Magnetostriction longitudinal wave transducer structure capable of realizing static magnetic field adjustment

Abstract

The invention relates to the technical field of ultrasonic guided wave nondestructive testing, in particular to a magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field adjustment, which comprises a first circumferential static magnetic field array unit, a second circumferential static magnetic field array unit and an alternating magnetic field generation unit, the first circumferential static magnetic field array unit is formed on the periphery of one end of the to-be-detected piece and can generate a static magnetic field in the circumferential direction of the to-be-detected piece. And the second circumferential static magnetic field array unit is also formed on the periphery of one end of the to-be-detected piece, is arranged opposite to the first circumferential static magnetic field array unit, and can generate a static magnetic field in the circumferential direction of the to-be-detected piece. The second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit can move in opposite directions. The second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit can rotate relatively. The stability of the bias magnetic field is guaranteed, and the size of the static bias magnetic field can be accurately adjusted.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic guided wave nondestructive testing, and in particular to a magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation. Background Art

[0002] The grounding rods of transmission towers are made of steel with a circular cross-section. Because they remain buried beneath the surface for extended periods, corrosion and fracture are inevitable, threatening the safe operation of the power system and even the safety of workers. Therefore, regular inspection of grounding rods is essential. Conventional nondestructive testing methods, such as magnetic particle testing, X-ray testing, and eddy current testing, are not suitable for these complex working conditions. Magnetostrictive guided wave testing, however, can detect areas inaccessible to conventional testing and is therefore widely used for trenchless nondestructive testing of grounding rods.

[0003] The principle of magnetostrictive guided wave testing is to generate a magnetic field at one axial end of the grounding rod. This magnetic field, also known as the bias field, is used to excite longitudinal guided waves within the grounding rod and is a key element in defect detection. A bias field can be provided using a powered coil. While the magnitude of the field can be precisely adjusted to suit the specific application scenario, the resulting bias field is unstable and can cause electromagnetic interference to the guided wave receiving signal. Alternatively, a bias field can be provided using permanent magnets. While this field is sufficiently stable, the magnitude can only be adjusted in small increments by increasing or decreasing the number of permanent magnets, and precise adjustment is not possible.

[0004] Therefore, how to ensure the stability of the bias magnetic field and accurately adjust the magnitude of the bias magnetic field has become a technical problem that needs to be urgently solved by those skilled in the art. Summary of the invention

[0005] The present invention provides a magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation, so as to solve the problem of how to ensure the stability of the bias magnetic field and accurately adjust the magnitude of the bias magnetic field.

[0006] In one aspect, the present invention provides a magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation, comprising: A first circumferential static magnetic field array unit is formed on the periphery of the object to be detected; a second circumferential static magnetic field array unit, formed on the periphery of the to-be-detected component and arranged opposite to the first circumferential static magnetic field array unit; the second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit are movable toward each other; and the second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit are relatively rotatable; The alternating magnetic field generating unit is arranged between the second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit, and is wound around the periphery of the component to be detected.

[0007] In some of these embodiments, the second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit are capable of moving towards each other by 0 - 40 mm.

[0008] In some of these embodiments, the second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit are capable of rotating relative to each other by 0 - 20°.

[0009] In some of these embodiments, the first circumferential static magnetic field array unit includes: A plurality of first static magnetic field generating members, which are evenly distributed along the circumference of the first circumferential static magnetic field array unit; A plurality of second static magnetic field generating members, which are alternately arranged with the first static magnetic field generating members along the circumference of the first circumferential static magnetic field array unit; The second circumferential static magnetic field array unit includes: A plurality of third static magnetic field generating members, which are evenly distributed along the circumference of the second circumferential static magnetic field array unit; A plurality of fourth static magnetic field generating members, which are alternately arranged with the third static magnetic field generating members along the circumference of the second circumferential static magnetic field array unit; A part of the top of each third static magnetic field generating member covers a part of the top of a first static magnetic field generating member; a part of the top of each second static magnetic field generating member covers a part of the top of a fourth static magnetic field generating member.

