A stretchable electromagnetic ultrasonic guided wave sensor and a method of making the same

Abstract

The application belongs to the technical field of pipeline sensors, and discloses a stretchable electromagnetic ultrasonic guided wave sensor and a preparation method thereof, wherein the sensor comprises a flexible substrate, the flexible substrate has a cavity inside, the cavity is filled with a liquid metal coil formed by liquid metal, both ends of the liquid metal coil are connected with metal electrodes, and the two metal electrodes are fixed at two ends of the flexible substrate respectively. The sensor can be used for ultrasonic guided wave detection of thin pipelines with different diameters, and realizes positioning of defects. The sensor coil of the application is filled with liquid metal in the flexible substrate, and can stretch or contract along with the flexible stretching substrate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pipeline sensors, and particularly relates to a stretchable electromagnetic ultrasonic guided wave sensor and a preparation method thereof. BACKGROUND

[0002] Pipelines are one of the economic means for transporting oil, natural gas and other media, and play an important role in the national economy and production. However, pipelines may also fail due to corrosion and other reasons. A large number of small and medium diameter oil and gas pipelines in some areas are distributed in densely populated areas, and once corrosion leakage accidents occur, the consequences will be more serious. Therefore, the detection of oil and gas pipelines is particularly important.

[0003] In the petrochemical industry, small diameter pipelines are used in various aspects of petrochemical pipeline systems, including applications such as:

[0004] 1. Pipeline transportation: Small diameter pipelines can connect different equipment and process units to achieve fluid transportation and distribution.

[0005] 2. Measurement and instrumentation: By installing flow meters, pressure sensors, temperature sensors and other measuring instruments on small diameter pipelines, process parameters can be monitored and controlled in real time to ensure the safety and quality of the production process.

[0006] 3. Process control: Small diameter pipelines are used in the process control system of a petrochemical plant by connecting to control valves, regulating valves and other control elements.

[0007] 4. Equipment connection and installation: Small diameter pipelines serve as connecting elements to connect various equipment and machinery in a petrochemical plant, such as pumps, compressors, heat exchangers, etc.

[0008] Although the thin-wall pipe is generally made of high-strength material resistant to corrosion and high temperature, due to the harsh working environment (in humid, corrosive gas or water and vibration load), the pipe system in long-term operation will inevitably produce some defects such as oxidation, corrosion, metal fatigue and cracks. The commonly used non-destructive testing methods for pipes include magnetic flux leakage detection method, eddy current detection method, ultrasonic detection method and ultrasonic guided wave detection method. Among them, the eddy current detection can be used for various metal pipes and can detect cracks and corrosion defects, but the eddy current detection has weak penetration ability for ferromagnetic metal and can only detect surface or near-surface defects, and when the surface corrosion product contains a magnetic scale layer, the signal-to-noise ratio of the detection signal will be greatly reduced, resulting in detection error. The ultrasonic detection is generally used to detect whether there is a crack in the thickness direction of the pipe, and the ultrasonic wave can be focused through phased array to achieve the purpose of point detection, but the disadvantage is that it cannot be used for large-area rapid detection. The ultrasonic phased array needs to use a special timing circuit design, and the obtained data is large, and the data processing takes a long time, so the detection efficiency is relatively low. As a commonly used detection method in China at present, the magnetic flux leakage detection has more intuitive results than other detection methods, but it can only detect the surface defects of the pipe and is highly subjective. The ultrasonic guided wave detection detects defects through guided wave transmission and reflection characteristics, has the characteristics of high efficiency and rapidness, and is suitable for pipe detection.

[0009] The ultrasonic guided wave used for thin-wall pipe detection is different from the conventional pipe detection, and has the following difficulties:

[0010] 1. Difficulty in coupling. Due to the small curvature radius of the thin-wall pipe, the contact area between the probe and the pipe is small, and the poor coupling leads to low excitation and reception efficiency of the transducer.

