Electromagnetic eddy current magnetic focusing probe and detection method thereof

Abstract

The application provides an electromagnetic eddy current magnetic focusing detection probe and a detection method thereof. The probe comprises a shell, a plurality of integrated signal generating devices and receiving devices are arranged in the shell, an electromagnetic shielding device is arranged between adjacent integrated signal generating devices and receiving devices, a coaxial signal receiving device is mounted on the upper side of the center of each integrated signal generating device and receiving device, the coaxial signal receiving device and the integrated signal generating device and receiving device have a height difference in spatial position, and the integrated signal generating device and receiving device and the coaxial signal receiving device are connected with a host through a transmission port. The independent parallel detection module can accurately determine the position and depth of defects, improve the signal quality and anti-interference ability, and cope with complex working conditions.

Description

Technical Field

[0001] This invention relates to the field of eddy current electromagnetic flaw detection technology, and in particular to an electromagnetic eddy current magnetic focusing probe and its detection method. Background Technology

[0002] The core principle of electromagnetic nondestructive testing is to identify defects in ferromagnetic / conductive components, such as cracks, corrosion, wall thinning, delamination, and magnetic field distortion of defects, by utilizing differences in electromagnetic induction, permeability, eddy current, leakage flux, and electromagnetic attenuation.

[0003] Eddy current detection is based on the principle of electromagnetic induction. Its basic principle is as follows: When an AC signal is used to excite a coil, the coil will generate an excitation magnetic field. If a conductor approaches, eddy current signals will be generated in the conductor. The eddy currents will then generate an eddy current magnetic field that acts on the coil. The thickness of the conductor will cause changes in the eddy current signals, which in turn affect the eddy current magnetic field. This change is ultimately reflected in the coil. Therefore, by obtaining this change in the coil through appropriate methods, the thickness of the conductor can be distinguished and calculated. However, existing eddy current detection technologies suffer from weak defect response signals and low signal-to-noise ratios. Deep defect signals are severely attenuated, resulting in weak effective signals. They are also susceptible to stray electromagnetic interference from the environment and materials, increasing the difficulty of signal recognition and defect determination.

[0004] The applicant intends to design a new electromagnetic eddy current magnetic focusing detection method and detection probe to solve the above-mentioned technical problems. After a detailed search, no relevant existing technologies were found.

[0005] Therefore, a new technical solution is needed to solve the above-mentioned technical problems. Summary of the Invention

[0006] This application provides an electromagnetic eddy current magnetic focusing detection probe, including a housing, within which multiple integrated signal generating and receiving devices are arranged coaxially in parallel. An electromagnetic shielding device is provided between adjacent integrated signal generating and receiving devices. A coaxial signal receiving device is installed on the upper center of each integrated signal generating and receiving device. There is a height difference between the coaxial signal receiving device and the integrated signal generating and receiving device in spatial position. The integrated signal generating and receiving devices and the coaxial signal receiving device are connected to a host through a transmission port.

[0007] As a preferred embodiment, the height difference is 3mm-10mm.

[0008] As a preferred embodiment, the electromagnetic shielding device is made of permalloy.

[0009] As a preferred embodiment, the bottom of the housing is provided with a heat-resistant insulation plate.

[0010] As a preferred embodiment, the integrated signal generating and receiving device is composed of three layers of stacked coils. The outermost and innermost coils are wound in the same way, while the middle coil is wound in the opposite way to the other two coils. The outermost coil is the signal output coil, which outputs different excitation signals according to the material of the workpiece under test. The innermost coil is the signal receiving unit, which receives the electromagnetic signals of the workpiece under test. The middle coil utilizes reverse coupling to quickly absorb the self-inductance signals generated by the other two sides when the signals change abruptly.

