Flexible Multifunctional Sensing Network and Its Manufacturing Method

Abstract

The present invention provides a flexible multifunctional sensing network applicable to the structural health monitoring of pressure vessels and a manufacturing method thereof. The above-mentioned sensing network includes a network-shaped stretchable flexible base layer composed of a plurality of island-shaped members and a plurality of stretchable members, a guided wave signal acquisition unit including more than one flexible piezoelectric sensor, a temperature signal acquisition unit including more than one patch-type temperature sensor, and a plurality of interfaces for electrically connecting to the guided wave signal acquisition unit and the temperature signal acquisition unit respectively. Each flexible piezoelectric sensor and each patch-type temperature sensor are arranged in a distributed manner on the island-shaped members, and the collected guided wave signals and temperature signals are transmitted to a computer through the corresponding interfaces, and the wave velocity is corrected based on the temperature signals and combined with the guided wave signals for damage monitoring and positioning of the pressure vessels. The sensing network has good coupling, takes into account the influence of temperature fluctuations on guided wave signals, and can improve the accuracy and reliability of on-line diagnosis of pressure vessel damage.

Description

Technical Field

[0001] The present invention relates to the fields of guided wave signal acquisition and structural health monitoring, and particularly to a flexible multifunctional sensing network that can be used for damage monitoring and positioning of pressure vessels and a manufacturing method thereof. Background Art

[0002] Pressure vessels operating under conditions such as high pressure, high temperature, fatigue, and vibration are vulnerable to threats brought by harsh working conditions, which can exacerbate excessive deformation and cause fracture failure. Online monitoring of in-service pressure vessels can, on the one hand, promptly detect equipment damage, eliminate potential safety hazards, and reduce the likelihood of failure; on the other hand, by obtaining the dynamic development of these defects in real time, it can provide guidance for further offline detection methods, improve detection efficiency, and reduce economic losses caused by blind repair and scrapping.

[0003] As a new generation of clean energy, hydrogen has attracted the attention of many countries in the past few decades and has great application potential in the field of new energy vehicle manufacturing. However, the flammability and explosiveness of hydrogen energy pose great potential hazards during its manufacturing, storage, transportation, and use. Currently, high-pressure vessels play a crucial role in the product life cycle of hydrogen energy. Therefore, it is necessary to monitor their status in real time. For hydrogen pressure vessels, fatigue cracks may occur during long-term operation, and defects may appear due to collision impacts during transportation, which may become potential safety hazards leading to accidents.

[0004] Currently, the structural health monitoring technology based on ultrasonic guided waves is widely used for online damage diagnosis and real-time warning of pressure vessels. For example, in the prior art, patent document 1 (CN107490602A) proposes a damage real-time perception and warning system for pressure vessels, which uses piezoelectric ceramic chips to monitor pressure vessels online. However, piezoelectric ceramics are rigid materials with poor coupling with pressure vessels, high acoustic impedance, and are prone to failure scenarios such as brittle fracture and debonding during use, which will have an adverse impact on the long-term monitoring of the structural health status of pressure vessels. At the same time, the above monitoring method ignores the adverse effects of temperature changes during the use of pressure vessels on the wave velocity and amplitude disturbances of guided waves, which will reduce the accuracy and reliability of online damage diagnosis of pressure vessels.

[0005] Therefore, there is a need for a sensing network that can be used for damage positioning and monitoring of pressure vessels, which has good coupling with pressure vessels to improve the disadvantages of brittle fracture and high acoustic impedance of piezoelectric ceramic transducers, and takes into account the problem of the influence of guided wave signals on temperature fluctuations, so as to improve the accuracy and reliability of online damage diagnosis of pressure vessels. Summary of the Invention

[0006] In view of the defects existing in the above-mentioned prior art, the present invention aims to provide a flexible multifunctional sensing network applicable to the structural health monitoring of pressure vessels, which has good coupling with the pressure vessels, takes into account the influence of guided wave signals by temperature fluctuations, and can improve the accuracy and reliability of on-line diagnosis of pressure vessel damage.

[0007] The present invention also aims to provide a manufacturing method for the flexible multifunctional sensing network.

[0008] The present invention includes the following technical solutions.

[0009] 〔1〕A flexible multifunctional sensing network, comprising a stretchable flexible base layer, a guided wave signal acquisition unit, a temperature signal acquisition unit, and a plurality of interfaces for electrically connecting to the guided wave signal acquisition unit and the temperature signal acquisition unit respectively.

[0010] The above-mentioned stretchable flexible base layer is in a network shape and is composed of a plurality of island-shaped members at the network nodes and a plurality of stretchable members connecting the island-shaped parts.

[0011] The above-mentioned guided wave signal acquisition unit includes more than one flexible piezoelectric sensor, and the flexible piezoelectric sensors are arranged in a distributed manner on the island-shaped members.

[0012] The above-mentioned temperature signal acquisition unit includes more than one patch-type temperature sensor, and the patch-type temperature sensors are arranged in a distributed manner on the island-shaped members.

[0013] The above-mentioned flexible piezoelectric sensors and the above-mentioned patch-type temperature sensors are respectively independently carried on the island-shaped members.

[0014] The guided wave signals collected by the guided wave signal acquisition unit and the temperature signals collected by the temperature signal acquisition unit are transmitted to a computer through the above-mentioned interfaces, the wave velocity is corrected based on the temperature signals, and combined with the guided wave signals for damage monitoring and positioning of the pressure vessel.

