CN115684355A - Flexible multifunctional sensing network and manufacturing method thereof - Google Patents
Flexible multifunctional sensing network and manufacturing method thereof Download PDFInfo
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- CN115684355A CN115684355A CN202211428603.2A CN202211428603A CN115684355A CN 115684355 A CN115684355 A CN 115684355A CN 202211428603 A CN202211428603 A CN 202211428603A CN 115684355 A CN115684355 A CN 115684355A
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Abstract
The invention provides a flexible multifunctional sensing network suitable for monitoring the structural health of a pressure container and a manufacturing method thereof, wherein the sensing network comprises a network-shaped stretchable flexible substrate layer consisting of a plurality of island-shaped members and a plurality of stretchable members, a guided wave signal acquisition unit comprising more than one flexible piezoelectric sensor, a temperature signal acquisition unit comprising more than one patch-type temperature sensor, and a plurality of interfaces which are respectively and electrically connected with the guided wave signal acquisition unit and the temperature signal acquisition unit, wherein the flexible piezoelectric sensors and the patch-type temperature sensors are distributed on the island-shaped members, the acquired guided wave signals and the temperature signals are transmitted to a computer through the corresponding interfaces, the wave velocity is corrected based on the temperature signals, and the damage monitoring and positioning of the pressure container are carried out by combining the temperature signals with the guided wave signals. The sensing network has better coupling, considers the influence of temperature fluctuation on the guided wave signal, and can improve the accuracy and reliability of online diagnosis of the damage of the pressure vessel.
Description
Technical Field
The invention relates to the field of guided wave signal acquisition and structural health monitoring, in particular to a flexible multifunctional sensing network for monitoring and positioning damage of a pressure container and a manufacturing method thereof.
Background
Pressure vessels working under the working conditions of high pressure, high temperature, fatigue, vibration and the like are easily threatened by severe working conditions to aggravate excessive deformation and cause fracture failure. On one hand, the online monitoring is carried out on the in-service pressure container, so that the damage of the equipment can be found in time, the potential safety hazard is eliminated, and the failure occurrence possibility is reduced; on the other hand, the dynamic development conditions of the defects are obtained in real time, so that guidance is provided for a more recent offline detection method, the detection efficiency is improved, and the economic loss caused by blind repair and scrapping is reduced.
Hydrogen as a new generation of clean energy attracts the attention of many countries in the past decades, and has great application potential in the field of new energy automobile manufacturing. However, the flammability and explosiveness of hydrogen energy sources pose significant concerns in their manufacture, storage, transportation and use. At present, high pressure vessels play a crucial role in the product life cycle of hydrogen energy sources, and therefore their status must be monitored in real time. For a hydrogen pressure container, fatigue cracks may be generated under the long-time working condition, and the hydrogen pressure container may face collision and impact to generate defects in the transportation process and may become a potential safety hazard which causes accidents.
At present, the structural health monitoring technology based on ultrasonic guided waves is widely applied to damage online diagnosis and real-time early warning of pressure vessels, for example, patent document 1 (CN 107490602A) in the prior art proposes a damage real-time sensing and early warning system for pressure vessels, and the method adopts piezoelectric ceramic sheets to perform online monitoring on the pressure vessels. However, the piezoelectric ceramic is a rigid material, has poor coupling with the pressure vessel and high acoustic impedance, and is easy to have failure situations such as brittle fracture, degumming and the like in the use process, which brings adverse effects on long-term monitoring of the structural health state of the pressure vessel. Meanwhile, the monitoring means ignores the adverse effects that the temperature change in the use process of the pressure vessel can introduce wave velocity disturbance, amplitude disturbance and the like to the guided wave, so that the accuracy and reliability of online diagnosis of the damage of the pressure vessel can be reduced.
Therefore, a sensing network for performing damage location monitoring on a pressure vessel is required, which has better coupling performance with the pressure vessel to improve the defects of fragility and high acoustic impedance of a piezoelectric ceramic transducer, and considers the problem that a guided wave signal is influenced by temperature fluctuation, so as to improve the accuracy and reliability of online diagnosis of damage of the pressure vessel.
Disclosure of Invention
In view of the above-mentioned drawbacks in the prior art, the present invention provides a flexible multifunctional sensor network suitable for monitoring the structural health of a pressure vessel, which has better coupling with the pressure vessel, considers the influence of temperature fluctuation on the guided wave signal, and can improve the accuracy and reliability of online diagnosis of damage to the pressure vessel.
It is also an object of the present invention to provide a method of manufacturing a flexible multifunctional sensor network.
The invention comprises the following technical scheme.
The flexible multifunctional sensing network includes a stretchable flexible substrate layer, a guided wave signal acquisition unit, a temperature signal acquisition unit, and a plurality of interfaces for electrically connecting the guided wave signal acquisition unit and the temperature signal acquisition unit,
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 portions,
the guided wave signal acquisition unit comprises more than one flexible piezoelectric sensor which is distributed on the island-shaped member,
the temperature signal acquisition unit comprises more than one patch type temperature sensor which is distributed on the island-shaped component,
the flexible piezoelectric sensor and the patch type temperature sensor are respectively and independently carried on the island-shaped member,
and transmitting the guided wave signals collected by the guided wave signal collecting unit and the temperature signals collected by the temperature signal collecting unit to a computer through the interface, correcting the wave velocity based on the temperature signals, and combining the corrected wave velocity with the guided wave signals to monitor and position the damage of the pressure container.