[0011] 2. Difficulty in defect positioning and quantification. For thin-wall pipes, the short length and thin thickness of the pipe make the guided wave sound path short, thereby affecting the positioning and quantification of defects in the near-field area.

[0012] 3. Interference of false signals. The excess height of the thin-wall weld is smaller than the thickness of the base material, and the excess height of the inner and outer surfaces of the weld will produce more signal interference during inspection, which makes it difficult to identify the existence of real defects.

[0013] 4. Influence of joint form. The thin-wall pipe is mostly a branch pipe, and the complex guided wave propagation makes the received signal complex, which affects the defect judgment.

[0014] Therefore, it is necessary to design a thin-wall sensor compatible with different pipe diameters to realize ultrasonic guided wave detection of thin-wall pipes. SUMMARY

[0015] In view of the above problems, the present application provides a stretchable electromagnetic ultrasonic guided wave sensor and a preparation method thereof, which adopts the following technical scheme:

[0016] A stretchable electromagnetic ultrasonic guided wave sensor, comprising a flexible substrate, wherein the flexible substrate has a cavity inside, the cavity is filled with a liquid metal coil formed by a liquid metal, both ends of the liquid metal coil are connected with metal electrodes, and the two metal electrodes are fixed on both ends of the flexible substrate respectively.

[0017] Further, the metal electrode is made of copper, aluminum or silver.

[0018] Further, the liquid metal coil is a zigzag coil.

[0019] Further, the flexible substrate is in a strip shape, and the metal electrode is in a square plate shape.

[0020] The application also provides a use method of the stretchable electromagnetic ultrasonic guided wave sensor, comprising the following steps:

[0021] The stretchable electromagnetic ultrasonic guided wave sensor is circumferentially arranged on the outer wall of the pipeline, and a magnet is installed on the outer wall of the pipeline to provide a bias static magnetic field for the liquid metal coil.

[0022] The stretchable electromagnetic ultrasonic guided wave sensor is used as an excitation end to input an alternating excitation signal, and is used as a receiving end to receive a reflected wave.

[0023] The propagation speed of the guided wave is determined according to the pipeline dispersion curve, and the distance between the pipeline defect and the stretchable electromagnetic ultrasonic guided wave sensor is determined according to the time when the alternating excitation signal is input, the time when the reflected wave is received, and the propagation speed of the guided wave.

[0024] Further, the stretchable electromagnetic ultrasonic guided wave sensor is used as an excitation end to input an alternating excitation signal, and is used as a receiving end to receive a reflected wave, comprising:

[0025] When the stretchable electromagnetic ultrasonic guided wave sensor is used as an excitation end, the alternating excitation signal is introduced into the metal electrode through a wire and conducted to the liquid metal coil, an induced eddy current is generated on the inner wall of the pipeline, under the action of the bias static magnetic field formed by the magnet on the outer wall of the pipeline, a force perpendicular to the radial direction of the pipeline is generated, an ultrasonic guided wave is generated by vibration, the guided wave propagates along the axial direction of the pipeline, when the ultrasonic guided wave encounters a defect, a reflected wave is generated from the defect and propagates back to the stretchable electromagnetic ultrasonic guided wave sensor as a receiving end along the incident wave propagation path.

[0026] Further, the distance between the pipeline defect and the stretchable electromagnetic ultrasonic guided wave sensor is determined according to the time when the alternating excitation signal is input, the time when the reflected wave is received, and the propagation speed of the guided wave, comprising:

[0027] L=(t2-t1) / (2*v)

[0028] Where v represents the propagation speed of the guided wave, t1 represents the excitation time, and t2 represents the time when the reflected wave is received.

[0029] The present invention also provides a method for fabricating the stretchable electromagnetic ultrasonic guided wave sensor, comprising the following steps:

[0030] To create a solid coil with the same shape as a liquid metal coil;

[0031] The solid coil is placed into a mold, liquid flexible stretchable material is poured in, and a fluid inlet and a fluid outlet are reserved. After the liquid flexible stretchable material solidifies, a flexible substrate is obtained.

