Detection system and detection analysis method for magnetic anisotropy caused by pressure stress under weak alternating current excitation

Abstract

A pressure stress induced magnetic anisotropy detection system under weak alternating current excitation comprises a detection probe which comprises a fixed frame, a detection coil, a U-shaped iron core and two groups of excitation coils connected in series; the detection probe is tightly attached and fixed to the test piece; the test piece is fixed on the pressure stress loading device; the output end of the signal generator is electrically connected with the input end of the power amplifier, and the output end of the power amplifier is electrically connected with the exciting coil; an output voltage detection end of the power amplifier is connected with a first input channel of the oscilloscope; the detection coil is connected with a second input channel of the oscilloscope; the upper computer is connected with an output channel of the oscilloscope; a method for detecting and analyzing magnetic anisotropy caused by compressive stress under weak alternating current excitation comprises the following steps: S0, determining Pm, fn, V1 and theta q applied by a test piece, and preferably selecting excitation signals; s1, carrying out magnetization detection on the test piece to obtain detection information; and S2, analyzing the compressive stress induced magnetic anisotropy characteristics of the test piece under weak alternating current excitation.

Description

Technical Field

[0001] The present invention relates to the technical field of stress detection, and in particular to a compressive stress-induced magnetic anisotropy detection system and a detection and analysis method under weak AC excitation. Background Art

[0002] Ferromagnetic materials are widely used in mechanical equipment. The compressive stress they experience during service is a key factor affecting structural safety. Therefore, the detection of compressive stress is crucial for the protection of ferromagnetic mechanical equipment. Traditional compressive stress detection technologies, such as strain gauges or ultrasonic waves, are susceptible to environmental interference and lack online monitoring capabilities. More advanced compressive stress detection technologies based on the magnetic anisotropy effect have become a research hotspot due to their advantages such as non-contact and high sensitivity. However, existing research results have mostly focused on the magnetic signal response under static or strong DC excitation. The characteristics of compressive stress-induced magnetic anisotropy under weak AC excitation have not been deeply studied. Weak AC excitation, as an emerging magnetic detection method, can influence the magnetic signal response by adjusting the excitation parameters, providing a new approach for high-precision compressive stress detection. Therefore, there is an urgent need to detect and analyze the characteristics of compressive stress-induced magnetic anisotropy under weak AC excitation to provide theoretical and technical support for compressive stress monitoring in ferromagnetic components during service. Summary of the Invention

[0003] In view of this, it is necessary to provide a compressive stress-induced magnetic anisotropy detection system and a detection and analysis method under weak AC excitation.

[0004] A system for detecting compressive stress-induced magnetic anisotropy under weak AC excitation comprises: a detection probe, a test piece, a compressive stress loading device, a signal generator, a power amplifier, an oscilloscope and a host computer; wherein the detection probe comprises: a fixing frame, a detection coil, a U-shaped iron core and two sets of excitation coils connected in series; the detection coil is hollow and arranged horizontally in the middle of the fixing frame; the two legs of the U-shaped iron core are arranged on both sides of the detection coil, and the center line connecting the two legs of the U-shaped iron core coincides with the axis of the detection coil; the two sets of excitation coils are symmetrically wound around the two legs of the U-shaped iron core, and the winding directions of the two sets of excitation coils are opposite; the detection probe is tightly fitted and fixed to the test piece; the test piece is fixed on the clamping device of the compressive stress loading device, and the axial direction of the test piece is consistent with the compressive stress loading direction of the compressive stress loading device; the output end of the signal generator is electrically connected to the input end of the power amplifier, and the output end of the power amplifier is electrically connected to the excitation coil; the output voltage detection end of the power amplifier is connected to the first input channel of the oscilloscope; the detection coil is connected to the second input channel of the oscilloscope; and the host computer is connected to the output channel of the oscilloscope.

[0005] Preferably, the test piece is plate-shaped with a circular through hole in the center; both ends of the U-shaped core are tightly fitted to the test piece, and the circular through hole is arranged at the center position of the line connecting the two ends of the U-shaped core.

[0006] Preferably, the fixing frame includes: a fixing groove, a first fixing plate and a second fixing plate; wherein the fixing groove is in the shape of a bottomless square groove and is arranged in the middle of the fixing frame; the first fixing plate and the second fixing plate are horizontally symmetrically fixed on both sides of the fixing groove; the first fixing hole and the second fixing hole are symmetrically opened on the first fixing plate and the second fixing plate respectively; the detection coil is horizontally placed in the fixing groove; the U-shaped iron core is mounted on the fixing groove, and the bottoms of the two legs of the U-shaped iron core are respectively inserted into the first fixing hole and the second fixing hole.

[0007] Preferably, the detection probe also includes: a cover body, which is arranged outside the U-shaped iron core and the detection coil, including: a main body, which is rectangular; a wire outlet hole is opened on the outer side of the main body; handles are set on both sides of the main body; and plate-shaped support feet extending outward are set on both sides of the bottom of the main body.

[0008] Preferably, the voltage of the power amplifier output signal is 5-8V and the frequency is 100-300 Hz.

[0009] A method for detecting and analyzing compressive stress-induced magnetic anisotropy under weak AC excitation, using any of the above-mentioned compressive stress-induced magnetic anisotropy detection systems under weak AC excitation, comprises the following steps:

[0010] S0, determine each level of compressive stress P that needs to be applied to the specimen during the test process n , each level of excitation frequency f of the scan n 、Each level excitation voltage V n 、Each level magnetization angle θ n , and the excitation frequency f of the preferred excitation signal * and the excitation voltage V * ;

[0011] S1. Perform magnetization testing on the specimen to obtain test information;

[0012] S2. Based on the detection information obtained in S1, the compressive stress-induced magnetic anisotropy characteristics of the specimen under weak AC excitation are analyzed.

