Circumferential radiation magnetizing electromagnetic ultrasonic transducer for high-temperature nondestructive monitoring and design method

Abstract

The invention belongs to the technical field of electromagnetic ultrasonic transducers, and provides a high-temperature nondestructive monitoring circumferential radiation magnetizing electromagnetic ultrasonic transducer and a design method, and the main scheme is that the electromagnetic ultrasonic transducer comprises eight fan-shaped permanent magnets, a cylindrical magnetic core and a butterfly coil, the central angle of each permanent magnet in the eight fan-shaped permanent magnets is 45 degrees, the eight fan-shaped permanent magnets are spliced to form a circular ring to wrap the cylindrical magnetic core, the butterfly-shaped coil is arranged under the cylindrical magnetic core, the magnetization direction of each permanent magnet points to the circle center, and after the eight fan-shaped permanent magnets are spliced to form the circular ring to wrap the cylindrical magnetic core, the butterfly-shaped coil is arranged under the cylindrical magnetic core. The cylindrical magnetic core is magnetized in the axial direction, and the magnetic flux of each fan-shaped permanent magnet is overlapped and converged in the magnetic core. According to the invention, the ultrasonic amplitude can be improved, and the device can work stably in a high-temperature environment.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic ultrasonic transducers, and in particular to a circumferential radiation magnetized electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring and a design method thereof. Background Art

[0002] In the oil and gas industry, in order to ensure pipeline safety and avoid catastrophic explosions, the traditional method is to shut down and overhaul at room temperature, but this will cause huge economic losses. The introduction of non-destructive monitoring equipment will help to detect defects more promptly and improve economic benefits. Electromagnetic ultrasonic technology is increasingly used in structural health monitoring, industrial pipeline safety assessment and other fields due to its non-destructive nature, ability to detect through coatings, no need for coupling agents, and easy installation. However, the weak signal-to-noise ratio and low operating temperature of electromagnetic ultrasound severely limit its application in harsh high-temperature environments (>500°C). Industrial scenarios such as oil refining, chemical plants, and nuclear power plants inevitably involve high-temperature and high-pressure environments, and there are more pipeline equipment working in these environments, which poses greater safety risks and greater monitoring needs.

[0003] The basic structure of electromagnetic ultrasonic probe is as follows Figure 1 As shown in Figure 1, it consists of a unidirectionally polarized permanent magnet and an excitation coil. When high-frequency alternating current J1 is passed through the excitation coil, eddy current J1 is induced on the surface of the metal specimen. e , the moving charged particle is subjected to the alternating Lorentz force F under the action of the bias magnetic field B0 L The interaction between charged particles and surrounding structures forms ultrasonic waves. When ultrasonic waves are transmitted downward and encounter defects or bottom surface reflection, the ultrasonic waves carrying the specimen information return to the specimen surface. The mechanical vibration of the particles cuts the magnetic flux lines, and eddy currents are induced on the specimen surface again and received by the coil.

[0004] Electromagnetic ultrasonic technology is based on the electromagnetic induction mechanism. It directly generates ultrasonic waves in the test piece through electromagnetic field coupling. The energy is converted back and forth between the electromagnetic field and the acoustic field, resulting in low transducer efficiency. The traditional electromagnetic ultrasonic transducer consists of a permanent magnet and an excitation / receiving coil. For a permanent magnet, when the temperature is less than the Curie temperature, the residual magnetic induction intensity of the permanent magnet will lose a certain percentage for every 1°C increase in temperature, namely the residual magnetic temperature coefficient. At the same time, as the temperature increases, the change in the performance of the test piece will also increase the noise, and the signal-to-noise ratio will be further weakened. Electromagnetic ultrasonic transducer technology has the advantages of non-invasiveness, non-contact, allowing for a lifting distance, and easy installation. It is widely used in structural health monitoring, industrial pipeline safety assessment and other fields. However, the weak signal-to-noise ratio of this technology and the low operating temperature of the permanent magnet greatly limit the application of electromagnetic ultrasonic technology in high temperature monitoring scenarios (>500°C). In order to improve the signal-to-noise ratio of the electromagnetic ultrasonic transducer, the commonly used methods are (1) enhancing the efficiency of the excitation power supply; (2) enhancing the bias magnetic field strength. Summary of the invention

[0005] The purpose of the present invention is to provide a circular radiation magnetized electromagnetic ultrasonic transducer and a design method for high-temperature non-destructive monitoring, which can increase the ultrasonic amplitude and thus improve the signal-to-noise ratio, and can work stably in a high-temperature environment.

