A device for measuring the dynamic coupling piezoelectric effect of a thin film element

Abstract

The application relates to the technical field of thin film element performance testing, and particularly discloses a device for measuring the dynamic coupling piezoelectric effect of a thin film element, which comprises a double-curved waveguide rod system having a merging section for receiving the impact of an impact rod and two symmetrical curved sections, the downstream ends of the curved sections extending into linear sections; an incident rod system comprising an incident rod one and an incident rod two arranged orthogonally, the two rods being connected to the ends of the two linear sections through connecting parts to receive compression stress waves and generate tensile stress waves; a transmission rod system comprising a transmission rod one and a transmission rod two; and a cross-shaped thin film sample, four clamping areas of the sample being connected to the two incident rods and the two transmission rods through adapters, and the center of a test area of the sample being provided with a sensitive area with piezoelectric effect. The device can convert a single impact into synchronous and orthogonal biaxial tensile stress waves, and directly act on the sensitive area of the sample, so that the loading and measurement of the biaxial orthogonal impact tensile dynamic force-electric coupling effect of the thin film element can be realized.

Description

Technical Field

[0001] This invention relates to the field of thin-film element performance testing technology, and in particular to a device for measuring the dynamic coupling piezoelectric effect of thin-film elements. Background Technology

[0002] Dynamic pressure measurement based on the out-of-plane deflection of an elastic thin-film element is a widely used working principle of pressure sensors. Its core sensing element is typically a circumferentially fixed circular metal thin film, whose thickness is much smaller than its diameter, and it undergoes deflection deformation under out-of-plane pressure. According to the small deflection theory of thin-plate bending in elastic mechanics, the deflection of the film is linearly related to the applied out-of-plane pressure. By measuring the strain in a specific region of the film, the pressure information acting on its surface can be simultaneously obtained.

[0003] If the sensing element itself possesses electromechanical response characteristics or deformation-electrical coupling response characteristics, then the thin film can not only serve as an elastic sensing element that senses pressure and generates deformation, but also directly output deformation-related electrical signals, thereby achieving structural-functional integration. This is a novel working mode for pressure sensors. For example, Chinese Patent CN113432772A discloses a highly sensitive thin-film sensor for measuring shock waves on object surfaces and its fabrication method. This sensor is based on the in-plane piezoelectric effect of PVDF thin films, encapsulating the piezoelectric polymer film into a measuring element and subjecting it to circumferential fixed-support constraints. Under the action of a shock wave, the thin film generates an in-plane tensile stress field. Utilizing the coupled piezoelectric effect of the d31 and d32 piezoelectric modes, it can achieve extremely high charge output under relatively low-intensity shock waves, becoming a novel measurement technology with excellent performance.

[0004] In this coupled piezoelectric effect operating mode, the thin-film elastic element is under a complex stress state during flexural deformation, with its central sensitive region exhibiting primarily a biaxial orthogonal tensile stress state. Under these conditions, the electromechanical response of the piezoelectric element differs significantly from that under uniaxial tension or compression. Therefore, using the piezoelectric coefficient matrix obtained from uniaxial tension-compression calibration to calculate the coupled piezoelectric response will result in significant deviations. Furthermore, piezoelectric polymer films are mainly used for high-frequency pressure signal measurement, and polymer materials themselves exhibit a significant strain rate effect. Therefore, their electromechanical coupling response must be measured at a deformation rate closely resembling their actual working environment. Currently, piezoelectric coefficient calibration primarily employs a quasi-static compression method, yielding results with substantial deviations from dynamic coefficients. In particular, there is a lack of measurement and calibration devices specifically designed for the electromechanical response under biaxial orthogonal impact tension in the coupled piezoelectric operating mode. Summary of the Invention

