A method and apparatus for optimizing the selection of multiple magnetization directions based on magnetoacoustic emission stress detection

Abstract

This invention discloses a multi-magnetization direction selection optimization method and apparatus based on magnetoacoustic emission stress detection. The method includes applying excitation to two pairs of orthogonal Helmholtz coils using two excitation sources with the same frequency but different amplitudes to generate an alternating magnetic field to magnetize the test piece; acquiring the magnetoacoustic emission signal of the test piece, processing it to obtain an enhanced magnetoacoustic emission signal; performing Wiener filtering on the magnetoacoustic emission signal under each stress group corresponding to the magnetization direction and extracting the envelope; extracting multiple peak signals from the envelope; and calculating the average peak value of the multiple peak signals. This invention employs a multi-directional, dynamically adjustable magnetization method, utilizing orthogonal coils to generate magnetic fields in different directions, comparing stress changes to select the optimal magnetization direction, which can capture multi-dimensional stress components, improve detection sensitivity and accuracy, avoid information loss, and adapt to complex stress fields.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing, and in particular to a method and apparatus for optimizing the selection of multiple magnetization directions based on magnetoacoustic emission stress detection. Background Technology

[0002] With the rapid development of China's economy and industry, the quality standards and requirements for industrial products are increasingly stringent, making non-destructive testing (NDT) technology for ferromagnetic materials increasingly crucial for this booming industry. Cracks and other damage in engineering structures are direct causes of catastrophic accidents. NDT can provide early warnings of structural damage, allowing for remedial measures such as grinding, welding, and replacement, thus preventing serious accidents caused by fatigue damage. Magnetoacoustic emission (MEE) stress NDT utilizes the acoustic emission signals generated when magnetic domains in ferromagnetic materials realign under stress to assess the internal stress state of the material. Residual stress is widely present in various load-bearing structures and pressure vessels, generated during heat treatment, machining, and temperature changes in steel surfaces. MEE stress testing can detect early damage such as stress concentration areas.

[0003] Existing magnetoacoustic emission (MAE) stress detection methods typically employ magnetization in a single direction (e.g., parallel to the weld or rolling direction), which has limitations. It may miss stress information from other directions, and analyzing only the magnetoacoustic emission signal 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, existing MAE stress detection schemes still have many shortcomings:

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

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

[0006] Third, the magnetic anisotropy of ferromagnetic materials has an impact: the magnetic anisotropy of ferromagnetic materials (such as the texture of rolled steel plates) will cause the magnetic domain wall movement to preferentially proceed along the easy magnetization axis, and single magnetization will lead to significant errors in anisotropic materials.

[0007] Fourth, the limitations of stress component detection: it can only detect stress components in a single direction (such as parallel to the weld or rolling direction), that is, stress components parallel to the magnetization direction. The stress response in other directions is weak. For example, the transverse residual stress of the welded joint is often ignored, which may miss stress information in other directions. Summary of the Invention

[0008] This invention provides a method and apparatus for optimizing the selection of multiple magnetization directions based on magnetoacoustic emission stress detection, in order to solve the limitations of existing magnetoacoustic emission (MAE) stress detection in the selection of magnetization directions, the difficulty in selecting the optimal magnetization direction for stress detection, and the difficulty in meeting the requirements of high-precision detection.

[0009] In view of the above technical problems, embodiments of the present invention provide a multi-magnetization direction selection optimization method based on magnetoacoustic emission stress detection, comprising:

[0010] Two pairs of orthogonal Helmholtz coils are excited by two excitation sources with the same frequency but different amplitudes to generate an alternating magnetic field to magnetize the test piece.

[0011] The magnetoacoustic emission signal of the test piece is acquired, amplified and filtered to obtain an enhanced magnetoacoustic emission signal, which is then acquired and stored.

[0012] The amplitude of the excitation source is adjusted by a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions. Different sets of stresses with preset step sizes are applied to the test piece with enhanced magnetoacoustic emission signals in each angular direction. Wiener filtering is performed on the magnetoacoustic emission signals under the stress group corresponding to each magnetization direction and the envelope is extracted. Multiple peak signals are extracted from the envelope and the average peak value of the multiple peak signals is calculated as the peak feature value.

