Eddy current modulation detection system and method for magnetic Barkhausen noise

Abstract

The invention belongs to the technical field of electromagnetic nondestructive testing, and particularly discloses an eddy current modulation detection system and method for magnetic Barkhausen noise. Comprising a magnet exciting coil wound on the U-shaped magnet yoke; the ferromagnetic material is arranged towards the pole shoe direction of the U-shaped magnet yoke; the eddy current excitation coil and the eddy current detection coil are arranged between the U-shaped magnet yoke and the ferromagnetic material; the eddy current excitation coil and the eddy current detection coil are positioned between two pole shoes of the U-shaped magnet yoke and are arranged side by side; the distance between the eddy current excitation coil and the ferromagnetic material and the distance between the eddy current detection coil and the ferromagnetic material are fixed; the bipolar current source is electrically connected with the excitation coil; the signal generator is electrically connected with the eddy current excitation coil; and the integral and filter circuit module is electrically connected with the eddy current detection coil. According to the method, the eddy current signal which is high in precision and reflects magnetic Barkhausen noise information can be obtained, so that the detection precision is improved, and the method has the advantages of being higher in detection precision and easier to analyze.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic nondestructive testing, and more specifically, relates to an eddy current modulation detection system and method for magnetic Barkhausen noise. Background Art

[0002] Eddy current testing is a method widely used in the field of non-destructive testing. It uses electromagnetic fields to generate eddy currents to detect defects on the surface or near the surface of an object. However, it has the disadvantage of shallow defect detection depth, and the maximum detection depth is generally no more than 5mm. Magnetized eddy current testing is based on eddy current testing and modulates the magnetic field of the material being tested to detect deep defects in ferromagnetic materials, greatly increasing the detection depth of defects. Currently, defect detection with a burial depth of 20mm can be achieved under laboratory conditions. Magnetic Barkhausen noise detection is the detection of the stress state, plastic deformation, surface hardness, etc. of ferromagnetic materials under AC magnetization. However, there are problems in the detection process such as complex noise signal processing and analysis, which is not conducive to on-site detection. Traditional magnetic Barkhausen noise detection methods and devices cannot meet the needs of high-precision detection of deep defects, especially for on-site detection conditions.

[0003] Chinese patent CN114295258A discloses an electromagnetic composite nondestructive testing sensor, system and method, which integrates the excitation component and receiving component based on different frequency excitation signals into the same sensor, and realizes different nondestructive testing by passing different excitation signals to the first excitation coil and the second excitation coil at different times, including eddy current testing, AC electromagnetic field testing, magnetic Barkhausen noise testing, incremental magnetic permeability testing and other nondestructive testing, thereby being able to obtain stress changes caused by microstructures, the influence of incremental magnetic permeability on stress, and the influence of electrical conductivity and magnetic permeability on stress, so as to accurately judge the stress size of components and provide an experimental verification basis for complex stress theory research. However, this method has the disadvantage of complex magnetic Barkhausen noise signal processing and analysis process in the detection process, and cannot meet the high-precision detection requirements of deep defects.

[0004] In summary, the traditional magnetic Barkhausen noise detection method and device cannot meet the high-precision detection requirements of deep defects, especially for on-site detection conditions. Therefore, it is urgent to develop an eddy current modulation detection method of magnetic Barkhausen noise to adapt to different working conditions and material types and improve the depth and accuracy of eddy current detection. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides an eddy current modulation detection system and method for magnetic Barkhausen noise, wherein an eddy current modulation detection method for magnetic Barkhausen noise is designed accordingly in combination with the characteristics of magnetic Barkhausen noise and the characteristics of eddy current detection process, an eddy current signal reflecting the magnetic Barkhausen noise information is obtained by eddy current modulation, and the peak-to-peak value of the signal is used to characterize the internal corrosion and thinning defects of the ferromagnetic material, thereby greatly improving the detection accuracy and ease of operation, and compensating for the shortcomings that only surface and near-surface defects can be detected due to the eddy current skin effect and the complex processing and analysis process of the magnetic Barkhausen noise signal.

