Low overshoot high sensitivity coupled piezoelectric effect shock wave pressure sensor

Abstract

This invention relates to the field of electronic information technology, and in particular to a low-overshoot, high-sensitivity coupled piezoelectric effect shock wave pressure sensor, comprising a piezoelectric measuring element, a plastic damping layer, a variable-thickness elastic layer, a constraint substrate, and leads; the variable-thickness elastic layer, the plastic damping layer, and the piezoelectric measuring element are sequentially bonded together from top to bottom to form a vibrating element; the constraint substrate has a blind-hole structure, with an inner step constructed around the top of the constraint substrate, and the vibrating element is embedded in the inner step to form a circumferentially fixed constraint boundary; a cylindrical deformation cavity is provided at the bottom of the inner step to provide space for the plastic flexural deformation of the vibrating element under the action of a shock wave. This invention can suppress the central inertial effect and peak overshoot phenomenon, and utilizes the high stiffness and strong plastic damping characteristics of the metal thin film to improve the sensor's frequency response and pressure measurement duration, solving the problems of insufficient measurement pulse width of the viscoelastic stiffness layer and damping layer on the descending edge of the pressure curve and electrical relaxation of the piezoelectric device.

Description

Technical Field

[0001] This invention relates to the field of pressure sensor technology, and in particular to a low overshoot, high-sensitivity coupled piezoelectric effect shock wave pressure sensor. Background Technology

[0002] In medical research on biological damage caused by blast shock waves, the measurement of shock wave pressure on the target surface is a key technology. Accurate, in-situ, and real-time measurement of shock wave pressure on the surface of organisms plays a crucial role in improving diagnostic accuracy, reliability of injury assessment, and effectiveness of rehabilitation monitoring.

[0003] In existing technologies, rigid sensors are used for shock wave measurement. However, the conformal mounting of rigid sensors on biological surfaces, impedance mismatch, and fluid-structure interaction effects on flexible target surfaces can all lead to differences in actual shock wave pressure compared to rigid interfaces. Furthermore, existing measurement techniques are costly. They still have significant limitations in acquiring time-history information about pressure on flexible target surfaces. Using effect targets that characterize shock wave intensity through the flexural deformation of low-strength metal thin films is a commonly used approach, offering advantages such as low cost and ease of multi-point deployment. However, these effect targets can only indicate the peak value of the shock wave and cannot obtain information about the shock wave loading process. Moreover, they cannot obtain impulse information, which is more meaningful for characterizing shock wave damage, through pressure curve integration.

[0004] Therefore, this application designs a low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a low overshoot, high-sensitivity coupled piezoelectric effect shock wave pressure sensor to solve the problems of high overshoot and low pulse width in the current coupled piezoelectric effect sensors when measuring explosion shock waves, and to achieve high-precision and high-stability measurement of low-amplitude shock waves.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides a low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor, comprising a piezoelectric measuring element, a plastic damping layer, a variable thickness elastic layer, a constraint substrate, and leads; The variable thickness elastic layer, the plastic damping layer, and the piezoelectric measuring element are bonded together sequentially from top to bottom to form a vibration element; The constraint base is a blind hole structure, and an inner step is constructed around the top of the constraint base along the inner ring. The vibration element is embedded in the inner step to form a circumferential fixed constraint boundary. The bottom of the inner step is provided with a cylindrical deformation cavity, which provides space for the plastic flexural deformation of the vibration element under the action of shock wave.

[0007] Preferably, the piezoelectric measuring element includes two symmetrically arranged insulating encapsulation films, with a piezoelectric polymer film disposed between the two insulating encapsulation films; a piezoelectric sensitive region with piezoelectric properties is disposed within the piezoelectric polymer film, and metal electrodes are covered on both sides of the piezoelectric sensitive region; the amount of charge generated by the piezoelectric sensitive region during the deformation of the piezoelectric polymer film is output to an external circuit through the metal electrodes.

[0008] Preferably, the piezoelectric sensitive region is only located at the center of the piezoelectric polymer film, and the remaining areas of the piezoelectric polymer film do not have piezoelectric properties.

[0009] Preferably, the plastic damping layer is a low-strength metal with high modulus, linear elasticity, and ideal plastic mechanical properties, which has both stiffness and damping regulating effects.