The flexible multifunctional sensor network according to the above [ 1 ], wherein the stretchable flexible substrate layer is made of a double-sided copper-plated polyimide film having a thickness of 0.1 to 0.5mm, and the island-shaped member and the stretchable member are prepared by laser engraving the double-sided copper-plated polyimide film at room temperature.
(3) the flexible multifunctional sensor network according to the above [ 2 ], wherein a copper coating on a surface of a part of the island-shaped members and a part of the stretchable members is removed by etching;
the other part of the surface of the stretchable member with the copper coating reserved on the surface is used as a stretchable conductor member to electrically connect the guided wave signal acquisition unit and the temperature signal acquisition unit with corresponding interfaces respectively for transmitting signals acquired by the signal acquisition units.
The flexible multifunctional sensor network according to any one of [ 1 ] to [ 3 ], wherein the stretchable member is a serpentine member.
The flexible multifunctional sensor network according to the above (1), wherein the guided wave signal collection unit is a piezoelectric sensor array including 2 or more flexible piezoelectric sensors, and the temperature signal collection unit is a temperature sensor array including 2 or more surface mount temperature sensors.
The flexible multifunctional sensor network according to the above [ 1 ] or [ 5 ], wherein the flexible piezoelectric sensor is a piezoelectric thin film sensor, and the patch type temperature sensor is a patch type thin film temperature sensor.
And (7) the flexible multifunctional sensor network according to the above (6), wherein the flexible piezoelectric sensor is a circular polyvinylidene fluoride piezoelectric film transducer, and the patch type temperature sensor is a square platinum patch resistance type temperature sensor.
[ 8 ] the flexible multifunctional sensor network according to [ 1 ] above, wherein,
the guided wave signal acquisition unit comprises a first excitation terminal and a first signal receiving terminal, the temperature signal acquisition unit comprises a second signal receiving terminal,
the first excitation terminal, the first signal receiving terminal and the second signal receiving terminal are electrically connected to corresponding interfaces respectively, and each interface is arranged on a plurality of fixing components for fixing the flexible multifunctional sensor network.
The flexible multi-function sensor network according to [ 9 ] above [ 8 ], wherein the first excitation terminal and the first signal receiving terminal are used interchangeably.
[ 10 ] A method for manufacturing a flexible multifunctional sensor network, comprising the steps of:
s1: flatly paving a flexible double-sided copper-plated polyimide film on the plane of a workbench, then printing a pre-designed conductive path by using an ink-jet printer, standing until ink is cured, and after the curing is finished, etching by using ferric chloride etching solution to remove an unnecessary copper coating;
s2: then, the obtained polyimide film is tiled on a laser working platform, laser engraving is carried out on the polyimide film according to a pre-designed program and a substrate pattern to remove an unnecessary part, a network-shaped stretchable flexible substrate formed by a plurality of island-shaped members at network nodes and a plurality of stretchable members connecting the island-shaped members is formed, and laser processing is carried out on specific positions of part of the island-shaped members to form through holes;
s3: pouring conductive silver paste into the through hole and solidifying to form a conductive path;
more than 1 island-shaped member is provided with a flexible piezoelectric sensor to form a guided wave signal acquisition unit, an interface corresponding to the guided wave signal acquisition unit is arranged, so that the anode and the cathode of the guided wave signal acquisition unit are electrically connected with the corresponding interface through a stretchable member with a copper coating on the surface,
and mounting patch type temperature sensors on more than 1 island-shaped member to form a temperature signal acquisition unit, and arranging interfaces corresponding to the temperature signal acquisition unit so that the temperature signal acquisition unit is electrically connected with the corresponding interfaces through a stretchable member with a copper coating on the surface.
Advantageous effects
Compared with the prior art, the invention has the following advantages:
(1) The invention designs a highly integrated flexible multifunctional sensing network as a monitoring device, and can effectively adjust the monitoring area and the monitoring area by stretching the network, so that the device has good universality on pressure containers with different shapes and sizes.
(2) Compared with the traditional method for monitoring the structural health of the pressure container based on the guided wave, the method adopts the flexible piezoelectric sensor as the guided wave signal acquisition unit, can avoid the defects of easy breakage, poor conformal capability with the pressure container and high acoustic impedance of the traditional piezoelectric ceramic piece, and improves the reliability of long-term monitoring.
(3) The invention integrates the temperature sensor on the basis of the guided wave damage diagnosis technology, considers the influences of guided wave velocity disturbance caused by temperature change of the pressure container in a working state, such as the increase of the amplitude of the guided wave and the like, and improves the monitoring precision of the pressure container under different working conditions.
Other aspects, features and advantages of the present invention will become apparent in the following detailed description.
Drawings
Fig. 1 is a schematic diagram illustrating a configuration of a flexible multifunctional sensor network according to an embodiment of the present invention.