[0010] In some of these embodiments, each first static magnetic field generating member includes: A first permanent magnet; A first converging yoke plate, fixedly installed at the bottom of the first permanent magnet, capable of fitting against the outer wall of the workpiece to be detected; A first transfer yoke plate, fixedly installed at the top of the first permanent magnet; A first turning yoke plate, one end of which is fixedly installed at the top of the first transfer yoke plate, the other end extends towards the third static magnetic field generating member, and has upper threads provided on its top surface; Each third static magnetic field generating member includes: A second permanent magnet; A second converging yoke plate, fixedly installed at the bottom of the second permanent magnet, capable of fitting against the outer wall of the workpiece to be detected; A second transfer yoke plate, fixedly installed at the top of the second permanent magnet; A heightening yoke plate, fixedly installed at the top of the second transfer yoke plate; A second turning yoke plate, one end of which is fixedly installed at the top of the heightening yoke plate, the other end extends towards the first static magnetic field generating member, and has lower threads provided on its bottom surface; a part of the second turning yoke plate and a part of the first turning yoke plate are connected by the lower threads and the upper threads; The structure of each second static magnetic field generating member is the same as that of each third static magnetic field generating member; the structure of each fourth static magnetic field generating member is the same as that of each first static magnetic field generating member; a part of the second turning armature plate of each second static magnetic field generating member is connected to a part of the first turning armature plate of each fourth static magnetic field generating member through a lower thread and an upper thread.

[0011] In some embodiments, the first circumferential static magnetic field array unit further includes: A first support ring, on the inner wall of which there are formed a first installation groove for installing the first static magnetic field generating member and a second installation groove for installing the second static magnetic field generating member; The second circumferential static magnetic field array unit includes: A second support ring, on the inner wall of which there are formed a third installation groove for installing the third static magnetic field generating member and a fourth installation groove for installing the fourth static magnetic field generating member.

[0012] In some embodiments, a plurality of first support segments are sequentially connected to form the first support ring; A plurality of second support segments are sequentially connected to form the second support ring.

[0013] The beneficial effects of the present invention are as follows: The structure of the magnetostrictive longitudinal wave transducer capable of realizing static magnetic field regulation of the present invention is provided with a first circumferential static magnetic field array unit, a second circumferential static magnetic field array unit and an alternating magnetic field generating unit. The first circumferential static magnetic field array unit is formed on the outer periphery of one end of the workpiece to be detected, and can generate a static magnetic field in the circumferential direction of the workpiece to be detected. The second circumferential static magnetic field array unit is also formed on the outer periphery of one end of the workpiece to be detected, and is disposed opposite to the first circumferential static magnetic field array unit. The second circumferential static magnetic field array unit can also generate a static magnetic field in the circumferential direction of the workpiece to be detected. The second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit can move towards each other to accurately adjust the magnitude of the static bias magnetic field. The second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit can rotate relative to each other to accurately adjust the magnitude of the static bias magnetic field. It not only ensures the stability of the bias magnetic field but also can accurately adjust the magnitude of the bias magnetic field. The alternating magnetic field generating unit is disposed between the second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit and is wound around the outer periphery of one end of the workpiece to be detected, and can generate an alternating bias magnetic field. By using the form of coupling the static bias magnetic field and the alternating bias magnetic field, the grounding rod is excited to generate longitudinal mode guided waves along the axial direction, and then by receiving the longitudinal mode guided waves, the detection of defects on the grounding rod is realized. By changing the intensity of the static bias magnetic field, the magnetostrictive effect is located in the working area near the maximum value of the slope change on the magnetization curve, so as to excite the guided wave signal with the maximum energy and improve the conversion efficiency of electrical energy and mechanical energy of the magnetostrictive effect. Description of the Drawings