[0006] The present invention solves the technical problem and adopts the following technical solution: In one aspect, the present invention provides a circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring, comprising: Eight sector-shaped permanent magnets, cylindrical cores and butterfly coils; The central angle of each of the eight sector-shaped permanent magnets is 45 degrees. The eight sector-shaped permanent magnets are spliced ​​to form a ring to wrap the cylindrical magnetic core, and the butterfly coil is arranged directly below the cylindrical magnetic core; the magnetization direction of each permanent magnet points to the center of the circle; After eight sector-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized with the magnetization direction being axial, and the magnetic flux of each sector-shaped permanent magnet is superimposed and converged in the magnetic core.

[0007] As a further optimization, each of the eight sector-shaped permanent magnets has a wall thickness of 10 mm and a height of 30 mm; The core radius of the cylindrical core is 5 mm, and the core height is 3 / 5 to 4 / 5 of the height of each permanent magnet; The diameter of the butterfly coil is 0.26 mm, the center spacing is 3 times the coil radius, and the number of coil turns is 13; The butterfly coil is 0.2 mm away from the lower surface of the cylindrical magnetic core.

[0008] As a further optimization, a test piece is arranged directly below the butterfly coil. The test piece is a rectangular parallelepiped with a length and a width of 45 mm and a height of 5 mm.

[0009] As a further optimization, the butterfly coil is 0.2 mm away from the upper surface of the test piece.

[0010] As a further optimization, the test piece is provided with an air domain, and the air domain is a cube with a side length 1.5 times the width of the test piece.

[0011] As a further optimization, Permalloy patches are attached to the bottom of the cylindrical magnetic core and the eight sector-shaped permanent magnets.

[0012] On the other hand, the present invention also provides a design method of a circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring, comprising the following steps: Obtain eight sector-shaped permanent magnets, a cylindrical magnetic core and a butterfly coil, wherein the central angle of each of the eight sector-shaped permanent magnets is 45 degrees; Eight fan-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, and the butterfly coil is arranged directly below the cylindrical magnetic core. The magnetization direction of each permanent magnet points to the center of the circle. After eight sector-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized with the magnetization direction being axial, and the magnetic flux of each sector-shaped permanent magnet is superimposed and converged in the magnetic core.

[0013] As a further optimization, after the eight sector-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, the following is also included: Parameter scanning is performed using finite element simulation software, wherein the parameters include the wall thickness and height of each of the eight sector-shaped permanent magnets, and the core radius and core height of the cylindrical magnetic core; The parameter scanning results are used to optimize the dimensions of the eight sector-shaped permanent magnets and the cylindrical magnetic core to obtain the optimal dimensions.

[0014] As a further optimization, after obtaining the optimal size, it also includes: According to the mode of the ultrasonic wave excited by the electromagnetic ultrasonic transducer, the size and number of turns of the butterfly coil are designed; Permalloy patches are attached under the cylindrical magnetic core and eight sector-shaped permanent magnets.

[0015] As a further optimization, after the cylindrical core and the eight sector-shaped permanent magnets are all covered with Permalloy patches, the following are also included: The performance improvement and stability results of the electromagnetic ultrasonic transducer are verified under normal temperature and high temperature environments.