[0013] The peak characteristic values ​​were organized, and a trend graph of magnetization direction as a function of stress, a peak curve of magnetoacoustic emission signal, and a line graph of stress versus peak point were plotted. The relationship between the direction of magnetoacoustic emission signal and the rate of stress change was analyzed to determine the optimal magnetization direction.

[0014] This invention also provides a multi-magnetization direction selection optimization system based on magnetoacoustic emission stress detection, comprising:

[0015] The excitation module 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;

[0016] The signal preprocessing module is used to acquire the magnetoacoustic emission signal of the test piece, amplify and filter the magnetoacoustic emission signal to obtain an enhanced magnetoacoustic emission signal, and then acquire and store it.

[0017] The 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. Different sets of stresses with preset step sizes are applied to the test piece of the enhanced magnetoacoustic emission signal in each angular direction. Wiener filtering is performed on the magnetoacoustic emission signal under the corresponding set of stresses in each magnetization direction and the envelope is extracted. Multiple peak signals extracted from the envelope are used to calculate the average peak value of the multiple peak signals as the peak feature value.

[0018] The analysis and determination module is used to organize the peak characteristic values, draw the trend graph of magnetization direction with stress, the peak curve of magnetoacoustic emission signal and the line graph of stress and peak point, and analyze the relationship between the direction of magnetoacoustic emission signal and the rate of stress change to determine the optimal magnetization direction.

[0019] This invention addresses the problem that a single magnetization direction cannot acquire stress information in different directions of the test piece. It finds the optimal magnetization direction with the highest magnetization sensitivity by deeply analyzing the magnetoacoustic emission signals from different magnetization directions. In selecting 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. This avoids missing stress information and improves the comprehensiveness of the detection.

[0020] In terms of magnetic field generation, two orthogonal coils are used to apply the same phase excitation to generate magnetic fields at different angles to magnetize the test specimen. By comparing the stress changes at different 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 test specimen sequentially from different 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 determine the optimal magnetization direction.

[0021] In summary, this invention offers significant advantages: Regarding improved detection sensitivity and accuracy, the multi-directional magnetization direction selection captures stress components across more dimensions, and the peak values ​​of the magnetoacoustic emission signals under different magnetization directions exhibit a good linear relationship with the stress. In terms of avoiding information loss, it overcomes the limitations of a single magnetization direction, effectively preventing the omission of stress information from other directions. Furthermore, in adapting to complex stress fields, it demonstrates better detection performance in complex stress fields (such as welding residual stress and multiaxial fatigue), providing a more reliable stress detection method for engineering practice. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

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

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

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

[0028] Figure 6 This is a schematic diagram of the stress envelopes of MAE under different magnetization directions in one embodiment of the present invention;

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

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

[0031] Figure 9 This is a sensitivity curve of MAE under different magnetization directions in one embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The multi-magnetization direction selection optimization method based on magnetoacoustic emission stress detection provided in this invention can be applied to, for example... Figure 1 The application environment is shown. Specifically, the multi-magnetization direction selection optimization method based on magnetoacoustic emission stress detection is applied in a multi-magnetization direction selection optimization device based on magnetoacoustic emission stress detection, which includes, as shown in the example... Figure 2 The diagram shows a client and a server, with the client communicating with the server over a network. The client, also known as the user terminal, refers to the program that provides local services to the client, corresponding to the server. The client can be installed on, but is not limited to, various personal computers, laptops, smartphones, tablets, and portable wearable devices. The server can be implemented using a standalone server or a server cluster consisting of multiple servers.

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

[0035] S10. Two pairs of orthogonal Helmholtz coils are excited by two excitation sources with the same frequency but different amplitudes to generate an alternating magnetic field to magnetize the test piece. Understandably, an alternating magnetic field is generated by exciting two pairs of orthogonally placed Helmholtz coils with the same frequency but different amplitudes. The orthogonally arranged Helmholtz coils can generate a uniform and direction-controllable magnetic field, which is beneficial for comprehensively exciting the magnetoacoustic emission signals of the test piece in different directions.

[0036] S20. Acquire the magnetoacoustic emission signal of the test piece, amplify and filter the magnetoacoustic emission signal to obtain an enhanced magnetoacoustic emission signal, acquire and store it; understandably, this step aims to improve the quality and strength of the signal, remove noise interference, and provide an accurate and reliable data basis for subsequent signal analysis.

