Method for testing magnetic properties of a sheet in situ

Abstract

The application discloses a kind of sheet in-situ magnetic property testing method, comprising: adjusting the height and angle of testing device, so that testing device is close to the position of magnetic shielding body to be measured;With excitation coil, auxiliary magnetic yoke is tightly attached to test surface, and vacuum chuck is locked;Start data acquisition program, magnetic field intensity coil and magnetic induction intensity probe are close to the test surface of magnetic shielding body under the action of electric push rod, while the excitation coil on magnetic yoke is electrified;Test graph and test data are obtained on host computer using data transmission software and hardware;After testing, the vacuum chuck lock is opened, and the testing device is removed.The application can realize in-situ measurement of magnetic shielding material, without disassembly, convenient for magnetic shielding performance monitoring and maintenance, and convenient to operate, wide applicability.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic material testing, and in particular to a method for testing the in-situ magnetic properties of thin plates. Background Technology

[0002] Utilizing the high permeability of soft magnetic materials, most DC and low-frequency magnetic fields in the environment can be trapped inside the soft magnetic material through current shunting. Therefore, after constructing a closed magnetic shielding structure using soft magnetic materials, a high-performance near-zero magnetic space can be obtained within the closed structure. The constructed near-zero magnetic space can serve as a fundamental condition for ultra-sensitive measurements, deep space and deep earth exploration, and basic physics research. Thus, soft magnetic materials play an important role in the field of magnetic shielding. The magnetic properties of soft magnetic materials, such as permeability, coercivity, and saturation magnetic induction, directly determine their magnetic shielding performance. Therefore, accurate, rapid, and comprehensive testing and evaluation of the magnetic properties of soft magnetic materials are of great significance.

[0003] In general, the magnetic property testing method for soft magnetic materials often uses a specially made standard test ring. An excitation coil and a test induction coil are uniformly and densely wound on the test ring. The magnetic field strength H and the corresponding magnetic induction intensity B are obtained by electromagnetic induction. By excitation in both directions, the complete hysteresis loop of the material can be obtained, and the magnetic properties of the material can be calculated. The drawbacks of this testing method are: 1) It requires a specially made standard test ring and cannot directly reflect the performance of the thin plate material used in actual installation; 2) Each test requires winding, resulting in low testing efficiency and introducing human stress error. In the current research progress on the magnetic property testing method of soft magnetic materials, Gmyrek et al. used a high-permeability material to make a magnetic yoke, combined with the test sample, to extend it into a closed loop (Gmyrek Z. Single Sheet Tester With Variable Dimensions[J].IEEE Transactions on Instrumentation & Measurement,2016,65(7):1661-1668). Thus, by installing an induction coil on the plate sample used to construct the shield, the magnetic properties of the plate sample can be directly obtained (without the need for a separately made test ring). However, the improved testing method still has some shortcomings: 1) The improved testing method still requires winding a magnetic induction coil, which cannot solve the problems of low testing efficiency and the introduction of human error; 2) It can only test the overall average magnetic properties on the plate, and cannot obtain the magnetic properties of local areas, so it cannot locate defects; 3) It cannot perform in-situ measurements on the shield after installation, that is, it cannot evaluate the magnetic properties of the material after the construction is completed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes an in-situ magnetic property testing method for thin plates. This method enables the measurement of the magnetic properties of the material after the shielding structure is assembled. Furthermore, by applying a two-dimensional magnetic field and changing the direction of the magnetic field excitation, the complete magnetic properties of the thin plate sample can be measured. Additionally, by fine-tuning the test structure, different shielding structures (such as flat plates, curved plates, etc.) can be tested. The testing method mentioned in this invention is simple, easy to operate, and highly applicable.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for testing the in-situ magnetic properties of a thin plate includes the following steps:

[0007] Step (1) Adjust the height and angle of the testing device by moving the base, lifting support frame and rotating support seat so that the testing device is close to the thin plate sample to be tested.

