Grid type crack sensor and preparation method thereof

Abstract

The invention discloses a grating type crack sensor and a preparation method thereof, and relates to the technical field of crack monitoring. The grating type crack sensor comprises a flexible base layer, a protective layer, at least two sensing layers and an insulating layer arranged between every two adjacent sensing layers, each sensing layer comprises a plurality of parallel conductive grid bars, one ends of the conductive grid bars are connected through a conductive sheet, and the conductive grid bars of different sensing layers are staggered to form a grating structure. The multi-layer conductive grid bars are staggered to form the grid structure, the crack length can be monitored, the crack propagation direction can be monitored, more accurate crack information can be obtained, the environment influence resistance is enhanced through the design of the flexible base layer, the protection layer and the insulation layer, and therefore an accurate crack positioning result is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of crack monitoring, and in particular to a grid-type crack sensor and a preparation method thereof. Background Art

[0002] In large structures such as steel bridges, buildings, high-rise towers, aircraft, and ships, fatigue cracks in stress concentration areas such as connection nodes and welding parts not only directly threaten the overall stability and durability of the structure, but may also lead to catastrophic consequences. Therefore, early detection and real-time monitoring of cracks in these large structures, especially crack monitoring in key parts, have become important measures to ensure the safe operation of the structure and extend its service life.

[0003] At present, the main crack monitoring technologies include ultrasonic testing, magnetic particle testing, thermal imaging testing and visual inspection. Although these technologies can identify cracks in structures to a certain extent, they also have some significant shortcomings. First, they need to rely on high-precision equipment, which leads to high detection costs; second, the operation process is complicated, and professionals are required to conduct regular inspections and data analysis. It is difficult to apply them in large-scale structures, and it is impossible to detect and monitor small cracks in the early stage; in addition, these traditional methods are sensitive to environmental factors, such as changes in temperature and humidity, which will affect the performance of the detection equipment and reduce the detection accuracy; more importantly, traditional methods can usually only cover local areas, and it is difficult to conduct comprehensive and real-time crack monitoring of large structures, especially in the sensitive monitoring of the early stage of crack development. There are great challenges.

[0004] In order to solve these problems, crack monitoring technology based on coating sensors can provide the advantages of low cost, easy operation and wide coverage, and has gradually attracted widespread attention. By applying a crack-sensitive functional coating on the surface of the structure, the coating sensor monitoring technology makes the monitoring system simple, convenient for signal processing, and has a wide range of applications. It has become an important development direction in the field of structural health monitoring. However, the existing coating sensor monitoring technology still has some shortcomings. First, in terms of environmental adaptability, external factors such as temperature and humidity may affect the monitoring accuracy of the sensor, thereby affecting the performance of long-term stability; secondly, the design of traditional coating sensors is mostly focused on the detection of crack length, lacking the ability to monitor complex crack extension paths in real time, and has limitations in obtaining crack information.

[0005] Therefore, in view of the above-mentioned deficiencies, the present invention proposes an improved coating sensor and crack monitoring system. Summary of the invention

[0006] The present invention provides a grid type crack sensor and a preparation method thereof, so as to solve the problem that the existing coating sensor can only monitor the crack length and the monitoring accuracy is easily affected by the environment.

[0007] The present invention is achieved through the following technical solutions:

[0008] A first aspect of the present invention provides a grid-type crack sensor, comprising:

[0009] A flexible base layer and a protective layer, wherein the flexible base layer is used to connect the component to be tested;

[0010] at least two sensing layers, wherein the sensing layers are disposed between the flexible base layer and the protective layer;

[0011] An insulating layer, arranged between two adjacent sensing layers;

[0012] Each of the sensing layers comprises a plurality of parallel conductive bars, one ends of the plurality of conductive bars are connected via a conductive sheet, and the conductive bars of different sensing layers are staggered to form a grid structure.