[0037] S30. Adjust the amplitude of the excitation source with a preset amplitude to obtain enhanced magnetoacoustic emission signals at different angles. Apply different sets of stresses with preset step sizes to the test piece for each angle of enhanced magnetoacoustic emission signal. Perform Wiener filtering on the magnetoacoustic emission signal under the stress set corresponding to each magnetization direction and extract the envelope. Extract multiple peak signals from the envelope and calculate the average peak value of the multiple peak signals as the peak feature value. In essence, enhanced magnetoacoustic emission signals at different angles are obtained by adjusting the amplitude of the excitation source with a preset amplitude. For each angle of signal, apply different sets of stresses with preset step sizes to the test piece, and then perform Wiener filtering on the magnetoacoustic emission signal under the stress set corresponding to each magnetization direction. Applying different sets of stresses with preset step sizes can simulate the material response under different stress levels, which helps to understand the influence of stress on the magnetoacoustic emission signal. Wiener filtering can further improve the signal quality. The purpose of this step is to obtain the characteristic information of the magnetoacoustic emission signal under different magnetization directions and stress conditions, providing data support for subsequent determination of the optimal magnetization direction.

[0038] S40. Organize the peak characteristic values ​​and plot the trend of magnetization direction versus stress, the peak curve of the magnetoacoustic emission signal, and a line graph of stress versus peak points. Analyze these to obtain the relationship between the magnetoacoustic emission signal direction and the rate of stress change, which is used to determine the optimal magnetization direction. Understandably, by analyzing and processing a large amount of data, the intrinsic relationship between the magnetoacoustic emission signal, magnetization direction, and stress can be uncovered. This allows for a visual representation of the variation law of the magnetoacoustic emission signal from different perspectives, facilitating in-depth research on the magnetoacoustic emission characteristics of materials. This step, by analyzing the relationship between the magnetoacoustic emission signal direction and the rate of stress change, can determine under which magnetization direction the material's response to force is most sensitive, thus selecting that direction as the optimal magnetization direction.

[0039] This invention addresses the problem that a single magnetization direction cannot acquire stress information in different directions of the test piece. It finds the optimal magnetization direction with the highest magnetization sensitivity by deeply analyzing the magnetoacoustic emission signals from different magnetization directions. In selecting the magnetization direction, it abandons the traditional single magnetization method and adopts dynamic adjustment methods such as multi-directional, rotational, or vector magnetization to capture multi-dimensional stress components, such as transverse and longitudinal residual stresses in welded joints, thus avoiding the loss of stress information and improving the comprehensiveness of the detection.

[0040] In terms of magnetic field generation, two orthogonal coils are used to apply the same phase excitation to generate magnetic fields at different angles to magnetize the test specimen. By comparing the stress changes at different 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 test specimen sequentially from different 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 determine the optimal magnetization direction.

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

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

[0043] S102. Two sinusoidal signals are respectively connected to two identical power amplifiers through the first and second channels, and then the power amplifiers are connected to two pairs of orthogonal Helmholtz coils. Understandably, the Helmholtz coils generate an alternating magnetic field when energized. The function of the power amplifier is to enhance the power of the signal so that it can drive the Helmholtz coils to generate a sufficiently strong magnetic field, while the orthogonal arrangement of the Helmholtz coils can achieve more complex and flexible magnetic field distribution control.

[0044] S103. After the Helmholtz coil is energized, an alternating magnetic field is applied using a sinusoidal signal. The Helmholtz coil converts the sinusoidal current into an alternating magnetic field. The alternating magnetic field magnetizes the test piece, causing it to magnetostrict and generate a magnetoacoustic emission signal. Understandably, under the influence of the alternating magnetic field, the internal magnetic domains will move and rearrange, resulting in mechanical vibration. This mechanical vibration propagates in the test piece in the form of elastic waves, forming a magnetoacoustic emission signal.