[0008] Step (2) Place the auxiliary magnetic yoke close to the thin plate sample and lock the vacuum suction cup, movable base, lifting support frame, and rotating support base;

[0009] Step (3) Start the data acquisition process, and the measuring component automatically approaches the thin plate sample;

[0010] Step (4) Select the test mode, and apply current to the excitation coil according to the set test mode;

[0011] Step (5) Select the target measurement point according to the test requirements, acquire data through the measurement component, and acquire the test graph and test data on the host computer using data transmission software and hardware;

[0012] Step (6) Repeat steps (1) to (5) according to the test requirements to collect data at different test positions of the thin plate sample;

[0013] Step (7) Complete the test and remove the test device.

[0014] Further, step (1) includes: using a movable base to move the test device to the position to be tested, adjusting the height of the lifting support frame fixedly connected to the movable base and adjusting the angle of the rotating support seat hinged to the lifting support frame to adjust the measurement posture of the test device so that the magnetic yoke is facing and close to the thin plate sample.

[0015] Further, step (2) includes: when the magnetic yoke is close to the thin plate sample, the test device and the thin plate sample are attracted and fixed by a vacuum chuck fixedly connected to the magnetic yoke and the rotating support base, and the movable joints of the movable base, the lifting support frame and the rotating support base are locked to ensure that the relative position of the test device and the thin plate sample remains fixed during the test; after the position of the test device is locked, the magnetic yoke and the thin plate sample form a closed loop.

[0016] Further, in step (3), the data acquisition stream includes: firstly, pushing the measurement component close to the thin plate sample by a non-magnetic electric push rod, one end of the non-magnetic electric push rod being fixedly connected to the rotating support base, and the other end being bolted to the measurement component; after the measurement component reaches the test position under the push of the non-magnetic electric push rod, an excitation current is applied by the excitation coil wound on the magnetic yoke, forming a controllable magnetic flux density in the closed loop formed by the thin plate sample, and by adjusting the current of the excitation coil, magnetic field strength and magnetic induction intensity of different amplitudes are formed in the thin plate sample, thereby obtaining the complete hysteresis characteristics of the thin plate sample.

[0017] Further, in step (4), the test mode includes a DC mode or an AC mode, wherein the DC mode is used to obtain the DC magnetic characteristics of the thin plate sample with an amplitude of less than 200kA, and the AC mode is used to obtain the AC magnetic characteristics of the thin plate sample with a frequency range of 20Hz to 20kHz; the excitation current input is a pulse waveform with different amplitudes, or a waveform that continuously increases or decreases; in the AC mode, different hysteresis characteristics of the thin plate sample are obtained by adjusting the frequency of the excitation current of the excitation coil; the number of turns of the excitation coil is 200 to 300 turns.

[0018] Furthermore, in step (5), the method for selecting target measurement points of the thin plate sample is as follows: the size of the thin plate sample is 400mm×400mm, and the minimum test area of ​​the measurement component is 50mm×50mm. Therefore, the spacing between measurement points on the thin plate sample is more than 50mm. At the same time, considering the uniform magnetic excitation area in the thin plate sample, the test points are selected at a distance of more than 50mm from the edge. Therefore, for a 400mm×400mm thin plate sample, the maximum number of measurement points is 6×6=36.

[0019] Further, the measurement component in step (5) consists of a measurement base, a magnetic induction intensity probe, and a magnetic field intensity coil; the magnetic induction intensity probe and the magnetic field intensity coil are fixedly connected to the measurement base, and under the drive of the non-magnetic electric push rod, they approach the thin plate sample to acquire magnetic signals; under the drive of the non-magnetic electric push rod, the tip of the magnetic induction intensity probe contacts and contracts with the thin plate sample to form an electrical conduction path, thereby obtaining the potential difference between the contact points, and further calculating the magnetic induction intensity between the test points.