[0006] To achieve the above object, according to one aspect of the present invention, a magnetic Barkhausen noise eddy current modulation detection system is proposed, comprising:

[0007] An excitation coil wound around the U-shaped magnetic yoke;

[0008] A ferromagnetic material disposed toward the pole shoe of the U-shaped magnetic yoke;

[0009] An eddy current excitation coil and an eddy current detection coil are arranged between the U-shaped magnetic yoke and the ferromagnetic material, and the eddy current excitation coil and the eddy current detection coil are arranged side by side between the two pole shoes of the U-shaped magnetic yoke; the distance between the eddy current excitation coil and the eddy current detection coil and the ferromagnetic material is fixed;

[0010] a bipolar current source electrically connected to the excitation coil;

[0011] a signal generator electrically connected to the eddy current excitation coil, and

[0012] an integration and filtering circuit module electrically connected to the eddy current detection coil,

[0013] In this way, the magnetic Barkhausen noise generated by the ferromagnetic material is modulated by the eddy current excitation coil to detect internal defects of the test piece at an optimal modulation frequency.

[0014] As a further preferred embodiment, an industrial computer connected to the integration and filtering circuit module is also included, and the industrial computer is used to display the eddy current signal reflecting the magnetic Barkhausen noise information modulated by the integration and filtering circuit module, so as to determine the defect depth.

[0015] As a further preference, the current of the bipolar current source ranges from 0 to 60A.

[0016] As a further preference, the excitation frequency range of the eddy current excitation coil is 1 kHz to 200 kHz.

[0017] As further preferred, the U-shaped yoke material is MnZn ferrite.

[0018] As a further preference, the eddy current excitation coil and the eddy current detection coil are arranged side by side with a spacing of 0.5 mm.

[0019] As a further preference, the eddy current excitation coil and the eddy current detection coil are both wound with enameled copper wire with a wire diameter of 0.08 mm, and the number of turns is 50.

[0020] As a further preference, the eddy current excitation coil and the eddy current detection coil both have an outer diameter of 4 mm, an inner diameter of 3 mm, and a height of 1 mm.

[0021] According to another aspect of the present invention, there is also provided a method for detecting eddy current modulation of magnetic Barkhausen noise, comprising the following steps:

[0022] Step 1: Loading a low-frequency sinusoidal alternating current to the excitation coil to magnetize the ferromagnetic material using a U-shaped magnetic yoke, so that the ferromagnetic material generates magnetic Barkhausen noise reflecting local magnetic flux density distortion information of the defect;

[0023] Step 2: Load a sinusoidal current to the eddy current excitation coil, the eddy current detection coil receives the electromagnetic field generated by the eddy current excitation coil and induces the magnetic Barkhausen noise of the ferromagnetic material, and the induced voltage of the eddy current detection coil is jointly determined by the magnetic field generated by the eddy current field of the eddy current detection coil and the electromagnetic field generated by the eddy current excitation coil;

[0024] Step 3: fix the eddy current excitation coil and the eddy current detection coil above the ferromagnetic material. When the defect depth is different, the eddy current detection coil obtains the change of the eddy current induced magnetic field, and uses the integration and filtering circuit module to modulate the magnetic Barkhausen noise signal to obtain the eddy current signal reflecting the magnetic Barkhausen noise information, so as to determine the defect depth;

[0025] Step 4: linearly increase the frequency of the voltage applied to the eddy current excitation coil from 0 Hz, and detect internal defects of the test piece at the optimal modulation frequency according to the eddy current modulation signal.

[0026] As a further preferred embodiment, in step four, when the peak-to-peak value of the eddy current signal first increases and then decreases with the increase of the output voltage frequency of the signal generator, the frequency corresponding to the turning point of the voltage amplitude is the optimal frequency of the eddy current modulation, and at this time, the detection accuracy of the magnetic Barkhausen noise eddy current modulation is the highest.

[0027] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0028] 1. The present invention modulates the magnetic Barkhausen noise through the eddy current coil to achieve rapid adjustment of the optimal modulation frequency, and detects internal defects of the test piece at the optimal modulation frequency. At this time, the defect detection accuracy reaches the maximum, and a high-precision eddy current signal can be obtained, thereby improving the accuracy of detection, and has the advantages of higher detection accuracy and easier analysis.

[0029] 2. The present invention firstly adjusts a 0-60A bipolar current source to output a low-frequency sinusoidal alternating current, which is loaded onto an excitation coil to excite a periodically varying magnetizing field, so that the ferromagnetic material generates a magnetic Barkhausen noise reflecting the local magnetic flux density distortion information of the defect, and then fixes an eddy current excitation coil and an eddy current detection coil above the ferromagnetic material, obtains the eddy current induced magnetic field change through the eddy current excitation coil and the eddy current detection coil, detects the defect, and then linearly adjusts the magnitude of the output voltage frequency of the signal generator. When the peak-to-peak value of the eddy current signal first increases and then decreases with the increase of the output voltage frequency of the signal generator, the frequency corresponding to the turning point of the voltage amplitude is the optimal frequency of the eddy current modulation, and at this time, the eddy current modulation detection accuracy is the highest.

