Hysteresis and magnetostrictive property test system and test method under stress loading

Abstract

The invention belongs to the technical field of force-magnetic characteristic testing, and particularly relates to a hysteresis and magnetostrictive property testing system and method under stress loading. The system is composed of a plate-shaped test piece, a stress loading module, a magnetic field loading module, a signal acquisition module and a computer. The stress loading module comprises a mounting plate, a T-shaped piece, a clamp, an L-shaped piece, a sliding module, a cushion block, a pressure sensor, an electric push rod and a driver; the magnetic field loading module comprises a U-shaped magnet yoke, a signal generator, a power amplifier, a sampling resistor and an exciting coil; the signal acquisition module comprises an induction loop, a strain gauge, a strain bridge box and a dynamic signal acquisition instrument; the method comprises the steps of test piece preparation, system assembly, parameter setting, stress loading and signal acquisition, magnetic field loading and signal acquisition, data processing and curve drawing. The test system and method can measure force-hysteresis and force-magnetostrictive properties, and have the characteristics of light weight, variable magnetic field direction and position and high test precision.

Description

Technical Field

[0001] The invention relates to the technical field of magnetostrictive property testing, and in particular to a system and method for testing hysteresis and magnetostrictive properties under stress loading. Background Art

[0002] Magnetic nondestructive testing technology for ferromagnetic components based on magnetomechanical coupling characteristics, such as metal magnetic memory testing, coercive force testing, Barkhausen testing, etc., has been a hot topic of research for scholars at home and abroad in recent years. In the theoretical research of these detection technologies, especially in quantitative analysis, multiple force-hysteresis characteristics and force-magnetostriction characteristic parameters are required. However, a large number of existing theoretical studies are cited literature data, and there is no research on the force-hysteresis and force-magnetostriction characteristics of specific materials, which makes the material parameters mismatch with the research conditions, resulting in poor quantitative results. In order to solve this problem, it is urgent to develop a device that can test the force-hysteresis and force-magnetostriction properties of materials and the corresponding test method.

[0003] To solve the above problems, Chinese patent CN114035132A proposes a force-magnetic coupling test device under simulated composite load conditions. The device can provide longitudinal and transverse magnetic field environments for different forms of stress loading such as pulling, pressing, and bending, which solves the composite problem of force and magnetic loads very well, but it cannot accurately measure the magnetic changes of the sample, so it does not meet the needs of material force-hysteresis and force-magnetostriction performance testing. Chinese patent CN1304848C proposes a horizontal force-magnetic coupling mechanical loading and measurement system. The system uses a stepper motor for mechanical loading and an electromagnet for magnetic field excitation, which can realize the measurement of various force-magnetic properties. However, the device is very large and bulky, the weight of the electromagnet alone is 1000kg, and the magnetic field direction and magnetization position are immutable; at the same time, its mechanical loading control method and signal acquisition method are relatively backward, and can no longer meet the modern high-precision measurement requirements.

[0004] Therefore, there is currently a lack of a testing system and corresponding method that can perform force-hysteresis and force-magnetostriction performance tests, and has a lightweight device, high measurement accuracy, and variable magnetic field direction and position. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a hysteresis and magnetostriction performance testing system and testing method under stress loading, so as to solve the problems in the prior art that the hysteresis and magnetostriction performance are difficult to accurately test, the testing device is bulky, and the direction and position of the magnetic field cannot be changed.

[0006] To achieve the above object, the present invention provides the following technical solutions: A hysteresis and magnetostriction performance testing system under stress loading, comprising a plate-shaped test piece, a stress loading module, a magnetic field loading module, a signal acquisition module and a computer; the plate-shaped test piece is composed of clamping sections at both ends, a test section in the middle and a transition section between the two; the stress loading module comprises a mounting plate, a T-shaped piece, a fixture, an L-shaped piece, a sliding module, a cushion block, a pressure sensor, an electric push rod and a driver; the fixture has two pieces, which are arranged on the left and right; the fixture on the left is connected to the mounting plate through the T-shaped piece, the fixture on the right is connected to the pressure sensor and the electric push rod in sequence through the vertical section of the L-shaped piece, and the horizontal section of the L-shaped piece is connected to the mounting plate through the sliding module. The electric push rod is connected to the mounting plate through the pad; the magnetic field loading module includes a U-shaped magnetic yoke, and a signal generator, a power amplifier, a sampling resistor and an excitation coil which are sequentially connected in series through wires, and the excitation coil is wound on the middle crossbeam of the U-shaped magnetic yoke; the signal acquisition module includes an induction loop, a strain gauge, a strain bridge box, a dynamic signal acquisition instrument and a computer; the induction loop is composed of an induction coil, an integral capacitor and an integral resistor which are connected in series through wires, and the induction coil is wound on the two legs of the U-shaped magnetic yoke; the strain gauge is attached to the surface of the test section of the plate-shaped specimen, and is electrically connected to the strain bridge box, the dynamic signal acquisition instrument and the computer in sequence.

