A T(0,1) mode wave source excitation device for a rod and its preparation method

Abstract

This invention relates to a T(0,1) mode wave source excitation device and its preparation method for a rod, comprising an annular mounting base, a vibration assembly, and a piezoelectric assembly. The inner wall of the annular mounting base is in contact with the outer wall of the rod under test. The vibration assembly includes multiple cubic blocks distributed on the outer side of the annular mounting base, which are connected to the annular mounting base via vibration connecting fasteners. The piezoelectric assembly includes multiple piezoelectric plates, which are respectively disposed on one side of the cubic blocks and connected to the cubic blocks via piezoelectric connecting fasteners. The multiple piezoelectric plates are respectively connected to an externally input excitation voltage signal, which is converted into mechanical vibration and conducted sequentially through the piezoelectric connecting fasteners, the vibration assembly, and the annular mounting base to the surface of the rod under test, thereby exciting the rod-guided wave T(0,1) mode of the rod under test. This invention generates pure T(0,1) mode rod-guided waves in rods, which can be used for related experiments and practical applications of pure T(0,1) mode rod-guided waves.

Description

Technical Field

[0001] This invention relates to the field of functional devices and elastic wave source generating devices, specifically to a T(0,1) mode wave source excitation device for a rod and its preparation method. Background Technology

[0002] As an important component of some mechanical and building structures, the rod is an essential load-bearing part. After being subjected to fatigue damage or corrosion damage, tiny defects will appear on the surface and inside of the rod. These defects will gradually expand under load, eventually leading to the failure of the rod.

[0003] To prevent such problems, we need to conduct safety inspections throughout the entire life cycle of structural members to ensure the overall reliability of mechanical and building structures. Laser ultrasonic technology, as a defect detection method, not only has the advantages of low cost and simple process, but also does not cause any damage to the inspected structure, making it a primary method for detecting defects in structural members.

[0004] However, due to the boundary conditions of the rod and the reflection and superposition of ultrasonic waves within it, the guided waves in the rod undergo dispersion, resulting in the ultrasonic waves transmitted into the rod being decomposed into three independent modes: longitudinal wave mode (L mode), bending wave mode (F mode), and torsional wave mode (T mode). These separated modes cause the ultrasonic signals to generate superimposed and extremely complex reflection signals when detecting defects within the rod, making it difficult to further analyze the characteristics of the defects. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a T(0,1) mode wave source excitation device for rods and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a T(0,1) mode wave source excitation device for a rod, comprising an annular mounting base, a vibration assembly, and a piezoelectric assembly;

[0007] The inner wall of the annular mounting base fits against the outer wall of the rod being measured;

[0008] The vibration assembly includes at least two cubic blocks evenly spaced on the outside of the annular mounting base, and the cubic blocks are connected to the annular mounting base by a vibration connection fastener.

[0009] The piezoelectric assembly includes multiple piezoelectric sheets, which are respectively disposed on one side of the cube. The cube and the piezoelectric sheets are connected by piezoelectric connectors.

[0010] Multiple piezoelectric elements are connected to externally input excitation voltage signals, which are converted into mechanical vibrations. These vibrations are then transmitted sequentially through piezoelectric connecting fasteners, vibration components, and annular mounting bases to the surface of the rod under test, thereby exciting the rod-guided wave T(0,1) mode of the rod under test.

[0011] Preferably, the device also includes a plurality of first connecting wires and second connecting wires, wherein the first connecting wires are connected to the upper surface of each piezoelectric element and the second connecting wires are connected to the lower surface of each piezoelectric element.

[0012] Preferably, multiple piezoelectric elements are arranged at equal intervals on the same side of the corresponding cube along the circumferential direction of the annular mounting base. The same side means that the tangential direction of the annular mounting base on which the side is located is parallel to the normal direction of the side.

[0013] Preferably, the piezoelectric components share a common excitation voltage signal and are connected to the positive and negative terminals of the excitation voltage signal via a first connecting wire and a second connecting wire, respectively. The positive terminals of multiple piezoelectric elements are connected in series, and the negative terminals of multiple piezoelectric elements are connected in series.