[0013] The grid-type crack sensor of the present invention forms a grid structure by staggering conductive bars of multiple sensing layers. When measuring, a voltage is applied to the conductive sheet. When the crack is transmitted to the conductive bars through the flexible base layer, the conductive bars break at the crack. Multiple layers of parallel conductive bars are staggered to form a grid structure. Through the crack information received on different sensing layers, not only the crack length can be monitored, but also the different directions of crack extension can be monitored, thereby providing accurate crack location information in the early stage of crack extension. An insulating layer is set between two adjacent sensing layers to prevent the two sensing layers from being directly connected, and serves as the printing base layer of the next sensing layer. The protective layer protects the coating sensor, enhances the ability to resist environmental influences, and ensures safety in use.

[0014] In some embodiments, the sensing layer includes a first sensing layer and at least one second sensing layer; the conductive bars and conductive sheets of the first sensing layer are made by printing conductive ink on the flexible base layer; the conductive bars and conductive sheets of the second sensing layer are made by printing conductive ink on the insulating layer.

[0015] In some embodiments, the conductive ink comprises flake-shaped conductive particles and self-drying ink.

[0016] In some embodiments, there is one second sensing layer, and the conductive grids of the first sensing layer and the second sensing layer are perpendicular to each other.

[0017] In some embodiments, the material of the insulating layer is modified polyurethane resin.

[0018] In some embodiments, the material of the protective layer is anti-corrosion spray paint.

[0019] In some embodiments, the grid-type crack sensor further includes a single-chip microcomputer, a ground line of the single-chip microcomputer is connected to the conductive sheet, and an I / O port of the single-chip microcomputer is connected to the other end of the conductive grid bar for receiving crack information.

[0020] In some embodiments, the grid-type crack sensor further includes a WiFi module, and the WiFi module is integrated with the single-chip microcomputer so that the single-chip microcomputer communicates with a remote terminal.

[0021] A second aspect of the present invention provides a method for preparing the grid-type crack sensor according to any one of the first aspects of the present invention, comprising:

[0022] S1, preparing a flexible base layer;

[0023] S2, coating the prepared conductive ink on the flexible base layer by a screen printer and curing at room temperature;

[0024] S3, printing an insulating layer on the flexible base layer;

[0025] S4, coating the prepared conductive ink on the insulating layer by a screen printer and curing at room temperature;

[0026] S5, spraying a protective layer on the insulating layer, or spraying a protective layer on the outermost sensing layer after preparing multiple insulating layers and sensing layers, to obtain a grid-type crack sensor.

[0027] In some embodiments, the conductive ink is prepared by:

[0028] Adding a leveling agent to the self-drying ink and stirring evenly to obtain a first mixture;

[0029] Adding flaky conductive particles to the first mixture and stirring evenly to obtain a second mixture;

[0030] A curing agent is added to the second mixture, and the mixture is stirred evenly to obtain the conductive ink.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] A grid structure is formed by staggered arrangement of multiple layers of parallel conductive bars. By receiving crack information on different sensing layers, not only the crack length but also the different directions of crack extension can be monitored, thereby providing accurate crack location information in the early stages of crack extension.

[0033] An insulating layer is arranged between two adjacent sensing layers to prevent the two sensing layers from being directly connected and to serve as a printing effect for the next sensing layer; the insulating layer adopts modified polyurethane resin to improve the printing effect for the next sensing layer.

[0034] The protective layer ensures safe use and enhances its ability to resist environmental influences; the protective layer adopts anti-corrosion self-spray paint to improve the durability of the coated sensor and further enhance its ability to resist environmental influences.

[0035] The sensing layer uses conductive ink, which contains flaky conductive particles and self-drying ink, and is prepared by screen printing with a leveling agent to improve printability to ensure the accuracy of the conductive path.

[0036] The coating sensor of the present invention performs monitoring and signal processing based on a single chip microcomputer, has low equipment cost and simplifies the signal processing process, can provide accurate crack location information in the early stage of crack propagation, and provides strong technical support for the structural health monitoring system. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0038] Figure 1 is a schematic structural diagram of a grid-type crack sensor according to an embodiment of the present invention;

[0039] Figure 2 is a schematic structural diagram of a sensing layer according to an embodiment of the present invention;

[0040] Figure 3 is a schematic diagram of the connection between a single chip microcomputer and a sensing layer according to an embodiment of the present invention;

[0041] Figure 4 is a flow chart of preparing a grid-type crack sensor according to an embodiment of the present invention;

[0042] Figure 5 The figure is a schematic diagram of a conductive ink preparation process according to an embodiment of the present invention;

[0043] Figure 6 Shown is a crack monitoring system according to an embodiment of the present invention.