[0007] Furthermore, the clamp is composed of a C-shaped part, a locking stud, a pressure block and a limit block. The top plate of the C-shaped part is provided with a threaded hole matching the locking stud, and the bottom plate of the C-shaped part is provided with a through hole on the same vertical line as the threaded hole of the top plate; the side of the limit block is provided with a protrusion, and the limit blocks are arranged in pairs on the bottom plate of the C-shaped part in a mirror image, and the protrusions are kept on the horizontal inner side. The plate-like specimen is normally limited by the locking stud and the pressure block, and the protrusion of the limit block cooperates with the transition section of the plate-like specimen to axially limit the plate-like specimen to keep the clamping stable and avoid slipping.

[0008] Furthermore, a pair of support seats are provided in the middle of the mounting plate, the U-shaped yoke is placed on the support seats, and the support seats are kept supported on the part of the U-shaped yoke that is not wound with the excitation coil, so as to avoid compressing the excitation coil and affecting the excitation magnetic field; the legs of the U-shaped yoke are upwardly attached to the lower surface of the test section of the plate-like specimen, and the weight of the U-shaped yoke is borne by the support seats, and no interference stress will be introduced to the test section of the plate-like specimen; the left array of the mounting plate 1 has multiple groups of mounting holes of T-shaped pieces 2, which are then combined with an electric push rod to meet the testing requirements of plate-like specimens of different lengths and improve the adaptability of the device; feet are provided at the top corners of the mounting plate, and two reinforcing square tubes are axially arranged below the mounting plate to enhance the ability of the mounting plate to resist deformation.

[0009] Furthermore, the electric push rod is internally driven by a servo motor, the electric push rod is electrically connected to the computer through the driver, and the pressure sensor is electrically connected to the computer. The driver cooperates with the servo motor to achieve constant thrust or tension output of the electric push rod, and cooperates with the pressure sensor feedback at the output end of the electric push rod to achieve precise control of thrust and tension.

[0010] Furthermore, the mounting plate, T-shaped piece, fixture, L-shaped piece, sliding module, pad, support seat, support foot and reinforced square tube are all made of non-ferromagnetic materials to prevent these parts from being magnetized and introducing interfering magnetic fields when the magnetic field is loaded.

[0011] On the other hand, the present invention also provides the following technical solution: A method for testing a hysteresis and magnetostriction performance testing system under stress loading, comprising the following steps: Step 1: Specimen preparation: After demagnetizing and cleaning the plate-shaped specimen, two strain gauges are selected and attached in parallel to the surface of the test section of the plate-shaped specimen. One of the strain gauges is directly fixed with an adhesive as a test gauge, and the other strain gauge is attached with tape as a compensation gauge. The parallel arrangement of the test gauge and the non-fixed compensation gauge can not only achieve temperature and magnetic field compensation, but also avoid the introduction of strain errors, so as to improve the detection accuracy of the device; Step 2: Assemble the system, use the computer to control the extension length of the electric push rod through the driver, so that the distance between the two fixtures matches the length of the specimen; put the two ends of the plate-like specimen into the fixture, keep the strain gauge on the lower surface of the plate-like specimen, and then put the pressure blocks on them respectively, tighten the locking studs, and press the plate-like specimen; connect the test piece and the compensation piece to the strain bridge box with wires respectively, and the connection method adopts the half-bridge method with anti-interference effect; Step 3: Parameter setting: setting the acquisition parameters of the dynamic signal acquisition instrument on the computer and performing initialization processing; Step 4: Stress loading and signal acquisition: Set the stress target value on the computer, control the electric push rod to drive the right fixture to move, and apply stress to the plate specimen. When the pressure sensor detects that the stress reaches the target value, the servo motor's torque output mode is used to keep the stress constant. After the strain waveform is stable, the strain data of the specimen under stress loading is collected. Step 5: Magnetic field loading and signal acquisition: select a sine wave on the signal generator, set the amplitude and frequency, and then output the excitation signal. After the waveform on the dynamic signal acquisition instrument is stable, synchronously collect the strain data, sampling resistor voltage, and integral capacitor voltage of the specimen under stress and magnetic field loading; Step 6: Data processing, filtering the strain data, sampling resistor voltage and integral capacitor voltage collected in steps 4 and 5; taking the average value of the processed strain data of step 4 as the initial strain; subtracting the initial strain from the processed strain data of step 5 to obtain the magnetostrictive strain under the stress state; converting the processed sampling resistor voltage and integral capacitor voltage into magnetic field intensity and magnetic induction intensity using formula (1) and formula (2) respectively, the formula is: in, H is the magnetic field strength, A / m; N 1 is the number of turns of the exciting coil; L is the length of the closed magnetic circuit, m; R 1 is the resistance value of the sampling resistor, Ω; U 1 is the sampling resistor voltage, V; B is the magnetic induction intensity, T; R 2 is the resistance value of the integrating resistor, Ω; C is the capacitive reactance of the integrating capacitor, F; N 2 is the number of turns of the detection coil; S is the cross-sectional area of ​​the U-shaped yoke, m 2 ; U 2 is the integrating capacitor voltage, V; Step 7: Curve drawing. Finally, the magnetostriction curve and hysteresis loop are drawn with the magnetic field intensity as the horizontal coordinate and the magnetostriction strain and magnetic induction intensity as the vertical coordinate.