[0030] 3. The present invention fixes the distance between the eddy current excitation coil and the eddy current detection coil and the ferromagnetic material to 0.5 mm, and linearly adjusts the frequency of the signal generator output voltage. When the peak-to-peak value of the eddy current signal is maximum, the optimal modulation frequency is achieved, and a higher-precision eddy current signal can be obtained, thereby improving the accuracy of detection.

[0031] 4. The present invention can measure the magnetic Barkhausen noise signal caused by deep defects in ferromagnetic materials under AC magnetization, realize accurate detection of the depth of deep defects, and use eddy current detection coils instead of traditional magnetic Barkhausen noise detection coils to obtain detection signals with high reliability. The magnetic Barkhausen noise is modulated by eddy current coils to realize rapid adjustment of the optimal modulation frequency, and the defects of the test piece are detected at the optimal modulation frequency. At this time, the defect detection accuracy reaches the maximum. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall structure of an eddy current modulation detection system for magnetic Barkhausen noise involved in an embodiment of the present invention;

[0033] Figure 2 It is a flow chart of an eddy current modulation detection method of magnetic Barkhausen noise of the present invention;

[0034] Figure 3 It is the original signal diagram of magnetic Barkhausen noise in the general magnetic Barkhausen noise detection method;

[0035] Figure 4 A phase relationship diagram of an excitation current and an eddy current detection coil voltage signal in an eddy current modulation detection method of a magnetic Barkhausen noise according to the present invention;

[0036] Figure 5 This is a graph showing the relationship between defect signal and defect depth at an optimal modulation frequency in an eddy current modulation detection method of magnetic Barkhausen noise according to the present invention.

[0037] In all the drawings, the same figure marks represent the same technical features, specifically: 1- eddy current excitation coil; 2- eddy current detection coil; 3- U-shaped magnetic yoke; 4- excitation coil; 5- ferromagnetic material; 6- industrial computer; 7- integration and filtering circuit module; 8- signal generator; 9- bipolar current source. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] like Figure 1-2 As shown, an eddy current modulation detection system for magnetic Barkhausen noise provided by an embodiment of the present invention comprises a U-shaped magnetic yoke 3 and an excitation coil 4, wherein the excitation coil 4 is wound on the U-shaped magnetic yoke 3, the pole shoe of the U-shaped magnetic yoke 3 faces the ferromagnetic material 5, an eddy current excitation coil 1 and an eddy current detection coil 2 are arranged between the U-shaped magnetic yoke 3 and the ferromagnetic material 5, and the eddy current excitation coil 1 and the eddy current detection coil 2 are arranged side by side between the two pole shoes; the distances between the eddy current excitation coil 1 and the eddy current detection coil 2 and the ferromagnetic material 5 are fixed, both of which are 0.5 mm; the excitation coil 4 is electrically connected to a bipolar current source 9, the eddy current excitation coil 1 is electrically connected to a signal generator 8, the eddy current detection coil 2 is electrically connected to an integration and filtering circuit module 7, and the integration and filtering circuit module 7 is electrically connected to an industrial computer 6.

[0040] More specifically, the system includes: an excitation coil 4 wound around the U-shaped magnetic yoke 3; a ferromagnetic material 5 arranged toward the pole shoe direction of the U-shaped magnetic yoke 3; an eddy current excitation coil 1 and an eddy current detection coil 2 arranged between the U-shaped magnetic yoke 3 and the ferromagnetic material 5, the eddy current excitation coil 1 and the eddy current detection coil 2 being arranged side by side between the two pole shoes of the U-shaped magnetic yoke 3; a fixed distance between the eddy current excitation coil 1 and the eddy current detection coil 2 and the ferromagnetic material 5; a bipolar current source 9 electrically connected to the excitation coil 4; a signal generator 8 electrically connected to the eddy current excitation coil 1, and an integration and filtering circuit module 7 electrically connected to the eddy current detection coil 2, in this way, the magnetic Barkhausen noise generated by the ferromagnetic material 5 is modulated by the eddy current excitation coil 1 and the integration and filtering circuit module 7 to detect internal defects of the test piece at an optimal modulation frequency.

[0041] Preferably, the current of the bipolar current source 9 is in the range of 0 to 60A.