[0044] The reference numerals and their descriptions are as follows:

[0045] 100 - flexible base layer, 200 - sensing layer, 300 - protective layer, 400 - insulating layer, 210 - first sensing layer, 220 - second sensing layer, 201 - conductive grid bars, 202 - conductive sheets, 500 - single chip microcomputer. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0047] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to or inherent to other steps or units of the device.

[0048] The terms used in various embodiments of the present invention are only used for the purpose of describing specific embodiments and are not intended to limit various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meaning generally understood by those of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in various embodiments of the present invention.

[0049] The embodiments of the present invention provide a grid-type crack sensor and a preparation method thereof, which are suitable for real-time monitoring of cracks in structures, and are beneficial for early crack detection and improving crack location accuracy.

[0050] like Figure 1 The figure shows a schematic diagram of the structure of a grid-type crack sensor according to an embodiment of the present invention, which adopts a multi-layer coating sensor structure, including a flexible base layer 100, a sensing layer 200 and a protective layer 300 from bottom to top. The sensing layer 200 is a conductive coating, there are at least two of them, and an insulating layer 400 is provided between two adjacent sensing layers 200 to play an isolation role.

[0051] like Figure 2 The figure is a schematic diagram of the structure of the sensing layer 200, which includes a plurality of parallel conductive bars 201, one end of which is connected by a conductive sheet 202, so that the same voltage is applied to the plurality of parallel conductive bars through the conductive sheet to ensure the uniformity of material properties.

[0052] The flexible base layer 100 is made of epoxy resin, which has good toughness and brittleness. As a flexible substrate, one side surface is used to prepare the sensing layer, and the other side is adhered to the surface of the structure to be measured by a high-performance adhesive. The flexible design of the sensor ensures that it can be closely attached to the surface of the steel bridge and can maintain normal operation as the structure deforms. When a crack occurs, the crack is transmitted from the surface of the structure to the flexible base layer 100, causing the conductive bars at the corresponding position of the sensing layer to break, destroying the conductive path of the sensor, causing the circuit to break, and the crack information is obtained by monitoring the on-off status of multiple conductive bars.

[0053] The conductive grid bars 201 of different sensing layers 200 are staggered to form a grid structure. Figure 2 Taking the grid-type crack sensor including two sensing layers 200 as an example, the first sensing layer 210 is arranged between the flexible base layer 100 and the insulating layer 400, and the second sensing layer 220 is arranged between the insulating layer 400 and the protective layer 300. There is an angle difference between the parallel conductive bars 201 of the first sensing layer 210 and the second sensing layer 220, and the interlaced parts form a two-dimensional grid structure. The directions of the two layers of parallel conductive bars are different, and the extended crack can be monitored from two directions.

[0054] In the case of three or more sensing layers, the grid-type crack sensor includes a first sensing layer 210 and at least one second sensing layer 220, wherein the first sensing layer 210 is disposed between the flexible base layer 100 and the insulating layer 400, and the second sensing layer 220 is disposed between two insulating layers 400 or between the insulating layer 400 and the protective layer 300. The conductive bars of different sensing layers are staggered to form a grid structure.

[0055] The multi-layer grid-coated sensor design significantly improves the accuracy of crack monitoring and can effectively monitor the crack extension path, rather than just the length of the crack. By staggering conductive lines to form a grid structure, this design can more accurately capture the starting position of the crack and its extension direction, providing more detailed data support for later structural repair and reinforcement, and timely discovering and tracking crack development in the early stages of the crack, greatly improving the sensitivity and reliability of the monitoring system.

[0056] In some embodiments, the conductive grid bars 201 and conductive sheets 202 of the first sensing layer 210 are made by printing conductive ink on the flexible substrate 100 , and the conductive grid bars 201 and conductive sheets 202 of the second sensing layer 220 are made by printing conductive ink on the insulating layer 400 .

