Piezoelectric Composite Transducer with Adjustable Guided Wave Excitation Modes and Its Working Method

Abstract

The present invention belongs to the technical field of transducers, and provides a piezoelectric composite transducer with adjustable guided wave excitation mode and its working method. A plurality of piezoelectric composite array elements are multiple plate-like structures distributed in parallel. The piezoelectric composite array elements arranged in a line are used to replace the traditional interdigital and comb-shaped piezoelectric transducers. By unplugging and plugging wires, the connection terminals on part of the double-row female headers can be selectively connected to the corresponding independent female headers, so as to adjust the distribution of the excited piezoelectric composite array elements, achieve the purpose of flexibly controlling the wavelength of the guided wave excitation mode, and can excite a single guided wave mode with different wavelengths under the condition of not changing the geometric structure of the transducer, solving the problem that the traditional transducer cannot realize the adjustment of a single guided wave excitation mode.

Description

Technical Field

[0001] The present invention belongs to the technical field of transducers, and particularly relates to a piezoelectric composite transducer with adjustable guided wave excitation mode and its working method. Background Art

[0002] The ultrasonic guided wave detection technology is a non-destructive detection technology based on the stress wave propagation theory in bounded structures. It has the advantages of long detection distance, high detection accuracy and low cost, and is widely used in the flaw detection of engineering equipment. However, the complex multi-modal characteristics of guided waves greatly limit its detection effect. The so-called multi-modal characteristics mean that at any excitation frequency, there are at least two modes of ultrasonic guided waves in the structure to be detected, which not only increases the difficulty of processing the received signals, but also reduces the transducer efficiency of the key modes. Therefore, selecting a single and appropriate guided wave mode for excitation can improve the sensitivity to defects and reduce the influence of multi-modal characteristics, which has great engineering significance for ultrasonic guided wave detection technology.

[0003] The inventors found that among the piezoelectric transducers developed at the present stage that can achieve single guided wave mode excitation, one is to design the structural dimensions of the comb-shaped electrodes to achieve the excitation of specific guided wave modes in plates or pipes; the other is an improvement based on the traditional interdigital piezoelectric transducer, using discrete distributed electrode strips to replace the traditional interdigital electrodes with fixed spacing. Without changing the electrode structure, different single guided wave modes with different wavelengths can be selectively excited through the connection configuration between discrete electrodes. However, the piezoelectric transducers developed at the present stage can only excite a single guided wave mode at certain specific frequencies, and cannot arbitrarily control the guided wave excitation mode in a wide frequency range. The detection flexibility is poor, the efficiency is low, and it cannot meet the engineering detection requirements. Summary of the Invention

[0004] In order to solve the above problems, the present invention proposes a piezoelectric composite transducer with adjustable guided wave excitation mode and its working method. Using linearly arranged piezoelectric composite array elements to replace the traditional interdigital electrodes and the entire piezoelectric ceramic transducer plate effectively reduces the weaknesses of traditional piezoelectric ceramics in terms of strength and brittleness, increases the longitudinal electromechanical conversion efficiency, and greatly expands the working bandwidth of the piezoelectric transducer; by controlling the delay of the input signal and adjusting the distribution of the excited piezoelectric array elements in combination with circuit connection, arbitrary control of a single guided wave excitation mode in a wide frequency range can be achieved without changing the geometric structure of the transducer, effectively eliminating the influence of guided wave multi-modal characteristics, and realizing high-efficiency defect detection. It has great engineering application value and potential in the fields of guided wave non-destructive detection and structural health monitoring.

[0005] In a first aspect, the present invention provides a piezoelectric composite transducer with adjustable guided wave excitation modes, comprising a composite piezoelectric array layer and a connector;

[0006] The composite piezoelectric array layer includes a plurality of piezoelectric composite array elements. The plurality of piezoelectric composite array elements are a plurality of plate-like structures distributed in parallel, and decoupling materials are filled between every two adjacent piezoelectric composite array elements; electrodes are provided on each piezoelectric composite array element.

[0007] On the body of the connector, there are provided a plurality of independent female headers for introducing circuit delay signals, and a double-row female header including a plurality of connection terminals; one end of each connection terminal is connected to an electrode on a piezoelectric composite array element through a wire, and the other end is connected to the independent female header through a pluggable wire; by selectively connecting the connection terminals on some of the double-row female headers to the corresponding independent female headers through the pluggable wires, the distribution of the excited piezoelectric composite array elements is adjusted, and the distribution of the excited piezoelectric elements is controlled through circuit connection, and an additional circuit delay signal is introduced to realize the regulation and excitation of a single target guided wave mode and suppress the interference mode.

