A multi-modal fusion magnetostrictive ultrasonic guided wave sensing structure for small diameter pipes

Abstract

The application provides a multi-modal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes, which comprises two positioning seats symmetrically arranged on two opposite outer walls of the small-diameter pipe; each high-magnetostrictive strip is laid on the inner wall of the corresponding positioning seat and the outer wall of the small-diameter pipe; a flexible printed racetrack coil circuit board is tightly attached to the surface of the middle part of the corresponding high-magnetostrictive strip and extends in the direction parallel to the length of the small-diameter pipe; a positioning block is tightly pressed on the flexible printed racetrack coil circuit board and extends in the direction parallel to the length of the small-diameter pipe; two permanent magnets are tightly attached to the surfaces of the corresponding high-magnetostrictive strips and are respectively located on the opposite sides of the positioning block; and two small switch circuit boards are respectively electrically connected to the flexible printed racetrack coil circuit boards on the two sensors. The structure can excite or receive axisymmetric and bending mode guided waves respectively, and greatly improves the guided wave detection capability of the small-diameter pipe.

Description

Technical Field

[0001] This application relates to the field of pipeline non-destructive testing, and in particular to a multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes. Background Technology

[0002] Small-diameter pipelines are widely used in industries such as petrochemicals, nuclear power, and aerospace for transporting liquids and gases. However, due to factors such as corrosion, fatigue, and stress damage during long-term operation, small-diameter pipelines are prone to defects, thus threatening equipment safety. Therefore, developing efficient and convenient non-destructive testing technologies is crucial for the health monitoring of small-diameter pipelines.

[0003] Ultrasonic guided wave detection technology has become an important means of monitoring pipeline structural health due to its long-distance propagation, high sensitivity, and full-section coverage capability. Among them, magnetostrictive ultrasonic guided wave sensors have high energy conversion efficiency and can easily excite torsional mode guided waves, leading to their widespread research and application in pipeline inspection. However, small-diameter pipes have a small outer surface curvature radius, resulting in a small contact area between the sensor and the pipe, significantly reducing the sensor's transduction efficiency. Furthermore, traditional sensors typically only excite axisymmetric mode guided waves, making it difficult to excite pure bending mode guided waves. However, the circumferential focusing characteristics of bending mode guided waves can provide more information about the pipeline's health status. Conversely, traditional magnetostrictive sensors can usually only excite or receive a single mode of ultrasonic guided wave, making it difficult to comprehensively assess the pipeline's health status. Summary of the Invention

[0004] One of the objectives of this application is to provide a multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes, aiming to solve the problem of poor comprehensive assessment of the health status of existing small-diameter pipes.

[0005] The technical solution of this application is: a multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes, comprising two sensors; the two sensors are symmetrically arranged on the outer wall of the small-diameter pipe, and each includes a positioning seat, a highly magnetostrictive strip, a flexible printed racetrack-shaped coil circuit board, a positioning block, two permanent magnets, and a small switch circuit board; the two positioning seats are symmetrically arranged on two opposite outer walls of the small-diameter pipe; each highly magnetostrictive strip is laid on the inner wall of the corresponding positioning seat and the outer wall of the small-diameter pipe; the flexible printed racetrack-shaped coil circuit board is closely attached to the surface of the middle part of the corresponding highly magnetostrictive strip and extends in a direction parallel to the length of the small-diameter pipe, and is used to excite and receive dynamic magnetic fields; the positioning block is pressed tightly against the flexible printed racetrack-shaped coil circuit board. The two permanent magnets are attached to the surfaces of the corresponding high magnetostrictive strips and are located on opposite sides of the positioning blocks, and are parallel to the corresponding positioning blocks, in order to generate a static magnetic field. The small switch circuit board is electrically connected to the flexible printed racetrack-shaped coil circuit boards on the two sensors, and is used to control the working mode of the sensors by controlling the direction of the current. When the flexible printed racetrack-shaped coil circuit boards on the two sensors are supplied with alternating current in the same direction, an axisymmetric mode ultrasonic guided wave is excited in the axial direction of the small-diameter pipe. When the flexible printed racetrack-shaped coil circuit boards on the two sensors are supplied with alternating current in opposite directions, an axial bending mode ultrasonic guided wave is excited in the axial direction of the small-diameter pipe.