Fig. 2 is an exploded view of the guided wave signal acquisition unit in the region a of fig. 1.
Fig. 3 is an exploded view of the temperature signal acquisition unit in the area B of fig. 1.
Fig. 4 is a schematic circuit layout diagram of the flexible multifunctional sensor network shown in fig. 1.
FIG. 5 is a tensile test diagram of a flexible multi-functional sensor network according to an embodiment of the present invention.
Fig. 6 is a graph showing the temperature change of the pressure vessel (gas cylinder) during the pressurizing process according to the present invention.
Fig. 7 is a graph showing a comparison of the results of localization of damage before and after temperature correction of the pressure vessel according to the present invention, in which fig. 7 (a) shows the results of localization of damage before temperature correction, and fig. 7 (B) shows the results of localization of damage after temperature correction.
Detailed Description
The technical features of the present invention will be described below with reference to preferred embodiments and drawings, which are intended to illustrate the present invention and not to limit the present invention. The figures are greatly simplified for illustration and are not necessarily drawn to scale.
It is to be understood that the preferred embodiments of the present invention are shown in the drawings only, and are not to be considered limiting of the scope of the invention. Various obvious modifications, variations and equivalents may be made to the present invention by those skilled in the art on the basis of the embodiments shown in the drawings, and technical features in different embodiments described below may be arbitrarily combined without contradiction, and these are within the scope of the present invention.
[ Flexible multifunctional sensor network ]
The configuration and features of the flexible multifunctional sensor network (hereinafter also referred to as "sensor network") according to the present invention will be described in detail below with reference to fig. 1 to 4. Fig. 1 is a schematic diagram illustrating the configuration of a flexible multifunctional sensor network according to an embodiment of the present invention. Fig. 2 is an exploded view of the guided wave signal acquisition unit in the region a of fig. 1. Fig. 3 is an exploded view of the temperature signal acquisition unit in the area B of fig. 1. Fig. 4 is a schematic circuit layout diagram of the flexible multifunctional sensor network shown in fig. 1.
The flexible multifunctional sensing network comprises a stretchable flexible substrate layer 1, a guided wave signal acquisition unit 4, a temperature signal acquisition unit 3 and a plurality of interfaces (P1-P20) which are respectively and electrically connected with the guided wave signal acquisition unit and the temperature signal acquisition unit.
As shown in fig. 1, the stretchable flexible substrate layer 1 is in a network shape, composed of a plurality of island members 5 at nodes of the network and a plurality of stretchable members 6 connecting the island portions. For convenience of description, the sensor network is in a 5 × 5 matrix format, with the bottom left corner of fig. 1 as the origin as the coordinate axis, the horizontal direction as the X-axis direction, 5 columns of the sensor network are sequentially denoted as X1, X2, X3, X4, and X5 from the origin, the vertical direction as the Y-axis direction, and 5 rows of the sensor network are sequentially denoted as Y1, Y2, Y3, Y4, and Y5 from the origin. The island-like structures located at the nodes of the network are denoted as I (x) according to the coordinates of the island-like structures i ,y j ) For example, island-like members located in column 3 and row 1 are denoted as island I (x) 3 ,y 1 )。
In the present embodiment, the sensor network is a 5 × 5 matrix, but the present invention is not limited to this, and may be any matrix such as 6 × 6, 8 × 8, 10 × 10, 100 × 100, or 50 × 200, if necessary.
Between the island members, a stretchable member 6 is formed which connects the island members to each other. The tensile member is preferably a serpentine member such that the network has excellent extensibility to reach 350% or more, more preferably 400% or more of the original length after stretching, and the tensile member preferably has a length of 1000% or less, more preferably 800% or less of the original length in consideration of the strength of the sensor network and the interval between sensors. The line width of the stretchable member is not particularly limited, and may be 0.5 to 5mm, preferably 1 to 4mm, more preferably 1 to 3mm, and most preferably 1 to 2mm. The line width of the tensile member is within the above range, which facilitates laser processing and can ensure that the tensile member is not easily broken when stretched. Monitoring area and monitoring area can be effectively adjusted through stretching the network, so that the device has good universality on pressure containers with different shapes and sizes.
In fig. 1, a part of the surface of the stretchable flexible substrate layer 1 is covered with a conductive copper cladding layer 2, and the copper cladding layer 2 is a black part including a stretchable conductive member and an island-shaped conductive member.
In a preferred embodiment, the stretchable flexible substrate layer 1 is made of a double-sided copper-plated polyimide film having a thickness of 0.1 to 0.5mm, and the island-shaped members 5 and the stretchable members 6 are prepared by laser engraving the double-sided copper-plated polyimide film at normal temperature. The thickness of the double-sided copper-plated polyimide film is preferably 0.2 to 0.5mm, more preferably 0.25 to 0.4mm. The copper cladding is removed from the surface of portions of the island members and portions of the tensile members by an etching process. By removing part of the copper coating on both sides of the film, short circuit of each transmission path can be avoided. In addition, the other part of the surface of the stretchable member, on which the copper coating is remained, is used as a stretchable conductor member to electrically connect the guided wave signal acquisition unit and the temperature signal acquisition unit with the corresponding interfaces respectively, and can be used for transmitting the signals acquired by the signal acquisition units.