[0020] Furthermore, the magnetic field strength coil comprises two layers stacked on top of each other, each layer being wound with two sets of mutually perpendicular first and second coils to obtain the magnetic field strength of the thin plate sample in two perpendicular directions respectively;

[0021] Based on electromagnetic induction, the magnetic field strength H1 of the coil near the thin plate sample is calculated as follows:

[0022]

[0023] Where: μ0—vacuum permeability; N H1 —Magnetic field strength; number of coil turns; S H1 — Cross-sectional area of ​​the magnetic flux density coil perpendicular to the magnetic field strength coil; U1 — Induced electromotive force inside the magnetic field strength coil;

[0024] The magnetic field strength H2 was obtained from testing another layer away from the magnetic field strength coil. Based on the linear relationship of magnetic field strength, the corrected internal magnetic field strength H0 of the thin plate sample is as follows:

[0025]

[0026] Where: H1—magnetic field strength measured by the magnetic field strength coil near the test sample; L1—distance between the magnetic field strength coil near the test sample and the thin plate sample; H2—magnetic field strength measured by the magnetic field strength coil away from the thin plate sample; L2—distance between the magnetic field strength coil away from the thin plate sample and the thin plate sample.

[0027] Furthermore, based on the principle of electromagnetic induction, the formula for calculating magnetic field strength is:

[0028]

[0029] Wherein: S B —The cross-sectional area formed by the magnetic induction intensity probe test position and the sample; U —The induced electromotive force detected by the magnetic induction intensity probe.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This invention tests thin plate samples used in actual installation of shielding bodies, and can directly obtain the magnetic permeability of the shielding layer structure without the need to separately make a standard test ring.

[0032] 2. In this invention, the test is completed by using a test coil / probe to approach / contact the test sample. Therefore, the test sample itself does not need to be wound, which reduces the influence of human factors during the test and improves the convenience and reliability of the test.

[0033] 3. The method of the present invention can achieve in-situ testing of the magnetic shield by adjusting the testing device to adapt to the shape of the shield, so as to evaluate the magnetic properties of a local area of ​​the completed magnetic shield and accurately locate defects.

[0034] 4. The present invention adopts a two-dimensional magnetic performance testing scheme. By adjusting the magnitude of the excitation magnetic field component and changing the direction of the excitation magnetic field, the anisotropic magnetic characteristic data of the test sample can be obtained, and the loss parameters under the rotating magnetic field can be obtained.

[0035] 5. The test coil in this invention can achieve correction compensation, thereby improving test accuracy. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of an in-situ magnetic property testing method for thin plates according to the present invention;

[0037] Figure 2 This is a flowchart of a method for testing the in-situ magnetic properties of a thin plate according to the present invention;

[0038] Figure 3 This is a schematic diagram of the magnetic yoke and magnetic flux density flow direction of the present invention;

[0039] Figure 4 This is a schematic diagram of the measurement point selection for the present invention;

[0040] Figure 5 This is a schematic diagram of the test scheme structure of the present invention;

[0041] Figure 6 This is a diagram of the sample magnetic field strength testing method of the present invention;

[0042] Figure 7 This is a diagram illustrating the magnetic induction intensity testing method for the sample according to the present invention;

[0043] In the figure: 1. Vacuum chuck; 2. Magnetic yoke; 3. Rotary support base; 4. Lifting support frame; 5. Moving base; 6. Non-magnetic electric push rod; 7. Measurement component; 8. Thin plate sample; 9. Excitation coil; 10. First coil; 11. Second coil; 7-1. Measurement base; 7-2. Magnetic induction intensity probe; 7-3. Magnetic field strength test coil. Detailed Implementation

[0044] The present invention will become clearer from the following detailed description with reference to the accompanying drawings and preferred embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0045] like Figure 1As shown, the testing device involved in the thin-plate in-situ magnetic property testing method of the present invention consists of a movable base 5, a lifting support frame 4, a rotating support seat 3, a measuring component 7, a vacuum chuck 1, and a magnetic yoke 2. The movable base 5 is used to move the testing device to the position to be tested. By adjusting the height of the lifting support frame 4, which is fixedly connected to the movable base 5, and adjusting the angle of the rotating support seat 3, which is hinged to the lifting support frame 4, the measuring posture of the testing device can be adjusted so that the magnetic yoke 2 faces and approaches the thin-plate sample 8. When the magnetic yoke 2 is close to the thin-plate sample 8, the vacuum chuck 1, which is fixedly connected to the magnetic yoke 2 and the rotating support seat 3, attracts and fixes the testing device and the thin-plate sample 8. At the same time, the movable joints of the movable base 5, the lifting support frame 4, and the rotating support seat 3 are locked to ensure that the relative position of the testing device and the thin-plate sample 8 remains fixed during the test. After the testing device position is locked, the magnetic yoke 2 and the thin-plate sample 8 form a closed loop, and the data acquisition process can be started.