[0016] The beneficial effects of the present invention are: through the above-mentioned circumferential radiation magnetization electromagnetic ultrasonic transducer and design method for high-temperature non-destructive monitoring, the signal-to-noise ratio of the circumferential radiation magnetization electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring can be significantly improved, and the allowable lifting distance of the probe is increased, and the stability of working in a high temperature environment (>500°C) can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a basic structural diagram of the background technology and the conventional electromagnetic ultrasonic probe in Embodiment 3 of the present invention; Figure 2 This is a schematic diagram of the structural design principle of the circular radiation electromagnetic ultrasonic transducer in Example 3 of the present invention; Figure 3 It is a three-dimensional principle diagram of CRM-EMAT in Example 3 of the present invention; Figure 4 Schematic diagram of magnetic flux density distribution of CRM-EMAT in Example 3 of the present invention; Figure 5Schematic diagram of the comparison results of the magnetic flux density norm of CRM-EMAT and single magnet EMAT on the sampling section line in Example 3 of the present invention; Figure 6 Schematic diagram of scanning results of the magnetic core radius and the magnet wall thickness at the sampling point in Example 3 of the present invention; Figure 7 Schematic diagram of the scanning result of the magnetic core height at the sampling point in Example 3 of the present invention; Figure 8 Schematic diagram of scanning results of magnet height at sampling points in Example 3 of the present invention; Fig. 9 Schematic diagram of a two-dimensional axisymmetric numerical simulation model of a single magnet EMAT (left) and a CRM-EMAT (right) in Example 3 of the present invention; Fig.10 The ultrasonic motion cloud diagrams of the single magnet EMAT (left) and CRM-EMAT (right) in the specimen at 8.75 microseconds in Example 3 of the present invention; Fig.11 Schematic diagram of simulation signal comparison between single magnet EMAT and CRM-EMAT in Example 3 of the present invention; Fig.12 This is a schematic diagram of a normal temperature experimental platform in Example 3 of the present invention; Fig.13 The noise shielding effect of the Permalloy patch in Example 3 of the present invention Fig.14 Schematic diagram of signal comparison between CRM-EMAT of different sizes and single magnet EMAT in Example 3 of the present invention; Fig.15 Schematic diagram of the effect of lift-off distance on signal amplitude in Example 3 of the present invention; Fig.16 This is a schematic diagram of a high temperature experimental platform in Example 3 of the present invention; Fig.17 Schematic diagram of ultrasonic echo signals at different temperatures in Example 3 of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations. Example 1

[0019] This embodiment provides a circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring, including: Eight sector-shaped permanent magnets, cylindrical cores and butterfly coils; The central angle of each of the eight sector-shaped permanent magnets is 45 degrees. The eight sector-shaped permanent magnets are spliced ​​to form a ring to wrap the cylindrical magnetic core, and the butterfly coil is arranged directly below the cylindrical magnetic core; the magnetization direction of each permanent magnet points to the center of the circle; After eight sector-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized with the magnetization direction being axial, and the magnetic flux of each sector-shaped permanent magnet is superimposed and converged in the magnetic core.

[0020] In order to improve the bias magnetic field strength of the probe and thus improve the signal-to-noise ratio and operating temperature of the electromagnetic ultrasonic signal, this embodiment utilizes the characteristics of soft iron that is easy to be magnetized and has high magnetic permeability. In the magnet package, the magnetic core is first magnetized in the axial direction. Secondly, the magnetic flux of the surrounding magnets converges in the magnetic core. The overall magnetic flux density of the electromagnetic ultrasonic transducer (i.e., the probe) reaches 3.18T in the axial direction of the magnetic core. Compared with Figure 1 The single N52NdFeB magnet is about 1.4T, which is increased by nearly 2.3 times.

[0021] Considering that the volume of the probe is not too large, the wall thickness of each of the eight sector-shaped permanent magnets is 10 mm and the height is 30 mm; the core radius of the cylindrical magnetic core is 5 mm, and the core height is 3 / 5 to 4 / 5 of the height of each permanent magnet; The probe in this embodiment is used to excite ultrasonic shear waves, so the coil is designed as a butterfly coil. The middle straight part is the effective area, which is located directly below the magnetic core. The effective area of ​​the coil should be larger than the diameter of the magnetic core to maximize the use of the bias magnetic field. Therefore, the diameter of the butterfly coil is 0.26 mm, the center spacing is 3 times the coil radius, and the number of coil turns is 13 turns; the butterfly coil is 0.2 mm away from the lower surface of the cylindrical magnetic core.

