Multi-mode fusion magnetostriction ultrasonic guided wave sensing structure for small-diameter tube

Abstract

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

Description

Technical Field

[0001] This application relates to the field of non-destructive testing of pipelines, and particularly to a multi-modal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes. Background Art

[0002] In industries such as petrochemical, nuclear, and aerospace, small-diameter pipelines are widely used for the transportation of liquids and gases. However, affected by factors such as corrosion, fatigue, and stress damage during long-term operation, small-diameter pipelines are extremely prone to defects, thus threatening the safety of equipment. Therefore, the development of efficient and convenient non-destructive testing technologies is crucial for the health monitoring of small-diameter pipelines.

[0003] The ultrasonic guided wave detection technology has become an important means for the health monitoring of pipeline structures due to its long-distance propagation, high sensitivity, and full-section coverage capabilities. Among them, magnetostrictive ultrasonic guided wave sensors have high energy conversion efficiency and can conveniently excite torsional mode guided waves, and have been widely studied and applied in the field of pipeline detection. The outer surface curvature radius of small-diameter pipes is small, and the contact area between the sensor and the pipe is small, which greatly reduces the transducer efficiency of the sensor. In addition, traditional sensors can usually only excite axisymmetric mode guided waves and it is difficult to excite pure bending mode guided waves, but the circumferential focusing and other characteristics of bending mode guided waves can provide more pipeline health status information. However, traditional magnetostrictive sensors can usually only excite or receive ultrasonic guided waves of a single mode, and it is difficult to comprehensively evaluate the health status of pipelines. Summary of the Invention

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

[0005] The technical solution of this application is: A multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes, including two sensors; the two sensors are symmetrically arranged on the outer wall of the small-diameter pipe respectively, 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 the two opposite outer walls of the small-diameter pipe respectively; 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 along the direction parallel to the length of the small-diameter pipe, and is used for exciting and receiving a dynamic magnetic field: the positioning block presses tightly on the flexible printed racetrack-shaped coil circuit board and extends along the direction parallel to the length of the small-diameter pipe; the two permanent magnets are both closely attached to the surface of the corresponding highly magnetostrictive strip and are respectively outside the opposite sides of the positioning block, and are both parallel to the corresponding positioning block, so as 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 respectively, and is used for regulating the working mode of the sensors by controlling the current direction; when the flexible printed racetrack-shaped coil circuit boards on the two sensors are passed through with the same-direction alternating current, ultrasonic guided waves in the axial symmetry mode are excited in the small-diameter pipe; when the flexible printed racetrack-shaped coil circuit boards on the two sensors are passed through with the reverse-direction alternating current, ultrasonic guided waves in the bending mode are excited in the axial direction of the small-diameter pipe.

[0006] As a technical solution of this application, a limit through hole matching with the small-diameter pipe is opened on the positioning seat; the small-diameter pipe is clamped in the limit through holes on the two sensors; the highly magnetostrictive strip is closely attached to the outer wall of the small-diameter pipe; the positioning block is located at the limit through hole.

[0007] As a technical solution of this application, the positioning seat includes two side plates, a connecting plate and two limit plates; the two limit plates are arranged at intervals and jointly form the limit through hole; the two side plates are arranged at intervals and are respectively arranged on the sides far away from each other of the corresponding limit plates; the connecting plate is vertically connected to the two side plates and the two limit plates respectively.

[0008] As a 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] Where: L is the center distance between the upper and lower runway-shaped coils in the flexible printed runway-shaped coil circuit board; λ is the wavelength of the ultrasonic guided wave; C is the phase velocity of the ultrasonic guided wave.

[0011] As a technical solution of the present application, the relationship between the width of the highly magnetostrictive strip and the ultrasonic guided wave is:

[0012]

[0013] Where: w is the width of the highly magnetostrictive strip; 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.

[0014] As a technical solution of the present application, the material of the highly magnetostrictive strip includes an iron-cobalt-nickel alloy material.

