A flexible triboelectric-piezoelectric expansion joint monitoring device based on rubber waterstop

Abstract

The present invention discloses a flexible triboelectric-piezoelectric expansion joint monitoring device based on a rubber waterstop, comprising an acquisition module buried in the rubber waterstop for collecting expansion joint vibration signals, and a processing module for processing the electrical signals collected on the acquisition module; the acquisition module comprises a flexible contact layer extending from bottom to top and provided with a plurality of hollow pyramid-shaped protrusions, a rigid cone located at the lower end of the flexible contact layer and matching the plurality of hollow pyramid-shaped protrusions, a PVDF electrospun film located at the lower end of the rigid cone, a metal electrode located at one end of the PVDF electrospun film, and a flexible packaging bottom layer at the bottom. The flexible triboelectric-piezoelectric expansion joint monitoring device of the present invention, based on the cooperation of the acquisition module and the processing module, collects the vibration signal generated on the PVDF electrospun film through the acquisition module, and compares and analyzes it with the normal vibration curve through the processing module, thereby being able to provide real-time monitoring of whether the expansion joint of the bridge is damaged.

Description

Technical Field

[0001] The present invention belongs to the field of expansion joint monitoring devices, and in particular relates to a flexible triboelectric-piezoelectric expansion joint monitoring device based on a rubber waterstop. Background Art

[0002] Large bridges can deform due to thermal expansion and contraction under temperature fluctuations. To accommodate this structural deformation and prevent cracks caused by this deformation, expansion joints are typically installed every few spans. The main types of expansion joints include butt-jointed, steel plate, combined shear, modular support, and seamless. Except for seamless expansion joints, all other expansion joints incorporate rubber waterstops to prevent moisture and debris from seeping into the bridge.

[0003] Increased traffic volume, overloading, speeding, and substandard construction often lead to damage to bridge expansion joints. Due to the unique nature of bridge construction, damage to expansion joints is often not detected promptly, and regular inspections are difficult. Furthermore, bridge expansion joints are numerous and long, making inspections time-consuming and labor-intensive for workers, and manual inspections may not always accurately detect damage. Damaged expansion joints can cause height differences between the bridge decks, and this unevenness can affect vehicle safety and comfort. Failure of expansion joints can even prevent them from providing the expected expansion and contraction capacity, leading to stress concentrations in the bridge structure and accelerating its destruction.

[0004] Most existing monitoring devices are rigid devices that are connected to expansion joints and may be damaged if the expansion joints are damaged. Monitoring devices are generally exposed to the air and will oxidize with use, especially some metal parts, which will oxidize after long-term exposure to the air, thus affecting the performance of the sensor. The casing material of the sensor may be sensitive to light, and the material will age under the influence of long-term sun and wind. At the same time, bridges often cross water bodies with high humidity. When operating in a high-humidity environment, corrosion or short circuits may occur inside the monitoring device. There are also pollutants in the air, such as dust and chemicals, which may be deposited on the surface of the monitoring device or enter the interior of the device, causing the monitoring device to be damaged before the expansion joint is damaged. Existing monitoring devices often require internal or external power supply, regular maintenance, battery replacement, etc., and there is a risk of power failure due to exhaustion.

[0005] Electrospinning is an advanced fiber manufacturing process that can produce nanometer-diameter polymer fibers. PVDF fiber polymer films produced through electrospinning can transform the majority of the PVDF fiber material's crystals from the α-phase to the β-phase, thereby achieving piezoelectric properties and possessing excellent triboelectric and piezoelectric properties. However, when using PVDF for signal acquisition, both triboelectricity and piezoelectricity cannot be collected simultaneously; instead, they are collected separately based on different vibration frequencies. For example, when electrospun PVDF films are subjected to low acceleration and low vibration frequencies, the fibers rub against each other, primarily generating the triboelectric effect and a triboelectric potential difference. At higher acceleration and higher frequencies, the fibers themselves are squeezed and deformed, primarily generating the piezoelectric effect and a piezoelectric potential difference. In other words, while the film can generate electrical signals at both low and high frequency vibrations, it is not possible to simultaneously capture both triboelectric and piezoelectric properties at a single frequency. Summary of the Invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to provide a flexible triboelectric-piezoelectric expansion joint monitoring device based on a rubber waterstop, which can simultaneously obtain triboelectric and piezoelectric properties at the same frequency.