[0022] In actual application, a test piece is set directly below the butterfly coil. The test piece is a cuboid with a length and width of 45 mm and a height of 5 mm. The butterfly coil is 0.2 mm away from the upper surface of the test piece. The test piece is provided with an air space, which is a cube with a side length 1.5 times the width of the test piece.

[0023] In order to prevent the eddy current induced in the magnetic core from causing crosstalk to the coil signal, Permalloy patches are attached under the cylindrical magnetic core and the eight sector-shaped permanent magnets for electromagnetic shielding. Example 2

[0024] Based on Example 1, this embodiment provides a design method for a circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring, comprising the following steps: S1. Obtain eight sector-shaped permanent magnets, a cylindrical magnetic core and a butterfly coil, wherein the central angle of each of the eight sector-shaped permanent magnets is 45 degrees; S2. Splice eight sector-shaped permanent magnets into a ring to wrap the cylindrical magnetic core, and arrange the butterfly coil directly below the cylindrical magnetic core. The magnetization direction of each permanent magnet points to the center of the circle. S3. After eight sector-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized in the axial direction, and the magnetic flux of each sector-shaped permanent magnet is superimposed and converged in the magnetic core.

[0025] In practical application, after the eight sector-shaped permanent magnets are spliced ​​to form a ring to wrap the cylindrical magnetic core, the following may also be included: Parameter scanning is performed using finite element simulation software, wherein the parameters include the wall thickness and height of each of the eight sector-shaped permanent magnets, and the core radius and core height of the cylindrical magnetic core; The parameter scanning results are used to optimize the dimensions of the eight sector-shaped permanent magnets and the cylindrical magnetic core to obtain the optimal dimensions.

[0026] In addition, after obtaining the optimal size, it can also include: According to the mode of the ultrasonic wave excited by the electromagnetic ultrasonic transducer, the size and number of turns of the butterfly coil are designed; Permalloy patches are attached under the cylindrical magnetic core and eight sector-shaped permanent magnets.

[0027] Finally, after the cylindrical core and the eight sector-shaped permanent magnets are all attached with Permalloy patches, the following can also be included: The performance improvement and stability results of the electromagnetic ultrasonic transducer are verified under normal temperature and high temperature environments. Example 3

[0028] On the basis of Example 1 and Example 2, the circumferential radiation magnetized electromagnetic ultrasonic transducer (CRM-EMAT for short) for high temperature non-destructive monitoring of this embodiment is composed of a cylindrical silicon steel core wrapped with eight permanent magnets magnetized in a circumferential radial manner, and a Permalloy sheet is bonded to the lower surface of the probe. This configuration significantly improves the signal-to-noise ratio of the probe and increases the allowable lift-off distance of the probe, providing a solution to the structural monitoring problem of electromagnetic ultrasonic technology in a high temperature environment (>500°C, especially 600°C).

[0029] In this embodiment, first, the magnetic concentration principle is explained and the probe size is optimized through finite element simulation; then, the performance improvement effect of the probe is explained through comparative experiments and lift-off experiments under normal temperature; finally, the stability of the probe under 500°C environment is verified through high temperature experiments.

[0030] The basic structure of commonly used electromagnetic ultrasonic probes is as follows: Figure 1 As shown in Figure 1, it consists of a unidirectionally polarized permanent magnet and an excitation coil. When high-frequency alternating current J1 is passed through the excitation coil, eddy current J1 is induced on the surface of the metal specimen. e , the moving charged particle is subjected to the alternating Lorentz force F under the action of the bias magnetic field B0 L The interaction between charged particles and surrounding structures forms ultrasonic waves. When ultrasonic waves are transmitted downward and encounter defects or bottom surface reflections, the ultrasonic waves carrying the specimen information return to the specimen surface. The mechanical vibration of the particles cuts the magnetic flux lines, and the specimen surface induces eddy currents again, which are received by the coil. Under the premise of not changing the volume of the probe, in order to enhance the bias magnetic field density, this embodiment provides a circumferential radiation magnetized electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring, which is configured as follows: Figure 2 As shown, eight sector-shaped permanent magnets with polarization directions pointing to the center of the circle wrap a cylindrical soft iron core, and each magnet faces the core with the same magnetic pole, and the magnetic fields converge and overlap in the magnetized soft iron core.