[0014] Figure 1It is a schematic structural diagram of some specific embodiments of a magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation according to the present invention; Figure 2 It is Figure 1 The displacement distribution diagram of the cross-section of the workpiece to be detected in the horizontal direction when the magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation shown in the figure works; Figure 3 It is Figure 1 The displacement distribution diagram of the cross-section of the workpiece to be detected in the vertical direction when the magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation shown in the figure works; Figure 4 It is Figure 1 The displacement distribution diagram of the cross-section of the workpiece to be detected in the axial direction when the magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation shown in the figure works; Figure 5 It is a schematic structural diagram of some other specific embodiments of a magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation according to the present invention; Figure 6 It is a schematic structural diagram of some further specific embodiments of a magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation according to the present invention; Figure 7 It is Figure 1 The schematic diagram of the magnetic flux density in the axial direction of the workpiece to be detected when the first circumferential static magnetic field array unit and the second circumferential static magnetic field array unit of the magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation shown in the figure move towards each other; Figure 8 It is Figure 5 The schematic diagram of the magnetic flux density in the axial direction of the workpiece to be detected when the first circumferential static magnetic field array unit and the second circumferential static magnetic field array unit of the magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation shown in the figure move towards each other; Figure 9 It is Figure 5 The schematic diagram of the magnetic flux density in the axial direction of the workpiece to be detected when the first circumferential static magnetic field array unit and the second circumferential static magnetic field array unit of the magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation shown in the figure rotate relative to each other; Figure 10 It is Figure 5 The polar coordinate diagram of the magnetic field distribution at the middle position of the grounding rod section covered by the magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation shown in the figure; Figure 11 It is a schematic structural diagram of some specific embodiments of a defect detection device according to the present invention; Figure 12 It is using Figure 11 The schematic diagram of the echo signal detected by the defect detection device shown in the figure.

[0015] In the accompanying drawings, 100, a magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation; 110, a first circumferential static magnetic field array unit; 111, a first static magnetic field generating element; 1111, a first permanent magnet; 1112, a first converging armature piece; 1113, a first transfer armature piece; 1114, a first steering armature piece; 112, a second static magnetic field generating element; 113, a first supporting ring; 1131, a first supporting section; 1132, a first connecting block; 120, a second circumferential static magnetic field array unit; 121, a third static magnetic field generating element; Magnetic field generating element; 1211, second permanent magnet; 1212, second converging armature piece; 1213, second transfer armature piece; 1214, raising armature piece; 1215, second steering armature piece; 122, fourth static magnetic field generating element; 123, second support ring; 1231, second support section; 1232, second connecting block; 130, alternating magnetic field generating unit; 200, part to be detected; 310, signal generating module; 320, power amplifying module; 330, signal amplifying module; 340, signal processing module. DETAILED DESCRIPTION

[0016] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] As described in the background technology, a bias magnetic field can be provided by using a powered coil. Although the magnitude of the magnetic field can be precisely adjusted according to the actual use scenario, the resulting bias magnetic field is not stable enough and can cause electromagnetic interference to the waveguide receiving signal. A bias magnetic field can also be provided by using a permanent magnet. Although the magnetic field is sufficiently stable, the magnitude of the magnetic field can only be significantly adjusted by increasing or decreasing the number of permanent magnets, and the magnitude of the magnetic field cannot be precisely adjusted. Therefore, how to ensure the stability of the bias magnetic field while precisely adjusting the magnitude of the bias magnetic field has become a technical problem that needs to be solved urgently by those skilled in the art.

[0018] To solve the above problems, refer to Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 and Figure 11, on the one hand, the present invention provides a magnetostrictive longitudinal wave transducer structure 100 capable of realizing static magnetic field regulation, including a first circumferential static magnetic field array unit 110, a second circumferential static magnetic field array unit 120, and an alternating magnetic field generating unit 130. The first circumferential static magnetic field array unit 110 is formed on the outer periphery of one end of the workpiece to be detected 200, and can generate a static magnetic field in the circumferential direction of the workpiece to be detected 200. The second circumferential static magnetic field array unit 120 is also formed on the outer periphery of one end of the workpiece to be detected 200, and is disposed opposite to the first circumferential static magnetic field array unit 110. The second circumferential static magnetic field array unit 120 can also generate a static magnetic field in the circumferential direction of the workpiece to be detected 200. The second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 can move towards each other to precisely adjust the magnitude of the static bias magnetic field. The second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 can rotate relative to each other to precisely adjust the magnitude of the static bias magnetic field. This not only ensures the stability of the bias magnetic field but also enables precise adjustment of the magnitude of the bias magnetic field. The alternating magnetic field generating unit 130 is disposed between the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110, and is wound around the outer periphery of one end of the workpiece to be detected 200, and can generate an alternating bias magnetic field. It should be noted that the workpiece to be detected 200 is a grounding rod or other rod-shaped parts that are not easily accessible. By using the form of coupling the static bias magnetic field and the alternating bias magnetic field, longitudinal mode guided waves are excited along the axial direction of the grounding rod, and then by receiving the longitudinal mode guided waves, defects on the grounding rod can be detected. By changing the intensity of the static bias magnetic field, the magnetostrictive effect is located in the working area near the maximum value of the slope change on the magnetization curve, thereby exciting the guided wave signal with the maximum energy and improving the conversion efficiency of electrical energy and mechanical energy of the magnetostrictive effect.