[0012] The beneficial effects of the present invention are: (1) The combined design of the horizontally arranged stress loading module, magnetic field loading module and signal acquisition module can realize the synchronous loading of stress and magnetic field, and then synchronously test the force-hysteresis and force-magnetostriction performance, avoiding accidental errors introduced by separate testing.

[0013] (2) The magnetic field loading module is mainly composed of a U-shaped magnetic yoke and an excitation coil. Compared with the electromagnet excitation, it has the characteristics of being lightweight and having variable magnetic field direction and position.

[0014] (3) The selection of materials for the components of the device and the installation method of the U-shaped magnetic yoke enable the present invention to avoid the introduction of interfering magnetic fields and interfering stresses; the setting method of the test piece and the compensation piece can not only perform temperature and magnetic field compensation, but also avoid strain errors; the setting of the pressure sensor and the electric push rod driven by the servo motor can achieve constant stress output. These settings enable the device to have a high test accuracy.

[0015] (4) The design of the fixture and limit block can meet the testing requirements of plate specimens of different sizes and shapes, greatly improving the adaptability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0017] Figure 2 It is a schematic diagram of the magnetic field loading module and the signal acquisition module.

[0018] Figure 3 It is a schematic diagram of the magnetostrictive performance acquisition part.

[0019] Figure 4 It is a schematic diagram of the structure of the fixture.

[0020] Figure 5 It is a flow chart of the test method.

[0021] Figure 6 It is the hysteresis loop diagram.

[0022] Figure 7 It is a graph of magnetostriction curve.

[0023] In the figure, 1. mounting plate, 2. T-shaped part, 3. clamp, 301. locking stud, 302. C-shaped part, 303. pressure block, 304. limit block, 4. L-shaped part, 5. sliding module, 6. pad, 7. pressure sensor, 8. electric push rod, 9. U-shaped yoke, 10. sampling resistor, 11. excitation coil, 12. strain gauge, 13. induction coil, 14. integrating capacitor, 15. integrating resistor, 16. supporting seat, 17. supporting foot, 18. reinforced square tube. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0025] like Figure 1 , Figure 2 , Figure 3As shown, a hysteresis and magnetostriction performance testing system under stress loading proposed by the present invention includes a plate-shaped specimen, a stress loading module, a magnetic field loading module, a signal acquisition module and a computer. The plate-shaped specimen is composed of a clamping section at both ends, a test section in the middle and a transition section between the two. The stress loading module includes a mounting plate 1, a T-shaped member 2, a fixture 3, an L-shaped member 4, a sliding module 5, a cushion block 6, a pressure sensor 7, an electric push rod 8 and a driver. There are 2 fixtures 3, arranged on the left and right. The fixture 3 on the left is connected to the mounting plate 1 through the T-shaped member 2, and the fixture 3 on the right is connected to the pressure sensor 7 and the electric push rod 8 in sequence through the vertical section of the L-shaped member 4. The horizontal section of the L-shaped member 4 is connected to the mounting plate 1 through the sliding module 5, and the bottom of the electric push rod 8 is connected to the mounting plate 1 through the cushion block 6. The electric push rod 8 is driven by a servo motor inside, and the electric push rod 8 is electrically connected to the computer through the driver, and the pressure sensor 7 is electrically connected to the computer. The pressure sensor 7 and the servo motor cooperate to realize the constant stress output of the electric push rod 8, so as to achieve the purpose of high-precision control of stress. The magnetic field loading module includes a U-shaped yoke 9, and a signal generator, a power amplifier, a sampling resistor 10 and an excitation coil 11 which are sequentially connected in series through wires. The excitation coil 11 is wound on the middle crossbeam of the U-shaped yoke 9. The signal acquisition module includes an induction loop, a strain gauge 12, a strain bridge box and a dynamic signal acquisition instrument. The induction loop is composed of an induction coil 13, an integral capacitor 14 and an integral resistor 15 which are connected in series through wires. The induction coil 13 is wound on the two legs of the U-shaped yoke 9. The strain gauge 12 is attached to the surface of the test section of the plate-shaped specimen, and is electrically connected to the strain bridge box, the dynamic signal acquisition instrument and the computer in sequence.