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

[0016] As a technical solution of the present 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 obtusely connected to the arc-shaped circuit board; the third circuit board is obtusely connected to the arc-shaped circuit board; the fourth circuit board is perpendicularly connected to the third circuit board.

[0017] As a technical solution of the present application, it further includes two housings for loading the sensors; the two housings are respectively symmetrically arranged on the outer wall of the small-diameter pipeline; the sensor is detachably installed in the inner cavity of the corresponding housing.

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

[0019] The beneficial effects of the present application:

[0020] This structure takes advantage of the characteristics of fewer guided wave modes in small-diameter pipes and relatively simple guided wave mode structures. It innovatively realizes the separate excitation or reception of axisymmetric mode guided waves and flexural mode guided waves within a single sensor. By introducing a small switch circuit board into the sensor, it enables convenient and flexible switching between axisymmetric mode and flexural mode guided waves. This multi-modal fusion design structure not only improves the applicability and detection accuracy of ultrasonic guided waves but also reduces the design and installation costs of different mode sensors, providing a more efficient and economical non-destructive testing solution for the health monitoring of small-diameter pipelines. At the same time, this structure can excite and receive ultrasonic guided waves in axisymmetric mode and flexural mode within the same sensor group, adapting to the detection requirements of different types of defects, thereby improving the comprehensiveness and accuracy of detection. Moreover, this sensor adopts a stable and efficient magnetic field design, providing a uniform static magnetic field through a permanent magnet group, enhancing the magnetostrictive effect, and improving signal quality and detection stability. In addition, the design of its split positioning seat, flexible printed runway-shaped coil circuit board, and limit through-hole matching the small-diameter pipeline not only improves the installation convenience of the sensor but also optimizes the energy transmission efficiency of ultrasonic guided waves. Therefore, this application realizes the flexible conversion of different ultrasonic guided wave modes by introducing a modal switching mechanism structure of a small switch circuit board, avoiding the additional design and installation of multiple sensors, and thus reducing the input cost of detection equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 Schematic diagram of the connection between the multi-modal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes provided by the embodiment of the present application and the small-diameter pipeline;

[0023] Figure 2 Schematic diagram of the first angle of the connection between the multi-modal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes provided by the embodiment of the present application and the small-diameter pipeline;

[0024] Figure 3 Schematic diagram of the flexible printed runway-shaped coil circuit board provided by the embodiment of the present application;

[0025] Figure 4 Schematic diagram of the circumferential current and magnetic field distribution in axisymmetric mode provided by the embodiment of the present application;

[0026] Figure 5 Schematic diagram of the circumferential current and magnetic field distribution in flexural mode provided by the embodiment of the present application;

[0027] Figure 6 Schematic diagram of the switch circuit design provided by the embodiment of the present application;

[0028] Figure 7 Schematic diagram of the dispersion curve of the 3 / 8-inch pipe provided by the embodiment of the present application;

[0029] Figure 8 Schematic diagram of the F(1,1) wave structure of the bending mode of the 3 / 8-inch pipeline provided by the embodiment of the present application;

[0030] Figure 9 Schematic diagram of the effect of axisymmetric mode ultrasonic guided wave provided by the embodiment of the present application;

[0031] Figure 10 Schematic diagram of the effect of the bending mode F(1,1) ultrasonic guided wave provided by the embodiment of the present application;

[0032] Figure 11 Schematic diagram of the housing provided by the embodiment of the present application.

[0033] Icon: 1 - small-diameter pipeline; 2 - positioning seat; 3 - high magnetostrictive strip; 4 - flexible printed track-shaped coil circuit board; 5 - positioning block; 6 - permanent magnet; 7 - limiting through hole; 8 - housing; 9 - small switch circuit board. Detailed implementation manners

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

[0035] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application claimed, but merely represents the selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0036] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0037] In the description of this application, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is customarily placed during use. This is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0038] In addition, in this application, unless otherwise clearly specified and defined, the first feature being above or below the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween. Moreover, the first feature being above, over, and on the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being below, under, and beneath the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0039] In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging vertically, but may be slightly inclined. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but may be slightly inclined.