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

[0046] S201. A magnetoacoustic emission sensor is placed on the test piece. The magnetoacoustic emission sensor is connected to a signal amplifier to amplify the magnetoacoustic emission signal. The signal amplifier is connected to a pre-bandpass filter to filter the magnetoacoustic emission signal. Understandably, to capture this magnetoacoustic emission signal, a magnetoacoustic emission sensor coated with a coupling agent is placed on the surface of the test piece, with a center frequency of 80kHz. Because the magnetoacoustic emission signal is extremely small, it needs to be amplified by 60dB using a pre-amplifier. Simultaneously, due to the wide signal bandwidth, pre-filtering using a pre-bandpass filter (20-1200kHz) is necessary.

[0047] S202. Using the PicoScope acquisition card, the amplified and filtered enhanced magnetoacoustic emission signal is acquired and stored on a PC.

[0048] Understandably, magnetoacoustic emission (MAE) is the phenomenon where ferromagnetic materials generate elastic waves under the influence of an alternating magnetic field due to irreversible movement of magnetic domain walls or abrupt changes in magnetic moment. When the applied magnetic field changes, the internal magnetic domain structure of the material dynamically reorganizes, local stress is rapidly released, and an acoustic signal is excited. This signal can be obtained using a magnetoacoustic emission sensor and converted into an electrical signal based on the piezoelectric effect. Due to the small signal size, it needs to be processed by an amplifier (e.g., amplified by 60 dB) and a pre-bandpass filter. Subsequently, the magnetoacoustic emission signal stored in the PC is subjected to Wiener filtering to reduce the signal-to-noise ratio.

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

[0050] S301. The magnetic field strength of the two Helmholtz coils under the power amplifier output is obtained by using a gaussmeter. The amplitude of the excitation source is changed by using a magnetic field direction adjustment model. By adjusting the amplitude of the magnetic field, magnetization in different directions can be obtained, thereby obtaining the angle of the enhanced magnetoacoustic emission signal 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 strength of the two Helmholtz coils at the power amplifier output, B 合 θ represents the strength of the combined magnetic field, and θ represents the angle of the enhanced magnetoacoustic emission signal in different directions.

[0053] Understandably, based on the vector nature of magnetic fields, two pairs of coils generate magnetic fields with the same phase but different amplitudes. By adjusting the amplitude of the magnetic field, magnetization in different directions can be obtained.

[0054] S302. With a preset step size of 15°, apply a stress group of 10.9 MPa to the test piece for each preset angle direction of the enhanced magnetoacoustic emission signal in the range of 0°-180° for each preset angle direction. Obtain the envelope of the enhanced magnetoacoustic emission signal after Wiener filtering by the moving average method. Collect at least 20 peak signals from the envelope and calculate its average peak value as the peak characteristic value.

[0055] Understandably, extracting peak values ​​from the Wiener-filtered envelope allows for the acquisition of 20 peak signals, with the average peak value used as a feature value. In experiments at each directional angle, starting from 0 MPa, the above steps were repeated for each stress level, increasing in 10.9 MPa increments, until reaching 120 MPa. For each set of stresses under each magnetization direction, the magnetoacoustic emission signals were filtered and their envelopes extracted to obtain the average peak value feature for each experiment.

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

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

[0058] Next, the original signal is subjected to Wiener filtering, which can effectively reduce the influence of noise while preserving the main characteristics of the signal, thereby obtaining a clearer and more accurate signal representation.

[0059] After obtaining the Wiener-filtered signal, the envelope of the filtered signal can be accurately obtained using methods such as the moving average method. The envelope can intuitively show the overall trend and characteristics of the magnetoacoustic emission signal, and is an important foundation for subsequent analysis.

[0060] Subsequently, peak information is extracted from the Wiener-filtered envelope. These peaks represent key feature points in the signal and are of great significance for analyzing the stress state and magnetization direction response of the material. For example, in experiments at each angle, 20 peak signals are collected and their average value is calculated to reduce random errors and fluctuations, thereby obtaining more stable peak feature values.

[0061] To comprehensively evaluate the material's response characteristics under different stress levels, the stress value was gradually increased from 0 MPa in increments of 10.9 MPa until a predetermined maximum stress value (e.g., 120 MPa) was reached. At each stress level, the above steps of signal acquisition, filtering, envelope extraction, and peak value calculation were repeated to ensure data integrity and accuracy.