[0046] like Figure 2 As shown, the thin-plate in-situ magnetic property testing method of the present invention includes the following steps:

[0047] Step (1) Adjust the height and angle of the test device by moving the base 5, lifting support frame 4, and rotating support seat 3 so that the test device is close to the thin plate sample 8 to be tested for magnetism;

[0048] Step (2) Place the auxiliary magnetic yoke 2 close to the thin plate sample 8, and lock the vacuum suction cup 1, the movable base 5, the lifting support frame 4, and the rotating support seat 3.

[0049] Step (3) Start the data acquisition process, and the measurement component 7 automatically approaches the thin plate sample 8;

[0050] The data acquisition process is detailed below: Figure 1 As shown, the measuring component 7 is first pushed close to the thin plate sample 8 by the non-magnetic electric push rod 6. One end of the non-magnetic electric push rod 6 is fixedly connected to the rotating support 3, and the other end is bolted to the measuring component 7. The contact surface between the measuring component 7 and the magnetic yoke 2 is made of a non-magnetic, wear-resistant, and low-resistance material, allowing the measuring component 7 to slide smoothly within the magnetic yoke 2. After the measuring component 7 reaches the test position under the push of the non-magnetic electric push rod 6, an excitation current is applied through the excitation coil 9 wound on the magnetic yoke 2, such as... Figure 3 As shown, a controllable magnetic flux density is formed in the closed loop formed by the thin plate sample 8. By adjusting the current of the excitation coil 9, magnetic field strength and magnetic induction intensity of different amplitudes can be formed in the thin plate sample 8, thereby obtaining the complete magnetic hysteresis characteristics of the sample.

[0051] Step (4) Select the test mode (DC, AC, etc.), and the excitation coil 9 will be loaded with current according to the set program;

[0052] In the test mode, either DC or AC mode is selected as needed. DC mode is used to obtain the DC magnetic characteristics of the thin-plate sample 8 with an amplitude up to 200kA, while AC mode is used to obtain the AC magnetic characteristics of the thin-plate sample 8 within a frequency range of 20Hz to 20kHz. The excitation current input is preferably a pulse waveform with different amplitudes; waveforms that continuously increase or decrease can also be used. In AC mode, different hysteresis characteristics of the thin-plate sample 8 can be obtained by adjusting the frequency of the excitation current. The recommended number of turns for the excitation coil 9 is 200–300 turns.

[0053] Step (5) Select the target measurement point according to the test requirements, acquire data through the measurement component 7, and acquire the test graph and test data on the host computer using data transmission software and hardware;

[0054] like Figure 4 As shown, the method for selecting target measurement points on the thin plate sample 8 is as follows: The typical size of the thin plate sample 8 is 400mm × 400mm, and the minimum test area of ​​the measuring component 7 is 50mm × 50mm. Therefore, the spacing between measurement points on the thin plate sample 8 should be more than 50mm. Simultaneously, considering the uniform magnetic excitation area within the thin plate sample, the test points should be selected at least 50mm from the edge. Therefore, for a 400mm × 400mm thin plate sample 8, the maximum number of measurement points is 6 × 6 = 36.