[0006] As one technical solution of this application, the positioning seat is provided with a limiting port that cooperates with the small-diameter pipe; the small-diameter pipe is snapped into the limiting ports on the two sensors; the high magnetostrictive strip is tightly attached to the outer wall of the small-diameter pipe; and the positioning block is located at the limiting port.

[0007] As one technical solution of this application, the positioning seat includes two side plates, a connecting plate, and two limiting plates; the two limiting plates are arranged alternately and together form the limiting opening; the two side plates are arranged alternately and are respectively disposed on the opposite side of the corresponding limiting plates; the connecting plate is perpendicularly connected to the two side plates and the two limiting plates respectively.

[0008] As one technical solution of this application, the relationship between the racetrack-shaped coil in the flexible printed racetrack-shaped coil circuit board and the wavelength of the ultrasonic guided wave is as follows:

[0009]

[0010] In the formula: L is the center-to-center distance between the upper and lower racetrack-shaped coils in the flexible printed racetrack-shaped coil circuit board; λ is the wavelength of the ultrasonic guided wave; and C is the phase velocity of the ultrasonic guided wave.

[0011] As one technical solution of this application, the relationship between the width of the highly magnetostrictive strip and the ultrasonic guided wave is as follows:

[0012]

[0013] In the formula: w is the width of the high magnetostrictive strip; λ is the wavelength of the ultrasonic guided wave; v is the velocity of the ultrasonic guided wave; and f is the frequency of the ultrasonic guided wave.

[0014] As one technical solution of this application, the material of the high magnetostrictive strip includes an iron-cobalt-nickel alloy.

[0015] As one technical solution of this application, a limiting groove matching the small-diameter pipe is provided on one surface of the positioning block.

[0016] As one technical solution of this application, the flexible printed runway-shaped coil circuit board includes a first circuit board, a second circuit board, an arc-shaped circuit board, a third circuit board, and a fourth circuit board connected in sequence; the first circuit board is perpendicularly connected to the second circuit board; the second circuit board is connected to the arc-shaped circuit board at an obtuse angle; the third circuit board is connected to the arc-shaped circuit board at an obtuse angle; and the fourth circuit board is perpendicularly connected to the third circuit board.

[0017] As one technical solution of this application, it also includes two housings for mounting the sensor; the two housings are respectively symmetrically arranged on the outer wall of the small-diameter pipe; the sensor is detachably installed in the inner cavity of the corresponding housing.

[0018] As a technical solution of this application, each of the housings is provided with an arc-shaped groove for engaging with the small-diameter pipe, and guide rails matching the positioning seat are provided on the two opposite inner walls; the two opposite outer walls of the positioning seat are provided with slots for connecting with the guide rails; the positioning seat is detachably installed in the corresponding housing through the slots and the guide rails.

[0019] The beneficial effects of this application are:

[0020] This structure leverages the limited number of guided wave modes and the relatively simple structure of guided wave modes in small-diameter pipes. It innovatively achieves separate excitation or reception of axisymmetric and bending guided waves within a single sensor. Furthermore, by introducing a small switching circuit board into the sensor, convenient and flexible switching between axisymmetric and bending guided waves is realized. This multi-modal fusion design not only improves the applicability and detection accuracy of ultrasonic guided waves but also reduces the design and installation costs of different modal sensors, providing a more efficient and economical non-destructive testing solution for the health monitoring of small-diameter pipes. Simultaneously, this structure can excite and receive axisymmetric and bending guided waves within the same sensor group, adapting to the detection needs of different types of defects, thereby improving the comprehensiveness and accuracy of detection. Moreover, the sensor employs a stable and efficient magnetic field design, providing a uniform static magnetic field through a permanent magnet assembly, enhancing the magnetostrictive effect, and improving signal quality and detection stability. In addition, its split positioning base, flexible printed racetrack-shaped coil circuit board, and matching limiting port design for small-diameter pipes not only improve the ease of sensor installation but also optimize the energy transmission efficiency of ultrasonic guided waves. Therefore, this application achieves flexible switching between different ultrasonic guided wave modes by introducing a small switching circuit board as a mode switching mechanism, avoiding the need for additional design and installation of multiple sensors, thereby reducing the investment cost of detection equipment. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 A schematic diagram showing the connection between a multimodal fusion magnetostrictive ultrasonic waveguide sensing structure for small-diameter pipes and a small-diameter pipe, as provided in an embodiment of this application.