[0062] Finally, for each set of magnetoacoustic emission signals under each magnetization direction and stress, the same filtering and envelope extraction steps are performed to obtain the average peak feature of each experiment as the peak feature value. These feature values ​​will be used for subsequent analysis and comparison to determine the optimal magnetization direction, thereby achieving accurate detection of the stress state.

[0063] In one specific embodiment, such as Figures 4 to 5 As shown, in order to accurately extract features and analyze the stress response characteristics of silicon steel sheets, firstly, a magnetoacoustic emitter was used to acquire the magnetoacoustic emission signal of the test piece (silicon steel sheet), providing a basis for subsequent analysis. The acquired magnetoacoustic emission signal then needs to be processed using MATLAB to extract useful information.

[0064] During the experiment, to ensure signal integrity and accuracy, the excitation sinusoidal signal needed to be maintained at 20Hz, and each sample had to include at least 10 complete sinusoidal excitation signals, i.e., at least 20 magnetoacoustic emission peaks. This was done so that errors could be reduced through averaging during subsequent peak extraction. Simultaneously, the sampling rate was set to 6MS / s to ensure a sufficient number of data points were collected and to avoid data loss.

[0065] Next, based on the calculation formula of the magnetic field direction adjustment model, the geomagnetic field is calibrated using a teslameter to calculate the synthesized magnetic field, and then the voltage value of each channel is selected. During this process, it is important to note that the excitation signal for each channel should only differ in amplitude, while the phase must remain consistent to ensure the consistency and repeatability of the experiment.

[0066] The experiments were grouped in 15° increments, ranging from 0° to 180°, with stress applied ranging from 0 MPa to 120 MPa in each group. The same stress was applied under different magnetization directions, and the rate of change of the magnetoacoustic emission signal was observed.

[0067] Experimental results show that the rate of change of the magnetoacoustic emission signal varies significantly under different magnetization directions. For example, the rate of decrease in the magnetoacoustic emission signal is greatest at 45°, while the rate of decrease is relatively smaller at 90°. This finding provides a basis for subsequent quantitative data processing and predicts that the rate of change of the magnetoacoustic emission signal may initially increase and then decrease.

[0068] To ensure the accuracy of subsequent signal processing, each experiment needs to be conducted under different magnetization directions, acquiring a sufficient number of data periods, while setting an adequate sampling rate. This avoids errors from single peaks and signal loss due to insufficient sampling frequency, thereby improving the reliability and accuracy of the experiment.

[0069] like Figure 4 and Figure 5As shown, the original magnetoacoustic emission signals under stress-free and stress-applied conditions with magnetization in different directions 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 and stress-applied conditions with magnetization in different directions are shown. Figure 4 (a) is the original magnetoacoustic emission signal. Figure 4 (b) shows the filtered signal and its envelope.

[0071] Figure 5 The original magnetoacoustic emission signals were displayed in three different scenarios. Figure 5 (a) shows the original magnetoacoustic emission signals at 0 MPa and 98 MPa magnetized at 0°. Figure 5 (b) shows the original magnetoacoustic emission signals at 0 MPa and 98 MPa when magnetized downwards at 45°. Figure 5 (c) The original magnetoacoustic emission signals at 0 MPa and 98 MPa under 0° downward magnetization.

[0072] After comparison, it is evident that the magnetoacoustic emission signal decreases at the 45° direction, while the decrease rate is relatively smaller at the 90° direction of magnetization. This observation provides important evidence for subsequent quantitative data processing. Based on these data characteristics, it can be predicted that the rate of change of the magnetoacoustic emission signal will first increase and then decrease, laying the foundation for more accurate quantitative data processing.

[0073] In another specific embodiment, to further investigate the relationship between magnetoacoustic emission signal characteristics and stress under different magnetization directions, a method of gradually increasing tensile stress was adopted. Specifically, whenever the tensile stress on the silicon steel sheet 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, magnetoacoustic emission envelopes corresponding to different stress levels under different magnetization directions were successfully plotted, such as... Figure 6 Show.

[0074] Figure 6 The image details the magnetoacoustic emission envelopes for each magnetization direction (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 visually reflect the rate of change of magnetoacoustic emission signal amplitude with stress at different magnetization directions and stress levels.

