Circumferential Radiation Magnetizing Electromagnetic Ultrasonic Transducer for High-Temperature Non-Destructive Monitoring and Design Method

Abstract

The present invention belongs to the technical field of electromagnetic ultrasonic transducers, and proposes a circumferential radiation magnetized electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring and a design method. The main solution is as follows: The electromagnetic ultrasonic transducer includes eight sector-shaped permanent magnets, a cylindrical magnetic core, and a butterfly coil. Among them, the central angle of each permanent magnet in 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. The butterfly coil is arranged directly below the cylindrical magnet. The magnetization direction of each permanent magnet points to the center of the circle. After the eight sector-shaped permanent magnets are spliced to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized, and the magnetization direction is axial. The magnetic fluxes of each sector-shaped permanent magnet are superimposed and converged in the magnetic core. The present invention can improve the ultrasonic amplitude and can work stably in a high-temperature environment.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic ultrasonic transducers, and particularly 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 for maintenance in a normal temperature environment, but this will cause huge economic losses. The introduction of non-destructive monitoring equipment helps to detect defects more timely and improve economic benefits. Due to its non-destructive nature, the electromagnetic ultrasonic technology can detect through coatings, does not require a coupling agent, and is easy to install, so it is increasingly applied in fields such as structural health monitoring and industrial pipeline safety assessment. However, the weak signal-to-noise ratio and low operating temperature of electromagnetic ultrasound seriously limit its application in harsh high-temperature environments (>500°C). Industrial scenarios such as oil refining, chemical plants, and nuclear power plants inevitably generate high-temperature and high-pressure environments, and there are more pipeline equipment working in these environments, with greater potential safety hazards and greater monitoring needs.

[0003] The basic structure of an electromagnetic ultrasonic probe is as Figure 1 shown, consisting of a unidirectionally polarized permanent magnet and an exciting coil. When a high-frequency alternating current J 1 is passed through the exciting coil, eddy current J e is induced on the surface of the metal specimen. The moving charged particles are subjected to an alternating Lorentz force F 0 under the action of the bias magnetic field B L . The interaction between the charged particles and the surrounding structure forms ultrasonic waves. When the ultrasonic waves are conducted downward and encounter a defect or the bottom surface and are reflected, when the ultrasonic waves carrying the specimen information return to the specimen surface, the mechanical vibration of the particles cuts the magnetic induction line, and eddy current is induced again on the specimen surface and received by the coil.

[0004] Electromagnetic ultrasonic technology is based on the mechanism of electromagnetic induction, directly generating 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 conversion efficiency. Traditional electromagnetic ultrasonic transducers consist of permanent magnets and excitation / receiving coils. For permanent magnets, when the temperature is below the Curie temperature, for every 1°C increase in temperature, the residual magnetic induction intensity of the permanent magnet will lose a certain percentage, that is, the temperature coefficient of remanence. At the same time, as the temperature rises, the change in the performance of the test piece will also increase the noise, further weakening the signal-to-noise ratio. Electromagnetic ultrasonic transducer technology has the advantages of non-invasiveness, non-contact, allowing lift-off distance, and easy installation, and is widely used in fields such as structural health monitoring and industrial pipeline safety assessment. However, the weak signal-to-noise ratio of this technology and the low operating temperature of permanent magnets greatly limit the application of electromagnetic ultrasonic technology in high-temperature monitoring scenarios (>500°C). To improve the signal-to-noise ratio of electromagnetic ultrasonic transducers, common methods include (1) enhancing the efficiency of the excitation power supply; (2) enhancing the bias magnetic field intensity. Summary of the Invention

[0005] The object of the present invention is to provide a circumferential radiation magnetized electromagnetic ultrasonic transducer and a design method for high-temperature non-destructive monitoring, which can improve the ultrasonic amplitude, thereby increasing the signal-to-noise ratio, and can operate stably in a high-temperature environment.

[0006] To solve its technical problems, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a circumferential radiation magnetized electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring, including:

[0008] Eight sector-shaped permanent magnets, a cylindrical magnetic core, and a butterfly coil;

[0009] 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 magnet; the magnetization direction of each permanent magnet points to the center of the circle;

[0010] After the eight sector-shaped permanent magnets are spliced to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized, and the magnetization direction is axial. The magnetic fluxes of each sector-shaped permanent magnet are superimposed and converge in the magnetic core.

