Ferromagnet residual magnetism measurement method based on magnetic Barkhausen noise signal

Abstract

The invention discloses a residual magnetism measurement method of a ferromagnetic material based on a magnetic Barkhausen noise signal, and belongs to the technical field of electromagnetic parameter measurement. A magnetic Barkhausen noise signal serves as an electromagnetic nondestructive testing signal with huge development potential and has unique advantages in the aspects of detection and evaluation of ferromagnetic metal materials, and the signal generation mechanism of the magnetic Barkhausen noise signal is similar to the generation mechanism of residual magnetism and is related to irreversible magnetic domain rotation and irreversible magnetic domain wall movement; therefore, through two theoretical model formulas of a magnetic Barkhausen noise signal stress detection model based on a J-A magnetization theory and a magnetomechanical model of residual magnetism and stress, a physical model relational expression of a magnetic Barkhausen noise voltage signal peak value and residual magnetization intensity is established by taking stress existing in a ferromagnetic material as an intermediate medium; on the premise that the geomagnetic field can be ignored, the residual magnetism in the ferromagnetic material can be calculated through the measured magnetic Barkhausen noise voltage peak signal according to the constitutive relation, and the method is easy and convenient to operate, reliable in result and wide in applicability.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic parameter measurement, and in particular to a method for measuring residual magnetism of a ferromagnetic body based on a magnetic Barkhausen noise signal. Background Art

[0002] When the ferromagnetic material is magnetized and the external magnetic field is removed, the magnetic domains in the material will not return to the original random arrangement state, and the ferromagnetic material will still show a certain degree of magnetism to the outside. This phenomenon that the change in magnetic induction intensity lags behind the change in magnetic field intensity is called the hysteresis characteristic of the ferromagnetic material. Due to the hysteresis characteristic of the ferromagnetic material, when the external magnetic field intensity is 0, the magnetic induction intensity of the material is not 0, and the corresponding magnetic induction intensity is called residual magnetic induction intensity, or remanence for short. Since most of the power equipment in the power system is made of ferromagnetic materials, such as transformers, reactors, current transformers and other inductive equipment with iron cores. When these inductive equipment are powered off, remanence will appear in the internal iron core. The presence of remanence will change the starting working point of the transformer on the excitation curve, thereby accelerating the magnetization saturation of the iron core, resulting in the phenomenon of excitation inrush current when the no-load switch is closed. The overcurrent value generated by the excitation inrush current can be as high as 6 to 8 times the rated current value. This will endanger the mechanical stability and insulation strength of the transformer winding, and seriously affect the safety and stability of the transformer in power grid applications. In addition, residual magnetism can also cause errors in current transformers, thereby affecting their metering and protection performance, resulting in deviations in electricity metering and trade settlement.

[0003] In order to avoid damage to the transformer windings and their insulation in the power system and the situation where the residual magnetism of the current transformer affects the accuracy of the power system measurement, it is necessary to study the measurement of the residual magnetism of ferromagnetic materials so as to measure the residual magnetism and demagnetize the inductive equipment with iron core. Although some residual magnetism detection methods have been proposed, the effects of some of the detection measures proposed so far are not very ideal due to factors such as low measurement accuracy or complex measurement systems.

[0004] For example, CN102645640A discloses a measurement structure for measuring the residual magnetism of ferromagnetic components by the direct current method, which mainly includes a direct current power supply, a control switch, an integrator, a winding of the measured component and a direct current voltage measuring device. The invention applies a direct current voltage with changing polarity to the winding to make the iron core reach the saturation point in the positive and negative directions respectively, and records the voltage and current waveforms of the whole process. The partial saturation hysteresis loop of the iron core is drawn, and the residual magnetic flux and residual magnetic coefficient of the iron core are calculated based on the obtained hysteresis loop. However, the calculation of the magnetic flux by the inventive method is obtained by integrating the collected voltage signal, but the collected voltage signal inevitably has noise, drift, etc., and the simple integration method will infinitely accumulate such errors, resulting in low accuracy of the measurement results.

