Multi-magnetization direction selection optimization method and device based on magnetoacoustic emission stress detection

Abstract

The invention discloses a multi-magnetization direction selection optimization method and device based on magnetoacoustic emission stress detection, and the method comprises the steps: applying excitation to two pairs of orthogonal Helmholtz coils based on two excitation sources with the same frequency but different amplitudes, so as to generate an alternating magnetic field to magnetize a to-be-tested test piece; the method comprises the following steps: acquiring a magnetoacoustic emission signal of a test piece to be tested, processing the magnetoacoustic emission signal to obtain an enhanced magnetoacoustic emission signal, carrying out Wiener filtering processing on the magnetoacoustic emission signal under a stress group corresponding to each magnetization direction, extracting an envelope line, extracting a plurality of peak signals from the envelope line, and calculating an average peak value of the plurality of peak signals. A multidirectional equal dynamic adjustment magnetization mode is adopted, magnetic fields in different directions are generated by using an orthogonal coil, the optimal magnetization direction is selected by comparing stress changes, multidimensional stress components can be captured, the detection sensitivity and accuracy are improved, information omission is avoided, and the method is suitable for complex stress fields.

Description

Technical Field

[0001] The present invention relates to the technical field of nondestructive testing, and in particular, to a method and device for optimizing the selection of multiple magnetization directions based on magnetoacoustic emission stress detection. Background Art

[0002] With the rapid development of the domestic economy and industry, the quality standards and requirements for industrial products are increasing day by day. The nondestructive testing technology of ferromagnetic materials is becoming increasingly crucial for the booming industry. Cracks and other damages in engineering structures are the direct causes of catastrophic accidents. By using nondestructive testing to give early warnings of engineering structure damages and taking remedial measures such as grinding, welding, and replacement, malignant accidents caused by the development of fatigue damages can be avoided. Among them, magnetoacoustic emission stress nondestructive testing is to evaluate the internal stress state of materials by using the acoustic emission signals generated when magnetic domains reorient under the action of stress. Residual stress widely exists in various load-bearing structures and pressure vessels. Residual stress will be generated during the processes such as surface heat treatment and machining of steel and temperature changes. Magnetoacoustic emission stress detection can detect early damages such as stress concentration areas.

[0003] Existing magnetoacoustic emission stress detection usually magnetizes in a single direction (such as parallel to the weld or rolling direction), which has certain limitations. It may miss stress information in other directions. Only analyzing the magnetoacoustic emission signals in a single magnetization direction results in extremely low detection sensitivity. Therefore, optimizing the magnetization direction is a key factor in improving the accuracy of MAE stress detection. However, there are still many deficiencies in existing magnetoacoustic emission stress detection schemes:

[0004] First, signal generation dependence: The generation of MAE signals depends on the coupling effect between magnetic domain wall motion and stress. When the magnetization direction is parallel to the weld direction, it is only sensitive to the tensile / compressive stress along the magnetization direction, and there is almost no response to stresses in other directions, resulting in the loss of stress information.

[0005] Second, there is a detection risk when the stress direction is unknown: In engineering, the stress direction is often unknown (such as random cracks and complex geometric structures). The magnetization direction in only a single direction lacks accuracy, and it is difficult to find the optimal stress direction and magnetization direction, resulting in a high risk of detection failure.

[0006] Third, the influence of magnetic anisotropy of ferromagnetic materials: The magnetic anisotropy of ferromagnetic materials (such as the texture of rolled steel plates) will cause the magnetic domain wall motion to preferentially occur along the easy magnetization axis. Single magnetization in anisotropic materials will result in significant errors.

[0007] Fourth, the limitation of stress component detection: It can only detect a single direction (such as parallel to the weld or rolling direction), that is, the stress component parallel to the magnetization direction. The stress response in other directions is weak. For example, the transverse residual stress in welded joints is often ignored, and stress information in other directions may be missed. Summary of the Invention

[0008] An embodiment of the present invention provides a method and device for optimizing the selection of multiple magnetization directions based on magnetoacoustic emission stress detection, so as to solve the technical problems in the prior art that the magnetoacoustic emission (MAE) stress detection has limitations in the selection of magnetization directions, it is difficult to select the optimal magnetization direction for stress detection and it is difficult to meet the requirements of high-precision detection.

[0009] In view of the above technical problems, an embodiment of the present invention provides a method for optimizing the selection of multiple magnetization directions based on magnetoacoustic emission stress detection, including:

[0010] Applying excitations to two pairs of orthogonal Helmholtz coils based on two excitation sources with the same frequency but different amplitudes to generate an alternating magnetic field to magnetize the specimen to be tested;

[0011] Collecting the magnetoacoustic emission signals of the specimen to be tested, amplifying and filtering the magnetoacoustic emission signals to obtain enhanced magnetoacoustic emission signals, and collecting and storing them;

[0012] Adjusting the amplitude of the excitation source with a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions, applying different groups of stresses with a preset step size to the specimen to be tested for each angular direction of the enhanced magnetoacoustic emission signals, performing Wiener filtering processing on the magnetoacoustic emission signals under each stress group corresponding to each magnetization direction and extracting the envelope, extracting multiple peak signals from the envelope, and calculating the average peak of the multiple peak signals as the peak characteristic value;

[0013] Sorting out the peak characteristic values, plotting the trend diagram of the magnetization direction changing with stress, the peak curve of the magnetoacoustic emission signal, and the broken line diagram of stress and peak points, and analyzing them respectively to obtain the relationship between the direction of the magnetoacoustic emission signal and the stress change rate, so as to determine the optimal magnetization direction.

