Subwavelength elastic wave spin wave source excitation device and preparation method thereof

Abstract

The application relates to a subwavelength elastic wave spin wave source excitation device and a preparation method thereof. The device comprises a mounting base, a piezoelectric vibration assembly connected and mounted on the mounting base, the piezoelectric vibration assembly comprising a first piezoelectric element and a second piezoelectric element, the first piezoelectric element and the second piezoelectric element being fixed to two adjacent surfaces of the mounting base respectively, the first piezoelectric element and the second piezoelectric element being connected to double-channel excitation voltage signals inputted from outside respectively, and the phase difference or voltage amplitude ratio of the double-channel excitation voltage signals being adjustable. Compared with the prior art, the application can realize adjustable spin source displacement field characteristics, is suitable for spin source excitation of Lamb waves and Rayleigh waves, and has the advantages of small size, simple structure, portability and detachability, convenient preparation, low cost and the like.

Description

Technical Field

[0001] This invention relates to the field of elastic wave excitation technology, and in particular to a subwavelength elastic wave spin source excitation device and its preparation method. Background Technology

[0002] The study of spin has advanced our understanding of fundamental properties such as symmetry and topology from the quantum level to classical systems. Spin has become one of the most important properties in condensed matter physics and quantum mechanics, and is also the foundation of topological states. In classical elastic wave systems, spin not only manifests in direction-selective propagation (unidirectional propagation, backscattering suppression, etc.), but also has outstanding advantages in characterizing displacement fields and describing particle displacement polarization behavior. Although classical elastic wave theory can clearly describe the propagation properties of waves in general elastic media, analyzing the topological properties of waves from the perspective of particle spin can further reveal the intrinsic physical mechanisms of wave propagation, which will greatly promote the development of related application technologies, especially in non-destructive testing, geological exploration, and earthquake prevention.

[0003] Furthermore, the concept of spin has been rapidly extended to classical wave systems based on periodic structures (such as acoustic metamaterials). Due to their flexible and controllable structural characteristics, periodic structures and classical wave systems within them have become excellent platforms for testing or realizing many topological physical phenomena. Numerous researchers have conducted studies on analog Hall effects, spin Hall effects, valley Hall effects, Weyl points, and higher-order topologies in acoustic or mechanical systems. A significant characteristic of topological structures is the unidirectional propagation of waves along the topological boundary composed of two antiphase components. For example, in phononic crystal plates, on topological boundaries based on analog spin Hall effects and valley Hall effects, an elastic wave spin source with a specific polarization direction can selectively excite unidirectional boundary states, and the propagation direction of the boundary states in the topological projection is spin-dependent. However, experimental studies on unidirectional propagation boundary states excited by spin elastic wave sources are currently very rare, especially regarding the spin source excitation of Lamb waves and Rayleigh waves. Existing functional devices and elastic wave source excitation technologies can already achieve excitation through multi-channel phase-controlled plate waves or Rayleigh wave sources. However, the application of wave source excitation devices is limited due to factors such as the complexity of elastic wave experimental technology, the large size of spin source excitation devices, and the single and uncontrollable distribution characteristics of spin source displacement fields. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing a subwavelength elastic wave spin source excitation device and its preparation method, which can achieve adjustable spin source displacement field characteristics and is applicable to spin source excitation of Lamb waves and Rayleigh waves.

[0005] The objective of this invention can be achieved through the following technical solution: a subwavelength elastic wave spin source excitation device, comprising a mounting base, on which a piezoelectric vibration assembly is connected and mounted, the piezoelectric vibration assembly comprising a first piezoelectric element and a second piezoelectric element, the first piezoelectric element and the second piezoelectric element being respectively fixed to two adjacent surfaces of the mounting base, the first piezoelectric element and the second piezoelectric element being respectively connected to an externally input dual-channel excitation voltage signal, the phase difference or voltage amplitude ratio of the dual-channel excitation voltage signal being adjustable.

[0006] Furthermore, the first piezoelectric element and the second piezoelectric element have the same size, material, and polarization direction.