[0007] Technical solution: The present invention is a flexible triboelectric-piezoelectric expansion joint monitoring device based on a rubber waterstop, characterized in that the monitoring device includes an acquisition module buried in the rubber waterstop for collecting vibration signals of the expansion joint, and a processing module for processing the vibration signals collected by the acquisition module;

[0008] The collection module includes a flexible contact layer extending from the bottom to the top and having a plurality of hollow pyramid-shaped protrusions, a rigid cone located at the lower end of the flexible contact layer and matching the plurality of hollow pyramid-shaped protrusions, a PVDF electrospun film arranged at the lower end of the rigid cone, a metal electrode arranged at one end of the PVDF electrospun film, and a flexible packaging bottom layer arranged at the bottom end.

[0009] The present invention is based on a flexible contact layer, and is provided with a plurality of hollow pyramid-shaped protrusions extending from the bottom to the top, and a rigid cone-shaped body is correspondingly provided to be embedded with the plurality of hollow pyramid-shaped protrusions. Based on the cooperation of the two, when the rigid cone-shaped body is squeezed by the waterstop rubber, the pressure will be transmitted to the PVDF electrospinning film, so that the fibers at the bottom of the cone-shaped body are compressed and the surrounding fibers are stretched, thereby generating triboelectric and piezoelectric effects at the same time, that is, regardless of whether the vibration frequency is low or high, the triboelectric and piezoelectric properties can be monitored at the same time, and the processing module will record the transmitted vibration curve. By comparing it with the normal vibration curve, the state of the expansion joint can be judged, thereby improving the accuracy of monitoring.

[0010] Furthermore, the processing module amplifies the vibration signal collected from the acquisition module and plots a vibration curve to be analyzed. The vibration curve to be analyzed is then compared with a normal vibration curve to determine the condition of the expansion joint. Preferably, when comparing the vibration curve to be analyzed with the normal vibration curve, if the similarity between the two is less than a preset similarity threshold, the condition is determined to be normal; otherwise, the condition is determined to be abnormal.

[0011] Furthermore, the monitoring device comprises two groups of PVDF electrospun films, which are respectively arranged between the flexible packaging bottom layer and the rigid cone in a horizontal and vertical cross manner.

[0012] The two layers of PVDF electrostatic spinning films with different orientations can simultaneously output two different signals during extrusion and conduct them through metal electrodes.

[0013] Furthermore, there are two groups of metal electrodes, which are spaced apart at both ends of the PVDF electrospun film in a horizontal and vertical cross manner, and are consistent with the setting direction of the PVDF electrospun film.

[0014] Furthermore, the rigid cone of the monitoring device is embedded in the hollow pyramid-shaped protrusion of the flexible contact layer.

[0015] Furthermore, the flexible contact layer of the monitoring device is a PDMS flexible contact layer, the flexible packaging bottom layer is a PDMS flexible packaging bottom layer, and the rigid cone is an epoxy resin rigid cone.

[0016] Furthermore, the number of acquisition modules of the monitoring device is no less than four, and the flexible contact layer is provided with nine hollow pyramid-shaped protrusions in the middle, arranged in a 3×3 matrix.