[0010] Preferably, the variable thickness elastic layer is a composite material with viscoelastic mechanical properties, which regulates the high-frequency oscillation of the vibration element under impact load through viscoelastic mechanical response.

[0011] Preferably, the variable thickness elastic layer is recessed from the periphery to the center, with a thickness of 0.4-0.8 mm at the boundary and 0-0.2 mm in the central region. By gradually decreasing the thickness from the edge to the center, the inertial effect in the central region of the vibrating element is reduced, thereby suppressing peak overshoot during pressure measurement.

[0012] Preferably, the diameter of the deformation cavity is 4-10 mm, and the depth of the deformation cavity is not less than twice the maximum deformation deflection of the vibration element.

[0013] Preferably, the radius of the piezoelectric sensitive region is less than 0.578 times the radius of the deformation cavity.

[0014] Preferably, the electrode is divided into positive and negative electrodes, and the electrode extends out of the piezoelectric polymer film and is electrically connected to the lead wire.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: The present invention discloses a low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor. Its core technical solution is to use a piezoelectric measuring element, a plastic damping layer, a variable thickness elastic layer, a constraint substrate, and a lead wire as all necessary components. The variable thickness elastic layer, the plastic damping layer, and the piezoelectric measuring element are tightly bonded together in a top-to-bottom order to form an integrated vibration element for sensing shock wave pressure and completing mechanical deformation and force-electric conversion. At the same time, the constraint substrate is designed as a blind hole structure. A continuous inner step is set on the inner circumferential side of the top of the constraint substrate. The above-mentioned stacked vibration element is embedded and fixed inside the inner step. The limiting and clamping effect of the inner step forms a circumferential fixed constraint boundary for the vibration element. A cylindrical deformation cavity is opened at the bottom of the inner step to provide sufficient accommodation space and deformation freedom for the vibration element to undergo controllable plastic flexural deformation when subjected to shock wave load. This technical solution, through the complete configuration of five essential components and a top-down laminated bonding structure, ensures continuous and stable transmission of mechanical response deformation. It can efficiently convert out-of-plane shock wave pressure into the flexural deformation of the vibrating element, providing a reliable mechanical basis for subsequent force-electric coupling conversion. A low-strength metal film is used as a damping layer, which can generate plastic deformation instantly upon impact and dissipate its energy during the impact loading process. Its plastic bending deformation can better maintain the force-electric output efficiency of the piezoelectric element during the pressure unloading phase, thereby extending the measurement time. The plastic damping, in conjunction with the viscoelastic damping characteristics of the elastic layer, jointly suppresses high-frequency vibration of the element under impact load. The design employs a blind-hole constrained substrate and a circumferentially stepped embedded support, which precisely defines the mechanical boundary conditions of the vibration element. This avoids interference from the deformation of the target surface on the piezoelectric element's own electromechanical response, ensuring a stable and quantifiable correspondence between pressure and deformation, and improving measurement consistency and accuracy. The cylindrical deformation cavity at the bottom of the inner step provides sufficient deformation margin, preventing rigid collisions or compression constraints between the vibration element and the constrained substrate during plastic deflection. This ensures smooth and controllable deformation throughout the process, providing a structural basis for the plastic damping layer to exert its energy dissipation and overshoot suppression effects. It also allows the piezoelectric measuring element to output a stable charge signal synchronously with deformation. From a structural perspective, this lays the necessary foundation for the sensor to achieve overall performance of low overshoot, high sensitivity, wide measurement pulse width, and high frequency response, adapting to the precise in-situ measurement requirements of low-amplitude explosive shock waves on flexible target surfaces. Attached Figure Description

[0016] 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 described 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. In the drawings: Figure 1 This is a schematic diagram of the low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor of the present invention; Figure 2 This is a schematic diagram of the piezoelectric measuring element of the present invention; Figure 3 For the present invention Figure 2 Enlarged diagram of A in the middle; Figure 4 This is a schematic diagram of the structure of the constraint substrate of the present invention; Figure 5 This is a comparison graph of the shock wave curves of the sensor and the control group of the present invention; In the figure: 1. Piezoelectric measuring element; 2. Plastic damping layer; 3. Variable thickness elastic layer; 4. Constraint substrate; 5. Lead wire; 101. Piezoelectric polymer film; 102. Insulating encapsulation film; 103. Piezoelectric sensitive area; 104. Electrode; 401. Inner step; 402. Deformation cavity. Detailed Implementation

[0017] 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.