[0007] Furthermore, the first piezoelectric element and the second piezoelectric element are respectively connected to the surface of the mounting base via connecting fasteners, which have insulating properties.

[0008] Furthermore, the dual-channel excitation voltage signal includes a first-channel excitation voltage signal and a second-channel excitation voltage signal, both of which are multi-cycle sinusoidal pulse voltage signals.

[0009] Furthermore, a first positive wire is connected to the surface of the first piezoelectric element away from the mounting base, and a first negative wire is connected to the surface of the first piezoelectric element close to the mounting base. The first positive wire is connected to the positive terminal of the first channel excitation voltage signal, and the first negative wire is connected to the negative terminal of the first channel excitation voltage signal.

[0010] Furthermore, a second positive wire is connected to the surface of the second piezoelectric element away from the mounting base, and a second negative wire is connected to the surface of the second piezoelectric element close to the mounting base. The second positive wire is connected to the positive terminal of the second channel excitation voltage signal, and the second negative wire is connected to the negative terminal of the second channel excitation voltage signal.

[0011] Furthermore, the mounting base is used to fix two adjacent surfaces of the first piezoelectric element and the second piezoelectric element to be perpendicular to each other.

[0012] Furthermore, the first piezoelectric element and the second piezoelectric element are specifically piezoelectric ceramic sheets or piezoelectric electret films, the connecting fastener is specifically epoxy resin, and the mounting base is specifically a metal column or an insulating column.

[0013] A method for fabricating a subwavelength elastic wave spin source excitation device includes the following steps:

[0014] S1. Determine the dimensions of the first piezoelectric element, the second piezoelectric element, and the mounting base based on the required frequency range and wave velocity of the elastic wave spin source.

[0015] S2. Fix two separate double-sided adhesive tapes to the mounting platform, and draw the positions for fixing the first piezoelectric element and the second piezoelectric element on one side of the two double-sided adhesive tapes respectively.

[0016] S3. Fix a wire to the position of the piezoelectric element on each of the two double-sided adhesive tapes;

[0017] S4. Apply a thin layer of epoxy resin to the positions where the piezoelectric element is fixed on the two double-sided adhesive tapes;

[0018] S5. Place the first piezoelectric element and the second piezoelectric element in the predetermined position, and press them to initially fix the two piezoelectric elements flat in the predetermined position.

[0019] S6. Measure whether the wire is connected to the surface of the corresponding piezoelectric element. If yes, proceed to step S7; otherwise, return to step S3 until the wire is connected to the surface of the corresponding piezoelectric element.

[0020] S7. After the two piezoelectric elements are initially fixed to their respective wires, but before the epoxy resin is fully cured, remove the double-sided tape.

[0021] S8. Fix two separate double-sided adhesive tapes on the mounting table again, apply a thin layer of epoxy resin to each, and then fix the two piezoelectric elements, along with the wires, into the epoxy resin and press them in place.

[0022] S9. Measure again whether the wire is connected to the surface of the corresponding piezoelectric element. If yes, let it cure for 2 to 3 hours. Otherwise, return to step S3.

[0023] S10. Clean off the double-sided tape and check whether the wires of the two components are insulated from the bottom of the components after curing. If they are not insulated, repeat step S9. Add a layer of epoxy resin under the components. If they are insulated, proceed to step S11.

[0024] S11. The two structures containing piezoelectric elements formed in the above steps are fixed to two adjacent surfaces of the mounting base with epoxy resin, and wires are welded to the surfaces of the two piezoelectric elements away from the mounting base to form the whole excitation device.

[0025] The wires connecting the two piezoelectric elements are connected to the external dual-channel excitation voltage signal.