[0014] Preferably, both the vibration connection fastener and the piezoelectric connection fastener are epoxy resin components.

[0015] Preferably, multiple piezoelectric elements have the same size, material, and polarization direction.

[0016] Preferably, the excitation voltage signal is a multi-cycle sinusoidal pulse voltage signal.

[0017] A method for fabricating a T(0,1) mode wave source excitation device for a rod, comprising the above-mentioned T(0,1) mode wave source excitation device for the rod, comprising the following steps:

[0018] S1. Determine the length L and circumferential dimension of the rod to be measured. The length L and circumferential dimension of the rod to be measured can be directly measured. Based on the size range m of the target defect in the rod to be measured, where the size range m refers to the length of the crack in the rod to be measured, determine the required frequency range f, f≥2c / m, where c is the wave velocity of the T(0,1) mode rod guide wave in the rod to be measured.

[0019] S2. Select the geometry of the annular mounting base according to the cross-sectional shape of the rod being measured, and determine the circumferential dimension l of the annular mounting base;

[0020] S3. Determine the side length q of the cube according to step S2, q = l / 3π;

[0021] S4. Determine the number of cubes n according to step S3, where 2≤n≤l / q;

[0022] S5. Based on step S4, determine the number of piezoelectric elements as e, n = e;

[0023] S6. Determine the diameter p of the piezoelectric sheet based on the side length q of the cube, where q / 2 ≤ p ≤ q;

[0024] S7. Determine the distance s between two adjacent cubic blocks based on the circumferential dimension l of the ring mounting base and the number of cubic blocks n, s = l / n;

[0025] S8. Based on the dimensions determined in S7, mark the position of each cubic block on the annular mounting base;

[0026] S9. Apply epoxy resin to the ring mounting base according to the position determined in S8, and fix the cubes on the ring mounting base in sequence. Let it stand for two to three hours to make it completely fixed.

[0027] S10. Take multiple first connecting wires and weld one end of each first connecting wire to the lower surface of the corresponding piezoelectric sheet.

[0028] S11. Take multiple second connecting wires and weld one end of each second connecting wire to the upper surface of the corresponding piezoelectric sheet.

[0029] S12. Check whether the first connecting wire, the second connecting wire and the corresponding connected surface are conductive. If they are not conductive, adjust steps S9-S11 until each wire is conductive to its respective connected surface.

[0030] S13. Adhere the lower surface of the piezoelectric sheet to the side of the corresponding cube;

[0031] S14. Connect the free end of the wires connected to the upper surface of each piezoelectric element to the positive / negative terminal of the external excitation signal, and connect the free end of the wires connected to the lower surface of each piezoelectric element to the negative / positive terminal of the external excitation signal.

[0032] As a preferred embodiment, a method for preparing a T(0,1) mode wave source excitation device for a rod involves applying epoxy resin to the side of each cube, sequentially bonding and fixing the lower surface of the corresponding piezoelectric sheet to the center of the side of the cube, and allowing it to stand for two to three hours to fully fix it.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1) By connecting the piezoelectric array to the voltage signal according to the wiring method described in this invention, and passing through the piezoelectric connection fixing component, the vibration array, the vibration connection fixing component and the ring mounting base, a pure T(0,1) mode rod wave is finally generated in the rod, which can be used for related experiments and practical applications of pure T(0,1) mode rod waves;

[0035] 2) The piezoelectric elements in the piezoelectric assembly have the same structure, and the cubic elements in the vibration assembly have the same structure, which reduces the manufacturing difficulty;

[0036] 3) In this invention, only one channel is needed to control multiple piezoelectric elements in the piezoelectric component, making the operation very simple;

[0037] 4) This invention can excite pure T(0,1) mode rod waves over a wide frequency range;

[0038] 5) This invention is applicable to rod structures with cross-sectional forms such as circular cross-section rods, elliptical cross-section rods, and rectangular cross-section rods, and has a very wide range of applications;