[0031] To verify and predict the enhancement effect of the bias magnetic field, a Figure 3 The three-dimensional schematic model of CRM-EMAT shown in the figure is numerically simulated and analyzed. The simulation model consists of CRM magnetic group, iron core, butterfly coil, specimen and air domain (hidden in the figure). The core radius is 5mm and the height is 20mm; the central angle of a single magnet is 45°, the height is 20mm, the thickness is 10mm (i.e., outer diameter minus inner diameter), and a total of 8 pieces form a ring; the excitation and receiving integrated coil is a butterfly coil with a diameter of 0.26mm, a center spacing of 3 times the coil radius, 13 turns of coils, and the distance between the coil and the lower surface of the core and the upper surface of the specimen (i.e., the lifting distance) is 0.2mm; the length and width of the specimen are 45mm and the height is 5mm; the air domain is set as a cube with a side length of 1.5 times the width of the specimen. The material properties of each part are shown in Table I. Since the magnetic permeability of the soft iron core changes with the magnetic field intensity, the magnetization model uses the BH curve in the multi-physics simulation software library. Here, we first conduct a steady-state study on the model. We only need to add the magnetic field physics field, complete the corresponding magnetization model configuration for the permanent magnet and the iron core, and add the coil geometry analysis step before the steady-state analysis to analyze the magnetic flux density distribution of the CRM-EMAT as follows: Figure 4 As shown, the radial magnetic flux is vertically concentrated in the core, with the maximum value reaching 3.18T, which is located at the lower edge of the core.

[0032] Table I

[0033] Next, we compared the optimization effect of the probe and explored the optimal size of CRM-EMAT. Due to the skin effect, the induced eddy current only exists on the shallow surface of the specimen, and the skin depth is It can be calculated using formula (1), where f is the excitation frequency, is the magnetic permeability, is the electrical conductivity of the conducting material.

[0034] With each skin depth, the electromagnetic wave decays to 1 / e of the original amplitude inside the conductor. Therefore, the bias magnetic field mainly acts at about 3 skin depths, with the center of the magnetic core as the center, on the lower surface of the specimen. Take a section line at the location, calculate the magnetic flux density distribution on the section line, and compare it with a cylindrical single magnet of the same volume. The results are as follows Figure 5 As shown, for the CRM-EMAT structure, the magnetic flux density in the core area is greatly improved, with a maximum value of 1.65T. Extending outward from just below the center of the core, the best detection range can be obtained, while the maximum value of the traditional single magnet structure is only 0.7T, and the magnetic flux density is increased by nearly 2.4 times.

[0035] Subsequently, a parametric scanning step was added to the study to scan the four parameters of core radius, magnet thickness, core height, and magnet height. When one parameter is changed, the other parameters remain unchanged. In this embodiment, the core radius is first scanned with a step length of 4mm, from 4mm to 52mm; then the magnet thickness is scanned with a step length of 5mm, from 5mm to 50mm. The midpoint of the intercept is taken as the sampling point, and its magnetic flux density is calculated. The results are as follows Figure 6 As shown in the figure, as the thickness of the magnet increases, the magnetic flux density increases, but when the magnet thickness is greater than 20mm, the increase begins to decrease; conversely, as the core radius increases, the magnetic flux density decreases, but considering the detection range, the core radius should not be too small. Then the core height is scanned, increasing from 4mm to 24mm in steps of 2mm. The results are as follows: Figure 7 As shown in Figure 1, the magnetic flux density reaches its maximum when the core height is 3 / 5 to 4 / 5 of the magnet height, rather than when it is flush with the magnet. Finally, scan the magnet height, see Figure 8 , with a step length of 5mm from 15mm to 60mm, the magnetic flux density increases with the increase of the magnet height. When the magnet height is greater than 30mm, the magnetic flux density increases slightly, but from the vertical axis of the result, the influence of radius on the magnetic flux density is more significant.