[0032] The corrosive agent is poured into the fluid inlet of the flexible substrate to corrode the solid coil, and then poured out from the corrosive fluid outlet. The coil is then rinsed with clean water until no corrosive liquid remains, forming a cavity in the flexible substrate that matches the shape of the liquid metal coil.

[0033] Liquid metal is injected into the fluid inlet of a flexible substrate, and the fluid inlet and outlet are sealed with a conductive solid material. Metal electrodes are attached to the fluid inlet and outlet. After the liquid metal solidifies, a liquid metal coil is formed, thus obtaining a stretchable electromagnetic ultrasonic guided wave sensor.

[0034] Furthermore, it also includes the following steps:

[0035] The dimensions of the flexible substrate are determined based on the volume of the liquid metal coil, and the dimensions of the mold are determined based on the dimensions of the flexible substrate.

[0036] Furthermore, the solid coil is made of iron or aluminum wire, and the etching agent is nitric acid solution.

[0037] The beneficial effects of this invention are: the sensor of this invention can be used for ultrasonic guided wave detection of thin pipes of different diameters to locate defects. The sensor coil of this invention uses liquid metal filled in a flexible substrate, allowing it to stretch or contract with the flexible substrate.

[0038] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A schematic diagram of a stretchable electromagnetic ultrasonic guided wave sensor according to an embodiment of the present invention is shown.

[0041] Figure 2 A schematic diagram of the installation of a stretchable electromagnetic ultrasonic guided wave sensor and a pipe according to an embodiment of the present invention is shown.

[0042] Figure 3 A schematic diagram illustrating the principle of using a stretchable electromagnetic ultrasonic guided wave sensor for pipeline defect localization according to an embodiment of the present invention is shown.

[0043] In the diagram: 1. Flexible substrate; 2. Liquid metal coil; 3. Metal electrode; 4. Magnet; 5. Pipe. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] It should be noted that the terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein.

[0046] Small-diameter pipelines are widely used in the petrochemical industry. Although the pipe body is generally made of high-strength materials that are resistant to high temperatures and corrosion, long-term operation in harsh environments inevitably leads to defects such as oxidation, corrosion, metal fatigue, and cracks. The presence of these defects can ultimately cause leaks and explosions, resulting in huge losses of life and property. Ultrasonic guided wave testing is fast and efficient, making it suitable for the inspection of petrochemical pipelines.

[0047] Ultrasonic guided wave detection methods can be divided into electromagnetic ultrasonic guided waves and piezoelectric ultrasonic guided waves. Piezoelectric ultrasonic guided waves utilize a polarized piezoelectric material attached to the surface of the material being tested. An excitation signal is passed through the high-impedance polarized piezoelectric material, causing it to vibrate in the polarization direction, thus converting the electrical signal into a mechanical vibration signal. This vibration signal is then transmitted to the material being tested, generating ultrasonic guided waves. Currently, piezoelectric sensors are relatively mature, with companies producing them in various sizes and from rigid to flexible designs, offering excellent frequency bandwidth and amplitude response. However, piezoelectric sensors also have significant and unavoidable drawbacks. First, the surface of the material being tested needs to be cleaned to reduce the impact of surface contaminants on the detection signal. Second, piezoelectric sensors must be used in conjunction with a coupling agent; the type of coupling agent and the application method can affect the detection results, and coupling agents are difficult to apply in certain environments, such as high temperatures. Electromagnetic ultrasonic guided wave sensors can be further divided into sensors based on the magnetostriction principle and sensors based on the Lorentz force. The magnetostriction-based sensor consists of a material with high magnetostriction (nickel strip) and a coil. Utilizing the magnetostrictive effect of the material, the pre-magnetized material is attached to the surface of the material being inspected. An excitation signal is then passed through the coil to generate an induced magnetic field. The nickel strip vibrates due to magnetostriction under the influence of the magnetic field, and the vibration is transmitted to the inspected material. Its disadvantages are similar to those of piezoelectric sensors. The Lorentz force-based electromagnetic ultrasonic sensor is a non-contact sensor, requiring no contact with the surface of the inspected material or surface cleaning, making it ideal for non-destructive testing of pipelines in the petrochemical industry.