[0005] The purpose of this invention is to provide a device for measuring the dynamic coupling piezoelectric effect of thin-film elements, thereby solving the aforementioned technical problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: a device for measuring the dynamic coupling piezoelectric effect of a thin-film element, comprising: a hyperbolic waveguide rod system, including a merging segment for receiving impacts, wherein two symmetrical and curved segments are connected downstream of the merging segment, each curved segment extending downstream of a straight segment, the two straight segments being orthogonally distributed in the same plane, the merging segment being connected to an impact rod to receive the impact from the impact rod; and an incident rod system, including an incident rod one and an incident rod two, which are orthogonally arranged and connected to the two straight segments respectively via connecting portions. The end connection is used to receive compressive stress waves from the hyperbolic waveguide rod system and excite tensile stress waves; the transmission rod system includes transmission rod one and transmission rod two, which are respectively arranged coaxially with the incident rod one and the incident rod two, for receiving transmitted waves passing through the cross-shaped thin film sample; and the cross-shaped thin film sample has four clamping areas and a test area located in the center, the four clamping areas being connected to the incident rod one, the incident rod two, the transmission rod one, and the transmission rod two via adapters, and the center of the test area having a sensitive area with piezoelectric effect.

[0007] Optionally, the adapter includes a shaft and a sample connecting section, the shaft being used to connect the incident rod system and / or the transmission rod system, and the sample connecting section having multiple slits for fixing the sample.

[0008] Optionally, the number of slits on the sample connection section of the adapter is even, and they are symmetrically distributed on both sides of the longitudinal symmetry plane of the shaft, for simultaneously mounting multiple cross-shaped thin film samples.

[0009] Optionally, an arc-shaped groove is slidably connected to the outer side of the curved segment, the radius of curvature of the arc-shaped groove matching the radius of curvature of the curved segment, for forming a radial constraint on the curved segment.

[0010] Optionally, the connecting part is a pin, and the end of the straight segment and the front end of the incident rod system are respectively provided with connecting holes, and are connected by the pin.

[0011] Optionally, the connecting part is a boss provided at the front end of the incident rod system, and the end of the straight segment is in contact with the boss. The connection is achieved and the stress wave is transmitted by the impact of the stress wave on the boss.

[0012] Optionally, the sensitive area of ​​the cross-shaped thin film sample is locally polarized and has upper and lower surface electrodes, while the rest of the test area has the same material and thickness as the sensitive area but does not have piezoelectric properties.

[0013] Optionally, strain gauges are attached to the rods of the incident rod system and the transmission rod system to measure the incident wave, reflected wave and transmitted wave signals.

[0014] Optionally, the incident rod system is made of a low-impedance material, and the transmission rod system is made of a material with even lower impedance than the incident rod system.

[0015] Optionally, the length of the impact rod is not greater than half the length of the combined segment of the hyperbolic waveguide rod system.

[0016] Compared with the prior art, the present invention discloses at least the following beneficial effects: This invention utilizes a uniquely designed hyperbolic waveguide rod system to decompose and guide the single compressive stress wave generated by the impact rod into two synchronous, symmetrical, and orthogonally distributed compressive sub-waves in the same plane. An orthogonally arranged incident rod system receives these two sub-waves and transforms them into synchronously propagating high-quality biaxial tensile stress waves. These tensile waves act synchronously on the four clamping areas of the cross-shaped thin film sample via an adapter, ensuring that the sensitive area of ​​the central test zone is precisely in a dynamic stress state of biaxial orthogonal tension. Simultaneously, a transmission rod system coaxially arranged with the incident rod receives the transmitted wave signal. This organic synergy of the above structures achieves, for the first time, a high-quality biaxial tensile stress wave at 10... 2 ~10 4 s -1 Within the high strain rate range, the dynamic electromechanical coupling effect of biaxial orthogonal impact tensile stress on thin film elements is directly and synchronously loaded and measured, effectively simulating the complex stress state under actual coupled piezoelectric working mode. This provides a direct and reliable technical means for accurately calibrating the dynamic piezoelectric coefficient under this specific stress state. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the overall structure of the device for measuring the dynamic coupling piezoelectric effect of a thin-film element provided in an embodiment of the present invention; Figure 2 for Figure 1 The enlarged view at point A shows the positional relationship between the adapter and the cross-shaped thin film sample in the device of the present invention. Figure 3 for Figure 1 The enlarged view at point B shows a schematic diagram of the connection relationship between the incident rod system and the hyperbolic waveguide rod system in the device of the present invention. Figure 4 This is a schematic diagram illustrating another connection relationship between the incident rod system and the hyperbolic waveguide rod system in the device of the present invention; Figure 5This is a top view of the device of the present invention; Figure 6 This is a schematic diagram of the orthogonal arrangement of the Hopkinson rods, consisting of the incident rod and the transmission rod, in the device of the present invention. Figure 7 This is a schematic diagram of the hyperbolic waveguide rod system in the device of the present invention; Figure 8 This is a schematic diagram showing the connection relationship between the adapter and the cross-shaped thin film sample in the device of the present invention; Figure 9 This is a schematic diagram of the adapter structure in the device of the present invention; Figure 10 This is a schematic diagram of the cross-shaped thin film sample in the device of the present invention; Figure 11 This is a synchronous tensile stress wave diagram on the incident rod system provided in an embodiment of the present invention.