[0075] Through observation Figure 6The changes in the envelope clearly show that the rate of change of the magnetoacoustic emission signal amplitude with applied stress varies significantly under different magnetization directions. The rate of change is particularly high at a 45° magnetization direction; as the magnetization direction deviates from 45°, the rate of change gradually decreases, reaching its minimum at a 90° magnetization direction.

[0076] Based on the above observations, we can preliminarily conclude that the rate of change of the amplitude of the magnetoacoustic emission signal does indeed change significantly under different magnetization directions. This discovery effectively solves the problem of stress information that might be missed when only considering a single magnetization direction, demonstrating the innovation and importance of the proposed method in magnetoacoustic emission detection technology. Further verification of this conclusion will be conducted using specific experimental data.

[0077] In one specific embodiment, such as Figure 7 To comprehensively investigate the influence of different magnetization directions on magnetoacoustic emission signals, magnetoacoustic emission signals under different magnetization directions were collected. Specifically, for each magnetization direction, 20 peak points were extracted from the envelope under different stress levels, and the average value of these peak points was calculated. Subsequently, these average values ​​were organized according to the magnetization direction (from 0° to 165°), and a trend graph showing the change with applied stress was plotted. Figure 7 (Line graphs showing stress versus peak point under different magnetization directions in MAE). Among them... Figure 7 (a) shows the relationship between stress and peak point in magnetization directions from 0° to 90°, while Figure 7 (b) shows the corresponding relationship between magnetization directions from 105° to 165°.

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

[0079] Through observation Figure 7 (a) It can be clearly seen that the rate of change of the peak point increases significantly from 0° to 45° in the magnetization direction, while it decreases significantly from 45° to 90°. Similarly, Figure 7 (b) also shows a certain symmetry, namely, the rate of change of the peak value of magnetoacoustic emission increases significantly from 105° to 135°, and then decreases significantly from 135° to 165°. Together, these two figures reveal the symmetry characteristics of the magnetoacoustic emission signal between 0° and 90° and between 90° and 180° (inferred from symmetry).

[0080] After obtaining the line graphs 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, a straight line was fitted to each line graph. The slope of the fitted line and its Pearson correlation coefficient for each different magnetization direction were obtained. The results show that the average Pearson correlation coefficient for each magnetization direction reached 0.9515, indicating a good linear relationship between the magnetoacoustic emission signal peak and stress.

[0081] In one specific embodiment, such as Figure 8 As shown, to more intuitively analyze the changes in the peak value of the magnetoacoustic emission signal under different magnetization directions, the peak value curves of the magnetoacoustic emission signal under each magnetization direction were normalized. Normalization helps to eliminate the differences between different data magnitudes, making the changing trends under different magnetization directions clearer.

[0082] Specifically, it was drawn Figure 8 ,in Figure 8 (a) shows the normalized curves for magnetization directions from 0° to 90°, while Figure 8 (b) shows the normalized curves for magnetization directions from 105° to 165°. By observing these normalized curves, it can be clearly seen that the rate of change of the peak value of the magnetoacoustic emission signal in the two magnetization direction ranges of 0° to 90° and 90° to 165° both show a trend of first increasing and then decreasing.

[0083] This discovery not only provides an intuitive understanding of the variations in magnetoacoustic emission signals under different magnetization directions, but also quantitatively verifies the previous hypothesis regarding the trend of magnetoacoustic emission signal peak values ​​with stress. The normalized data are in good agreement with the previous hypothesis, further enhancing the reliability and accuracy of the research conclusions.

[0084] In another specific embodiment, further observation of the slopes of these fitted lines reveals that the relationship between the peak value of the magnetoacoustic emission signal and stress exhibits a trend of first increasing and then decreasing under different magnetization directions, which is consistent with previous predictions. To more intuitively illustrate this relationship, the slope is used as a sensitivity indicator of the rate of change of the magnetoacoustic emission signal, and corresponding graphs are plotted, such as... Figure 9 As shown.

[0085] Combination Figure 8This allows for a more intuitive and quantitative analysis of the rate of change of the magnetoacoustic emission signal peak under applied stress in different magnetization directions. Due to the symmetry of the magnetization directions, the sensitivity in the 0° to 165° magnetization direction is the same as that in the 180° to 345° direction. The figure clearly shows that the sensitivity increases first and then decreases from 0° to 90°. Based on the symmetry of the magnetized sample, a similar sensitivity change trend is observed in the 90° to 180° direction, with a more significant effect. This finding is entirely consistent with previous assumptions, indicating that stress information under different magnetic field directions can be effectively extracted, thereby minimizing information loss.