[0008] Further, a piezoelectric ceramic plate is selected as the piezoelectric phase and polarized along the thickness direction, and a 1-3 type piezoelectric composite material is obtained by cutting and filling the piezoelectric ceramic plate with epoxy resin; the 1-3 type piezoelectric composite material is cut into piezoelectric composite array elements with the same external dimensions and structures.

[0009] Further, the composite piezoelectric array layer is provided with a housing; a backing layer is provided between one side of the composite piezoelectric array layer and the inner wall of the housing, and a matching layer is provided between the other side and the inner wall of the housing.

[0010] Further, both sides of the composite piezoelectric array layer are adhered to the backing layer and the matching layer respectively through epoxy resin glue.

[0011] Further, the backing layer is a mixture including epoxy resin glue, metal oxide and polymer epoxy air spheres; the matching layer is a mixture including epoxy resin glue and metal oxide.

[0012] Further, the decoupling material is a mixture including epoxy resin glue and polymer epoxy air spheres.

[0013] Further, each piezoelectric composite array element has the same external dimensions and structures.

[0014] Further, the plurality of piezoelectric composite array elements are arranged at equal intervals along a straight line.

[0015] Further, each independent female header is respectively connected with a clamping piece; the clamping piece is connected with an external excitation signal source for introducing a circuit delay signal.

[0016] In a second aspect, the present invention further provides a working method for a piezoelectric composite transducer with adjustable guided-wave excitation mode, which adopts the piezoelectric composite transducer with adjustable guided-wave excitation mode as described in the first aspect, including: selectively connecting some connection terminals on the double-row female header to the corresponding independent female header by unplugging and plugging wires, adjusting the distribution of the piezoelectric composite array elements, so as to control the wavelength of the guided-wave excitation mode.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. In the present invention, multiple piezoelectric composite array elements are multiple plate-like structures distributed in parallel. The piezoelectric composite array elements arranged in a line replace the traditional interdigital and comb-shaped piezoelectric transducers. By unplugging and plugging wires, some connection terminals on the double-row female header can be selectively connected to the corresponding independent female header, realizing the adjustment of the distribution of the excited piezoelectric composite array elements, achieving the purpose of flexibly controlling the wavelength of the guided-wave excitation mode. Without changing the geometric structure of the transducer, a single guided-wave mode with different wavelengths can be excited. At the same time, through the additional delay circuit signal introduced by the connector, arbitrary regulation of a single guided-wave excitation mode can be realized within a wide frequency range, solving the problems that the piezoelectric transducers in the prior art can only excite a single guided-wave mode at certain specific frequencies, with poor excitation flexibility and low detection efficiency.

[0019] 2. The present invention uses 1-3 type piezoelectric composite materials polarized in thickness to fabricate the piezoelectric composite array elements. Compared with traditional piezoelectric ceramics, the working bandwidth of the transducer is effectively broadened, and the longitudinal electromechanical coupling efficiency of the piezoelectric composite transducer is improved;

[0020] 3. The present invention fills a high-attenuation decoupling material between the piezoelectric composite array elements. The high-attenuation decoupling material made of epoxy resin glue and polymer epoxy air spheres effectively reduces the deficiency of the transducer in terms of strength brittleness on the one hand, and reduces the transverse coupling vibration between the piezoelectric composite array elements on the other hand, enhancing the sensitivity and signal-to-noise ratio of the excited guided-wave signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings forming a part of this embodiment are used to provide a further understanding of this embodiment. The schematic embodiments and descriptions thereof of this embodiment are used to explain this embodiment and do not constitute an improper limitation to this embodiment.

