magnetic field interference generated by the magnetizing device, while allowing the quantum magnetic sensor to detect the directional leakage magnetic field generated by the surface defects of the workpiece under test.

6. The detector according to claim 4, characterized in that, The displacement system includes a mechanism that drives the workpiece under test to move continuously along the axis of the through hole, and synchronously records the position signal and magnetic field signal of the workpiece under test at the quantum magnetic sensor to achieve precise positioning of defects.

7. A non-destructive testing device, characterized in that, The detector includes the one described in any one of claims 4 to 6, used for detecting minute cracks and defects inside metallic materials by magnetic flux leakage method.

8. A non-destructive testing method, characterized in that, The method of using the detector according to any one of claims 4 to 6 includes the following steps: (1) The workpiece to be tested is placed in a magnetizing device for magnetization to generate an initial magnetic flux; (2) The workpiece to be tested is driven to move along the through hole axially through the displacement system and pass through the magnetic concentrating structure; (3) Between the conical magnetic protrusions of the magnetic focusing structure, a quantum magnetic sensor is used to detect the leakage magnetic field generated by the defect in the workpiece under test. (4) Simultaneously record the position signal of the workpiece under test and the leakage magnetic field signal, and identify and locate the micro-crack defects inside the workpiece under test based on the changes in the intensity and direction of the leakage magnetic field.

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