[0005] For example, CN111638478A discloses a method for measuring the residual magnetism of a transformer core based on a time constant. The method determines the direction of the residual magnetic flux density by comparing the magnitudes of the positive and negative time constants generated when applying positive and negative excitations; then establishes an empirical relationship between the residual magnetic flux density and the difference between the positive and negative time constants to calculate the magnitude of the residual magnetic flux density. However, due to the different coefficients of the empirical formula for the residual magnetism and the time constant difference under different excitations, the empirical formula is not unique, and the empirical formula for residual magnetism calculation obtained by data fitting lacks physical meaning.

[0006] For example, the article "Estimation of Residual Magnetism of Transformer Core" in the 2nd issue of "Power System Technology" in 2011 uses the voltage and current data detected on the primary side of the transformer after the transformer is closed without load to find the saturation moment of the transformer core and estimate the residual magnetism in the core after the transformer is opened. However, this method needs to record the time for the core to reach saturation during measurement, and the excitation surge current generated when the core is saturated will cause harm to the equipment, and demagnetization is required after the measurement. The article "Research on Residual Magnetism Measurement Method of Power Transformer" in the 15th issue of "Power System Protection and Control" in 2019 analyzes the generation mechanism of excitation surge current of power transformer and obtains the peak expression of excitation surge current of transformer, and then obtains that the surge current peak is uniquely determined by residual magnetism, so the residual magnetism can be inferred from the closing angle of voltage and the first peak of excitation surge current, but this method cannot calculate the residual magnetism value in the core before closing, and cannot help suppress the generation of excitation surge current when the transformer is closed, and the excitation surge current generated by measurement will cause harm to the equipment. The article "Evaluation and Experimental Verification of Residual Magnetism of Power Transformers Based on External DC Excitation" in the 10th issue of "Power System Technology" in 2022 is based on the measurement method of real-time flux tracking. An external current excitation of known magnitude is applied to the transformer winding to magnetize the core, and the magnitude and direction of the residual magnetism are obtained by recording the flux changes in the process. However, this method uses the measurement method of real-time flux tracking, which has high requirements on the performance of the measuring instrument and requires reversibility of the external excitation magnetization process, so it is limited to the residual magnetism measurement of soft magnetic materials.

[0007] As an electromagnetic nondestructive testing technology with great development potential, magnetic Barkhausen noise technology has unique advantages in the detection and evaluation of ferromagnetic metal materials, such as sensitivity to physical signal changes in materials, obvious signal characteristics, fast scanning, etc. Considering that the generation mechanism of magnetic Barkhausen noise signals is similar to the generation mechanism of remanent magnetism, both of which are related to irreversible magnetic domain rotation and irreversible magnetic domain wall movement, the application of magnetic Barkhausen noise detection technology to remanent magnetism measurement has great development potential and application prospects. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a method for measuring the residual magnetism of a ferromagnetic body based on a magnetic Barkhausen noise signal, so as to solve the problems of low measurement accuracy and complex measurement system of the existing method for measuring the residual magnetism of a ferromagnetic body.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is a method for measuring the residual magnetism of ferromagnetic materials based on a magnetic Barkhausen noise signal, comprising the following steps: Step 1: Construct a stress detection model of magnetic Barkhausen noise signal based on JA magnetization theory, and obtain the expression of the relationship between the magnetic Barkhausen noise voltage peak signal and the applied stress of ferromagnetic material; Step 2: Apply the magnetomechanical model to obtain the magnetomechanical model relationship expression between remanence and stress, with the applied stress of ferromagnetic material as input variable and the residual magnetization intensity as output; Step 3: Solve the stress detection model relationship expression of the magnetic Barkhausen noise signal based on the JA magnetization theory and the magnetomechanical model relationship expression of the residual magnetism and stress described in Step 1 and Step 2, and then derive the theoretical model relationship expression of the magnetic Barkhausen noise voltage signal and the residual magnetization intensity; Step 4: According to the mathematical model expression of the magnetic Barkhausen noise signal, a simulation model of the magnetic Barkhausen noise signal is established. By presetting different residual magnetization intensities in the simulation model, it is used to verify the correctness of the theoretical model expression of the residual magnetization measurement proposed.