[0011] As a further optimization, the wall thickness of each of the eight sector-shaped permanent magnets is 10 mm, and the height is 30 mm;

[0012] The magnetic core radius of the cylindrical magnetic core is 5 mm, and the magnetic core height is 3 / 5 to 4 / 5 of the height of each permanent magnet;

[0013] 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;

[0014] The butterfly-shaped coil is 0.2 mm away from the lower surface of the cylindrical magnetic core.

[0015] As a further optimization, a test piece to be tested is arranged directly below the butterfly-shaped coil. The test piece to be tested is a cuboid with a length and width of 45 mm each and a height of 5 mm.

[0016] As a further optimization, the butterfly-shaped coil is 0.2 mm away from the upper surface of the test piece to be tested.

[0017] As a further optimization, the test piece to be tested 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 to be tested.

[0018] As a further optimization, Permalloy patches are pasted below both the cylindrical magnetic core and the eight sector-shaped permanent magnets.

[0019] On the other hand, the present invention also provides a design method for a circumferential radiation magnetizing electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring, including the following steps:

[0020] Obtain eight sector-shaped permanent magnets, a cylindrical magnetic core, and a butterfly-shaped coil. The central angle of each permanent magnet among the eight sector-shaped permanent magnets is 45 degrees;

[0021] Splice the eight sector-shaped permanent magnets to form a ring to wrap the cylindrical magnetic core, and arrange the butterfly-shaped coil directly below the cylindrical magnet. The magnetization direction of each permanent magnet points to the center of the circle;

[0022] After the eight sector-shaped permanent magnets are spliced to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized, and the magnetization direction is axial. The magnetic fluxes of each sector-shaped permanent magnet are superimposed and converged in the magnetic core.

[0023] As a further optimization, after the eight sector-shaped permanent magnets are spliced to form a ring to wrap the cylindrical magnetic core, it further includes:

[0024] Perform parameter scanning using finite element simulation software. The parameters include the wall thickness and height of each permanent magnet among the eight sector-shaped permanent magnets, the core radius and core height of the cylindrical magnetic core;

[0025] Optimize the sizes of the eight sector-shaped permanent magnets and the cylindrical magnetic core using the parameter scanning results to obtain the optimal sizes.

[0026] As a further optimization, after obtaining the optimal sizes, it further includes:

[0027] Design the size and number of turns of the butterfly-shaped coil according to the mode of the ultrasonic wave excited by the electromagnetic ultrasonic transducer;

[0028] Paste Permalloy patches below both the cylindrical magnetic core and the eight sector-shaped permanent magnets.

[0029] As a further optimization, after attaching permalloy patches to both the cylindrical magnetic core and the eight sector-shaped permanent magnets, it further includes:

[0030] Verifying the performance improvement results and stability results of the electromagnetic ultrasonic transducer under normal temperature environment and high temperature environment.

[0031] The beneficial effects of the present invention are: through the above-mentioned circumferential radiation magnetized electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring and the design method, the signal-to-noise ratio of the circumferential radiation magnetized electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring can be significantly improved, and moreover, the lift-off distance allowed by the probe is increased, and the stability of working under high temperature environment (>500 °C) can be achieved. Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the basic structure of the traditional electromagnetic ultrasonic probe in the background technology and Embodiment 3 of the present invention;

[0033] Figure 2 It is a schematic diagram of the structural design principle of the circumferential radiation electromagnetic ultrasonic transducer in Embodiment 3 of the present invention;

[0034] Figure 3 It is a three-dimensional schematic diagram of CRM-EMAT in Embodiment 3 of the present invention;

[0035] Figure 4 It is a schematic diagram of the magnetic flux density distribution of CRM-EMAT in Embodiment 3 of the present invention;

[0036] Figure 5 It is a schematic diagram of the comparison result of the magnetic flux density modulus of CRM-EMAT and single-magnet EMAT on the sampling cross-section in Embodiment 3 of the present invention;

[0037] Figure 6 It is a schematic diagram of the scanning result of the magnetic core radius and the magnet wall thickness at the sampling point in Embodiment 3 of the present invention;

[0038] Figure 7 It is a schematic diagram of the scanning result of the magnetic core height at the sampling point in Embodiment 3 of the present invention;

[0039] Figure 8 It is a schematic diagram of the scanning result of the magnet height at the sampling point in Embodiment 3 of the present invention;