[0015] 〔2〕The flexible multifunctional sensing network as described in 〔1〕 above, wherein the stretchable flexible base layer is made of a double-sided copper-plated polyimide film with a thickness of 0.1 - 0.5 mm, and the island-shaped members and the stretchable members are prepared by laser engraving the double-sided copper-plated polyimide film at room temperature.

[0016] 〔3〕The flexible multifunctional sensing network as described in 〔2〕 above, wherein the copper cladding on the surfaces of part of the island-shaped members and part of the stretchable members is removed by etching treatment.

[0017] Another part of the surface of the stretchable member with a copper coating is used as a stretchable conductor member to electrically connect the above-mentioned guided wave signal acquisition unit and the above-mentioned temperature signal acquisition unit to the corresponding interfaces respectively, for transmitting the signals collected by each signal acquisition unit.

[0018] 〔4〕The flexible multi-functional sensing network according to any one of the above-mentioned 〔1〕~〔3〕, wherein the above-mentioned stretchable member is a serpentine member.

[0019] 〔5〕The flexible multi-functional sensing network according to the above-mentioned 〔1〕, wherein the above-mentioned guided wave signal acquisition unit is a piezoelectric sensor array composed of more than 2 flexible piezoelectric sensors, and the above-mentioned temperature signal acquisition unit is a temperature sensor array composed of more than 2 patch-type temperature sensors.

[0020] 〔6〕The flexible multi-functional sensing network according to the above-mentioned 〔1〕 or 〔5〕, wherein the above-mentioned flexible piezoelectric sensor is a piezoelectric thin film sensor, and the above-mentioned patch-type temperature sensor is a patch-type thin film temperature sensor.

[0021] 〔7〕The flexible multi-functional sensing network according to the above-mentioned 〔6〕, wherein the above-mentioned flexible piezoelectric sensor is a circular polyvinylidene fluoride piezoelectric film transducer, and the above-mentioned patch-type temperature sensor is a square platinum patch resistance temperature sensor.

[0022] 〔8〕The flexible multi-functional sensing network according to the above-mentioned 〔1〕, wherein,

[0023] The above-mentioned guided wave signal acquisition unit includes a first excitation terminal and a first signal receiving terminal, and the above-mentioned temperature signal acquisition unit includes a second signal receiving terminal,

[0024] The above-mentioned first excitation terminal, the first signal receiving terminal, and the above-mentioned second signal receiving terminal are respectively electrically connected to the corresponding interfaces, and each interface is arranged on a plurality of fixing components for fixing the above-mentioned flexible multi-functional sensing network.

[0025] 〔9〕The flexible multi-functional sensing network according to the above-mentioned 〔8〕, wherein the above-mentioned first excitation terminal and the above-mentioned first signal receiving terminal can be used interchangeably.

[0026] 〔10〕A manufacturing method of a flexible multi-functional sensing network, comprising the following steps:

[0027] S1: Lay the flexible double-sided copper-plated polyimide film flat on the workbench plane, then use an inkjet printer to print the pre-designed conduction path, and then let it stand until the ink solidifies. After the solidification is completed, use ferric chloride etching solution to etch away the unnecessary copper coating;

[0028] S2: Next, lay the obtained polyimide film flat on the laser working platform, and laser engrave the polyimide film according to the pre-designed program and substrate pattern to remove the unnecessary parts, forming a network-shaped stretchable flexible substrate composed of multiple island-shaped components at the network nodes and multiple stretchable components connecting the island-shaped parts. Laser processing is performed at specific positions of some of the island-shaped components to form through holes.

[0029] S3: Pour conductive silver paste into the through holes and cure it to form conductive paths.

[0030] Install a flexible piezoelectric sensor on more than 1 island-shaped component to form a guided wave signal acquisition unit, set an interface corresponding to the guided wave signal acquisition unit, and electrically connect the positive and negative electrodes of the guided wave signal acquisition unit to the corresponding interface through a stretchable component with a copper coating on its surface.

[0031] Install a patch-type temperature sensor on more than 1 island-shaped component to form a temperature signal acquisition unit, set an interface corresponding to the temperature signal acquisition unit, and electrically connect the temperature signal acquisition unit to the corresponding interface through a stretchable component with a copper coating on its surface.

[0032] Advantageous Effects

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention designs a highly integrated flexible multi-functional sensing network as a monitoring device. By stretching the network, the monitoring area and monitoring region can be effectively adjusted, enabling a single device to have good universality for pressure vessels of different shapes and sizes.

[0035] (2) Compared with the traditional guided-wave-based structural health monitoring method for pressure vessels, the present invention uses a flexible piezoelectric sensor as the guided wave signal acquisition unit, which can avoid the disadvantages of traditional piezoelectric ceramic chips, such as being prone to brittle fracture, poor conformal ability with pressure vessels, and high acoustic impedance, and improves the reliability of long-term monitoring.

[0036] (3) The present invention integrates a temperature sensor on the basis of the guided-wave-based damage diagnosis technology, taking into account the influence of the guided wave velocity disturbance and the increase in guided wave amplitude caused by temperature changes in the pressure vessel during operation, and improves the monitoring accuracy for pressure vessels under different working conditions.

[0037] Other aspects, features, and advantages of the present invention will become apparent in the following detailed description. Description of the Drawings

[0038] Figure 1 It is a schematic diagram showing the composition of the flexible multi-functional sensing network according to an embodiment of the present invention.