[0040] In the description of this application, it should also be noted that, unless otherwise clearly specified and defined, the terms "set", "connected", and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0041] Embodiment:

[0042] Please refer to Figure 1 and, in conjunction with reference to Figures 2 to 11, this application provides a multi-modal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes, which can respectively excite or receive axisymmetric and flexural mode guided waves, realizing multi-modal fusion perception of the health state of small-diameter pipes and greatly improving the guided wave detection ability of small-diameter pipes. It is designed based on the magnetostrictive effect and mainly includes two sensors and two housings 8 for loading the sensors; the two housings 8 are symmetrically arranged on the outer wall of the small-diameter pipe 1 respectively; the sensors are detachably installed in the inner cavities of the corresponding housings 8. Among them, the two sensors are symmetrically arranged on the outer wall of the small-diameter pipe 1 respectively, and each sensor includes a positioning seat 2, a high magnetostrictive strip 3, a flexible printed raceway-shaped coil circuit board 4, a positioning block 5, two permanent magnets 6 and a small switch circuit board 9; among them, the two positioning seats 2 are symmetrically arranged on the two opposite outer walls of the small-diameter pipe 1 respectively; at the same time, each high magnetostrictive strip 3 is laid on the inner wall of the corresponding positioning seat 2 and the outer wall of the small-diameter pipe 1; in addition, the flexible printed raceway-shaped coil circuit board 4 is closely attached to the surface of the middle part of the corresponding high magnetostrictive strip 3 and extends along the direction parallel to the length of the small-diameter pipe 1, and is used for exciting and receiving the dynamic magnetic field: and, the positioning block 5 presses tightly on the flexible printed raceway-shaped coil circuit board 4 and extends along the direction parallel to the length of the small-diameter pipe 1; the two permanent magnets 6 are both closely attached to the surface of the corresponding high magnetostrictive strip 3 and are respectively outside the opposite sides of the positioning block 5 and are both parallel to the corresponding positioning block 5 for generating a static magnetic field; the small switch circuit board 9 is electrically connected to the flexible printed raceway-shaped coil circuit boards 4 on the two sensors respectively and is used for regulating the working mode of the sensors by controlling the current direction. The sensors are installed in pairs facing each other, and the small switch circuit board 9 is used for controlling the current direction. Therefore, when the flexible printed raceway-shaped coil circuit boards 4 on the two sensors are passed through with the same-direction alternating current, axisymmetric mode ultrasonic guided waves are excited in the axial direction of the small-diameter pipe 1; when the flexible printed raceway-shaped coil circuit boards 4 on the two sensors are passed through with the reverse-direction alternating current, flexural mode ultrasonic guided waves are excited in the axial direction of the small-diameter pipe 1. This structure can flexibly switch within the same sensor group and realize the excitation or reception of axisymmetric mode and flexural mode, realizing multi-modal fusion guided wave detection of small-diameter pipe defects and accurately meeting the detection requirements of different types of defects. This design uses a pair of sensors and switches the working state through the small switch circuit board 9 to realize the excitation and reception of axisymmetric mode and flexural mode ultrasonic guided waves.

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

[0044] It should be noted that the positioning seat 2 includes two side plates, a connecting plate, and two limiting plates; the two limiting plates are arranged at intervals and together form a limiting through-hole 7, which is matched with the small-diameter pipeline 1; the two side plates are arranged at intervals and are respectively arranged on the mutually remote 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 pipeline 1 is clamped in the limiting through-hole 7 on the two sensors; the high magnetostrictive strip 3 is closely attached to the outer wall of the small-diameter pipeline 1; the positioning block 5 is located at the limiting through-hole 7. The limiting through-hole 7 is used to increase the contact area between the high magnetostrictive strip 3 and the small-diameter pipeline 1 and improve the energy conversion efficiency.