[0023] Figure 2 A schematic diagram of the first angle connecting the multimodal fusion magnetostrictive ultrasonic waveguide sensing structure for small-diameter pipes provided in this embodiment of the application to the small-diameter pipe;

[0024] Figure 3 A schematic diagram of a flexible printed racetrack-shaped coil circuit board provided in an embodiment of this application;

[0025] Figure 4 A schematic diagram of the circumferential current and magnetic field distribution in the axisymmetric mode provided in the embodiments of this application;

[0026] Figure 5 A schematic diagram of the circumferential current and magnetic field distribution in the bending mode provided in this application embodiment;

[0027] Figure 6 A schematic diagram of the switching circuit design provided in the embodiments of this application;

[0028] Figure 7 A schematic diagram of the dispersion curve of a 3 / 8-inch tube provided in an embodiment of this application;

[0029] Figure 8 This is a schematic diagram of the F(1,1) wave structure of a 3 / 8-inch pipe bending mode provided in an embodiment of this application;

[0030] Figure 9 This is a schematic diagram of the effect of axisymmetric modal ultrasonic guided wave provided in the embodiments of this application;

[0031] Figure 10 This is a schematic diagram of the ultrasonic waveguide effect of the bending mode F(1,1) provided in an embodiment of this application;

[0032] Figure 11 This is a schematic diagram of the housing provided for an embodiment of this application.

[0033] Icons: 1-Small diameter pipe; 2-Positioning seat; 3-High magnetostrictive strip; 4-Flexible printed racetrack-shaped coil circuit board; 5-Positioning block; 6-Permanent magnet; 7-Limiting port; 8-Housing; 9-Small switch circuit board. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0036] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0037] In the description of this application, it should be noted that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only used to facilitate the description of this application and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0038] Furthermore, in this application, unless otherwise expressly specified and limited, "above or below" the first feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Moreover, "above," "over," and "on" the first feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the first feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0039] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0040] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0041] Example:

[0042] Please refer to Figure 1 (Refer to) Figures 2 to 11This application provides a multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes. It can excite or receive axisymmetric and bending mode guided waves respectively, realizing multimodal fusion sensing of the health status of small-diameter pipes and significantly improving the guided wave detection capability of small-diameter pipes. Based on the magnetostrictive effect, it mainly includes two sensors and two housings 8 for mounting the sensors; the two housings 8 are symmetrically arranged on the outer wall of the small-diameter pipe 1; the sensors are detachably installed in the inner cavity of the corresponding housing 8. The system comprises two sensors symmetrically positioned on the outer wall of the small-diameter pipe 1. Each sensor includes a positioning base 2, a highly magnetostrictive strip 3, a flexible printed racetrack-shaped coil circuit board 4, a positioning block 5, two permanent magnets 6, and a small switch circuit board 9. The two positioning bases 2 are symmetrically positioned on opposite outer walls of the small-diameter pipe 1. Each highly magnetostrictive strip 3 is laid on the inner wall of the corresponding positioning base 2 and the outer wall of the small-diameter pipe 1. Furthermore, the flexible printed racetrack-shaped coil circuit board 4 is tightly attached to the surface of the middle portion of the corresponding highly magnetostrictive strip 3. Extending parallel to the length of the small-diameter pipe 1, and used to excite and receive dynamic magnetic fields; and, the positioning block 5 is pressed tightly against the flexible printed racetrack-shaped coil circuit board 4 and extends parallel to the length of the small-diameter pipe 1; two permanent magnets 6 are each in close contact with the surface of the corresponding high magnetostrictive strip 3, and are respectively located on opposite sides of the positioning block 5, and are parallel to the corresponding positioning block 5, to generate static magnetic fields; small switch circuit boards 9 are electrically connected to the flexible printed racetrack-shaped coil circuit boards 4 on the two sensors respectively, and are used to regulate the working mode of the sensors by controlling the direction of the current. The sensors are installed in pairs facing each other, and the small switch circuit boards 9 are used to control the direction of the current. Therefore, when the flexible printed racetrack-shaped coil circuit boards 4 on the two sensors are supplied with alternating current in the same direction, an axisymmetric mode ultrasonic guided wave is excited in the axial direction of the small-diameter pipe 1; when the flexible printed racetrack-shaped coil circuit boards 4 on the two sensors are supplied with alternating current in opposite directions, a bending mode ultrasonic guided wave is excited in the axial direction of the small-diameter pipe 1. This structure can flexibly switch between axisymmetric and bending modes within the same sensor group, enabling multi-mode fusion guided wave detection of small-diameter pipe defects and accurately meeting the detection requirements of different types of defects. The design employs a pair of sensors, with the operating state switched via a small switching circuit board 9, to achieve excitation and reception of axisymmetric and bending mode ultrasonic guided waves.