[0019] Preferably, the alternating magnetic field generating unit 130 is a coil with a certain number of turns.

[0020] Preferably, the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 can move towards each other by 0 - 40 mm. Without changing the specifications of the permanent magnets used in the circumferential static magnetic field array unit, by changing the length of the magnetic circuit, the uniformity of the magnetic field distribution in the grounding rod can be improved, and the intensity of the static bias magnetic field can be increased. Since the alternating magnetic field generating unit 130 is theoretically selected according to the wavelength, the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 that can move towards each other can match the coil specifications at different frequencies without the need for re-magnetic circuit design.

[0021] Preferably, the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 can rotate relative to each other by 0 - 20°. When the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 rotate relative to each other by 0°, the contact area between the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 is the largest, realizing the complete connection of the magnetic circuit, and the static bias magnetic field intensity provided at this time is at the maximum value. When the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 rotate relative to each other by 20°, the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 no longer contact each other, there is an air gap in the magnetic circuit, and the generated magnetic field intensity is at the minimum value.

[0022] In some of its practical applications, such as Figure 1 As shown, the first circumferential static magnetic field array unit 110 only includes a plurality of second static magnetic field generating members 112. The plurality of second static magnetic field generating members 112 are evenly distributed along the circumference of the first circumferential static magnetic field array unit 110. The second circumferential static magnetic field array unit 120 only includes a plurality of fourth static magnetic field generating members 122. The plurality of fourth static magnetic field generating members 122 are evenly distributed along the circumference of the second circumferential static magnetic field array unit 120. A part of the top of each second static magnetic field generating member 112 covers a part of the top of a fourth static magnetic field generating member 122.

[0023] Preferably, the first circumferential static magnetic field array unit 110 includes four second static magnetic field generating members 112. The second circumferential static magnetic field array unit 120 includes four fourth static magnetic field generating members 122.

[0024] Adopt Figure 1 The magnetostrictive longitudinal wave transducer structure 100 capable of realizing static magnetic field regulation shown in the figure is used for simulation experiments by using simulation software. The first step is to apply an excitation signal, input an alternating current to the alternating magnetic field generating unit 130 to generate a dynamic alternating magnetic field, which is coupled with the static magnetic field. Under the action of the magnetostrictive positive effect, magnetostrictive strain is generated inside the grounding rod, and the displacement strain signal is obtained through mechanical field calculation. The second step is to use the obtained displacement strain signal as the input signal and apply it to the grounding rod to cause vibration inside the grounding rod. Under the action of the static magnetic field, according to the magnetostrictive inverse effect, the magnetic field around the grounding rod changes, causing the alternating magnetic field generating unit 130 to generate an induced voltage signal. Post-processing the simulation experiment data, the displacement distribution of the cross-section of the grounding rod in the horizontal direction is as shown in Figure 2 As shown, the displacement distribution of the cross-section of the grounding rod in the vertical direction is as shown in Figure 3 As shown, the displacement distribution of the cross-section of the grounding rod in the axial direction is as shown in Figure 4As shown. Through comparison, it can be concluded that the displacement in the axial direction is the largest, far greater than the displacements in the other two directions, proving that under the combined action of the static bias magnetic field and the dynamic bias magnetic field, the mechanical vibration inside the grounding rod is mainly axial vibration, and the generated is indeed longitudinal mode guided waves, verifying the feasibility of the transducer structure.