[0026] like Figure 1 and Figure 4 As shown, the clamp 3 is composed of a locking stud 301, a C-shaped member 302, a pressure block 303 and a limit block 304. The top plate of the C-shaped member 302 is provided with a threaded hole matching the locking stud 301, and the bottom plate of the C-shaped member 302 is provided with a through hole on the same vertical line as the threaded hole of the top plate. The side of the limit block 304 is provided with a protrusion; the limit blocks 304 are arranged in pairs on the bottom plate of the C-shaped member 302 in mirror image, and the protrusions are kept on the horizontal inner side, and the limit block 304 is connected to the bottom plate of the C-shaped member 302 by bolts. The plate-like specimen is normally limited by the locking stud 301 and the pressure block 303, and the protrusion of the limit block 304 cooperates with the transition section of the plate-like specimen to axially limit the plate-like specimen to keep the clamping stable and avoid slipping.

[0027] like Figure 1As shown, a pair of support seats 16 are provided in the middle of the mounting plate 1, and the U-shaped yoke 9 is placed on the support seat 16, and the support seat 16 is kept supported on the part of the U-shaped yoke 9 where the excitation coil 11 is not wound, so as to avoid the excitation coil 11 from being compressed and affecting the excitation magnetic field; the legs of the U-shaped yoke 9 are upwardly attached to the lower surface of the test section of the plate-shaped specimen, and the weight of the U-shaped yoke 9 is borne by the support seat 16, so as not to introduce interference stress to the test section of the plate-shaped specimen. When conducting a test experiment, the support seat and the U-shaped yoke can be moved axially along the plate-shaped specimen to magnetize different positions of the plate-shaped specimen to meet different test requirements. The left array of the mounting plate 1 has multiple groups of mounting holes for T-shaped pieces 2, and is combined with an electric push rod to meet the test requirements of plate-shaped specimens of different lengths and improve the adaptability of the device; a support foot 17 is provided at the top corner of the mounting plate 1, and two reinforcing square tubes 18 are provided axially below the mounting plate 1 to enhance the rigidity of the mounting plate 1 and avoid deformation during high-load operation.

[0028] The mounting plate 1, T-shaped piece 2, fixture 3, L-shaped piece 4, sliding module 5, pad 6, support seat 16, support foot 17 and reinforced square tube 18 are all made of non-ferromagnetic materials to prevent these parts from being magnetized and introducing interfering magnetic fields when the magnetic field is loaded.