[0043] It should be noted that each housing 8 has an arc-shaped groove for engaging with the small-diameter pipe 1, and guide rails matching the positioning seat 2 are provided on the two opposite inner walls; the positioning seat 2 has slots for connecting with the guide rails on the two opposite outer walls; the positioning seat 2 is detachably installed in the corresponding housing 8 through the slots and guide rails.

[0044] It should be noted that the positioning base 2 includes two side plates, a connecting plate, and two limiting plates; the two limiting plates are arranged alternately and together form a limiting port 7, which cooperates with the small-diameter pipe 1; the two side plates are arranged alternately and are respectively set on the opposite sides of the corresponding limiting plates; the connecting plate is perpendicularly connected to the two side plates and the two limiting plates respectively. The small-diameter pipe 1 is snapped into the limiting ports 7 on the two sensors; the high magnetostrictive strip 3 is tightly attached to the outer wall of the small-diameter pipe 1; the positioning block 5 is located at the limiting port 7. The limiting port 7 is used to increase the contact area between the high magnetostrictive strip 3 and the small-diameter pipe 1, thereby improving the energy conversion efficiency.

[0045] It should be noted that the center-to-center distance between the two turns of the racetrack-shaped coil in the designed flexible printed racetrack-shaped coil circuit board 4 is adapted to the half-wavelength of the axisymmetric and bending modes being excited and received, in order to excite and receive pure ultrasonic guided wave modes. Specifically, the relationship between the racetrack-shaped coil in the flexible printed racetrack-shaped coil circuit board 4 and the wavelength of the ultrasonic guided wave is as follows:

[0046]

[0047] In the formula: L is the center-to-center distance between the upper and lower racetrack-shaped coils in the flexible printed racetrack-shaped coil circuit board 4; λ is the wavelength of the ultrasonic guided wave; and C is the phase velocity of the ultrasonic guided wave.

[0048] When designing a racetrack-shaped coil, ensuring that the spacing between the excitation and receiving coils is the same and that the above formula is satisfied can maximize the efficiency of the ultrasonic waves required for excitation and reception, while reducing ultrasonic signals of other modes.

[0049] It should be noted that the high magnetostrictive strip 3 is made of an iron-cobalt-nickel alloy, and its width is adapted to different excitation and reception frequencies to improve the conversion efficiency of the magnetostrictive effect. The relationship between the width and frequency of the iron-cobalt magnetostrictive strip is mainly affected by factors such as the magnetostrictive effect, wavelength, and ultrasonic guided wave mode. The relationship between its propagation wavelength and frequency is as follows: The relationship between the wavelength λ of the ultrasonic guided wave and its propagation velocity v and frequency f is:

[0050]

[0051] Here, v depends on the propagation speed of the torsional carrier (T) or bending mode (F), which is related to the pipe material and the waveguide mode.