[0045] It should be noted that the center distance between two turns of the wire of the racetrack-shaped coil in the designed flexible printed racetrack-shaped coil circuit board 4 is adapted to the half-wavelength of the axially symmetric mode and the bending mode excited and received, so as 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 distance between the upper and lower parts of the racetrack-shaped coil in the flexible printed racetrack-shaped coil circuit board 4; λ is the wavelength of the ultrasonic guided wave; C is the phase velocity of the ultrasonic guided wave.

[0048] When designing the racetrack-shaped coil, ensuring that the distances between the excitation and receiving coils are the same and satisfying the above formula can achieve the maximum efficiency of exciting and receiving the required ultrasonic waves, while weakening the ultrasonic wave signals of other modes.

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

[0050]

[0051] Among them, v depends on the propagation speed of the torsional carrier wave (T) or the bending mode (F), and this speed is related to the pipeline material and the guided wave mode.

[0052] The width w of the high magnetostrictive strip 3 directly affects the excitation and reception efficiency of guided waves; generally, the width of the high magnetostrictive strip 3 should match the excitation and reception wavelengths so that the magnetostrictive effect can effectively couple ultrasonic guided waves. To obtain efficient signals, the width of the high magnetostrictive strip 3 is approximately equal to or close to half of 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 as follows:

[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 can maximize the use of the magnetostrictive effect to excite and receive guided waves of the target mode.

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

[0057] The permanent magnet group is arranged on both sides of the high magnetostrictive strip 3 to provide a stable static magnetic field for the sensor. According to the excitation and reception frequencies, a permanent magnet 6 matching the dynamic magnetic field intensity is selected, and the permanent magnet groups of the two pairs of sensors attract each other to form a uniform circumferential static magnetic field, enhancing the magnetostrictive effect.

[0058] The magnetostrictive effect refers to the phenomenon that a magnetic material undergoes a shape change under the action of an external magnetic field. When an external magnetic field is applied to the magnetostrictive material, the magnetic domains inside the material will rearrange, resulting in a change in its shape. If the magnetostrictive material is attached to the pipeline surface and a regularly changing magnetic field excitation is applied to it, the material will generate corresponding deformations according to the changes in the magnetic field. This deformation acts on the pipeline, thereby exciting ultrasonic guided waves. In the sensor, the permanent magnet provides a static magnetic field in a fixed direction. By changing the direction of the coil current, the magnetic field direction of the high magnetostrictive strip 3 can be changed, and thus the deformation direction can be changed, so as to realize the excitation of ultrasonic guided waves in different modes.

[0059] It should be noted that according to the frequency requirements, a permanent magnet 6 matching the dynamic magnetic field intensity is selected to ensure the best effect of the magnetostrictive effect. It uses the permanent magnet group to provide a stable circumferential static magnetic field, and according to the requirements of the excitation frequency, a permanent magnet 6 matching the dynamic magnetic field intensity is selected to ensure the excitation efficiency and signal quality of the ultrasonic guided wave.

[0060] Based on the inverse magnetostrictive effect, the effective reception of ultrasonic guided waves can be achieved. When the ultrasonic guided wave propagates along the small-diameter pipeline 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 pipeline 1, and 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 coil connection of the flexible printed racetrack coil circuit board 4. By reading and analyzing the induced current in the racetrack coil connection, the reception and detection of ultrasonic guided waves can be realized.

[0061] It should be noted that the flexible printed racetrack 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; the fourth circuit board is perpendicularly connected to the third circuit board.