[0013] Wherein, step S1 specifically includes the following steps:

[0014] S10, setting the orientation of the detection probe so that the magnetization angle θ0 formed between the excitation magnetic field and the compressive stress of the test piece is 0°;

[0015] S11, apply the optimal excitation signal to the excitation coil to magnetize the specimen, and then apply compressive stress to the specimen step by step starting from 0 MPa, and synchronously obtain the compressive stress P of the specimen at each level. n The induced voltage U2(t) of the corresponding detection coil;

[0016] S12, the maximum compressive stress P of the specimen maxWhen the load is kept constant, the specimen is loaded with excitation frequency f step by step. n , synchronously obtain the specimen at each level of excitation frequency f n The induced voltage U2(t) of the corresponding detection coil;

[0017] S13, removing the compressive stress from the test piece, removing the excitation signal from the excitation coil, separating the detection probe from the test piece, and demagnetizing the test piece to restore the test piece to its initial state;

[0018] S14, reattach the detection probe and the test piece, and make the magnetization angle consistent with the magnetization angle in S11;

[0019] S15. Apply maximum compressive stress P to the specimen max , keep the load constant, apply an excitation signal with the same frequency as the preferred excitation signal to the excitation coil, and load the excitation voltage V step by step n , synchronously obtain the specimen at each level of excitation voltage V n The corresponding excitation voltage U1(t) of the excitation coil and the induced voltage U2(t) of the detection coil;

[0020] S16, removing the compressive stress from the test piece, removing the excitation signal from the excitation coil, separating the detection probe from the test piece, and demagnetizing the test piece to restore the test piece to its initial state;

[0021] S17, reset the orientation of the detection probe so that the magnetization angle steps up one level based on the magnetization angle in S11, and repeat steps S11-S17 until each level of magnetization angle θ is completed. n Corresponding detection.

[0022] Preferably, step S2 specifically includes the following steps:

[0023] S20, according to the specimen obtained in S11 at different magnetization angles, each level of compressive stress P n The corresponding induced voltage U2(t) at the magnetization angle is obtained according to formula (1), and the compressive stress P of each level of the specimen at different magnetization angles is obtained. n The corresponding leakage magnetic field is the leakage magnetic induction intensity B, where n0 is the number of turns of the detection coil, and A0 is the cross-sectional area of the magnetic flux path of the detection coil;

[0024]

[0025] S21, at the same magnetization angle, each level of compressive stress P n The corresponding induced voltage U2(t) minus the induced voltage when the compressive stress is 0 MPa, the corresponding interference-free induced voltage U2 is obtained. ′ (t); Under the same magnetization angle, each level of compressive stress Pn The corresponding leakage magnetic induction intensity B of the leakage magnetic field is subtracted from the leakage magnetic induction intensity when the compressive stress is 0 MPa to obtain the corresponding non-interference leakage magnetic induction intensity B ′ ;

[0026] S22, according to the interference-free induced voltage U2 obtained in S21 ′ (t), and the corresponding magnetic field angle and compressive stress, construct the interference-free induced voltage U2 under different magnetic field angles ′ (t) Correlation fitting curve with compressive stress, analysis and acquisition of the influence of magnetic field angle on the change trend of compressive stress and non-interference induced voltage;

[0027] S23, according to the non-interference leakage magnetic induction intensity B obtained in S21 ′ , and the corresponding magnetic field angle and compressive stress, construct the non-interference leakage magnetic induction intensity B under different magnetic field angles ′ The correlation fitting curve with compressive stress is used to analyze and obtain the influence of magnetic field angle on the changing trend of compressive stress and undisturbed leakage magnetic induction intensity.

[0028] Preferably, step S2 further includes the following steps:

[0029] S24, according to the specimen obtained in S12 under different magnetic field angles, keep the maximum compressive stress constant, and preferably keep the excitation voltage constant, each level of excitation frequency f n The corresponding induced voltage U2(t) is used to construct the correlation fitting curve between the induced voltage and the excitation frequency at different magnetic field angles, and the response characteristics of the induced voltage as the excitation frequency changes are analyzed and obtained;

[0030] S25, according to the specimen obtained in S15, under different magnetic field angles, keep the maximum compressive stress constant, and preferably keep the excitation frequency constant, at each voltage V n The excitation voltage U1(t) of the excitation coil and the induced voltage U2(t) of the detection coil corresponding to the magnetic field angle are constructed to construct the correlation fitting curve between the induced voltage and the excitation voltage at different magnetic field angles, and the response characteristics of the induced voltage changing with the excitation voltage are analyzed and obtained.

[0031] Preferably, in step S0, the compressive stress P of each level to be applied to the specimen during the test is determined. n , each level of scanning frequency f n , each level voltage V n 、Each level magnetization angle θ n , specifically including:

[0032] S00, determine the compressive stress range 0-P of the specimen max , P maxThe maximum compressive stress is set, and the compressive stress loading step ΔP is set during the test. max and ΔP to determine the compressive stress P at each level of specimen loading n ;

[0033] S01, set the excitation frequency scanning range of the excitation signal to 100-300Hz, set the excitation frequency scanning change step Δf, and determine the excitation frequency f of each level of the scan based on the excitation frequency scanning range and Δf n ;

[0034] S02, set the excitation voltage scanning range of the excitation signal to 5-8V, set the excitation voltage scanning change step ΔV, and determine the excitation voltage V of each level of the scan based on the excitation voltage scanning range and ΔV. n ;

[0035] S03, set the magnetization angle detection range to 0°-90°, set the magnetization angle change step to Δθ, and determine each level of magnetization angle θ based on the magnetization angle detection range and Δθ. n .

[0036] Preferably, the excitation frequency f of the preferred excitation signal in step S0 is * and the excitation voltage V * , determined by the material properties of the specimen, as well as the resistance and wire diameter of the excitation coil.

[0037] Preferably, in step S00, the maximum compressive stress P max Less than or equal to the yield strength of the material to which the specimen belongs.