[0052] The width w of the high magnetostrictive strip 3 directly affects the excitation and reception efficiency of the guided wave. Typically, the width of the high magnetostrictive strip 3 should match the excitation and reception wavelengths to ensure effective coupling of the ultrasonic guided wave by the magnetostrictive effect. To obtain a high-efficiency signal, the width of the high magnetostrictive strip 3 is approximately equal to or close to half the wavelength of the ultrasonic guided wave; that is, the relationship between the width of the high magnetostrictive strip 3 and the ultrasonic guided wave is:

[0053]

[0054] In the formula: w is the width of the high magnetostrictive strip 3; λ is the wavelength of the ultrasonic guided wave; v is the velocity of the ultrasonic guided wave; f is the frequency of the ultrasonic guided wave;

[0055] This allows for maximum utilization of the magnetostrictive effect to excite and receive guided waves of the target mode.

[0056] Furthermore, a limiting groove matching the small-diameter pipe 1 is provided on one surface of the positioning block 5.

[0057] Permanent magnet assemblies are arranged on both sides of the high magnetostrictive strip 3 to provide a stable static magnetic field for the sensor. Based on the excitation and reception frequencies, permanent magnets 6 that match the dynamic magnetic field strength are selected. The permanent magnet assemblies of the two pairs of sensors attract each other to form a uniform circumferential static magnetic field, enhancing the magnetostrictive effect.

[0058] Magnetostriction refers to the phenomenon where magnetic materials change shape under the influence of an external magnetic field. When an external magnetic field is applied to a magnetostrictive material, the magnetic domains inside the material rearrange, causing a change in its shape. If a magnetostrictive material is attached to the surface of a pipe and a regularly changing magnetic field is applied to it, the material will deform accordingly based on the change in the magnetic field. This deformation acts on the pipe, thereby exciting ultrasonic guided waves. In the sensor, a permanent magnet provides a static magnetic field with a fixed direction. By changing the direction of the coil current, the direction of the magnetic field in the high magnetostrictive strip 3 can be changed, thereby changing its deformation direction and enabling the excitation of ultrasonic guided waves in different modes.

[0059] It should be noted that, based on the frequency requirements, a permanent magnet 6 matching the strength of the dynamic magnetic field is selected to ensure the optimal effect of the magnetostrictive effect. It utilizes a permanent magnet assembly to provide a stable circumferential static magnetic field. The selection of a permanent magnet 6, matching the strength of the dynamic magnetic field, based on the excitation frequency requirements, ensures the excitation efficiency and signal quality of the ultrasonic guided wave.

[0060] Based on the inverse effect of magnetostriction, effective reception of ultrasonic guided waves can be achieved. When the ultrasonic guided wave propagates along the small-diameter pipe 1 and reaches the sensor, the displacement vibration caused by the guided wave will deform the highly magnetostrictive strip 3 attached to the surface of the small-diameter pipe 1. This deformation will further change the magnetic field distribution around the highly magnetostrictive strip 3. Due to the change in the magnetic field, a corresponding current signal will be induced in the racetrack-shaped coil connection of the flexible printed racetrack-shaped coil circuit board 4. By reading and analyzing the induced current in the racetrack-shaped coil connection, the reception and detection of ultrasonic guided waves can be achieved.

[0061] It should be noted that the flexible printed racetrack-shaped coil circuit board 4 includes a first circuit board, a second circuit board, an arc-shaped circuit board, a third circuit board, and a fourth circuit board connected in sequence; the first circuit board is perpendicularly connected to the second circuit board; the second circuit board is connected to the arc-shaped circuit board at an obtuse angle; the third circuit board is connected to the arc-shaped circuit board at an obtuse angle; and the fourth circuit board is perpendicularly connected to the third circuit board.

[0062] It should be noted that the small switching circuit board 9 consists of a signal source input, the racetrack-shaped coil input of the flexible printed racetrack-shaped coil circuit board 4 from the two sensors, and a synchronization switch. The synchronization switch is used to control the connection method of the second racetrack-shaped coil of the second flexible printed racetrack-shaped coil circuit board 4. The small switching circuit board 9 can adjust the current direction, and the switching between excitation and reception of ultrasonic guided wave modes is achieved according to the adjusted current direction. Figure 6 As shown, specifically:

[0063] When the synchronous switch is turned on upward, the positive and negative terminals of the second racetrack-shaped coil of the second flexible printed racetrack-shaped coil circuit board 4 are directly connected to the positive and negative terminals of the signal source, forming forward conduction; therefore, the alternating currents passed through the racetrack-shaped coils of the two sensors are in the same direction, and the sensors can excite and receive axisymmetric mode ultrasonic guided waves.