[0062] It should be noted that the small switch circuit board 9 consists of a signal source access port, the racetrack coil access ports of the flexible printed racetrack coil circuit boards 4 in two sensors, and a synchronous switch. The synchronous switch is used to control the access mode of the second racetrack coil of the second flexible printed racetrack coil circuit board 4. The small switch circuit board 9 can regulate the current direction to realize the switching of exciting and receiving ultrasonic guided wave modes according to the regulated current direction. As Figure 6 shown, specifically:

[0063] When the synchronous switch is turned on upward, the positive and negative poles of the second racetrack coil of the second flexible printed racetrack coil circuit board 4 are directly connected to the positive and negative poles of the signal source respectively, forming a forward conduction; therefore, the alternating currents passing through the racetrack coils of the flexible printed racetrack coil circuit boards 4 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 on downward, the negative pole of the second racetrack coil of the second flexible printed racetrack coil circuit board 4 is connected to the first racetrack coil of the first flexible printed racetrack coil circuit board 4 and the positive pole of the power supply, while the positive pole of the second racetrack coil of the second flexible printed racetrack coil circuit board 4 is connected to the first racetrack coil of the first flexible printed racetrack coil circuit board 4 and the negative pole of the power supply, forming a reverse conduction; therefore, the alternating currents passing through the racetrack coils of the flexible printed racetrack coil circuit boards 4 of the two sensors are in the opposite direction, and the sensors can excite and receive bending mode ultrasonic guided waves.

[0065] When the same-direction current is passed through the two sensors, the dynamic magnetic field directions generated by the racetrack coils of the flexible printed racetrack coil circuit boards 4 in the two sensors are the same, along the same axis as 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 that changes in the same direction enables the sensor to excite and receive ultrasonic guided waves in the axisymmetric mode.

[0066] As Figure 5 shown, when reverse currents are passed through the two sensors, the dynamic magnetic fields generated by the racetrack coils of the flexible printed racetrack coil circuit boards 4 in the two sensors are in opposite directions, one along the positive axial direction and the other along the negative axial direction, and the two are 180° opposite. At this time, the static bias magnetic field provided by the permanent magnet still remains fixed, and the deformation direction of the high magnetostrictive strip 3 of the first sensor is 180° opposite to the deformation direction of the high magnetostrictive strip 3 of the second sensor. The combined deformation of the two acts in one direction in the circumferential direction, thereby enabling the sensor to excite and receive ultrasonic guided waves in the bending mode.

[0067] According to the above principle, by adjusting the current direction through the small switch circuit board 9, the axisymmetric mode and the bending mode can be flexibly switched within the same sensor group. Figure 6 Shown is the small switch circuit board 9, whose function is to control the energization direction of the racetrack coils of the flexible printed racetrack coil circuit board 4 to achieve the switching of different ultrasonic guided wave modes. Specifically, Figure 6 in, the positive and negative poles of the first racetrack coil of the first flexible printed racetrack coil circuit board 4 are directly connected to the positive and negative poles of the signal source. When the synchronous switch is turned on upward, the positive and negative poles of the second racetrack coil of the second flexible printed racetrack coil circuit board 4 are respectively directly connected to the positive and negative poles of the signal source to form a forward conduction, and the current flow direction is as Figure 4 shown; in this state, the racetrack coils of the flexible printed racetrack coil circuit board 4 of the sensor are passed through with a same-direction alternating current for exciting and receiving the axisymmetric mode. When the synchronous switch is turned on downward, the negative pole of the second racetrack coil of the second flexible printed racetrack coil circuit board 4 is connected to the first racetrack coil of the first flexible printed racetrack coil circuit board 4 and the positive pole of the power supply, while the positive pole of the second racetrack coil of the second flexible printed racetrack coil circuit board 4 is connected to the first racetrack coil of the first flexible printed racetrack coil circuit board 4 and the negative pole of the power supply to form a reverse conduction, and the current flow direction is as Figure 5 shown; in this state, the racetrack coils of the flexible printed racetrack coil circuit board 4 of the sensor are passed through with a reverse alternating current for exciting and receiving the bending mode.