[0019] Reference numerals: 1. Hyperbolic waveguide rod system; 11. Merging section; 12. Bending section; 13. Straight section; 14. Arc groove; 15. Connecting hole; 2. Incident rod system; 21. Incident rod one; 22. Incident rod two; 3. Transmission rod system; 31. Transmission rod one; 32. Transmission rod two; 4. Adapter; 41. Shaft; 42. Sample connection section; 5. Cross-shaped thin film sample; 51. Clamping area; 52. Test area; 53. Sensitive area; 6. Impact rod; 7. Connecting part. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Reference Figures 1 to 10 As shown, this embodiment provides a device for measuring the dynamic coupled piezoelectric effect of a thin film element. This device aims to simultaneously measure the mechanical and electrical responses of a thin film element exhibiting coupled piezoelectric effect under biaxial orthogonal, high-strain-rate tensile stress conditions, based on the Hopkinson pressure bar principle, thereby accurately calibrating its dynamic piezoelectric coefficient under this complex stress state. The device mainly includes a hyperbolic waveguide rod system 1, an incident rod system 2, a transmission rod system 3, an adapter 4, a cross-shaped thin film sample 5, an impact rod 6, and a connecting part 7.

[0023] In one specific embodiment, the hyperbolic waveguide rod system 1 serves as the core waveguide and conversion component of the device, and its structure is as follows: Figure 7 As shown, the hyperbolic waveguide system 1 consists of two symmetrically curved waveguide rods that fuse at the impact end to form a merging section 11. The cross-sectional area of ​​the merging section 11 is approximately twice that of a single waveguide rod, used to receive the impact of the impact rod 6. Starting downstream of the merging section 11, the two waveguide rods bend to the left and right, forming an arc-shaped curved section 12 with a central angle of approximately 45°. A matching arc-shaped groove 14 is provided on the outer side of the curved section 12, which provides radial constraint to the curved section 12, ensuring that the waveguide rod can only deform and move along its bending axis when impacted, thereby precisely guiding the propagation path of the stress wave. A straight section 13 extends downstream of the curved section 12, and the two straight sections 13 are ultimately orthogonally distributed in the same horizontal plane. The material, length, curvature, and cross-sectional shape and size of the entire curved waveguide are kept consistent to ensure the synchronicity and symmetry of stress wave decomposition and propagation. The impact rod 6 is a straight rod with a circular cross section. Its material is consistent with that of the merging section 11 of the curved waveguide rod, and its length is no more than half the length of the merging section 11 to ensure that a clear compressive stress wave is generated.