[0018] Existing diaphragm-type shock wave effect targets, through optimized adjustments to the metal thin film, exhibit high frequency response, and a clear linear relationship between the maximum deflection after deformation and the shock wave intensity. Furthermore, the low-strength metal thin film undergoes plastic deformation instantaneously upon impact. During bending deformation, this plastic deformation further dissipates its energy during the impact loading process, providing a good plastic damping effect on the structural deformation, thus effectively suppressing overshoot deformation. To achieve highly sensitive measurement of low-intensity shock waves on object surfaces, Chinese Patent Publication No. CN113432772A discloses a highly sensitive thin-film sensor for measuring shock waves on object surfaces and its fabrication method. By circumferentially fixing and constraining the flexible PVDF sensor, the out-of-plane shock wave pressure is converted into in-plane tensile stress, generating a higher electromechanical coupling effect. Furthermore, by constraining the substrate to isolate the deformation-induced effects on the flexible target surface, more accurate shock wave time history information of the target surface can be obtained. This coupled piezoelectric sensor, which uses both d31 and d32 piezoelectric modes, can generate extremely high charge output under relatively low shock wave conditions. By optimizing the damping layer configuration, the sensor's frequency response, range, and sensitivity can be adjusted. However, this type of sensor still suffers from large peak overshoot and short measurement pulse width. The reason for this is that both the fiber polymer damping layer and the PVDF pressure gauge stacked measuring element used in this technology exhibit significant nonlinear elastic characteristics. Insufficient stiffness, high inertia, and nonlinear mechanical response of the measuring element collectively lead to the aforementioned problems. Furthermore, the transient loading of a shock wave easily causes localized high-frequency oscillations in the vibrating element. The ultra-high frequency response (GHz) of the piezoelectric film generates a sensitive electrical signal output to such high-frequency oscillations, resulting in high-frequency oscillations in the pressure measurement curve. Damping media are generally used to suppress these high-frequency oscillations. However, using viscoelastic damping alone can easily lead to a rapid decrease in charge output during the pressure unloading stage, which is mainly related to the relaxation mechanical properties of viscoelastic materials. Therefore, this invention incorporates plastic damping, which maintains the electromechanical response output of the piezoelectric element through the plastic bending deformation of the damping layer during the unloading stage, thereby extending its measurement time during the pressure unloading stage.

[0019] 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.

[0020] Reference Figures 1 to 4 As shown, this embodiment provides a low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor, including a piezoelectric measuring element 1, a plastic damping layer 2, a variable thickness elastic layer 3, a constraint substrate 4, and a lead wire 5; A vibrating element is formed by bonding a variable thickness elastic layer 3, a plastic damping layer 2, and a piezoelectric measuring element 1 sequentially from top to bottom. The constraint base 4 is a blind hole structure. An inner step 401 is constructed around the top of the constraint base 4. The vibration element is embedded in the inner step 401 to form a circumferential fixed constraint boundary. The bottom of the inner step 401 is provided with a cylindrical deformation cavity 402, which provides space for the plastic flexural deformation of the vibrating element under the action of shock wave.