[0039] Figure 2 is Figure 1 A schematic diagram of the structural decomposition of the guided wave signal acquisition unit in area A of

[0040] Figure 3 is Figure 1 A schematic diagram of the structural decomposition of the temperature signal acquisition unit in area B of

[0041] Figure 4 is Figure 1 A schematic diagram of the circuit layout of the flexible multi-functional sensing network shown in

[0042] Figure 5 A tensile test diagram of the flexible multi-functional sensing network according to an embodiment of the present invention.

[0043] Figure 6 A temperature change curve graph of the pressure vessel (gas cylinder) involved in the present invention during the pressure test.

[0044] Figure 7 is a comparison graph of the damage location results before and after temperature correction of the pressure vessel involved in the present invention, where Figure 7 (A) is the damage location result before temperature correction, Figure 7 (B) is the damage location result after temperature correction. Specific embodiments

[0045] The following describes the technical features of the present invention in conjunction with preferred embodiments and accompanying drawings, which are intended to illustrate the present invention rather than limit it. The drawings are greatly simplified for illustration purposes and are not necessarily drawn to scale.

[0046] It should be understood that what is shown in the drawings is only a preferred embodiment of the present invention, which does not constitute a limitation on the scope of the present invention. Those skilled in the art can make various obvious modifications, variations, equivalent replacements to the present invention based on the embodiments shown in the drawings, and under the premise of non-contradiction, the technical features in the following described different embodiments can be combined arbitrarily, and all of these fall within the protection scope of the present invention.

[0047] 〔Flexible multi-functional sensing network〕

[0048] The following refers to Figures 1 to 4 to describe in detail the composition and features of the flexible multi-functional sensing network (hereinafter also referred to as "sensing network") of the present invention. Figure 1 is a schematic diagram of the composition of the flexible multi-functional sensing network according to an embodiment of the present invention. Figure 2 is Figure 1 A schematic diagram of the structural decomposition of the guided wave signal acquisition unit in area A of Figure 3 is Figure 1 A schematic diagram of the structural decomposition of the temperature signal acquisition unit in area B ofFigure 4 for Figure 1 Schematic diagram of the circuit layout of the flexible multifunctional sensing network shown.

[0049] The flexible multifunctional sensing network of the present invention comprises a stretchable flexible substrate layer 1, a waveguide signal acquisition unit 4, a temperature signal acquisition unit 3, and a plurality of interfaces (P1 to P20) for electrically connecting to the waveguide signal acquisition unit and the temperature signal acquisition unit, respectively.

[0050] like Figure 1 As shown in FIG. 1 , the stretchable flexible substrate layer 1 is in a network shape, and is composed of a plurality of island-shaped components 5 at the network nodes and a plurality of stretchable components 6 connecting the island-shaped parts. For ease of explanation, the sensing network is set to a 5×5 matrix format. Figure 1 The lower left corner is the origin as the coordinate axis, the horizontal direction is the X-axis direction, and the 5 columns of the sensor network are marked as x1, x2, x3, x4, and x5 from the origin. The vertical direction is the Y-axis direction, and the 5 rows of the sensor network are marked as y1, y2, y3, y4, and y5 from the origin. The island-shaped component located at the network node is marked as I (x i ,y j ), for example, the island-shaped component located in the 3rd column and the 1st row is recorded as island I (x3, y1).

[0051] In this embodiment, the sensor network is set to a 5×5 matrix, but the present invention is not limited thereto, and may be set to any matrix such as 6×6, 8×8, 10×10, 100×100, or 50×200 as needed.

[0052] A stretchable member 6 is formed between each island-shaped member to connect the island-shaped members to each other. The stretchable member is preferably a serpentine member, so that the network has excellent extensibility, and can reach more than 350% of the original length after stretching, more preferably more than 400%. Considering the strength of the sensor network and the spacing between sensors, the length of the stretchable member after stretching is preferably less than 1000% of the original length, more preferably less than 800%. There is no special limitation on the line width of the stretchable member, which can be 0.5-5mm, preferably 1-4mm, more preferably 1-3mm, and most preferably 1-2mm. The line width of the stretchable member is within the above range, which is convenient for laser processing and can ensure that the stretchable member is not easy to break when stretched. The monitoring area and monitoring area can be effectively adjusted by stretching the network, so that a device has good universality for pressure vessels of different shapes and sizes.

[0053] Figure 1 In the figure, part of the surface of the stretchable flexible substrate layer 1 is covered with a conductive copper coating 2, and the copper coating 2 is a black part, including a stretchable conductive component and an island-shaped conductive component.

[0054] In a preferred embodiment, the stretchable flexible base layer 1 is made of a double-sided copper-plated polyimide film with a thickness of 0.1 - 0.5 mm. The above-mentioned island-shaped member 5 and the above-mentioned stretchable member 6 are prepared by laser engraving the double-sided copper-plated polyimide film at room temperature. The thickness of the double-sided copper-plated polyimide film is preferably 0.2 - 0.5 mm, more preferably 0.25 - 0.4 mm. The copper cladding on the surfaces of part of the island-shaped member and part of the stretchable member is removed by etching treatment. By removing part of the copper cladding on both sides of the film, short circuits of each transmission path can be avoided. In addition, the surface of another part of the stretchable member with the copper cladding retained serves as a stretchable conductor member to electrically connect the guided wave signal acquisition unit and the temperature signal acquisition unit to the corresponding interfaces respectively, and can be used to transmit the signals collected by each signal acquisition unit.