[0025] When only considering the influence of the static bias magnetic field and not considering the influence of the dynamic bias magnetic field, the physical field only retains the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120, and no longer retains the alternating magnetic field generating unit 130. When the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120 move towards each other by 10 mm ( Figure 7 the red curve in), 20 mm ( Figure 7 the green curve in), and 30 mm ( Figure 7 the blue curve in), that is, when the screwed connection lengths of the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120 are 10 mm, 20 mm, and 30 mm, the magnetic field distribution on the central axis inside the grounding rod is as shown in Figure 7 As shown. It can be seen from this that with the increase of the screwed connection length, the axial magnetic field intensity is greatly enhanced. However, due to the different magnetic circuit lengths in the radial direction, the magnetic field distribution shows obvious deflection, which will lead to a decrease in the transducer efficiency and affect the stability of the excited guided waves.

[0026] In some other practical applications, as shown in Figure 5 the first circumferential static magnetic field array unit 110 includes a plurality of first static magnetic field generating parts 111 and a plurality of second static magnetic field generating parts 112. The plurality of first static magnetic field generating parts 111 and the plurality of second static magnetic field generating parts 112 are alternately arranged along the circumferential direction of the first circumferential static magnetic field array unit 110. The second circumferential static magnetic field array unit 120 includes a plurality of third static magnetic field generating parts 121 and a plurality of fourth static magnetic field generating parts 122. The plurality of third static magnetic field generating parts 121 and the plurality of fourth static magnetic field generating parts 122 are alternately arranged along the circumferential direction of the second circumferential static magnetic field array unit 120. A part of the top of each third static magnetic field generating part 121 covers a part of the top of a first static magnetic field generating part 111. A part of the top of each second static magnetic field generating part 112 covers a part of the top of a fourth static magnetic field generating part 122.

[0027] Preferably, the first circumferential static magnetic field array unit 110 includes two first static magnetic field generating parts 111 and two second static magnetic field generating parts 112. The second circumferential static magnetic field array unit 120 includes two third static magnetic field generating parts 121 and two fourth static magnetic field generating parts 122.

[0028] When only the influence of the static bias magnetic field is considered without considering the influence of the dynamic bias magnetic field, the physical field only retains the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120, and no longer retains the alternating magnetic field generating unit 130. When the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120 move toward each other by 10 mm ( Figure 8 Medium red curve), 20mm ( Figure 8 medium green curve) and 30mm ( Figure 8 When the screw connection lengths of the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120 are 10 mm, 20 mm, and 30 mm, the magnetic field distribution on the central axis of the grounding rod is as follows: Figure 8 As the screw connection length increases, the axial magnetic field strength is greatly enhanced, and the axial magnetic field strength is evenly distributed, which improves the energy conversion efficiency.

[0029] When the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120 rotate 5° relative to each other ( Figure 9 Medium blue curve), 10° ( Figure 9 Medium green curve), 15° ( Figure 9 The red curve in the middle shows the magnetic field distribution on the central axis of the grounding rod. Figure 9 As shown in Figure 2, the axial magnetic flux density shows a downward trend as the relative rotation angle increases.