[0039] 6) The T(0,1) mode wave source excitation device for rods designed in this invention can be pre-packaged to make it a detachable and portable device. Moreover, the materials used in this invention can all be obtained through customization or purchase, and the structure is simple and easy to prepare. Attached Figure Description

[0040] Appendix Figure 1 This is a three-dimensional structural diagram of the present invention;

[0041] Appendix Figure 2 This is a front view of the present invention;

[0042] Appendix Figure 3 Appendix to this invention Figure 1 Enlarged structural diagram at point A in the middle;

[0043] Appendix Figure 4 Appendix to this invention Figure 2 Enlarged structural diagram at point B;

[0044] Appendix Figure 5 This is a schematic diagram of the single-channel sinusoidal pulse excitation voltage signal of the present invention;

[0045] Appendix Figure 6 This is a diagram showing the effect of the rod-guided wave T(0,1) mode generated by the present invention when excited on a solid aluminum rod;

[0046] Appendix Figure 7 This is a time-domain signal diagram of the T(0,1) mode rod guide wave excited in the aluminum rod according to an embodiment of the present invention;

[0047] Appendix Figure 8 This is a frequency domain signal diagram of the T(0,1) mode rod guided wave excited by the aluminum rod in an embodiment of the present invention.

[0048] The following are the reference numerals in the attached diagram: 1. Annular mounting base; 2. Vibration connection fastener; 3. Piezoelectric connection fastener; 4. Vibration assembly; 401. Cube I; 402. Cube II; 403. Cube III; 404. Cube IV; 5. Piezoelectric assembly; 501. Piezoelectric sheet I; 502. Piezoelectric sheet II; 503. Piezoelectric sheet III; 504. Piezoelectric sheet IV; 6. First connecting wire; 7. Second connecting wire. Detailed Implementation

[0049] The invention will be further described below with reference to specific embodiments, such as... Figure 1-8 As shown, a T(0,1) mode wave source excitation device for a rod includes an annular mounting base 1, a vibration component 4, a piezoelectric component 5, a first connecting wire 6, and a second connecting wire 7.

[0050] Based on the torsional polarization characteristics of the displacement field of T(0,1) mode rod-guided waves, this invention designs a T(0,1) mode wave source excitation device and its fabrication method for rods. This invention not only provides single-mode excitation for non-destructive testing of rods, but also provides experimental support for the study of rod-guided wave propagation dependent on the T(0,1) mode.

[0051] In this embodiment, the inner wall of the annular mounting base 1 is adapted to and fits against the outer wall of the rod being measured. The annular mounting base 1 is a closed annular solid metal, used to fix the overall device and transmit mechanical vibration. Depending on the cross-sectional shape of the rod being measured, the annular mounting base 1 can be a circular ring, an elliptical ring, a rectangular ring, a square ring, an L-shaped ring, a T-shaped ring, an I-shaped ring, etc.

[0052] The vibration assembly 4 in this embodiment includes four cubic blocks evenly spaced on the outside of the annular mounting base 1, namely cubic block I 401, cubic block II 402, cubic block III 403, and cubic block IV 404. The cubic blocks are connected to the annular mounting base 1 by vibration connection fasteners 2. The cubic blocks are made of aluminum, and the four solid metal cubic blocks are arranged at equal intervals along the circumference of the annular mounting base 1. The vibration connection fasteners 2 are made of epoxy resin, which has high connection strength and is used both to fix the vibration assembly and the annular mounting base 1 to form a whole and to transmit the mechanical vibration generated by the vibration assembly to the annular mounting base 1.