[0021] This invention discloses a low overshoot, high-sensitivity coupled piezoelectric effect shock wave pressure sensor. Its core technical solution comprises a piezoelectric measuring element 1, a plastic damping layer 2, a variable-thickness elastic layer 3, a constraint substrate 4, and lead wires 5 as all necessary components. The variable-thickness elastic layer 3, the plastic damping layer 2, and the piezoelectric measuring element 1 are sequentially and tightly bonded together from top to bottom, forming an integrated vibration element for sensing shock wave pressure and completing mechanical deformation and force-electric conversion. Simultaneously, the constraint substrate 4 is designed as a blind-hole structure, with a continuous inner step 401 circumferentially arranged on the inner side of the top of the constraint substrate 4. The aforementioned stacked vibration element is integrally embedded and fixed inside the inner step 401. The limiting and clamping effect of the inner step 401 forms a circumferentially fixed constraint boundary for the vibration element. Furthermore, a cylindrical deformation cavity 402 is opened at the bottom of the inner step 401, providing sufficient space and deformation freedom for the vibration element to undergo controllable plastic flexural deformation under shock wave load. This technical solution, through the complete configuration of five necessary components and a top-down layered bonding structure, ensures continuous and stable mechanical transmission, efficiently converting the out-of-plane pressure of the shock wave into the overall flexural deformation of the vibrating element, providing a reliable mechanical basis for subsequent force-electric coupling conversion. The design employing a blind-hole constrained base 4 and a circumferentially inward step 401 for embedded support precisely defines the mechanical boundary conditions of the vibrating element, avoiding interference from the deformation of the target surface on the sensor's own deformation response, ensuring a stable and quantifiable correspondence between pressure and deformation, and improving measurement consistency and accuracy. The cylindrical deformation cavity 402 at the bottom of the inner step 401 can fully reserve deformation margin, preventing the vibration element from rigidly colliding with or being squeezed and restricted during plastic deflection, ensuring that the deformation is stable and controllable throughout the process. This provides a structural prerequisite for the plastic damping layer 2 to play its role in energy dissipation and overshoot suppression, and also allows the piezoelectric measuring element 1 to output a stable charge signal synchronously with the deformation. From a structural perspective, this lays the necessary foundation for the sensor to achieve overall performance of low overshoot, high sensitivity, wide measurement pulse width and high frequency response, and is suitable for the precise in-situ measurement requirements of low-amplitude explosive shock waves on the surface of flexible targets.

[0022] In one embodiment of the present invention, the working principle of the sensor provided by the present invention is as follows: the bottom of the constraint substrate 4 is attached to the surface of the object being measured by an adhesive. When a shock wave acts on the front surface of the sensor, the vibrating element undergoes downward deflection under the action of out-of-plane load. A complex bidirectional tensile stress state is generated inside the piezoelectric sensitive area of ​​the piezoelectric measuring element 1, thereby outputting a certain amount of charge. According to the first kind of piezoelectric equation, the amount of charge is linearly related to the internal stress. According to elasticity theory, there is a quantitative relationship between stress and the displacement of the thin-film piezoelectric sensor. The deflection of the element after being modulated by the plastic damping layer 2 is proportional to the shock wave pressure it senses. Therefore, it can be seen that there is a good linear relationship between the shock wave pressure and the amount of charge output by the element.

[0023] In one embodiment of the present invention, the thickness of the variable thickness elastic layer 3 increases sequentially from the center to the constraint boundary, with the thickness being the smallest in the central region and the largest in the constraint region, which can greatly reduce the central inertia of the vibration element; the plastic damping layer 2 continuously generates irreversible flexural deformation while being loaded by the shock wave, and dissipates high-frequency energy, suppressing the deformation overshoot phenomenon caused by structural inertia at the peak of the flexural deformation. This high-frequency oscillation and deformation overshoot are also the main reasons for the peak overshoot of the pressure signal output by the sensor.

[0024] In one embodiment of the present invention, the piezoelectric measuring element 1 is located at the bottom layer of the vibration element, i.e. the back of the shock wave action surface. The stress level inside the material of this layer can be further increased by the bending effect generated by the deformation of the element, so as to improve the power generation efficiency.

[0025] In one embodiment of the present invention, a three-layer composite structure consisting of a variable-thickness elastic layer 3, a plastic damping layer 2, and a piezoelectric measuring element 1 is employed. During structural response, these layers respectively function as deformation constraint, deformation response and energy dissipation, and synchronous electrical signal output of deformation information. The plastic damping layer 2 also provides stiffness and deformation regulation; for a circumferentially fixed circular thin film, its natural frequency is: Where D is the bending stiffness of the vibrating element, D = Eh³ / 12 (1–μ²), and E is the elastic modulus. The elastic modulus of the metal film used in this invention is 30-50 times that of the viscoelastic layer; therefore, the introduction of metal material can provide a higher natural frequency in the initial response stage of the shock wave. For a single-degree-of-freedom system, the relationship between the undamped natural frequency ωn and the damped natural frequency ωd is as follows: Where ζ is the viscous damping ratio, Overshoot of the vibration system As a key performance indicator in control systems and vibration analysis, the overshoot represents the maximum deviation of the system response from the steady-state value before reaching the steady-state value, and is also directly related to the damping ratio. When the system exhibits oscillatory characteristics in an underdamped state (0 < ζ < 1), its oscillation frequency is determined by the natural frequency ωn, while the overshoot amplitude is mainly controlled by the damping ratio ζ. The larger the damping ratio, the smaller the overshoot of the system response, the faster the oscillation decay rate, and the shorter the steady-state response time. Therefore, the elastic layer of this invention uses a variable thickness feature to mainly regulate the inertial effect in the central region to increase the natural frequency. In addition to the viscoelastic damping effect of the elastic layer, a metallic plastic damping is introduced. Through its deformation, it dissipates impact energy and provides strong damping, eliminating high-frequency oscillations and peak overshoot of the vibrating element.