For example, in FIG. 1, island-like members (e.g., island I (x)) appear black 1 ,y 5 )、I(x 2 ,y 3 )、I(x 3 ,y 2 )、I(x 3 ,y 4 )、I(x 4 ,y 3 )、I(x 5 ,y 3 ) And stretchable member means a member having white (or hollow) island-like members (e.g., island I (x)) with a copper coating remaining on the surface of the member 1 ,y 1 )、I(x 1 ,y 2 )、I(x 5 ,y 4 ) Etc.) and the tensile member means that the copper coating of the surface of the member is removed. In addition, island-like members (e.g., island I (x)) shaded in gray 2 ,y 2 )、I(x 3 ,y 3 ) Etc.) means that a guided wave signal pickup unit or a temperature signal pickup unit is carried on the island-shaped member.
In addition, according to the circuit layout requirement, it is preferable that a through hole is formed in a specific portion of a part of the island-shaped members by laser processing, and a conductive silver paste is poured into the through hole, so that the copper clad layers on the front and back surfaces of the island-shaped members are electrically conducted.
In the flexible multifunctional sensor network, the guided wave signal acquisition unit comprises more than one flexible piezoelectric sensor, and the flexible piezoelectric sensors are distributed 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, in FIG. 1, at island I (x) 1 ,y 4 )、I(x 3 ,y 1 )、I(x 3 ,y 3 )、I(x 5 ,y 2 ) Patch type temperature sensors are respectively arranged on the base plates to form an array of the patch type temperature sensors.
In addition, in the flexible multifunctional sensor network, the temperature signal acquisition unit comprises more than one patch type temperature sensor, and the patch type temperature sensors are distributed on the island-shaped component. The temperature signal acquisition unit is preferably a temperature sensor array composed of more than 2 patch type temperature sensors. For example, in FIG. 1, at island I (x) 2 ,y 2 )、I(x 2 ,y 4 )、I(x 4 ,y 2 )、I(x 4 ,y 4 ) Are respectively arranged with flexible piezoelectric sensors to form an array of flexible piezoelectric sensors.
In the flexible multifunctional sensor network of the present invention, the flexible piezoelectric sensor and the surface mount type temperature sensor are respectively and independently supported on the island-shaped member. The shape and size of the island members are preferably adapted to the flexible piezoelectric sensor and the patch temperature sensor they carry.
In the invention, the flexible piezoelectric sensor is a sensor based on piezoelectric effect with flexibility, which is a self-generating type and electromechanical conversion type sensor and is used 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 film sensor has the characteristics of thinness, light weight and softness, and has the advantages of wide frequency response, large dynamic range, high force point conversion sensitivity, light weight, softness, no brittleness, impact resistance and the like. The thickness of the flexible piezoelectric sensor is 0.05 to 0.5mm, preferably 0.1 to 0.4mm, and more preferably 0.2 to 0.3mm. The shape of the flexible piezoelectric sensor is not particularly limited, and may be circular, square, hexagonal, or the like, and is preferably circular. Fig. 1 shows a sensor network in which circular flexible piezoelectric sensors are used. The size of the flexible piezoelectric sensor is not particularly limited and may be selected as needed, and for example, in the case of using a circular flexible piezoelectric sensor, the diameter thereof may be 5 to 10mm.
By adopting the flexible piezoelectric sensor as the guided wave signal acquisition unit, the defects of fragility, poor conformal capability with a pressure container and high acoustic impedance of the traditional piezoelectric ceramic piece can be avoided, and the reliability of long-term monitoring can be improved.
In addition, the patch type temperature sensor is used for collecting temperature signals. The patch type temperature sensor has the characteristics of high measurement precision and high response speed when being 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 type temperature sensor is more preferably used. The platinum patch resistance type temperature sensor has the advantages of high precision, good stability and wide application temperature range. The thickness of the surface mount type temperature sensor is not particularly limited, and may be 0.05 to 3mm, preferably 0.1 to 1mm. The shape of the surface mount type temperature sensor is not particularly limited, and may be circular, square, hexagonal, or the like, and is preferably square. A square patch type temperature sensor is used in the sensing network shown in fig. 1. The size of the surface mount type temperature sensor is not particularly limited, and may be selected as needed, and for example, in the case of using a square surface mount type temperature sensor, the side length thereof may be 5 to 12mm, preferably 8 to 10mm.
The flexible piezoelectric sensor preferably includes a first excitation terminal electrically connected to the corresponding interface and exciting the piezoelectric sensor, and a first signal receiving terminal connected to the corresponding interface and transmitting the piezoelectric signal to the computer through a port and a circuit. The first excitation terminal and the first signal receiving terminal may be used interchangeably in the present invention.
The temperature signal acquisition unit preferably comprises a second signal receiving terminal for electrically connecting with a corresponding interface and transmitting the received temperature signal to the computer.
In some preferred embodiments, the 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 fixing members of the flexible multifunctional sensor network, and the fixing members are used to fix the flexible multifunctional sensor network to the pressure vessel. For convenience of explanation, the fixing means are provided with reference symbols corresponding to the respective interfaces (P1 to P20).