[0053] The piezoelectric assembly 5 includes four piezoelectric plates corresponding to the cube: piezoelectric plate I 501, piezoelectric plate II 502, piezoelectric plate III 503, and piezoelectric plate IV 504. All four piezoelectric plates are identical in size, material, and polarization direction. The piezoelectric connecting fastener 3 is made of epoxy resin, which provides high connection strength. It serves to fix the piezoelectric assembly 5 and the vibration assembly 4 together, ensures insulation between the lower surface of the piezoelectric plates and the vibration assembly 4, and transmits the mechanical vibration generated by the piezoelectric assembly 5 to the vibration assembly 4. The cube and the piezoelectric plates are connected by the piezoelectric connecting fastener 3. In this embodiment, the four piezoelectric plates are evenly spaced along the circumferential direction of the annular mounting base 1 on the same side of the corresponding cube. If the four piezoelectric plates are not on the same side, a pure T(0,1) mode rod waveguide cannot be excited.

[0054] The number and material of the piezoelectric elements and cubes are selected according to the actual situation.

[0055] In this embodiment, the rod length L of the tested rod is selected as 3000 mm, the cross-section is selected as circular, the circumference of the circular cross-section is selected as 78.5 mm, the side length of each cubic block is 6 mm, the piezoelectric sheet is selected as cylindrical piezoelectric ceramic with a diameter of 5 mm and a thickness of 1 mm, and the material is PZT-5H, with the polarization direction along the thickness direction. The working frequency of the T(0,1) mode rod waveguide source excitation device composed of piezoelectric sheets and arrays of this size can cover at least the range of 10 to 70 kHz. In this example, the circumferential spacing between adjacent piezoelectric cubic blocks is 19.625 mm.

[0056] Four piezoelectric elements are respectively connected to externally input excitation voltage signals, which are converted into mechanical vibrations. These vibrations are then transmitted to the surface of the rod under test through the piezoelectric connection fixing part 3, the vibration component 4, and the annular mounting base 1, in order to excite the rod guided wave T(0,1) mode of the rod under test.

[0057] The first connecting wire 6 is connected to the upper surface of each piezoelectric element, and the second connecting wire 7 is connected to the lower surface of each piezoelectric element. The piezoelectric assembly 5 shares a common excitation voltage signal channel. The upper surface of piezoelectric element 501 is connected to the positive terminal of the excitation voltage signal, and the lower surface is connected to the negative terminal. The upper surface of piezoelectric element 502 is connected to the negative terminal, and the lower surface of piezoelectric element 503 is connected to the negative terminal, and the lower surface of piezoelectric element 504 is connected to the negative terminal, and the lower surface of piezoelectric element 504 is connected to the positive terminal. In this embodiment, the positive terminals of the four piezoelectric elements are connected in series, and the negative terminals of the four piezoelectric elements are connected in series.

[0058] A method for fabricating a T(0,1) mode wave source excitation device for a rod, comprising the following steps:

[0059] S1. Based on the length L, circumferential dimension and target defect size m of the rod being tested, the length L and circumferential dimension of the rod being tested can be directly measured; based on the size range m of the target defect in the rod, determine the required frequency range f, f≥2c / m, where c is the wave velocity of the T(0,1) mode rod guide wave in the rod being tested, and the wave velocity value is 3072m / s;

[0060] In this example, the size range of the target defect is as follows: the crack length is approximately 13 cm; the selected frequency band is 50 kHz; the size of the target defect refers to the length of the crack, and the exact size of the target defect is an unknown factor. The size range of the target defect is obtained by observation, direct measurement or numerical calculation, and then the accurate defect size is detected by this T(0,1) mode wave source excitation device.

[0061] The length of the rod to be measured is 3000 mm, and the cross-section is circular. The circumference of the circular cross-section is directly measured based on the actual rod, and the circumference of the circular cross-section is 78.5 mm.

[0062] S2. Based on the cross-sectional shape of the rod being measured, the geometry of the annular mounting base 1 is selected as circular, and the circumferential dimension l of the annular mounting base 1 is determined to be 78.5 mm.

[0063] S3. Based on the circumferential dimension l of the ring mounting base 1, determine the side length q of the cube, l / 8π≤q≤l / 3π (l is the circumferential dimension), and select the cube size as 6 mm;

[0064] S4. Based on the circumferential dimension l of the ring mounting base 1 and the side length q of the cube, determine the number n of the cubes, where 2≤n≤l / q, and four cubes are selected.