[0040] Figure 9 It is a schematic diagram of the two-dimensional axisymmetric numerical simulation model of single-magnet EMAT (left) and CRM-EMAT (right) in Embodiment 3 of the present invention;

[0041] Figure 10 It is an ultrasonic motion cloud map of single-magnet EMAT (left) and CRM-EMAT (right) in a specimen at 8.75 microseconds in Embodiment 3 of the present invention;

[0042] Figure 11 Schematic diagram of the simulation signal comparison between the single-magnet EMAT and CRM-EMAT in Embodiment 3 of the present invention;

[0043] Figure 12 Schematic diagram of the normal-temperature experimental platform in Embodiment 3 of the present invention;

[0044] Figure 13 Noise shielding effect of the permalloy patch in Embodiment 3 of the present invention

[0045] Figure 14 Schematic diagram of the signal comparison between the CRM-EMAT and single-magnet EMAT with different sizes in Embodiment 3 of the present invention;

[0046] Figure 15 Schematic diagram of the influence of the lift-off distance on the signal amplitude in Embodiment 3 of the present invention;

[0047] Figure 16 Schematic diagram of the high-temperature experimental platform in Embodiment 3 of the present invention;

[0048] Figure 17 Schematic diagram of the ultrasonic echo signals at different temperatures in Embodiment 3 of the present invention. Detailed implementation manners

[0049] To make the objectives, 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 with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations. Embodiment 1

[0050] The circumferential-radiation magnetized electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring provided in this embodiment includes:

[0051] Eight sector-shaped permanent magnets, a cylindrical magnetic core, and a butterfly coil;

[0052] 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 magnet; the magnetization direction of each permanent magnet points to the center of the circle;

[0053] After the eight sector-shaped permanent magnets are spliced to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized, and the magnetization direction is axial. The magnetic fluxes of each sector-shaped permanent magnet are superimposed and converged in the magnetic core.

[0054] In order to increase the bias magnetic field intensity of the probe, thereby improving the signal-to-noise ratio and operating temperature of the electromagnetic ultrasonic signal, this embodiment utilizes the characteristics that soft iron is easily magnetized and has a high magnetic permeability. In the wrapping of the magnet, the magnetic core is first magnetized, and the magnetization direction is axial. Secondly, the magnetic fluxes of the surrounding magnets converge in the magnetic core, and the overall magnetic flux density of the electromagnetic ultrasonic transducer (i.e., the probe) reaches 3.18 T in the axial direction of the magnetic core. Compared with Figure 1 about 1.4 T of a single N52 NdFeB magnet in

[0055] Considering that the volume of the probe should not be too large, the wall thickness of each of the eight sector-shaped permanent magnets is 10 mm and the height is 30 mm; the radius of the magnetic core of the cylindrical magnetic core is 5 mm, and the height of the magnetic core is 3 / 5 to 4 / 5 of the height of each permanent magnet;

[0056] The probe in this embodiment is used to excite ultrasonic shear waves. Therefore, the coil is designed as a butterfly coil, and 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 utilization 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; the butterfly coil is 0.2 mm away from the lower surface of the cylindrical magnetic core.

[0057] In actual application, a specimen to be tested is arranged directly below the butterfly coil. The specimen to be tested is a cuboid, with the length and width of the cuboid both being 45 mm and the height being 5 mm; the butterfly coil is 0.2 mm away from the upper surface of the specimen to be tested. The specimen to be tested is provided with an air domain, and the air domain is a cube with a side length 1.5 times the width of the specimen to be tested.

[0058] In order to avoid the eddy current induced in the magnetic core from causing crosstalk to the coil signal, Permalloy patches are pasted below both the cylindrical magnetic core and the eight sector-shaped permanent magnets for electromagnetic shielding. Embodiment 2

[0059] Based on Embodiment 1, this embodiment provides a design method for a circumferential radiation magnetized electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring, including the following steps:

[0060] S1. Obtain eight sector-shaped permanent magnets, a cylindrical magnetic core, and a butterfly coil. The central angle of each of the eight sector-shaped permanent magnets is 45 degrees;

[0061] S2. Splice the eight sector-shaped permanent magnets to form a ring to wrap the cylindrical magnetic core, and arrange the butterfly coil directly below the cylindrical magnet. The magnetization direction of each permanent magnet points to the center of the circle;

[0062] S3. After eight sector-shaped permanent magnets are spliced to form a ring to wrap the cylindrical magnetic core, the cylindrical magnetic core is magnetized, and the magnetization direction is axial. The magnetic fluxes of each sector-shaped permanent magnet are superimposed and converged in the magnetic core.