[0064] When the synchronous switch is turned down, the negative terminal of the second racetrack-shaped coil of the second flexible printed racetrack-shaped coil circuit board 4 is connected to the first racetrack-shaped coil of the first flexible printed racetrack-shaped coil circuit board 4 and the positive terminal of the power supply, while the positive terminal of the second racetrack-shaped coil of the second flexible printed racetrack-shaped coil circuit board 4 is connected to the first racetrack-shaped coil of the first flexible printed racetrack-shaped coil circuit board 4 and the negative terminal of the power supply, forming reverse conduction; therefore, the alternating currents flowing through the racetrack-shaped coils of the two sensors are reversed, and the sensors can excite and receive bending mode ultrasonic guided waves.

[0065] When two sensors are supplied with current in the same direction, the dynamic magnetic fields generated by the racetrack-shaped coils on the flexible printed racetrack-shaped coil circuit board 4 in both sensors are in the same direction, along the same axis. Figure 4As shown. At this time, the static bias magnetic field provided by the permanent magnet remains fixed, and the deformation of the high magnetostrictive strip 3 mainly depends on the change of the dynamic magnetic field. The deformation changing in the same direction enables the sensor to excite and receive axisymmetric mode ultrasonic guided waves.

[0066] like Figure 5 As shown, when reverse currents are applied to the two sensors, the dynamic magnetic fields generated by the racetrack-shaped coils on the flexible printed racetrack-shaped coil circuit board 4 in the two sensors are in opposite directions, one along the positive axial direction and the other along the negative axial direction, 180° opposite. At this time, the static bias magnetic field provided by the permanent magnet remains fixed, and the deformation direction of the high magnetostriction strip 3 of the first sensor is 180° opposite to the deformation direction of the high magnetostriction strip 3 of the second sensor. The deformations of both act together in one circumferential direction, thereby enabling the sensor to excite and receive ultrasonic guided waves in bending modes.

[0067] Based on the above principle, the direction of current can be adjusted by the small switching circuit board 9, allowing for flexible switching between axisymmetric and bending modes within the same sensor group. Figure 6 The small switch circuit board 9 is shown, and its function is to control the energizing direction of the racetrack-shaped coil on the flexible printed racetrack-shaped coil circuit board 4, thereby achieving the switching of different ultrasonic guided wave modes. Specifically, Figure 6 In the first flexible printed racetrack-shaped coil circuit board 4, the positive and negative terminals of the first racetrack-shaped coil are directly connected to the positive and negative terminals of the signal source. When the synchronous switch is turned on upwards, the positive and negative terminals of the second flexible printed racetrack-shaped coil circuit board 4 are directly connected to the positive and negative terminals of the signal source, forming forward conduction, and the current flows in the direction shown in the diagram. Figure 4 As shown; in this state, the racetrack-shaped coil of the sensor's flexible printed racetrack-shaped coil circuit board 4 is supplied with a co-current alternating current to excite and receive axisymmetric modes. When the synchronous switch is turned down, the negative terminal of the second racetrack-shaped coil of the second flexible printed racetrack-shaped coil circuit board 4 is connected to the first racetrack-shaped coil of the first flexible printed racetrack-shaped coil circuit board 4 and the positive terminal of the power supply, while the positive terminal of the second racetrack-shaped coil of the second flexible printed racetrack-shaped coil circuit board 4 is connected to the first racetrack-shaped coil of the first flexible printed racetrack-shaped coil circuit board 4 and the negative terminal of the power supply, forming reverse conduction, and the current flows as shown. Figure 5 As shown; in this state, the racetrack-shaped coil of the sensor's flexible printed racetrack-shaped coil circuit board 4 is supplied with a reverse alternating current to excite and receive bending modes.

