High-temperature metal surface wave electromagnetic ultrasonic transducer and test system
By designing a high-temperature metal surface wave electromagnetic ultrasonic transducer, using a gas cooling system and a ceramic PCB process, the problem of poor performance of EMAT at high temperatures is solved, and higher transduction efficiency and signal conduction capabilities are achieved.
Patent Information
- Application Number
- CN202421428107.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-21
- Publication Date
- 2025-05-30
- Estimated Expiration
- 2034-06-21
AI Technical Summary
In the detection of high-temperature forgings, the existing EMAT has problems such as low transduction efficiency, low echo signal-to-noise ratio, and poor resolution. The existing cooling systems have problems such as excessive equipment size, many fault points, and inability to independently guarantee performance.
A high-temperature metal surface wave electromagnetic ultrasonic transducer is designed, using biased magnetic field module, gas cooling module and PCB coil module. It is placed in a suspended hanging bin through a permanent magnet, cooled by a gas cooling system, and a back-folded coil plate is made through a ceramic PCB process to achieve signal conduction.
It effectively isolates the impact of the shell on the permanent magnet temperature, reduces the loss of high-temperature magnetic performance of the permanent magnet, improves the performance and reliability of EMAT at high temperatures, reduces the equipment volume and failure risk, and ensures signal conduction at high temperatures.
Smart Images
Figure CN222926676U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of nondestructive testing, and relates to an electromagnetic ultrasonic transducer, in particular to a high-temperature metal surface wave electromagnetic ultrasonic transducer and a testing system. Background Technique
[0002] Electromagnetic ultrasonic transducers (EMATs) are particularly attractive in some nondestructive testing applications. EMATs do not require coupling or contact with the sample and can generate and detect multiple wave modes. Currently, many EMATs have problems such as strong heat radiation, large lift-off, and large ultrasonic attenuation coefficients in the detection of high-temperature castings and forgings, resulting in low transducer efficiency, low echo signal-to-noise ratio, and poor resolution at high temperatures, which limits the application of EMATs in the detection of high-temperature castings and forgings.
[0003] At present, some researchers have designed different cooling systems to improve the high-temperature resistance of EMATs. There are two current cooling methods: water cooling and air cooling. The water cooling system requires components such as water pumps, coolers, and pipeline valves, which will make the EMAT equipment too large and heavy, increasing the failure points of the system. However, the existing air cooling systems cannot independently guarantee the performance of EMATs under high-temperature conditions due to unreasonable cavity designs.
[0004] At present, the coils of high-temperature EMATs can be wound by hand or processed by printed circuit boards (PCBs). The method of hand winding is difficult to accurately control the line spacing, and the wire spacing has a great impact on the superposition effect of ultrasonic signals. Therefore, the PCB process is basically used to process EMAT coils at present. However, the coils made of ordinary PCB substrates are difficult to survive at high temperatures. Summary of the Utility Model
[0005] The purpose of the utility model is to overcome the above-mentioned defects existing in the prior art and provide a high-temperature metal surface wave electromagnetic ultrasonic transducer and a testing system that are suitable for high-temperature environments and have high reliability.
[0006] The purpose of the utility model can be realized by the following technical solutions:
[0007] A high-temperature metal surface wave electromagnetic ultrasonic transducer includes a bias magnetic field module, a gas cooling module, and a PCB coil module. The bias magnetic field module includes a hanging bin and a permanent magnet disposed in the hanging bin. The gas cooling module includes a metal cavity, a front plate, and an inflation interface. The metal cavity and the front plate are combined into a closed structure. The hanging bin is suspended and installed in the metal cavity. The inflation interface is connected to the metal cavity. The PCB coil module includes a ceramic cover plate and a ceramic PCB folded coil plate stacked. The PCB coil module is installed at the bottom of the metal cavity through fixing bolts. One end of the fixing bolt is connected to the top of the metal cavity, and the other end is in contact connection with the ceramic cover plate to clamp the ceramic cover plate and the ceramic PCB folded coil plate.
[0008] Further, the end of the hanging bin includes a bin body part and feet disposed at the four corners of the bin body part. The bin body part is used to place the permanent magnet, and the top ends of the feet are fixed to the metal cavity through pins.
[0009] Further, a plurality of through holes for passing through the pins are provided at the top ends of the feet.
[0010] Further, a BNC connector for passing through the lead-out signal line of the ceramic PCB folded coil plate is provided on the front plate.
[0011] Further, the metal cavity, the front plate, and the hanging bin are all made by 3D printing of 316L stainless steel material.