[0024] In one specific embodiment, the bent waveguide rod can be made of 7075 aluminum alloy. The impact rod 6 can be designed as a straight rod with a cross-sectional diameter of 12.7 mm and a length of 100 mm. The bent waveguide rod can be composed of a bent segment 12 with a radius of curvature of 210 mm and a central angle of 45°, a merging segment 11 with a length of 200 mm, and a straight segment 13 with a length of 200 mm. An arc-shaped groove 14 with the same radius of curvature of 210 mm is slidably connected below the bent segment 12. The cross-section of the entire bent waveguide rod can be an 8 mm × 8 mm square, wherein the length of the merging segment 11 is 200 mm. The bent segment 12 is constrained by the arc-shaped groove 14, so that it always moves along a trajectory with the same radius of curvature during the impact. The bent waveguide rod is a one-piece machined structure, and the end of its straight segment 13 can be provided with a connecting hole 15 with a diameter of 5 mm for installing a pin-type connecting part 7.

[0025] Based on the above embodiments, the incident rod system 2 is further used to receive and convert stress waves. For example... Figure 1 , Figure 3 , Figure 4 , Figure 6As shown, the incident rod system 2 includes incident rod one 21 and incident rod two 22, which are straight rods arranged orthogonally to each other, located on the plane above the curved waveguide rods, forming a longitudinal three-dimensional layout. The front ends of incident rod one and incident rod two 22 are respectively connected to the tail ends of the straight segments 13 of the two curved waveguide rods through connecting parts 7. The incident rod one 21 and incident rod two 22 are made of the same material, length and cross-section to ensure synchronous loading. Their cross-sections can be circular or rectangular, preferably using low-impedance materials (such as polymers such as plexiglass, polycarbonate or nylon) to improve the wave impedance matching with the thin film sample, but their generalized wave impedance must be matched with the hyperbolic waveguide rod system 1 to ensure the generation of high-quality tensile incident waves. Strain gauges are attached to the middle part of the incident rod system 2 for measuring incident and reflected wave signals.

[0026] In one specific embodiment, the incident rod system 2 can also be made of 7075 aluminum alloy, with a length of 240mm and a square cross-section of 8mm×8mm. The incident rod system 2, through the installation of the adapter 4, is positioned above the hyperbolic waveguide rod system 1, forming a longitudinal three-dimensional layout, thereby avoiding spatial interference.

[0027] Regarding the specific implementation of the connecting part 7, the present invention provides two preferred embodiments: In one specific embodiment, such as Figure 3 As shown, the connecting part 7 is a pin, and connecting holes 15 are machined at the tail end of the straight section 13 of the curved waveguide rod and the front end of the incident rod (incident rod one 21 / incident rod two 22), and the two are connected in parallel by a 5mm rigid pin. When the stress wave propagates to the end of the curved waveguide rod, it impacts the incident rod system 2 through the shear pin, thereby exciting a tensile stress wave therein.

[0028] In another specific embodiment, such as Figure 4 As shown, the connecting part 7 is designed as a boss connection. An integral or bolted boss is machined at the front end of the incident rod as an impact flange. The boss height can be 8mm and the length can be 20mm. In the initial state, the tail end of the straight section 13 of the bent waveguide rod is in contact with this boss. When the stress wave arrives, it directly impacts the boss, propelling it forward and creating a one-time impact tensile load on the incident rod. The boss connection effectively avoids mutual interference between the waveguide rod and the incident rod during subsequent movement.

[0029] Based on the above embodiments, the adapter 4, as a key component connecting the rod system and the sample, has the following structure: Figure 8 and Figure 9As shown. The adapter 4 mainly includes a shaft 41 and a sample connecting section 42. One end of the shaft 41 is provided with an external thread for tightening with the internal thread structure of the rod end of the incident rod or transmission rod. The cross-sectional shape of the sample connecting section 42 matches the rod, and multiple slits are opened on it. These slits are evenly distributed on both sides of the longitudinal symmetry plane of the shaft 41. The clamping area 51 of the cross-shaped thin film sample 5 can be fixed in the slits with high-strength adhesive. This design allows multiple thin film samples to be installed simultaneously in one test, which enhances the transmitted wave signal intensity by increasing the generalized wave impedance ratio between the sample and the rod system, and effectively suppresses the eccentric effect through symmetrical installation, thereby improving the test accuracy and efficiency.