[0068] Furthermore, in this embodiment, a 304 stainless steel pipe with an outer diameter of 3 / 8 inch (9.6 mm) and a pipe length of 1.5 m without defects is selected to verify the performance of the sensor in terms of ultrasonic guided wave mode conversion. As Figure 7As shown, the small-diameter pipeline 1 has a small number of guided wave modes near the 64 kHz frequency, and the mode structure is relatively simple, which provides ideal conditions for exciting and receiving torsional mode and flexural mode F(1,1) ultrasonic guided waves at this frequency. At the 64 kHz frequency, the velocity of the torsional mode T(0,1) is 3066 m / s, and the velocity of the flexural mode F(1,1) is 2380 m / s. The wave structure of the flexural mode F(1,1) is as Figure 8 shown, and both its tangential displacement and radial displacement are relatively large. This characteristic enables this mode to effectively detect axial and radial defects in the pipeline, with relatively high detection sensitivity.

[0069] Figure 9 shows the effect of axisymmetric mode ultrasonic guided waves at the 64 kHz frequency, and the wave velocity is consistent with the theoretical velocity at 3066 m / s. Moreover, from Figure 9 it can be clearly observed that there are multiple end-face reflection echoes, and the clutter of the signals excited by the sensor is less, indicating that this sensor has a relatively high signal-to-noise ratio and strong practicability in practical applications.

[0070] Similarly, Figure 10 shows the effect of flexural mode ultrasonic guided waves at the 64 kHz frequency, and the wave velocity is consistent with the theoretical velocity at 2038 m / s. The wave structure is clear and the clutter is less, further verifying the stability and reliability of the sensor in different modes. These experimental results show that this sensor can efficiently excite and receive ultrasonic guided waves of multiple modes at specific frequencies, meeting the requirements for detecting different types of defects.

[0071] It can be seen from this that this multi-modal fusion magnetostrictive ultrasonic guided wave sensor for small-diameter pipelines can excite and receive ultrasonic guided waves of axisymmetric mode and flexural mode within the same sensor group, adapting to the detection requirements of different types of defects, thereby improving the comprehensiveness and accuracy of detection. This sensor adopts a stable and efficient magnetic field design, provides a uniform static magnetic field through a permanent magnet group, enhances the magnetostrictive effect, and improves the signal quality and detection stability.

[0072] In addition, through a mode switching mechanism in this application, flexible conversion of different ultrasonic guided wave modes is realized, avoiding the need for additional design and installation of multiple sensors, thereby reducing the investment cost of detection equipment. Since magnetostrictive sensors are applicable to complex working conditions such as high temperature, high pressure, and liquid media, their engineering adaptability is significantly improved, expanding the application scope in fields such as petrochemical industry, nuclear industry, and aerospace. At the same time, this application has broad application prospects in the health monitoring of small-diameter pipeline 1, providing an efficient and low-cost non-destructive testing solution for pipeline structure safety assessment and maintenance.

[0073] In summary, this structure takes advantage of the characteristics of fewer guided wave modes in small-diameter pipes and relatively simple guided wave mode structures. It innovatively realizes the separate excitation or reception of axisymmetric mode guided waves and bending mode guided waves within a single sensor. By introducing a small switch circuit board 9 into the sensor, convenient and flexible switching between axisymmetric mode and bending mode guided waves is achieved. This design structure with multimodal fusion not only improves the applicability and detection accuracy of ultrasonic guided waves but also reduces the design and installation costs of different mode sensors, providing a more efficient and economical non-destructive testing solution for the health monitoring of small-diameter pipelines 1. At the same time, this structure can excite and receive ultrasonic guided waves in axisymmetric mode and bending mode within the same sensor group, adapting to the detection requirements of different types of defects, thereby improving the comprehensiveness and accuracy of detection. Moreover, this sensor adopts a stable and efficient magnetic field design, providing a uniform static magnetic field through a permanent magnet group to enhance the magnetostrictive effect, improve signal quality and detection stability. In addition, the design of its split positioning seat 2, flexible printed runway-shaped coil circuit board 4, and the limiting through-hole 7 matching the small-diameter pipeline 1 not only improves the installation convenience of the sensor but also optimizes the energy transmission efficiency of ultrasonic guided waves. Therefore, this application realizes the flexible conversion of different ultrasonic guided wave modes through the structure of introducing a small switch circuit board 9 as a mode switching mechanism, avoiding the additional design and installation of multiple sensors, and thus reducing the input cost of detection equipment.