[0030] Specifically, in the example, Figure 5As shown, each first static magnetic field generator 111 includes a first permanent magnet 1111, a first converging armature 1112, a first transfer armature 1113, and a first deflection armature 1114. The first converging armature 1112 is fixedly mounted to the bottom of the first permanent magnet 1111 and can be attached to the outer wall of the component to be detected 200, acting as a magnetic conductor. This allows the same first permanent magnet 1111 to be compatible with grounding rods of various diameters, improving the versatility of the magnetostrictive longitudinal wave transducer structure 100 capable of static magnetic field regulation. The first transfer armature 1113 is fixedly mounted to the top of the first permanent magnet 1111. It acts as a magnetic conductor and connects the first permanent magnet 1111 to the first deflection armature 1114. One end of the first deflection armature 1114 is fixedly mounted to the top of the first transfer armature 1113, while the other end extends toward the third static magnetic field generator 121. The top surface of the first deflection armature 1114 is provided with an upper thread, acting as a magnetic conductor. Each third static magnetic field generating element 121 includes a second permanent magnet 1211, a second converging armature piece 1212, a second transfer armature piece 1213, a raised armature piece 1214, and a second steering armature piece 1215. The second converging armature piece 1212 is fixedly mounted on the bottom of the second permanent magnet 1211 and can be attached to the outer wall of the component to be detected 200, playing a magnetic conduction role. This allows the same second permanent magnet 1211 to be applicable to grounding rods of various diameters, thereby improving the versatility of the magnetostrictive longitudinal wave transducer structure 100 capable of achieving static magnetic field regulation. The second transfer armature piece 1213 is fixedly mounted on the top of the second permanent magnet 1211 and plays a magnetic conduction role. The raised armature piece 1214 is fixedly mounted on the top of the second transfer armature piece 1213 so that the second steering armature piece 1215 is higher than the first steering armature piece 1114. One end of the second steering armature piece 1215 is fixedly mounted on the top of the raised armature piece 1214, and the other end extends toward the first static magnetic field generating element 111. A lower thread is provided on the bottom surface. A portion of the second steering armature piece 1215 is connected to a portion of the first steering armature piece 1114 via a lower thread and an upper thread. The structure of each second static magnetic field generating element 112 is the same as that of each third static magnetic field generating element 121. The structure of each fourth static magnetic field generating element 122 is the same as that of each first static magnetic field generating element. A portion of the second steering armature piece 1215 of each second static magnetic field generating element 112 is connected to a portion of the first steering armature piece 1114 of each fourth static magnetic field generating element 122 via a lower thread and an upper thread. The use of a screw connection facilitates both the movement of the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110 toward each other and the relative rotation of the second circumferential static magnetic field array unit 120 and the first circumferential static magnetic field array unit 110.

[0031] Preferably, inside each of the first static magnetic field generating members 111, inside each of the second static magnetic field generating members 112, inside each of the third static magnetic field generating members 121, and inside each of the fourth static magnetic field generating members 122, a welding process is adopted to achieve integral fixation.

[0032] Preferably, the thicknesses of the first steering armature piece 1114 and the second steering armature piece 1215 are less than or equal to 5 mm to avoid magnetic field deviation on the axis of the grounding rod.

[0033] Preferably, the first converging armature piece 1112, the first transfer armature piece 1113, the first steering armature piece 1114, the second converging armature piece 1212, the second transfer armature piece 1213, the elevation armature piece 1214, and the second steering armature piece 1215 are all made of soft magnetic materials. The first permanent magnet 1111 and the second permanent magnet 1211 are neodymium iron boron or other types of permanent magnets.

[0034] Preferably, as Figure 6 shown, the first circumferential static magnetic field array unit 110 further includes a first support ring 113. A first installation groove for installing the first static magnetic field generating member 111 and a second installation groove for installing the second static magnetic field generating member 112 are formed on the inner wall of the first support ring 113. The second circumferential static magnetic field array unit 120 includes a second support ring 123. The first support ring 113 can drive the first static magnetic field generating member 111 and the second static magnetic field generating member 112 to rotate synchronously. A third installation groove for installing the third static magnetic field generating member 121 and a fourth installation groove for installing the fourth static magnetic field generating member 122 are formed on the inner wall of the second support ring 123. The second support ring 123 can drive the third static magnetic field generating member 121 and the fourth static magnetic field generating member 122 to rotate synchronously.

[0035] Preferably, the materials of the first support ring 113 and the second support ring 123 are non-ferromagnetic materials such as aluminum alloy or nylon.

[0036] Preferably, a plurality of first support segments 1131 are sequentially connected to form the first support ring 113. Adjacent two first support segments 1131 are detachably connected by a first connection block 1132 and screws to facilitate the disassembly and assembly of the first support ring 113. A plurality of second support segments 1231 are sequentially connected to form the second support ring 123. Adjacent two second support segments 1231 are detachably connected by a second connection block 1232 and screws to facilitate the disassembly and assembly of the second support ring 123.