[0012] Further, the permanent magnet is made of samarium cobalt material.
[0013] Further, a plurality of exhaust holes are provided at the bottoms of the metal cavity and the front plate.
[0014] Further, the exhaust holes are through holes inclined upward at 45°.
[0015] Further, the ceramic PCB folded coil plate includes an alumina substrate with a glass glaze solder mask layer and silver wires.
[0016] The present utility model also provides a test system, including the high-temperature metal surface wave electromagnetic ultrasonic transducer as described above.
[0017] Compared with the prior art, the present utility model has the following beneficial effects:
[0018] (1) The present utility model sets a high-temperature EMAT air-cooled cavity. The permanent magnet is placed in the suspended hanging bin. The heat in the high-temperature specimen is difficult to transfer from the hanging bin to the permanent magnet, effectively isolating the influence of the housing on the temperature of the permanent magnet, thereby reducing the high-temperature magnetic performance loss of the permanent magnet, and irreversible magnetic performance loss will not occur within the required temperature range for measurement.
[0019] (2) The present utility model is provided with an inflation interface and a metal cavity, and uses an air-cooling method to cool the high-temperature magnet. Compared with the water-cooling method, the air-cooling system has a more lightweight volume, and can more conveniently cool the EMAT. In addition, the risk of equipment leakage caused by liquid leakage due to pipeline rupture is reduced. The air-cooling method of the structure of the present utility model can reduce the temperature at the top of the EMAT and ensure the normal operation of the BNC installed near this position. The exhaust holes are all designed as through holes inclined upward at 45°, so as to reduce the influence of the externally sprayed air flow on the temperature of the aluminum plates around the EMAT.
[0020] (3) The present utility model realizes the production and signal conduction of the high-temperature EMAT coil by using the ceramic PCB process to produce the folded-back coil board and clamping the wire with a ceramic cover plate. Compared with winding the coil, the design of the PCB folded-back coil can more accurately and conveniently excite surface waves at a lower cost.
[0021] (4) Compared with ordinary PCB substrates, the present utility model uses alumina with the lowest thermal conductivity as the substrate, uses glass glaze as the solder mask layer, and silver as the wire material, so that the present utility model can still operate normally under high-temperature working conditions and still play the advantages of the PCB folded-back coil. Compared with the connection method of wire soldering, the present utility model uses the method of clamping the wire with a ceramic cover plate to realize the hard connection between the BNC wire and the ceramic PCB, effectively avoiding the situation of internal wire de-soldering under high-temperature conditions. Description of the Drawings
[0022] Figure 1 is a schematic structural diagram of the ultrasonic transducer of the present utility model;
[0023] Figure 2 is a schematic internal structure diagram of the ultrasonic transducer of the present utility model;
[0024] Figure 3 is a schematic top view of the ultrasonic transducer of the present utility model;
[0025] Figure 4 is Figure 3 a C-C cross-sectional view of;
[0026] Figure 5 is a schematic front plate diagram of the ultrasonic transducer of the present utility model;
[0027] Figure 6 is a schematic installation diagram of the ceramic cover plate and the ceramic PCB folded-back coil board of the present utility model;
[0028] Figure 7 is a schematic internal air-cooling circuit diagram of the ultrasonic transducer of the present utility model;
[0029] Figure 8Schematic diagram for comparison of surface wave signals excited by the original design and the corrected excitation frequency in the time domain in the embodiment;
[0030] Figure 9 Schematic diagram for comparison of surface wave signals excited by the original design and the corrected excitation frequency in the frequency domain in the embodiment;
[0031] Figure 10 Waveforms at different temperatures after adjusting the excitation frequency in the embodiment;
[0032] In the figure: 1. Inflation interface, 2. Metal cavity, 3. Pin, 4. First bolt, 5. BNC connector, 6. Hanging bin, 7. Ceramic cover plate, 8. Permanent magnet, 9. Nut, 10. Ceramic PCB folded coil board, 11. Front plate, 12. Second bolt, 601. Bin body part, 602. Foot part, 701. Through hole, 801. PCB substrate, 802. Pad, 803. Wire. Detailed implementation manners
[0033] The present utility model will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present utility model, and gives detailed implementation manners and specific operation processes, but the protection scope of the present utility model is not limited to the following embodiments.