[0042] Preferably, the U-shaped magnetic yoke 3 is made of MnZn ferrite.

[0043] Preferably, the excitation frequency range of the eddy current excitation coil 1 is 1 kHz to 200 kHz.

[0044] Preferably, the eddy current excitation coil 1 and the eddy current detection coil 2 are arranged side by side with an interval of 0.5 mm.

[0045] Preferably, the eddy current excitation coil 1 and the eddy current detection coil 2 are both wound with enameled copper wire with a wire diameter of 0.08 mm, with 50 turns.

[0046] More preferably, the eddy current excitation coil 1 and the eddy current detection coil 2 have an outer diameter of 4 mm, an inner diameter of 3 mm, and a height of 1 mm.

[0047] like Figure 2 As shown, according to another aspect of the present invention, a detection method using the above-mentioned magnetic Barkhausen noise eddy current modulation is also provided, comprising the following steps:

[0048] S1, outputting a low-frequency sinusoidal alternating current through a bipolar current source 9 and loading it onto an excitation coil 4, and using a U-shaped magnetic yoke 3 to magnetize a ferromagnetic material 5, so that the ferromagnetic material 5 generates a magnetic Barkhausen noise reflecting the local magnetic flux density distortion information of the defect;

[0049] S2, the signal generator 8 outputs a sine wave and loads it onto the eddy current excitation coil 1, the eddy current detection coil 2 receives the electromagnetic field generated by the eddy current excitation coil 1 and induces the magnetic Barkhausen noise of the ferromagnetic material 5, and the induced voltage amplitude of the eddy current detection coil 2 is jointly determined by the magnetic field generated by the eddy current field under the eddy current detection coil 2 and the electromagnetic field generated by the eddy current excitation coil 1;

[0050] S3, fix the eddy current excitation coil 1 and the eddy current detection coil 2 above the ferromagnetic material, when the depth of the crack or thinning defect is different, the eddy current detection coil 2 obtains the change of the eddy current induced magnetic field, and uses the integration and filtering circuit module 7 to modulate the magnetic Barkhausen noise signal. The obtained eddy current signal reflecting the magnetic Barkhausen noise information is displayed on the industrial computer 6, so as to determine the defect depth;

[0051] S4. Linearly increase the frequency of the output voltage of the signal generator 8 from 0 Hz, and synchronously record the eddy current modulation signal displayed on the industrial computer 6. When the peak-to-peak value of the eddy current signal increases first and then decreases with the increase of the output voltage frequency of the signal generator 8, the frequency corresponding to the turning point of the voltage amplitude is the optimal frequency of the eddy current modulation. At this time, the detection accuracy of the magnetic Barkhausen noise eddy current modulation is the highest.

[0052] The present invention firstly adjusts the 0-60A bipolar current source to output a low-frequency sinusoidal alternating current to load onto the excitation coil 4 to excite a periodic magnetization field, so that the ferromagnetic material 5 generates a magnetic Barkhausen noise reflecting the local magnetic flux density distortion information of the defect, and then fixes the eddy current excitation coil 1 and the eddy current detection coil 2 above the ferromagnetic material, obtains the eddy current induced magnetic field change through the eddy current excitation coil 1 and the eddy current detection coil 2, detects the defect, and then linearly adjusts the magnitude of the output voltage frequency of the signal generator 8. When the peak-to-peak value of the eddy current signal first increases and then decreases with the increase of the voltage of the signal generator 8, the frequency corresponding to the turning point of the voltage amplitude is the optimal frequency of the eddy current modulation. At this time, the detection accuracy is the highest, and the accurate detection of deep defect signals is achieved.

[0053] The present invention fixes the distance between the eddy current excitation coil 1 and the eddy current detection coil 2 and the ferromagnetic material 5 to 0.5 mm, and linearly adjusts the magnitude of the output voltage frequency of the signal generator 8. When the eddy current signal intensity is maximum, the optimal eddy current modulation frequency is achieved, and a higher-precision eddy current signal can be obtained, thereby improving the accuracy of detection.

[0054] The present invention can measure the magnetic Barkhausen noise signal caused by deep defects under AC magnetization of ferromagnetic material 5, realize accurate detection of deep defect signals, use eddy current detection coil 2 to obtain detection signals, and has high reliability. The eddy current coil is used to detect the magnetic field strength, realize rapid adjustment of the optimal modulation frequency, and detect defects of the test piece at the optimal modulation frequency. At this time, the defect detection accuracy reaches the maximum.