[0017] Beneficial effects: Compared with the existing technology, the significant advantages of the present invention are: the flexible triboelectric-piezoelectric expansion joint monitoring device, based on the cooperation of the acquisition module and the processing module, collects the triboelectric and piezoelectric effects generated on the PVDF electrospinning film through the acquisition module, and compares and analyzes them with the normal vibration curve through the processing module, thereby providing real-time monitoring of whether the bridge expansion joint is damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the distribution of acquisition modules and their connection with processing modules of the present invention;

[0019] Figure 2 This is a schematic diagram of the installation position of the acquisition module of the present invention in the expansion joint;

[0020] Figure 3 This is a schematic diagram of the installation position of the collection module in the water stop of the present invention, that is, Figure 2 Enlarged view of part A in the middle;

[0021] Figure 4 This is a structural diagram of the acquisition module of the present invention, namely Figure 3 Enlarged view of part B in the middle. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0023] like Figures 1 to 3 As shown, the flexible triboelectric-piezoelectric expansion joint monitoring device of the present invention is used to monitor whether a bridge expansion joint assembly is damaged. It includes a data acquisition module and a processing module for processing the signals collected by the data acquisition module. The number of data acquisition modules is no less than four.

[0024] The acquisition module is a flexible device embedded in the rubber waterstop and bonded to the rubber stiffening layer. It deforms with the deformation of the rubber waterstop to collect vibration signals from the expansion joint. If a bridge expansion joint is damaged, the frequency and amplitude of its vibration will change when a vehicle passes over it. This change is particularly pronounced when the bolts securing the expansion joint become loose or fall off. This vibration change is also transmitted to the rubber waterstop. By monitoring the vibration of the rubber waterstop, the expansion joint can be monitored.

[0025] The processing module is electrically connected to the acquisition module. It collects electrical signals from the acquisition module, amplifies them, and plots a vibration curve for analysis. By comparing the analysis curve with the normal vibration curve, the expansion joint's condition is determined. If the similarity between the analysis and normal vibration curves is less than a preset similarity threshold, the joint is considered normal; otherwise, it is considered abnormal.

[0026] The acquisition module adopts a layered stacking structure, including a flexible contact layer 3 with a plurality of hollow pyramid-shaped protrusions extending from the bottom to the top, a rigid cone 4 located at the lower end of the flexible contact layer 3 and matching the plurality of hollow pyramid-shaped protrusions, a PVDF electrospun film 5 located at the lower end of the rigid cone 4, a metal electrode 6 located at one end of the PVDF electrospun film 5, and a flexible packaging bottom layer 7 located at the bottom. In order to further improve the accuracy of monitoring, the PVDF electrospun film 5 located at the lower end of the rigid cone 4 of the monitoring device can be arranged in two groups to achieve different orientations. Figure 4 As shown, a PVDF electrospinning film staggered horizontally and vertically can be set at the lower end of the rigid cone, and two groups of metal electrodes staggered horizontally and vertically can be set at both ends of the PVDF electrospinning film staggered horizontally and vertically. The metal electrodes staggered horizontally and vertically are separated by the PVDF electrospinning film, so that different orientation signals can be collected.

[0027] Furthermore, the flexible contact layer 3 of the present invention can be a PDMS flexible contact layer, and the rigid cone 4 can be an epoxy resin rigid cone. To prepare the mold, a 3D printer is used to print a pit mold and a column mold with 3×3 pits in the shape of a truncated pyramid. A PDMS solution mixture with a mass ratio of 10:1 is poured into the pit mold. The column mold is then placed on top of the solution. After curing at 70°C for 12 hours, the mixture is heated in an oven to produce the PDMS flexible contact layer. The rigid cone 4 is embedded in the PDMS flexible contact layer by pouring epoxy resin into the raised portion of the PDMS hollow pyramid and curing it at 25°C for 24 hours, so that the epoxy resin rigid cone is embedded in the upper PDMS flexible contact layer.