[0029] On the other hand, Figure 5 As shown, the present invention also provides the following technical solution: A method for testing a hysteresis and magnetostriction performance testing system under stress loading, comprising the following steps: Step 1: Specimen preparation: After demagnetizing and cleaning the plate-shaped specimen, two strain gauges are selected and attached in parallel to the surface of the test section of the plate-shaped specimen. One of the strain gauges is directly fixed with an adhesive as a test gauge, and the other strain gauge is attached with tape as a compensation gauge. The parallel arrangement of the test gauge and the non-fixed compensation gauge can not only achieve temperature and magnetic field compensation, but also avoid the introduction of strain errors, so as to improve the detection accuracy of the device; Step 2: Assemble the system, use the computer to control the extension length of the electric push rod through the driver, so that the distance between the two fixtures matches the length of the specimen; put the two ends of the plate-like specimen into the fixture, keep the strain gauge on the lower surface of the plate-like specimen, and then put the pressure blocks on them respectively, tighten the locking studs, and press the plate-like specimen; connect the test piece and the compensation piece to the strain bridge box with wires respectively, and the connection method adopts the half-bridge method with anti-interference effect; Step 3: Parameter setting: setting the acquisition parameters of the dynamic signal acquisition instrument on the computer and performing initialization processing; Step 4: Stress loading and signal acquisition: Set the stress target value on the computer, control the electric push rod to drive the right fixture to move, and apply stress to the plate specimen. When the pressure sensor detects that the stress reaches the target value, the servo motor's torque output mode is used to keep the stress constant. After the strain waveform is stable, the strain data of the specimen under stress loading is collected. Step 5: Magnetic field loading and signal acquisition: select a sine wave on the signal generator, set the amplitude and frequency, and then output the excitation signal. After the waveform on the dynamic signal acquisition instrument is stable, synchronously collect the strain data, sampling resistor voltage, and integral capacitor voltage of the specimen under stress and magnetic field loading; Step 6: Data processing, filtering the strain data, sampling resistor voltage and integral capacitor voltage collected in steps 4 and 5; taking the average value of the processed strain data of step 4 as the initial strain; subtracting the initial strain from the processed strain data of step 5 to obtain the magnetostrictive strain under the stress state; converting the processed sampling resistor voltage and integral capacitor voltage into magnetic field intensity and magnetic induction intensity using formula (1) and formula (2) respectively, the formula is: in, H is the magnetic field strength, A / m; N 1 is the number of turns of the exciting coil; L is the length of the closed magnetic circuit, m; R 1 is the resistance value of the sampling resistor, Ω; U 1 is the sampling resistor voltage, V; B is the magnetic induction intensity, T; R 2 is the resistance value of the integrating resistor, Ω; C is the capacitive reactance of the integrating capacitor, F; N 2 is the number of turns of the detection coil; S is the cross-sectional area of ​​the U-shaped yoke, m 2 ; U 2 is the integrating capacitor voltage, V; Step 7: Plot the curve, with magnetic field intensity as the horizontal coordinate and magnetostrictive strain and magnetic induction intensity as the vertical coordinates, such as Figure 6 and Figure 7 As shown, the magnetostriction curve and hysteresis loop are drawn.

[0030] In addition to the above-mentioned embodiments, the present invention also has the following second embodiment, firstly, the locking stud 301, the pressing block 303 and the limiting block 304 of the clamp 3 are removed, and then the long strip plate-shaped specimen is replaced with a square flat specimen with a through hole preset at the end, and then a flat head pin is used to sequentially pass through the top plate threaded hole of the C-shaped member 302, the through hole of the flat specimen and the through hole of the bottom plate of the C-shaped member 302 to achieve axial limiting of the flat specimen. In this installation mode, in addition to the tensile test of the square flat specimen, the direction of the magnetic field applied by the U-shaped magnetic yoke 9 to the specimen can be changed by rotating the support seat 16, and performance tests in different force-magnetic coupling directions can be performed to meet the test requirements of complex loading conditions, which greatly improves the adaptability of the test device.

Claims

1. A hysteresis and magnetostriction performance testing system under stress loading, characterized in that: It includes a plate-shaped specimen, a stress loading module, a magnetic field loading module, a signal acquisition module and a computer; The plate-shaped test piece is composed of clamping sections at both ends, a testing section in the middle and a transition section between the two; The stress loading module includes a mounting plate, a T-shaped piece, a fixture, an L-shaped piece, a sliding module, a cushion block, a pressure sensor, an electric push rod and a driver; the fixture has two pieces, which are arranged on the left and right; the fixture on the left is connected to the mounting plate through the T-shaped piece, and the fixture on the right is connected to the pressure sensor and the electric push rod in sequence through the vertical section of the L-shaped piece, the horizontal section of the L-shaped piece is connected to the mounting plate through the sliding module, and the bottom of the electric push rod is connected to the mounting plate through the cushion block; The magnetic field loading module includes a U-shaped magnetic yoke, and a signal generator, a power amplifier, a sampling resistor and an excitation coil which are sequentially connected in series through a wire, and the excitation coil is wound on the middle crossbeam of the U-shaped magnetic yoke; The signal acquisition module includes an induction loop, a strain gauge, a strain bridge box and a dynamic signal acquisition instrument; the induction loop is composed of an induction coil, an integral capacitor, and an integral resistor connected in series through a wire, and the induction coil is wound around the two legs of the U-shaped magnetic yoke; the strain gauge is attached to the surface of the test section of the plate-shaped specimen, and is electrically connected to the strain bridge box, the dynamic signal acquisition instrument and the computer in sequence.