[0030] In one specific embodiment, the shaft 41 of the adapter 4 can be an M6 external threaded screw, and the ends of the incident rod system 2 and the transmission rod system 3 are machined with corresponding M6 internal threads. The cross-section of the sample connection section 42 of the adapter 4 is the same as that of the rod. A double-slit design can be used to install the sample, so that the force and electrical response of two cross-shaped thin film samples 5 can be measured simultaneously in a single experiment. The slit width can be matched with the sample clamping area 51, for example, 8 mm, and the gap thickness can be matched with the sample thickness, for example, 1 mm.

[0031] In this embodiment, the cross-shaped thin film sample 5 is the piezoelectric sensing element to be tested, and its structure is as follows: Figure 10 As shown, the sample is cross-shaped, with four clamping areas 51 and a rectangular test area 52 in the center. The center of the test area 52 has a sensitive area 53 of a specific shape (e.g., circular), which is locally polarized and has upper and lower surface electrodes to achieve a piezoelectric effect for outputting a force-electric response signal. The remaining part of the test area 52 has the same material and thickness as the sensitive area 53 but does not possess piezoelectric properties to ensure uniform stress transmission. The four clamping areas 51 of the sample are connected to two incident rods and two transmission rods via adapters 4, respectively.

[0032] In one specific embodiment, the thickness of the cross-shaped thin film sample 5 can be 1 mm, and the size of the clamping area 51 is 8 mm × 8 mm. The size of the test area 52 is 8 mm × 8 mm, and a circular sensitive area 53 with a diameter of 5 mm is machined in the center. Thin film electrodes are machined on both sides of the sensitive area 53 to discharge the charge generated by the element during the impact and stretching process.

[0033] Furthermore, the transmission rod system 3 is used to receive the transmitted wave passing through the sample. For example... Figure 1 and Figure 6As shown, the transmission rod system 3 includes a transmission rod 31 arranged coaxially with the incident rod 21, and a transmission rod 32 arranged coaxially with the incident rod 22. The two sets of incident rods and transmission rods together form a cross-shaped test area 52. The material, length, and cross-sectional shape of transmission rods 31 and 32 must be consistent. To enhance the transmitted wave signal, their material can be a material with lower impedance than the incident rod (such as plexiglass). Strain gauges are also attached to the middle part of the transmission rods (transmission rod 31 / transmission rod 32) for measuring the transmitted wave.

[0034] In one specific embodiment, the transmission rod system 3 can be composed of two square rods with a cross-section of 8mm×8mm, using low-impedance plexiglass material to improve the intensity of the transmitted wave signal of the sample.

[0035] Reference Figure 11 As shown in the figure, the tensile stress wave waveforms measured on the two incident rods (incident rod 1 21 and incident rod 22) during a biaxial orthogonal tensile loading experiment are illustrated. The results show that the stress wave waveforms on the two incident rods have good repeatability, verifying that the device can generate biaxial orthogonal tensile stress waves with high synchronization and consistency, thereby realizing impact tensile loading on thin film samples under complex stress states.