[0038] The above-mentioned compressive stress-induced magnetic anisotropy detection system under weak AC excitation, on the one hand, symmetrically arranges two groups of excitation coils connected in series and with opposite winding directions on the two legs of the U-shaped iron core of the detection probe. When the excitation signal is applied, the current directions of the two groups of excitation coils are opposite, so that the excitation magnetic fields generated by the two excitation coils can be superimposed on each other in the entire magnetic flux loop. Although a weak AC excitation signal is applied, the superposition of the excitation magnetic fields can completely magnetize the test piece, ensuring the accuracy and reliability of the detection results; on the other hand, by horizontally arranging a hollow detection coil between the two groups of excitation coils, the leakage magnetic signal under weak AC excitation can be accurately captured, which also ensures the accuracy of the detection results. and reliability; on the other hand, by opening a circular through hole in the center of the specimen, when the leakage magnetic signals with different directions of the excitation magnetic field and the compressive stress are detected and analyzed, it is ensured that the detection results will not be affected by the different defect shapes at each magnetic field angle, thereby improving the accuracy and reliability of the detection and analysis results; the above-mentioned compressive stress-induced magnetic anisotropy detection and analysis method under weak AC excitation, on the one hand, obtains the non-interference induced voltage and non-interference leakage magnetic induction intensity corresponding to each level of compressive stress of the specimen at different magnetic field angles by applying the preferred excitation signal to the specimen, and then obtains the correlation fitting curves of the non-interference induced voltage and compressive stress at different magnetic field angles, as well as the correlation fitting curves of the non-interference leakage magnetic induction intensity and compressive stress. The correlation fitting curve of the induced voltage and the excitation frequency at different magnetic field angles is obtained, and finally, the influence of the magnetic field angle on the changing trend of the compressive stress and the undisturbed induced voltage, as well as the influence of the magnetic field angle on the changing trend of the compressive stress and the leakage magnetic induction intensity are obtained by analysis. On the other hand, by applying the maximum compressive stress and the preferred excitation voltage to the specimen, the induced voltage corresponding to each level of excitation frequency is obtained when the maximum compressive stress and the excitation voltage are constant, and then the correlation fitting curve of the induced voltage and the excitation frequency at different magnetic field angles is obtained. Finally, the response characteristics of the induced voltage changing with the excitation frequency at different magnetic field angles are obtained by analysis. On the other hand, by applying the maximum compressive stress and the preferred excitation frequency to the specimen, the response characteristics of the induced voltage changing with the excitation frequency at different magnetic field angles are obtained when the maximum compressive stress and the excitation frequency are constant. , the induced voltage corresponding to each level of excitation voltage is obtained, and then the correlation fitting curve of the induced voltage and the excitation voltage under different magnetic field angles is obtained, and finally the response characteristics of the induced voltage changing with the excitation voltage under different magnetic field angles are obtained through analysis; compared with the magnetic signal response obtained under static or strong DC excitation in the prior art, the present invention detects and analyzes the compressive stress-induced magnetoanisotropy characteristics under weak AC excitation. On the one hand, it can provide a theoretical basis for understanding the magnetic response of ferromagnetic materials under compressive stress, and on the other hand, it can provide a new technical path for the online monitoring technology of compressive stress of ferromagnetic components in practical applications, and can also provide technical support and important basis for the sensitivity and accuracy of compressive stress detection under weak AC excitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the overall structure of the compressive stress-induced magnetic anisotropy detection system under weak AC excitation in the present invention.

[0040] Figure 2 It is a structural schematic diagram of the detection probe in the present invention.

[0041] Figure 3 Schematic diagram of the detailed structure of the fixing frame in the present invention.

[0042] Figure 4 This is a schematic structural diagram of the detection probe with a cover in the present invention.

[0043] Figure 5 Schematic diagram of the process of the method for detecting and analyzing compressive stress-induced magnetic anisotropy under weak AC excitation in the present invention.

[0044] Figure 6 1 is the correlation fitting curve between the non-interference induced voltage and the compressive stress at different magnetic field angles in the present invention.

[0045] Figure 7 It is the correlation fitting curve of the non-interference leakage magnetic induction intensity and compressive stress under different magnetic field angles in the present invention.

[0046] Figure 8 : is the correlation fitting curve between the induced voltage and the excitation frequency at different magnetic field angles in the present invention.

[0047] Figure 9 It is the correlation fitting curve between the induced voltage and the excitation voltage at different magnetic field angles in the present invention.

[0048] In the figure: detection probe 1; fixing frame 10; fixing slot 100; first fixing plate 101; second fixing plate 102; first fixing hole 103; second fixing hole 104; U-shaped iron core 11; excitation coil 12; detection coil 13; cover 14; main body 140; wire outlet hole 141; handle 142; support leg 143; signal generator 2; power amplifier 3; oscilloscope 4; host computer 5; test piece 6; through hole 60; compressive stress loading device 7. DETAILED DESCRIPTION

[0049] The technical solutions and technical effects of the embodiments of the present invention are further elaborated below in conjunction with the accompanying drawings of the present invention.

[0050] In the following specific embodiments of the present invention, a test specimen is made of Q235 carbon structural steel widely used in the engineering field, and its yield strength is 235 MPa. When making the test specimen, according to GB / T7314-2017 Metal Material Room Temperature Compression Test Specification, a 20 mm thick plate is processed into a standard test specimen of 120 mm*90 mm, and a circular through hole 60 with a diameter of 4 mm is opened at the center of the test specimen 6. In the compressive stress-induced magnetic anisotropy detection system under weak AC excitation, the signal generator 2 adopts the RIGOLDG4102 signal generator, and the power amplifier 3 adopts the LYB HB-877-4 low-voltage power amplifier, in the detection probe 1, the U-shaped iron core 11 is made of high-magnetic permeability PC40 ferrite, and 2040 turns of the excitation coil 12 are symmetrically wound on the two legs of the U-shaped iron core 11 to form a 41mm effective magnetic flux path for constructing a closed loop; the oscilloscope 4 adopts a Tektronix3 series mixed domain oscilloscope, whose first input channel is connected to the output voltage detection end of the power amplifier 3 for synchronously monitoring and obtaining the excitation voltage U1(t) related to the excitation magnetic field, and its second input channel is connected to the detection coil 13 for synchronously monitoring and obtaining the induced voltage U2(t) related to the leakage magnetic induction intensity of the leakage magnetic field; the compressive stress loading device adopts an SHT4605 microcomputer-controlled electro-hydraulic servo universal testing machine.