The sensing network transmits the guided wave signals acquired by the guided wave signal acquisition unit and the temperature signals acquired by the temperature signal acquisition unit to a computer through a plurality of interfaces, corrects the wave velocity based on the temperature signals, and is combined with the guided wave signals to monitor and position the damage of the pressure container.
The connection and operation of each constituent element of the sensor network according to the preferred embodiment of the present invention will be described in detail below with reference to fig. 2 to 3.
Fig. 2 is an exploded view of the guided-wave signal collection unit in the region a of fig. 1, where the region a includes an island I (x 2, y 2), an island I (x 2, y 1), and a stretchable member connecting the two islands, and a circular PVDF piezoelectric thin film transducer (hereinafter also referred to as a PVDF piezoelectric thin film) is supported on the island I (x 2, y 2). As can be seen from fig. 2, the front surfaces of the islands I (x 2, y 1) and the stretchable member are white, indicating that the copper clad layer on the front surface of the copper-clad polyimide film 11 is removed, but the copper clad layer 12 remains on the back surface of the copper-clad polyimide film 11 for electrical connection with the PVDF piezoelectric film and transmission of electrical signals.
The guided wave signal acquisition unit integrally presents a stacked structure, is sandwiched between an upper layer and a lower layer of copper-clad polyimide films 11, and is formed by respectively bonding the upper side and the lower side of a PVDF piezoelectric film 14 with copper-clad layers 12 on the copper-clad polyimide films 11 through z-axis conductive adhesive tape layers 13 of 10-30 mu m, so that electrical connection and mechanical connection are realized, and electrical signals are transmitted from an island I (x 2, y 1) to the anode of the PVDF piezoelectric film 14 at the island I (x 2, y 2) through a tensile component. The island I (x 2, y 1) is formed by closely bonding the copper clad layers 12 of the two layers of copper clad polyimide 11 via a z-axis conductive tape, thereby achieving electrical and mechanical connection, and outputting a piezoelectric signal collected from the PVDF piezoelectric film to a corresponding interface.
Fig. 3 is an exploded view of the temperature signal acquisition unit in the area B of fig. 1. The area B comprises an island I (x 3, y 1) and tensile members connected with the two sides of the island I (x 3, y 1), the upper part of the drawing is the front side of the island I (x 3, y 1), the lower part of the drawing is the reverse side of the island I (x 3, y 1), and the middle part of the drawing is an exploded structural view of the temperature signal acquisition unit. In the island-like member and the stretchable member in fig. 3, the white portions indicate that the copper clad layer on the surface of the copper-clad polyimide film 21 is removed, and the black portions indicate that the copper clad layer 22 on the surface of the copper-clad polyimide film 21 remains as a lead.
A through hole 23 with the aperture of about 1-2 mm formed by laser processing is arranged at a specific part of the island I (x 3, y 1), and a conductive silver paste 24 is poured into the through hole 23 to form a conductive path for conducting copper cladding layers at both sides of the copper-clad polyimide film. A patch temperature sensor 25 for collecting a temperature signal is mounted on the island I (x 3, y 1). As shown in the exploded view of fig. 3, the positive electrode 26 and the negative electrode 27 of the chip temperature sensor are bonded to the copper clad of the copper-clad polyimide film via the z-axis conductive tape 28, wherein the negative electrode is electrically connected to the copper clad on the other side of the copper-clad polyimide film through the conductive path of the through-hole portion to form a conductive path. And transmitting the electric signals to the surface mount type temperature sensor through the anode and the cathode of the surface mount type temperature sensor and transmitting the acquired temperature signals to corresponding interfaces.
The circuit layout of the flexible multifunctional sensor network according to the preferred embodiment of the present invention is described below with reference to fig. 4.
In the flexible multifunctional sensor network of the present invention, the temperature signal collection units 3 and the guided wave signal collection units 4 are arranged in a distributed manner on a plurality of island-shaped members, and the island-shaped members are interconnected with each other by the stretchable members. The temperature signal acquisition unit 3 and the guided wave signal acquisition unit 4 are connected with the outside (for example, a computer) through corresponding interfaces (P1 to P20). The sensor network is arranged on the surface of the pressure vessel after stretching by means of a fixing component at the interface. In fig. 4, the gray lines are back lines of the sensor network, the black lines are front lines, and the nodes where the black lines and the gray lines are connected are junctions electrically connected through conductive silver paste of the through holes.
In the process of collecting temperature signals and guided wave signals, current flows in from the signal input end and flows out from the negative electrode of the circuit after flowing through the temperature collecting unit (a patch type temperature sensor) and the guided wave collecting unit (a flexible piezoelectric sensor). The circuit layout is designed flexibly according to the number of sensors and the installation position, and a preferred arrangement of the circuit paths of each signal acquisition unit is described by taking a 5 × 5 matrix multifunctional sensor network shown in fig. 4 as an example.