[0068] Furthermore, in this embodiment, a defect-free 304 stainless steel tube with an outer diameter of 3 / 8 inch (9.6 mm) and a length of 1.5 m was selected to verify the sensor's performance in ultrasonic guided wave mode conversion. Figure 7As shown, the small-diameter pipe 1 has a relatively small number of guided wave modes near the 64kHz frequency, and the mode structure is relatively simple. This provides ideal conditions for exciting and receiving torsional and bending modes F(1,1) ultrasonic guided waves at this frequency. At 64kHz, the velocity of the torsional mode T(0,1) is 3066m / s, and the velocity of the bending mode F(1,1) is 2380m / s. The wave structure of the bending mode F(1,1) is as follows... Figure 8 As shown, its tangential and radial displacements are both large. This characteristic enables this mode to effectively detect axial and radial defects in pipelines, exhibiting high detection sensitivity.

[0069] Figure 9 The effect of axisymmetric mode ultrasonic guided waves at a frequency of 64 kHz was demonstrated, with a wave velocity consistent with the theoretical velocity of 3066 m / s. Furthermore, from... Figure 9 Multiple end-face reflection echoes can be clearly observed, and the signal noise generated by the sensor is relatively small, indicating that the sensor has a high signal-to-noise ratio and strong practicality in practical applications.

[0070] Similarly, Figure 10 The effect of the sensor on bending mode ultrasonic guided waves at a frequency of 64 kHz was demonstrated, with a wave velocity consistent with the theoretical velocity of 2038 m / s. The wave structure was clear with minimal clutter, further validating the stability and reliability of the sensor across different modes. These experimental results demonstrate that the sensor can efficiently excite and receive ultrasonic guided waves of multiple modes at specific frequencies, meeting the needs of detecting various types of defects.

[0071] Therefore, this multi-modal fusion magnetostrictive ultrasonic guided wave sensor for small-diameter pipes can excite and receive axisymmetric and bending modes of ultrasonic guided waves within the same sensor group, adapting to the detection needs of different types of defects and thus improving the comprehensiveness and accuracy of detection. The sensor employs a stable and efficient magnetic field design, providing a uniform static magnetic field through a permanent magnet array to enhance the magnetostrictive effect and improve signal quality and detection stability.

[0072] Furthermore, this application utilizes a mode-switching mechanism to achieve flexible switching between different ultrasonic guided wave modes, avoiding the need for additional design and installation of multiple sensors, thereby reducing the investment cost of detection equipment. Since magnetostrictive sensors are suitable for complex operating conditions such as high temperature, high pressure, and liquid media, their engineering adaptability is significantly improved, expanding their application scope in fields such as petrochemicals, nuclear industry, and aerospace. Simultaneously, this application has broad application prospects in the health monitoring of small-diameter pipelines, providing an efficient and low-cost non-destructive testing solution for pipeline structural safety assessment and maintenance.

[0073] In summary, this structure leverages the limited number of guided wave modes and the relatively simple structure of guided wave modes in small-diameter pipes. It innovatively achieves separate excitation or reception of axisymmetric and bending guided waves within a single sensor. Furthermore, by introducing a small switching circuit board 9 into the sensor, convenient and flexible switching between axisymmetric and bending guided waves is realized. This multi-modal fusion design not only improves the applicability and detection accuracy of ultrasonic guided waves but also reduces the design and installation costs of different modal sensors, providing a more efficient and economical non-destructive testing solution for the health monitoring of small-diameter pipes. Simultaneously, this structure can excite and receive axisymmetric and bending guided waves within the same sensor group, adapting to the detection needs of different types of defects, thereby improving the comprehensiveness and accuracy of detection. Moreover, the sensor employs a stable and efficient magnetic field design, providing a uniform static magnetic field through a permanent magnet assembly, enhancing the magnetostrictive effect, and improving signal quality and detection stability. Furthermore, the design of its split positioning base 2, flexible printed racetrack-shaped coil circuit board 4, and limiting port 7 that matches the small-diameter pipe 1 not only improves the ease of sensor installation but also optimizes the energy transmission efficiency of ultrasonic guided waves. Therefore, this application, by introducing a mode-switching mechanism such as a small switching circuit board 9, achieves flexible switching between different ultrasonic guided wave modes, avoiding the need for additional design and installation of multiple sensors, thereby reducing the investment cost of the detection equipment.