[0055] For example, Figure 1 in, the black island-shaped members (such as Island I(x1,y5), I(x2,y3), I(x3,y2), I(x3,y4), I(x4,y3), I(x5,y3)) and the stretchable members indicate that the copper cladding remains on the surface of the members, and the white (or hollow) island-shaped members (such as Island I(x1,y1), I(x1,y2), I(x5,y4), etc.) and the stretchable members indicate that the copper cladding on the surface of the members has been removed. In addition, the gray-shaded island-shaped members (such as Island I(x2,y2), I(x3,y3), etc.) indicate that a guided wave signal acquisition unit or a temperature signal acquisition unit is carried on the island-shaped member.

[0056] In addition, according to the requirements of the circuit layout, it is preferred to form through holes at specific parts of part of the island-shaped members by laser processing, and conductive silver paste is poured into the through holes to electrically connect the copper cladding on the front and back sides of the island-shaped members.

[0057] In the flexible multifunctional sensing network of the present invention, the guided wave signal acquisition unit includes more than one flexible piezoelectric sensor, and the flexible piezoelectric sensors are arranged in a distributed manner on the island-shaped members. The guided wave signal acquisition unit is preferably a piezoelectric sensor array composed of more than 2 flexible piezoelectric sensors. For example Figure 1 in, patch-type temperature sensors are respectively arranged on Island I(x1,y4), I(x3,y1), I(x3,y3), I(x5,y2) to form an array of patch-type temperature sensors.

[0058] In addition, in the flexible multifunctional sensing network of the present invention, the temperature signal acquisition unit includes more than one patch-type temperature sensor, and the patch-type temperature sensors are arranged in a distributed manner on the island-shaped members. The temperature signal acquisition unit is preferably a temperature sensor array composed of more than 2 patch-type temperature sensors. For example Figure 1In it, flexible piezoelectric sensors are respectively arranged on islands I(x2, y2), I(x2, y4), I(x4, y2), and I(x4, y4) to form an array of flexible piezoelectric sensors.

[0059] In the flexible multi-functional sensing network of the present invention, the above-mentioned flexible piezoelectric sensors and the above-mentioned patch-type temperature sensors are respectively carried on island-shaped members independently. The shape and size of the island-shaped members are preferably adapted to the flexible piezoelectric sensors and the patch-type temperature sensors they carry.

[0060] In the present invention, the flexible piezoelectric sensor is a flexible sensor based on the piezoelectric effect, which is a self-powered and electromechanical conversion sensor for damage diagnosis and location. As the flexible piezoelectric sensor, a piezoelectric thin film sensor is preferably used, and a circular polyvinylidene fluoride (PVDF) piezoelectric thin film transducer is particularly preferably used. The piezoelectric thin film sensor has the characteristics of being thin, light in weight, and very flexible, and has a wide frequency response, a large dynamic range, a high sensitivity of force-point conversion, and advantages such as light weight, softness without brittleness, and impact resistance. The thickness of the flexible piezoelectric sensor is 0.05 - 0.5 mm, preferably 0.1 - 0.4 mm, and more preferably 0.2 - 0.3 mm. There is no particular limitation on the shape of the flexible piezoelectric sensor, which can be circular, square, hexagonal, etc., and preferably circular. Figure 1 In the shown sensing network, circular flexible piezoelectric sensors are used. There is no particular limitation on the size of the flexible piezoelectric sensor, which can be selected according to needs. For example, when using a circular flexible piezoelectric sensor, its diameter can be 5 - 10 mm.

[0061] By using the flexible piezoelectric sensor as the guided wave signal acquisition unit, it is possible to avoid the disadvantages of traditional piezoelectric ceramic sheets, such as being easily brittle, poor conformal ability with pressure vessels, and high acoustic impedance, and improve the reliability of long-term monitoring.

[0062] In addition, in the present invention, the patch-type temperature sensor is used for collecting temperature signals. The patch-type temperature sensor has the characteristics of high measurement accuracy and fast response speed when used for measuring the surface temperature of an object. As the patch-type temperature sensor, a patch-type thin film temperature sensor is preferably used, and a platinum patch resistance temperature sensor is more preferably used. The platinum patch resistance temperature sensor has the advantages of high accuracy, good stability, and a wide application temperature range. There is no particular limitation on the thickness of the patch-type temperature sensor, which can be 0.05 - 3 mm, preferably 0.1 - 1 mm. There is no particular limitation on the shape of the patch-type temperature sensor, which can be circular, square, hexagonal, etc., and preferably square. Figure 1 In the shown sensing network, square patch-type temperature sensors are used. There is no particular limitation on the size of the patch-type temperature sensor, which can be selected according to needs. For example, when using a square patch-type temperature sensor, its side length can be 5 - 12 mm, preferably 8 - 10 mm.

[0063] The flexible piezoelectric sensor preferably includes a first excitation terminal and a first signal receiving terminal. The first excitation terminal is electrically connected to a corresponding interface to excite the piezoelectric sensor, and the first signal receiving terminal is connected to a corresponding interface and conveys the piezoelectric signal to a computer through a port and a circuit. In the present invention, the first excitation terminal and the first signal receiving terminal can be used interchangeably.

[0064] The temperature signal acquisition unit preferably includes a second signal receiving terminal for electrically connecting to a corresponding interface and conveying the received temperature signal to a computer.

[0065] In some preferred embodiments, the respective interfaces (P1 to P20) corresponding to the first excitation terminal, the first signal receiving terminal, and the second signal receiving terminal are provided on a plurality of fixed components of the flexible multifunctional sensing network. The fixed components are used to mount and fix the flexible multifunctional sensing network on a pressure vessel. For ease of explanation, the fixed components use marking symbols corresponding to the respective interfaces (P1 to P20).