[0026] Furthermore, in step S1, wavelength data is calculated based on the frequency range and wave velocity required by the elastic wave spin source. Then, the dimensions of the first piezoelectric element, the second piezoelectric element, and the mounting base are designed to be less than one-quarter of the wavelength, where wavelength = wave velocity ÷ frequency.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] I. This invention relates to a piezoelectric vibration assembly mounted on a mounting base. The assembly includes a first piezoelectric element and a second piezoelectric element, which are respectively fixed to two adjacent surfaces of the mounting base. Both the first and second piezoelectric elements are connected to an externally input dual-channel excitation voltage signal, the phase difference or voltage amplitude ratio of which is adjustable. When the first and second piezoelectric elements receive the externally input excitation voltage signal, they convert the voltage signal into mechanical vibration, which is then transmitted to the structural surface through the mounting base, thereby exciting an elastic wave spin source. This can be used for related experiments and practical applications of spin Lamb waves and Rayleigh waves. Furthermore, by adjusting the externally input dual-channel excitation voltage information, the displacement field distribution characteristics of the spin source can be adjusted and controlled accordingly.

[0029] Second, in this invention, negative and positive wires are connected to the surfaces of the two piezoelectric elements near the mounting base and the surfaces away from the mounting base, respectively, so as to be connected to the positive and negative poles of the excitation voltage signal, so that the external voltage signal can be accurately transmitted to the piezoelectric element, ensuring the accuracy of the elastic wave spin source excitation.

[0030] Third, based on the frequency range and wave velocity required by the elastic wave spin source, this invention determines the dimensions of the two piezoelectric elements and the mounting base, ensuring that the mounting base can accommodate the piezoelectric elements and that the overall size is less than a quarter of the wavelength, thereby miniaturizing the overall structure of the device.

[0031] Fourth, the present invention uses a manufacturing method that involves multiple applications of double-sided adhesive tape during the preparation of the device, which reduces the difficulty of manufacturing and ensures the precision of the processing. Attached Figure Description

[0032] Figure 1 This is a schematic diagram showing the disassembly of the device structure of the present invention;

[0033] Figure 2 This is a front view of the device structure of the present invention;

[0034] Figure 3 This is a schematic diagram of the overall structure of the device of the present invention;

[0035] Figures 4a-4c This is a schematic diagram of the dual-channel excitation voltage signal in the embodiment;

[0036] Figure 5 This is a diagram showing the experimental results of using Lamb waves to excite on a thin aluminum plate in the examples;

[0037] Figure 6 This is a diagram showing the experimental results of Rayleigh wave excitation on a thin aluminum plate in the examples;

[0038] The markings in the diagram are as follows: 1. First piezoelectric element; 2. Second piezoelectric element; 3. Connecting fastener; 4. Mounting base; 5. First positive electrode wire; 6. First negative electrode wire; 7. Second positive electrode wire; 8. Second negative electrode wire. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0040] Example

[0041] like Figures 1-3 As shown, a subwavelength elastic wave spin source excitation device includes a piezoelectric vibration assembly and a mounting base 4. The piezoelectric vibration assembly includes a first piezoelectric element 1 and a second piezoelectric element 2 adjacent to two surfaces of the mounting base 4. The first piezoelectric element 1 and the second piezoelectric element 2 are respectively connected to two adjacent surfaces of the mounting base 4 through connecting fasteners 3. The mounting base 4 is used to fix the elastic wave spin source excitation device to form an integral whole. The first piezoelectric element 1 and the second piezoelectric element 2 respectively receive externally input dual-channel excitation voltage signals (including channel 1 and channel 2, with a certain phase difference or voltage amplitude ratio between the two channels relative to the center frequency), and correspondingly convert the voltage signals into mechanical vibrations, which are then transmitted to the structural surface through the connecting fasteners 3 and the mounting base 4 to complete the excitation of the elastic wave spin source.

[0042] In practical applications, both the first piezoelectric element 1 and the second piezoelectric element 2 are piezoelectric ceramic sheets or piezoelectric electret films. The two piezoelectric elements are identical in size, material, and polarization direction. They can be various shapes such as discs, rings, or square sheets. The parameters of the piezoelectric elements need to be set according to actual usage requirements, including the size (designed based on the required frequency of the elastic wave spin source) and shape. In this embodiment, both piezoelectric elements are cylindrical piezoelectric ceramics with a diameter of 5 mm, a thickness of 1.2 mm, and made of PZT-5H material, with the polarization direction along the thickness direction. The operating frequency of the elastic wave spin source excitation device composed of piezoelectric elements of this size can cover at least the range of 10 to 80 kHz.