[0051] Please see Figure 1 and 2 As shown, a specific embodiment of the present invention provides a compressive stress-induced magnetic anisotropy detection system under weak AC excitation, comprising: a detection probe 1, a test piece 6, a compressive stress loading device 7, a signal generator 2, a power amplifier 3, an oscilloscope 4 and a host computer 5; wherein the detection probe 1 comprises: a fixing frame 10, a detection coil 13, a U-shaped iron core 11 and two sets of exciting coils 12 connected in series; the detection coil 13 is hollow and horizontally arranged in the middle of the fixing frame 10; the two legs of the U-shaped iron core 11 are arranged on both sides of the detection coil 13, and the center line of the two legs of the U-shaped iron core 11 coincides with the axis of the detection coil 13; the two sets of exciting coils 12 are respectively It is wound on the two legs of the U-shaped iron core 11, and the winding directions of the two groups of excitation coils 12 are opposite; the detection probe 1 is tightly fitted and fixed to the specimen 6; the specimen 6 is fixed on the clamping device of the compressive stress loading device 7, and the axial direction of the specimen 6 is consistent with the compressive stress loading direction of the compressive stress loading device 7; the output end of the signal generator 2 is electrically connected to the input end of the power amplifier 3, and the output end of the power amplifier 3 is electrically connected to the excitation coil 12; the output voltage detection end of the power amplifier 3 is connected to the first input channel of the oscilloscope 4; the detection coil 13 is connected to the second input channel of the oscilloscope 4; the host computer 5 is connected to the output channel of the oscilloscope 4.

[0052] In this embodiment, the fixing frame 10 of the detection probe 1 is made of non-metallic material, which fixes the excitation coil 12 and the detection coil 13 for easy testing. At the same time, the detection coil 13 is placed horizontally between the two excitation coils 12, and the detection coil 13 is hollow without an iron core. During detection, the leakage magnetic signal just passes through the hollow part of the detection coil 13, which facilitates the detection coil 13 to capture the leakage magnetic signal. By setting the winding directions of the two groups of excitation coils 12 in opposite directions, when the signal is applied, the currents generated by the two excitation coils 12 are in opposite directions, so that the excitation magnetic fields generated by the two excitation coils 12 can be superimposed on each other in the entire magnetic flux loop, thereby making the magnetization of the test piece 6 more thorough and complete.

[0053] In this embodiment, the detection probe 1 is tightly fitted and fixed to the specimen 6, the bottom of the fixing frame 10 is fixedly fitted to the bottom of the specimen 6, and then the two ends of the U-shaped iron core 11 are tightly fitted to the specimen 6. When the specimen 6 is subjected to compressive stress by the compressive stress loading device 7, the input signal generated by the signal generator 2 is transmitted to the excitation coil 12 after passing through the power amplifier 3, thereby generating an excitation magnetic field, and the U-shaped iron core 11 and the specimen 6 form a magnetic flux loop. The excitation magnetic field excites the specimen 6, and the stress in the specimen 6 causes the magnetic flux lines inside the specimen 6 to be distorted, and part of the magnetic flux lines leak to the surface of the specimen to form a leakage magnetic signal, and the magnetic flux lines set at The detection coil 13 between the two legs of the U-shaped iron core 11 is placed horizontally, so the leakage magnetic signal just passes through the center of the detection coil 13, and the detection coil 13 captures the leakage magnetic signal; at the same time, the output voltage detection end of the power amplifier 3 is connected to the first input channel of the oscilloscope 4, so that the oscilloscope 4 synchronously collects the excitation voltage generated by the excitation coil 12, and the detection coil 13 is connected to the second input channel of the oscilloscope 4, so that the oscilloscope 4 synchronously collects the induced voltage related to the leakage magnetic signal detected by the detection coil 13; and the collected excitation voltage and induced voltage are saved through the host computer 5 connected to the oscilloscope 4 and the OpenChoice Desktop software installed in the host computer 5, so as to facilitate the subsequent extraction of experimental data and analysis of experimental results;

[0054] Further, see Figure 1 As shown, the specimen 6 is plate-shaped with a circular through hole 60 in the center; both ends of the U-shaped core 11 are tightly fitted with the specimen 6, and the circular through hole 60 is arranged at the center position of the line connecting the two ends of the U-shaped core 11.

[0055] In this embodiment, a circular through hole 60 is opened in the center of the plate-like specimen 6 to form a circular defect inside the specimen 6. During the test, since the direction of the exciting magnetic field is located between the line connecting the two legs of the U-shaped iron core 11, and the direction of the compressive stress borne by the specimen 6 is consistent with the axial direction of the specimen 6, when the specimen 6 is rotated so that an angle is formed between the direction of the exciting magnetic field and the direction of the compressive stress, that is, the magnetic field angle formed is no longer 0 degrees, the circular defect will not affect the detection signal due to the different defect shapes at each magnetic field angle, so that the detection and analysis results are more accurate.

[0056] Further, see Figure 2 and 3 As shown, the fixing frame 10 includes: a fixing slot 100, a first fixing plate 101 and a second fixing plate 102; wherein the fixing slot 100 is a bottomless square slot and is arranged in the middle of the fixing frame 10; the first fixing plate 101 and the second fixing plate 102 are horizontally symmetrically fixed on both sides of the fixing slot 100; the first fixing plate 101 and the second fixing plate 102 are symmetrically provided with a first fixing hole 103 and a second fixing hole 104 respectively; the detection coil 13 is horizontally placed in the fixing slot 100; the U-shaped iron core 11 is mounted on the fixing slot 100, and the bottoms of the two legs of the U-shaped iron core 11 are respectively inserted into the first fixing hole 103 and the second fixing hole 104.

[0057] Further, see Figure 4 As shown, in order to ensure the safety of the operators during the inspection and improve the convenience during the test, the detection probe 1 also includes: a cover body 14, which is arranged outside the U-shaped iron core 11 and the detection coil 13, including: a main body 140, which is rectangular; a wire outlet hole 141 is provided on the outer side of the main body 140; handles 142 are provided on both sides of the main body 140; and plate-shaped support feet 143 extending outward are provided on both sides of the bottom of the main body 140.

[0058] In this embodiment, by providing a cover body 14, the operator is prevented from accidentally touching the excitation coil 12 and the detection coil 13, thereby improving the safety of the operation; at the same time, the wire outlet hole 141 is used to lead the positive and negative poles of the excitation coil 12 and the detection coil 13 out of the cover body 14 respectively and connect them to other equipment; the setting of the handle 142 makes it convenient for the operator to move the detection probe 1 during measurement; the setting of the support foot 143 allows the operator to stick the plate-shaped support foot 143 and the test piece 6 together during measurement to facilitate measurement.

