Piezoelectric superstructure capable of controlling axial bending wave transmission in shell structures

Abstract

A piezoelectric superstructure capable of controlling axial flexural wave transmission within a shell structure comprises a cylindrical thin-walled shell substrate, piezoelectric fiber composite patches acting as piezoelectric transducers disposed on the inner and outer sides of the substrate, and a shunt circuit and unidirectional coupling element connected to the two piezoelectric fiber composite patches. By modifying the parameters of the external circuit network, the present invention opens a flexural wave passband, allowing flexural wave transmission along the axial direction of the shell structure below the ring frequency, while also achieving controllable transmission amplitude. While opening a local resonant passband below the ring frequency, the transmission amplitude can be flexibly controlled, providing a new approach for structural health monitoring within shell structures.

Description

Technical Field

[0001] The present invention relates to a technology in the field of superstructures, in particular to a piezoelectric superstructure capable of regulating the transmission of axial bending waves in a shell structure. Background Art

[0002] Metastructures are one of the latest technologies for flexural wave control. Their negative effective properties break the constraints of traditional theories and provide new approaches to addressing wave manipulation challenges such as waveguiding, stealth, and vibration suppression. Locally resonant metastructures (LRMs) have attracted extensive research attention due to their subwavelength manipulation capabilities. Composed of piezoelectric materials and external shunt circuits, LRMs offer advantages such as low added mass, strong adaptability, and high design flexibility, holding great promise for applications in tunable wave control. However, most piezoelectric LRMs are applied in low-dimensional structures such as beams, plates, and membranes, typically utilizing the LR band gap to suppress flexural wave propagation. Geometric curvature, a factor that has received less attention, can significantly influence flexural wave propagation by coupling in-plane and out-of-plane vibrations. For example, in cylindrical shells, curvature-induced coupling inhibits axial flexural wave propagation below the ring frequency. This limits applications in shell structures that rely on flexural wave propagation, such as structural health monitoring. Summary of the Invention

[0003] To address the limitations of existing technologies, which cannot regulate the axial transmission and transmission rate of bending waves below the ring frequency, this present invention proposes a piezoelectric metastructure that can control the axial transmission of bending waves in shell structures. By modifying the parameters of the external circuit network, the flexural wave passband is opened, allowing flexural wave transmission along the axial direction of the shell structure below the ring frequency, and the transmission amplitude can be controlled. While opening the local resonance passband below the ring frequency, the transmission amplitude can be flexibly controlled, providing a new approach for structural health monitoring in shell structures.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a piezoelectric superstructure capable of regulating the axial bending wave transmission of a shell structure, comprising: a cylindrical thin-walled shell base, piezoelectric fiber composite material patches respectively arranged on the inner and outer sides of the base as piezoelectric transducers, a shunt circuit connected to the two piezoelectric fiber composite material patches, and a unidirectional coupling element, wherein: each pair of piezoelectric fiber composite material patches is connected to the shunt circuit after being connected in parallel, each pair of piezoelectric fiber composite material patches and the cylindrical thin-walled shell base connected thereto and the shunt circuit constitute a unit, the shunt circuit contains a switch and an inductor element, the unidirectional coupling element is arranged between two adjacent shunt circuits along the axial direction to form a unidirectional circuit network along the axial direction, the shunt circuits along the circumferential direction are independent of each other, and the cylindrical thin-walled shell base and the last-stage shunt circuit are both grounded.

[0006] The present invention relates to a method for realizing axial transmission of bending waves in the above-mentioned piezoelectric superstructure, comprising:

[0007] Step 1: Determine the ring frequency of the structure based on the geometric and physical parameters of the cylindrical thin-walled shell base and adjust the value of the inductor element in the shunt circuit so that the resonant frequency of the circuit is below the ring frequency of the structure, specifically: Ring frequency Where: C is the tensile stiffness of the cylindrical thin-walled shell base, m is the area mass, R is the radius; the resonant frequency Where: L is the value of the inductor component in the shunt circuit, C p is the capacitance value of a pair of piezoelectric fiber composite patches connected in parallel.

[0008] Step 2: Determine the unidirectional coupling coefficient G = -R2 / R1, where: R1 is a fixed resistor, R2 is an adjustable resistor; G = 0 means there is no coupling between adjacent units in the axial direction.

[0009] Step 3: Adjust the circuit parameters to achieve axial bending wave transmission based on actual requirements, including:

[0010] 3.1 Prevent bending waves below the ring frequency from propagating along the axial direction: Open switch S;

[0011] 3.2 Enable bending waves with a specified frequency below the ring frequency to propagate along the axial direction: Set the corresponding inductance parameter L according to step 1 and close the switch S;

[0012] 3.3 Control the transmission rate of the bending wave along the axial direction at a specified frequency below the ring frequency: Based on setting the corresponding inductance parameter L and closing the switch S according to step 1, adjust the unidirectional coupling coefficient according to step 2.