[0048] Currently, there are very few electromagnetic ultrasonic guided wave sensors specifically designed for the inspection of small-diameter pipes. Small-diameter pipes come in a wide variety of diameters and types, and traditionally, a single sensor design can only be used for the inspection of one type of pipe diameter.

[0049] Based on the above theory, this invention provides a stretchable electromagnetic ultrasonic guided wave sensor and its preparation method, which can be used for ultrasonic guided wave detection in thin pipes of different diameters, and generates ultrasonic guided waves in the pipe by utilizing the static magnetic field and the eddy current effect of the coil.

[0050] like Figure 1 As shown, a stretchable electromagnetic ultrasonic guided wave sensor includes a flexible substrate 1, for example, the flexible substrate 1 is made of flexible and stretchable materials such as silicone or PDMS (polydimethylsiloxane).

[0051] Polydimethylsiloxane is a high molecular weight polymer that is odorless, highly transparent, and possesses excellent heat and cold resistance, minimal viscosity change with temperature, water resistance, low surface tension, and thermal conductivity (0.134-0.159 W / (m·K)). It exhibits 100% light transmittance. Dimethylsiloxane is non-toxic, odorless, physiologically inert, and chemically stable. It also demonstrates good electrical insulation, weather resistance, and hydrophobicity, along with high shear strength and tensile strength, allowing for long-term use at temperatures ranging from -50℃ to 200℃. It possesses excellent physical properties.

[0052] The flexible substrate 1 has a cavity inside, which is filled with a liquid metal coil 2. Both ends of the liquid metal coil 2 are connected to metal electrodes 3. The two metal electrodes 3 are fixed at both ends of the flexible substrate 1. The two ends of the liquid metal coil 2 are led out from the metal electrodes 3 and can be connected to wires to conduct excitation signals or receive signals.

[0053] For example, the metal electrode 3 and the liquid metal coil 2 can be made of materials such as copper, aluminum, or silver. The liquid metal coil 2 is one or more of the following: a zigzag coil, a spiral coil, a racetrack coil, a spiral coil, a zigzag coil, and a racetrack coil. For example, the liquid metal coil 2 may be a single zigzag coil. However, the liquid metal coil 2 is not limited to a single coil; it can also be a spiral coil, a racetrack coil, multiple spiral coils, or a combination of a zigzag coil and a racetrack coil.

[0054] For example, the flexible substrate 1 is strip-shaped, the metal electrode 3 is square plate-shaped, and the cavity is zigzag-shaped. A zigzag coil is formed by filling the cavity with liquid metal. The reason why the liquid metal coil 2 of this invention does not directly use copper wire is that although copper wire is relatively flexible and can be bent to adapt to the curved surface of the pipe 5, its tensile strength is poor, and it cannot stretch or contract with the flexible substrate 1 according to changes in pipe diameter. Therefore, the liquid metal coil 2 of this invention is designed with liquid metal filled in the flexible substrate 1, allowing it to stretch or contract with the flexible substrate.

[0055] The present invention also provides a method for using the above-mentioned stretchable electromagnetic ultrasonic guided wave sensor, comprising the following steps:

[0056] S11. A stretchable electromagnetic ultrasonic guided wave sensor is wrapped around the outer wall of the pipe 5 in the circumference of the pipe 5, and a magnet 4 is installed on the outer wall of the pipe 5 to provide a bias static magnetic field for the liquid metal coil 2.

[0057] For example, magnet 4 is a high coercivity hard magnet. When the outer diameter of pipe 5 is less than 10cm, a stretchable electromagnetic ultrasonic waveguide sensor is wrapped around the outer wall of pipe 5, and a bias static magnetic field is provided to liquid metal coil 2 through magnet 4.