[0011] This application provides an electromagnetic eddy current magnetic focusing detection method, including the following steps: S1: Place the electromagnetic eddy current magnetic focusing probe on the workpiece to be tested; S2: The host controls the integrated signal generator and receiver to emit multi-frequency electromagnetic signals, and the integrated signal generator and receiver and the coaxial signal receiver simultaneously receive the multi-frequency electromagnetic signals. S3: The received multi-frequency electromagnetic signal is sent to the host, which processes the multi-frequency electromagnetic signal to form data; S4: The host computer determines the type of defect by analyzing the phase time difference of the data; S5: Determine the defect length and defect depth; As a preferred embodiment, S4 specifically comprises: S41: The collected data is based on... Establish an electromagnetic field model for the workpiece to be tested, wherein, The electromagnetic field model of the workpiece to be tested. This is a model of the magnetic field received by an integrated signal generator and receiver. A model of the magnetic field received by a coaxial signal receiving device; , Let be the conductivity constant of the workpiece under test. J(ar) is the weighted average of the conductivity of each integrated signal generator and receiver, and J(ar) is the induced magnetic field function of the workpiece under test. The induced magnetic field function of the weld seam of the workpiece under test. This is a function of the magnetic field direction. The voltage intensity in the integrated signal generator and receiver; , Let be the conductivity constant of the workpiece under test. This is a weighted average of the conductivity of each coaxial signal receiving device. , The first Fourier expansion of the induced magnetic field of the workpiece under test is given. The voltage level in a coaxial signal receiving device. Let be the radial coordinate of the nth coaxial signal receiving device; For the weighting coefficient of the nth coaxial signal receiving device; S42: At the beginning of the test, raw data is collected and calibrated while the workpiece is intact to determine the overall magnetic field at the intact position. According to the zeroing method This will serve as the zero point for subsequent testing records, and the corresponding values ​​will be stored in the database; S43: During subsequent defect detection, continuous signal zero-point offsets within a single sampling period can be recorded as defects, and the magnetic field at the defect location will be recorded. pass Fourier expansion is performed, and the defect type is determined by analyzing the phase time difference. If a negative amplitude change occurs and a positive amplitude change occurs when the defect appears, it is determined to be a band defect; otherwise, it is a regional defect.

[0012] As a preferred embodiment, in S5, the defect length L = v × Δt, where v represents the speed of the integrated signal generator and receiver, and Δt represents the duration of the detected defect signal. The duration of the detected defect signal is the time from when the defect first enters the detection range of the integrated signal generator and receiver and the coaxial signal receiver, until the magnetic field of the integrated signal generator and receiver and the coaxial signal receiver is completely restored to normal.

[0013] As a preferred approach, the determination of defect depth involves first calculating the amplitude A of the defect distortion eddy current field, and then calculating the defect depth h based on the amplitude A of the defect distortion eddy current field and the calibration coefficient k. in, , R represents the amplitude of the defect-distorted eddy current field. Represents the permeability of the coil in an integrated signal generator and receiver. Indicates the dielectric constant. Let be the conductivity constant of the workpiece under test. , This indicates the diameter of the coil in the integrated signal generator and receiver. For angular components, The vertical magnetic field strength; Defect depth h = k represents the calibration coefficient, which is fixed under the same material and the same testing parameters.

[0014] This invention employs an integrated signal generating and receiving device to improve sensor utilization efficiency, increase the effective receiving area of ​​the sensor, and improve signal quality. Combined with a coaxial signal receiving device, it further enhances signal quality, enabling the detection of cracks and defects in the metal body. The use of independent parallel detection modules can accurately determine the location and depth of defects, while improving signal quality and anti-interference capabilities, and enabling it to cope with complex working conditions. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure from one angle of Embodiment 1 of this application; Figure 2 This is a schematic diagram of the structure from angle two of Embodiment 1 of this application; Figure 3 This is a schematic diagram of Embodiment 3 of this application; Figure label: 1. Housing; 2. Integrated signal generator and receiver; 3. Electromagnetic shielding device; 4. Coaxial signal receiver; 5. Transmission port; 6. Heat-resistant insulation board; 7. Workpiece to be tested. Detailed Implementation

[0016] The following is in conjunction with the appendix Figure 1 To be continued Figure 3 The specific embodiments of the present invention will be described in detail below. It should be noted that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the present invention. Example 1