[0066] The sensing network of the present invention conveys the guided wave signal collected by the guided wave signal acquisition unit and the temperature signal collected by the temperature signal acquisition unit to a computer through a plurality of interfaces, corrects the wave velocity based on the temperature signal, and combines it with the above-mentioned guided wave signal for damage monitoring and positioning of the pressure vessel.

[0067] The following combines Figures 2 to 3 to further illustrate the connection and working mode of each component unit of the sensing network of the preferred embodiment of the present invention.

[0068] Figure 2 Shows Figure 1 a schematic exploded view of the structure of the guided wave signal acquisition unit in area A. Area A includes island I(x2,y2), island I(x2,y1), and a stretchable member connecting the two islands. Among them, a circular PVDF piezoelectric film transducer (hereinafter also simply referred to as PVDF piezoelectric film) is carried on island I(x2,y2). From Figure 2 it can be seen that the fronts of island I(x2,y1) and the stretchable member are white, indicating that the copper cladding on the front of the copper-clad polyimide film 11 has been removed, but the copper cladding 12 remains on the back of the copper-clad polyimide film 11 for electrical connection to the PVDF piezoelectric film and transmission of electrical signals.

[0069] The guided wave signal acquisition unit as a whole presents a stacked structure, sandwiched between two layers of copper-clad polyimide films 11, and is formed by bonding the upper and lower sides of the PVDF piezoelectric film 14 to the copper-clad layer 12 on the copper-clad polyimide film 11 through a z-axis conductive tape layer 13 with a thickness of 10 - 30 μm respectively, thereby achieving electrical connection and mechanical connection. The electrical signal is transmitted from island I(x2,y1) to the positive electrode of the PVDF piezoelectric film 14 at island I(x2,y2) via a stretchable member. Island I(x2,y1) is formed by closely fitting the copper-clad layers 12 of the two layers of copper-clad polyimide 11 through a z-axis conductive tape, thereby achieving electrical connection and mechanical connection, and outputting the piezoelectric signal collected from the PVDF piezoelectric film to the corresponding interface.

[0070] Figure 3 For Figure 1 Figure 6 is a schematic diagram of the structural decomposition of the temperature signal acquisition unit in region B. Region B includes island I(x3,y1) and the stretchable members connected to its two sides. The upper part in the figure is the front side of island I(x3,y1), the lower part is the back side of island I(x3,y1), and the middle part is the structural decomposition diagram of the temperature signal acquisition unit. Figure 3 In the island-shaped member and the stretchable member in Figure 7, the white part indicates that the copper cladding on the surface of the copper-clad polyimide film 21 has been removed, and the black part indicates that the copper cladding 22 on the surface of the copper-clad polyimide film 21 remains as a wire.

[0071] At a specific part of island I(x3,y1), a through-hole 23 with a diameter of about 1 - 2 mm is formed by laser processing. Conductive silver paste 24 is poured into the through-hole 23 to form a conductive path that conducts the copper cladding layers on both sides of the copper-clad polyimide film. A surface-mounted temperature sensor 25 for collecting temperature signals is carried on island I(x3,y1). As Figure 3 shown in the structural decomposition diagram of Figure 8, the positive electrode 26 and the negative electrode 27 of the surface-mounted temperature sensor are bonded to the copper-clad layer of the copper-clad polyimide film through a z-axis conductive tape 28. The negative electrode is conducted to the copper cladding layer on the other side of the copper-clad polyimide film through the conductive path of the through-hole part, forming a conductive path. Electrical signals are transmitted to the surface-mounted temperature sensor through the positive electrode and the negative electrode of the surface-mounted temperature sensor, and the collected temperature signals are transmitted to the corresponding interface.

[0072] The following refers to Figure 4 to describe the circuit layout of the flexible multi-functional sensing network according to the preferred embodiment of the present invention.

[0073] In the flexible multi-functional sensing network of the present invention, the temperature signal acquisition unit 3 and the guided wave signal acquisition unit 4 are distributed on a plurality of island-shaped components, and the island-shaped components are interconnected with each other through stretchable components. The temperature signal acquisition unit 3 and the guided wave signal acquisition unit 4 are connected to the outside (such as a computer) through corresponding interfaces (P1 to P20). After being stretched, the sensing network is arranged on the surface of the pressure vessel through the fixing components at the interfaces. Figure 4 Among them, the gray line is the back-wiring of the sensing network, the black line is the front-wiring, and the node where the black and gray intersect is the intersection electrically connected through the conductive silver paste passing through the through-hole.

[0074] During the acquisition of temperature signals and guided wave signals, the current flows in from the signal input terminal, passes through the temperature acquisition unit (patch temperature sensor) and the guided wave acquisition unit (flexible piezoelectric sensor), and then flows out from the negative electrode of the circuit. The circuit layout is flexibly designed according to the number of sensors and the installation positions, Figure 4 Taking the multi-functional sensing network of the 5×5 matrix shown as an example, the preferred layout of the circuit paths of each signal acquisition unit is described.

[0075] Since all sensors of the same type are connected with a common negative electrode, the potential of the entire negative electrode surface is the same and can be regarded as a common ground. The common ground of the temperature sensors is I(x1,y3)-I(x1,y2)-I(x1,y1)-I(x2,y1)-I(x3,y1)-I(x4,y1)-I(x5,y1), and this entire common ground path is named Gt. The common ground of the piezoelectric sensors is I(x2,y4)-I(x3,y4)-I(x4,y4)-I(x4,y3)-I(x4,y2)-I(x3,y2)-I(x2,y2)-I(x2,y3)-I(x5,y3), and this entire common ground path is named Gg.