[0010] In a preferred solution, the stress detection model of the magnetic Barkhausen noise signal based on the JA magnetization theory in Step 1 is obtained specifically in the following manner: Step 1.1: When there is no external magnetic field and only stress exists, that is, H =0, σ≠0, the ferromagnetic material satisfies the following conditions when there is no hysteresis under stress: (1) In the formula, H is the strength of the external magnetic field, is the tensile stress on the material, is the differential of the maximum magnetic susceptibility, is the saturation magnetization, is the magnetic domain wall density in the material; is the coupling coefficient of the interaction between adjacent magnetic domains, is the second-order coefficient, is the magnetic permeability of vacuum.

[0011] Step 1.2: None H When the magnetic Barkhausen signal is and The strength is directly proportional to each other, and we get: (2) In the formula, is the constant coefficient of proportionality, is the peak value of the magnetic Barkhausen voltage signal when there is stress, is the peak value of the magnetic Barkhausen voltage signal when there is no stress.

[0012] In a preferred solution, the magnetomechanical model of remanence and stress in Step 2 is obtained specifically in the following manner: Step 2.1: Based on the magnetomechanical model theory, the coercive force of ferromagnetic materials in a stable state can approximately satisfy: (3) In the formula, is the coercive force; is a constant coefficient, and its maximum value is 1; is the magnetostriction; Step 2.2: Combining the critical magnetic field strength of ferromagnetic materials and the relationship between the residual magnetization and saturation magnetization of the disordered uniaxial anisotropic micro-grains in cubic crystals, we can get: (4) In the formula, is the residual magnetization, is the demagnetization factor of the long axis of the magnetic domain, is the demagnetization factor of the short axis of the magnetic domain, is the constant factor of the grain averaging effect.

[0013] In a preferred solution, the theoretical model of the magnetic Barkhausen noise voltage signal and the residual magnetization in Step 3 is obtained specifically in the following manner: Combining the stress detection model relationship of the magnetic Barkhausen noise signal of the above JA magnetization theory and the magnetomechanical model relationship between residual magnetism and stress, taking stress as the intermediate physical quantity, we can get: (5) Thus, the physical model relationship between the magnetic Barkhausen noise voltage peak signal and the residual magnetization intensity is obtained, where: is the peak value of the magnetic Barkhausen voltage signal when there is residual magnetism, is the peak value of the magnetic Barkhausen voltage signal when there is no residual magnetism.

[0014] In the preferred scheme, the residual magnetization intensity can be calculated by obtaining the physical model relationship between the magnetic Barkhausen noise voltage peak signal and the residual magnetization intensity through the measured magnetic Barkhausen voltage signal, and the residual magnetization value in the ferromagnetic material can be obtained by using the constitutive relationship between the magnetic induction intensity and the magnetization intensity.