[0063] In practical applications, after the eight sector-shaped permanent magnets are spliced to form a ring to wrap the cylindrical magnetic core, it may further include:

[0064] Using finite element simulation software for parameter scanning, the parameters include the wall thickness and height of each permanent magnet in the eight sector-shaped permanent magnets, the core radius and core height of the cylindrical magnetic core;

[0065] Using the parameter scanning results to optimize the sizes of the eight sector-shaped permanent magnets and the cylindrical magnetic core to obtain the optimal sizes.

[0066] In addition, after obtaining the optimal sizes, it may further include:

[0067] Designing the size and number of turns of the butterfly coil according to the mode of the ultrasonic wave excited by the electromagnetic ultrasonic transducer;

[0068] Pasting permalloy patches on both the cylindrical magnetic core and the eight sector-shaped permanent magnets.

[0069] Finally, after pasting permalloy patches on both the cylindrical magnetic core and the eight sector-shaped permanent magnets, it may further include:

[0070] Verifying the performance improvement results and stability results of the electromagnetic ultrasonic transducer in normal temperature environment and high temperature environment. Embodiment 3

[0071] Based on Embodiment 1 and Embodiment 2, the circumferential radiation magnetized electromagnetic ultrasonic transducer (abbreviation: CRM-EMAT) for high-temperature non-destructive monitoring in this embodiment is composed of eight permanent magnets magnetized in the circumferential radial direction to wrap a cylindrical silicon steel magnetic core, and a permalloy thin sheet is attached to the lower surface of the probe. This configuration significantly improves the signal-to-noise ratio of the probe and increases the lift-off distance allowed by the probe, providing a solution to the problem of structural monitoring of electromagnetic ultrasonic technology in high-temperature environments (>500 °C, especially 600 °C).

[0072] In this embodiment, first, through finite element simulation, the magnetic focusing principle is illustrated and the probe size is optimized; then, through comparative experiments and lift-off experiments in normal temperature environment, the performance improvement effect of the probe is illustrated; finally, through high-temperature experiments, the stability of the probe in a 500 °C environment is verified.

[0073] The basic structure of a common electromagnetic ultrasonic probe is as Figure 1 shown, consisting of a unidirectionally polarized permanent magnet and an excitation coil. When a high-frequency alternating current J 1 is passed through the excitation coil, eddy current J is induced on the surface of the metal specimene , a moving charged particle is subjected to an alternating Lorentz force F under the action of a bias magnetic field B 0 . The interaction between the charged particle and the surrounding structure forms ultrasonic waves. When the ultrasonic waves are transmitted downward and reflected by defects or the bottom surface, when the ultrasonic waves carrying the specimen information return to the specimen surface, the mechanical vibration of the particles cuts the magnetic induction line, and eddy currents are induced again on the specimen surface and received by the coil. Without changing the volume of the probe, in order to enhance the bias magnetic field density, the circumferential radiation magnetizing electromagnetic ultrasonic transducer for high-temperature non-destructive monitoring provided in this embodiment has a configuration as L shown in Figure 2 . An eight-piece sector permanent magnet with the polarization direction pointing to the center of the circle wraps a cylindrical soft iron core, and each magnet has the same magnetic pole facing the core, and the magnetic fields converge and superimpose in the magnetized soft iron core.

[0074] To verify and predict the enhancement effect of the bias magnetic field, a three-dimensional schematic model of CRM-EMAT as shown in Figure 3 is constructed, and numerical simulation analysis is carried out on it. The simulation model consists of a CRM magnetic group, an iron core, a butterfly coil, a specimen, and an air domain (hidden in the figure). The radius of the magnetic core is 5 mm and the height is 20 mm; the central angle of a single magnet is 45°, the height is 20 mm, and the thickness is 10 mm (i.e., the outer diameter minus the inner diameter), and a total of 8 pieces form a ring; the excitation-reception integrated coil is a butterfly coil with a diameter of 0.26 mm, the center spacing is 3 times the coil radius, the number of coil turns is 13, and the coil is 0.2 mm away from the lower surface of the magnetic core and the upper surface of the specimen (i.e., the lift-off distance); the length and width of the specimen are both 45 mm and the height is 5 mm; the air domain is set as a cube with a side length 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 strength, the magnetization model selects the B-H curve in the multi-physics simulation software library. Here, first, a steady-state study of the model is carried out. Only the magnetic field physical field needs to be added, the corresponding magnetization model configuration is completed for the permanent magnet and the iron core, and a coil geometric analysis step is added before the steady-state analysis to analyze the magnetic flux density distribution of CRM-EMAT as shown in Figure 4 . The radial magnetic flux is vertically concentrated in the magnetic core, and the maximum value reaches 3.18 T, which is located at the lower edge of the iron core.