[0034] This embodiment provides a high-temperature metal surface wave electromagnetic ultrasonic transducer. Referring to Figures 1-5 as shown, the EMAT includes a bias magnetic field module, a gas cooling module and a PCB coil module. The bias magnetic field module includes a hanging bin 6 and a permanent magnet 8 arranged in the hanging bin 6. The gas cooling module includes a metal cavity 2, a front plate 11 and an inflation interface 1. The metal cavity 2 and the front plate 11 are combined into a closed structure and fixed by a second bolt 12. The hanging bin 6 is suspended and installed in the metal cavity 2. The inflation interface 1 is connected to the metal cavity 2. The PCB coil module includes a ceramic cover plate 7 and a ceramic PCB folded coil board 10 which are stacked. The PCB coil module is installed at the bottom of the metal cavity 2 through a fixing bolt. One end of the fixing bolt is connected to the top of the metal cavity 2, and the other end is in contact connection with the ceramic cover plate 7. The fixing bolt is the first bolt 4. The above EMAT can obtain an ultrasonic transducer that can ensure the high-temperature survival ability of the permanent magnet and effectively reduce waveform distortion, improve the reliability of subsequent applications such as sample damage detection, and can be applied to high-temperature environments.
[0035] In the above device, the hanging bin 6 is suspended above the PCB coil module. By adjusting the position of the hanging bin, the height of the magnet structure relative to the coil can be adjusted, and the reserved space is used as an air layer to reduce the heat received by the permanent magnet from the coil.
[0036] As Figure 2As shown, the end of the hanging bin 6 includes a bin body part 601 and feet 602 provided at the four corners of the bin body part 601. The bin body part 601 is used to place the permanent magnet 8, and the top ends of the feet 602 are fixed to the metal cavity 2 through pins 3. In a preferred embodiment, a plurality of through holes for passing the pins are provided at the top ends of the feet 602 to facilitate adjusting the hanging position of the hanging bin and at the same time keep the distance between the magnet and the coil relatively unchanged.
[0037] The above-mentioned permanent magnet 8 is made of samarium cobalt (SmCo) material. Samarium cobalt material exhibits better performance and viability at high temperatures, will not have irreversible magnetic property loss at high temperatures, and can maintain long-term magnetic property stability.
[0038] The above-mentioned ceramic PCB folded coil board 10 uses alumina as the PCB substrate, covers glass glaze as the solder mask layer, and uses silver wires as the signal layer, which can effectively circulate current signals at high temperatures, and realizes the hard connection between the wires and the ceramic PCB substrate by clamping the wires with a ceramic cover plate. Refer Figure 6 As shown, the ceramic cover plate 7 and the ceramic PCB folded coil board 10 are inserted into the bottom groove reserved in the metal cavity 2 of the high-temperature EMAT in an overlapping manner from top to bottom. Four first bolts 4 extend from the top of the EMAT metal shell, and by adjusting the screwing length of the bolts, different pressures are applied to the ceramic cover plate on the top to achieve complete clamping of the ceramic cover plate and the ceramic PCB folded coil board. In this embodiment, there are four through holes 701 on the surface of the ceramic cover plate, two in a group, and two wires are respectively wound in a group of through holes. The wire 803 extends into the ceramic cover plate from one through hole 701, enters the gap between the ceramic cover plate and the PCB substrate 801, and after passing through the square silver solder pad 802 exposed on the surface of the PCB substrate 801, extends out from another through hole. A BNC connector 5 is provided on the front plate 11, and the signal wire led out by the coil transmits signals to and from the transceiver device through the BNC connector. Preferably, the wire between the BNC connector and the ceramic PCB is a high-temperature resistant wire, and the insulating layer on its surface is woven with glass fiber filaments to adapt to the high-temperature environment.
[0039] The space between the metal cavity 2, the front plate 11 and the hanging bin 6 forms a gas cooling channel. Among them, the metal cavity 2 and the front plate 11 form an outer shell, which plays a role of fixing and guiding air. The hanging bin 6 is a metal hanging bin, which is used to fix the permanent magnet structure. An inflation interface 1 fixed by a nut 9 is provided at the top of the metal cavity 2, and the inflation interface 1 is connected to the air-cooling quick connector of the air pump for inputting gas. An exhaust hole is provided at the bottom of the metal cavity 2. When in the working state, the cooling air flow enters the EMAT from the inflation interface 1, then takes away their heat when passing through the permanent magnet downward, and finally discharges the hot air from the exhaust hole at the bottom of the outer shell. Specifically, as Figure 7As shown, the air-cooling circuit introduces cold air from the air pump to the periphery of the permanent magnet. The top first comes into contact with the cold air, which can effectively reduce the temperature of the top of the magnet. Blocked by the magnet, part of the air will move upward, taking away the heat from the top of the EMAT, thereby reducing the temperature inside the cavity and ensuring that the nearby BNC connectors can work properly. Another part of the air will continue to move downward along the side of the magnet and finally discharge from the exhaust holes at the bottom of the housing. At the same time, under the action of air pressure, the hot air at the bottom of the permanent magnet will also be discharged.