[0014] The present invention also provides a device for optimizing the selection of multiple magnetization directions based on magnetoacoustic emission stress detection, including:

[0015] An excitation module, configured to apply excitations to two pairs of orthogonal Helmholtz coils based on two excitation sources with the same frequency but different amplitudes to generate an alternating magnetic field to magnetize the specimen to be tested;

[0016] A signal preprocessing module, configured to collect the magnetoacoustic emission signals of the specimen to be tested, amplify and filter the magnetoacoustic emission signals to obtain enhanced magnetoacoustic emission signals, and collect and store them;

[0017] A feature acquisition module is used to change the amplitude of the excitation source by a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions. For the test piece of the enhanced magnetoacoustic emission signal in each angular direction, different groups of stresses with a preset step size are applied. Wiener filtering processing is carried out on the magnetoacoustic emission signals under the corresponding groups of stresses in each magnetization direction, and the envelope is extracted. Multiple peak signals are extracted from the envelope, and the average peak of the multiple peak signals is calculated as the peak feature value;

[0018] An analysis and determination module is used to sort out the peak feature values, draw a trend chart of the change of magnetization direction with stress, a peak curve of the magnetoacoustic emission signal, and a broken line chart of stress and peak points, and analyze them respectively to obtain the relationship between the direction of the magnetoacoustic emission signal and the stress change rate, so as to determine the optimal magnetization direction.

[0019] In the present invention, aiming at the problem that the stress information in different directions of the test piece cannot be obtained with a single magnetization direction, the optimal magnetization direction with the highest magnetization sensitivity is found by deeply analyzing the magnetoacoustic emission signals in different magnetization directions. In the selection of the magnetization direction, the traditional single magnetization method is abandoned, and dynamic adjustment methods such as multi-directional, rotational or vector magnetization are adopted to capture multi-dimensional stress components such as transverse and longitudinal residual stresses in welded joints, avoiding the lack of stress information and improving the comprehensiveness of detection.

[0020] In terms of magnetic field generation, two orthogonal coils are used to apply the same-phase excitation to generate magnetic fields in different angular directions to magnetize the test piece. By comparing the stress change conditions in different angular directions, the angle with the fastest stress change rate is selected as the optimal magnetization direction. In the data acquisition and analysis link, stresses are applied to the test piece in turn from different angular directions and the magnetoacoustic emission envelope is obtained. The peak values collected each time are averaged to reduce errors. At the same time, the stress change rate at different angles is used as the basis for sensitivity analysis to obtain the optimal magnetization direction.

[0021] In summary, the present invention has significant advantages: in terms of improving detection sensitivity and accuracy, the multi-directional magnetization direction selection can capture more dimensional stress components, and there is a good linear relationship between the peak value of the magnetoacoustic emission signal and the stress under different magnetization directions. In terms of avoiding information omission, the limitation of a single magnetization direction is overcome, effectively avoiding the omission of stress information in other directions; in terms of adapting to complex stress fields, it shows better detection effects in complex stress fields (such as welding residual stress, multiaxial fatigue), providing a more reliable stress detection method for engineering practice. Brief Description of the Drawings

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments of the present invention. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0023] Figure 1 is a flowchart of an optimization method for multi-magnetization direction selection based on magnetoacoustic emission stress detection in an embodiment of the present invention;

[0024] Figure 2 is a structural diagram of an optimization device for multi-magnetization direction selection based on magnetoacoustic emission stress detection in an embodiment of the present invention;

[0025] Figure 3 is a structural diagram of an optimization device for multi-magnetization direction selection based on magnetoacoustic emission stress detection in another embodiment of the present invention;

[0026] Figure 4 is a schematic diagram of signals before and after MAE filtering of magnetoacoustic emission signals in an embodiment of the present invention;

[0027] Figure 5 is a schematic diagram of magnetoacoustic emission filtered signals and envelope lines under different magnetization directions in an embodiment of the present invention;

[0028] Figure 6 is a schematic diagram of stress envelope lines of MAE under different magnetization directions in an embodiment of the present invention;

[0029] Figure 7 is a stress-peak point line graph of MAE under different magnetization directions in an embodiment of the present invention;

[0030] Figure 8 is a normalized feature map of magnetoacoustic emission signals under different magnetization directions in an embodiment of the present invention;

[0031] Figure 9 is a sensitivity curve graph of MAE under different magnetization directions in an embodiment of the present invention. Detailed implementation manners

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0033] The multi-magnetization direction selection and optimization method based on magnetoacoustic emission stress detection provided by the embodiments of the present invention can be applied in the application environment as Figure 1 shown. Specifically, the multi-magnetization direction selection and optimization method based on magnetoacoustic emission stress detection is applied in a multi-magnetization direction selection and optimization device based on magnetoacoustic emission stress detection. The multi-magnetization direction selection and optimization device based on magnetoacoustic emission stress detection includes a client and a server as Figure 2 shown. The client communicates with the server through a network. Among them, the client, also known as the user end, refers to a program that provides local services for clients corresponding to the server. The client can be installed on, but not limited to, various personal computers, laptop computers, smart phones, tablet computers, and portable wearable devices. The server can be implemented by an independent server or a server cluster composed of multiple servers.