[0013] Technical Effects

[0014] This invention modifies the effective properties of the structure by coupling a unidirectional circuit network with the cylindrical thin-walled shell base. This allows for the control of the transmission characteristics of bending waves within the shell structure. Compared to existing technologies, this invention enables the axial transmission of bending waves below the ring frequency along the shell structure, and also allows for controllable transmission amplitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of 1 / 4 of the present invention;

[0017] Figure 3 for Figure 1 Schematic diagram of the local magnification unit;

[0018] Figure 4 for Figure 1 Axial schematic diagram;

[0019] Figure 5 Schematic diagram of the circuit network of the present invention;

[0020] Figure 6 It is a schematic diagram of a unidirectional coupling element;

[0021] Figure 7 Schematic diagram of the dispersion relation of the embodiment;

[0022] Figure 8 This is a diagram illustrating a scenario for implementing an embodiment;

[0023] Figure 9 Schematic diagram of vibration response when there is no control in the embodiment;

[0024] Figure 10 Schematic diagram of vibration response when the embodiment is controlled

[0025] Figure 11 This is a schematic diagram of the transmission amplitude control effect of the embodiment;

[0026] In the figure: 1 cylindrical thin-walled shell base, 2 piezoelectric fiber composite patch, 3 shunt circuit, 4 unidirectional coupling element. DETAILED DESCRIPTION

[0027] like Figures 1-6 As shown, this embodiment relates to a piezoelectric superstructure for controllable axial bending wave transmission of a shell structure, comprising: a cylindrical thin-walled shell base 1, piezoelectric fiber composite patches 2 respectively arranged on the inner and outer sides of the base 1 as piezoelectric transducers, a shunt circuit 3 and a unidirectional coupling element 4 connected to the two piezoelectric fiber composite patches 2, wherein: each pair of piezoelectric fiber composite patches 2 is connected to the shunt circuit 3 after being connected in parallel, each pair of piezoelectric fiber composite patches 2 and the cylindrical thin-walled shell base 1 and the shunt circuit 3 connected thereto constitute a unit, the unidirectional coupling element 4 is arranged between two adjacent shunt circuits 3 along the axial direction to form a unidirectional circuit network along the axial direction, and each shunt circuit 3 along the circumferential direction is independent of each other, and the base 1 and the last-stage shunt circuit 3 are both grounded.

[0028] All piezoelectric fiber composite patches 2 have the same polarization direction, one side is pasted on the cylindrical thin-walled shell base 1, and the other side is connected to the shunt circuit 3. The piezoelectric fiber composite patches 2 are symmetrically distributed about the neutral layer of the cylindrical thin-walled shell base 1 and are evenly distributed along the axial and circumferential directions of the cylindrical thin-walled shell base 1.

[0029] The unidirectional coupling element 4 includes an operational amplifier, a resistor R1 and a resistor R2, wherein the values ​​of the resistor R1 and the resistor R2 determine the unidirectional coupling coefficient.

[0030] The shunt circuit 3 includes an inductor L and a switch S. By adjusting the on-off state of the switch S, whether a bending wave below the loop frequency can be transmitted can be controlled. Further adjusting the unidirectional coupling coefficient can achieve control of the transmission amplitude.

[0031] After theoretical analysis and numerical simulation, the radius of the cylindrical thin-walled shell base 1 is set to 500 mm, the thickness is 1 mm, the circumferential width and axial length are both 24 mm; the thickness of the piezoelectric fiber composite patch 2 is 0.5 mm, the circumferential width and axial length are both 20 mm, and its average capacitance is 24.6 nF; 12 of the units are set in the axial direction; the inductance L is set to 5 H, the resistance R1 is set to 1 MΩ, and the unidirectional coupling coefficient G = -R2 / R1 is changed by adjusting the value of R2.

[0032] Under the above parameters, the ring frequency of the simulated piezoelectric superstructure shell is f r =1230Hz, the resonant frequency of the shunt circuit is f cir =450Hz, so the circuit resonant frequency is below the ring frequency of the shell. Figure 7 The dispersion relation shown in Figure 2 shows that the bending wave passband is open around 370Hz to 430Hz, allowing bending waves to propagate along the shell axis. Figure 8 In the implementation scenario shown, since the structure is circularly symmetric in the circumferential direction, it is only necessary to construct a structural model with 1 unit in the circumferential direction and 12 units in the axial direction. The vibration response of the complete cylindrical shell can be simulated by applying circularly symmetric boundary conditions in the circumferential direction. A force of 1N is applied radially on one side of the piezoelectric superstructure shell, and a perfect matching layer is applied on the other side to absorb the bending wave and avoid reflection. The ratio of the average acceleration on the transmission side to the average acceleration on the excitation side is calculated to represent the transmission rate. Running the above device, the following is obtained: Figures 9 to 11 The effect diagram is shown. Figure 9 This diagram shows the vibration response of the embodiment without control, i.e., switch S is open. At an excitation frequency of 390 Hz, the shunt circuit has no effect on the structural response, and the vibration response is localized on the excitation side, meaning that bending waves cannot propagate along the axial direction of the housing. Figure 10 Figure 2 is a schematic diagram of the vibration response of the embodiment under control, that is, switch S is closed and the one-way coupling coefficient G is set to 0. The excitation frequency is still 390Hz. At this time, there is a significant bending vibration response in the axial direction of the shell. The results show that under the control of the shunt circuit, the bending wave can be transmitted along the axial direction of the shell. The transmission rate from 350Hz to 450Hz is calculated as follows: Figure 11 The schematic diagram of the transmission amplitude control effect of the embodiment shown in FIG. 1 shows that, within the frequency band of 370 Hz to 430 Hz, when the switch S in the shunt circuit 3 is open, the transmission rate approaches 0, indicating that bending waves cannot propagate axially below the ring frequency. However, when the switch S in the shunt circuit 3 is closed, the transmission rate approaches 1, indicating that bending waves can propagate axially. Figure 11 The results shown are Figure 7 The dispersion relation and Figure 9 、 Figure 10 The vibration response diagram of is well verified. Further changing the size of the one-way coupling coefficient G, such as Figure 11 As shown, the amplitude of the transmissibility can be controlled.

