Piezoelectric superstructure capable of regulating and controlling axial bending wave transmission of shell structure

Abstract

A piezoelectric superstructure capable of regulating and controlling axial bending wave transmission of a shell structure comprises a cylindrical thin-wall shell substrate, piezoelectric fiber composite material patches which serve as piezoelectric transducers and are arranged on the inner side and the outer side of the substrate respectively, a shunt circuit connected with the two piezoelectric fiber composite material patches and a one-way coupling element. The bending wave passband is opened by changing the parameters of the external circuit network, the bending wave is allowed to be axially transmitted along the shell structure when the frequency is lower than the loop frequency, and the transmission amplitude can be regulated and controlled. And when the frequency is lower than the loop frequency, a local resonance passband is opened, and meanwhile, the transmission amplitude can be flexibly regulated and controlled, so that a new way is provided for structural health monitoring in the shell structure.

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 of a shell structure. Background Art

[0002] Superstructures are one of the latest technologies for achieving flexural wave control. Their negative effective properties break the shackles of traditional theories and provide new methods for solving wave control problems such as waveguides, stealth, and vibration suppression. Local resonant superstructures have attracted extensive research attention due to their subwavelength manipulation capabilities. Piezoelectric local resonant superstructures composed of piezoelectric materials and external shunt circuits have the advantages of small added mass, strong adaptability, and high design flexibility. They have broad application prospects in the fields of tunable wave control. However, most piezoelectric superstructures are used in low-dimensional structures such as beams, plates, and membranes, and usually use local resonant band gaps to suppress the transmission of flexural waves. Geometric curvature is a factor that has received little attention. It actually significantly affects the propagation of flexural waves by coupling in-plane vibrations and out-of-plane vibrations. For example, in cylindrical shell structures, due to curvature-induced coupling, flexural waves are prohibited from propagating along the axial direction below their ring frequency. This limits the applications in shell structures that rely on flexural wave propagation, such as structural health monitoring. Summary of the invention

[0003] In view of the deficiency of the prior art that the axial transmission and transmission rate of bending waves below the ring frequency cannot be adjusted, the present invention proposes a piezoelectric superstructure that can adjust the axial bending wave transmission of the shell structure. By changing the parameters of the external circuit network, the bending wave passband is opened, allowing the bending wave to be transmitted axially along the shell structure when it is lower than the ring frequency, and the transmission amplitude can be adjusted. While opening the local resonance passband below the ring frequency, the transmission amplitude can be flexibly adjusted, providing a new way for structural health monitoring in the shell structure.

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

[0005] The present invention relates to a piezoelectric superstructure capable of regulating axial bending wave transmission of a shell structure, comprising: a cylindrical thin-walled shell substrate, piezoelectric fiber composite material patches respectively arranged on the inner and outer sides of the substrate 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 are connected to the shunt circuit after being connected in parallel, each pair of piezoelectric fiber composite material patches and the cylindrical thin-walled shell substrate connected thereto and the shunt circuit form a unit, the shunt circuit contains switches and inductance elements, 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, each shunt circuit along the circumferential direction is independent of each other, and the cylindrical thin-walled shell substrate 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 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 according to actual needs to achieve axial transmission of bending waves, including:

[0010] 3.1 To prevent bending waves below the ring frequency from being transmitted along the axial direction: disconnect switch S;

[0011] 3.2 Enable the bending wave with a specified frequency below the ring frequency to be transmitted 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 the specified frequency below the ring frequency: Then, according to step 1, set the corresponding inductance parameter L and close the switch S, and adjust the unidirectional coupling coefficient according to step 2. Technical Effects

[0013] The present invention achieves control over the transmission characteristics of bending waves in the shell structure by designing a unidirectional circuit network coupled with a cylindrical thin-walled shell base to change the effective properties of the structure. Compared with the prior art, the present invention enables bending waves with a frequency lower than the ring frequency to be transmitted along the axial direction of the shell structure, and achieves controllable transmission amplitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of the present invention;