[0034] As Figure 1 shown, an embodiment of the present invention provides a multi-magnetization direction selection and optimization method based on magnetoacoustic emission stress detection, including the following steps:

[0035] S10. Apply excitations to two pairs of orthogonal Helmholtz coils based on two excitation sources with the same frequency but different amplitudes to generate an alternating magnetic field to magnetize the specimen to be tested; it can be understood that, with the help of two excitation sources with the same frequency but different amplitudes, excitations are applied to two pairs of orthogonally arranged Helmholtz coils to generate an alternating magnetic field; the orthogonally arranged Helmholtz coils can generate a uniform and directionally controllable magnetic field, which is beneficial to comprehensively exciting the magnetoacoustic emission signals of the specimen to be tested in different directions.

[0036] S20. Collect the magnetoacoustic emission signals of the specimen to be tested, perform amplification and filtering processing on the magnetoacoustic emission signals to obtain enhanced magnetoacoustic emission signals, and collect and store them; it can be understood that the purpose of this step is to improve the quality and intensity of the signals, remove noise interference, and provide an accurate and reliable data basis for subsequent signal analysis.

[0037] S30. Adjust the amplitude of the excitation source by a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions. For the test specimens of the enhanced magnetoacoustic emission signals in each angular direction, apply different groups of stresses with a preset step size. Conduct Wiener filtering on the magnetoacoustic emission signals under each stress group corresponding to each magnetization direction and extract the envelope. Extract multiple peak signals from the envelope and calculate the average peak of the multiple peak signals as the peak eigenvalue. Understandably, by adjusting the amplitude of the excitation source by a preset amplitude, enhanced magnetoacoustic emission signals in different angular directions are obtained. For the signals in each angular direction, apply different groups of stresses with a preset step size to the test specimens, and then conduct Wiener filtering on the magnetoacoustic emission signals under each stress group corresponding to each magnetization direction. Applying different groups of stresses with a preset step size can simulate the material responses under different stress levels, which helps to understand the influence law of stress on magnetoacoustic emission signals. Wiener filtering can further improve the signal quality. The purpose of this step is to obtain the characteristic information of magnetoacoustic emission signals under different magnetization directions and stress conditions, providing data support for the subsequent determination of the optimal magnetization direction.

[0038] S40. Organize the peak eigenvalues, draw the trend graph of the magnetization direction changing with stress, the peak curve of the magnetoacoustic emission signal, and the broken line graph of stress and peak points, and analyze them respectively to obtain the relationship between the direction of the magnetoacoustic emission signal and the stress change rate, so as to determine the optimal magnetization direction. Understandably, through the analysis and processing of a large amount of data, the internal relationship between the magnetoacoustic emission signal, the magnetization direction, and the stress is excavated, which can intuitively display the change law of the magnetoacoustic emission signal from different angles and helps to deeply study the magnetoacoustic emission characteristics of materials. This step can determine in which magnetization direction the material is most sensitive to stress by analyzing the relationship between the direction of the magnetoacoustic emission signal and the stress change rate, and thus select this direction as the optimal magnetization direction.

[0039] In view of the problem that the stress information in different directions of the test specimen cannot be obtained with a single magnetization direction, the present invention finds the optimal magnetization direction with the highest magnetization sensitivity by deeply analyzing the magnetoacoustic emission signals in different magnetization directions. In terms of magnetization direction selection, the traditional single magnetization method is abandoned, and dynamic adjustment methods such as multi-directional, rotational, or vector magnetization are adopted to capture multi-dimensional stress components such as transverse and longitudinal residual stresses in welded joints, avoiding the lack of stress information and improving the comprehensiveness of detection.

[0040] In terms of magnetic field generation, two orthogonal coils are used to apply excitation with the same phase to generate magnetic fields with different direction angles to magnetize the specimen to be tested. By comparing the stress changes at different direction angles, the angle with the fastest stress change rate is selected as the optimal magnetization direction. In the data acquisition and analysis stage, stress is applied to the specimen to be tested successively from different direction angles and the magnetoacoustic emission envelope is obtained. The peak values of each acquisition are averaged to reduce errors. At the same time, the stress change rate at different angles is used as the basis for sensitivity analysis to obtain the optimal magnetization direction.

[0041] In one embodiment, as shown in FIG. 1 and Figure 3 shown, the step S10 includes the following sub-steps:

[0042] S101. Use a dual-channel function generator to generate two sine signals with the same frequency but different amplitudes. The sine signals serve as the excitation source for the magnetoacoustic emission signal. Understandably, before each output of the excitation signal, the phase coupling of these two sine signals is set to 0°, that is, in the same phase, and the sine signals provide a stable signal source for subsequent excitation.

[0043] S102. The two sine signals are respectively connected to two identical power amplifiers through the first channel and the second channel, and then the power amplifiers are connected to two pairs of orthogonal Helmholtz coils. Understandably, an alternating magnetic field will be generated after the Helmholtz coils are energized. The role of the power amplifier is to enhance the power of the signal so that it can drive the Helmholtz coils to generate a magnetic field with sufficient intensity, and the arrangement of the orthogonal Helmholtz coils can achieve more complex and flexible control of the magnetic field distribution.