[0015] The present invention provides a method for measuring the residual magnetism of a ferromagnetic body based on a magnetic Barkhausen noise signal, which has the following beneficial effects: 1. The present invention solves the problems of low measurement accuracy and complex measurement system of the existing ferromagnetic remanence measurement method; 2. The present invention uses the stress on ferromagnetic materials as the intermediate medium for research, constructs the relationship between the magnetic Barkhausen signal and the residual magnetism, and provides a new method and idea for the measurement and evaluation of the residual magnetism of ferromagnetic materials; 3. The ferromagnetic material remanence measurement relationship provided by the present invention has a clear physical meaning, the measurement principle is simple and clear, and the obtained ferromagnetic material remanence measurement result has high credibility and accuracy; 4. The method of the present invention is generally applicable and can be widely used in the measurement and calculation of the residual magnetism of ferromagnetic bodies in power equipment, which plays a significant role in suppressing and eliminating the influence of residual magnetism in power equipment; 5. The present invention applies the electromagnetic nondestructive testing technology of magnetic Barkhausen noise (MBN) signal to the measurement of residual magnetism of ferromagnetic materials for the first time. MBN signal is a signal with great development potential. It is sensitive to the change of physical signals in materials, has obvious signal characteristics and fast scanning. These characteristics make it have unique advantages in the application of residual magnetism measurement. 6. The present invention combines JA magnetization theory and magnetomechanics model, takes stress as the intermediate medium, and innovatively constructs the physical model relationship between MBN signal and residual magnetism. The proposal of this theoretical model provides a new theoretical basis for residual magnetism measurement, which is different from the previous method that relies on empirical formulas or complex experimental measurements; 7. The measurement method of the present invention is easy to operate. It only requires placing the designated MBN signal detection sensor on the surface of the material, avoiding the inconvenience of winding coils due to the complex shape of ferromagnetic objects. This non-contact measurement method greatly improves the convenience and flexibility of measurement; 8. This invention has achieved a breakthrough in theory. By deeply analyzing the similarity between the generation mechanism of MBN signal and the generation mechanism of residual magnetism, it innovatively proposed a residual magnetism measurement method based on MBN signal and constructed a corresponding theoretical model. This theoretical innovation has brought new perspectives and thinking to the field of residual magnetism measurement; 9. The present invention successfully integrates the JA magnetization theory and the magnetomechanical model into the residual magnetism measurement. By solving the relationship expression of the two models together, the theoretical model relationship between the MBN signal and the residual magnetism is derived. The application of this technology integration not only improves the accuracy of the measurement, but also broadens the application scope of the theoretical model. 10. The measurement method of the present invention has a wide range of practical application value and can be applied to the measurement and evaluation of the residual magnetism of various ferromagnetic equipment in the power system. By accurately measuring the residual magnetism, the influence of the residual magnetism on the safety and stability of the equipment can be effectively avoided, and the operating efficiency and reliability of the power system can be improved. The creativity of this practical application has contributed to the technological progress and development of the power industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and implementation examples: Figure 1 This is a structural schematic diagram of a magnetic Barkhausen noise signal detection sensor according to embodiment 3 of the present invention; Figure 2 This is a schematic block diagram of the operation flow of Embodiment 3 of the present invention; Figure 3 A magnetic Barkhausen noise signal diagram without residual magnetization intensity under an excitation frequency of 5 Hz in an excitation cycle established in Example 3 of the present invention; Figure 4 A magnetic Barkhausen noise signal diagram with residual magnetization intensity under an excitation frequency of 5 Hz in an excitation cycle established in Example 3 of the present invention; In the figure: ferromagnetic sample 1, U-shaped magnetic yoke 2, AC excitation power supply 3, excitation excitation coil 4, pickup coil 5, manganese-zinc ferrite 6. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below in conjunction with the embodiments and drawings: Example 1 A method for measuring the residual magnetism of a ferromagnetic material based on a magnetic Barkhausen noise signal comprises the following steps: Step 1: Construct a stress detection model of magnetic Barkhausen noise signal based on JA magnetization theory, and obtain the expression of the relationship between the magnetic Barkhausen noise voltage peak signal and the applied stress of ferromagnetic material; Step 2: Apply the magnetomechanical model to obtain the magnetomechanical model relationship expression between remanence and stress, with the applied stress of ferromagnetic material as input variable and the residual magnetization intensity as output; Step 3: Solve the stress detection model relationship expression of the magnetic Barkhausen noise signal based on the JA magnetization theory and the magnetomechanical model relationship expression of the residual magnetism and stress described in Step 1 and Step 2, and then derive the theoretical model relationship expression of the magnetic Barkhausen noise voltage signal and the residual magnetization intensity; Step 4: According to the mathematical model expression of the magnetic Barkhausen noise signal, a simulation model of the magnetic Barkhausen noise signal is established. By presetting different residual magnetization intensities in the simulation model, it is used to verify the correctness of the theoretical model expression of the residual magnetization measurement proposed.

[0018] In this embodiment, the stress detection model of the magnetic Barkhausen noise signal based on the JA magnetization theory in Step 1 is obtained in the following manner: Step 1.1: When there is no external magnetic field and only stress exists, that is, =0, σ≠0, the ferromagnetic material satisfies the following conditions when there is no hysteresis under stress: (1) In the formula, is the strength of the external magnetic field, is the tensile stress on the material, is the differential of the maximum magnetic susceptibility, is the saturation magnetization, is the magnetic domain wall density in the material; is the coupling coefficient of the interaction between adjacent magnetic domains, is the second-order coefficient, is the magnetic permeability of vacuum.