[0015] Figure 2 This is a schematic diagram of the structure of 1 / 4 of the present invention;

[0016] Figure 3 for Figure 1 Schematic diagram of local enlargement unit;

[0017] Figure 4 for Figure 1 Axial schematic diagram;

[0018] Figure 5 It is a schematic diagram of the circuit network of the present invention;

[0019] Figure 6 It is a schematic diagram of a unidirectional coupling element;

[0020] Figure 7 is a schematic diagram of the dispersion relation of an embodiment;

[0021] Figure 8 It is a diagram illustrating a scenario for implementing an embodiment;

[0022] Fig. 9 It is a schematic diagram of the vibration response when there is no control in the embodiment;

[0023] Fig.10 Schematic diagram of vibration response when the embodiment is controlled

[0024] Fig.11 It is a schematic diagram of the transmission amplitude control effect of the embodiment;

[0025] In the figure: 1 cylindrical thin-walled shell substrate, 2 piezoelectric fiber composite patch, 3 shunt circuit, 4 unidirectional coupling element. DETAILED DESCRIPTION

[0026] like Figure 1-Figure 6 As shown, the present embodiment relates to a piezoelectric superstructure capable of regulating axial bending wave transmission of a shell structure, comprising: a cylindrical thin-walled shell substrate 1, piezoelectric fiber composite patches 2 as piezoelectric transducers respectively arranged on the inner and outer sides of the substrate 1, 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 are 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 substrate 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, each shunt circuit 3 along the circumferential direction is independent of each other, and the substrate 1 and the last-stage shunt circuit 3 are both grounded.

[0027] All piezoelectric fiber composite material patches 2 have the same polarization direction, one side is pasted on the cylindrical thin-walled shell substrate 1, and the other side is connected to the shunt circuit 3. The piezoelectric fiber composite material patches 2 are symmetrically distributed about the neutral layer of the cylindrical thin-walled shell substrate 1, and are evenly distributed along the axial and circumferential directions of the cylindrical thin-walled shell substrate 1.

[0028] The unidirectional coupling element 4 comprises: 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.

[0029] The shunt circuit 3 comprises: an inductor L and a switch S. By adjusting the on-off state of the switch S, it is possible to control whether a bending wave lower than the loop frequency can be transmitted, and further adjusting the unidirectional coupling coefficient to achieve regulation of the transmission amplitude.

[0030] After theoretical analysis and numerical simulation, the radius of the cylindrical thin-walled shell base 1 is set to 500mm, the thickness is 1mm, the circumferential width and axial length are both 24mm; the thickness of the piezoelectric fiber composite patch 2 is 0.5mm, the circumferential width and axial length are both 20mm, and its average capacitance is 24.6nF; 12 units are set in the axial direction; the inductance L is set to 5H, the resistance R1 is set to 1MΩ, and the unidirectional coupling coefficient G=-R2 / R1 is changed by adjusting the value of R2.

[0031] 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 370 Hz to 430 Hz, allowing bending waves to be transmitted 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 waves 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 Schematic diagram of the effect shown. Fig. 9 The vibration response diagram of the embodiment without control is shown, that is, the switch S is disconnected. The excitation frequency is 390 Hz, at which time the shunt circuit has no regulating effect on the response of the structure, and the vibration response is localized on the excitation side, that is, the bending wave cannot be transmitted along the axial direction of the shell. Fig.10 Figure 1 is a schematic diagram of the vibration response of the embodiment when the 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 an obvious 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: Fig.11 The schematic diagram of the transmission amplitude regulation effect of the embodiment shown in the figure shows that within the frequency band of 370 Hz to 430 Hz, when the switch S in the shunt circuit 3 is disconnected, the transmission rate approaches 0, indicating that the bending wave cannot propagate along the axial direction when the frequency is lower than the ring frequency; and when the switch S in the shunt circuit 3 is closed, the transmission rate approaches 1, indicating that the bending wave can propagate along the axial direction at this time. Fig.11 The results shown are similar to Figure 7 The dispersion relation and Fig. 9 , Fig.10 The vibration response diagram of is well verified. Further changing the size of the one-way coupling coefficient G, such as Fig.11 As shown, the amplitude of the transmission rate can be adjusted.