[0040] In this embodiment, the metal cavity 2, the front plate 11 and the hanging bin 6 are all made by 3D printing of 316L stainless steel material, so as to ensure the overall strength and high-temperature applicability of the structure. At the same time, 316L belongs to austenitic stainless steel and does not have ferromagnetic properties itself, and will not interfere with the magnetic field distribution. The air-cooling quick connectors use PU hoses or nylon tubes with a pressure resistance of 1.32 MPa.
[0041] In the preferred embodiment, a plurality of exhaust holes are provided on both the metal cavity 2 and the front plate 11, and each exhaust hole is designed as a through hole inclined upward at 45°, which is used to maintain the pressure balance inside the cavity when the air pump is ventilated.
[0042] This embodiment provides a narrow magnet EMAT structure to excite ultrasonic waves. Different from the conventional wide magnet, the magnet width of the narrow magnet EMAT less than is the width of the folded coil. The narrow magnet EMAT can significantly amplify the signal, but the problem of waveform distortion of the excited signal is serious. In the high-temperature EMAT structure, when the surface temperature of the specimen to be tested rises from room temperature of 25 °C to 350 °C, the wave velocity of the surface wave will decrease by about 10%. When the excitation frequency remains unchanged, it will cause the wavelength of the surface wave to also decrease by 10%. The change in wavelength will significantly affect the phase of the surface wave, thereby amplifying the phase difference between the excited signals of different wires, which is not conducive to the superposition and enhancement of the surface wave. Therefore, in the preferred embodiment, when the EMAT is used, the optimal excitation frequency can be calculated first to effectively eliminate waveform distortion. Specifically, according to the folding distance of the folded coils on the ceramic PCB folded coil board, the optimal excitation frequency of the ultrasonic transducer is calculated to achieve waveform distortion correction.
[0043] In a specific embodiment, the calculation of the optimal excitation frequency specifically includes:
[0044] After determining the hanging position of the hanging bin and the screwing length of the fixing bolts, assemble the components of the ultrasonic transducer, and use a 10-cycle tone-burst signal as the excitation signal with a frequency of 500 kHz, and calculate the folding distance L = λ / 2 = 2.94 mm;
[0045] Determine the magnetic field phase offset according to the magnetic field distribution The value is used to obtain the phase offset of the surface wave signal excited by the nth wire.
[0046]
[0047] Among them, is the phase offset of the nth wire, λ is the wavelength, L is the folding distance, is the phase offset component is the relationship function between the position x where the wire is located, and f is the frequency;
[0048] Select the two wires at the edge and in the center as typical feature pairs representing the phase difference of the entire coil. Taking the 1st wire and the 6th wire as examples:
[0049]
[0050] Calculate the frequency f value that makes the phase deviation between the edge wire and the central wire zero:
[0051]
[0052] After calculation, the optimal excitation frequency f = 438 kHz can be obtained.
[0053] As Figure 8 and Figure 9 can be seen from the signal spectrograms, after correcting the excitation frequency to 438 kHz, the frequency sidelobes of the signal are effectively eliminated, and there is basically no phenomenon of central frequency offset. The result shows that the central frequency of the received signal is 440.382 kHz, and the error is about 0.54%. As Figure 10 shows, the surface wave can be well transmitted and received at different temperatures.
[0054] The above method for eliminating waveform distortion is also applicable to wide magnets.
[0055] The high-temperature metal surface wave electromagnetic acoustic transducer (EMAT) obtained in this embodiment has the advantages of ensuring the high-temperature survival ability of the permanent magnet and realizing reliable conduction of the high-temperature EMAT coil signal, and is applicable to an environment up to 350 °C. In the high-temperature gas-cooled cavity EMAT, the metal cavity, the front plate, and the BNC probe enclose the EMAT metal shell, the hanging bin and the magnet form the bias magnetic field, and the ceramic cover plate and the PCB board form the coil. Before using the EMAT, first use an air pump to pump air into the air pipe interface to inflate the metal shell. The gas fills the EMAT metal shell to cool the bias magnetic field and the coil, and finally flows out from the uniformly distributed exhaust holes at the bottom of the metal cavity. The inflation speed can be achieved by adjusting the air pump pressure. When exciting ultrasonic waves, the EMAT is placed on the surface of the plate as a probe, and the pulsed current is conducted through the BNC connector and the coil. When an alternating current passes through the coil, an alternating eddy current is induced in the plate. Under the action of the bias magnetic field, the eddy current is subjected to the Lorentz force. Under the action of the Lorentz force, the particles inside the metal plate vibrate, and this vibration will propagate in the form of ultrasonic waves.