[0044] S103. After the Helmholtz coils are energized, an alternating magnetic field is applied by the sine signal. The Helmholtz coils convert the sine current into an alternating magnetic field, and the alternating magnetic field magnetization acts on the specimen to be tested. The specimen undergoes magnetostriction and then generates a magnetoacoustic emission signal. Understandably, under the action of the alternating magnetic field, the internal magnetic domains will move and rearrange, and then mechanical vibrations will be generated. These mechanical vibrations propagate in the specimen in the form of elastic waves to form a magnetoacoustic emission signal.

[0045] In one embodiment, as shown in FIG. 1, the step S20 includes the following sub-steps:

[0046] S201. Set magnetoacoustic emission sensors on the specimen to be tested. The magnetoacoustic emission sensors are connected to a signal amplifier to amplify the magnetoacoustic emission signals, and the signal amplifier is connected to a pre - band - pass filter to filter the magnetoacoustic emission signals. Understandably, in order to capture the magnetoacoustic emission signals, magnetoacoustic emission sensors coated with coupling agent are placed on the surface of the specimen to be tested, with a center frequency of 80 kHz. Since the magnetoacoustic emission signals are extremely tiny, a pre - amplifier is needed to amplify them by 60 dB. At the same time, because the signal frequency band is relatively wide, a pre - band - pass filter (20 - 1200 kHz) is used for pre - filtering.

[0047] S202. Use a PicoScope acquisition card to collect the enhanced magnetoacoustic emission signals after amplification and filtering processing, and store them in a PC.

[0048] Understandably, the magnetoacoustic emission (MAE) is a phenomenon in ferromagnetic materials where elastic waves are generated due to the irreversible movement of magnetic domain walls or the sudden change of magnetic moments under the action of an alternating magnetic field. When the applied magnetic field changes, the internal magnetic domain structure of the material is dynamically reorganized, and local stress is rapidly released, exciting acoustic wave signals. The magnetoacoustic emission sensors can obtain these signals and convert them into electrical signals according to the piezoelectric effect. Since the signals are tiny, they need to be processed by an amplifier (such as amplifying by 60 dB) and a pre - band - pass filter. Subsequently, Wiener filtering is performed on the magnetoacoustic emission signals stored in the PC to reduce the signal - to - noise ratio.

[0049] In one embodiment, as shown in Figure 1, the step S30 includes the following sub - steps:

[0050] S301. Respectively obtain the magnetic field intensities of two Helmholtz coils under the power amplifier output through a gaussmeter, and use a magnetic field direction adjustment model to change the amplitude of the excitation source. By adjusting the amplitude of the magnetic field, different directions of magnetization can be obtained to acquire the angles of enhanced magnetoacoustic emission signals in different angular directions. The mathematical expression of the magnetic field direction adjustment model is:

[0051]

[0052] where B1 and B2 represent the magnetic field intensities of two Helmholtz coils under the power amplifier output, B 合 represents the intensity of the magnetic field synthesis, and θ represents the angles of enhanced magnetoacoustic emission signals in different directions.

[0053] Understandably, according to the vector property of the magnetic field, two pairs of coils generate magnetic fields with the same phase and different amplitudes. By adjusting the magnetic field amplitude, different directions of magnetization can be obtained.

[0054] S302. With a preset step size of 15°, for each specimen to be tested with enhanced magnetoacoustic emission signals in the range of 0° - 180° in a preset angular direction, apply stress groups with a preset step size of 10.9 Mpa respectively, and obtain the envelope of the enhanced magnetoacoustic emission signals after Wiener filtering through the moving average method. Collect at least 20 peak signals from the envelope and calculate their average peak value as the peak characteristic value.

[0055] Understandably, to extract peaks from the envelope after Wiener filtering, 20 peak signals can be collected and their average peak value can be calculated as the characteristic value. In the experiment for each angular direction, starting from 0 MPa, with every 10.9 MPa as a step size, repeat the above steps to collect magnetoacoustic emission signals at each stress, and keep increasing until 120 MPa. Filter the magnetoacoustic emission signals and extract the envelope for each group of stresses under each magnetization direction to obtain the average peak characteristics of each experiment.

[0056] Specifically, the specific process to obtain multiple peaks in the envelope for subsequent processing is as follows:

[0057] First, the device collects the original magnetoacoustic emission signals, which directly reflect the acoustic emission phenomenon of the material under the action of an alternating magnetic field. Since the original signals may contain noise and other interference components, preprocessing is required to improve the signal-to-noise ratio.

[0058] Next, perform Wiener filtering on the original signals. It can effectively reduce the influence of noise while retaining the main features of the signals, thus obtaining a clearer and more accurate signal representation.

[0059] After obtaining the signals after Wiener filtering, through methods such as the moving average method, the envelope of the filtered signals can be accurately obtained. The envelope can intuitively display the overall change trend and characteristics of the magnetoacoustic emission signals and is an important basis for subsequent analysis.