[0032] Compared with the prior art, the present invention changes the effective properties of the structure by designing a unidirectional circuit network and coupling with the cylindrical thin-walled shell base without changing the mechanical structure, thereby opening a bending wave passband below the ring frequency in the cylindrical shell structure, making it possible for the bending wave to be transmitted along the axial direction of the cylindrical shell when the frequency is lower than the ring frequency, and further realizing the controllable transmission amplitude by adjusting the unidirectional coupling coefficient. Based on the principle of local resonance, the present invention focuses on the transmission characteristics of the bending wave when the frequency is lower than the ring frequency of the shell structure, makes full use of the flexibility and diversity of the external shunt circuit, greatly improves the adjustability of the axial transmission of the bending wave, provides a new idea for structural health monitoring, and has important engineering application value.

[0033] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme 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 of a shell structure, characterized in that: include: A cylindrical thin-walled shell substrate, piezoelectric fiber composite patches as piezoelectric transducers respectively arranged on the inner and outer sides of the substrate, 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 to the shunt circuit after being connected in parallel, each pair of piezoelectric fiber composite patches and the cylindrical thin-walled shell substrate and the shunt circuit connected thereto constitute a unit, 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, each shunt circuit along the circumferential direction is independent of each other, and the substrate and the last-stage shunt circuit are both grounded.

2. The piezoelectric superstructure for axial bending wave transmission of an adjustable shell structure according to claim 1, characterized in that: All piezoelectric fiber composite patches have the same polarization direction, one side is pasted on the cylindrical thin-walled shell base, and the other side is connected to the shunt circuit. The piezoelectric fiber composite 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. The piezoelectric superstructure for axial bending wave transmission of an adjustable shell structure according to claim 1, characterized in that: The unidirectional coupling element comprises: an operational amplifier and two resistors.

4. The piezoelectric superstructure for axial bending wave transmission of an adjustable shell structure according to claim 1, characterized in that: The shunt circuit includes: an inductor and a switch. By adjusting the on-off of the switch, it is possible to control whether the bending wave below the loop frequency can be transmitted, and further adjust the unidirectional coupling coefficient to achieve the regulation of the transmission amplitude.

5. A method for realizing axial transmission of bending waves based on the piezoelectric superstructure according to any one of claims 1 to 4, characterized in that: include: Step 1: Determine the ring frequency of the structure according to the geometric and physical parameters of the cylindrical thin-walled shell base and adjust the value of the inductance 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 needs to achieve axial transmission of bending waves.

6. The method according to claim 5, characterized in that: 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 in the shunt circuit, C p is the capacitance value of a pair of piezoelectric fiber composite patches connected in parallel.

7. The method according to claim 5, characterized in that: The unidirectional coupling coefficient G=-R2 / R1, wherein: R1 is a resistor of fixed size, R2 is an adjustable resistor; G=0 indicates that there is no coupling between adjacent units in the axial direction.

8. The method according to claim 5, characterized in that: The adjusting circuit parameters specifically include: 3.1 To prevent bending waves below the ring frequency from being transmitted along the axial direction: disconnect switch S; 3.2 Enable the bending wave with a specified frequency below the ring frequency to be transmitted along the axial direction: set the corresponding inductance parameter L according to step 1, and close the switch S; 3.3 Control the transmission rate of the bending wave along the axial direction at the specified frequency below the ring frequency: Then, according to step 1, set the corresponding inductance parameter L and close the switch S, and adjust the unidirectional coupling coefficient according to step 2.

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