[0075] Table Ⅰ

[0076]

[0077] Next, compare the optimization effect of the probe and explore the optimal size of CRM-EMAT. Limited by the skin effect, the induced eddy current only exists in the shallow surface of the specimen, and the skin depth can be calculated by formula (1), where f is the excitation frequency, is the magnetic permeability, is the electrical conductivity of the conductor material.

[0078]

[0079] For each additional skin depth, the electromagnetic wave attenuates to 1 / e of its original amplitude inside the conductor. Therefore, the bias magnetic field mainly acts at about 3 skin depths. Taking the center of the magnetic core as the center, a cross-section line is taken on the lower surface of the specimen to calculate the magnetic flux density distribution on the cross-section line and compare it with a cylindrical single magnet of the same volume. The results are as Figure 5 shown. For the CRM-EMAT structure, in the magnetic core region, the magnetic flux density increases significantly, with a maximum value of 1.65 T. Extending outward from directly below the center of the magnetic core, the best detection range can be obtained, while the maximum value of the traditional single magnet structure is only 0.7 T, and the magnetic flux density is increased by nearly 2.4 times.

[0080] Subsequently, a parametric scanning step is added to the study, and four parameters, namely the magnetic core radius, magnet thickness, magnetic core height, and magnet height, are scanned respectively. When one parameter changes, the other parameters remain unchanged. In this embodiment, first, the magnetic core radius is scanned with a step size of 4 mm from 4 mm to 52 mm; then the magnet thickness is scanned with a step size of 5 mm from 5 mm to 50 mm. Taking the midpoint of the cross-section line as the sampling point, its magnetic flux density is calculated. The results are as Figure 6 shown. As the magnet thickness increases, the magnetic flux density increases accordingly, but when the magnet thickness is greater than 20 mm, the increase rate begins to decrease; conversely, as the magnetic core radius increases, the magnetic flux density weakens, but considering the detection range, the magnetic core radius should not be too small. Then the magnetic core height is scanned, increasing from 4 mm to 24 mm in steps of 2 mm. The results are as Figure 7 shown. When the magnetic core height is 3 / 5 - 4 / 5 of the magnet height, the magnetic flux density reaches the maximum, rather than when it is flush with the magnet. Finally, the magnet height is scanned. Referring to Figure 8 , with a step size of 5 mm from 15 mm to 60 mm, the magnetic flux density increases with the increase of the magnet height. When the magnet height is greater than 30 mm, the increase trend of the magnetic flux density is weak. However, from the vertical axis of the results, the influence of the radius on the magnetic flux density is more significant.

[0081] Next, a transient study is added to the model to analyze the ultrasonic signal and its propagation in the specimen. To improve the calculation efficiency, a two-dimensional axisymmetric model is adopted, as Figure 9As shown, on the left is the equal - volume single - magnet EMAT structure, and on the right is the CRM - EMAT structure. With r = 0 as the axis, the magnetic field distribution is the same as that of the three - dimensional model described above. The purpose of equally dividing the CRM circular magnet into eight parts in actual production is to facilitate radial magnetization. The shape of the coil does not affect the signal amplitude, so the influence brought by the change of the coil shape is ignored here. In order to successfully analyze the ultrasonic waveform, when meshing, the maximum mesh in the specimen shall not exceed 1 / 10 of the shear - wave wavelength. In this embodiment, the Lorentz - force conversion mechanism is mainly considered, and the main ultrasonic type is shear - wave. A pulsed - modulated current with a frequency of 3 MHz and an amplitude of 20 A is applied to the coil. The function equation is as follows, where gp(t) is the Gaussian pulse function, f 0 is the frequency, T 0 is the period.

