Defect detection pen type probe based on differential alternating excitation focusing sensing

Abstract

The invention discloses a defect detection pen type probe based on differential alternating excitation focusing sensing. The defect detection pen type probe comprises an excitation coil, a magnet yoke, a TMR magnetic sensor, a power supply and a signal conditioning circuit, an excitation coil is connected with an excitation signal source, a TMR magnetic sensor is connected with a power supply and a signal conditioning circuit, a pen type probe is placed on a detected test piece, an alternating signal generated by a signal generator is applied to the excitation coil after being subjected to power amplification, the excitation coil can generate an alternating magnetic field, the alternating magnetic field forms a loop in a manganese zinc ferrite magnet yoke, and the magnetic field is applied to the detected test piece. When a defect exists on the test piece and an eddy current gathering area passes through the defect, the induced eddy current generates disturbance, a secondary magnetic field is changed, and then a signal of the magnetic sensor is changed. After a magnetic sensor signal passes through the differential amplification circuit, data acquisition is carried out by using the data acquisition module, and finally the data is transmitted to the upper computer for display and storage.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic non-destructive testing. More specifically, it relates to a defect detection pen-type probe based on differential alternating excitation focusing sensing. Background Art

[0002] For the defect detection of key components such as aerospace parts and nuclear reactor pressure vessels, there are currently different types of non-destructive testing methods applied to the detection of different complex environments. Among them, there are detection methods including radiographic testing, ultrasonic testing, magnetic particle testing, eddy current testing, magnetic flux leakage testing, etc. Radiographic testing is generally not suitable for on-site testing and has radiation, with high requirements for operators. Ultrasonic technology requires a coupling agent and is not easy to detect surface corrosion. Magnetic particle testing is mainly for ferromagnetic materials and cannot detect non-ferromagnetic materials. Due to the skin effect, eddy current technology cannot detect external defects. Magnetic flux leakage testing requires the saturation magnetization of the test material, which will have a residual magnetic effect on the specimen, and can only detect ferromagnetic materials. Currently, a relatively popular detection technology, the ACFM (Alternating Current Field Measurement) technology, is an advanced electromagnetic non-destructive testing method, mainly used for the detection of surface and near-surface cracks in metal structures. With its advantages of non-contact, high precision, anti-interference, etc., it shows high efficiency and reliability in industrial non-destructive testing, especially suitable for the rapid evaluation of complex environments and key structures. However, traditional ACFM probes are generally large in size, difficult to meet the detection requirements of metal specimens with complex shapes, and still have insufficient detection sensitivity for micro-sized defects. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art. For the surface and near-surface micro-cracks of metal materials, a defect detection pen-type probe based on differential alternating excitation focusing sensing is provided. After the alternating electromagnetic field is focused by a unique focusing type manganese-zinc ferrite magnetic yoke, the eddy current density in the detection area of the specimen can be greatly increased, so as to achieve the purpose of high-sensitivity detection of micro-defects. Moreover, the size of the detection end of the pen-type probe of the present invention is small, and it can meet the detection requirements of specimens with more complex shapes.

[0004] To achieve the above invention purpose, a defect detection pen-type probe based on differential alternating excitation focusing sensing of the present invention is characterized in that it includes: an excitation coil, a magnetic yoke, a TMR magnetic sensor, a power supply, and a signal conditioning circuit;

[0005] The excitation coil is wound on both sides of the U-shaped magnetic yoke. By controlling the winding method, the magnetic field directions generated by the excitation coils on both sides are opposite, forming a loop in the magnetic yoke;

[0006] The yoke includes two parts, the upper part is a U-shaped yoke, and a wedge-shaped yoke is respectively arranged below the two arms of the U-shaped yoke for focusing magnetic field lines to enhance the local magnetization ability of the probe for the test piece.

[0007] The TMR magnetic sensor is placed at the middle position at the bottom of the two wedge-shaped yokes, and the magnetic sensitive direction is the vertical direction.

[0008] The power supply and signal conditioning circuit includes a power supply module and a differential amplifier circuit for supplying power to the magnetic sensor and differentially amplifying the magnetic sensor signal.

[0009] The invention purpose of the present invention is realized as follows:

[0010] A defect detection pen-type probe based on differential alternating excitation focusing sensing of the present invention includes: an excitation coil, a yoke, a TMR magnetic sensor, and a power supply and signal conditioning circuit; the excitation coil is connected to an excitation signal source, the TMR magnetic sensor is connected to the power supply and signal conditioning circuit, and then the pen-type probe is placed on the test piece to be inspected. The alternating signal generated by the signal generator is applied to the excitation coil after power amplification. The excitation coil will generate an alternating magnetic field, and the alternating magnetic field forms a loop in the manganese-zinc ferrite yoke and generates aggregation at the bottom of the yoke. The aggregated alternating magnetic field will induce aggregated eddy currents on the test piece. When there is a defect on the test piece and the eddy current aggregation area passes through the defect, the induced eddy current will generate a disturbance, causing the secondary magnetic field generated by the eddy current to change, and further causing the signal of the magnetic sensor to change. The signal of the magnetic sensor is differentially amplified by the differential amplifier circuit and then data is collected by the data acquisition module, and finally the data is transmitted to the upper computer for display and storage.