[0059] Furthermore, the voltage of the output signal of the power amplifier 3 is 5-8V and the frequency is 100-300 Hz.

[0060] In this embodiment, through the above-mentioned settings, on the one hand, it is ensured that the signal applied by the excitation coil 12 is within the range of weak AC, and on the other hand, it is ensured that the test piece 6 can be fully magnetized, and no current overload will occur to cause the temperature of the excitation coil 12 to rise, and the magnetic flux of the leakage magnetic field will not exceed the range of the detection coil 13, thereby ensuring the accuracy and reliability of the final experimental data.

[0061] like Figure 5 As shown, a specific embodiment of the present invention further provides a method for detecting and analyzing compressive stress-induced magnetic anisotropy under weak AC excitation, using any of the above-mentioned compressive stress-induced magnetic anisotropy detection systems under weak AC excitation, comprising the following steps:

[0062] S0, determine each level of compressive stress P that needs to be applied to the specimen 6 during the test process m , each level of excitation frequency f of the scan n 、Each level excitation voltage V l 、Each level magnetization angle θ q , and the excitation frequency f of the preferred excitation signal * and the excitation voltage V * , m is an integer greater than or equal to 0, P0 represents the compressive stress is 0 MPa, n, l, are all natural numbers, q is an integer greater than or equal to 0, θ q Indicates that the magnetization angle is 0°, specifically including:

[0063] S00, determine the compressive stress range 0-P of specimen 6 max , P max is the maximum compressive stress, P max Less than or equal to the yield strength of the material of the specimen 6. In this specific embodiment, P max Set to 120Mpa, set the compressive stress loading step ΔP during the test to 10Mpa, according to P max and ΔP to determine the compressive stress P0-P at each level of specimen loading 12 They are 0Mpa, 10Mpa, 20Mpa, 30Mpa, 40Mpa, 50Mpa, 60Mpa, 70Mpa, 80Mpa, 90Mpa, 100Mpa, 110Mpa, and 120Mpa respectively;

[0064] S01, set the excitation frequency scanning range of the excitation signal to 100-300Hz, set the excitation frequency scanning change step Δf to 50Hz, and determine the excitation frequency f of each level of the scan based on the excitation frequency scanning range and Δf n ; f1-f5 are 100Hz, 150Hz, 200Hz, 250Hz and 300Hz respectively;

[0065] S02, setting the excitation voltage scanning range of the excitation signal to 5-8V, setting the excitation voltage scanning change step ΔV to 1V, and determining the excitation voltages V1-V4 of each scan level to be 5V, 6V, 7V, and 8V respectively according to the excitation voltage scanning range and ΔV;

[0066] S03. Set the magnetization angle detection range to 0°-90°, set the magnetization angle change step to Δθ to 30°, and determine each level of magnetization angle θ1-θ4 to be 0°, 30°, 60° and 90° respectively according to the magnetization angle detection range and Δθ.

[0067] Among them, the excitation frequency f of the excitation signal is preferably * and the excitation voltage V * , determined according to the material properties of the specimen 6 and the U-shaped core 11, as well as the resistance and wire diameter of the excitation coil 12; * On the one hand, the signal-to-noise ratio characteristics of the U-shaped iron core 11 need to be considered. On the other hand, it is necessary to consider that if the excitation frequency is too high, it will cause the vibration of the U-shaped iron core 11, affecting the close fit between the test piece 6 and the U-shaped iron core 11, and further affecting the authenticity of the test signal. Based on the above two points, 100 Hz is selected as the excitation frequency f of the preferred excitation signal. * ; After determining V * Since the intensity of the excitation voltage directly affects the efficiency of generating the magnetic field of the magnetic flux loop, too low an excitation voltage will result in the specimen 6 not being fully magnetized or the magnetization of the specimen being too long, affecting the experimental results or efficiency. However, too high a voltage will not only cause the magnetic flux of the leakage magnetic field to exceed the detection coil range, but will also cause the temperature of the excitation coil 12 to rise due to current overload, thereby affecting the authenticity of the test signal. Therefore, it is necessary to balance the magnetic field intensity and system safety. In this embodiment, based on the resistance of the excitation coil 12 being 64Ω, the wire diameter being 0.2mm, and the rated current limit of the excitation coil 12 being 1.57A, the excitation voltage V of the preferred excitation signal is determined. * The voltage is 5V, and the corresponding current of the excitation coil 12 is about 0.08A, which ensures the accuracy and reliability of the test data.

[0068] S1. Perform magnetization testing on the specimen to obtain test information, specifically including the following steps:

[0069] S10, setting the orientation of the detection probe so that the magnetization angle θ0 formed between the excitation magnetic field and the compressive stress of the test piece 6 is 0°;

[0070] S11, apply the preferred excitation signal to the excitation coil 12 to magnetize the specimen 6, and then apply compressive stress to the specimen 6 step by step starting from 0 MPa, and synchronously obtain the compressive stress P0-P 12 The induced voltage U2(t) of the detection coil 13 corresponding to P0 is 0 MPa;

[0071] S12, maximum compressive stress P at specimen 6 load max When the load is 120 MPa, the load is kept constant, and the excitation frequencies f1-f5 are applied to the specimen 6 step by step, and the induced voltage U2(t) of the detection coil 13 corresponding to the specimen 6 at f1-f5 is obtained synchronously;

[0072] S13, removing the compressive stress from the test piece 6, removing the excitation signal from the excitation coil 12, separating the detection probe 1 from the test piece 6, and demagnetizing the test piece 6 to restore the test piece 6 to its initial state;

[0073] S14, reattach the detection probe 1 and the test piece 6, and make the magnetization angle consistent with the magnetization angle in S11;

[0074] S15. Apply maximum compressive stress P to specimen 6. max The load is 120 MPa, and the load is kept constant. An excitation signal with a frequency consistent with the preferred excitation signal frequency, i.e., an excitation signal of 100 Hz, is applied to the excitation coil 12. Excitation voltages V1-V4 are applied step by step, and the excitation voltage U1(t) of the excitation coil 12 and the induced voltage U2(t) of the detection coil 13 corresponding to the test piece 6 at positions V1-V4 are simultaneously obtained.