[0022] Figure 1 It is a schematic structural diagram of Embodiment 1 of the present invention;

[0023] Figure 2 It is a schematic overall structural diagram of the composite piezoelectric array layer of Embodiment 1 of the present invention;

[0024] Figure 3Schematic diagram of the partial structure of the composite piezoelectric array layer in Embodiment 1 of the present invention;

[0025] Figure 4 Schematic diagram of the structure of the piezoelectric composite element in Embodiment 1 of the present invention;

[0026] Figure 5 Schematic diagram of the structure of the connector in Embodiment 1 of the present invention;

[0027] Figure 6 Schematic diagram of the experimental system in Embodiments 2 and 3 of the present invention;

[0028] Figure 7 Test result diagram of the frequency response characteristics in Embodiment 2 of the present invention;

[0029] Figure 8 Ultrasonic guided wave phase velocity dispersion curve of the 4mm thick 6061-T6 aluminum plate in Embodiment 3 of the present invention;

[0030] Figure 9 Schematic diagram of the experimental system of the traditional comb-shaped piezoelectric transducer in Embodiment 3 of the present invention;

[0031] Figure 10 Explanation diagram of the single guided wave mode that can be excited by the traditional comb-shaped piezoelectric transducer in the range of 150 - 1000kHz when the fixed finger spacing in Embodiment 3 of the present invention is 12mm;

[0032] Figure 11 Schematic diagram of the circuit connection of the composite piezoelectric array layer in Embodiment 3 of the present invention, where every 10 piezoelectric composite elements are connected to a channel signal source, and a 200ns linear delay is applied to adjacent channel signal sources;

[0033] Figure 12 Explanation diagram of the single guided wave mode that can be excited by the piezoelectric composite transducer in the range of 150 - 1000kHz under the 200ns linear delay in Embodiment 3 of the present invention;

[0034] Figure 13 Schematic diagram of the circuit connection of the composite piezoelectric array layer in Embodiment 3 of the present invention, where every 5 piezoelectric composite elements are connected to a channel signal source, and a 100ns linear delay is applied to adjacent channel signal sources;

[0035] Figure 14 Explanation diagram of the single guided wave mode that can be excited by the piezoelectric composite transducer in the range of 150 - 1000kHz under the 100ns linear delay in Embodiment 3 of the present invention;

[0036] Among them, 1. Outer shell; 2. Backing layer; 3. Composite piezoelectric array layer; 301. Piezoelectric composite element; 302. Decoupling material; 303. Electrode; 4. Electrode lead; 5. Matching layer; 6. Connector; 601. Clamping piece; 602. Independent row header; 603. Double-row row header; 7. Plug-and-play wire; 8. Cable; 9. 6061-T6 aluminum plate; 10. Signal generator; 11. Amplifier; 12. Piezoelectric composite transducer; 13. Comb-shaped piezoelectric transducer; 14. Piezoelectric ceramic sensor; 15. Oscilloscope. Detailed implementation mode

[0037] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0038] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0039] Embodiment 1:

[0040] At present, the developed piezoelectric transducers can only excite a single guided wave mode at certain specific frequencies, and cannot arbitrarily control the guided wave excitation mode within a wide frequency range. The detection flexibility is poor and the efficiency is low, which cannot meet the engineering detection requirements for regular non-destructive testing of related facilities; in view of the above problems, as Figure 1 shown, the present invention provides a piezoelectric composite transducer with adjustable guided wave excitation mode, including an outer shell 1, a backing layer 2, a composite piezoelectric array layer 3, an electrode lead 4, a matching layer 5, a connector 6, a multi-in-one connecting wire 7 and a cable 8; wherein, the composite piezoelectric array layer 3 includes a piezoelectric composite element 301, a decoupling material 302 and an electrode 303. It can be understood that the electrode 303 can be divided into a positive electrode and a negative electrode. The 6 connectors include a clamping piece 601, an independent row header 602 and a double-row row header 603, and a plurality of connection terminals are arranged on the double-row row header 603.

[0041] Specifically, as Figure 2 , Figure 3 , Figure 4 and Figure 5As shown, the composite piezoelectric array layer 3 includes a plurality of piezoelectric composite array elements 301. The plurality of piezoelectric composite array elements 301 are a plurality of plate-like structures distributed in parallel, and a decoupling material 302 is filled between every two adjacent piezoelectric composite array elements 301; an electrode 303 is provided on each piezoelectric composite array element 301; a plurality of independent female headers 602 and a double-row female header 603 including a plurality of connection terminals are provided on the body of the connector 6; one end of each connection terminal is connected to an electrode lead 4 of an electrode on the piezoelectric composite array element 301 through a wire, and the other end is connected to an independent female header 602 through a pluggable wire 7; it can be understood that the pluggable wire 7 is realized by a conventional connectable and disconnectable connecting wire at any time, and the pluggable wire 7 can achieve the purpose of connecting the same independent female header 602 to a plurality of connection terminals at the same time, and the wire connecting the electrode lead 4 is realized by a cable 8. The plurality of piezoelectric composite array elements 301 are a plurality of plate-like structures distributed in parallel. The piezoelectric composite array elements 301 arranged in a line replace the traditional interdigital and comb-shaped piezoelectric transducers. By the pluggable wire, the connection terminals on part of the double-row female header 603 can be selectively connected to the corresponding independent female headers 602, so as to adjust the distribution of the excited piezoelectric composite array elements 301, achieve the purpose of flexibly controlling the wavelength of the guided wave excitation mode, and can excite a single guided wave mode with different wavelengths under the condition of not changing the geometric structure of the transducer, solving the problem that the traditional transducer cannot realize the adjustment of the single guided wave excitation mode.