[0017] This application provides an electromagnetic eddy current magnetic focusing probe, including a housing 1. Multiple integrated signal generating and receiving devices 2 are disposed within the housing 1. Specifically, the integrated signal generating and receiving devices 2 are composed of three layers of nested coils. The outermost and innermost coils have the same winding method, while the middle coil has the opposite winding method to the other two layers. The outermost coil is the signal output coil, i.e., the driving end, which outputs different excitation signals according to the material of the workpiece under test. The innermost layer is the signal receiving unit, receiving the electromagnetic signal from the workpiece under test. The middle coil can utilize reverse coupling to quickly absorb the self-inductance signals generated by the other two sides during signal abrupt changes, thereby achieving rapid signal rise and rapid attenuation. The multiple integrated signal generating and receiving devices 2 are arranged coaxially in parallel. An electromagnetic shielding device 3 is disposed between adjacent integrated signal generating and receiving devices 2. The electromagnetic shielding device 3 is made of permalloy and is used to absorb the electromagnetic energy radiated to both sides by the integrated signal generating and receiving devices 2. To ensure the signal-to-noise ratio and stability of the independent integrated signal generator and receiver 2, a coaxial signal receiver 4 is installed on the upper center of each integrated signal generator and receiver 2. The coaxial signal receiver 4 and the integrated signal generator and receiver 2 are installed in a central coaxial manner, which can collect strong signals from the center of the induced magnetic field, which is beneficial for the detection of defect signals. There is a height difference between the coaxial signal receiver 4 and the integrated signal generator and receiver 2 in spatial position. When collecting signals from the same source induced magnetic field, there are differences in signal amplitude and phase. The type of defect is determined by analyzing the phase time difference, and the defect signal is enhanced by unified data processing. Specifically, within the detection range, such as carbon steel ≤15mm and stainless steel ≤30mm, a database of defect types and defect depths is established, and the corresponding signals of defect characteristics are entered to determine the defect signal type. The type of defect is determined by analyzing the phase time difference. If a negative amplitude change occurs and a positive amplitude change occurs when the defect is detected, it is judged as a band defect; otherwise, it is a regional defect. The defect length is calculated as follows: Defect length L = v × Δt, where v represents the speed of the integrated signal generator and receiver, and Δt represents the duration of the detected defect signal. The duration of the detected defect signal is the time from when the defect first enters the detection range of the integrated signal generator and receiver 2 and the coaxial signal receiver 4 until the magnetic field of the integrated signal generator and receiver 2 and the coaxial signal receiver 4 is completely restored to normal.

[0018] To determine the depth of a defect, first calculate the amplitude A of the distorted eddy current field of the defect, and then calculate the depth h of the defect based on the amplitude A of the distorted eddy current field of the defect and the calibration coefficient k. in, , R represents the amplitude of the defect-distorted eddy current field. Represents the permeability of the coil in an integrated signal generator and receiver. Indicates the dielectric constant. Let be the conductivity constant of the workpiece under test. , This refers to the diameter of the coil in an integrated signal generator and receiver, more specifically, the diameter of the outermost coil. For angular components, The vertical magnetic field strength; Defect depth h = k represents the calibration coefficient, which is fixed under the same material and the same testing parameters.

[0019] Specifically, the height difference is set as follows: the electromagnetic signal intensity in the air attenuates exponentially with the natural number e as the base, and it is excited by a fixed 8V voltage. The induced signal attenuates to 0.01mV in the air, and its maximum lift is 12mm. To ensure the stability of the received signal, the height difference of the coaxial signal receiving device is 3mm-10mm. The aforementioned integrated signal generator and receiver 2 and coaxial signal receiver 4 are connected to the host through the transmission port 5. The host transmits excitation signals and receives induction signals through the transmission port 4.

[0020] Preferably, the bottom of the housing 1 is provided with a heat-resistant insulation plate 6. The heat-resistant insulation plate 6 can better protect the integrated signal generator and receiver 2, the electromagnetic shielding device 3, and the coaxial signal receiver 4, so as to meet the need for the probe to work in a high-temperature environment and extend its service life. Example 2

[0021] This embodiment provides an electromagnetic eddy current magnetic focusing detection method, including the following steps: S1: Place the electromagnetic eddy current magnetic focusing probe on the workpiece 7 to be tested; S2: The host controls the integrated signal generator and receiver 2 to emit multi-frequency electromagnetic signals, and the integrated signal generator and receiver 2 and the coaxial signal receiver 4 simultaneously receive the multi-frequency electromagnetic signals. S3: The received multi-frequency electromagnetic signal is sent to the host. The host processes the multi-frequency electromagnetic signal to form data. Specifically, the multi-frequency electromagnetic signal is subjected to filtering and noise reduction, DC removal, Fourier frequency division and separation, amplitude and phase feature extraction, error correction and data normalization in sequence to complete the quantization of multi-dimensional electromagnetic features and finally organize and generate structured usable data.