[0026] Further optimization of the scheme: The piezoelectric measuring element includes two corresponding insulating encapsulation films 102, with a piezoelectric polymer film 101 disposed between the two insulating encapsulation films 102; a piezoelectric sensitive region 103 with piezoelectric properties is disposed within the piezoelectric polymer film 101, and metal electrodes 104 are covered on both sides of the piezoelectric sensitive region 103. The charge generated by the piezoelectric sensitive region 103 during the deformation of the piezoelectric polymer film 101 is output to the external circuit through the metal electrodes 104. The two insulating encapsulation films 102 are arranged opposite each other as insulating protective layers; the piezoelectric polymer film 101 is disposed between the two insulating encapsulation films 102 to form a stable structure; wherein the piezoelectric polymer film 101 has piezoelectric properties only in a circular area within a certain range at its center, which is the piezoelectric sensitive region, and metal electrodes 104 are covered on both sides of the piezoelectric sensitive region. The charge generated by the piezoelectric sensitive region during the deformation of the film is output to the external circuit through the electrodes 104 on both sides.

[0027] In a further optimized design, the piezoelectric sensitive region 103 is only located at the center of the piezoelectric polymer film 101, while the remaining areas of the piezoelectric polymer film 101 do not exhibit piezoelectric response. The core layer of the piezoelectric measuring element 1 is a single sheet of piezoelectric polymer film 101, rather than a composite film layer embedded in the sensitive region. The complete film core layer can better transmit the continuous tensile stress generated within the self-constrained deformation zone, thereby improving power generation efficiency. The piezoelectric sensitive region is a specific area on the piezoelectric polymer film 101, equipped with a double-sided metal electrode 104, which exhibits piezoelectric properties through local polarization technology. Meanwhile, the piezoelectric polymer film 101 in other areas does not have a piezoelectric response, thus serving as the circumferential constraint material for the sensitive region.

[0028] In one embodiment of the present invention, the piezoelectric polymer film 101 is preferably PVDF, PVDF-TrFE, PVDF-HFP and other polymer materials with piezoelectric properties, with a thickness of 0.03mm-0.05mm, and has high piezoelectric sensitivity and flexibility.

[0029] In one embodiment of the present invention, the insulating encapsulation film 102 is a polyimide film or a polyester film with a thickness of 0.02-0.03 mm. Its main function is to insulate and protect the electrode 104 and the lead 5 of the film electrode 104 in the piezoelectric sensitive area.

[0030] Further optimization of the scheme involves using a low-strength metal with high modulus, linear elasticity, and ideal plastic mechanical properties as the plastic damping layer 2. This layer combines the functions of stiffness and damping regulation. As the functional layer with the highest elastic modulus in the laminated vibration element, the plastic damping layer 2 can improve the stiffness and response frequency of the vibration element. Under the action of out-of-plane shock waves, it can generate downward plastic flexural deformation, which in turn causes the underlying piezoelectric film layer to flex, generating high horizontal in-plane tensile stress.

[0031] In one embodiment of the present invention, the plastic damping layer 2 is preferably made of annealed copper, low-alloy aluminum film, silver foil, etc., with a thickness of 0.1mm-0.6mm, which has the function of regulating both stiffness and damping.

[0032] In one embodiment of the present invention, T2 annealed copper foil is used as the plastic damping layer 2, with an elastic modulus of 100-110 GPa, a yield strength of 60-80 MPa, and an elongation of ≥30%.