[0086] In one embodiment, such as Figure 2 As shown, the present invention also provides a multi-magnetization direction selection optimization system based on magnetoacoustic 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 acquire the magnetoacoustic emission signal of the test piece, amplify and filter the magnetoacoustic emission signal to obtain an enhanced magnetoacoustic emission signal, and then acquire and store it.

[0089] The feature acquisition module 300 is used to change the amplitude of the excitation source by a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions. Different sets of stresses with preset step sizes are applied to the test piece of the enhanced magnetoacoustic emission signal in each angular direction. Wiener filtering is performed on the magnetoacoustic emission signal under the corresponding set of stresses in each magnetization direction and the envelope is extracted. Multiple peak signals extracted from the envelope are used to calculate the average peak value of the multiple peak signals as the peak feature value.

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

[0091] In the system described in the above embodiments of the present invention, the working principle of the system is to analyze the acoustic emission signals generated by the material under the action of an alternating magnetic field, and then assess the stress state inside the material. Magnetoacoustic emission originates from the elastic waves generated by ferromagnetic materials in an alternating magnetic field due to the magnetostrictive effect. These elastic waves are released by the irreversible motion of magnetic domain walls or abrupt changes in the magnetization vector. The stress state alters the magnetic domain structure of the material, thereby affecting the intensity and frequency characteristics of the magnetoacoustic emission signal. Therefore, by detecting these acoustic wave signals, we can deduce the stress distribution inside the material.

[0092] It is worth noting that the magnetostriction coefficient of different materials is direction-dependent; for example, the magnetostriction coefficient of materials such as silicon steel varies significantly in different crystal orientations. Therefore, when selecting the magnetization direction, choosing a direction with a larger magnetostriction coefficient can amplify the stress-induced changes in magnetoelastic properties, thereby improving the sensitivity of the detection.

[0093] The system of this invention innovates in the design of magnetization direction selection and detection device. By selecting different magnetization directions, it is possible to obtain stress information of the material in different directions, thereby obtaining more accurate stress data.

[0094] In one embodiment, such as Figure 3 As 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 also connected to the dual-channel function generator and the Helmholtz coil. Understandably, the power amplifier's function is to amplify the signal power, enabling it to drive the Helmholtz coil to generate a sufficiently strong magnetic field.

[0095] In one embodiment, such as Figure 3 As shown, the signal preprocessing module includes a magnetoacoustic sensor mounted on a Helmholtz coil, a stress loading mechanism, a signal amplifier connected to the magnetoacoustic sensor, a pre-filter connected to the signal amplifier, and a data 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 piece under an alternating magnetic field, converting 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 piece. In magnetoacoustic emission detection, by changing the stress state of the test piece, different magnetoacoustic emission signal characteristics can be excited. These characteristics are closely related to internal defects and material properties of the test piece. The signal amplifier amplifies this weak electrical signal, and the pre-filter filters the amplified signal, removing high-frequency noise, low-frequency drift, or other interference components, retaining effective magnetoacoustic emission signal characteristics, and improving signal quality and signal-to-noise ratio.

[0096] In one embodiment, such as Figure 3 As shown, the feature acquisition module includes an X channel and a Y channel, both of which are connected to the acquisition card. A Wiener filter is configured on the X channel. Understandably, a nanofilter can automatically adjust its parameters based on the statistical characteristics of the signal (such as the power spectral density of the signal and noise) to achieve optimal filtering performance.