[0060] Subsequently, extract peak information from the envelope after Wiener filtering. These peaks represent the key feature points in the signals and are of great significance for analyzing the stress state and magnetization direction response of the material. For example, in the experiment for each angle, collect 20 peak signals and calculate their average value to reduce random errors and fluctuations and obtain a more stable peak characteristic value.

[0061] To comprehensively evaluate the response characteristics of the material under different stress levels, starting from 0 MPa, increase the stress value step by step with every 10.9 MPa as a step size until reaching the predetermined maximum stress value (such as 120 MPa). At each stress level, repeat the steps of signal collection, filtering processing, envelope extraction, and peak calculation to ensure the integrity and accuracy of the data.

[0062] Finally, for each group of stress levels under each magnetization direction, the magnetoacoustic emission signals are filtered and the envelopes are extracted in the same steps to obtain the average peak characteristics of each experiment as the peak characteristic values. These characteristic values will be used for subsequent analysis and comparison to determine the optimal magnetization direction, thereby achieving precise detection of the stress state.

[0063] In a specific embodiment, as Figures 4 to 5 shown, to accurately extract features and analyze the stress response characteristics of silicon steel sheets, first, a magnetoacoustic emitter is used to collect the magnetoacoustic emission signals of the specimen to be tested (silicon steel sheet), providing a basis for subsequent analysis. The collected magnetoacoustic emission signals then need to be processed using MATLAB to extract useful information.

[0064] During the experiment, to ensure the integrity and accuracy of the signals, the excitation sine signal needs to be maintained at 20 Hz, and each sampling should include at least 10 complete sine excitation signals, that is, at least 20 magnetoacoustic emission peaks. This is done to reduce errors through averaging during subsequent peak extraction. At the same time, the sampling rate is set to 6 MS / s to ensure that enough data points can be collected to avoid data loss.

[0065] Next, the calculation formula of the model is adjusted according to the magnetic field direction, and the geomagnetic field is calibrated by a teslameter to calculate the synthesized magnetic field, and then the voltage value of each channel is selected. In this process, it should be noted that the excitation signals of each channel should only have different amplitudes, while the phases need to be kept consistent to ensure the consistency and repeatability of the experiment.

[0066] Grouping is carried out at a step size of 15° ranging from 0° to 180°, and the stress is applied from 0 MPa to 120 MPa in each group of experiments. The same stress is applied under different magnetization directions to observe the change rate of the magnetoacoustic emission signals.

[0067] The experimental results show that the change rates of the magnetoacoustic emission signals are significantly different under different magnetization directions. For example, the decline rate of the magnetoacoustic emission signal in the 45° direction is the largest, while the decline rate of magnetization in the 90° direction is relatively small. This finding provides a basis for subsequent quantitative data processing and predicts that the change rate of the magnetoacoustic emission signal may first increase and then decrease.

[0068] To ensure the accuracy of subsequent signal processing, each group of experiments needs to be carried out under different magnetization directions and enough data cycles need to be collected, and at the same time, a sufficient sampling rate needs to be set. This can avoid errors caused by single peaks and signal loss due to insufficient sampling frequency, thereby improving the reliability and accuracy of the experiment.

[0069] As Figure 4 and Figure 5As shown, the original magnetoacoustic emission signals under stress-free magnetization in different directions and under an applied stress of 98 MPa demonstrate the variation characteristics of magnetoacoustic emission signals under different conditions, providing rich data support for subsequent analysis.

[0070] Figure 4 The original magnetoacoustic emission signals under stress-free magnetization in different directions and under an applied stress of 98 MPa are shown. Among them, Figure 4 (a) is the original magnetoacoustic emission signal, Figure 4 (b) is the filtered signal and its envelope.

[0071] Figure 5 The original magnetoacoustic emission signals in three different scenarios are shown. Among them, Figure 5 (a) are the original magnetoacoustic emission signals at 0 MPa and 98 MPa under magnetization in the 0° direction, Figure 5 (b) are the original magnetoacoustic emission signals at 0 MPa and 98 MPa under magnetization at 45° downward, Figure 5 (c) are the original magnetoacoustic emission signals at 0 MPa and 98 MPa under magnetization at 0° downward.

[0072] After comparison, it can be clearly observed that the decline rate of the magnetoacoustic emission signal in the 45° direction is the largest, while the decline rate in the mentioned 90° direction of magnetization is relatively small. This observation provides an important basis for subsequent quantitative data processing. Based on these data characteristics, it can be predicted that the change rate trend of the magnetoacoustic emission signal is to increase first and then decrease, laying a foundation for more accurate subsequent quantitative data processing.

[0073] In another specific embodiment, in order to deeply explore the relationship between the characteristics of magnetoacoustic emission signals and stress under different magnetization directions, a method of gradually increasing the tensile stress was adopted. Specifically, whenever the tensile stress of the silicon steel sheet was increased by 10.89 MPa, multiple magnetoacoustic emission signals were collected and obtained according to the experimental method under 0 MPa stress. Through this series of experiments, the magnetoacoustic emission envelopes corresponding to different stress levels under different magnetization directions were successfully plotted, as Figure 6 shown.

[0074] Figure 6 Details show the magnetoacoustic emission envelopes in different magnetization directions (0°, 15°, 30°, 45°, 60°, 90°) at four different stress levels starting from 0 MPa and increasing by 33.7 MPa each time. These envelopes intuitively reflect the rate of change of the magnetoacoustic emission signal amplitude with stress under different magnetization directions and at different stress levels.