[0055] The working principle of the present invention is as follows:

[0056] There are many spontaneous magnetization areas, i.e., magnetic domains, inside ferromagnetic materials. The boundary between adjacent magnetic domains is the domain wall. When the ferromagnetic material is in a magnetic neutral state, the macroscopic magnetization intensity of the material is zero due to the different magnetization directions of different magnetic domains. When it is subjected to an external magnetic field, magnetic domain rotation and domain wall displacement will occur in the direction of the external magnetic field. When the external magnetic field increases to a certain extent, it will present a magnetic saturation state. This process is called the magnetization process. When an AC magnetic field is applied, the magnetization process of the ferromagnetic material will form a closed curve, i.e., the hysteresis loop. In the intense magnetization stage, i.e., where the slope of the hysteresis loop is large, the curve shows a step-like jitter change rather than a smooth continuous curve. This is because the internal magnetic domains and domain walls of the ferromagnetic material will change dramatically under the action of the AC magnetic field. When a large number of adjacent magnetic domains produce friction, the domain wall will undergo a jump-like displacement, i.e., a Barkhausen jump occurs. The magnetic Barkhausen noise (MBN) signal is generated at the moment when the positive and negative changes of the magnetic field are the fastest. The sensor can be used to receive the signal released by the Barkhausen jump. The existence of internal defects in the steel plate affects the movement of the magnetic domain wall, which in turn affects the magnetic Barkhausen signal. Therefore, the internal defects of the steel plate can be detected by analyzing the magnetic Barkhausen signal with defect information.

[0057] An analysis is performed at any moment under AC magnetization. When there is a defect, a part of the magnetic flux lines pass over the deep defect of the ferromagnetic material 5, and a part of the magnetic flux lines leak into the air from the defect. When an alternating eddy current field is applied to the surface of the ferromagnetic material 5, the defect disturbs the surface eddy current, forming a secondary disturbed magnetic field; at the same time, the magnetic flux density disturbance in the material becomes the measurement source of the eddy current effect, which affects the eddy current excited by the excitation coil on the surface of the material, resulting in changes in the secondary magnetic field in the space outside the material. On the other hand, the sensor also receives leakage magnetic field information leaked into the air. According to Faraday's law of electromagnetic induction, the receiving coil can sense all changes in magnetic flux density, and it is reflected in the change of the coil induced voltage. When there is a deep defect, the magnetic flux density disturbance caused by the deep defect, due to the skin effect of the eddy current, is expressed as follows: Its penetration depth δ is limited, and the detectable depth of eddy current for defects is usually defined as 3δ. For defects with a depth greater than 3δ, although magnetic flux density distortion will occur on the side of the defect, eddy current disturbances cannot be formed inside the material. At the same time, the magnetic flux density disturbance in the area above the defect diffuses to the surface of the material and can be detected by the eddy current probe. Therefore, the signal mainly comes from the magnetic flux density disturbance reflecting the defect information and the disturbed magnetic field generated by the leakage magnetic field.

[0058] During detection, the low-frequency sinusoidal alternating current output by the bipolar current source 9 of 0 to 60A is loaded onto the excitation coil 4 to excite the alternating magnetization field, and the output size of the current source is adjusted to control the magnetization degree of the ferromagnetic test piece 5 in the effective magnetization area, so as to form a near-saturation magnetization area on the body surface. The signal generator 8 applies adjustable excitation to the eddy current excitation coil 1. The two detection coils are arranged side by side in space to measure the changes in the induced magnetic field in the flux density mutation zone. The magnetic field strength is detected by the eddy current coil to achieve rapid adjustment of the optimal modulation frequency, and detect defects in the test piece under the optimal modulation frequency state. At this time, the defect detection accuracy reaches the maximum.

[0059] The eddy current excitation coil 1 and the eddy current detection coil 2 are fixed above the ferromagnetic material 7. When the defect depth is different, the eddy current induced magnetic field changes are obtained. The magnitude of the output voltage frequency of the signal generator 8 is linearly adjusted. When the peak-to-peak value of the eddy current modulation signal increases first and then decreases with the increase of the voltage frequency of the signal generator 8, the frequency corresponding to the turning point of the voltage amplitude is the optimal frequency of the eddy current modulation. At this time, the detection accuracy of the magnetic Barkhausen noise eddy current modulation signal is the highest, and the accurate measurement of deep defects can be achieved.