[0075] S16, removing the compressive stress from the test piece 6, removing the excitation signal from the excitation coil 12, separating the detection probe 1 from the test piece 6, and demagnetizing the test piece 6 to restore the test piece 6 to its initial state;

[0076] S17, reset the orientation of the detection probe 1 so that the magnetization angle steps up one level based on the magnetization angle in S11, and repeat steps S11-S17 until the detection corresponding to each level of magnetization angle θ0-θ4 is completed.

[0077] S2. Analyze the compressive stress-induced magnetic anisotropy characteristics of the specimen 6 under weak AC excitation based on the detection information obtained in S1, specifically including the following steps:

[0078] S20, according to the specimen 6 obtained in S11 at different magnetization angles, each level of compressive stress P0-P 12 The corresponding induced voltage U2(t) is obtained, and according to formula (1), the compressive stress P0-P of each level of specimen 6 at different magnetization angles is obtained. 12 The corresponding leakage magnetic field is the leakage magnetic induction intensity B, where n0 is the number of turns of the detection coil, and A0 is the cross-sectional area of the magnetic flux path of the detection coil 13;

[0079]

[0080] S21, under the same magnetization angle, each level of compressive stress P0-P12 The corresponding induced voltage U2(t) minus the induced voltage when the compressive stress is 0 MPa, the compressive stress P0-P at each level is obtained. 12 The corresponding interference-free induced voltage U2 ′ (t); Under the same magnetization angle, each level of compressive stress P0-P 12 The corresponding leakage magnetic field leakage magnetic induction intensity B minus the leakage magnetic induction intensity when the compressive stress is 0 MPa, to obtain each level of compressive stress P0-P 12 The corresponding non-interference leakage magnetic induction intensity B ′ ;

[0081] S22, according to the interference-free induced voltage U2 obtained in S21 ′ (t), and the corresponding magnetic field angle and compressive stress, construct the interference-free induced voltage U2 under different magnetic field angles ′ (t) and the associated fitting curve of compressive stress, such as Figure 6 As shown in the figure, the influence of magnetic field angle on the variation trend of compressive stress and non-interference induced voltage is analyzed and obtained; Figure 6 It can be seen that at various magnetic field angles, the non-interference induced voltage shows an upward trend with the increase of compressive stress; when the magnetic field angle is 0°, that is, when the magnetization direction is consistent with the compressive stress direction, the increase in the non-interference induced voltage caused by the compressive stress is most significant, and as the magnetic field angle increases, the increase in the non-interference induced voltage shows a decreasing trend; under the condition of constant compressive stress, as the magnetic field angle increases, the non-interference induced voltage shows a monotonically decreasing characteristic, among which, when the magnetic field angle is 90°, the influence of compressive stress on the non-interference induced voltage is the smallest; the above results show that in order to ensure high sensitivity, the magnetization direction needs to be consistent with the compressive stress direction;

[0082] S23, according to the non-interference leakage magnetic induction intensity B obtained in S21 ′ , and the corresponding magnetic field angle and compressive stress, construct the non-interference leakage magnetic induction intensity B under different magnetic field angles ′ The correlation fitting curve with compressive stress is as follows: Figure 7 As shown in the figure, the influence of magnetic field angle on the variation trend of compressive stress and undisturbed magnetic leakage induction intensity is analyzed and obtained; Figure 7It can be seen that at various magnetic field angles, the non-interference leakage magnetic induction intensity increases with the increase of compressive stress. When the magnetic field angle is 0°, that is, when the magnetization direction is consistent with the compressive stress direction, the increase in the non-interference leakage magnetic induction intensity caused by the compressive stress is most significant. As the magnetic field angle increases, the increase in the non-interference leakage magnetic induction intensity shows a decreasing trend. Under the condition of constant compressive stress, the non-interference leakage magnetic induction intensity shows a monotonically decreasing characteristic as the magnetic field angle increases. Among them, when the magnetic field angle is 90°, the influence of compressive stress on the non-interference leakage magnetic induction intensity is the smallest. The above results show that in order to ensure high sensitivity, the magnetization direction needs to be consistent with the compressive stress direction.

[0083] S24, based on the induced voltage U2(t) corresponding to each level of excitation frequency f1-f5 of the specimen 6 obtained in S12 at different magnetic field angles, when the maximum compressive stress is kept constant at 120 MPa and the excitation voltage is preferably kept constant at 5 V, a correlation fitting curve between the induced voltage and the excitation frequency at different magnetic field angles is constructed, such as Figure 8 As shown, the response characteristics of the induced voltage changing with the excitation frequency are analyzed and obtained; Figure 8 It can be seen that when the excitation voltage is constant, the induced voltage amplitude at each magnetic field angle increases linearly with the excitation frequency, indicating that the excitation frequency is a key parameter affecting the detection signal amplitude and detection sensitivity;

[0084] S25. According to the test piece 6 obtained in S15, when the maximum compressive stress of 120 MPa is kept constant and the excitation frequency is preferably kept constant at 100 Hz, the excitation voltage U1(t) of the excitation coil 12 and the induced voltage U2(t) of the detection coil 13 corresponding to each voltage level V1-V4 are constructed, and the correlation fitting curve between the induced voltage and the excitation voltage at different magnetic field angles is constructed, as shown in FIG. Figure 9 As shown in the figure, the response characteristics of the induced voltage as the excitation voltage changes are analyzed and obtained. Figure 9 It can be seen that when the excitation frequency is constant, the induced voltage at each magnetic field angle shows a significant positive correlation with the excitation voltage, indicating that the excitation voltage is a key parameter affecting the detection signal amplitude and detection sensitivity.