[0075] By observing Figure 6From the change of the envelope curve, it can be clearly seen that there are significant differences in the change rate of the magnetoacoustic emission signal amplitude with the applied stress under different magnetization directions. Especially when the magnetization direction is 45°, the change rate reaches the maximum; as the magnetization direction deviates from 45°, the change rate gradually decreases, and when the magnetization direction is 90°, the change rate decreases to the minimum.

[0076] Based on the above observations, a preliminary conclusion is drawn that the amplitude change rate of the magnetoacoustic emission signal does change significantly under different magnetization directions. This discovery effectively solves the problem of stress information that may be missed when only considering a single magnetization direction in the past, reflecting the innovation and importance of the method in the magnetoacoustic emission detection technology. Subsequently, this conclusion will be further verified according to specific experimental data.

[0077] In a specific embodiment, as Figure 7 shown, in order to comprehensively explore the influence of different magnetization directions on the magnetoacoustic emission signal, magnetoacoustic emission signals under different magnetization directions are collected. In the specific operation, for the envelope curve at different stress levels for each magnetization direction, 20 peak points are extracted respectively, and the average values of these peak points are calculated. Subsequently, these average values are sorted according to the magnetization direction (from 0° to 165°), and a trend graph showing the change with the applied stress is plotted, that is Figure 7 (Line graph of stress and peak points under different magnetization directions of MAE). Among them, Figure 7 (a) shows the relationship between stress and peak points under the magnetization direction from 0° to 90°, while Figure 7 (b) shows the corresponding relationship under the magnetization direction from 105° to 165°.

[0078] Considering the symmetry of magnetic field magnetization, that is, the magnetization effect of the magnetization direction from 0° to 165° is the same as that after increasing by 180° each time, so the magnetoacoustic emission signals within the range of 0° to 165° are only collected. Based on this symmetry, the characteristics of the magnetoacoustic emission signals within the entire circular domain can be inferred.

[0079] By observing Figure 7 (a), it can be clearly seen that from the magnetization direction of 0° to 45°, the change rate of the peak points increases significantly, while from 45° to 90° it decreases significantly. Similarly, Figure 7 (b) also shows a certain symmetry, that is, the peak change rate of magnetoacoustic emission increases significantly from 105° to 135°, and then decreases significantly from 135° to 165°. These two figures together reveal the symmetry characteristics of the magnetoacoustic emission signals between 0° to 90° and 90° to 180° (inferred by symmetry).

[0080] After obtaining the line charts of stress and peak points under different magnetization directions, in order to further obtain the quantitative relationship between the magnetoacoustic emission peak signal and stress under different magnetization directions, each line chart was fitted with a straight line to obtain the slope and Pearson correlation coefficient of the fitted straight line under each different magnetization direction. The results show that the average value of the Pearson correlation coefficient in each magnetization direction reaches 0.9515, indicating that there is a good linear relationship between the magnetoacoustic emission signal peak and stress.

[0081] In a specific embodiment, as Figure 8 shown, in order to more intuitively analyze the variation of the magnetoacoustic emission signal peak under different magnetization directions, the magnetoacoustic emission signal peak curves under each magnetization direction were normalized. The normalization process helps to eliminate the differences between different data magnitudes, enabling the variation trends under different magnetization directions to be presented more clearly.

[0082] Specifically, Figure 8 was plotted, where Figure 8 (a) shows the normalized curve under the magnetization direction from 0° to 90°, while Figure 8 (b) shows the normalized curve under the magnetization direction from 105° to 165°. By observing these normalized curves, it can be clearly seen that within the two magnetization direction intervals of 0° to 90° and 90° to 165°, the variation rate of the magnetoacoustic emission signal peak first increases and then decreases.

[0083] This finding not only provides an intuitive understanding of the magnetoacoustic emission signal variation under different magnetization directions but also verifies the previous hypothesis about the variation trend of the magnetoacoustic emission signal peak with stress through quantitative analysis. The data after normalization is basically consistent with the previous hypothesis, further enhancing the reliability and accuracy of the research conclusion.

[0084] In another specific embodiment, by further observing the slopes of these fitted straight lines, it can be found that the relationship between the magnetoacoustic emission signal peak and stress first increases and then decreases under different magnetization directions, which is consistent with the previous prediction. To more intuitively display this relationship, the slope was used as a sensitivity index for the rate of change of the magnetoacoustic emission signal, and the corresponding chart was plotted, as Figure 9 shown.

[0085] Combined with Figure 8, it is possible to more intuitively and quantitatively analyze how fast the peak value of the magnetoacoustic emission signal changes under applied stress in different magnetizing directions. Due to the symmetry of the magnetizing direction, the sensitivity in the magnetizing direction of 0° to 165° is the same as that in the direction of 180° to 345°. It can be clearly seen from the figure that the sensitivity shows a trend of first increasing and then decreasing from 0° to 90°. According to the symmetry of the magnetized sample, the direction from 90° to 180° also shows a similar sensitivity change trend, and the effect is more significant. This finding is completely consistent with the previous hypothesis, indicating that stress information in different magnetic field directions can be effectively extracted, thereby avoiding information loss as much as possible.