[0042] Optionally, the housing 1 is a metal housing filled with epoxy resin glue to ensure insulation between the metal housing and the internal circuit; the backing layer 2 is located at one end of the internal structure of the entire piezoelectric composite transducer, and the matching layer 5 is located at the other end of the entire piezoelectric composite transducer; both side surfaces of the composite piezoelectric array layer 3 are tightly bonded to the backing layer 2 and the matching layer 5 through epoxy resin glue respectively. The electrodes 303 at both ends of each piezoelectric composite array element 301 are respectively connected to the electrode leads 4; each clamping piece 601 is connected to an independent female header 602. Specifically, through a plurality of pluggable wires 7, part of the connection terminals on the double-row female header 603 can be selectively connected to the independent female headers 602, so as to adjust the distribution of the excited piezoelectric composite array elements 301, and achieve the purpose of flexibly controlling the wavelength of the guided wave excitation mode; finally, an external excitation signal source can introduce a circuit delay signal through the clamping piece 601, realizing arbitrary regulation of the single guided wave excitation mode of the piezoelectric composite transducer in a wide frequency range.

[0043] The size of the composite piezoelectric array layer 3 described can be set to a length l 2 = 25, a width w 2 = 60 and a thickness h 2= 2.8 mm. Specifically, it may include 100 piezoelectric composite array elements 301 arranged at equal intervals, decoupling material 302, and electrodes 303. Among them, the arrangement pitch of the piezoelectric composite array elements 301 on the matching layer can be set to s = 0.2.

[0044] Optionally, the backing layer 2 is set to include a mixture made of epoxy resin glue, metal oxide, and polymer epoxy air spheres, which can broaden the working frequency bandwidth of the piezoelectric composite transducer. The length and width of the backing layer 2 are the same as those of the composite piezoelectric array layer 3, and the thickness can be set to h 1 = 30. Among them, the metal oxide can increase the acoustic impedance of the backing layer 2, the epoxy resin glue can play a bonding role, and the polymer epoxy air spheres can increase the acoustic attenuation rate of the backing layer 2. It can be understood that the polymer epoxy air spheres are hollow or solid spheres processed from polymer epoxy resin. The matching layer 5 is set to include a compound made of epoxy resin glue and metal oxide, which can prevent wear and at the same time improve the acoustic wave energy conversion efficiency of the piezoelectric composite transducer. The length and width of the matching layer 5 are the same as those of the composite piezoelectric array layer, and the thickness can be set to h 3 = 2.75.

[0045] Optionally, PZT-5A piezoelectric ceramic is selected as the piezoelectric phase and polarized along the thickness direction. The PZT-5A piezoelectric ceramic plate and epoxy resin can obtain 1-3 type piezoelectric composite materials through the cutting and filling method. The 1-3 type piezoelectric composite materials are cut into piezoelectric composite array elements 301 with completely the same external dimensions and structures by using a numerical control machine tool. All the piezoelectric composite array elements 301 have good consistency in terms of resonance frequency and piezoelectric constant, etc. The dimensions can be set as length l 4 = 25, width w 4 = 0.4 mm, thickness h 4 = 2.8 mm. The piezoelectric composite array elements 301 are made of 1-3 type piezoelectric composite materials with thickness polarization, which improves the longitudinal electromechanical coupling efficiency of the piezoelectric composite transducer and expands the working bandwidth compared with traditional piezoelectric ceramics. Electrodes 303 are prepared on the two end surfaces of the piezoelectric composite array elements 301 by using an ion sputtering instrument. The electrodes 303 can select metal materials with high conductivity and easy welding such as gold, silver, copper, or platinum.