[0085] The above-mentioned compressive stress-induced magnetic anisotropy detection system under weak AC excitation, on the one hand, symmetrically arranges two groups of excitation coils 12 connected in series and with opposite winding directions on the two legs of the U-shaped iron core 11 of the detection probe 1. When the excitation signal is applied, the current directions generated by the two groups of excitation coils 12 are opposite, so that the excitation magnetic fields generated by the two excitation coils 12 can be superimposed on each other in the entire magnetic flux loop. Although a weak AC excitation signal is applied, the superposition of the excitation magnetic fields can completely magnetize the test piece 6, ensuring the accuracy and reliability of the detection results; on the other hand, by horizontally arranging a hollow detection coil 13 between the two groups of excitation coils 12, the leakage magnetic signal under weak AC excitation can be accurately captured, which also ensures On the other hand, by providing a circular through hole 60 in the center of the specimen 6, when detecting and analyzing the leakage magnetic signals with different directions of the excitation magnetic field and the compressive stress, it is ensured that the detection results will not be affected by the different defect shapes at each magnetic field angle, thereby improving the accuracy and reliability of the detection and analysis results; the above-mentioned compressive stress-induced magnetic anisotropy detection and analysis method under weak AC excitation, on the one hand, obtains the non-interference induced voltage and non-interference leakage magnetic induction intensity corresponding to each level of compressive stress of the specimen 6 at different magnetic field angles by applying the preferred excitation signal to the specimen 6, and then obtains the correlation fitting curves of the non-interference induced voltage and compressive stress at different magnetic field angles, as well as the non-interference leakage magnetic induction intensity. The correlation fitting curve between magnetic induction intensity and compressive stress is obtained, and finally, the influence of magnetic field angle on the changing trend of compressive stress and undisturbed induced voltage, as well as the influence of magnetic field angle on the changing trend of compressive stress and leakage magnetic induction intensity are obtained by analysis; on the other hand, by applying maximum compressive stress and optimal excitation voltage to specimen 6, the induced voltage corresponding to each level of excitation frequency of the specimen when the maximum compressive stress and excitation voltage are constant is obtained, and then the correlation fitting curve between induced voltage and excitation frequency at different magnetic field angles is obtained, and finally, the response characteristics of induced voltage changing with excitation frequency at different magnetic field angles are obtained by analysis; on the other hand, by applying maximum compressive stress and optimal excitation frequency to specimen 6, the response characteristics of induced voltage changing with excitation frequency at different magnetic field angles are obtained. When the frequency is constant, the induced voltage corresponding to each level of excitation voltage is obtained, and then the correlation fitting curve of the induced voltage and the excitation voltage at different magnetic field angles is obtained. Finally, the response characteristics of the induced voltage changing with the excitation voltage at different magnetic field angles are obtained through analysis; compared with the magnetic signal response obtained under static or strong DC excitation in the prior art, the present invention detects and analyzes the compressive stress-induced magnetoanisotropy characteristics under weak AC excitation. On the one hand, it can provide a theoretical basis for understanding the magnetic response of ferromagnetic materials under compressive stress. On the other hand, it can provide a new technical path for the online monitoring technology of compressive stress in service of ferromagnetic components in practical applications, and can also provide technical support and important basis for the sensitivity and accuracy of compressive stress detection under weak AC excitation.

[0086] The above disclosure is only a preferred embodiment of the present invention, and it is certainly not intended to limit the scope of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A compressive stress-induced magnetic anisotropy detection system under weak AC excitation, characterized in that: include: A detection probe, a test piece, a compressive stress loading device, a signal generator, a power amplifier, an oscilloscope and a host computer; wherein the detection probe comprises: a fixing frame, a detection coil, a U-shaped iron core and two groups of excitation coils connected in series; the detection coil is hollow and arranged horizontally in the middle of the fixing frame; the two legs of the U-shaped iron core are arranged on both sides of the detection coil, and the center line of the two legs of the U-shaped iron core coincides with the axis of the detection coil; the two groups of excitation coils are symmetrically wound on the two legs of the U-shaped iron core, and the winding directions of the two groups of excitation coils are opposite; the detection probe is tightly fitted and fixed to the test piece; the test piece is fixed on the compressive stress loading device, and the axial direction of the test piece is consistent with the compressive stress loading direction of the compressive stress loading device; the output end of the signal generator is electrically connected to the input end of the power amplifier, and the output end of the power amplifier is electrically connected to the excitation coil; the output voltage detection end of the power amplifier is connected to the first input channel of the oscilloscope; the detection coil is connected to the second input channel of the oscilloscope; the host computer is connected to the output channel of the oscilloscope.

2. The compressive stress-induced magnetic anisotropy detection system under weak AC excitation according to claim 1, characterized in that: The specimen is plate-shaped with a circular through hole in the center; both ends of the U-shaped iron core are tightly fitted to the specimen, and the through hole is arranged at the center position of the line connecting the two ends of the U-shaped iron core.

3. The compressive stress-induced magnetic anisotropy detection system under weak AC excitation according to claim 1, wherein the fixing frame comprises: A fixing slot, a first fixing plate and a second fixing plate; wherein the fixing slot is a bottomless square slot and is arranged in the middle of the fixing frame; the first fixing plate and the second fixing plate are horizontally and symmetrically fixed on both sides of the fixing slot; the first fixing plate and the second fixing plate are respectively symmetrically provided with a first fixing hole and a second fixing hole; the detection coil is horizontally placed in the fixing slot; the U-shaped iron core is mounted on the fixing slot, and the bottoms of the two legs of the U-shaped iron core are respectively inserted into the first fixing hole and the second fixing hole.

4. The compressive stress-induced magnetic anisotropy detection system under weak AC excitation according to claim 1, characterized in that: The detection probe also includes: a cover body, which is arranged outside the U-shaped iron core and the detection coil, including: a main body, which is rectangular; a wire outlet hole is opened on the outer side of the main body; handles are set on both sides of the main body; and plate-shaped support feet extending outward are set on both sides of the bottom of the main body.

5. The compressive stress-induced magnetic anisotropy detection system under weak AC excitation according to claim 1, characterized in that: The voltage of the power amplifier output signal is 5-8V and the frequency is 100-300Hz.