[0057] In some embodiments, there is one second sensing layer 220, and the conductive bars of the first sensing layer 210 and the second sensing layer 220 are perpendicular to each other. The conductive bars are staggered in the longitudinal and transverse directions to form a two-dimensional grid structure, which tracks the development of cracks in two directions, ensuring positioning accuracy. At the same time, the double-layer grid only needs to process data in two dimensions, reducing the amount of data processing.

[0058] In some embodiments, the conductive ink contains flaky conductive particles. The conductive material in the conductive ink is provided by the conductive particles, and the flaky conductive particles have good conductivity, improve monitoring sensitivity, and have low production cost.

[0059] In some embodiments, the conductive particles are silver-plated copper particles.

[0060] In some embodiments, the insulating layer is made of modified polyurethane resin, which can prevent two sensing layers from being directly connected and improve the printing effect of the next sensing layer.

[0061] In some embodiments, the protective layer is made of anti-corrosion self-spray paint, which can improve the durability of the coated sensor and enhance its ability to resist environmental influences.

[0062] In some embodiments, the grid-type crack sensor further includes a single-chip microcomputer 500. Figure 3 The figure shows the connection diagram of the single chip microcomputer and the sensing layer. The ground wire (GND) of the single chip microcomputer 500 is connected to the conductive sheet 202, and the I / O port of the single chip microcomputer is connected to the other end of the conductive grid bar 201. The single chip microcomputer is used to apply a uniform voltage to the conductive grid bars and receive the crack information transmitted by each conductive grid bar through the I / O port. When the crack passes through a conductive path, the conductive path at the corresponding position is broken, and the corresponding I / O port of the single chip microcomputer changes from a low level to a high level. The system can locate the position and length of the crack by monitoring these signal characteristics.

[0063] The present invention determines the crack expansion position by monitoring the on-off state of the conductive path through a single-chip microcomputer, rather than relying on the traditional potential change method. The sensor contains regularly distributed conductive paths, which cover the monitoring area on the surface of the structure. When a crack occurs on the surface of the structure or the crack expands to a specific position, the crack will cut off the corresponding conductive path, causing the path to lose conductivity. By detecting the on-off state of each conductive path, the single-chip microcomputer can accurately locate the expansion position and range of the crack, thereby realizing real-time monitoring of the crack. Compared with the traditional detection method based on potential change, the present invention simplifies the signal processing process through the change of the on-off state, and can provide accurate position information in the early stage of crack expansion.

[0064] The sensor is integrated with the single-chip microcomputer, and the signal acquisition and processing are performed based on the single-chip microcomputer, which greatly simplifies the complex equipment required for the crack sensor in hardware design. Unlike traditional crack sensors that rely on external equipment such as high-precision acquisition cards and DC power supplies, the present invention uses a single-chip microcomputer for direct control and data acquisition, which reduces the dependence on complex hardware, simplifies wiring and system structure, and significantly reduces hardware costs. This makes the system not only more stable and reliable, but also convenient for large-scale promotion and application.

[0065] Furthermore, the grid-type crack sensor also includes a WiFi module, which is integrated with the single-chip microcomputer, so that the single-chip microcomputer communicates with a remote terminal.

[0066] The MCU communicates with the host computer and other terminals through the WiFi module, and forms a monitoring system with the remote terminal. The system has real-time monitoring function and can quickly collect crack signals and process them. In addition, the low power consumption design of the MCU ensures that the system can continue to operate for a long time, which is suitable for the long-term health monitoring needs of structures such as bridges. At the same time, the system adopts a modular architecture design with good scalability and can be linked with other health monitoring equipment. This system architecture design significantly improves the efficiency and practicality of crack monitoring.

[0067] A second aspect of the present invention provides a method for preparing a grid-type crack sensor, such as Figure 4 Shown is a preparation flow chart, comprising the following steps.

[0068] S1, preparing a flexible base layer.

[0069] S2, coating the prepared conductive ink on the flexible base layer by a screen printer and curing at room temperature;

[0070] S3, printing an insulating layer on the flexible base layer;

[0071] S4, coating the prepared conductive ink on the insulating layer by a screen printer and curing at room temperature;

[0072] S5, spraying a protective layer on the insulating layer, or spraying a protective layer on the outermost sensing layer after preparing multiple insulating layers and sensing layers, to obtain a grid-type crack sensor.