[0033] In one embodiment of the present invention, considering the radius r and thickness h of the circumferentially fixed circular thin film deformation zone, the radial stress in the central region under the action of out-of-plane pressure p is: Where μ is Poisson's ratio, and the aspect ratio of a typical thin film structure is not less than 10. Therefore, the in-plane stress is 10¹-10² times the out-of-plane pressure, and plastic deformation can be initiated even under relatively low out-of-plane pressure <1MPa.

[0034] Further optimization involves using a variable-thickness elastic layer 3, a composite material with viscoelastic mechanical properties, to regulate the high-frequency oscillations generated by the plastic damping layer 2. The variable-thickness elastic layer 3 is concave from the periphery to the center, with a thickness of 0.4-0.8 mm at the boundary and 0-0.2 mm in the central region. This gradual decrease in thickness from the edge to the center reduces the inertial effect of the central piezoelectric sensitive area. The elastic modulus of the variable-thickness elastic layer 3 is typically 2-4 GPa, controlling the high-frequency oscillations generated by the plastic damping layer 2. Furthermore, the variable-thickness elastic layer 3 is designed with a gradually concave structure towards the center.

[0035] In one embodiment of the present invention, the matching combination of the variable thickness elastic layer 3 and the plastic damping layer 2 can directly regulate the amplitude-frequency response characteristics of the vibration element, including natural frequency, equivalent stiffness, equivalent modulus, flexural deformation, vibration damping and stress state, etc., and directly regulate the sensitivity, linearity, overshoot and frequency response of the sensor.

[0036] In one embodiment of the present invention, the variable thickness elastic layer 3 is made of polymer materials such as rubber, epoxy resin, polyurea, and polyurethane, and their composite materials, which have high stress wave dissipation characteristics and viscoelastic properties.

[0037] Further optimization of the scheme: the diameter of the deformation cavity 402 is 4-10mm, and the depth of the deformation cavity 402 is not less than twice the maximum deformation deflection of the vibrating element; the radius of the piezoelectric sensitive area 103 is less than 0.578 times the radius of the deformation cavity 402. The deformation cavity 402 is the deformation space of the vibrating element. This is achieved by optimizing the force-displacement response characteristics of the vibrating element. The depth of the deformation cavity 402 is more than twice the maximum deformation depth of the vibrating element to avoid measurement errors caused by limited deformation. The radius of the piezoelectric sensitive area is not greater than 0.578 times the radius of the deformation area. According to the theory of small deformation of thin plates, the in-plane strain distribution law is as follows: Where $x$ represents the distance to the center of the circle. Within the range of $x \leq 0.578r$, both radial and tangential strains are positive, indicating that the region is under tensile strain, and the piezoelectric element outputs positive charge under this influence. When $x > 0.578r$, the radial and tangential strains are in opposite directions, and the charge output of the piezoelectric element in this region is chaotic, making it unsuitable as a sensitive area. Therefore, this invention controls the radius of the piezoelectric sensitive area to be no greater than $0.578r$, which maintains the deformation-charge output relationship as positive as possible while ensuring that the piezoelectric sensitive area is always in a region of deformation and stress concentration, thus improving sensitivity.

[0038] In one embodiment of the present invention, the inner step 401 is the installation position of the vibration element, which can provide a circumferential fixed boundary area for the vibration element.

[0039] In one embodiment of the present invention, the constraint substrate 4 is made of metal, plastic or polymer.

[0040] In a further optimized design, electrode 104 is divided into positive and negative electrodes, and a piezoelectric polymer film 101 extends from electrode 104 and is electrically connected to lead wire 5. Electrode 104 is the output terminal for generating charge in the piezoelectric sensitive area, and is divided into positive and negative electrodes, which are connected to the lead wires 5 on both sides of the piezoelectric functional film by means of conductive silver paste or riveting.

[0041] In summary, the technical effects of the present invention are as follows: The coupled piezoelectric effect provided by this invention mainly utilizes the piezoelectric effect in two orthogonal directions within the plane of the piezoelectric thin film to generate an electrical signal. Through elastic theory, the deformation of the thin film under the action of a shock wave is designed to transform from the traditional out-of-plane compression form to out-of-plane flexural deformation. Even a small flexural deformation can generate a high-order stress field within the thin film layer. By reasonably controlling the vibration frequency and deflection, it is possible to ensure that the charge quantity is linearly related to the shock wave pressure. Moreover, this working mode, which requires only weak deformation to generate a large amount of charge, can improve the signal-to-noise ratio and sensitivity of the component output.