[0043] The connecting fastener 3 is made of epoxy resin. The epoxy resin connecting fastener has high connection strength, which can effectively fix the piezoelectric element to the mounting base 4 and ensure the insulation between the surface of the piezoelectric element and the mounting base 4.

[0044] Mounting base 4 is made of metal or insulating material and is used to fix the subwavelength elastic wave spin source excitation device into an integral device. Mounting base 4 has two mutually perpendicular surfaces for fixing two piezoelectric elements 1 and 2 respectively. Mounting base 4 can be hexahedral or other geometric shapes and has multiple mounting methods.

[0045] Furthermore, the surface of the first piezoelectric element 1 furthest from the mounting base 4 is connected to the first positive wire 5, and the surface of the first piezoelectric element 1 closest to the mounting base 4 is connected to the first negative wire 6; the surface of the second piezoelectric element 2 furthest from the mounting base 4 is connected to the second positive wire 7, and the surface of the second piezoelectric element 2 closest to the mounting base 4 is connected to the second negative wire 8; the first piezoelectric element 1 uses the excitation voltage signal of channel 1, with the surface of the first piezoelectric element 1 furthest from the mounting base 4 connected to the positive terminal of the excitation voltage signal of channel 1, and the surface of the first piezoelectric element 1 closest to the mounting base 4 connected to the negative terminal of the excitation voltage signal of channel 1; the second piezoelectric element 2 uses the excitation voltage signal of channel 2, with the surface of the second piezoelectric element 2 furthest from the mounting base 4 connected to the positive terminal of the excitation voltage signal of channel 2, and the surface of the second piezoelectric element 2 closest to the mounting base 4 connected to the negative terminal of the excitation voltage signal of channel 2.

[0046] In this embodiment, both channel 1 and channel 2 of the excitation voltage signal use multi-cycle sinusoidal pulse voltage signals. In this embodiment, the sinusoidal pulse excitation voltage signals of channel 1 and channel 2 are as follows: Figures 4a-4c As shown, the center frequency is 20 kHz. There is a phase difference of π / 2 or an amplitude ratio of 1 / 2 between channel 1 and channel 2 relative to the center frequency of 20 kHz, or there are both a phase difference of π / 2 and an amplitude ratio of 1 / 2 between channel 1 and channel 2 relative to the center frequency of 20 kHz.

[0047] Figure 5 The experimental results of the spin source device in the embodiment for Lamb waves at an excitation signal center frequency of 20 kHz demonstrate the direction-selective propagation characteristics of spin elastic waves under excitation conditions. Obviously, the spin elastic wave mainly propagates to the left. Figure 6 The experimental results of using the spin source device in this embodiment for Rayleigh waves at an excitation signal center frequency of 20 kHz show that the spin elastic wave propagates primarily to the left. This demonstrates that this technical solution can excite Lamb waves and Rayleigh waves with spin characteristics.

[0048] This embodiment also provides a method for preparing the above-mentioned device, including:

[0049] (1) Select the dimensions of two piezoelectric elements 1 and 2 according to the frequency range and wave velocity required by the elastic wave spin source;

[0050] (2) Determine the dimensions of the mounting base 4 based on the dimensions of piezoelectric elements 1 and 2;

[0051] (3) Fix two separate double-sided adhesive tapes to the mounting table (desktop or workbench, etc.), and draw the corresponding positions for fixing piezoelectric elements 1 and 2 on one side of the double-sided adhesive tapes according to the determined dimensions;

[0052] (4) Fix a wire to the position of the piezoelectric element on each of the two double-sided adhesive tapes;

[0053] (5) Apply a thin layer of epoxy resin to the positions where the piezoelectric element is fixed on the two double-sided adhesive tapes;

[0054] (6) Place piezoelectric elements 1 and 2 in the predetermined positions and press them down to initially fix the two piezoelectric elements flat in the predetermined positions;

[0055] (7) Measure whether the wire is connected to the corresponding piezoelectric element surface. If it is not properly connected, check and return to steps (4) to (6) to make the wire connected to the corresponding piezoelectric element surface.