[0055] like Figure 5 As shown, the measurement assembly 7 consists of a measurement base 7-1, a magnetic induction intensity probe 7-2, and a magnetic field intensity coil 7-3. The magnetic induction intensity probe 7-2 and the magnetic field intensity coil 7-3 are fixedly connected to the measurement base 7-1 and, driven by the non-magnetic electric actuator 6, approach the thin plate sample 8 to acquire magnetic signals. In one implementation, the magnetic induction intensity probe 7-2 is arranged with two pairs of needles (4 needles), each representing a magnetic induction intensity B in two perpendicular directions. Driven by the non-magnetic electric actuator 6, the needles of the magnetic induction intensity probe 7-2 contact and contract with the thin plate sample 8, forming a conductive path. This allows the potential difference between the contact points to be obtained, and the magnetic induction intensity B between the test points can be further calculated. In another implementation, the magnetic field intensity coil 7-3 is arranged in two overlapping layers. Each layer consists of two sets of mutually perpendicular first coils 10 and second coils 11 wound to acquire the magnetic field intensity H of the thin plate sample 8 in two perpendicular directions. The two overlapping layers of magnetic field intensity coils 7-3 are used to correct the value of the magnetic field intensity H, improving the test accuracy. Meanwhile, depending on the testing requirements, the magnetic field strength coil and the magnetic induction intensity probe can also be arranged as a pair to obtain the unidirectional magnetic field strength H and magnetic induction intensity B.

[0056] The test of magnetic field strength H is as follows: Figure 6As shown, according to the boundary conditions of Maxwell's equations, the magnetic field strength H is the same at the interface of different magnetic media, and this method can be used to test the magnetic field strength H. When the magnetic field strength coil 7-3 is close to the thin plate sample 8, the magnetic field strength sensed by the magnetic field strength coil can be considered to be the magnetic field strength inside the thin plate sample 8. Based on electromagnetic induction, the magnetic field strength H1 of the magnetic field strength coil close to the sample 8 can be calculated as follows:

[0057]

[0058] Where: μ0—vacuum permeability; N H1 —Magnetic field strength; number of coil turns; S H1 — Cross-sectional area of ​​the magnetic flux density perpendicular to the magnetic field strength coil; U1 — Induced electromotive force inside the magnetic field strength coil.

[0059] Based on the magnetic field distribution at the interface of different media, the magnetic field strength H near the interface exhibits a linear relationship with the distance L from the interface. Therefore, the magnetic field strength H1 obtained by the magnetic field strength coil has a certain error compared to the actual internal magnetic field strength H0 of the thin plate sample 8. To improve the testing accuracy, another magnetic field strength coil with a different distance was used to measure the magnetic field strength H2. Based on the linear relationship of magnetic field strength, the corrected internal magnetic field strength H0 of the thin plate sample 8 can be obtained as follows:

[0060]

[0061] Wherein: H1—magnetic field strength measured by the magnetic field strength coil near the test sample 8; L1—distance between the magnetic field strength coil near the test sample 8 and the thin plate sample 8; H2—magnetic field strength measured by the magnetic field strength coil away from the thin plate sample 8; L2—distance between the magnetic field strength coil away from the thin plate sample 8 and the thin plate sample 8.

[0062] The method for testing magnetic flux density B is as follows: Figure 7 As shown, to increase the convenience of testing and use in-situ measurement, a probe method is used instead of the wire-wound method to test the magnetic induction intensity B. Driven by the non-magnetic electric actuator 6, the magnetic induction intensity probe 7-2 contacts and compresses the thin plate sample 8. Therefore, the probe and the thin plate sample 8 form a conductive path. When the magnetic induction intensity B within the thin plate sample changes, according to the electromagnetic induction theorem, an induced electromotive force (EMF) is generated in the closed-loop path abcda. This induced EMF can be measured by a pair of magnetic induction intensity probes (the induced EMF obtained by probe ab is half of the closed-loop path abcda). Thus, the magnetic induction intensity B can be obtained as follows:

[0063]

[0064] Wherein: S B—The cross-sectional area formed by the magnetic induction intensity probe test position and the sample; U —The induced electromotive force detected by the magnetic induction intensity probe.

[0065] Step (6) Repeat steps (1) to (5) according to the test requirements to collect data from different test positions of the thin plate sample 8;

[0066] Step (7) Complete the test and remove the test device.