Because all the similar sensors are connected by adopting a common negative electrode, the potential of the whole negative electrode surface is the same and can be regarded as the common ground. The common ground plane of the temperature sensors is I (x 1, y 3) -I (x 1, y 2) -I (x 1, y 1) -I (x 2, y 1) -I (x 3, y 1) -I (x 4, y 1) -I (x 5, y 1), and the whole common ground path is named as Gt. The common ground plane of the piezoelectric sensor is I (x 2, y 4) -I (x 3, y 4) -I (x 4, y 3) -I (x 4, y 2) -I (x 3, y 2) -I (x 2, y 3) -I (x 5, y 3), and the whole common ground path is named Gg.
The circuit layout of each temperature sensor (T1 to T5) is as follows:
T1:7→P15→I(x1,y5)→T1→Gt→P5→10
T2:7→P13→I(x3,y5)→I(x3,y4)→T2→Gt→P5→10
T3:7→P7→T3→Gt→P5→10
T4:7→P3→T4→Gt→P5→10
the circuit layout of each of the piezoelectric sensors (PT 1 to PT 5) is as follows:
PT1:8→P14→I(x2,y5)→PT1→Gg→P8→9
PT2:8→P12→I(x4,y5)→PT2→Gg→P8→9
PT3:8→P4→I(x4,y1)→PT3→Gg→P8→9
PT4:8→P2→I(x2,y1)→PT4→Gg→P8→9
the circuit layout of the sensors of the temperature signal acquisition unit and the guided wave signal acquisition unit is only a preferred embodiment, and the present invention is not limited thereto, and on the premise that the operation of the sensors and the signal acquisition and transmission can be realized, a person skilled in the art can make any changes and combinations according to actual needs.
[ method for manufacturing flexible multifunctional sensor network ]
The preferred flexible multifunctional sensor network of the present invention can be manufactured by the following method.
The method comprises the steps of flatly paving a flexible double-sided copper-plated polyimide film on a plane of a workbench, printing a pre-designed conductive path by using an ink-jet printer, standing until ink is cured, and etching and removing an unnecessary copper coating by using ferric chloride etching solution after the curing is finished (step S1). In this step, the curing temperature is preferably room temperature, the curing time is preferably 12 to 24 hours, and the etching time is preferably 5 to 20 minutes.
Next, the obtained polyimide film is laid on a laser work table, laser engraving is performed on the polyimide film according to a pre-designed program and a substrate pattern to remove an unnecessary portion, a network-like stretchable flexible substrate composed of a plurality of island members at network nodes and a plurality of stretchable members connecting the island members is formed, and laser processing is performed at specific positions of part of the island members to form through holes (step S2). In this step, the stretchable member is preferably processed into a serpentine member. In addition, it is preferable that the island-shaped members and the stretchable members each having a copper coating on the surface are further coated with an insulating material for electromagnetic protection. As the insulating material, an insulating material such as silicone three-proofing adhesive is preferably used.
Then, pouring conductive silver paste into the through hole and solidifying to form a conductive path; installing flexible piezoelectric sensors on more than 1 island-shaped member to form a guided wave signal acquisition unit, and arranging interfaces corresponding to the guided wave signal acquisition unit so that the positive and negative electrodes of the guided wave signal acquisition unit are electrically connected with the corresponding interfaces through stretchable members with copper coatings on the surfaces; mounting patch type temperature sensors on more than 1 island-shaped member to form a temperature signal acquisition unit, and arranging interfaces corresponding to the temperature signal acquisition unit so that the temperature signal acquisition unit is electrically connected with the corresponding interfaces through a stretchable member with a copper coating on the surface (step S3). In this step, the curing condition of the conductive silver paste is preferably at 100-150 ℃ for 5 minutes-8 hours. In addition, the flexible piezoelectric sensor and the patch type temperature sensor are preferably bonded to the island-shaped member by a z-axis conductive tape to achieve electrical conduction and mechanical connection. Further, as the flexible piezoelectric sensor, a PVDF piezoelectric thin film transducer is preferably used, and as the patch type temperature sensor, a platinum patch resistance type temperature sensor is preferably used.
Examples
The present invention will be further described with reference to the following examples, but it should be understood that the following examples are only illustrative of the practice of the present invention and are not intended to limit the scope of the present invention.
(manufacturing of Flexible multifunctional sensor network)
A flexible double-sided copper-plated polyimide film with the thickness of 0.25mm is laid on the plane of a workbench, then a pre-designed conductive path is printed by an ink-jet printer, then the ink is solidified after standing for 12 hours at room temperature, and after the solidification is finished, etching is carried out for 10 minutes by using ferric chloride etching solution (ferric chloride-water solution with the mass fraction of 20%) to remove the unnecessary copper coating.
Then, the obtained polyimide film was laid on a laser working platform (Stone MMEPU-355-5, tianjingmeman laser technology limited), laser engraving (laser power 5w, laser spot size 25 μm, engraving rate 10 mm/s) was performed on the polyimide film according to a pre-designed program and a substrate pattern to remove unnecessary portions, to form a 5 × 5 array-type sensor network shown in fig. 1, which is composed of a plurality of island-shaped members at network nodes and a plurality of stretchable members connecting the island-shaped portions, the stretchable members were formed into a serpentine structure with a line width of 1mm, and laser processing was performed at specific positions of some of the island-shaped members to form through holes with a hole diameter of 1mm. And further spraying organic silicon three-proofing glue serving as an insulating material on the surfaces of the island-shaped member and the stretchable member, the surfaces of which are provided with the copper coating, for electromagnetic protection.