[0042] The piezoelectric polymer functional material prepared by this invention using local polarization technology has a complete and continuous structure, which improves the continuous transmission efficiency of tensile stress. The piezoelectric sensitive region is set to 0.578 times the radius of the deformation region, which facilitates the utilization of the uniform and high-level isotropic tensile properties of the central region during film flexural deformation. This avoids the problem of charge reduction caused by stress reversal at the boundary positions due to the piezoelectric sensitive material being placed throughout the entire deformation region. The uniform stress field also helps to maintain the linear characteristics of the electromechanical response.

[0043] The plastic damping layer 2 provided by this invention can extend the response time of the piezoelectric element through irreversible deformation, overcoming the problem of voltage relaxation in piezoelectric polymer materials, which are accurate in responding to high-frequency signals but prone to voltage relaxation in responding to low-frequency signals. This improves the measurement duration and pulse width of the sensor's shock wave pressure curve. The piezoelectric measuring element 1 is attached to the back of the plastic damping layer 2 and deforms synchronously with it, responding synchronously to its deformation process and converting it into a high-frequency electrical signal for output.

[0044] This invention, through multi-layer structural optimization and flexible packaging design, achieves a small overall size and facilitates conformal mounting with the target on the structural surface. The constraint substrate 4 provides circumferential constraints for the vibrating element and protects it from forced deformation under shock waves, unaffected by tensile and bending deformation of the target surface, thus ensuring a predictable quantitative relationship between pressure and deformation. The sensor provided by this invention has extremely high sensitivity, is suitable for measuring low-intensity shock waves, requires no additional power supply or complex circuitry, and features low power consumption, small size, high shock resistance, and ease of low-cost, multi-point distributed measurement.

[0045] Specific examples: like Figure 1 As shown, a low overshoot, high-sensitivity coupled piezoelectric effect shock wave pressure sensor includes a piezoelectric measuring element 1, a plastic damping layer 2, a variable-thickness elastic layer 3, a constraint substrate 4, and leads 5. The piezoelectric measuring element 1 comprises a central PVDF piezoelectric film and insulating films on both sides, such as... Figure 2As shown, the PVDF piezoelectric film has a thickness of 0.03 mm, and the central region contains a circular piezoelectric sensitive area 103 with a diameter of 5 mm. Electrodes with a thickness of 100 nm are fabricated on both sides of the sensitive area by magnetron sputtering. The insulating film on both sides is a polyimide film with a thickness of 0.03 mm.

[0046] The plastic damping layer 2 is a 0.1mm thick T2 annealed copper film. The variable thickness elastic layer 3 is made of polyurea material, with zero thickness at the center and 0.6mm at the constraint boundary. The thickness increases linearly from the center to the constraint boundary. This material has good hyperelasticity and high damping characteristics, and can be used as a constraint layer to control the degree of structural deformation. It can also work in conjunction with the plastic damping layer to regulate the response characteristics of the vibrating element under shock wave action. The constraint base 4 is made of PVC and has an internal structure with an inner step 401 and a deformation cavity 402. The outer diameter of the constraint base 4 is 18mm and the height is 5mm. The inner step 401 has a diameter of 16mm and a height of 1.5mm, and the deformation cavity 402 has a diameter of 8mm and a height of 2.5mm. Figure 4 As shown, from bottom to top, the piezoelectric measuring element 1, the plastic damping layer 2, and the variable thickness elastic layer 3 are bonded together with epoxy resin to form a laminated vibration element. The vibration element is mounted on the inner step 401 and fixed with epoxy resin adhesive.

[0047] The shock wave pressure sensor prepared in this embodiment is attached to the surface of the blind plate of the shock tube, so that it faces the planar shock wave. The shock tube generates a planar shock wave of a certain intensity to load it from the front. A standard hard shock wave pressure sensor PCB113B24 is also installed on the blind plate.

[0048] Another set of sensors prepared using a similar method to that in this embodiment was installed as a control group. The control group did not contain a plastic damping layer, and the variable thickness elastic layer was configured with a center thickness of 0.1 mm and a thickness of 0.7 mm at the constraint boundary, with the thickness increasing linearly from the center to the constraint boundary. That is, the elastic layer material was used to replace the plastic damping layer, while the thickness of the vibration element remained consistent. The remaining structural dimensions, configuration, and materials were consistent with the sensor in the embodiment.