[0060] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A magnetic Barkhausen noise eddy current modulation detection system, characterized in that: include: an excitation coil (4) wound around the U-shaped magnetic yoke (3); A ferromagnetic material (5) arranged in the direction of the pole shoe of the U-shaped magnetic yoke (3); An eddy current excitation coil (1) and an eddy current detection coil (2) are arranged between the U-shaped magnetic yoke (3) and the ferromagnetic material (5); the eddy current excitation coil (1) and the eddy current detection coil (2) are arranged side by side between two pole shoes of the U-shaped magnetic yoke (3); the distance between the eddy current excitation coil (1) and the eddy current detection coil (2) and the ferromagnetic material (5) is fixed; a bipolar current source (9) electrically connected to the excitation coil (4); a signal generator (8) electrically connected to the eddy current excitation coil (1), and an integration and filtering circuit module (7) electrically connected to the eddy current detection coil (2), In this way, the magnetic Barkhausen noise generated by the ferromagnetic material (5) is modulated by the eddy current excitation coil (1), and an eddy current signal reflecting the magnetic Barkhausen noise information is obtained at an optimal modulation frequency to detect internal defects of the test piece.

2. The eddy current modulation detection system of magnetic Barkhausen noise according to claim 1, characterized in that: It also includes an industrial computer (6) connected to the integration and filtering circuit module (7), and the industrial computer (6) is used to display the eddy current signal reflecting the magnetic Barkhausen noise information modulated by the integration and filtering circuit module (7), so as to determine the defect depth.

3. The eddy current modulation detection system of magnetic Barkhausen noise according to claim 1, characterized in that: The current of the bipolar current source (9) ranges from 0 to 60A.

4. The eddy current modulation detection system of magnetic Barkhausen noise according to claim 1, characterized in that: The excitation frequency range of the eddy current excitation coil (1) is 1 kHz to 200 kHz.

5. The eddy current modulation detection system of magnetic Barkhausen noise according to claim 1, characterized in that: The U-shaped magnetic yoke material (5) is MnZn ferrite.

6. The eddy current modulation detection system of magnetic Barkhausen noise according to claim 1, characterized in that: The eddy current excitation coil (1) and the eddy current detection coil (2) are arranged side by side with an interval of 0.5 mm.

7. The eddy current modulation detection system of magnetic Barkhausen noise according to claim 1, characterized in that: The eddy current excitation coil (1) and the eddy current detection coil (2) are both wound from enameled copper wire with a wire diameter of 0.08 mm, and the number of turns is 50.

8. The eddy current modulation detection system of magnetic Barkhausen noise according to claim 1, characterized in that: The eddy current excitation coil (1) and the eddy current detection coil (2) both have an outer diameter of 4 mm, an inner diameter of 3 mm, and a height of 1 mm.

9. A method for detecting eddy current modulation of magnetic Barkhausen noise, characterized in that: The following steps are involved: Step 1: A low-frequency sinusoidal alternating current is applied to the excitation coil (4) to magnetize the ferromagnetic material (5) using the U-shaped magnetic yoke (3), so that the ferromagnetic material (5) generates magnetic Barkhausen noise reflecting local magnetic flux density distortion information of the defect; Step 2: A high-frequency sinusoidal current is applied to the eddy current excitation coil (1); the eddy current detection coil (2) receives the electromagnetic field generated by the eddy current excitation coil (1) and induces the magnetic Barkhausen noise of the ferromagnetic material (5); the eddy current field of the eddy current detection coil (2) and the electromagnetic field generated by the eddy current excitation coil (1) jointly determine the induced voltage of the eddy current detection coil (2); Step 3, fixing the eddy current excitation coil (1) and the eddy current detection coil (2) above the ferromagnetic material (5), when the defect depth is different, the eddy current detection coil (2) obtains the change of the induced magnetic field, and uses the integration and filtering circuit module (7) to modulate the magnetic Barkhausen noise signal to obtain the eddy current signal reflecting the magnetic Barkhausen noise information, so as to determine the defect depth; Step 4: linearly increase the frequency of the voltage applied to the eddy current excitation coil (1) from 0 Hz, and detect internal defects of the test piece at the optimal modulation frequency according to the eddy current modulation signal.

10. The eddy current modulation detection method of magnetic Barkhausen noise according to claim 9, characterized in that: In step 4, when the peak-to-peak value of the eddy current modulation signal increases first and then decreases as the output voltage frequency of the signal generator (8) increases, the frequency corresponding to the turning point of the voltage amplitude is the optimal frequency of the eddy current modulation, and at this time, the magnetic Barkhausen noise eddy current modulation detection accuracy is the highest.

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