[0058] When the outer diameter of the pipe 5 is greater than 10cm, the metal electrodes 3 of multiple stretchable electromagnetic ultrasonic guided wave sensors are connected end to end and wrapped around the outer wall of the pipe 5, and multiple magnets 4 provide a bias static magnetic field for the liquid metal coil 2.

[0059] For example, such as Figure 2 As shown, two metal electrodes 3 of a stretchable electromagnetic ultrasonic guided wave sensor are arranged end to end around the outer wall of the pipe 5 according to the outer diameter of the pipe 5. At the upper and lower ends of the outer wall of the pipe 5, there are a first magnet 4 and a second magnet 4 respectively. The N pole of the first magnet 4 and the S pole of the second magnet 4 are arranged opposite to each other.

[0060] In this invention, the stretchable electromagnetic ultrasonic guided wave sensor uses a flexible substrate 1, which can be stretched and attached to the outer wall of the pipe 5. Since the liquid metal coil 2 is a zigzag coil, it can be stretched along with the flexible substrate 1. Metal electrodes 3 are provided at both ends of the flexible substrate 1, so that when the outer diameter of the pipe 5 is large, the metal electrodes 3 of multiple stretchable electromagnetic ultrasonic guided wave sensors can be connected end to end and wrapped around the outer wall of the pipe 5, thus achieving the matching setting of thin pipes 5 with different diameters.

[0061] S12. An AC excitation signal is passed into the stretchable electromagnetic ultrasonic guided wave sensor as the excitation end, and the reflected wave is received by the stretchable electromagnetic ultrasonic guided wave sensor as the receiving end, as detailed below:

[0062] When the stretchable electromagnetic ultrasonic guided wave sensor is used as the excitation end, the AC excitation signal is introduced through the wire into the metal electrode 3 and conducted to the liquid metal coil 2, generating induced eddy currents on the inner wall of the pipe 5. Under the action of the bias static magnetic field formed by the magnet 4 on the outer wall of the pipe 5, the induced eddy currents generate a force perpendicular to the radial direction of the pipe 5, and the vibration generates ultrasonic guided waves, such as... Figure 3 As shown, the guided wave propagates along the axial direction of pipe 5. When the ultrasonic guided wave encounters a defect, two situations will occur: reflection and transmission. The reflected wave will propagate in the opposite direction from the defect and return to the stretchable electromagnetic ultrasonic guided wave sensor along the incident wave propagation path. At this time, the stretchable electromagnetic ultrasonic guided wave sensor acts as the receiving end.

[0063] In this step, because an AC signal is introduced into the liquid metal, induced eddy currents will be generated on the surface of pipe 5 up to the skin depth, according to the principle of electromagnetic induction. The magnets 4 placed at both ends of the coil will generate a static bias magnetic field along the circumference of pipe 5, according to the formula: f L =B0×J e The Lorentz force is generated due to the interaction between the eddy current and the bias magnetic field. Where f L The force is the Lorentz force, B0 is the bias magnetic field, and J is the... eThe eddy current density is denoted as . For the receiving end, when the ultrasonic guided wave is transmitted to the sensor, the charged particles moving in the material under test in the area below the sensor generate an induced current under the action of the applied bias magnetic field. This current is dynamic and will generate a dynamic magnetic field in and around the material under test. The receiving coil of the electromagnetic ultrasonic sensor in this magnetic field will generate an induced electromotive force, which will convert the vibration mechanical signal into an electrical signal.

[0064] S13. Determine the propagation velocity of the guided wave based on the dispersion curve of pipe 5. Based on the time of AC excitation signal input, the time of received reflected wave, and the propagation velocity of the guided wave, determine the distance between the defect location in pipe 5 and the stretchable electromagnetic ultrasonic guided wave sensor, thereby completing the defect detection of pipe 5, as detailed below:

[0065] L=(t2-t1) / (2*v)

[0066] In the formula, v represents the propagation speed of the guided wave, t1 represents the excitation time, and t2 represents the time when the reflected wave is received.