[0046] Optionally, multiple piezoelectric composite array elements 301 are arranged at equal intervals along a straight line on the matching layer 5. The decoupling material 302 is a high-attenuation decoupling material, which can be made of a mixture of epoxy resin glue and polymer epoxy air spheres. The decoupling material 302 is filled in the intervals between adjacent piezoelectric composite array elements 301 to reduce the signal crosstalk caused by vibration between the piezoelectric composite array elements 301.

[0047] The circuit connection of the connector 6 can be controlled by using a plurality of plug-and-play wires 7, so as to adjust the distribution pitch of the piezoelectric composite material elements 301, achieving the effect of controlling the guided wave excitation mode; wherein the equal interval dimension L of the piezoelectric composite material elements 301 is equal to the wavelength λ of the guided wave excitation mode.

[0048] Optionally, an external multi-channel signal source is connected to the clamping piece 601, and a circuit signal with a linear delay can be additionally applied to the piezoelectric composite material elements 301, that is, each channel is delayed by a time Combined with the circuit connection control of the connector 6, the single guided wave excitation mode with any wavelength can be flexibly controlled within a wide frequency range.

[0049] Embodiment 2:

[0050] In order to test the performance of the piezoelectric composite transducer with adjustable guided wave excitation mode in Embodiment 1, this embodiment provides a test system including a piezoelectric composite transducer with adjustable guided wave excitation mode, realizing the test of the frequency response characteristics of the piezoelectric composite transducer, specifically:

[0051] Optionally, the detection object is a 6061-T6 aluminum plate with a specification of 1000mm×1000mm×4mm. The piezoelectric composite transducer is used to excite and control a single guided wave mode in the 6061-T6 aluminum plate in the frequency range of 150-1000 kHz. As Figure 6 shown, the test system includes a 6061-T6 aluminum plate 9, a signal generator 10, an amplifier 11, a piezoelectric composite transducer 12, a piezoelectric ceramic sensor 14, and an oscilloscope 15; wherein, the signal generator 10 can be set as a multi-channel signal generator, and the amplifier assembly 11 can be set as a multi-channel high-voltage amplifier. The multi-channel signal generator can output a sine pulse signal modulated by a Hanning window as a signal source, which can reduce the spectral side lobes of the excitation signal, make the frequency of the excited guided wave signal closer to being single, and the energy more concentrated; the multi-channel high-voltage amplifier can increase the voltage amplitude of the signal source, improve the energy of the excited guided wave signal and the sensitivity to defects; the piezoelectric ceramic sensor 14 is used to receive the guided wave signal propagating in the aluminum plate; the oscilloscope 15 is used to export the waveform information of the received signal for post-processing.

[0052] A frequency sweep experiment was conducted on the piezoelectric composite transducer 12 in Example 1; optionally, the piezoelectric composite transducer 12 was used as an excitation transducer, and it was 300 mm away from the left end face of the 6061-T6 aluminum plate 9. The piezoelectric composite transducer 12 and the piezoelectric ceramic sensor 14 were arranged horizontally with a spacing of 200 mm, and the piezoelectric ceramic sensor was 500 mm away from the right end face of the 6061-T6 aluminum plate. The excitation signal source could be a ten-cycle sine pulse wave modulated by a Hanning window. The starting frequency of the frequency sweep experiment could be 115 kHz, increasing in steps of 10 kHz to 1075 kHz. An excitation-and-reception experiment method was adopted, and the received signal amplitude was normalized. The frequency response characteristics of the piezoelectric composite transducer 12 were as Figure 7 shown. It can be found that the actual center frequency of the piezoelectric composite transducer 12 was 540 kHz, and the relative bandwidth reached 72.55%. This shows that the 1-3 type piezoelectric composite material used in this embodiment had good frequency response characteristics in the wide frequency range of 150 - 1000 kHz, overcame the problem of the narrow working bandwidth of traditional piezoelectric ceramic transducers, increased the longitudinal electromechanical conversion efficiency of the transducer, and simultaneously verified the rationality of the design of the piezoelectric composite transducer 12.