[0022] S4: The host computer determines the type of defect by analyzing the phase time difference of the data; specifically: S41: The collected data is based on... Establish an electromagnetic field model for the workpiece to be tested, wherein, The electromagnetic field model of the workpiece to be tested. This is a model of the magnetic field received by an integrated signal generator and receiver. A model of the magnetic field received by a coaxial signal receiving device; , Let be the conductivity constant of the workpiece under test. Let J(ar) be the weighted average of the conductivity of the integrated signal generating and receiving devices, and let J(ar) be the induced magnetic field function of the workpiece under test. The induced magnetic field function of the weld seam of the workpiece under test. This is a function of the magnetic field direction. The voltage intensity of the signal generating and receiving devices is integrated into one unit; , Let be the conductivity constant of the workpiece under test. This is a weighted average of the conductivity of each coaxial signal receiving device. , Let be the first Fourier expansion of the induced magnetic field of the workpiece under test, and 'a' be the voltage intensity in the coaxial signal receiving device. Let be the radial coordinate of the nth coaxial signal receiving device; For the weighting coefficient of the nth coaxial signal receiving device; S42: At the beginning of the test, raw data is collected and calibrated while the workpiece is intact to determine the overall magnetic field at the intact position. According to the zeroing method This will serve as the zero point for subsequent testing records, and the corresponding values ​​will be stored in the database; S43: During subsequent defect detection, continuous signal zero-point offsets within a single sampling period can be recorded as defects, and the magnetic field at the defect location will be recorded. pass Fourier expansion is performed, and the defect type is determined by analyzing the phase time difference. If a negative amplitude change occurs and a positive amplitude change occurs when the defect appears, it is judged as a band defect; otherwise, it is a regional defect, also known as a circular defect. Band defects cut the magnetic field, causing the magnetic field to be distorted and changing the overall phase and amplitude changes. S5: Determine the defect length and defect depth; The defect length is determined by the time Δt taken from the moment the defect first enters the detection range of the integrated signal generator and receiver, causing magnetic field distortion, to the moment the magnetic field of the integrated signal generator and receiver fully recovers to normal. Combined with the travel speed of the integrated signal generator and receiver, the defect length L can be calculated as follows: Defect length L = v × Δt, where v represents the travel speed of the integrated signal generator and receiver, and Δt represents the duration of the detected defect signal.

[0023] Determination of defect depth: First, calculate the amplitude of the defect distortion eddy current field, and then calculate the defect depth h based on the amplitude of the defect distortion eddy current field and the calibration coefficient k. in, , R represents the amplitude of the defect-distorted eddy current field. Represents the permeability of the coil in an integrated signal generator and receiver. Indicates the dielectric constant. Let be the conductivity constant of the workpiece under test. , This indicates the diameter of the coil in the integrated signal generator and receiver. For angular components, The vertical magnetic field strength; Defect depth h = k represents the calibration coefficient, which is fixed under the same material and the same testing parameters. Example 3

[0024] This embodiment provides a specific application scenario for detecting welding defects in aluminum alloy materials; The electromagnetic eddy current magnetic focusing probe in this embodiment includes three integrated signal generating and receiving devices 2 arranged coaxially in parallel. Figure 3 Modules A1, A2, and A3 represent three integrated signal generators and receivers 2, respectively. An electromagnetic shielding device 3 made of permalloy is set between two adjacent integrated signal generators and receivers 2 to absorb the electromagnetic energy signals radiated to both sides by the integrated signal generators and receivers 2, ensuring the signal-to-noise ratio and stability of the independent sensors. The rest of the structure is the same as in Embodiment 1, and will not be described in detail here.

[0025] The electromagnetic eddy current magnetic focusing detection method of this embodiment includes the following steps: S1: Place the electromagnetic eddy current magnetic focusing probe on the workpiece 7 to be tested; the workpiece 7 to be tested is a weld test plate. S2: The host controls the integrated signal generator and receiver 2 to emit multi-frequency electromagnetic signals, and the integrated signal generator and receiver 2 and the coaxial signal receiver 4 simultaneously receive the multi-frequency electromagnetic signals. S3: The received multi-frequency electromagnetic signal is sent to the host, which processes the multi-frequency electromagnetic signal to form data; S4: The host computer determines the type of defect by analyzing the phase time difference of the data; specifically: S41: The collected data is based on... An electromagnetic field model of the weld test plate was established, in which... Electromagnetic field model of weld test plate, This is a model of the magnetic field received by an integrated signal generator and receiver. A model of the magnetic field received by a coaxial signal receiving device; , Let be the electrical conductivity constant of the weld test plate. J(ar) is the weighted average of the conductivity of the three integrated signal generators and receivers, and J(ar) is the induced magnetic field function of the weld test plate. The induced magnetic field function of the weld is... This is a function of the magnetic field direction. The voltage intensity in the integrated signal generator and receiver; , Let be the electrical conductivity constant of the weld test plate. Let be the conductivity constant of the three coaxial signal receiving devices. The Fourier expansion of the induced magnetic field in the weld test plate is given. This refers to the voltage intensity in a coaxial signal receiving device.