[0019] Step 1.2: None When the magnetic Barkhausen signal is and The strength is directly proportional to each other, and we get: (2) In the formula, is the constant coefficient of proportionality, is the peak value of the magnetic Barkhausen voltage signal when there is stress, is the peak value of the magnetic Barkhausen voltage signal when there is no stress.

[0020] Furthermore, the magnetomechanical model of remanence and stress in Step 2 is obtained in the following way: Step 2.1: Based on the magnetomechanical model theory, the coercive force of ferromagnetic materials in a stable state can approximately satisfy: (3) In the formula, is the coercive force; is a constant coefficient, and its maximum value is 1; is the magnetostriction; Step 2.2: Combining the critical magnetic field strength of ferromagnetic materials and the relationship between the residual magnetization and saturation magnetization of the disordered uniaxial anisotropic micro-grains in cubic crystals, we can get: (4) In the formula, is the residual magnetization, is the demagnetization factor of the long axis of the magnetic domain, is the demagnetization factor of the short axis of the magnetic domain, is the constant factor of the grain averaging effect.

[0021] Furthermore, the theoretical model of the magnetic Barkhausen noise voltage signal and the residual magnetization intensity in Step 3 is obtained in the following way: Combining the stress detection model relationship of the magnetic Barkhausen noise signal of the above JA magnetization theory and the magnetomechanical model relationship between residual magnetism and stress, taking stress as the intermediate physical quantity, we can get: (5) Thus, the physical model relationship between the magnetic Barkhausen noise voltage peak signal and the residual magnetization intensity is obtained, where: is the peak value of the magnetic Barkhausen voltage signal when there is residual magnetism, is the peak value of the magnetic Barkhausen voltage signal when there is no residual magnetism.

[0022] Furthermore, by obtaining the physical model relationship between the magnetic Barkhausen noise voltage peak signal and the residual magnetization intensity, the residual magnetization intensity can be calculated using the measured magnetic Barkhausen voltage signal, and the residual magnetization value in the ferromagnetic material can be obtained using the constitutive relationship between the magnetic induction intensity and the magnetization intensity.

[0023] Example 2 In another preferred embodiment, based on the above embodiment 1, a method for measuring residual magnetism of a ferromagnetic body based on a magnetic Barkhausen noise signal of the present invention comprises the following steps: Step 1: Construct a stress detection model of magnetic Barkhausen noise signal based on JA magnetization theory, and obtain the expression of the relationship between the magnetic Barkhausen noise voltage peak signal and the applied stress of ferromagnetic material, including: Step 1.1: In the elastic stage of the material, constant external stress σ The effect on the material can be regarded as a stress equivalent magnetic field , the magnetic field strength generated by stress Magnetoelasticity , magnetization intensity The relationship between them is: (6).

[0024] Step 1.2: For isotropic crystals with the same magnetostriction coefficient, the stress energy generated by stress is: (7) In the formula, is the magnetostriction coefficient; is the angle between the direction of the applied stress and the magnetic moment of the material; is the Poisson’s ratio of the material.

[0025] Step 1.3: When the magnetization degree has not reached saturation, the magnetization intensity M Relative to the saturation magnetization Very small, the magnetostriction coefficient when the material is not magnetized saturated can be approximately expressed as: (8) In the formula, is the second-order coefficient.

[0026] Step 1.4: When the material is subjected to unidirectional stress only, the magnetic domain magnetization vector is consistent with the stress direction, that is, =0, then we can get: (9).

[0027] Step 1.5: Improvement of Langevin paramagnetic theory based on JA model theory, magnetization intensity with and without hysteresis effect for: (10) In the formula, is the saturation magnetization; is the equivalent magnetic field; is the external magnetic field strength; is the magnetic domain wall density in the material; is the coupling coefficient of the interaction between adjacent magnetic domains.