[0086] In one embodiment, if Figure 2 As shown, the present invention also provides a multi-magnetization direction selection optimization device based on magnetic acoustic emission stress detection, comprising:

[0087] The excitation module 100 is used to apply excitation to two pairs of orthogonal Helmholtz coils based on two excitation sources with the same frequency but different amplitudes, so as to generate an alternating magnetic field to magnetize the test piece.

[0088] The signal preprocessing module 200 is used to collect the magnetoacoustic emission signal of the test piece, amplify and filter the magnetoacoustic emission signal to obtain an enhanced magnetoacoustic emission signal, collect and store it.

[0089] The feature acquisition module 300 is used to change the amplitude of the excitation source with a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions, apply different groups of stresses with preset step lengths to the test piece for the enhanced magnetoacoustic emission signals in each angular direction, perform Wiener filtering on the magnetoacoustic emission signals under the stress of the corresponding group in each magnetization direction and extract the envelope, and calculate the average peak value of the multiple peak signals extracted from the envelope as the peak characteristic value.

[0090] The analysis and determination module 400 is used to organize the peak characteristic values, draw a trend diagram of the magnetization direction changing with stress, a peak curve of the magnetoacoustic emission signal, and a line diagram of stress and peak points, and analyze the relationship between the magnetoacoustic emission signal direction and the stress change rate to determine the optimal magnetization direction.

[0091] In the device of the above embodiment of the present invention, the working principle of the device is to analyze the acoustic emission signal generated by the material under the action of the alternating magnetic field, and then evaluate the stress state inside the material. The magnetoacoustic emission phenomenon originates from the elastic waves generated by the magnetostrictive effect of ferromagnetic materials in the alternating magnetic field. These elastic waves are released by the irreversible movement of the magnetic domain wall or the sudden change of the magnetization vector. The stress state will change the magnetic domain structure of the material, thereby affecting the intensity and frequency of the magnetoacoustic emission signal. Therefore, by detecting these acoustic wave signals, we can infer the stress distribution inside the material.

[0092] It should be noted that the magnetostrictive coefficient of different materials has direction dependence. For example, materials such as silicon steel have significant differences in magnetostrictive coefficients in different crystal orientations. Therefore, when selecting the magnetization direction, if the direction with a larger magnetostrictive coefficient is selected for magnetization, the magnetoelastic energy change caused by stress can be amplified, thereby improving the detection sensitivity.

[0093] The device of the present invention has innovations in the selection of magnetization direction and the design of the detection device. By selecting different magnetization directions, stress information of the material in different directions can be obtained, so as to obtain more accurate stress data.

[0094] In one embodiment, as Figure 3 shown, the excitation module includes a dual-channel function generator, a first power amplifier and a second power amplifier. The first power amplifier is connected to the dual-channel function generator and the Helmholtz coil; the second power amplifier is connected to the dual-channel function generator and the Helmholtz coil. Understandably, the role of the power amplifier is to enhance the power of the signal so that it can drive the Helmholtz coil to generate a magnetic field with sufficient intensity.

[0095] In one embodiment, as Figure 3 shown, the signal preprocessing module includes a magnetoacoustic sensor arranged on the Helmholtz coil, a stress loading mechanism, a signal amplifier connected to the magnetoacoustic sensor, a pre-filter connected to the signal amplifier, and an acquisition card connected to the dual-channel function generator and the pre-filter. Understandably, the magnetoacoustic sensor can accurately sense the magnetoacoustic emission signal generated by the test specimen under the action of an alternating magnetic field, and convert this weak mechanical vibration signal into an electrical signal. The stress loading mechanism is used to apply different types and magnitudes of stress to the test specimen. In magnetoacoustic emission detection, by changing the stress state of the specimen, different magnetoacoustic emission signal characteristics can be excited, and these characteristics are closely related to the defects inside the specimen, material properties, etc. The role of the signal amplifier is to amplify this weak electrical signal, and the main function of the pre-filter is to filter the amplified signal, remove high-frequency noise, low-frequency drift or other interference components in the signal, retain the effective magnetoacoustic emission signal characteristics, and improve the quality and signal-to-noise ratio of the signal.

[0096] In one embodiment, as Figure 3 shown, the feature acquisition module includes an X channel and a Y channel. Both the X channel and the Y channel are connected to the acquisition card, and a Wiener filter is arranged on the X channel. Understandably, the Wiener filter can automatically adjust the parameters of the filter according to the statistical characteristics of the signal (such as the power spectral density of the signal and noise) to achieve the optimal filtering effect.

[0097] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for optimizing the selection of multiple magnetization directions based on magnetoacoustic emission stress detection, characterized in that Including: S10. Applying excitations to two pairs of orthogonal Helmholtz coils based on two excitation sources with the same frequency but different amplitudes to generate an alternating magnetic field to magnetize the specimen to be tested; S20. Collecting the magnetoacoustic emission signals of the specimen to be tested, amplifying and filtering the magnetoacoustic emission signals to obtain enhanced magnetoacoustic emission signals, and collecting and storing them; S30. Adjusting the amplitude of the excitation source with a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions. Applying different groups of stresses with a preset step size to the specimen to be tested for each angular direction of the enhanced magnetoacoustic emission signals. Performing Wiener filtering on the magnetoacoustic emission signals under the stress groups corresponding to each magnetization direction and extracting the envelope. Extracting multiple peak signals from the envelope and calculating the average peak of the multiple peak signals as the peak characteristic value; S40. Organizing the peak characteristic values, plotting the trend graph of the magnetization direction changing with stress, the peak curve of the magnetoacoustic emission signals, and the broken line graph of stress and peak points, and analyzing them respectively to obtain the relationship between the direction of the magnetoacoustic emission signals and the stress change rate, so as to determine the optimal magnetization direction.