[0011] Meanwhile, a defect detection pen-type probe based on differential alternating excitation focusing sensing of the present invention also has the following beneficial effects:

[0012] (1) After the present invention focuses the alternating electromagnetic field through a unique focusing-type manganese-zinc ferrite yoke, the eddy current density in the test area of the test piece can be greatly increased, so as to achieve the purpose of high-sensitivity detection of micro defects.

[0013] (2) The designed focusing-type manganese-zinc ferrite yoke of the present invention will neither cause the magnetic resistance of the magnetic circuit to be too large due to the too large distance between the two arms of the U-shaped yoke, resulting in a decrease in the magnetic induction intensity on the magnetic circuit, nor cause most of the magnetic field lines to directly propagate from one side of the magnetoferrite to the upper part of the magnetic sensor and then to the other side of the magnetoferrite without passing through the test piece from below, resulting in a small eddy current density.

[0014] (3) The present invention ensures that the background magnetic field in the vertical direction of the magnetic sensor is weak and has high sensitivity to the perturbation of the defect magnetic field by placing a high-sensitivity TMR magnetic sensor with a vertical magnetic sensitivity direction at the middle position of the bottoms of the above two wedge-shaped magnetic yokes.

[0015] (4) The detection end of the pen-type probe of the present invention has a small size and can meet the detection requirements of test pieces with more complex shapes. Description of the Drawings

[0016] Figure 1 is a structural diagram of a pen-type probe for defect detection based on differential alternating excitation focusing sensing according to the present invention;

[0017] Figure 2 is a schematic diagram of the specific position and magnetic sensitivity direction of the TMR magnetic sensor in the pen-type probe;

[0018] Figure 3 is a working schematic diagram of a pen-type probe for defect detection based on differential alternating excitation focusing sensing;

[0019] Figure 4 is a distribution diagram of the induced eddy current density generated by the pen-type probe on the surface and cross-section of the test piece;

[0020] Figure 5 is a detection signal diagram of test pieces with defects buried at different depths and the pen-type probe;

[0021] Figure 6 is a detection signal diagram of a test piece with an artificial groove defect (8×0.2×0.3 mm) and the pen-type probe;

[0022] Figure 7 is a detection signal diagram of a test piece with an artificial groove covered by a defect-free metal plate and the pen-type probe. Detailed Embodiments

[0023] The following describes the detailed embodiments of the present invention with reference to the drawings, so that those skilled in the art can better understand the present invention. It should be particularly 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.

[0024] Embodiment

[0025] In this embodiment, as Figure 1 shown, a structural diagram of a pen-type probe for defect detection based on differential alternating excitation focusing sensing according to the present invention includes: an excitation coil, a magnetic yoke, a TMR magnetic sensor, a power supply, and a signal conditioning circuit.

[0026] The exciting coil is wound around both sides of the U-shaped yoke. The number of turns on both sides is the same. By controlling the winding method of the coil, the magnetic field directions generated by the coils on both sides are opposite, forming a loop within the yoke.

[0027] The yoke includes an upper part and a lower part. The upper part is a U-shaped yoke. A wedge-shaped yoke is respectively arranged below the two arms of the U-shaped yoke to focus the magnetic lines of force and enhance the local magnetization ability of the probe for the test piece.

[0028] In this embodiment, as Figure 1 shown, the yoke is in the shape of a tweezer-like double-arm structure and belongs to a centrosymmetric structure. The cross-sectional size of the upper end of the wedge-shaped yoke is the same as that of the bottom end of the U-shaped yoke, and the two are in close contact and fixed. The cross-sectional area of the bottom end of the wedge-shaped yoke is much smaller than that of the upper end. The materials of the U-shaped yoke and the wedge-shaped yoke are selected as manganese-zinc ferrite.

[0029] In this embodiment, as Figure 2 shown, the highly sensitive TMR magnetic sensor is placed at the middle position at the bottom of the above two wedge-shaped yokes, and the magnetic sensitive direction is the vertical direction. This special position can ensure that the background magnetic field in the sensitive direction of the magnetic sensor is weak, while having a high sensitivity to the disturbance of the defect magnetic field.

[0030] When the pen-type probe works, as Figure 3 shown, the differential exciting coil is connected to the exciting signal source, the magnetic sensor is connected to the power supply and the signal conditioning circuit. The pen-type probe is placed on the test piece. The alternating signal generated by the signal generator is amplified by power and then applied to the exciting coil. The exciting coil will generate an alternating magnetic field. The alternating magnetic field forms a loop within the yoke and gathers at the bottom of the yoke. The gathered alternating magnetic field will induce a gathered eddy current on the test piece. When there is a defect on the test piece and the eddy current gathering area passes through the defect, the induced eddy current will generate a disturbance, causing the secondary magnetic field generated by the eddy current to change, and further causing the signal of the magnetic sensor to change. The signal of the magnetic sensor is amplified by the differential amplifier circuit and then data is collected using the data acquisition module. Finally, the data is transmitted to the host computer for display and storage.