[0056] In the experimental verification process of the present utility model, an air pump with an exhaust volume of 390 L / min is used to cool the inside of the high-temperature EMAT. When the average temperature on the surface of the aluminum plate reaches 346.6 °C, the temperature inside the high-temperature EMAT can still be maintained below 75 °C: the temperatures of the excitation-end EMAT and the receiving-end EMAT are 73.6 °C and 70.0 °C respectively, and the temperature rise is less than 50 °C compared with the normal temperature condition of 25 °C. At this time, the temperature difference between the inside and outside of the EMAT is more than 270 °C. As shown in Table 1.
[0057] Table 1 Actual temperatures on the surface of the aluminum plate and inside the high-temperature EMAT under different temperature settings
[0058]
[0059] In another embodiment, a test system is further provided, which can realize the transmission and reception of surface waves under high-temperature conditions, including: a signal generator, an oscilloscope, an impedance matching network, a preamplifier, a heating table, and the above-mentioned high-temperature metal surface wave electromagnetic acoustic transducer. Among them, the two ultrasonic transducers are respectively used as the excitation-end EMAT and the receiving-end EMAT, are respectively connected to the air pump through the inflation interface, and are placed on the sample of the heating table. The BNC connector of the excitation-end EMAT is connected to the signal generator through the impedance matching network, and the BNC connector of the receiving-end EMAT is connected to the oscilloscope through the impedance matching network, the preamplifier, and the oscilloscope. The heating table is also connected to a temperature controller, and the temperature is measured by a thermocouple thermometer.
[0060] The preferred specific embodiments of the present utility model have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present utility model without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in this technical field based on the concept of the present utility model through logical analysis, reasoning, or limited experiments on the basis of the prior art should fall within the protection scope determined by the claims.
Claims
1. A high temperature metal surface wave electromagnetic ultrasonic transducer, characterized in that: It includes a bias magnetic field module, a gas cooling module and a PCB coil module. The bias magnetic field module includes a hanging bin and a permanent magnet arranged in the hanging bin. The gas cooling module includes a metal cavity, a front plate and an inflation interface. The metal cavity and the front plate are combined into a closed structure. The hanging bin is suspended in the metal cavity. The inflation interface is connected to the metal cavity. The PCB coil module includes a stacked ceramic cover plate and a ceramic PCB folded coil plate. The PCB coil module is installed on the bottom of the metal cavity through a fixing bolt. One end of the fixing bolt is connected to the top of the metal cavity, and the other end contacts and connects the ceramic cover plate to clamp the ceramic cover plate and the ceramic PCB folded coil plate.
2. The high temperature metal surface wave electromagnetic ultrasonic transducer according to claim 1, characterized in that: The hanging bin end comprises a bin body and feet arranged at the four corners of the bin body, the bin body is used to place the permanent magnet, and the top of the foot is fixed to the metal cavity through a pin.
3. The high temperature metal surface wave electromagnetic ultrasonic transducer according to claim 2, characterized in that: The top of the foot is provided with a plurality of through holes for passing pins.
4. The high temperature metal surface wave electromagnetic ultrasonic transducer according to claim 1, characterized in that: The front panel is provided with a BNC connector for leading out a signal line passing through the ceramic PCB folded coil board.
5. The high temperature metal surface wave electromagnetic ultrasonic transducer according to claim 1, characterized in that: The metal cavity, front plate and hanging bin are all made of 316L stainless steel material by 3D printing.
6. The high temperature metal surface wave electromagnetic ultrasonic transducer according to claim 1, characterized in that: The permanent magnet is made of samarium cobalt material.
7. The high temperature metal surface wave electromagnetic ultrasonic transducer according to claim 1, characterized in that: The metal cavity and the bottom of the front plate are provided with a plurality of exhaust holes.
8. The high temperature metal surface wave electromagnetic ultrasonic transducer according to claim 7, characterized in that: The exhaust hole is a through hole inclined upward at 45 degrees.
9. The high temperature metal surface wave electromagnetic ultrasonic transducer according to claim 1, characterized in that: The ceramic PCB folded coil board includes an aluminum oxide substrate with a glass glaze solder resist layer and a silver wire.
10. A testing system, characterized in that: It comprises a high-temperature metal surface wave electromagnetic ultrasonic transducer as described in any one of claims 1-9.