2. The multi-magnetization direction selection optimization method based on magnetoacoustic emission stress detection according to claim 1, wherein The step S10 includes: S101. Using a dual-channel function generator to generate two sine signals with the same frequency but different amplitudes, and the sine signals are used as the excitation sources of the magnetoacoustic emission signals; S102. Connecting the two sine signals to two identical power amplifiers through the first channel and the second channel respectively, and then connecting the power amplifiers to two pairs of orthogonal Helmholtz coils; S103. After the Helmholtz coils are powered on, applying an alternating magnetic field with the sine signal. The Helmholtz coils convert the sine current into an alternating magnetic field, and the alternating magnetic field magnetizes the specimen to be tested. The specimen undergoes magnetostriction and then generates magnetoacoustic emission signals.

3. The multi-magnetization direction selection optimization method based on magnetoacoustic emission stress detection according to claim 2, wherein The step S20 includes: S201. Setting a magnetoacoustic emission sensor on the specimen to be tested. Connecting the magnetoacoustic emission sensor to a signal amplifier to amplify the magnetoacoustic emission signals, and connecting the signal amplifier to a pre-stage band-pass filter to filter the magnetoacoustic emission signals; S202. Using a PicoScope acquisition card to collect the enhanced magnetoacoustic emission signals after amplification and filtering, and storing them in a PC.

4. The multi-magnetization direction selection optimization method based on magnetoacoustic emission stress detection according to claim 3, characterized in that The step S30 includes: S301. Respectively obtaining the magnetic field intensities of the two Helmholtz coils under the power amplifier output through a gaussmeter, and using a magnetic field direction adjustment model to change the amplitude of the excitation source to obtain the angles of the enhanced magnetoacoustic emission signals in different angular directions. The mathematical expression of the magnetic field direction adjustment model is: Among them, B1 and B2 represent the magnetic field intensities of two Helmholtz coils under the power amplifier output, and B 合 represents the intensity of the synthesized magnetic field, and θ represents the angle of the enhanced magnetoacoustic emission signal in different directions; S302. With a preset step size of 15°, in the range from 0° to 180°, for each specimen to be tested with enhanced magnetoacoustic emission signals in a preset angular direction, applying stress groups with a preset step size of 10.9 Mpa respectively, and obtaining the envelope of the enhanced magnetoacoustic emission signals after Wiener filtering through the moving average method. Collecting at least 20 peak signals from the envelope and calculating their average peak as the peak characteristic value.

5. A multi-magnetization direction selection and optimization device based on magnetoacoustic emission stress detection, characterized in that, Including: An excitation module for applying excitations to two pairs of orthogonal Helmholtz coils based on two excitation sources with the same frequency but different amplitudes to generate an alternating magnetic field to magnetize the specimen to be tested; A signal preprocessing module for collecting magnetoacoustic emission signals of a specimen to be tested, amplifying and filtering the magnetoacoustic emission signals to obtain enhanced magnetoacoustic emission signals, and collecting and storing them; A feature acquisition module for adjusting the amplitude of an excitation source with a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions, applying different groups of stresses with a preset step size to the specimens to be tested for the enhanced magnetoacoustic emission signals in each angular direction, performing Wiener filtering on the magnetoacoustic emission signals under the stress groups corresponding to each magnetization direction and extracting the envelope, extracting multiple peak signals from the envelope, and calculating the average peak of the multiple peak signals as the peak feature value; An analysis and determination module for sorting out the peak feature values, plotting a trend graph of the change of magnetization direction with stress, a peak curve of the magnetoacoustic emission signal, and a broken line graph of stress and peak points, and respectively analyzing to obtain the relationship between the direction of the magnetoacoustic emission signal and the stress change rate to determine the optimal magnetization direction.

6. The multi-magnetization direction selection and optimization device based on magnetoacoustic emission stress detection according to claim 5, characterized in that The excitation module includes a dual-channel function generator, a first power amplifier, and a second power amplifier. The first power amplifier is connected to the dual-channel function generator and the Helmholtz coil; the second power amplifier is connected to the dual-channel function generator and the Helmholtz coil.

7. The multi-magnetization direction selection and optimization device based on magnetoacoustic emission stress detection according to claim 6, wherein The signal preprocessing module includes a magnetoacoustic sensor arranged on the Helmholtz coil, a stress loading mechanism, a signal amplifier connected to the magnetoacoustic sensor, a pre-filter connected to the signal amplifier, and an acquisition card connected to the dual-channel function generator and the pre-filter.

8. The multi-magnetization direction selection and optimization device based on magnetoacoustic emission stress detection according to claim 6, characterized in that The feature acquisition module includes an X channel and a Y channel. Both the X channel and the Y channel are connected to the acquisition card, and a Wiener filter is arranged on the X channel.

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