2. The hysteresis and magnetostriction performance testing system under stress loading according to claim 1, characterized in that: The clamp consists of a C-shaped part, a locking stud, a pressure block and a limit block. The top plate of the C-shaped part is provided with a threaded hole matching the locking stud, and the bottom plate of the C-shaped part is provided with a through hole on the same vertical line as the threaded hole of the top plate; the side of the limit block is provided with a protrusion, and the limit blocks are arranged in pairs on the bottom plate of the C-shaped part in a mirror-image manner, and the protrusions are kept on the horizontal inner side.

3. The hysteresis and magnetostriction performance testing system under stress loading according to claim 1, characterized in that: A pair of support seats are provided in the middle of the mounting plate, the U-shaped yoke is placed on the support seats, and the legs of the U-shaped yoke are kept upward and attached to the lower surface of the test section of the plate-shaped specimen; a plurality of groups of mounting holes are provided in an array on the left side of the mounting plate, support feet are provided at the top corners of the mounting plate, and two reinforced square tubes are axially arranged below the mounting plate.

4. The hysteresis and magnetostriction performance testing system under stress loading according to claim 3, characterized in that: The mounting plate, T-shaped piece, fixture, L-shaped piece, sliding module, cushion block, support seat, support foot and reinforced square tube are all made of non-ferromagnetic materials.

5. The hysteresis and magnetostriction performance testing system under stress loading according to claim 1, characterized in that: The electric push rod is internally driven by a servo motor, the electric push rod is electrically connected to the computer through the driver, and the pressure sensor is electrically connected to the computer.

6. A method for testing a hysteresis and magnetostriction performance testing system under stress loading, characterized in that: The following steps are involved: Step 1: Specimen preparation: After demagnetizing and cleaning the plate specimen, two strain gauges are selected and attached in parallel to the surface of the test section of the plate specimen. One of the strain gauges is directly fixed with an adhesive as a test gauge, and the other strain gauge is attached with tape as a compensation gauge. Step 2: Assemble the system, use the computer to control the extension length of the electric push rod through the driver, so that the distance between the two fixtures matches the length of the plate-like specimen; put the clamping section of the specimen into the fixture, keep the strain gauge on the lower surface of the plate-like specimen, and then put the pressure blocks on them respectively, tighten the locking studs, and press the plate-like specimen; connect the test piece and the compensation piece to the strain bridge box with wires respectively, and the connection method adopts the half-bridge method with anti-interference effect; Step 3: Parameter setting: setting the acquisition parameters of the dynamic signal acquisition instrument on the computer and performing initialization processing; Step 4: Stress loading and signal acquisition: Set the stress target value on the computer, control the electric push rod to drive the right fixture to move, and apply stress to the specimen. When the pressure sensor detects that the stress reaches the target value, the servo motor's constant torque output mode is used to keep the stress constant. After the strain waveform is stable, the strain data of the specimen under stress loading is collected. Step 5: Magnetic field loading and signal acquisition: select a sine wave on the signal generator, set the amplitude and frequency, and then output the excitation signal. After the waveform on the dynamic signal acquisition instrument is stable, synchronously collect the strain data, sampling resistor voltage, and integral capacitor voltage of the specimen under stress and magnetic field loading; Step 6: Data processing, filtering the strain data, sampling resistor voltage and integral capacitor voltage collected in steps 4 and 5; taking the average value of the processed strain data of step 4 as the initial strain; subtracting the initial strain from the processed strain data of step 5 to obtain the magnetostrictive strain under the stress state; converting the processed sampling resistor voltage and integral capacitor voltage into magnetic field intensity and magnetic induction intensity using formula (1) and formula (2) respectively, the formula is: in, H is the magnetic field strength, A / m; N 1 is the number of turns of the exciting coil; L is the length of the closed magnetic circuit, m; R 1 is the resistance value of the sampling resistor, Ω; U 1 is the sampling resistor voltage, V; B is the magnetic induction intensity, T; R 2 is the resistance value of the integrating resistor, Ω; C is the capacitive reactance of the integrating capacitor, F; N 2 is the number of turns of the detection coil; S is the cross-sectional area of ​​the U-shaped yoke, m 2 ; U 2 is the integrating capacitor voltage, V; Step 7: Curve drawing. Finally, the magnetostriction curve and hysteresis loop are drawn with the magnetic field intensity as the horizontal coordinate and the magnetostriction strain and magnetic induction intensity as the vertical coordinate.

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