[0036] The working principle of the device in this embodiment is as follows: The impact rod 6 is driven by the Hopkinson pressure rod's launching device to strike the end face of the merging section 11 of the curved waveguide rod at a certain speed (e.g., 9 m / s), generating a compressive stress wave. This compressive wave, upon propagating to the curved section 12, is decomposed into two synchronous, symmetrical compressive sub-waves, which then change direction along the trajectory of the curved section 12. Ultimately, these two compressive waves arrive synchronously at the end of the straight section 13 of the curved waveguide rod in two orthogonal directions in the horizontal plane, and strike the corresponding incident rods through the connecting part 7, thereby synchronously exciting tensile stress waves in the two incident rods. These two tensile waves propagate along the incident rods and are recorded as incident waves by strain gauges on them. When the tensile waves reach the adapter 4, a synchronous, orthogonal biaxial dynamic tensile load is applied to the cross-shaped thin film sample 5 installed therein. Under this complex stress field, the sample deforms, and its sensitive area 53 generates a charge due to the piezoelectric effect, which is output to an external charge measurement module through electrode leads. Simultaneously, part of the wave is reflected at the sample interface to form a reflected wave, which is recorded by the strain gauge on the incident rod; the other part of the wave is transmitted through the sample to form a transmitted wave, which is recorded by the strain gauge on the transmission rod system 3. By synchronously acquiring the strain signal on the rod system (used to calculate stress, strain, and strain rate) and the charge signal output by the sample (or the amplified voltage signal), the dynamic electromechanical coupling characteristics of the thin film element under high strain rate biaxial tension can be analyzed, and its coupling piezoelectric coefficient can be calibrated.

[0037] Compared with the prior art, the present invention has the following beneficial effects: The device for measuring the dynamic coupling piezoelectric effect of thin-film elements provided by this invention can accurately achieve orthogonal biaxial synchronous impact tensile loading on a cross-shaped thin-film sample 5, thereby effectively simulating the real working characteristics of the coupled piezoelectric effect measuring element in a diaphragm pressure sensor under complex stress conditions. This device uses a hyperbolic waveguide rod system 1 to decompose and redirect a single compressive stress wave into two orthogonal synchronous compressive waves, which are then converted into high-quality tensile stress waves by orthogonally arranged incident rod system 2 and transmission rod system 3, ultimately achieving a 10... 2 ~10 4 s -1 The sample is loaded within a high strain rate range. This waveguide and loading design based on structural symmetry fundamentally ensures the synchronicity and consistency of biaxial loading, solving the problem that traditional devices struggle to achieve high-precision synchronous impact loading.

[0038] Furthermore, the adapter 4 used in the device is designed to simultaneously install and test multiple sets of samples. By setting symmetrically distributed slits, multiple cross-shaped thin-film samples 5 can be fixed in a single test. This not only improves the generalized wave impedance ratio between the sample and the rod system, effectively enhancing the transmitted wave signal intensity and test accuracy, but also significantly suppresses measurement errors caused by sample clamping eccentricity through symmetrical installation. Simultaneously, the adapter 4 is threaded to the rod system, and the sample is fixed with adhesive, allowing for quick replacement of the adapter 4 assembly with the sample after each experiment, greatly improving testing efficiency.

[0039] Furthermore, the specially designed cross-shaped thin film specimen 5 forms a precisely sized sensitive region 53 at the center of its test area 52. This sensitive region 53 is locally polarized and fabricated with electrodes, enabling it to specifically output piezoelectric signals under biaxial tensile stress, while the rest of the specimen only serves to uniformly transmit the load. This design ensures that the piezoelectric functional region under test is always in a region with a relatively uniform stress distribution and is subjected to a high strain rate load consistent with the actual working condition, thus making the measurement results more accurately reflect the performance of the component under dynamic coupling piezoelectric effects.

[0040] Finally, this device, through the strain measurement module integrated on the incident rod system 2 and the transmission rod system 3, and the charge measurement module connected to the sensitive area 53 of the cross-shaped thin film sample 5, can synchronously and in real time acquire the mechanical response signals (such as stress, strain, and strain rate) and electrical response signals (such as charge and voltage) of the sample under complex stress conditions with high strain rates. Based on these synchronously acquired data, the electromechanical coupling characteristics and piezoelectric coefficient of the thin film element under dynamic biaxial tension can be accurately characterized and calibrated, providing a reliable device and methodological basis for evaluating and optimizing the dynamic performance of such piezoelectric elements.