[0076] The circuit layouts of each temperature sensor (T1 to T5) are as follows:

[0077] T1: 7→P15→I(x1,y5)→T1→Gt→P5→10

[0078] T2: 7→P13→I(x3,y5)→I(x3,y4)→T2→Gt→P5→10

[0079] T3: 7→P7→T3→Gt→P5→10

[0080] T4: 7→P3→T4→Gt→P5→10

[0081] The circuit layouts of each piezoelectric sensor (PT1 to PT5) are as follows:

[0082] PT1: 8 → P14 → I(x2, y5) → PT1 → Gg → P8 → 9

[0083] PT2: 8 → P12 → I(x4, y5) → PT2 → Gg → P8 → 9

[0084] PT3: 8 → P4 → I(x4, y1) → PT3 → Gg → P8 → 9

[0085] PT4: 8 → P2 → I(x2, y1) → PT4 → Gg → P8 → 9

[0086] The circuit layout of each sensor of the temperature signal acquisition unit and the guided wave signal acquisition unit described above is only a preferred embodiment, and the present invention is not limited thereto. On the premise of being able to realize the operation of the sensor and signal acquisition and transmission, those of ordinary skill in the art can make any changes and combinations according to actual needs.

[0087] 〔Manufacturing Method of Flexible Multifunctional Sensing Network〕

[0088] The preferred flexible multifunctional sensing network of the present invention can be manufactured by the following method.

[0089] Lay the flexible double-sided copper-clad polyimide film flat on the workbench plane. Then, print the pre-designed conductive path using an inkjet printer, and then let it stand still until the ink cures. After the curing is completed, use ferric chloride etching solution to etch away the unnecessary copper cladding (step S1). In this step, the curing temperature is preferably room temperature, the curing time is preferably 12 - 24 hours, and the etching time is preferably 5 minutes - 20 minutes.

[0090] Next, lay the obtained polyimide film on the laser working platform, and laser engrave the polyimide film according to the pre-designed program and substrate pattern to remove the unnecessary parts, forming a network-shaped stretchable flexible substrate composed of multiple island-shaped members at the network nodes and multiple stretchable members connecting the island-shaped parts. Laser process specific positions on some of the island-shaped members to form through holes (step S2). In this step, the stretchable members are preferably processed into serpentine members. In addition, it is preferably further to spray an insulating material on the surfaces of the island-shaped members and stretchable members with a copper cladding on the surface for electromagnetic protection. As the insulating material, insulating materials such as silicone three-proof glue are preferably used.

[0091] Next, pour conductive silver paste into the through-holes and cure it to form conductive paths; install flexible piezoelectric sensors on more than 1 island-shaped component to form a guided wave signal acquisition unit, set an interface corresponding to the guided wave signal acquisition unit, and electrically connect the positive and negative electrodes of the guided wave signal acquisition unit to the corresponding interface through a stretchable component with a copper coating on its surface; install patch-type temperature sensors on more than 1 island-shaped component to form a temperature signal acquisition unit, set an interface corresponding to the temperature signal acquisition unit, and electrically connect the temperature signal acquisition unit to the corresponding interface through a stretchable component with a copper coating on its surface (step S3). In this step, the curing conditions of the conductive silver paste are preferably curing at 100-150 °C for 5 minutes to 8 hours. In addition, it is preferred to bond the flexible piezoelectric sensor and the patch-type temperature sensor to the island-shaped component through a z-axis conductive tape to achieve electrical conduction and mechanical connection. In addition, as the flexible piezoelectric sensor, a PVDF piezoelectric film transducer is preferably used, and as the patch-type temperature sensor, a platinum patch resistance temperature sensor is preferably used.

[0092] Embodiment

[0093] The constitution and advantages of the present invention are further described below through embodiments. It should be understood that the following embodiments are only illustrative of the implementation of the present invention and are not intended to limit the protection scope of the present invention.

[0094] (Manufacture of Flexible Multifunctional Sensing Network)

[0095] Lay a flexible double-sided copper-plated polyimide film with a thickness of 0.25 mm flat on the workbench plane. Then, print a pre-designed conductive path using an inkjet printer, and then let it stand at room temperature for 12 hours to cure the ink. After curing is completed, etch for 10 minutes using a ferric chloride etching solution (20% by mass ferric chloride-aqueous solution) to remove the unnecessary copper coating.

[0096] Next, lay the obtained polyimide film flat on a laser working platform (Stone MMEPU-355-5, Tianjin Meiman Laser Technology Co., Ltd.), and perform laser engraving (laser power 5w, laser spot size 25 μm, engraving rate 10 mm / s) on the polyimide film according to the pre-designed program and substrate pattern to remove the unnecessary parts, forming Figure 1 a 5×5 array sensing network composed of multiple island-shaped components at the network nodes and multiple stretchable components connecting the island-shaped parts as shown. The stretchable component is formed into a serpentine structure with a line width of 1 mm, and laser processing is performed at specific positions of some island-shaped components to form through-holes with a pore diameter of 1 mm. Further, spray silicone three-proof glue as an insulating material on the surfaces of the island-shaped components and stretchable components with a copper coating on their surfaces for electromagnetic protection.