[0053] Example 3:

[0054] In order to further test the performance of the piezoelectric composite transducer with adjustable guided wave excitation mode in Example 1, this embodiment provides a test system including a piezoelectric composite transducer with adjustable guided wave excitation mode. Through comparative experiments, the frequency response characteristics of the piezoelectric composite transducer were tested. Specifically:

[0055] Optionally, the detection object was the 6061-T6 aluminum plate 9 with a specification of 1000 mm × 1000 mm × 4 mm. Figure 8 As shown, it was the ultrasonic guided wave phase velocity dispersion curve of the 4-mm-thick 6061-T6 aluminum plate; the test system was as Figure 6 and Figure 9As shown in the figure, it includes a 6061-T6 aluminum plate 9, a signal generator 10, an amplifier 11, a piezoelectric composite transducer 12, a comb-shaped piezoelectric transducer 13, a piezoelectric ceramic sensor 14, and an oscilloscope 15. Among them, the signal generator 10 can be set as a multi-channel signal generator, and the amplifier 11 can be set as a multi-channel high-voltage amplifier. The multi-channel signal generator can output a sine pulse signal modulated by a Hanning window as a signal source, which can reduce the spectral side lobes of the excitation signal, make the frequency of the excited guided wave signal closer to being single, and the energy more concentrated. The multi-channel high-voltage amplifier can increase the voltage amplitude of the signal source, improve the energy of the excited guided wave signal and the sensitivity to defects. The piezoelectric ceramic sensor 14 is used to receive the guided wave signal propagating in the aluminum plate. The oscilloscope 15 is used to export the waveform information of the received signal for post-processing.

[0056] In order to verify the feasibility of the piezoelectric composite transducer 12 for regulating the single guided wave excitation mode, a modal test experiment was designed in comparison with the traditional piezoelectric comb-shaped piezoelectric transducer. Among them, the excitation transducer is 300 mm away from the left end face of the 6061-T6 aluminum plate 9. The excitation transducer and the piezoelectric ceramic sensor 14 are horizontally arranged with a spacing of 200 mm. The piezoelectric ceramic sensor 14 is 500 mm away from the right end face of the 6061-T6 aluminum plate 9. In the experiment, the excitation signal source can be a ten-cycle sine pulse wave modulated by a Hanning window, and the one-shot-one-receive experimental method is adopted.

[0057] First, a comb-shaped piezoelectric transducer 13 with an interdigital spacing of 12 mm was designed and used as the excitation transducer. The frequency of the excited signal increased from 150 kHz in steps of 20 kHz to 1000 kHz. The piezoelectric ceramic sensor 14 was used to receive the direct signal. After separate processing, it was found that the traditional fixed-spacing comb-shaped piezoelectric transducer only has a good excitation response to a single guided wave mode with a fixed wavelength, that is Figure 10 the guided wave mode points Mode1, Mode2, Mode3, and Mode4 that intersect with the dotted line in the figure.

[0058] If the piezoelectric composite transducer 12 is used as the excitation transducer, the plug-and-play wire 7 is adopted, and part of the piezoelectric composite array 301 is connected to the excitation signal source through the connector 6. For example, every 10 piezoelectric composite array elements 301 are connected to a signal source of one channel. On this basis, a fixed 200 ns linear delay is applied to the signal sources of adjacent channels, that is, each channel is delayed by Specifically as Figure 11 shown; the frequency of the excited signal increases from 150 kHz in steps of 20 kHz to 1000 kHz. The piezoelectric ceramic sensor 14 is used to receive the direct signal, as Figure 12As shown, after separate processing, it is found that at this time, all single guided wave mode points Mode5, Mode6, Mode7, and Mode8 intersecting the dashed line can be excited.

[0059] If the piezoelectric composite transducer is used as the excitation transducer, the plug-and-play wire 7 is adopted, and some piezoelectric composite array elements 301 are connected to the excitation signal source through the connector 6. For example, every 5 piezoelectric composite array elements 301 are connected to the signal source of one channel. On this basis, a fixed 100 ns linear delay is applied to the signal sources of adjacent channels, that is, each channel is delayed by Specifically, as Figure 13 shown; the excitation signal frequency increases from 150 kHz in steps of 20 kHz to 1000 kHz, and the direct wave signal is received by the piezoelectric ceramic sensor 14, as Figure 14 shown. After separate processing, it is found that at this time, all single guided wave mode points, Mode9, Mode10, and Mode11 intersecting the dashed line can be excited.

[0060] It is thus found that if different magnitudes of linear delays are applied and then combined with the circuit configuration of the connector 6, single guided wave modes with different wavelengths can be flexibly excited in the range of 150 - 1000 kHz.