[0074] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes, characterized in that, The device includes two sensors; the two sensors are symmetrically arranged on the outer wall of a small-diameter pipe, and each sensor includes a positioning seat, a highly magnetostrictive strip, a flexible printed racetrack-shaped coil circuit board, a positioning block, two permanent magnets, and a small switch circuit board; the two positioning seats are symmetrically arranged on two opposite outer walls of the small-diameter pipe; each highly magnetostrictive strip is laid on the inner wall of the corresponding positioning seat and the outer wall of the small-diameter pipe; the flexible printed racetrack-shaped coil circuit board is closely attached to the surface of the middle part of the corresponding highly magnetostrictive strip and extends in a direction parallel to the length of the small-diameter pipe, and is used to excite and receive dynamic magnetic fields; the positioning block is pressed tightly against the flexible printed racetrack-shaped coil circuit board and extends in a direction parallel to the length of the small-diameter pipe. Extending in parallel directions; both permanent magnets are tightly attached to the surfaces of the corresponding high magnetostrictive strips and are located on opposite sides of the positioning blocks, and are parallel to the corresponding positioning blocks, to generate a static magnetic field; the small switch circuit board is electrically connected to the flexible printed racetrack-shaped coil circuit boards on the two sensors, and is used to control the working mode of the sensors by controlling the direction of the current; when the flexible printed racetrack-shaped coil circuit boards on the two sensors are supplied with alternating current in the same direction, an axisymmetric mode ultrasonic guided wave is excited in the axial direction of the small-diameter pipe; when the flexible printed racetrack-shaped coil circuit boards on the two sensors are supplied with alternating current in opposite directions, a bending mode ultrasonic guided wave is excited in the axial direction of the small-diameter pipe.

2. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 1, characterized in that, The positioning seat has a limiting port that matches the small-diameter pipe; the small-diameter pipe is engaged in the limiting ports on the two sensors; the high magnetostrictive strip is tightly attached to the outer wall of the small-diameter pipe; and the positioning block is located at the limiting port.

3. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 2, characterized in that, The positioning base includes two side plates, a connecting plate, and two limiting plates; the two limiting plates are arranged alternately and together form the limiting opening; the two side plates are arranged alternately and are respectively disposed on the opposite side of the corresponding limiting plates; the connecting plate is perpendicularly connected to the two side plates and the two limiting plates respectively.

4. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 1, characterized in that, The relationship between the racetrack-shaped coil in the flexible printed racetrack-shaped coil circuit board and the wavelength of the ultrasonic guided wave is as follows: In the formula: L is the center-to-center distance between the upper and lower racetrack-shaped coils in the flexible printed racetrack-shaped coil circuit board; λ is the wavelength of the ultrasonic guided wave; and C is the phase velocity of the ultrasonic guided wave.

5. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 4, characterized in that, The relationship between the width of the highly magnetostrictive strip and the ultrasonic guided wave is as follows: In the formula: w is the width of the high magnetostrictive strip; λ is the wavelength of the ultrasonic guided wave; v is the velocity of the ultrasonic guided wave; and f is the frequency of the ultrasonic guided wave.

6. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 1, characterized in that, The material of the high magnetostrictive strip includes an iron-cobalt-nickel alloy.

7. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 1, characterized in that, A limiting groove matching the small-diameter pipe is provided on one surface of the positioning block.

8. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 1, characterized in that, The flexible printed racetrack-shaped coil circuit board includes a first circuit board, a second circuit board, an arc-shaped circuit board, a third circuit board, and a fourth circuit board connected in sequence; the first circuit board is perpendicularly connected to the second circuit board; the second circuit board is connected to the arc-shaped circuit board at an obtuse angle; the third circuit board is connected to the arc-shaped circuit board at an obtuse angle; and the fourth circuit board is perpendicularly connected to the third circuit board.

9. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 1, characterized in that, It also includes two housings for mounting the sensor; the two housings are symmetrically arranged on the outer wall of the small-diameter pipe; the sensor is detachably installed in the inner cavity of the corresponding housing.

10. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 9, characterized in that, Each of the housings has an arc-shaped groove for engaging with the small-diameter pipe, and guide rails matching the positioning seat are provided on the two opposite inner walls; the two opposite outer walls of the positioning seat have slots for connecting with the guide rails; the positioning seat is detachably installed in the corresponding housing through the slots and the guide rails.

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