[0041] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0042] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A device for measuring the dynamic coupling piezoelectric effect of a thin-film element, characterized in that, include: The hyperbolic waveguide rod system (1) includes a merging segment (11) for receiving impacts, the merging segment (11) being connected downstream to two symmetrical and curved segments (12), each curved segment (12) extending downstream to a straight segment (13), the two straight segments (13) being orthogonally distributed in the same plane, the merging segment (11) being connected to an impact rod (6) to receive impacts from the impact rod (6); The incident rod system (2) includes incident rod one (21) and incident rod two (22), which are arranged orthogonally and are respectively connected to the ends of the two straight segments (13) through the connecting part (7) to receive the compressive stress wave from the hyperbolic waveguide rod system (1) and generate tensile stress wave. The transmission rod system (3) includes transmission rod one (31) and transmission rod two (32) arranged coaxially with the incident rod one (21) and the incident rod two (22) respectively, for receiving the transmitted wave passing through the cross-shaped thin film sample (5); The cross-shaped thin film sample (5) has four clamping areas (51) and a test area (52) located in the center. The four clamping areas (51) are connected to the first incident rod (21), the second incident rod (22), the first transmission rod (31), and the second transmission rod (32) via an adapter (4). The test area (52) has a sensitive area (53) with piezoelectric effect at its center.

2. The apparatus for measuring the dynamic coupling piezoelectric effect of a thin-film element according to claim 1, characterized in that, The adapter (4) includes a shaft (41) and a sample connecting section (42). The shaft (41) is used to connect the incident rod system (2) and / or the transmission rod system (3). The sample connecting section (42) has multiple slits for fixing the sample.

3. The apparatus for measuring the dynamic coupling piezoelectric effect of a thin-film element according to claim 2, characterized in that, The number of slits on the sample connection section (42) of the adapter (4) is even, and they are symmetrically distributed on both sides of the longitudinal symmetry plane of the shaft (41) for simultaneously installing multiple cross-shaped thin film samples (5).

4. The apparatus for measuring the dynamic coupling piezoelectric effect of a thin-film element according to claim 1, characterized in that, An arc-shaped groove (14) is slidably connected to the outer side of the curved section (12). The radius of curvature of the arc-shaped groove (14) matches the radius of curvature of the curved section (12) to form a radial constraint on the curved section (12).

5. The apparatus for measuring the dynamic coupling piezoelectric effect of a thin-film element according to claim 1 or 4, characterized in that, The connecting part (7) is a pin, and the end of the straight segment (13) and the front end of the incident rod system (2) are respectively provided with connecting holes (15), which are connected by the pin.

6. The apparatus for measuring the dynamic coupling piezoelectric effect of a thin-film element according to claim 1 or 4, characterized in that, The connecting part (7) is a boss located at the front end of the incident rod system (2). The end of the straight section (13) is attached to the boss, and the connection is achieved by impacting the boss and transmitting stress waves.

7. The apparatus for measuring the dynamic coupling piezoelectric effect of a thin-film element according to claim 1, characterized in that, The sensitive area (53) of the cross-shaped thin film sample (5) is locally polarized and has upper and lower surface electrodes. The rest of the test area (52) has the same material and thickness as the sensitive area (53) but does not have piezoelectric properties.

8. The apparatus for measuring the dynamic coupling piezoelectric effect of a thin-film element according to claim 1, characterized in that, Strain gauges are attached to the rods of the incident rod system (2) and the transmission rod system (3) to measure incident wave, reflected wave and transmitted wave signals.

9. The apparatus for measuring the dynamic coupling piezoelectric effect of a thin-film element according to claim 1, characterized in that, The incident rod system (2) is made of a low-impedance material, and the transmission rod system (3) is made of a material with even lower impedance than the incident rod system (2).

10. The apparatus for measuring the dynamic coupling piezoelectric effect of a thin-film element according to claim 1, characterized in that, The length of the impact rod (6) is no more than half the length of the combined segment (11) of the hyperbolic waveguide rod system (1).

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