6. A method for detecting and analyzing compressive stress-induced magnetic anisotropy under weak AC excitation, using the compressive stress-induced magnetic anisotropy detection system under weak AC excitation according to any one of claims 1 to 5, characterized in that: The following steps are involved: S0, determine each level of compressive stress P that needs to be applied to the specimen during the test process m , each level of excitation frequency f of the scan n 、Each level excitation voltage V l 、Each level magnetization angle θ q , and the excitation frequency f of the preferred excitation signal * and the excitation voltage V * ; S1. Perform magnetization testing on the specimen to obtain test information; S2. Based on the detection information obtained in S1, the compressive stress-induced magnetic anisotropy characteristics of the specimen under weak AC excitation are analyzed. Wherein, step S1 specifically includes the following steps: S10, setting the orientation of the detection probe so that the magnetization angle θ0 formed between the excitation magnetic field and the compressive stress of the test piece is 0°; S11, apply the optimal excitation signal to the excitation coil to magnetize the specimen, and then apply compressive stress to the specimen step by step starting from 0 MPa, and synchronously obtain the compressive stress P of the specimen at each level. n The induced voltage U2(t) of the corresponding detection coil; S12, the maximum compressive stress P of the specimen max When the load is kept constant, the specimen is loaded with excitation frequency f step by step. n , synchronously obtain the specimen at each level of excitation frequency f n The induced voltage U2(t) of the corresponding detection coil; S13, removing the compressive stress from the test piece, removing the excitation signal from the excitation coil, separating the detection probe from the test piece, and demagnetizing the test piece to restore the test piece to its initial state; S14, reattach the detection probe and the test piece, and make the magnetization angle consistent with the magnetization angle in S11; S15. Apply maximum compressive stress P to the specimen max , keep the load constant, apply an excitation signal with the same frequency as the preferred excitation signal to the excitation coil, and load the excitation voltage V step by step n , synchronously obtain the specimen at each level of excitation voltage V n The corresponding excitation voltage U1(t) of the excitation coil and the induced voltage U2(t) of the detection coil; S16, removing the compressive stress from the test piece, removing the excitation signal from the excitation coil, separating the detection probe from the test piece, and demagnetizing the test piece to restore the test piece to its initial state; S17, reset the orientation of the detection probe so that the magnetization angle steps up one level based on the magnetization angle in S11, and repeat steps S11-S17 until each level of magnetization angle θ is completed. n Corresponding detection.

7. The method for detecting and analyzing compressive stress-induced magnetic anisotropy under weak AC excitation according to claim 6, characterized in that: Step S2 specifically includes the following steps: S20, according to the specimen obtained in S11 at different magnetization angles, each level of compressive stress P n The corresponding induced voltage U2(t) at the magnetization angle is obtained according to formula (1), and the compressive stress P of each level of the specimen at different magnetization angles is obtained. n The corresponding leakage magnetic field is the leakage magnetic induction intensity B, where n0 is the number of turns of the detection coil, and A0 is the cross-sectional area of the magnetic flux path of the detection coil; S21, at the same magnetization angle, each level of compressive stress P n The corresponding induced voltage U2(t) minus the induced voltage when the compressive stress is 0 MPa, the corresponding interference-free induced voltage U2 is obtained. ′ (t); Under the same magnetization angle, each level of compressive stress P n The corresponding leakage magnetic induction intensity B of the leakage magnetic field is subtracted from the leakage magnetic induction intensity when the compressive stress is 0 MPa to obtain the corresponding non-interference leakage magnetic induction intensity B ′ ; S22, according to the interference-free induced voltage U2 obtained in S21 ′ (t), and the corresponding magnetic field angle and compressive stress, construct the interference-free induced voltage U2 under different magnetic field angles ′ (t) Correlation fitting curve with compressive stress, analysis and acquisition of the influence of magnetic field angle on the change trend of compressive stress and non-interference induced voltage; S23, according to the non-interference leakage magnetic induction intensity B obtained in S21 ′ , and the corresponding magnetic field angle and compressive stress, construct the non-interference leakage magnetic induction intensity B under different magnetic field angles ′ The correlation fitting curve with compressive stress is used to analyze and obtain the influence of magnetic field angle on the changing trend of compressive stress and undisturbed leakage magnetic induction intensity.

8. The method for detecting and analyzing compressive stress-induced magnetic anisotropy under weak AC excitation according to claim 7, characterized in that: Step S2 further includes the following steps: S24, according to the specimen obtained in S12 under different magnetic field angles, keep the maximum compressive stress constant, and preferably keep the excitation voltage constant, each level of excitation frequency f n The corresponding induced voltage U2(t) is used to construct the correlation fitting curve between the induced voltage and the excitation frequency at different magnetic field angles, and the response characteristics of the induced voltage as the excitation frequency changes are analyzed and obtained; S25, according to the specimen obtained in S15 under different magnetic field angles, keep the maximum compressive stress constant, and preferably keep the excitation frequency constant, at each level of excitation voltage V n The excitation voltage U1(t) of the excitation coil and the induced voltage U2(t) of the detection coil corresponding to the magnetic field angle are constructed to construct the correlation fitting curve between the induced voltage and the excitation voltage at different magnetic field angles, and the response characteristics of the induced voltage changing with the excitation voltage are analyzed and obtained.

9. The method for detecting and analyzing compressive stress-induced magnetic anisotropy under weak AC excitation according to claim 6, characterized in that: Step S0 determines the compressive stress P of each level to be applied to the specimen during the test process. n , each level of scanning frequency f n , each level voltage V n 、Each level magnetization angle θ n , specifically including: S00, determine the compressive stress range 0-P of the specimen max , P max The maximum compressive stress is set, and the compressive stress loading step ΔP is set during the test. max and ΔP to determine the compressive stress P at each level of specimen loading n ; S01, set the excitation frequency scanning range of the excitation signal to 100-300Hz, set the excitation frequency scanning change step Δf, and determine the excitation frequency f of each level of the scan based on the excitation frequency scanning range and Δf n ; S02, set the excitation voltage scanning range of the excitation signal to 5-8V, set the excitation voltage scanning change step ΔV, and determine the excitation voltage V of each level of the scan based on the excitation voltage scanning range and ΔV. n ; S03, set the magnetization angle detection range to 0°-90°, set the magnetization angle change step to Δθ, and determine each level of magnetization angle θ based on the magnetization angle detection range and Δθ. n .

10. The method for detecting and analyzing compressive stress-induced magnetic anisotropy under weak AC excitation according to claim 6, characterized in that: The excitation frequency f of the preferred excitation signal in step S0 is * and the excitation voltage V * , determined according to the material properties of the specimen and the U-shaped iron core, as well as the resistance and wire diameter of the excitation coil.

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