[0067] The present invention also provides a method for preparing the above-mentioned stretchable electromagnetic ultrasonic guided wave sensor, comprising the following steps:

[0068] S21. Determine the size of the flexible substrate 1 based on the volume of the liquid metal coil 2, and determine the size of the mold based on the size of the flexible substrate 1.

[0069] S22. A solid coil with the same shape as the liquid metal coil 2 is wound from a solid material. This solid coil is easily corroded.

[0070] In this step, a suitable solid material is selected to make the solid coil. This material is easily corroded by a reagent, but the corrosive reagent will not corrode or damage the stretchable flexible material, and the solid material has good plasticity. For example, the solid coil can be made of iron wire, aluminum wire, etc., and the corrosive reagent can be nitric acid solution.

[0071] In this step, the solid material is used to wind the coil to create the desired shape. The shape is not limited to a zigzag coil, nor is it limited to a single coil. It can also be a spiral coil, a racetrack coil, or a combination of multiple spiral coils or a zigzag coil and a racetrack coil.

[0072] S23. Place the solid coil into the mold, pour in the liquid flexible stretchable material, and reserve the fluid inlet and fluid outlet. After the liquid flexible stretchable material solidifies, the flexible substrate 1 is obtained.

[0073] S24. Pour a corrosive agent into the fluid inlet of the flexible substrate 1 to corrode the solid coil, and pour it out from the corrosive fluid outlet. Rinse with clean water until there is no residual corrosive liquid, forming a cavity in the flexible substrate 1 that matches the shape of the liquid metal coil 2.

[0074] S26. Liquid metal is poured into the fluid inlet of the flexible substrate 1, and the fluid inlet and fluid outlet are sealed with a conductive solid material. Metal electrodes 3 are attached to the fluid inlet and fluid outlet. After the liquid metal solidifies, a liquid metal coil 2 is formed, and a stretchable electromagnetic ultrasonic guided wave sensor is obtained.

[0075] The stretchable electromagnetic ultrasonic guided wave sensor of the present invention uses a stretchable flexible substrate 1, which can be tightly coupled with pipes 5 of different sizes. During the measurement process, a magnet 4 can be installed on the outer wall of the pipe 5 to provide a bias static magnetic field for the liquid metal coil 2. After identifying the approximate location of the defect, the distance between the defect in the pipe 5 and the stretchable electromagnetic ultrasonic guided wave sensor can be determined, thereby realizing the location of the defect.

[0076] This invention locates defects by determining the distance between a stretchable electromagnetic ultrasonic guided wave sensor and the defect in pipe 5. It employs a stretchable flexible substrate 1 and a biased static magnetic field provided by a magnet 4, allowing the stretchable electromagnetic ultrasonic guided wave sensor to be installed at any position on pipe 5. During measurement, induced eddy currents are generated on the inner wall of pipe 5. Under the influence of the biased static magnetic field formed by the magnet 4 on the outer wall of pipe 5, these induced eddy currents generate a force perpendicular to the radial direction of pipe 5, vibrating to produce ultrasonic guided waves. This avoids interference from spurious signals and the influence of joint type, thus making defect location more accurate.

[0077] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of using a stretchable electromagnetic ultrasonic guided wave sensor, characterized in that, The stretchable electromagnetic ultrasonic guided wave sensor includes a flexible substrate with a cavity inside. A liquid metal coil, formed from liquid metal, is filled inside the cavity. Both ends of the liquid metal coil are connected to metal electrodes, which are respectively fixed to both ends of the flexible substrate. The method of use includes the following steps: A stretchable electromagnetic ultrasonic guided wave sensor is wrapped around the outer wall of the pipe along the circumference, and a magnet is installed on the outer wall of the pipe to provide a bias static magnetic field for the liquid metal coil. An AC excitation signal is passed through a stretchable electromagnetic ultrasonic guided wave sensor as the excitation end, and the reflected wave is received by the stretchable electromagnetic ultrasonic guided wave sensor as the receiving end. The propagation speed of the guided wave is determined based on the dispersion curve of the pipeline. The distance between the pipeline defect and the stretchable electromagnetic ultrasonic guided wave sensor is determined based on the time of AC excitation signal input, the time of receiving the reflected wave, and the propagation speed of the guided wave.