[0031] A specific finite element simulation model is established for the present invention, and the distribution of the induced eddy current density on the surface and cross-section of the test piece is as Figure 4 shown. The gathering effect of the induced eddy current on the surface of the test piece is good, and the induced eddy current density is greatly improved, which can improve the detection ability for micro defects. And the induced eddy current also has a certain penetration depth, which can detect defects within a certain depth range.

[0032] Figure 5It is the detection signal diagram of specimens with defects at different burial depths and the pen-type probe. There is a surface-opening groove defect on the specimen, with dimensions of 50 mm × 3 mm. There are also three buried groove defects with the same dimensions on its right side, and their burial depths are 1 mm, 2 mm, and 3 mm respectively. It can be seen from the signal diagram that the probe can detect the above surface and buried defects well.

[0033] Figure 6 It is the detection signal diagram of the specimen with a shallow and narrow artificial groove defect and the pen-type probe. The size of this defect is 8 mm × 0.2 mm × 0.3 mm. It can be seen from the signal diagram that the probe can detect the above shallow and narrow artificial groove defect well.

[0034] Figure 7 It is the detection signal diagram of the artificial groove specimen covered by a defect-free metal plate and the pen-type probe. This specimen consists of two parts. The first part has an artificial groove defect with dimensions of 9.5 mm × 0.5 mm × 0.5 mm on its surface. The second part is a 1.5-mm-thick defect-free metal plate, which covers the first part to form the whole specimen. The scanning direction of the pen-type probe is perpendicular to the direction of the artificial groove defect. It can be seen from the signal diagram that the probe can also detect the above artificial groove defect covered by a 1.5-mm-thick metal plate well.

[0035] Although the above-described illustrative specific embodiments of the present invention have been described to facilitate those skilled in the art of the present technology 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 of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions created using the concept of the present invention are within the scope of protection.

Claims

1. A defect detection pen-type probe based on differential alternating excitation focusing sensing, characterized in that, It includes: An excitation coil, a magnetic yoke, a TMR magnetic sensor, a power supply and a signal conditioning circuit; The excitation coil is wound on both sides of the U-shaped magnetic yoke. By controlling the winding method, the magnetic field directions generated by the excitation coils on both sides are opposite, forming a loop in the magnetic yoke; The magnetic yoke includes two parts, the upper part is a U-shaped magnetic yoke, and a wedge-shaped magnetic yoke is respectively arranged below the two arms of the U-shaped magnetic yoke to focus the magnetic lines of force and enhance the local magnetization ability of the probe for the test piece; The TMR magnetic sensor is placed at the middle position of the bottom of the two wedge-shaped magnetic yokes, and the magnetic sensitive direction is the vertical direction; The power supply and signal conditioning circuit includes a power supply module and a differential amplifier circuit for supplying power to the magnetic sensor and differentially amplifying the magnetic sensor signal.

2. The pen-type probe for defect detection based on differential alternating excitation focusing sensing according to claim 1, characterized in that, The number of turns of the excitation coils wound on both sides of the U-shaped magnetic yoke is the same.

3. The pen-type probe for defect detection based on differential alternating excitation focusing sensing according to claim 1, wherein The magnetic yoke is in the shape of a tweezer-like double-arm structure and belongs to a centrosymmetric structure.

4. The pen-type probe for defect detection based on differential alternating excitation focusing sensing according to claim 1, characterized in that, The materials of the U-shaped magnetic yoke and the wedge-shaped magnetic yoke are selected as manganese-zinc ferrite.

5. The pen-type probe for defect detection based on differential alternating excitation focusing sensing according to claim 1, wherein, The cross-sectional size of the upper end of the wedge-shaped magnetic yoke is the same as that of the bottom end of the U-shaped magnetic yoke, and the two are in close contact and fixed. The cross-sectional area of the bottom end of the wedge-shaped magnetic yoke is much smaller than that of the upper end cross-section.

6. The pen-type probe for defect detection based on differential alternating excitation focusing sensing according to claim 1, wherein The process of defect detection by the pen-type probe is as follows: The alternating signal generated by the signal generator is amplified in power and then applied to the excitation coil. The excitation coil will generate an alternating magnetic field. The alternating magnetic field forms a loop in the magnetic yoke and gathers at the bottom of the magnetic yoke. The gathered alternating magnetic field will induce a gathered eddy current on the test piece. When there is a defect on the test piece and the eddy current gathering area passes through the defect, the induced eddy current will generate a disturbance, causing the secondary magnetic field generated by the eddy current to change, and further causing the signal of the TMR magnetic sensor to change. The signal of the TMR magnetic sensor is differentially amplified by the differential amplifier circuit and then data is collected by the data acquisition module. Finally, the data is transmitted to the upper computer for display and storage.

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