[0036] Next, a transient study is added to the model to analyze the ultrasonic signal and its propagation in the specimen. In order to improve the computational efficiency, a two-dimensional axisymmetric model is used, such as Fig. 9As shown, the left side is an equal volume single magnet EMAT structure, and the right side is a CRM-EMAT structure, with r=0 as the axis. The magnetic field distribution is the same as the three-dimensional model described above. In actual production, the purpose of dividing the CRM ring magnet into eight equal parts is to facilitate radiation magnetization. The coil shape will not affect the signal amplitude, so the impact of the change in coil shape is ignored here. In order to successfully analyze the ultrasonic waveform, when the grid is divided, the maximum grid in the specimen shall not exceed 1 / 10 of the shear wave wavelength. In this embodiment, the Lorentz force transduction mechanism is mainly considered, and the main ultrasonic type is shear wave. A pulse modulated current with a frequency of 3MHz and an amplitude of 20A is passed into the coil. The function equation is as follows, where gp(t) is a Gaussian pulse function, f 0 is the frequency, T 0 For cycle.

[0037] Fig.10 The ultrasonic motion comparison of the two probe structures in the specimen at 10.4ms is shown. The stress on the specimen in the CRM-EMAT model is significantly greater than that in the EMAT with a single magnet structure. According to the ultrasonic motion and the velocity characteristics of each type of wave, Fig.10 Surface waves, longitudinal waves, shear waves and LS mode conversion waves can be distinguished, which helps to analyze the echo signal. Fig.11 As shown in the figure, compared with the single magnet structure, CRM-EMAT increases the amplitude by nearly 10 times and can receive waveforms of other modes.

[0038] In the experimental part, we first conducted a Permalloy patch experiment, a comparative experiment, and a lift-off distance experiment at room temperature. Fig.12 As shown in the figure, the experimental platform consists of CRM-EMAT, test piece, monitoring motherboard and display screen. The test piece is a 7.33mm thick steel plate. Three sizes of CRM permanent magnets are processed, with thickness-height of 10-20mm, 10-30mm and 15-30mm respectively. The material is Sm2Co 17 (The reversible working temperature of the residual magnetism is 350℃, and the Curie temperature is 850℃). The core radius is 5mm, and the height is 7 / 10 of the magnet height (i.e. 14mm and 21mm). The material is silicon steel. The experimental data can be uploaded to the cloud through the MCU's 4G module, directly obtained remotely on the web page, or directly exported through the serial port transmission.

[0039] Fig.13The results of the Permalloy patch experiment show that Permalloy has a high weak magnetic field permeability. When the Permalloy patch is not applied, the coil induced magnetic field crosstalks into the silicon steel magnet to generate interference waves. After the Permalloy patch is applied, the interference waves disappear, indicating that the Permalloy patch prevents the coil induced magnetic field from entering the magnetic core and magnet, thereby shielding the interference waves. In the comparative experiment, the echo signals generated by the EMAT of a single cylindrical magnet with a diameter of 40mm and a height of 30mm were compared with the three sizes of CRM-EAMT. Fig.14 As shown, the results are consistent with the simulation results. Increasing the thickness and height of the magnet will increase the magnetic flux density and thus the amplitude, and the thickness of the magnet has a greater effect. Compared with the single-magnet EMAT, the amplitude of CRM-EMAT is increased by about 6 times. This is due to the fact that the lift-off distance in the actual experiment is larger than the simulation and other environmental factors.

[0040] In the lift-off experiment, the lift-off distances were set at 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm. Fig.15 It can be seen from the signal amplitude that the signal amplitude decreases by about half for every 0.5mm increase in the lifting distance. When the lifting distance is 1mm, the signal amplitude is slightly greater than Fig.14 Due to the single magnet structure in the CRM-EMAT, the lift-off distance is increased by about 1mm, allowing a working lift-off distance of 2mm.

[0041] Finally, high temperature experiments were carried out on CRM-EMAT. Fig.16 As shown in the figure, the specimen is heated by a heating furnace. The coil uses a ceramic substrate PCB and the conductor uses mica wrapped wire to adapt to the high temperature monitoring environment. The signal is collected every 100℃. The results are shown in the figure below. Fig.17 As shown in the figure, as the temperature rises, the propagation speed of ultrasound in the specimen slows down and the signal amplitude gradually decreases. When the temperature exceeds 350°C, the residual magnetism of the samarium-cobalt magnet begins to produce some irreversible losses, but due to the circumferential magnet-core design of the CRM-EMAT probe, the residual magnetism strength still meets the good excitation and reception of the signal. Therefore, at 500°C, the echo signal is still clear and stable.