Then, conductive silver paste (SINWE 3701) is poured into the through holes and cured at 150 ℃ for 5 minutes to form conductive paths; adhering and mounting square platinum patch resistance type temperature sensors (10 mm side length, 0.1mm thickness, and 100 omega initial resistance at 25 ℃) on the 4 island-shaped members respectively by using z-axis anisotropic conductive adhesive tapes to form a temperature sensor array; circular PVDF piezoelectric thin-film piezoelectric transducers (with the thickness of 0.2mm, the diameter of 9mm and the sampling center frequency of 200 kHz) are respectively bonded and installed on the 4 island-shaped members by using z-axis anisotropic conductive adhesive tapes to form an array of the piezoelectric thin-film piezoelectric transducers, and the specific arrangement is shown in figure 1. Interfaces corresponding to the temperature sensors and the piezoelectric thin-film piezoelectric transducers are provided, the stretchable serpentine member with the copper coating on the surface is electrically connected with the corresponding interfaces, and the sensors are communicated according to the circuit layout circuit shown in fig. 4.
(tensile test of Flexible multifunctional sensor network)
The serpentine portion of the flexible multifunctional sensor network prepared above was mounted in an upper ultimate stretcher (ESM 750S, mark-10, usa) for uniaxial stretching experiments to obtain force-length data as shown in fig. 5. As can be seen in FIG. 5, after the serpentine length is stretched to 390% of its original length, there is a sharp change in force, indicating that the serpentine breaks. Namely, the snake-shaped structure part has high extensibility which can be extended to the original length of 390 percent, and the flexible multifunctional sensing network can flexibly adjust the monitoring area and the area, has excellent extensibility and has good universality on pressure containers with different shapes and sizes.
(temperature change during inflation and deflation of pressure vessel)
The prepared flexible multifunctional sensing network is stretched and arranged on the surface of a gas cylinder (pressure container). The temperature signals of the platinum patch resistance type temperature sensors are acquired through a multi-channel data acquisition card, and an input port 7 and an output port 10 of each temperature sensor are respectively connected to a multi-channel data acquisition card NI-9273 (National Instruments, USA). And for an output port and an input port, setting the sampling voltage to be 1v and the sampling frequency to be 20Hz, automatically acquiring multi-channel current signals, and exporting data to a computer for recording. Collecting the temperature signals of the gas cylinder in the pressurizing process, wherein the pressurizing parameters are 0.8Mpa/s of inflation speed, 10Mpa/s of deflation speed, 20Mpa of peak pressure and 0s of peak holding time. The temperature acquisition result is shown in fig. 6, which shows the temperature acquisition capability of the temperature sensor array.
The principle of temperature-corrected ultrasonic guided waves is related to the propagation mechanism of ultrasonic guided waves, which are generally divided into transverse waves and longitudinal waves, and the wave velocity of the longitudinal waves propagating along the tubular structure is shown in formula (1):
the transverse wave propagates along the tubular structure as shown in equation (2):
wherein E is the Young's modulus of the material; rho is the material density; sigma is the Poisson ratio; g is the modulus of rigidity. The method can be used for obtaining the relation between the change of the rigid modulus of the solid elastic modulus and the temperature by adopting a statistical fitting method based on experiments, and then correcting the wave velocity based on the relation, so that the positioning precision can be improved.
(guided wave-based damage localization test)
And (3) stretching the prepared flexible multifunctional sensing network to a proper size along a transverse and longitudinal axis, and fixing the flexible multifunctional sensing network on the surface of the gas cylinder by using an adhesive. And performing a frequency sweep experiment on a PVDF piezoelectric transducer terminal used for collecting guided wave signals in the sensor network to obtain the central frequency and the bandwidth of the guided wave signal collecting terminal, wherein the central frequency is selected to be 200Khz, and the bandwidth is 30db. The guided wave signal is generated by a signal generator, is input into the anode of an excitation terminal through an input port 8 by a signal attenuator, is output to a signal amplifier through an output port 9 after being received by a receiving terminal, and finally is displayed on an oscilloscope to complete single-channel guided wave signal acquisition. And finally, carrying out damage positioning imaging by using an ellipse algorithm. As a result of imaging without temperature correction, as shown in fig. 7 (a), the damaged position of the pressure vessel and the imaging position are close to each other, and the abscissa and ordinate positioning accuracy was 91% and 92% respectively before the temperature correction wave velocity was not performed. On the other hand, the results of the damage detection and the positioning obtained by correcting the wave velocity based on the acquired temperature signal are shown in fig. 7 (B), and the abscissa and ordinate positioning accuracy after the correction is 95.2% and 96.7%, respectively. Therefore, by arranging the guided wave signal acquisition unit and the temperature signal acquisition unit comprising the temperature sensor in the flexible multifunctional sensor network, the influence of guided wave velocity disturbance and the like caused by temperature change of the pressure container in a working state is considered, the guided wave velocity is corrected based on the acquired temperature signal, and the monitoring precision of damage positioning of the pressure container in different working conditions can be obviously improved.