[0067] The thin-plate in-situ magnetic property testing method of the present invention involves placing the testing device close to the thin-plate sample 8 and using a magnetic field strength coil and a magnetic induction intensity probe to obtain the magnetic field strength and magnetic induction intensity of the sample under test, respectively. Therefore, by adjusting the height and angle of the testing device, magnetic property testing can be achieved at any position of the entire shield. By changing the shape of the magnetic yoke 2 and adjusting the position of the vacuum chuck 1, the present invention can extend this testing method to in-situ testing of magnetic shields of different shapes (arc surfaces, planes, etc.).

[0068] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for testing the in-situ magnetic properties of a thin plate, characterized in that, The testing device involved in the in-situ magnetic property testing method for thin plates includes a movable base, a lifting support frame, a rotating support, a measuring component, a vacuum chuck, and a magnetic yoke. The movable base is used to move the testing device to the position to be tested. By adjusting the height of the lifting support frame, which is fixedly connected to the movable base, and adjusting the angle of the rotating support seat, which is hinged to the lifting support frame, the measuring posture of the testing device is adjusted so that the magnetic yoke is facing and close to the thin plate sample. When the magnetic yoke is close to the thin plate sample, the vacuum chuck, which is fixedly connected to the magnetic yoke and the rotating support seat, is used to attract and fix the testing device and the thin plate sample. Simultaneously, the movable joints of the movable base, the lifting support frame, and the rotating support seat are locked to ensure that the relative position of the testing device and the thin plate sample remains fixed during the test. After the test device is locked in position, the magnetic yoke and the thin plate sample form a closed loop, and the data acquisition process is started. First, the measuring component is pushed close to the thin plate sample by a non-magnetic electric push rod. One end of the non-magnetic electric push rod is fixedly connected to the rotating support base, and the other end is connected to the measuring component. The contact surface between the measuring component and the magnetic yoke is made of a non-magnetic, wear-resistant, and low-resistance material, which allows the measuring component to slide smoothly within the magnetic yoke. When the measuring component reaches the test position under the push of the non-magnetic electric push rod, an excitation current is applied through the excitation coil wound on the magnetic yoke to form a controllable magnetic flux density in the closed loop formed by the thin plate sample. By adjusting the current of the excitation coil, magnetic field strength and magnetic induction intensity of different amplitudes are formed in the thin plate sample, thereby obtaining the complete magnetic hysteresis characteristics of the sample. The method includes the following steps: Step (1) Adjust the height and angle of the testing device by moving the base, lifting support frame and rotating support seat so that the testing device is close to the thin plate sample to be tested; Step (2) Place the auxiliary magnetic yoke close to the thin plate sample and lock the vacuum suction cup, moving base, lifting support frame, and rotating support seat; Step (3) Start the data acquisition process, and the measuring component automatically approaches the thin plate sample; Step (4) Select the test mode, and apply current to the excitation coil according to the set test mode; Step (5) Select the target measurement point according to the test requirements, acquire data through the measurement component, and acquire the test curve and test data on the host computer using data transmission software and hardware; Step (6) Repeat steps (1) to (5) according to the test requirements to collect data at different test locations of the thin plate sample; Step (7) Complete the test and remove the test device.

2. The method for testing the in-situ magnetic properties of a thin plate according to claim 1, characterized in that, Step (1) includes: using a movable base to move the test device to the position to be tested, adjusting the height of the lifting support frame fixedly connected to the movable base and adjusting the angle of the rotating support seat hinged to the lifting support frame to adjust the measurement posture of the test device so that the magnetic yoke is facing and close to the thin plate sample.

3. The method for testing the in-situ magnetic properties of a thin plate according to claim 2, characterized in that, Step (2) includes: when the magnetic yoke is close to the thin plate sample, the test device and the thin plate sample are attracted and fixed by the vacuum chuck fixedly connected to the magnetic yoke and the rotating support seat, and the movable joints of the movable base, the lifting support frame and the rotating support seat are locked to ensure that the relative position of the test device and the thin plate sample remains fixed during the test; after the position of the test device is locked, the magnetic yoke and the thin plate sample form a closed loop.