[0073] The flexible crack-prone material is used as the flexible base layer of the grid-type crack sensor. The appropriate shape and size of the flexible base layer are designed according to the monitoring structure location and monitoring area to determine the size of the grid-type crack sensor. The sensing layer is prepared by screen printing to ensure the accuracy of the conductive path. First, the first sensing layer is prepared on the flexible base layer by screen printing, and the insulating layer is printed after curing at room temperature. The insulating layer preferably uses modified polyurethane resin, and the first sensing layer is encapsulated between the flexible base layer and the insulating layer. Then, the second sensing layer is prepared on the insulating layer according to the same screen printing process. The conductive grid bars of the second sensing layer and the conductive grid bars of the first sensing layer have different angles, which can be staggered by 30°, 45°, 90°, etc., in order to form a grid structure between the multiple sensing layers.

[0074] If a double-layer grid crack sensor is prepared, the protective layer is sprayed after the second sensing layer is cured at room temperature to complete the lamination of the double-layer grid structure. If a three-layer or more grid crack sensor is prepared, the insulating layer and the sensing layer are printed again in the same way after the second sensing layer is cured at room temperature, and the protective layer is sprayed after the last sensing layer is cured at room temperature. The protective layer is preferably made of anti-corrosion self-spray paint.

[0075] In one embodiment, the conductive ink is a mixture of flake conductive particles and a self-drying ink, such as Figure 5 As shown, its preparation method is:

[0076] Adding a leveling agent to the self-drying ink and stirring evenly to obtain a first mixture;

[0077] Adding flaky conductive particles to the first mixture and stirring evenly to obtain a second mixture;

[0078] Add a curing agent to the second mixture and stir evenly to obtain conductive ink.

[0079] Compared with traditional coating sensors, the multi-layer grid-type crack coating sensor based on screen printing has the following advantages: (1) The screen printing process can achieve high-precision conductive paths and multi-layer structure design, which improves the sensitivity and reliability of crack monitoring; (2) The screen printing process supports large-scale production and can meet the needs of crack monitoring on complex surface shapes; (3) The multi-layer grid structure can provide more reliable electrical signal changes during crack initiation and expansion, significantly improving the monitoring effect; (4) Compared with traditional preparation methods such as thermal spraying, physical vapor deposition, and spraying, screen printing has high preparation efficiency, low cost, and small preparation error, and has superior practical performance for crack monitoring of large structures and large areas.

[0080] A third aspect of the present invention further provides a crack monitoring system, such as Figure 6 The figure is a schematic diagram of the structure of the monitoring system, which includes the grid-type crack sensor, single-chip microcomputer and host computer described in the above-mentioned embodiment of the present invention.

[0081] The structure of the grid crack sensor can be found in Figure 1 As shown, it includes a flexible base layer, at least two sensing layers, an insulating layer and a protective layer. The flexible base layer is used to connect the component to be measured, and the protective layer plays a role in protecting the sensor; at least two sensing layers are arranged between the flexible base layer and the protective layer; the insulating layer is arranged between two adjacent sensing layers; each sensing layer includes a plurality of parallel conductive bars, one end of the plurality of conductive bars is connected by a conductive sheet, and the conductive bars of different sensing layers are staggered to form a grid structure.

[0082] The ground wire of the single chip microcomputer is connected to the conductive sheet at one end of the conductive grid bar, and the I / O port of the single chip microcomputer is connected to the other end of the conductive grid bar, and one I / O port is correspondingly connected to one conductive grid bar.

[0083] The host computer is connected to the single-chip microcomputer and can communicate with the single-chip microcomputer remotely. It can issue instructions, receive collected information, process and analyze the collected information, and issue alarms based on the analysis results.

[0084] Furthermore, the communication module adopts a WiFi module, and the WiFi module is integrated on the single-chip microcomputer to realize wireless transmission of collected data.