[0061] In summary, by using the linearly arranged piezoelectric composite array elements 301 to replace the traditional electrodes and the entire piezoelectric transducer plate, through delay control of the input signal and adjustment of the circuit connection to change the distribution of the excited piezoelectric array elements, it is possible to efficiently regulate and excite a single target guided wave mode without changing the geometric structure of the transducer, achieving the effect of suppressing the multi-modal characteristics of guided waves.

[0062] Example 4:

[0063] This example provides a working method for a piezoelectric composite transducer with adjustable guided wave excitation mode, which adopts the piezoelectric composite transducer with adjustable guided wave excitation mode described in Example 1, including: selectively connecting some connection terminals on the double-row female header 603 to the corresponding independent female header 602 through the plug-and-play wire 7 to adjust the distribution of the piezoelectric composite array elements 301, thereby controlling the wavelength of the guided wave excitation mode.

[0064] The above is only the preferred embodiment of this example and is not used to limit this example. For those skilled in the art, this example can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this example shall be included in the protection scope of this example.

Claims

1. A piezoelectric composite transducer with adjustable guided wave excitation mode, characterized in that, it includes a composite piezoelectric array layer and a connector; the composite piezoelectric array layer includes a plurality of piezoelectric composite array elements, the plurality of piezoelectric composite array elements are a plurality of plate-like structures distributed in parallel, and decoupling materials are filled between every two adjacent piezoelectric composite array elements; electrodes are arranged on each piezoelectric composite array element; select a piezoelectric ceramic plate as the piezoelectric phase, polarize it along the thickness direction, and obtain a 1-3 type piezoelectric composite material by the cutting and filling method with the piezoelectric ceramic plate and epoxy resin; cut the 1-3 type piezoelectric composite material into piezoelectric composite array elements with the same outer shape and structure; the plurality of piezoelectric composite array elements are arranged at equal intervals along the width direction of the piezoelectric composite array element; a plurality of independent female headers for introducing circuit delay signals and a double-row female header including a plurality of connection terminals are arranged on the body of the connector; one end of each connection terminal is connected to an electrode on a piezoelectric composite array element through a wire, and the other end is connected to the independent female header through a pluggable wire; by selectively connecting the connection terminals on some double-row female headers to the corresponding independent female headers through pluggable wires, the distribution of the excited piezoelectric composite array elements is adjusted, the distribution of the excited piezoelectric array elements is controlled through circuit connection, and an additional circuit delay signal is introduced to realize the regulation and excitation of a single target guided wave mode and suppress the interference mode; the composite piezoelectric array layer is provided with a housing; a backing layer is arranged between one side of the composite piezoelectric array layer and the inner wall of the housing, and a matching layer is arranged between the other side and the inner wall of the housing; the backing layer is a mixture including epoxy resin glue, metal oxide and polymer epoxy air spheres; the matching layer is a mixture including epoxy resin glue and metal oxide.

2. The piezoelectric composite transducer with adjustable guided wave excitation mode according to claim 1, characterized in that, both sides of the composite piezoelectric array layer are bonded to the backing layer and the matching layer respectively through epoxy resin glue.

3. The piezoelectric composite transducer with adjustable guided wave excitation mode according to claim 1, characterized in that, the decoupling material is a mixture including epoxy resin glue and polymer epoxy air spheres.

4. The piezoelectric composite transducer with adjustable guided wave excitation mode according to claim 1, characterized in that, the outer shape and structure of each piezoelectric composite array element are the same.

5. The piezoelectric composite transducer with adjustable guided wave excitation mode according to claim 1, characterized in that, the plurality of piezoelectric composite array elements are arranged at equal intervals along a straight line.

6. The piezoelectric composite transducer with adjustable guided wave excitation mode according to claim 1, characterized in that, each independent female header is respectively connected with a clamping piece; the clamping piece is connected with an external excitation signal source for introducing a circuit delay signal.

7. A working method of a piezoelectric composite transducer with adjustable guided wave excitation mode, characterized in that, A piezoelectric composite transducer with adjustable guided wave excitation mode as described in any one of claims 1-6 is adopted, including: selectively connecting some connection terminals on the double-row female header to the corresponding independent female header by plugging and unplugging wires to adjust the distribution of piezoelectric composite array elements, thereby controlling the wavelength of the guided wave excitation mode.

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