[0097] Next, the through holes are filled with conductive silver paste (SINWE 3701) and cured at 150 °C for 5 minutes to form conductive paths; square platinum patch resistive temperature sensors (side length 10 mm, thickness 0.1 mm, initial resistance at 25 °C is 100 Ω) are bonded and installed on the 4 island components respectively using z-axis anisotropic conductive tapes to form a temperature sensor array; circular PVDF piezoelectric film piezoelectric transducers (thickness 0.2 mm, diameter 9 mm, sampling center frequency is 200 kHz) are bonded and installed on the 4 island components respectively using z-axis anisotropic conductive tapes to form an array of piezoelectric film piezoelectric transducers, and the specific layout is as Figure 1 shown. Interfaces corresponding to the above temperature sensors and piezoelectric film piezoelectric transducers are set, so that the stretchable serpentine component with a copper coating on the surface is electrically connected to the corresponding interfaces, and each sensor is connected according to the Figure 4 circuit layout shown.

[0098] (Tensile test of flexible multifunctional sensing network)

[0099] The serpentine structure part of the flexible multifunctional sensing network prepared as above is fixed to an upper limit tensile testing machine (ESM750S, Mark-10, USA) for uniaxial tensile experiments, and the force-length data as shown in Figure 5 are obtained. It can be seen from Figure 5 that when the length of the serpentine structure is stretched to 390% of its original length, the force changes sharply, indicating that the serpentine structure breaks at this time. That is, the serpentine structure part has a high extensibility that can be stretched to 390% of its original length. It can be known that the flexible multifunctional sensing network of the present invention can flexibly adjust the monitoring area and region, has excellent extensibility, and has good universality for pressure vessels of different shapes and sizes.

[0100] (Temperature change during the charging and discharging process of a pressure vessel)

[0101] The prepared flexible multifunctional sensing network is stretched and arranged on the surface of a gas cylinder (pressure vessel). The temperature signals of each platinum patch resistive temperature sensor are collected through a multi-channel data acquisition card. The input port 7 and output port 10 of the temperature sensor are respectively connected to the multi-channel data acquisition card NI-9273 (National Instruments, USA). For the output port and input port, the sampling voltage is set to 1 v, the sampling frequency is 20 Hz, the multi-channel current signals are automatically collected and the data is exported to a computer for recording. The temperature signals of the gas cylinder during the pressure boosting process are collected, and the pressure boosting parameters are an inflation speed of 0.8 Mpa / s, a deflation speed of 10 Mpa / s, a peak pressure of 20 Mpa, and a peak holding time of 0 s. The temperature acquisition results are as shown in Figure 6 and demonstrate the temperature acquisition ability of the temperature sensor array.

[0102] The principle of temperature-corrected ultrasonic guided waves is related to the propagation mechanism of ultrasonic guided waves. Guided waves are usually divided into transverse waves and longitudinal waves. The wave velocity of longitudinal waves propagating along a tubular structure is as shown in Equation (1):

[0103]

[0104] The transverse wave propagating along the tubular structure is as shown in Equation (2):

[0105]

[0106] Where E is the Young's modulus of the material; ρ is the material density; σ is the Poisson's ratio; G is the rigidity modulus. It can be seen that the guided wave velocity is related to the intrinsic properties of the material, and the Young's modulus and rigidity modulus of the material are greatly affected by temperature fluctuations. Usually, a statistical fitting method based on experiments is used to obtain the relationship between the elastic modulus and rigidity modulus of the solid with temperature, and then the wave velocity is corrected based on this relationship, which can improve the positioning accuracy.

[0107] (Damage location test based on guided waves)

[0108] After stretching the prepared flexible multi-functional sensing network to an appropriate size along the horizontal and vertical axes, it is fixed on the surface of the gas cylinder using an adhesive. And a sweep frequency experiment is carried out on the terminals of the PVDF piezoelectric transducers in the sensing network for collecting guided wave signals to obtain the center frequency and bandwidth of the guided wave signal collection terminals. In this example, the center frequency is selected as 200Khz and the bandwidth is 30db. The guided wave signal is generated by a signal generator, passes through a signal attenuator and is input to the positive electrode of the excitation terminal from input port 8, and then is received by the receiving terminal and output to the signal amplifier from output port 9, and finally the waveform is displayed on an oscilloscope to complete the single-channel guided wave signal collection. Finally, the elliptical algorithm is used for damage location imaging. The imaging result without temperature correction is as shown in Figure 7 (A). The damage location of the pressure vessel is close to the imaging location. Before correcting the wave velocity without temperature, the positioning accuracies of the horizontal and vertical coordinates are 91% and 92% respectively. In contrast, according to the collected temperature signal, the wave velocity is corrected, and the damage detection and location results are as shown in Figure 7 (B). After correction, the positioning accuracies of the horizontal and vertical coordinates are 95.2% and 96.7% respectively. It can be seen that by simultaneously setting a guided wave signal collection unit and a temperature signal collection unit including a temperature sensor in the flexible multi-functional sensing network of the present invention, considering the influence of the guided wave velocity disturbance caused by temperature changes in the pressure vessel during the working state, and correcting the guided wave velocity based on the collected temperature signal, the monitoring accuracy of damage location of the pressure vessel under different working conditions can be significantly improved.

[0109] Finally, it should be understood that the descriptions of the above embodiments and examples are illustrative in all aspects and do not constitute a limitation to the present invention. Those of ordinary skill in the art can make various improvements without creative labor within the scope not departing from the spirit of the present invention. The scope of the present invention is represented by the claims, rather than by the above embodiments or examples. In addition, the scope of the present invention includes all changes within the meaning and scope equivalent to the claims.