[0033] Compared with existing technologies, this invention modifies the effective properties of the structure by designing a unidirectional circuit network coupled to the cylindrical thin-walled shell base, without changing the mechanical structure. This opens a flexural wave passband below the ring frequency within the cylindrical shell structure, enabling flexural wave transmission along the axial direction of the cylindrical shell below the ring frequency. Furthermore, by adjusting the unidirectional coupling coefficient, the transmission amplitude can be controlled. Based on the principle of local resonance, this invention focuses on the transmission characteristics of flexural waves below the ring frequency of the shell structure. By leveraging the flexibility and versatility of an external shunt circuit, this invention significantly improves the adjustability of flexural wave transmission along the axial direction, providing new insights into structural health monitoring and possessing significant engineering applications.

[0034] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A piezoelectric superstructure capable of regulating axial bending wave transmission in a shell structure, characterized in that: include: A cylindrical thin-walled shell substrate, piezoelectric fiber composite patches serving as piezoelectric transducers disposed on the inner and outer sides of the substrate, respectively, a shunt circuit connected to the two piezoelectric fiber composite patches, and a unidirectional coupling element, wherein: each pair of piezoelectric fiber composite patches is connected in parallel to the shunt circuit, each pair of piezoelectric fiber composite patches and the cylindrical thin-walled shell substrate and shunt circuit connected thereto constitute a unit, the unidirectional coupling element is disposed between two adjacent shunt circuits along the axial direction to form a unidirectional circuit network along the axial direction, the shunt circuits along the circumferential direction are independent of each other, and the substrate and the last-stage shunt circuit are both grounded; The unidirectional coupling element includes: an operational amplifier and two resistors; The shunt circuit includes an inductor and a switch. By adjusting the on-off state of the switch, whether a bending wave lower than the loop frequency can be transmitted can be controlled. The unidirectional coupling coefficient can be further adjusted to achieve control of the transmission amplitude.

2. The piezoelectric superstructure for axial bending wave transmission in a controllable shell structure according to claim 1, characterized in that: All the piezoelectric fiber composite material patches have the same polarization direction, one side is attached to the cylindrical thin-walled shell base, and the other side is connected to the shunt circuit. The piezoelectric fiber composite material patches are symmetrically distributed about the neutral layer of the cylindrical thin-walled shell base (1) and are evenly distributed along the axial and circumferential directions of the cylindrical thin-walled shell base.

3. A method for realizing axial transmission of bending waves based on the piezoelectric superstructure according to claim 1 or 2, characterized in that: include: Step 1: Determine the ring frequency of the structure based on the geometric and physical parameters of the cylindrical thin-walled shell base and adjust the value of the inductor element in the shunt circuit so that the resonant frequency of the circuit is below the ring frequency of the structure; Step 2: Determine the one-way coupling coefficient; Step 3: Adjust the circuit parameters according to actual requirements to achieve axial transmission of bending waves.

4. The method according to claim 3, wherein: The ring frequency , where: C is the tensile stiffness of the cylindrical thin-walled shell base, m is the area mass, and R is the radius; the resonant frequency , where: L is the value of the inductor component in the shunt circuit, C p is the capacitance value of a pair of piezoelectric fiber composite patches connected in parallel.

5. The method according to claim 3, wherein: The one-way coupling coefficient , where: R1 is a fixed resistor, R2 is an adjustable resistor; G=0 means there is no coupling between adjacent units in the axial direction.

6. The method according to claim 3, wherein: The adjustment of circuit parameters in step 3 specifically includes: 3.1) Prevent bending waves below the ring frequency from propagating along the axial direction: Open switch S; 3.2) Enabling axial transmission of bending waves at a specified frequency below the ring frequency: Set the corresponding inductance parameter L according to step 1 and close the switch S; 3.3) Controlling the transmission rate of bending waves along the axial direction at a specified frequency below the ring frequency: After setting the corresponding inductance parameter L and closing the switch S according to step 1, adjust the unidirectional coupling coefficient according to step 2.

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