[0065] S5. Based on the side length q of the cube, determine the diameter p of the piezoelectric sheet. q / 2≤p≤q, so there are four piezoelectric sheets. The diameter of the piezoelectric sheet is 5 mm, the thickness is 1 mm, and the material is PZT-5H cylindrical piezoelectric ceramic disc.

[0066] S6. Determine the distance s between two adjacent cubic blocks based on the circumferential dimension l of the annular mounting base 1 and the number of cubic blocks n. The distance between two adjacent cubic blocks is 19.625 mm.

[0067] S7. Based on the dimensions determined in S4 and S6, mark the position of each cube on the annular mounting base 1 with a marker.

[0068] S8. Apply epoxy resin to the ring mounting base 1 according to the position determined in S7, and fix the cubes on the ring mounting base 1 in sequence. Let it stand for two to three hours to make it completely fixed.

[0069] S9. In this embodiment, four first connecting wires 6 are taken, and one end of each first connecting wire 6 is welded to the lower surface of the corresponding piezoelectric sheet.

[0070] S10. In this embodiment, four second connecting wires 7 are taken, and one end of each second connecting wire 7 is welded to the upper surface of the corresponding piezoelectric sheet.

[0071] S11. Check whether the first connecting wire 6 and the second connecting wire 7 are connected to the corresponding surfaces. If they are not connected, adjust steps S8-S10 until each wire is connected to its respective surface.

[0072] S12. Apply epoxy resin to the side of each cube, and then smoothly bond and fix the lower surface of the corresponding piezoelectric sheet to the center of the side of the cube. Let it stand for two to three hours to allow it to fully fix.

[0073] S13. Connect the free end of the wires connected to the upper surface of each piezoelectric element to the positive (or negative) terminal of the external excitation signal, and connect the free end of the wires connected to the lower surface of each piezoelectric element to the negative (or positive) terminal of the external excitation signal.

[0074] Figure 5 This is a schematic diagram of a single-channel sinusoidal pulse excitation voltage signal with a center frequency of 50 kHz.

[0075] Figure 6 The diagram shows the effect of the device in this embodiment, illustrating the calculation results of an example when the center frequency of the excitation signal is 50 kHz, and the displacement in the direction of the vertical rod is antisymmetric.

[0076] Figure 7 This is a time-domain signal diagram of the device in this embodiment that generates a T(0,1) mode rod guided wave in a 3-meter-long aluminum rod.

[0077] Figure 8 The image shows the frequency domain signal of the T(0,1) mode rod guided wave excited in a 3-meter-long aluminum rod by the device in this embodiment. It can be seen that under the excitation of this T(0,1) mode wave source excitation device suitable for rods, pure T(0,1) mode rod guided waves are generated in the rod.

[0078] It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

Claims

1. A type of rod T (0,1) modal wave source excitation device, characterized in that: It includes an annular mounting base (1), a vibration assembly (4), and a piezoelectric assembly (5); The inner wall of the annular mounting base (1) is in contact with the outer wall of the rod being tested; The vibration assembly (4) includes at least two cubic blocks that are equally spaced on the outside of the annular mounting base (1), and the cubic blocks are connected to the annular mounting base (1) by a vibration connection fastener (2). The piezoelectric assembly (5) includes multiple piezoelectric sheets, which are respectively disposed on one side of the cube, and the cube and the piezoelectric sheets are connected by a piezoelectric connecting fastener (3); Multiple piezoelectric elements are respectively connected to externally input excitation voltage signals, which are converted into mechanical vibrations. These vibrations are then transmitted sequentially through the piezoelectric connecting fastener (3), the vibration assembly (4), the vibration connecting fastener (2), and the annular mounting base (1) to the surface of the rod under test, thereby completing the rod waveguide of the rod under test. T Excitation of (0,1) modes; It also includes multiple first connecting wires (6) and second connecting wires (7), the first connecting wires (6) being connected to the upper surface of each piezoelectric element, and the second connecting wires (7) being connected to the lower surface of each piezoelectric element; Multiple piezoelectric elements are arranged at equal intervals along the circumferential direction of the annular mounting base (1) on the same side of the corresponding cube. The same side means that the tangential direction of the annular mounting base on which the side is located is parallel to the normal direction of the side.