[0026] S42: At the beginning of the inspection, raw data is collected and calibrated on the intact weld test plate to determine the overall magnetic field of the intact location. According to the zeroing method This will serve as the zero point for subsequent testing records, and the corresponding values ​​will be stored in the database; S43: During subsequent defect detection, continuous signal zero-point offsets within a single sampling period can be recorded as defects, and the magnetic field at the defect location will be recorded. pass Fourier expansion is performed, and the defect type is determined by analyzing the phase time difference. If a negative amplitude change occurs and a positive amplitude change occurs when the defect appears, it is determined to be a band defect; otherwise, it is a regional defect, which can also be called a circular defect. S5: Determine the defect length and defect depth; The calculation of defect length is as follows in this embodiment: Figure 3The defect shown is that the three integrated signal generators and receivers correspond to modules A1, A2, and A3 respectively, and the magnetic field of module A1 is used to address this issue. Magnetic field of module A3 Determine the defect length; max( ) represents the time it takes for the integrated signal generator and receiver to enter the defect, min( The time when the integrated signal generator and receiver device develops a defect; in this embodiment, the three data points of defect length need to be compared, because A1 and A3 are the two ends of the probe respectively. If the defect length exceeds the distance between A1 and A2, then A3 is needed to analyze the subsequent data length.

[0027] Determine the depth of the defect; like Figure 3 As shown, the deepest point of the defect is at module A2, therefore, the defect depth is determined using module A2: in, , R represents the amplitude of the defect-distorted eddy current field. Represents the permeability of the coil in an integrated signal generator and receiver. Indicates the dielectric constant. Let be the electrical conductivity constant of the weld test plate. Defect depth h = k represents the calibration coefficient, which is fixed under the same material and the same testing parameters.

[0028] In summary, due to the adoption of the above technical solution, the present invention has the following beneficial effects: 1. This invention can be used for crack defect detection in welds. Specifically, the host controls an integrated signal generating and receiving device to emit multi-frequency electromagnetic signals. The integrated signal generating and receiving device and the coaxial signal receiving device can enhance the crack defect signal and detect crack defects in welds. In addition, the electromagnetic shielding device applies shielding to shield the electromagnetic disturbance of parallel probes, further improving signal quality and stability. 2. This invention uses an integrated signal generating and receiving device to improve sensor efficiency, increase the effective receiving area of ​​the sensor, and improve signal quality. It is further enhanced by coaxial signal receiving device, which can detect cracks and defects in metal bodies. The independent parallel detection module can accurately determine the location and depth of defects, while improving signal quality and anti-interference ability, and can cope with complex working conditions.

[0029] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the various possible combinations in this application will not be described separately.

[0030] Furthermore, various different implementations of this application can be combined in any way, as long as they do not violate the spirit of this application, and such combinations should also be regarded as the content disclosed in this application.

Claims

1. An electromagnetic eddy current magnetic focusing probe, comprising a housing (1), characterized in that, Multiple integrated signal generators and receivers (2) are installed inside the housing (1). The multiple integrated signal generators and receivers (2) are arranged in a coaxial parallel manner. An electromagnetic shielding device (3) is provided between adjacent integrated signal generators and receivers (2). A coaxial signal receiver (4) is installed on the upper center side of each integrated signal generator and receiver (2). There is a height difference between the coaxial signal receiver (4) and the integrated signal generator and receiver (2) in terms of spatial position. The integrated signal generator and receiver (2) and the coaxial signal receiver (4) are connected to the host through the transmission port (5).

2. The electromagnetic eddy current magnetic focusing probe according to claim 1, characterized in that, The height difference is 3mm-10mm.