4. The method for testing the in-situ magnetic properties of a thin plate according to claim 3, characterized in that, In step (3), the data acquisition stream includes: firstly, pushing the measurement component close to the thin plate sample by a non-magnetic electric push rod, one end of the non-magnetic electric push rod is fixedly connected to the rotating support base, and the other end is bolted to the measurement component; after the measurement component reaches the test position under the push of the non-magnetic electric push rod, an excitation current is applied by the excitation coil wound on the magnetic yoke, and a controllable magnetic flux density is formed in the closed loop formed by the thin plate sample. By adjusting the current of the excitation coil, magnetic field strength and magnetic induction intensity of different amplitudes are formed in the thin plate sample, thereby obtaining the complete magnetic hysteresis characteristics of the thin plate sample.

5. The method for testing the in-situ magnetic properties of a thin plate according to claim 4, characterized in that, In step (4), the test mode includes a DC mode or an AC mode. The DC mode is used to obtain the DC magnetic characteristics of the thin plate sample with an amplitude of less than 200kA, and the AC mode is used to obtain the AC magnetic characteristics of the thin plate sample with a frequency range of 20Hz to 20kHz. The excitation current input is a pulse waveform with different amplitudes, or a waveform that continuously increases or decreases. In the AC mode, different hysteresis characteristics of the thin plate sample are obtained by adjusting the frequency of the excitation current of the excitation coil. The number of turns of the excitation coil is 200 to 300.

6. The method for testing the in-situ magnetic properties of a thin plate according to claim 5, characterized in that, In step (5), the method for selecting target measurement points of the thin plate sample is as follows: the size of the thin plate sample is 400mm×400mm, and the minimum test area of ​​the measurement component is 50mm×50mm. Therefore, the spacing between measurement points on the thin plate sample is more than 50mm. At the same time, considering the uniform magnetic excitation area in the thin plate sample, the test points are selected at a distance of more than 50mm from the edge. Therefore, for a 400mm×400mm thin plate sample, the maximum number of measurement points is 6×6=36.

7. The method for testing the in-situ magnetic properties of a thin plate according to claim 6, characterized in that, The measurement component in step (5) consists of a measurement base, a magnetic induction intensity probe, and a magnetic field intensity coil. The magnetic induction intensity probe and the magnetic field intensity coil are fixedly connected to the measurement base. Driven by a non-magnetic electric push rod, they approach the thin plate sample to acquire magnetic signals. Driven by a non-magnetic electric push rod, the tip of the magnetic induction intensity probe contacts and contracts with the thin plate sample to form an electrical conduction path, thereby obtaining the potential difference between the contact points and further calculating the magnetic induction intensity between the test points.

8. The method for testing the in-situ magnetic properties of a thin plate according to claim 7, characterized in that, The magnetic field strength coil comprises two layers stacked on top of each other. Each layer is wound with two sets of first and second coils that are perpendicular to each other, so as to obtain the magnetic field strength of the thin plate sample in two perpendicular directions. Based on electromagnetic induction, the magnetic field strength H1 of the coil near the thin plate sample is calculated as follows: ； in: —Vacuum permeability; —Magnetic field strength; number of coil turns; —The cross-sectional area of ​​the perpendicular magnetic flux density inside the coil; —Magnetic field strength induced electromotive force inside the coil; The magnetic field strength H2 was obtained from testing another layer away from the magnetic field strength coil. Based on the linear relationship of magnetic field strength, the corrected internal magnetic field strength H0 of the thin plate sample is as follows: ； in: —Magnetic field strength measured by a coil near the test sample; —The distance between the magnetic field strength coil near the test sample and the thin plate sample; —Magnetic field strength measured by a coil away from the thin plate sample; — The distance between the magnetic field strength coil and the thin plate sample.

9. The method for testing the in-situ magnetic properties of a thin plate according to claim 7, characterized in that, According to the principle of electromagnetic induction, the formula for calculating magnetic field strength is: ； in: —The cross-sectional area formed by the magnetic induction intensity probe test position and the sample; —Induced electromotive force detected by a magnetic induction intensity probe.

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