[0056] (8) When the two piezoelectric elements are initially fixed to their respective wires, but the epoxy resin has not been fully cured, remove the double-sided tape;

[0057] (9) Fix two separate double-sided adhesive tapes on the mounting table again, apply a thin layer of epoxy resin to each, and then fix the two piezoelectric elements that were initially fixed together with the wires into the epoxy resin and press them in place.

[0058] (10) Check again and perform step (7). If each wire is in good contact with the corresponding piezoelectric element, let it cure for 2 to 3 hours.

[0059] (11) Clean off the double-sided tape, check the two piezoelectric components after curing, and check whether the wires are insulated from the bottom of the piezoelectric components. If there is no insulation, repeat step (10) and add a layer of epoxy resin under the components; if there is insulation, proceed to the next step.

[0060] (12) The two structures containing piezoelectric elements formed in the above steps are fixed to two adjacent surfaces of a metal pillar or an insulating pillar with epoxy resin, and wires are welded to the surfaces of the two piezoelectric pieces away from the base to form the whole excitation device.

[0061] Through the above preparation process, a small device with a simple structure, detachable and portable design can be realized, which has a wider range of applications.

[0062] In practical applications, the first positive wire 5 is connected to the surface of the first piezoelectric element 1 away from the mounting base 4, and the first negative wire 6 is connected to the surface of the first piezoelectric element 1 close to the mounting base 4; the second positive wire 7 is connected to the surface of the second piezoelectric element 2 away from the mounting base 4, and the second negative wire 8 is connected to the surface of the second piezoelectric element 2 close to the mounting base 4.

[0063] The first piezoelectric element 1 uses the excitation voltage signal of channel 1. The surface of the first piezoelectric element 1 away from the mounting base 4 is connected to the positive terminal of the excitation voltage signal, and the surface close to the mounting base 4 is connected to the negative terminal. The second piezoelectric element 2 uses the excitation voltage signal of channel 2. The surface of the second piezoelectric element 2 away from the mounting base 4 is connected to the positive terminal, and the surface close to the mounting base 4 is connected to the negative terminal. Both channels 1 and 2 of the excitation voltage signal use multi-cycle sinusoidal pulse voltage signals. There is a certain phase difference or voltage amplitude ratio between the two channels relative to the center frequency. By adjusting the signal amplitude ratio of the two channels, the displacement field distribution characteristics of the elastic wave spin source can be controlled.

[0064] In summary, this technical solution proposes a subwavelength elastic wave spin source excitation device and its preparation method with adjustable spin source displacement field distribution characteristics, applicable to both Lamb waves and Rayleigh waves. It can provide key evidence for experimental research such as spin-dependent unidirectional transmission, and provide an experimental basis for the design and development of related miniaturized devices.