[0049] The experimental results obtained after loading the shock tube are as follows: Figure 5As shown in the figure, the shock wave curve measured by the PCB rigid pressure sensor is relatively regular, including a steep rising edge, a gentle falling edge, and accurate pressure peak value. The control group, lacking a stiff plastic damping layer, exhibits a slower rising edge than the example, and shows significant peak overshoot and a smaller pulse width, resulting in a less accurate representation of the shock wave time history curve. The pressure curve measured by the example sensor largely suppresses pressure peak overshoot, and the pulse width is consistent with the measurement results of the standard sensor. These results demonstrate that the stacked combination element provided by this invention effectively controls the response characteristics of the vibration element, leading to better measurement results. Pressure peak value calibration shows that the sensitivity of the sensor obtained in the example is approximately 450 pC / N, which is significantly higher than that obtained by compressing the piezoelectric film out of plane (i.e., d). 33 The sensitivity coefficient (typically 17-30 pC / N) is increased by an order of magnitude in the (mode) mode, resulting in extremely high sensitivity, suitable for measuring low-intensity shock waves on flexible target surfaces.

[0050] 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.

[0051] 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 low overshoot, high-sensitivity coupled piezoelectric effect shock wave pressure sensor, characterized in that: It includes a piezoelectric measuring element (1), a plastic damping layer (2), a variable thickness elastic layer (3), a constrained substrate (4), and a lead wire (5); The variable thickness elastic layer (3), the plastic damping layer (2), and the piezoelectric measuring element (1) are bonded together from top to bottom to form a vibration element; The constraint base (4) is a blind hole structure. An inner step (401) is constructed around the top of the constraint base (4). The vibration element is embedded in the inner step (401) to form a circumferential fixed constraint boundary. The bottom of the inner step (401) is provided with a cylindrical deformation cavity (402) to provide space for the plastic flexural deformation of the vibration element under the action of shock wave.

2. The low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor according to claim 1, characterized in that: The piezoelectric measuring element includes two symmetrically arranged insulating encapsulation films (102), and a piezoelectric polymer film (101) is disposed between the two insulating encapsulation films (102); a piezoelectric sensitive region (103) with piezoelectric properties is disposed in the piezoelectric polymer film (101), and metal electrodes (104) are covered on both sides of the piezoelectric sensitive region (103). The amount of charge generated by the piezoelectric sensitive region (103) during the stretching deformation in the piezoelectric polymer film (101) is output to the external circuit through the metal electrodes (104).

3. The low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor according to claim 2, characterized in that: The piezoelectric sensitive area (103) is only located at the center of the piezoelectric polymer film (101), and the remaining locations of the piezoelectric polymer film (101) do not have piezoelectric properties.

4. The low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor according to claim 1, characterized in that: The plastic damping layer (2) is a low-strength metal with high modulus, linear elasticity, and ideal plastic mechanical properties, which has the function of regulating stiffness and damping.

5. The low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor according to claim 1, characterized in that: The variable thickness elastic layer (3) is a composite material with viscoelastic mechanical properties, and the high-frequency oscillation generated by the vibration element is controlled by the viscoelastic mechanical response.

6. The low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor according to claim 5, characterized in that: The variable thickness elastic layer (3) is recessed from the periphery to the center, with a thickness of 0.4-0.8 mm at the boundary and 0-0.2 mm in the central region. By gradually decreasing the thickness from the edge to the center, the inertial effect in the central region of the vibration element is reduced to suppress peak overshoot during pressure measurement.

7. The low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor according to claim 2, characterized in that: The diameter of the deformation cavity (402) is 4-10 mm, and the depth of the deformation cavity (402) is not less than twice the maximum deformation deflection of the vibration element.

8. The low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor according to claim 7, characterized in that: The radius of the piezoelectric sensitive region (103) is less than 0.578 times the radius of the deformable cavity (402).

9. The low overshoot, high sensitivity coupled piezoelectric effect shock wave pressure sensor according to claim 2, characterized in that: The electrode (104) is divided into positive and negative poles, and the electrode (104) extends out of the piezoelectric polymer film (101) and is electrically connected to the lead wire (5).

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