Finally, it should be understood that the above description of embodiments and examples is illustrative in all respects and not restrictive, and that various modifications may be made by those skilled in the art without departing from the spirit of the invention without inventive faculty. The scope of the invention is indicated by the claims rather than by the foregoing description of embodiments or examples. The scope of the present invention includes all modifications within the meaning and range equivalent to the claims.
Moreover, although the foregoing specification and associated drawings describe exemplary embodiments in terms of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may 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 than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Industrial applicability of the invention
The flexible multifunctional sensing network has excellent tensile ductility, integrates the guided wave signal acquisition unit and the temperature signal acquisition unit, can flexibly and adjustably set the monitoring area, is integrated on the surface of a pressure container to realize online monitoring, and has good application prospect in the field of accurate positioning of damage defects.
Claims (10)
1. A flexible multifunctional sensing network comprises a stretchable flexible substrate layer, a guided wave signal acquisition unit, a temperature signal acquisition unit and a plurality of interfaces which are respectively and electrically connected with the guided wave signal acquisition unit and the temperature signal acquisition unit,
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 portions,
the guided wave signal acquisition unit comprises more than one flexible piezoelectric sensor which is distributed on the island-shaped member,
the temperature signal acquisition unit comprises more than one patch type temperature sensor which is distributed on the island-shaped component,
the flexible piezoelectric sensor and the patch type temperature sensor are respectively and independently carried on the island-shaped component,
and transmitting the guided wave signals collected by the guided wave signal collecting unit and the temperature signals collected by the temperature signal collecting unit to a computer through the interface, correcting the wave velocity based on the temperature signals, and combining the corrected wave velocity with the guided wave signals to monitor and position the damage of the pressure container.
2. The flexible multifunctional sensor network according to claim 1, wherein said stretchable flexible substrate layer is made of a double-sided copper-plated polyimide film having a thickness of 0.1-0.5 mm, said island members and said stretchable members being prepared by laser engraving said double-sided copper-plated polyimide film at normal temperature.
3. The flexible multifunctional sensor network of claim 2 wherein the copper cladding of portions of said island members and portions of said stretchable member surfaces are removed by an etching process;
and the other part of the surface of the stretchable member with the copper coating reserved on the surface is used as a stretchable conductor member to electrically connect the guided wave signal acquisition unit and the temperature signal acquisition unit with corresponding interfaces respectively for transmitting signals acquired by the signal acquisition units.
4. The flexible multifunctional sensor network of any one of claims 1 to 3 wherein said stretchable members are serpentine members.
5. The flexible multifunctional sensor network of claim 1, wherein 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.
6. The flexible multifunctional sensor network according to claim 1 or 5, wherein said flexible piezoelectric sensor is a piezoelectric thin film sensor and said patch type temperature sensor is a patch type thin film temperature sensor.
7. The flexible multifunctional sensor network of claim 6 wherein said flexible piezoelectric sensor is a polyvinylidene fluoride piezoelectric film transducer and said patch temperature sensor is a platinum patch resistive temperature sensor.
8. The flexible multifunctional sensor network of claim 1,
the flexible piezoelectric sensor comprises a first excitation terminal and a first signal receiving terminal, the patch type temperature sensor comprises a second signal receiving terminal,
the first excitation terminal, the first signal receiving terminal and the second signal receiving terminal are electrically connected to corresponding interfaces respectively, and each interface is arranged on a plurality of fixing components for fixing the flexible multifunctional sensor network.
9. The flexible multi-function sensor network of claim 8, wherein said first excitation terminal and said first signal receiving terminal are used interchangeably.
10. A method of manufacturing a flexible multifunctional sensor network, comprising the steps of:
s1: flatly paving a flexible double-sided copper-plated polyimide film on the plane of a workbench, then printing a pre-designed conductive path by using an ink-jet printer, standing until ink is cured, and after the curing is finished, etching by using ferric chloride etching solution to remove an unnecessary copper coating;
s2: then, the obtained polyimide film is tiled on a laser working platform, laser engraving is carried out on the polyimide film according to a pre-designed program and a substrate pattern to remove an unnecessary part, a network-shaped stretchable flexible substrate formed by a plurality of island-shaped members at network nodes and a plurality of stretchable members connecting the island-shaped members is formed, and laser processing is carried out on specific positions of part of the island-shaped members to form through holes;
s3: pouring conductive silver paste into the through hole and solidifying to form a conductive path;
more than 1 island-shaped member is provided with a flexible piezoelectric sensor to form a guided wave signal acquisition unit, an interface corresponding to the guided wave signal acquisition unit is arranged, so that the anode and the cathode of the guided wave signal acquisition unit are electrically connected with the corresponding interface through a stretchable member with a copper coating on the surface,
and mounting patch type temperature sensors on more than 1 island-shaped member to form a temperature signal acquisition unit, and arranging interfaces corresponding to the temperature signal acquisition unit so that the temperature signal acquisition unit is electrically connected with the corresponding interfaces through a stretchable member with a copper coating on the surface.
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