[0042] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A circular radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring, characterized in that: include: Eight sector-shaped permanent magnets, cylindrical cores and butterfly coils; The central angle of each of the eight sector-shaped permanent magnets is 45 degrees. The eight sector-shaped permanent magnets are spliced ​​to form a ring to wrap the cylindrical magnetic core, and the butterfly coil is arranged directly below the cylindrical magnetic core; the magnetization direction of each permanent magnet points to the center of the circle; After eight sector-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized with the magnetization direction being axial, and the magnetic flux of each sector-shaped permanent magnet is superimposed and converged in the magnetic core.

2. The circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring according to claim 1, characterized in that: Each of the eight sector-shaped permanent magnets has a wall thickness of 10 mm and a height of 30 mm; The core radius of the cylindrical core is 5 mm, and the core height is 3 / 5 to 4 / 5 of the height of each permanent magnet; The diameter of the butterfly coil is 0.26 mm, the center spacing is 3 times the coil radius, and the number of coil turns is 13; The butterfly coil is 0.2 mm away from the lower surface of the cylindrical magnetic core.

3. The circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature nondestructive monitoring according to claim 1, characterized in that: A test piece is arranged directly below the butterfly coil. The test piece is a cuboid with a length and a width of 45 mm and a height of 5 mm.

4. The circular radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring according to claim 3 is characterized in that: The butterfly coil is 0.2 mm away from the upper surface of the test piece.

5. The circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring according to claim 3, characterized in that: The test piece is provided with an air domain, and the air domain is a cube with a side length 1.5 times the width of the test piece.

6. The circular radiation magnetized electromagnetic ultrasonic transducer for high temperature nondestructive monitoring according to any one of claims 1 to 5, characterized in that: Permalloy patches are attached to the bottom of the cylindrical magnetic core and the eight sector-shaped permanent magnets.

7. A design method for a circumferential radiation magnetization electromagnetic ultrasonic transducer for high temperature nondestructive monitoring, applied to the circumferential radiation magnetization electromagnetic ultrasonic transducer for high temperature nondestructive monitoring as claimed in any one of claims 1 to 6, characterized in that: The steps include: Obtain eight sector-shaped permanent magnets, a cylindrical magnetic core and a butterfly coil, wherein the central angle of each of the eight sector-shaped permanent magnets is 45 degrees; Eight fan-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, and the butterfly coil is arranged directly below the cylindrical magnetic core. The magnetization direction of each permanent magnet points to the center of the circle. After eight sector-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized with the magnetization direction being axial, and the magnetic flux of each sector-shaped permanent magnet is superimposed and converged in the magnetic core.

8. The design method of the circular radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring according to claim 7 is characterized in that: After the eight sector-shaped permanent magnets are spliced ​​together to form a ring to wrap the cylindrical magnetic core, the following further comprises: Parameter scanning is performed using finite element simulation software, wherein the parameters include the wall thickness and height of each of the eight sector-shaped permanent magnets, and the core radius and core height of the cylindrical magnetic core; The parameter scanning results are used to optimize the dimensions of the eight sector-shaped permanent magnets and the cylindrical magnetic core to obtain the optimal dimensions.

9. The design method of the circular radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring according to claim 8 is characterized in that: After obtaining the optimal size, it also includes: According to the mode of the ultrasonic wave excited by the electromagnetic ultrasonic transducer, the size and number of turns of the butterfly coil are designed; Permalloy patches are attached under the cylindrical magnetic core and eight sector-shaped permanent magnets.

10. The design method of the circular radiation magnetization electromagnetic ultrasonic transducer for high temperature non-destructive monitoring according to claim 9, characterized in that: After the cylindrical core and eight sector-shaped permanent magnets are all covered with Permalloy patches, the following parts are also included: The performance improvement and stability results of the electromagnetic ultrasonic transducer are verified under normal temperature and high temperature environments.

Images