[0074] The above are only the preferred embodiments of this application and are not intended to limit this application. For those skilled in the art, various changes and modifications can be made to this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall 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 It includes two sensors; the two sensors are symmetrically arranged on the outer wall of the small-diameter pipeline respectively, and each includes a positioning seat, a high 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 the two opposite outer walls of the small-diameter pipeline respectively; each high magnetostrictive strip is laid on the inner wall of the corresponding positioning seat and the outer wall of the small-diameter pipeline; the flexible printed racetrack-shaped coil circuit board is closely attached to the surface of the middle part of the corresponding high magnetostrictive strip and extends along the direction parallel to the length of the small-diameter pipeline, and is used for exciting and receiving a dynamic magnetic field: the positioning block presses tightly on the flexible printed racetrack-shaped coil circuit board and extends along the direction parallel to the length of the small-diameter pipeline; the two permanent magnets are closely attached to the surface of the corresponding high magnetostrictive strip respectively, and are respectively located outside the opposite sides of the positioning block, and are both parallel to the corresponding positioning block, so as 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 respectively, and is used for regulating the working mode of the sensor by controlling the current direction; when the flexible printed racetrack-shaped coil circuit boards on the two sensors are fed with a same-direction alternating current, an axially symmetric mode of ultrasonic guided wave is excited in the axial direction of the small-diameter pipeline; when the flexible printed racetrack-shaped coil circuit boards on the two sensors are fed with a reverse-direction alternating current, a bending mode of ultrasonic guided wave is excited in the axial direction of the small-diameter pipeline.

2. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 1, wherein A limit through hole matching with the small-diameter pipeline is opened on the positioning seat; the small-diameter pipeline is clamped in the limit through holes on the two sensors; the high magnetostrictive strip is closely attached to the outer wall of the small-diameter pipeline; the positioning block is located at the limit through hole.

3. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 2, wherein The positioning seat includes two side plates, a connecting plate and two limiting plates; the two limiting plates are arranged at intervals and jointly form the limit through hole; the two side plates are arranged at intervals and are respectively arranged on the mutually remote sides of the corresponding limiting plates; the connecting plate is vertically 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 distance between the upper and lower parts of the racetrack-shaped coil in the flexible printed racetrack-shaped coil circuit board; λ is the wavelength of the ultrasonic guided wave; 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, wherein The relationship between the width of the high magnetostrictive strip and the ultrasonic guided wave is: 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; f is the frequency of the ultrasonic guided wave.

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

7. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 1, characterized in that, A limit groove matching with the small-diameter pipeline is arranged 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, wherein 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 that are 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; 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, wherein It further includes two housings for loading the sensors; the two housings are respectively symmetrically arranged on the outer wall of the small-diameter pipeline; the sensors are detachably installed in the inner cavities of the corresponding housings.

10. The multimodal fusion magnetostrictive ultrasonic guided wave sensing structure for small-diameter pipes according to claim 9, wherein Each of the housings is provided with an arc-shaped groove that is snap-connected to the small-diameter pipeline, and guide rails that are matched with the positioning seats are arranged on the opposite inner walls; clamping grooves for connecting with the guide rails are arranged on the opposite outer walls of the positioning seat; the positioning seat is detachably installed in the corresponding housing through the clamping grooves and the guide rails.

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