2. A rod according to claim 1 T (0,1) modal wave source excitation device, characterized in that: The piezoelectric component (5) shares an excitation voltage signal through a single channel and is connected to the positive and negative terminals of the excitation voltage signal via a first connecting wire (6) and a second connecting wire (7), respectively. The positive terminals of the multiple piezoelectric elements are connected in series, and the negative terminals of the multiple piezoelectric elements are connected in series.

3. A rod according to claim 1 T (0,1) modal wave source excitation device, characterized in that: Both the vibration connection fastener (2) and the piezoelectric connection fastener (3) are epoxy resin components.

4. A rod according to claim 1 T (0,1) modal wave source excitation device, characterized in that: The multiple piezoelectric elements are identical in size, material, and polarization direction.

5. A rod according to claim 2 T (0,1) modal wave source excitation device, characterized in that: The excitation voltage signal is a multi-cycle sinusoidal pulse voltage signal.

6. A type of rod T A method for preparing a (0,1) modal wave source excitation device, comprising a rod as described in any one of claims 1-5. T (0,1) modal wave source excitation device, characterized in that: Includes the following steps, S1. Determine the length of the rod being measured. L Circumferential dimension, length of the rod being measured L The circumferential dimension can be directly measured based on the size range of the target defect in the rod being measured. m Size range m The length of the crack in the rod being measured ， Determine the required frequency band f , f ≥2 c / m ,in c For the rod being measured T (0,1) mode rod wave velocity; S2. Select the geometry of the annular mounting base (1) according to the cross-sectional shape of the rod being measured, and determine the circumferential dimension of the annular mounting base (1). l ; S3. Determine the side length of the cube according to step S2. q , q = l / 3π; S4. Determine the number of cubes based on step S3. n ,2≤ n ≤ l / q ; S5. Determine the number of piezoelectric elements according to step S4. e , n=e ; S6. Based on the side length of the cube q Determine the diameter of the piezoelectric element. p , q / 2≤ p ≤ q ; S7. According to the circumferential dimension of the annular mounting base (1) l And the number of cubes n， Determine the distance between two adjacent cubes s , s = l / n ; S8. Mark the position of each cube on the annular mounting base (1) according to the dimensions determined in step S7; S9. Apply epoxy resin to the annular mounting base (1) according to the position determined in step S8, and fix the cube on the annular mounting base (1) in sequence. Let it stand for two to three hours to make it completely fixed. S10. Take multiple first connecting wires (6) and weld one end of each first connecting wire (6) to the lower surface of the corresponding piezoelectric sheet. S11. Take multiple second connecting wires (7) and weld one end of each second connecting wire (7) to the upper surface of the corresponding piezoelectric sheet. S12. Check whether the first connecting wire (6), the second connecting wire (7) and the corresponding connected surface are conductive. If they are not conductive, adjust steps S9-S11 until each wire is conductive to its respective connected surface. S13. Adhere the lower surface of the piezoelectric sheet to the side of the corresponding cube; S14. Connect the free end of the wire connected to the upper surface of each piezoelectric element to the positive / negative pole of the external excitation signal, and connect the free end of the wire connected to the lower surface of each piezoelectric element to the negative / positive pole of the external excitation signal.

7. A rod according to claim 6 T The method for preparing a (0,1) modal wave source excitation device is characterized by: Apply epoxy resin to the side of each cube, and then smoothly bond and fix the lower surface of the corresponding piezoelectric sheet to the center of the side of the cube. Let it stand for two to three hours to allow it to fully fix.

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