3. The electromagnetic eddy current magnetic focusing detection probe according to claim 1, characterized in that, The electromagnetic shielding device (3) is made of permalloy.

4. The electromagnetic eddy current magnetic focusing probe according to claim 1, characterized in that, The bottom of the housing (1) is provided with a heat-resistant insulation plate (6).

5. The electromagnetic eddy current magnetic focusing probe according to claim 1, characterized in that, The integrated signal generating device and receiving device (2) are composed of three layers of coils. The outermost and innermost coils are wound in the same way, while the middle coil is wound in the opposite way to the other two coils. The outermost coil is the signal output coil, which outputs different excitation signals according to the material of the workpiece to be tested. The innermost coil is the signal receiving unit, which receives the electromagnetic signal of the workpiece to be tested. The middle coil uses reverse coupling to absorb the self-inductance signals generated by the other two sides when the signal changes.

6. A method for electromagnetic eddy current magnetic focusing detection, characterized in that, The steps include the following: S1: Place the electromagnetic eddy current magnetic focusing probe on the workpiece (7) to be tested; S2: The host controls the integrated signal generator and receiver (2) to emit multi-frequency electromagnetic signals, and the integrated signal generator and receiver (2) and the coaxial signal receiver (4) simultaneously receive the multi-frequency electromagnetic signals. S3: The received multi-frequency electromagnetic signal is sent to the host, which processes the multi-frequency electromagnetic signal to form data; S4: The host computer determines the type of defect by analyzing the phase time difference of the data; S5: Determine the defect length and defect depth.

7. The electromagnetic eddy current magnetic focusing detection method according to claim 6, characterized in that, S4 includes: S41: The collected data is based on... Establish an electromagnetic field model for the workpiece to be tested, wherein, The electromagnetic field model of the workpiece to be tested. This is a model of the magnetic field received by an integrated signal generator and receiver. A model of the magnetic field received by a coaxial signal receiving device; , Let be the conductivity constant of the workpiece under test. J(ar) is the weighted average of the conductivity of each integrated signal generator and receiver, and J(ar) is the induced magnetic field function of the workpiece under test. The induced magnetic field function of the weld seam of the workpiece under test. It is a function of the direction of the magnetic field; The voltage intensity in the integrated signal generator and receiver; , Let be the conductivity constant of the workpiece under test. This is a weighted average of the conductivity of each coaxial signal receiving device. , The first Fourier expansion of the induced magnetic field of the workpiece under test is given. The voltage level in a coaxial signal receiving device. Let be the radial coordinate of the nth coaxial signal receiving device; For the weighting coefficient of the nth coaxial signal receiving device; S42: At the beginning of the test, raw data is collected and calibrated while the workpiece is intact to determine the overall magnetic field at the intact position. According to the zeroing method This will serve as the zero point for subsequent testing records, and the corresponding values ​​will be stored in the database; S43: During subsequent defect detection, continuous signal zero-point offsets within a single sampling period can be recorded as defects, and the magnetic field at the defect location will be recorded. pass Fourier expansion is performed, and the defect type is determined by analyzing the phase time difference. If a negative amplitude change occurs and a positive amplitude change occurs when the defect appears, it is determined to be a band defect; otherwise, it is a regional defect.

8. The electromagnetic eddy current magnetic focusing detection method according to claim 6, characterized in that, In S5, the defect length L = v × Δt, where v represents the speed of the integrated signal generator and receiver, and Δt represents the duration of the detected defect signal. The duration of the detected defect signal is the time from the defect first entering the detection range of the integrated signal generator and receiver (2) and the coaxial signal receiver (4) to the time when the magnetic field of the integrated signal generator and receiver (2) and the coaxial signal receiver (4) is completely restored to normal.

9. The electromagnetic eddy current magnetic focusing detection method according to claim 6, characterized in that, To determine the depth of a defect, first calculate the amplitude A of the distorted eddy current field of the defect, and then calculate the depth h of the defect based on the amplitude A of the distorted eddy current field of the defect and the calibration coefficient k. in, , R represents the amplitude of the defect-distorted eddy current field. Represents the permeability of the coil in an integrated signal generator and receiver. , Let be the conductivity constant of the workpiece under test. , This indicates the diameter of the coil in the integrated signal generator and receiver. For angular components, The vertical magnetic field strength; Defect depth h = k represents the calibration coefficient, which is fixed under the same material and the same testing parameters.

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