[0028] Step 1.6: According to the hyperbolic cotangent function exist x = 0, we can get the Taylor series expansion formula: (11) Combining the above results, we can further obtain: (12).

[0029] Step 1.7: The maximum magnetic susceptibility of the material at this time is: (13).

[0030] Step 1.8: When there is no external magnetic field and only stress exists, that is, H =0, σ ≠0, the ferromagnetic material satisfies the following conditions when there is no hysteresis under stress: (1) In the formula, H is the strength of the external magnetic field, is the tensile stress on the material, is the differential of the maximum magnetic susceptibility, is the saturation magnetization, is the magnetic domain wall density in the material; is the coupling coefficient of the interaction between adjacent magnetic domains, is the second-order coefficient, is the magnetic permeability of vacuum.

[0031] Step 1.9: From this we can further deduce: (14).

[0032] Step 1.10: None H When the magnetic Barkhausen signal is and The strength is directly proportional to each other, and we get: (2) In the formula, is the constant coefficient of proportionality, is the peak value of the magnetic Barkhausen voltage signal when there is stress, is the peak value of the magnetic Barkhausen voltage signal when there is no stress.

[0033] Step 2: Apply the magnetomechanical model to obtain the magnetomechanical model relationship expression between remanence and stress, with the applied stress of ferromagnetic material as input variable and the residual magnetization intensity as output; including: Step 2.1: Stress and material properties determine the magnitude of the coercive force. The critical magnetic field is also determined by stress and material properties. H C Critical magnetic field H 0, the coercive force can be expressed as: (15) In the formula, p is a constant coefficient, and its maximum value is 1.

[0034] Step 2.2: Due to the different stress distribution of each grain of the polycrystalline, each part The size of the stable state Substituting into formula (15), we get It can be approximately expressed as: (16) In the formula, is the magnetostriction; For stress.

[0035] Step 2.3: Imagine the magnetic domain as a long ellipsoid with the major and minor axes being long and short respectively. a and b ,and a > b , if the external magnetic field H along a The axial direction causes the magnetic domain to rotate and the magnetic moment to deviate a The angle of the axis is θ , then the magnetic field energy is: (17).

[0036] Step 2.4: Since the magnetic moment is a and b Two axes have and Two components, let a Axis and b The demagnetization factors of the axes are and , due to the demagnetization field , then the demagnetization energy can be obtained as: (18).

[0037] Step 2.5: , , so the total energy of the magnetic domain can be expressed as: (19).

[0038] Step 2.6: To determine the stable state, we can set: (20) The solution is: (twenty one).

[0039] Step 2.7: Solve the second-order derivative of equation (20) to obtain the magnetic domain equilibrium condition of stress: (twenty two).

[0040] Step 2.8: Critical Magnetic Field exist θ The critical angle satisfies equations (21) and (22) at the same time. Dividing equations (21) and (22) yields , so we can conclude θ =0, the critical magnetic field strength is obtained as: (twenty three).

[0041] Step 2.9: For a polycrystal, the long axis orientations of each grain are different, and we can get: (twenty four) In the formula, Factors can be obtained using average effects.

[0042] Step 2.10: For cubic crystals, the residual magnetization intensity of the disordered uniaxial anisotropic micro-grains It can be calculated from the spherical coordinates: (25).

[0043] Step 2.11: Substituting equation (24) and equation (25) into equation (16), the relationship between remanence and stress is: (26).

[0044] Step 3: Establish the theoretical model relationship expression between the magnetic Barkhausen noise voltage signal and the residual magnetization intensity: Combining the stress detection model relationship of the magnetic Barkhausen noise signal of the above JA magnetization theory and the magnetomechanical model relationship between residual magnetism and stress, taking stress as the intermediate physical quantity, we can get: (5) Thus, the physical model relationship between the magnetic Barkhausen noise voltage peak signal and the residual magnetization intensity is obtained, where: is the peak value of the magnetic Barkhausen voltage signal when there is residual magnetism, is the peak value of the magnetic Barkhausen voltage signal when there is no residual magnetism.