[0028] The longitudinal and transverse PVDF electrospun films in the intermediate layers of the present invention can be directly adhered to the PDMS flexible contact layer. The PVDF electrospun film is produced by electrospinning. The spinning material is PVDF powder, which is thoroughly stirred and dissolved in a DMF (dimethylformamide) solution using a magnetic stirrer to prepare a 15wt% PVDF solution. Its surface is covered with longitudinal and transverse metal electrodes. The PVDF electrospun film is cut into a square shape, and the longitudinal and transverse metal electrodes are cut into rectangles with a long side longer than the length of the spun film and a short side shorter than the length of the spun film. The extended portion facilitates connection to a wire. The PVDF electrospun film is slightly larger than the metal electrodes to prevent direct contact between the electrodes and short circuits. The flexible encapsulation substrate 7 can be a PDMS flexible encapsulation substrate, which can be directly encapsulated on the aforementioned PVDF electrospun film 5.

[0029] That is, the flexible triboelectric-piezoelectric expansion joint monitoring device of the present invention is based on the cooperation of the acquisition module and the processing module. The acquisition module collects the triboelectric and piezoelectric effects generated on the PVDF electrospun film, and compares and analyzes them with the normal vibration curve through the processing module, thereby providing real-time monitoring of whether the bridge expansion joint is damaged.

Claims

1. A flexible triboelectric-piezoelectric expansion joint monitoring device based on a rubber waterstop, characterized in that: The monitoring device comprises a collection module buried in the rubber water stop and used to collect vibration signals of the expansion joint, and a processing module (2) for processing the vibration signals collected by the collection module (1); The collection module (1) comprises a flexible contact layer (3) extending from the bottom to the top and provided with a plurality of hollow pyramid-shaped protrusions, a rigid cone (4) located at the lower end of the flexible contact layer (3) and matching the plurality of hollow pyramid-shaped protrusions, a PVDF electrospun film (5) located at the lower end of the rigid cone (4), a metal electrode (6) located at one end of the PVDF electrospun film (5), and a flexible packaging bottom layer (7) located at the bottom end.

2. The flexible triboelectric-piezoelectric expansion joint monitoring device based on rubber waterstop according to claim 1 is characterized in that: The processing module (2) performs gain amplification on the vibration signal collected from the acquisition module and draws a vibration curve to be analyzed, and judges the state of the expansion joint by comparing the vibration curve to be analyzed with a normal vibration curve.

3. The flexible triboelectric-piezoelectric expansion joint monitoring device based on rubber waterstop according to claim 2 is characterized in that: When comparing and analyzing the vibration curve to be analyzed with the normal vibration curve, if the similarity between the two is less than a preset similarity threshold, it is judged to be normal, otherwise it is abnormal.

4. The flexible triboelectric-piezoelectric expansion joint monitoring device based on rubber waterstop according to claim 1 is characterized in that: The PVDF electrospinning films (5) are in two groups, which are respectively arranged between the flexible packaging bottom layer (7) and the rigid cone (4) in a horizontal and vertical cross manner.

5. The flexible triboelectric-piezoelectric expansion joint monitoring device based on rubber waterstop according to claim 4 is characterized in that: The metal electrodes (6) are divided into two groups and are arranged at two ends of the PVDF electrostatic spinning film (5) in a horizontal and vertical cross-sectional manner, and are consistent with the arrangement direction of the PVDF electrostatic spinning film (5).

6. The flexible triboelectric-piezoelectric expansion joint monitoring device based on rubber waterstop according to claim 1 is characterized in that: The rigid cone (4) is embedded in the hollow pyramid-shaped protrusion of the flexible contact layer (3).

7. The flexible triboelectric-piezoelectric expansion joint monitoring device based on rubber waterstop according to claim 1 is characterized in that: The flexible contact layer (3) is a PDMS flexible contact layer, the flexible packaging bottom layer (7) is a PDMS flexible packaging bottom layer, and the rigid cone (4) is an epoxy resin rigid cone.

8. The flexible triboelectric-piezoelectric expansion joint monitoring device based on rubber waterstop according to claim 1 is characterized in that: The number of the acquisition modules (1) is no less than four, and the flexible contact layer (3) is provided with nine hollow pyramid-shaped protrusions in the middle, arranged in a 3×3 matrix.

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