[0110] In addition, although the foregoing specification and associated drawings describe exemplary embodiments with respect to certain exemplary combinations of elements and / or functions, it should be understood that different combinations of elements and / or functions can be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and / or functions other than those explicitly described above are also contemplated, such as may be set forth in some of the appended claims. Although specific terms are used herein, these terms are used only in a general and descriptive sense and do not constitute a limitation to the present invention.

[0111] Industrial availability

[0112] The flexible multi-functional sensing network of the present invention has excellent tensile ductility, integrates a guided wave signal acquisition unit and a temperature signal acquisition unit, can flexibly and adjustable set the monitoring area and be integrated on the surface of a pressure vessel to achieve on-line monitoring, and has good application prospects in the field of accurate positioning of damage defects.

Claims

1. A flexible multi-functional sensing network, comprising a stretchable flexible substrate layer, a guided wave signal acquisition unit, a temperature signal acquisition unit, and a plurality of interfaces for electrically connecting to the guided wave signal acquisition unit and the temperature signal acquisition unit respectively. The stretchable flexible substrate layer is in a network shape and is composed of a plurality of island-shaped members at network nodes and a plurality of stretchable members connecting the island-shaped members. The stretchable flexible substrate layer is made of a double-sided copper-plated polyimide film with a thickness of 0.1 - 0.5 mm. The island-shaped members and the stretchable members are prepared by laser engraving the double-sided copper-plated polyimide film at room temperature. The guided wave signal acquisition unit includes more than one flexible piezoelectric sensor, and the flexible piezoelectric sensors are arranged in a distributed manner on the island-shaped members. The temperature signal acquisition unit includes more than one patch-type temperature sensor, and the patch-type temperature sensors are arranged in a distributed manner on the island-shaped members. The flexible piezoelectric sensors and the patch-type temperature sensors are respectively carried on the island-shaped members independently. The guided wave signals collected by the guided wave signal acquisition unit and the temperature signals collected by the temperature signal acquisition unit are transmitted to a computer through the interfaces. The wave velocity is corrected based on the temperature signals and combined with the guided wave signals for damage monitoring and positioning of the pressure vessel.

2. The flexible multi-functional sensing network according to claim 1, wherein Part of the copper cladding on the surfaces of some of the island-shaped members and some of the stretchable members is removed through etching treatment. The surfaces of the other part of the stretchable members with copper cladding remaining are used as stretchable conductor members to electrically connect the guided wave signal acquisition unit and the temperature signal acquisition unit to the corresponding interfaces respectively, for transmitting the signals collected by each signal acquisition unit.

3. The flexible multi-functional sensing network according to claim 1 or 2, characterized in that The stretchable members are serpentine members.

4. The flexible multi-functional sensing network according to claim 1, characterized in that The guided wave signal acquisition unit is a piezoelectric sensor array composed of more than 2 flexible piezoelectric sensors, and the temperature signal acquisition unit is a temperature sensor array composed of more than 2 patch-type temperature sensors.

5. The flexible multi-functional sensing network according to claim 1 or 4, characterized in that The flexible piezoelectric sensor is a piezoelectric thin film sensor, and the patch-type temperature sensor is a patch-type thin film temperature sensor.

6. The flexible multi-functional sensing network according to claim 5, wherein, The flexible piezoelectric sensor is a polyvinylidene fluoride piezoelectric thin film transducer, and the patch-type temperature sensor is a platinum patch resistance temperature sensor.

7. The flexible multi-functional sensing network according to claim 1, wherein the flexible piezoelectric sensor includes a first excitation terminal and a first signal receiving terminal, and the patch-type temperature sensor includes a second signal receiving terminal. The first excitation terminal, the first signal receiving terminal, and the second signal receiving terminal are respectively electrically connected to corresponding interfaces, and each interface is arranged on a plurality of fixing components for fixing the flexible multi-functional sensing network.

8. The flexible multi-functional sensing network according to claim 7, characterized in that The first excitation terminal and the first signal receiving terminal can be used interchangeably.

9. A manufacturing method of a flexible multi-functional sensing network, comprising the following steps: S1: Lay the flexible double-sided copper-plated polyimide film on the workbench plane, then print a pre-designed conductive path using an inkjet printer, and then let it stand for the ink to cure. After the curing is completed, use ferric chloride etching solution to etch away the unnecessary copper cladding. S2: Next, lay the obtained polyimide film flat on the laser working platform, and laser engrave the polyimide film according to the pre-designed program and substrate pattern to remove the unnecessary parts, forming a network-shaped stretchable flexible substrate composed of multiple island-shaped components at the network nodes and multiple stretchable components connecting the island-shaped components. Laser process specific positions on some of the island-shaped components to form through holes. S3: Pour conductive silver paste into the through holes and cure it to form conductive paths. Install a flexible piezoelectric sensor on more than 1 island-shaped component to form a guided wave signal acquisition unit, set an interface corresponding to the guided wave signal acquisition unit, and electrically connect the positive and negative electrodes of the guided wave signal acquisition unit to the corresponding interface through a stretchable component with a copper coating on its surface. Install a patch-type temperature sensor on more than 1 island-shaped component to form a temperature signal acquisition unit, set an interface corresponding to the temperature signal acquisition unit, and electrically connect the temperature signal acquisition unit to the corresponding interface through a stretchable component with a copper coating on its surface.

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