2. The method of using the stretchable electromagnetic ultrasonic guided wave sensor according to claim 1, characterized in that, An AC excitation signal is supplied to a stretchable electromagnetic ultrasonic guided wave sensor as the excitation end, and the reflected wave is received by the stretchable electromagnetic ultrasonic guided wave sensor as the receiving end, including: When the stretchable electromagnetic ultrasonic guided wave sensor is used as the excitation end, the AC excitation signal is introduced into the metal electrode through the wire and transmitted to the liquid metal coil, generating induced eddy currents on the inner wall of the pipe. Under the action of the bias static magnetic field formed by the magnet on the outer wall of the pipe, the induced eddy currents generate a force perpendicular to the radial direction of the pipe, and the vibration generates ultrasonic guided waves. The guided waves propagate along the axial direction of the pipe. When the ultrasonic guided waves encounter a defect, the reflected waves will propagate in the opposite direction from the defect and return to the stretchable electromagnetic ultrasonic guided wave sensor, which serves as the receiving end, along the propagation path of the incident wave.

3. The method of using the stretchable electromagnetic ultrasonic guided wave sensor according to claim 1, characterized in that, Based on the timing of the AC excitation signal input, the timing of the received reflected wave, and the propagation speed of the guided wave, the distance between the pipe defect and the stretchable electromagnetic ultrasonic guided wave sensor is determined, including: L = (t2 - t1) / (2 * v) Where v represents the propagation speed of the guided wave, t1 represents the excitation time, and t2 represents the time when the reflected wave is received.

4. The method of using the stretchable electromagnetic ultrasonic guided wave sensor according to claim 1, characterized in that, The metal electrodes are made of copper, aluminum, or silver.

5. The method of using the stretchable electromagnetic ultrasonic guided wave sensor according to claim 1, characterized in that, The liquid metal coil is a polygonal coil.

6. The method of using the stretchable electromagnetic ultrasonic guided wave sensor according to claim 1, characterized in that, The flexible substrate is strip-shaped, and the metal electrode is square plate-shaped.

7. A method for fabricating a stretchable electromagnetic ultrasonic guided wave sensor, characterized in that, The method for preparing the stretchable electromagnetic ultrasonic guided wave sensor according to any one of claims 1-6 comprises the following steps: To create a solid coil with the same shape as a liquid metal coil; The solid coil is placed into a mold, liquid flexible stretchable material is poured in, and a fluid inlet and a fluid outlet are reserved. After the liquid flexible stretchable material solidifies, a flexible substrate is obtained. The corrosive agent is poured into the fluid inlet of the flexible substrate to corrode the solid coil, and then poured out from the corrosive fluid outlet. The coil is then rinsed with clean water until no corrosive liquid remains, forming a cavity in the flexible substrate that matches the shape of the liquid metal coil. Liquid metal is injected into the fluid inlet of a flexible substrate, and the fluid inlet and outlet are sealed with a conductive solid material. Metal electrodes are attached to the fluid inlet and outlet. After the liquid metal solidifies, a liquid metal coil is formed, thus obtaining a stretchable electromagnetic ultrasonic guided wave sensor.

8. The method for fabricating the stretchable electromagnetic ultrasonic guided wave sensor according to claim 7, characterized in that, It also includes the following steps: The dimensions of the flexible substrate are determined based on the volume of the liquid metal coil, and the dimensions of the mold are determined based on the dimensions of the flexible substrate.

9. The method for fabricating the stretchable electromagnetic ultrasonic guided wave sensor according to claim 7, characterized in that, The solid coil is made of iron or aluminum wire, and the corrosion reagent is nitric acid solution.

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