[0045] Step 4: For the measurement of a given material, the coefficient before the magnetic Barkhausen voltage in the formula is a constant, which can be calculated for convenience as , then the above physical model relationship becomes: (27) From the above relationship, the residual magnetization intensity can be calculated by measuring the magnetic Barkhausen voltage signal, and then the residual magnetization value in the ferromagnetic material can be obtained by using the constitutive relationship between the magnetic induction intensity and the magnetization intensity.

[0046] Example 3 In another preferred embodiment, based on the above embodiment 1, Figures 1 to 4 As shown, the provided ferromagnetic material residual magnetism measurement method system and its implementation process are further explained below in conjunction with the accompanying drawings.

[0047] Figure 1Schematic diagram of a sensor used to measure the magnetic Barkhausen noise signal of ferromagnetic materials. The sensor consists of two major parts: a U-shaped excitation yoke 2 and a pickup coil 5. The ferromagnetic body is excited by an AC excitation power supply 3 through an excitation coil 4. The pickup coil 5 is wound around a cylindrical manganese-zinc ferrite 6 to effectively collect and amplify the magnetic Barkhausen signal. The sensor is then placed on the surface of a ferromagnetic sample 1 to collect the magnetic Barkhausen noise voltage signals of the ferromagnetic sample 1 with and without residual magnetism.

[0048] use Figure 2 The measurement process shown in the figure is to determine the constant coefficient in the model formula by presetting the residual magnetization intensity, and substitute the peak value of the obtained magnetic Barkhausen noise voltage signal into the model formula to obtain the residual magnetization intensity. , the residual magnetic induction intensity in the ferromagnetic material can be calculated.

[0049] use Figure 3 When there is no residual magnetization in the magnetic Barkhausen noise voltage signal, the peak value can be calculated from the theoretical formula , the result is 152.439.

[0050] use Figure 4 The peak value of the magnetic Barkhausen noise voltage signal when there is residual magnetization is determined by using the method of undetermined coefficients to determine the constant in the relationship c , the result is -1.21E-06.

[0051] Finally, the mathematical expression for calculating the residual magnetization can be obtained: (28).

[0052] The obtained theoretical formula was used to calculate 11 sets of preset residual magnetism, and the relative error between the residual magnetization intensity obtained by the theoretical formula and the preset residual magnetization intensity was calculated, as shown in the following table: Table 1 Relative error at different residual magnetization intensities

[0053] It can be seen from Table 1 that the residual magnetization intensity calculated in the simulation according to the theoretical formula is close to the preset residual magnetization intensity value, and the maximum relative error does not exceed 5%. In addition, the larger the residual magnetization intensity, the more accurate the calculated value.

[0054] In summary, the present invention provides a method for measuring the residual magnetism of ferromagnets based on magnetic Barkhausen noise signals, which solves the problems of low measurement accuracy and complex measurement system of existing ferromagnetic residual magnetism measurement methods, and ensures the accuracy and reliability of residual magnetism measurement results through theoretical model derivation and simulation verification; the method only needs to place the magnetic Barkhausen noise signal detection sensor on the surface of the material to perform measurement, avoiding the problem of inconvenient operation such as complex winding coils; the method can be widely used in the measurement and calculation of the residual magnetism of ferromagnets in power equipment, which plays a significant role in suppressing and eliminating the influence of residual magnetism; the residual magnetism measurement relationship proposed in the present invention has a clear physical meaning, and provides a new method and idea for the residual magnetism measurement and evaluation of ferromagnetic materials; at the same time, the promotion and application of this technology will further promote the safe and stable operation of power equipment, reduce faults and accidents caused by residual magnetism, and improve the reliability and economy of the power system; this method not only provides a new idea for the rapid and non-contact measurement of the residual magnetism of ferromagnetic materials, but also opens up a new path for the development of electromagnetic non-destructive testing technology, and is expected to play an important role in aerospace, automobile manufacturing and other fields.