Claims

1. A method for preparing a subwavelength elastic wave spin source excitation device, characterized in that, The elastic wave spin wave source excitation device includes a mounting base (4), on which a piezoelectric vibration assembly is connected and mounted. The piezoelectric vibration assembly includes a first piezoelectric element (1) and a second piezoelectric element (2). The first piezoelectric element (1) and the second piezoelectric element (2) are respectively fixed to two adjacent surfaces of the mounting base (4). The first piezoelectric element (1) and the second piezoelectric element (2) are respectively connected to an externally input dual-channel excitation voltage signal. The phase difference or voltage amplitude ratio of the dual-channel excitation voltage signal is adjustable. The preparation method includes the following steps: S1. Based on the frequency range and wave velocity required by the elastic wave spin source, determine the dimensions of the first piezoelectric element, the second piezoelectric element, and the mounting base. Specifically, based on the frequency range and wave velocity required by the elastic wave spin source, calculate the wavelength data, and then design the dimensions of the first piezoelectric element, the second piezoelectric element, and the mounting base to be less than one-quarter of the wavelength, where wavelength = wave velocity ÷ frequency. S2. Fix two separate double-sided adhesive tapes to the mounting platform, and draw the positions for fixing the first piezoelectric element and the second piezoelectric element on one side of the two double-sided adhesive tapes respectively. S3. Fix a wire to the position of the piezoelectric element on each of the two double-sided adhesive tapes; S4. Apply a thin layer of epoxy resin to the positions where the piezoelectric element is fixed on the two double-sided adhesive tapes; S5. Place the first piezoelectric element and the second piezoelectric element in the predetermined position, and press them to initially fix the two piezoelectric elements flat in the predetermined position. S6. Measure whether the wire is connected to the surface of the corresponding piezoelectric element. If yes, proceed to step S7; otherwise, return to step S3 until the wire is connected to the surface of the corresponding piezoelectric element. S7. After the two piezoelectric elements are initially fixed to their respective wires, but before the epoxy resin is fully cured, remove the double-sided tape. S8. Fix two separate double-sided adhesive tapes on the mounting table again, apply a thin layer of epoxy resin to each, and then fix the two piezoelectric elements, along with the wires, into the epoxy resin and press them in place. S9. Measure again whether the wire is connected to the surface of the corresponding piezoelectric element. If yes, let it cure for 2 to 3 hours. Otherwise, return to step S3. S10. Clean off the double-sided tape and check whether the wires of the two components are insulated from the bottom of the components after curing. If they are not insulated, repeat step S9. Add a layer of epoxy resin under the components. If they are insulated, proceed to step S11. S11. The two structures containing piezoelectric elements formed in the above steps are fixed to two adjacent surfaces of the mounting base with epoxy resin, and wires are welded to the surfaces of the two piezoelectric elements away from the mounting base to form the whole excitation device. The wires connecting the two piezoelectric elements are connected to the external dual-channel excitation voltage signal.

2. The method for preparing a subwavelength elastic wave spin source excitation device according to claim 1, characterized in that, The first piezoelectric element (1) and the second piezoelectric element (2) have the same size, material and polarization direction.

3. The method for preparing a subwavelength elastic wave spin source excitation device according to claim 1, characterized in that, The first piezoelectric element (1) and the second piezoelectric element (2) are respectively connected to the surface of the mounting base (4) through a connecting fastener (3), and the connecting fastener (3) has insulating properties.

4. The method for preparing a subwavelength elastic wave spin source excitation device according to claim 1, characterized in that, The dual-channel excitation voltage signal includes a first-channel excitation voltage signal and a second-channel excitation voltage signal, both of which are multi-cycle sinusoidal pulse voltage signals.

5. The method for preparing a subwavelength elastic wave spin source excitation device according to claim 4, characterized in that, The surface of the first piezoelectric element (1) away from the mounting base (4) is connected to a first positive wire (5), and the surface of the first piezoelectric element (1) close to the mounting base (4) is connected to a first negative wire (6). The first positive wire (5) is connected to the positive terminal of the first channel excitation voltage signal, and the first negative wire (6) is connected to the negative terminal of the first channel excitation voltage signal.

6. The method for preparing a subwavelength elastic wave spin source excitation device according to claim 4, characterized in that, The second piezoelectric element (2) has a second positive wire (7) connected to the surface away from the mounting base (4), and a second negative wire (8) connected to the surface of the second piezoelectric element (2) close to the mounting base (4). The second positive wire (7) is connected to the positive terminal of the second channel excitation voltage signal, and the second negative wire (8) is connected to the negative terminal of the second channel excitation voltage signal.

7. The method for preparing a subwavelength elastic wave spin source excitation device according to claim 1, characterized in that, The mounting base (4) is used to fix two adjacent surfaces of the first piezoelectric element (1) and the second piezoelectric element (2) perpendicular to each other.

8. The method for preparing a subwavelength elastic wave spin source excitation device according to claim 3, characterized in that, The first piezoelectric element (1) and the second piezoelectric element (2) are specifically piezoelectric ceramic sheets or piezoelectric electret films, the connecting fastener (3) is specifically epoxy resin, and the mounting base (4) is specifically a metal column or an insulating column.

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