[0082]

[0083] Figure 10 shows the comparison of ultrasonic motion of two probe structures in the specimen at 10.4 ms. The stress on the specimen in the CRM - EMAT model is significantly greater than that of the EMAT with a single magnet structure. According to the ultrasonic motion and the velocity characteristics of various types of waves, surface waves, longitudinal waves, shear waves, and LS - mode conversion waves can be distinguished from Figure 10 , which helps in analyzing the echo signal. The ultrasonic echo signal is as Figure 11 shown. Compared with the single - magnet structure, the CRM - EMAT increases the amplitude by nearly 10 times and can receive waveforms of other modes.

[0084] In the experimental part, first, permalloy patch experiments, comparative experiments, and lift - off distance experiments were carried out at room temperature. As Figure 12 shown, the experimental platform consists of CRM - EMAT, specimen, monitoring main board, and display screen. The specimen is a 7.33 - mm - thick steel plate. Three sizes of CRM permanent magnets are processed, with thickness - height being 10 - 20 mm, 10 - 30 mm, and 15 - 30 mm respectively. The material is Sm 2 Co 17 (the remanence reversible operating temperature is 350 °C, and the Curie temperature is 850 °C). Silicon - steel cores with a magnetic - core radius of 5 mm and a height of 7 / 10 of the magnet height (i.e., 14 mm and 21 mm) are configured respectively. The material is silicon steel. The experimental data can be uploaded to the cloud through the 4G module of the MCU and obtained remotely directly on the web page, or can be directly exported through serial - port transmission.

[0085] Figure 13The following are the experimental results of permalloy patches. Permalloy has a high permeability in weak magnetic fields. When the permalloy patch is not attached, the magnetic field induced by the coil crosstalks into the silicon steel magnet and generates interference waves. After attaching the permalloy patch, the interference waves disappear, indicating that the permalloy patch prevents the magnetic field induced by the coil from entering the magnetic core and the magnet, thus playing a role in shielding the interference waves. In the comparative experiment, the echo signals generated by CRM-EAMT of three sizes were compared with those of a single cylindrical magnet EMAT with a diameter of 40 mm and a height of 30 mm. As Figure 14 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 increase the amplitude, and the effect of the magnet thickness is greater. Compared with the single-magnet EMAT, the amplitude of CRM-EMAT is increased by about 6 times. This is due to the larger lift-off distance in the actual experiment compared to the simulation and the influence of other environmental factors.

[0086] 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 respectively. From Figure 15 the signal amplitudes, it can be seen that when the lift-off distance increases by 0.5 mm each time, the signal amplitude decays by about half. When the lift-off distance is 1 mm, the signal amplitude is slightly larger than that of Figure 14 the single-magnet structure, so CRM-EMAT increases the lift-off distance by about 1 mm and allows a working lift-off distance of 2 mm.

[0087] Finally, a high-temperature experiment was conducted on CRM-EMAT. The experimental platform is as shown in Figure 16 The specimen was heated by a heating furnace. The coil used a ceramic substrate PCB, and the wire used mica-covered wire to adapt to the high-temperature monitoring environment. Signals were collected every 100 °C. The results are as shown in Figure 17 shown. 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, partial irreversible loss of the remanence of the samarium-cobalt magnet begins to occur. However, due to the circumferential magnet-core design of the CRM-EMAT probe, the remanence intensity still satisfies the good excitation and reception of the signal. Therefore, at 500 °C, the echo signal is still clear and stable.

[0088] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, 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 in the axial direction, and the magnetic flux of each sector-shaped permanent magnet is superimposed and converged in the magnetic core; 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.

2. The circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive 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.

3. The circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring according to claim 2, characterized in that: The butterfly coil is 0.2 mm away from the upper surface of the test piece.

4. The circumferential radiation magnetized electromagnetic ultrasonic transducer for high temperature nondestructive monitoring according to claim 2, 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.

5. The circular radiation magnetized electromagnetic ultrasonic transducer for high temperature nondestructive monitoring according to any one of claims 1 to 4, characterized in that: Permalloy patches are attached to the bottom of the cylindrical magnetic core and the eight sector-shaped permanent magnets.

6. A design method for a circular radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring, applied to the circular radiation magnetized electromagnetic ultrasonic transducer for high temperature non-destructive monitoring as claimed in any one of claims 1 to 5, 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.

7. The design method of the circular radiation magnetized electromagnetic ultrasonic transducer for high temperature nondestructive monitoring according to claim 6 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.

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 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.

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 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