[0037] When the first circumferential static magnetic field array unit 110 includes two first static magnetic field generating members 111 and two second static magnetic field generating members 112, and the second circumferential static magnetic field array unit 120 includes two third static magnetic field generating members 121 and two fourth static magnetic field generating members 122, the length of the first steering armature piece 1114 of each first static magnetic field generating member 111 is 80 mm, the length of the second steering armature piece 1215 of each third static magnetic field generating member 121 is 120 mm, and the length of the threaded fit is 60 mm. The axial length of the magnetostrictive longitudinal wave transducer structure 100 capable of realizing static magnetic field regulation is at most 200 mm. Using simulation software for simulation experiments, the diameter of the grounding rod is set to 30 mm, the material of the grounding rod is Q345 steel, and the threaded connection is regarded as the surface contact of the armature. The materials of the first permanent magnet 1111 and the second permanent magnet 1211 are set to N52 neodymium iron boron, the direction of the remanent magnetic flux density is the radial direction, and the magnetic pole directions of the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120 are opposite. Under the parametric scanning of indentations of 10 mm, 20 mm, 30 mm, etc., the corresponding magnetic field distribution is obtained, and Figure 10 the polar coordinate diagram of the magnetic field distribution at the middle position of the grounding rod section covered by the magnetostrictive longitudinal wave transducer structure 100 capable of realizing static magnetic field regulation as shown. It can be seen from Figure 10 that as the axial magnetic circuit length decreases, the axial magnetic field distribution inside the grounding rod becomes more uniform, and the magnetic field intensity is greatly increased, which is very beneficial to the generation of stress waves in the magnetostrictive effect. And in the actual on-site application process, considering the complex situation that one section of the grounding rod is in the air and one section is in the paddy field, in such cases, the magnetostrictive longitudinal wave transducer structure 100 capable of realizing static magnetic field regulation can still better solve the actual problems. In addition, the specifications of the coil used in the alternating magnetic field generating unit 130 are usually selected according to the required wavelength. For example, the wavelength is about 100 mm at a frequency of 50 kHz, and the wavelength is about 140 mm at a frequency of 35 kHz. Therefore, the indentation of the axial magnetic circuit is beneficial to the expansion of the coil frequency, thereby enhancing the detection ability for defects. Through this structure, theoretically, the magnetic field intensity provided by the static magnetic field array can be located within the maximum and minimum threshold values corresponding to 0~20°, greatly improving the energy conversion efficiency of the permanent magnet, and at the same time overcoming the disadvantage that the magnetic field size of the permanent magnet cannot be adjusted in real time.

[0038] Refer to Figure 11, on the other hand, the present invention also provides a defect detection device, which includes a signal generation module 310, a power amplification module 320, a signal amplification module 330, a signal processing module 340, and a magnetostrictive longitudinal wave transducer structure 100 capable of realizing static magnetic field regulation. The magnetostrictive longitudinal wave transducer structure 100 capable of realizing static magnetic field regulation is provided with a signal excitation end and a signal receiving end. The alternating magnetic field generation unit 130 is respectively connected to the signal excitation end and the signal receiving end. The signal excitation end is successively connected to the power amplification module 320 and the signal generation module 310. The signal receiving end is successively connected to the signal amplification module 330 and the signal processing module 340. By rotating the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120, the armature is driven to move towards each other to shorten the length of the magnetic circuit and improve the magnetic field uniformity and intensity. At the same time, by adjusting the magnitude of the axial magnetic field, the magnetostrictive effect is made to be at the optimal working point, breaking through the bottleneck of the non-adjustable static magnetic field intensity. The overall operation is simple, significantly improving the energy conversion efficiency and being applicable to the corrosion detection of grounding rods.