Claims

1. A method for measuring the residual magnetism of ferromagnetic materials based on a magnetic Barkhausen noise signal, characterized in that: The method comprises the following steps: Step 1: Construct a stress detection model of magnetic Barkhausen noise signal based on JA magnetization theory, and obtain the expression of the relationship between the magnetic Barkhausen noise voltage peak signal and the applied stress of ferromagnetic material; Step 2: Apply the magnetomechanical model to obtain the magnetomechanical model relationship expression between remanence and stress, with the applied stress of ferromagnetic material as input variable and the residual magnetization intensity as output; Step 3: Solve the stress detection model relationship expression of the magnetic Barkhausen noise signal based on the JA magnetization theory and the magnetomechanical model relationship expression of the residual magnetism and stress described in Step 1 and Step 2, and then derive the theoretical model relationship expression of the magnetic Barkhausen noise voltage signal and the residual magnetization intensity; Step 4: According to the mathematical model expression of the magnetic Barkhausen noise signal, a simulation model of the magnetic Barkhausen noise signal is established. By presetting different residual magnetization intensities in the simulation model, it is used to verify the correctness of the theoretical model expression of the residual magnetization measurement proposed.

2. The method for measuring residual magnetism of ferromagnetic materials based on magnetic Barkhausen noise signals according to claim 1, characterized in that: The stress detection model of the magnetic Barkhausen noise signal based on the JA magnetization theory in Step 1 is obtained in the following way: Step 1.1: When there is no external magnetic field and only stress exists, that is, H =0, σ≠0, the ferromagnetic material satisfies the following conditions when there is no hysteresis under stress: （1） In the formula, H is the strength of the external magnetic field, is the tensile stress on the material, is the differential of the maximum magnetic susceptibility, is the saturation magnetization, is the magnetic domain wall density in the material; is the coupling coefficient of the interaction between adjacent magnetic domains, is the second-order coefficient, is the vacuum permeability; Step 1.2: None H When the magnetic Barkhausen signal is and The strength is directly proportional to each other, and we get: （2） In the formula, is the constant coefficient of proportionality, is the peak value of the magnetic Barkhausen voltage signal when there is stress, is the peak value of the magnetic Barkhausen voltage signal when there is no stress.

3. The method for measuring residual magnetism of ferromagnetic materials based on magnetic Barkhausen noise signals according to claim 1, characterized in that: The magnetomechanical model of remanence and stress in Step 2 is obtained specifically in the following way: Step 2.1: Based on the magnetomechanical model theory, the coercive force of ferromagnetic materials in a stable state can approximately satisfy: （3） In the formula, is the coercive force; is a constant coefficient, and its maximum value is 1; is the magnetostriction; Step 2.2: Combining the critical magnetic field strength of ferromagnetic materials and the relationship between the residual magnetization and saturation magnetization of the disordered uniaxial anisotropic micro-grains in cubic crystals, we can get: （4） In the formula, is the residual magnetization, is the demagnetization factor of the long axis of the magnetic domain, is the demagnetization factor of the short axis of the magnetic domain, is the constant factor of the grain averaging effect.

4. The method for measuring residual magnetism of ferromagnetic materials based on magnetic Barkhausen noise signals according to claim 1, characterized in that: The theoretical model of the magnetic Barkhausen noise voltage signal and the residual magnetization intensity in Step 3 is obtained in the following way: Combining the stress detection model relationship of the magnetic Barkhausen noise signal of the above JA magnetization theory and the magnetomechanical model relationship between residual magnetism and stress, taking stress as the intermediate physical quantity, we can get: （5） Thus, the physical model relationship between the magnetic Barkhausen noise voltage peak signal and the residual magnetization intensity is obtained, where: is the peak value of the magnetic Barkhausen voltage signal when there is residual magnetism, is the peak value of the magnetic Barkhausen voltage signal when there is no residual magnetism.

5. The method for measuring residual magnetism of ferromagnetic materials based on magnetic Barkhausen noise signals according to claim 4, characterized in that: By obtaining the physical model relationship between the magnetic Barkhausen noise voltage peak signal and the residual magnetization intensity, the residual magnetization intensity can be calculated using the measured magnetic Barkhausen voltage signal, and the residual magnetization value in the ferromagnetic material can be obtained using the constitutive relationship between the magnetic induction intensity and the magnetization intensity.

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