[0097] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the 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, include: S10. Two pairs of orthogonal Helmholtz coils are excited based on two excitation sources with the same frequency but different amplitudes to generate an alternating magnetic field to magnetize the test piece. S20. Acquire the magnetoacoustic emission signal of the test piece, amplify and filter the magnetoacoustic emission signal to obtain an enhanced magnetoacoustic emission signal, and then acquire and store it. S30. Adjust the amplitude of the excitation source with a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions. Apply different sets of stresses with preset step sizes to the test piece with enhanced magnetoacoustic emission signals in each angular direction. Perform Wiener filtering on the magnetoacoustic emission signals under the stress set corresponding to each magnetization direction and extract the envelope. Extract multiple peak signals from the envelope and calculate the average peak value of the multiple peak signals as the peak feature value. S40. Organize the peak characteristic values, draw the trend graph of magnetization direction with stress, the peak curve of magnetoacoustic emission signal and the line graph of stress and peak point, and analyze them to obtain the relationship between the direction of magnetoacoustic emission signal and the rate of stress change, 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, characterized in that, Step S10 includes: S101. Use a dual-channel function generator to generate two sinusoidal signals with the same frequency but different amplitudes. The sinusoidal signals serve as the excitation source for the magnetoacoustic emission signal. S102. Two sinusoidal signals are connected to two identical power amplifiers through the first and second channels respectively, and then the power amplifiers are connected to two pairs of orthogonal Helmholtz coils. S103. After the Helmholtz coil is energized, an alternating magnetic field is applied by a sinusoidal signal. The Helmholtz coil converts the sinusoidal current into an alternating magnetic field. The alternating magnetic field magnetizes the test piece, causing the test piece to magnetostrict and generate a magnetoacoustic emission signal.

3. The multi-magnetization direction selection optimization method based on magnetoacoustic emission stress detection according to claim 2, characterized in that, Step S20 includes: S201. A magnetoacoustic emission sensor is set on the test piece. The magnetoacoustic emission sensor is connected to a signal amplifier to amplify the magnetoacoustic emission signal. The signal amplifier is connected to a pre-bandpass filter to filter the magnetoacoustic emission signal. S202. Using the PicoScope acquisition card, the amplified and filtered enhanced magnetoacoustic emission signal is acquired and stored on a PC.

4. The multi-magnetization direction selection optimization method based on magnetoacoustic emission stress detection according to claim 3, characterized in that, Step S30 includes: S301. The magnetic field strength of the two Helmholtz coils under the power amplifier output is obtained by using a gaussmeter. The amplitude of the excitation source is changed by using a magnetic field direction adjustment model to obtain the angle of the enhanced magnetoacoustic emission signal in different angular directions. The mathematical expression of the magnetic field direction adjustment model is: Where B1 and B2 represent the magnetic field strength of the two Helmholtz coils at the power amplifier output, B 合 The strength of the combined magnetic field is represented by θ, and the angle of the enhanced magnetoacoustic emission signal in different directions is represented by θ. S302. With a preset step size of 15°, apply a stress group of 10.9 MPa to the test piece for each preset angle direction of the enhanced magnetoacoustic emission signal in the range of 0°-180° for each preset angle direction. Obtain the envelope of the enhanced magnetoacoustic emission signal after Wiener filtering by the moving average method. Collect at least 20 peak signals from the envelope and calculate its average peak value as the peak characteristic value.

5. A multi-magnetization direction selection optimization device based on magnetoacoustic emission stress detection, characterized in that, include: The excitation module 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; The signal preprocessing module is used to acquire the magnetoacoustic emission signal of the test piece, amplify and filter the magnetoacoustic emission signal to obtain an enhanced magnetoacoustic emission signal, and then acquire and store it. The feature acquisition module is used to adjust the amplitude of the excitation source by a preset amplitude to obtain enhanced magnetoacoustic emission signals in different angular directions. Different sets of stresses with preset step sizes are applied to the test piece with enhanced magnetoacoustic emission signals in each angular direction. Wiener filtering is performed on the magnetoacoustic emission signals under the stress group corresponding to each magnetization direction and the envelope is extracted. Multiple peak signals are extracted from the envelope and the average peak value of the multiple peak signals is calculated as the peak feature value. The analysis and determination module is used to organize the peak characteristic values, draw the trend graph of magnetization direction with stress, the peak curve of magnetoacoustic emission signal and the line graph of stress and peak point, and analyze the relationship between the direction of magnetoacoustic emission signal and the rate of stress change to determine the optimal magnetization direction.

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

8. The multi-magnetization direction selection optimization device based on magnetoacoustic emission stress detection according to claim 7, characterized in that, The feature acquisition module includes an X channel and a Y channel, both of which are connected to the acquisition card. A Wiener filter is configured on the X channel.

Images