[0039] Since pulse echo is mostly used in on-site applications, the magnetostrictive longitudinal wave transducer structure 100 capable of realizing static magnetic field regulation is placed at the left end of the grounding rod, 0.2 m away from the left end face of the grounding rod. The diameter of the grounding rod specimen is 30 mm and the length is 2 m, and a 2-mm groove is engraved at the 1.2-m position. Figure 5 Or Figure 6 When the magnetostrictive longitudinal wave transducer structure 100 capable of realizing static magnetic field regulation as shown works, a pulse echo is excited at the right end face of the grounding rod to obtain Figure 12 the echo signal diagram as shown. An obvious defect signal appears at about 1 m, and as the first circumferential static magnetic field array unit 110 and the second circumferential static magnetic field array unit 120 rotate and separate, the amplitude of the defect echo signal becomes lower and lower, which is consistent with the simulation results.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 the present invention.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0042] In the present invention, unless otherwise clearly specified and defined, terms such as "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] In the present invention, terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0044] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation, characterized in that Comprising: A first circumferential static magnetic field array unit formed on the outer periphery of the workpiece to be detected; A second circumferential static magnetic field array unit formed on the outer periphery of the workpiece to be detected, disposed opposite to the first circumferential static magnetic field array unit; the second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit can move towards each other; the second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit can rotate relative to each other; An alternating magnetic field generating unit disposed between the second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit and wound around the outer periphery of the workpiece to be detected.

2. The magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation according to claim 1, characterized in that, The second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit can move towards each other by 0 - 40 mm.

3. The magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation according to claim 1, characterized in that, The second circumferential static magnetic field array unit and the first circumferential static magnetic field array unit can rotate relative to each other by 0 - 20°.

4. The magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation according to any one of claims 1 to 3, characterized in that, The first circumferential static magnetic field array unit includes: A plurality of first static magnetic field generating members evenly distributed along the circumference of the first circumferential static magnetic field array unit; A plurality of second static magnetic field generating members alternately arranged with the first static magnetic field generating members along the circumference of the first circumferential static magnetic field array unit; The second circumferential static magnetic field array unit includes: A plurality of third static magnetic field generating members evenly distributed along the circumference of the second circumferential static magnetic field array unit; A plurality of fourth static magnetic field generating members alternately arranged with the third static magnetic field generating members along the circumference of the second circumferential static magnetic field array unit; A part of the top of each third static magnetic field generating member covers a part of the top of a first static magnetic field generating member; a part of the top of each second static magnetic field generating member covers a part of the top of a fourth static magnetic field generating member.

5. The magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation according to claim 4, characterized in that, Each first static magnetic field generating member includes: A first permanent magnet; A first converging armature plate fixedly installed at the bottom of the first permanent magnet and capable of fitting on the outer wall of the workpiece to be detected; A first transfer armature plate fixedly installed at the top of the first permanent magnet; A first turning armature plate, one end of which is fixedly installed at the top of the first transfer armature plate and the other end extends towards the third static magnetic field generating member, and has upper threads provided on its top surface; Each third static magnetic field generating member includes: A second permanent magnet; A second converging armature plate fixedly installed at the bottom of the second permanent magnet and capable of fitting on the outer wall of the workpiece to be detected; A second transfer armature plate fixedly installed at the top of the second permanent magnet; A heightening armature plate fixedly installed at the top of the second transfer armature plate; A second turning armature plate, one end of which is fixedly installed at the top of the heightening armature plate and the other end extends towards the first static magnetic field generating member, and has lower threads provided on its bottom surface; a part of the second turning armature plate is connected to a part of the first turning armature plate through the lower threads and the upper threads; The structure of each of the second static magnetic field generating members is the same as that of each of the third static magnetic field generating members; the structure of each of the fourth static magnetic field generating members is the same as that of each of the first static magnetic field generating members; a part of the second steering armature plate of each of the second static magnetic field generating members is connected to a part of the first steering armature plate of each of the fourth static magnetic field generating members through the lower thread and the upper thread.

6. The magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation according to claim 4, wherein The first circumferential static magnetic field array unit further includes: A first support ring, on the inner wall of which there are formed a first installation groove for installing the first static magnetic field generating member and a second installation groove for installing the second static magnetic field generating member; The second circumferential static magnetic field array unit includes: A second support ring, on the inner wall of which there are formed a third installation groove for installing the third static magnetic field generating member and a fourth installation groove for installing the fourth static magnetic field generating member.

7. The magnetostrictive longitudinal wave transducer structure capable of realizing static magnetic field regulation according to claim 4, characterized in that, A plurality of first support segments are sequentially connected to form the first support ring; A plurality of second support segments are sequentially connected to form the second support ring.

Images