[0085] The single-chip computer monitors the changes in the conductive path of the sensor in real time, and transmits the monitoring data to the remote monitoring terminal through the Wi-Fi module. The system can quickly transmit the real-time monitoring structural status information to the host computer through the communication module for further analysis. After receiving the digital signal, the host computer processes the data and converts it into the coordinate information of the crack, calculates the length and extension path of the crack, and displays the crack extension path in the form of a three-dimensional image in real time in the monitoring system, helping users to intuitively observe the crack changes and grasp the crack extension process in time. This process reduces manual intervention, improves monitoring efficiency and accuracy, and provides engineers with real-time and accurate crack data to ensure the safety and reliability of the structure.

[0086] The system supports real-time analysis and storage of data, and realizes automatic early warning in combination with the crack feature database.

[0087] Furthermore, the single chip computer also includes a power supply module for providing a voltage source.

[0088] The monitoring principle of this system is: when a crack passes through a conductive path, the corresponding I / O port of the microcontroller changes from low level to high level, and the system can locate the position and length of the crack by monitoring these signal characteristics. The multi-layer sensor structure enables grids at different levels to respond to different position information of crack extension, thereby achieving more accurate crack assessment.

[0089] The modular design based on single-chip microcomputer supports the coordinated work of multiple sensors, further improving the scalability and application flexibility of the system. By modeling the characteristics of electrical signals and combining the response of multi-layer grids, the limitations of traditional methods for monitoring complex crack paths have been broken. In actual engineering applications, the system can significantly reduce maintenance costs and improve structural safety and service life.

[0090] Experimental verification on steel bridge weld fatigue specimens shows that the crack monitoring system of the present invention can sensitively detect fatigue cracks with a crack length as low as 0.5 mm, and the monitoring accuracy reaches 0.5 mm, meeting the needs of early warning of fatigue cracks in steel bridges.

[0091] The grid-type crack sensor and crack monitoring system of the present invention have strong universality and can be widely used in different industries and structures. In addition to bridges and buildings, it can also be used for structural health monitoring in the fields of aerospace, large machinery, ships, etc. The multi-layer grid-type sensor prepared by screen printing can achieve a wide range of structural surface coverage, and can efficiently monitor crack initiation and expansion in large-area structures such as bridges. Compared with existing crack sensors, it has higher accuracy and flexibility.

[0092] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A grid-type crack sensor, characterized in that: include: A flexible base layer (100) and a protective layer (300), wherein the flexible base layer (100) is used to connect a component to be tested; at least two sensing layers (200), wherein the sensing layers (200) are arranged between the flexible base layer (100) and the protective layer (300); An insulating layer (400) is arranged between two adjacent sensing layers (200); Each sensing layer (200) comprises a plurality of parallel conductive bars (201), one end of the plurality of conductive bars are connected via a conductive sheet (202), and the conductive bars (201) of different sensing layers (200) are staggered to form a grid structure.

2. The grid-type crack sensor according to claim 1, characterized in that: The sensing layer (200) comprises a first sensing layer and at least one second sensing layer; the conductive grid bars (201) and the conductive sheets (202) of the first sensing layer are made by printing conductive ink on the flexible base layer; and the conductive grid bars (201) and the conductive sheets (202) of the second sensing layer are made by printing conductive ink on the insulating layer.

3. The grid-type crack sensor according to claim 2, characterized in that: The conductive ink comprises flake conductive particles and self-drying ink.

4. The grid-type crack sensor according to claim 2, characterized in that: There is one second sensing layer, and the conductive grids of the first sensing layer and the second sensing layer are perpendicular to each other.

5. The grid-type crack sensor according to any one of claim 2, characterized in that: The material of the insulating layer (400) is modified polyurethane resin.

6. The grid-type crack sensor according to any one of claims 1 to 5, characterized in that: The material of the protective layer (300) is anti-corrosion self-spraying paint.

7. The grid-type crack sensor according to any one of claims 1 to 5, characterized in that: The grid-type crack sensor further comprises a single-chip microcomputer (500), a ground line of the single-chip microcomputer (500) being connected to the conductive sheet (202), and an I / O port of the single-chip microcomputer being connected to the other end of the conductive grid bar (201) for receiving crack information.

8. The grid-type crack sensor according to claim 7, characterized in that: The grid-type crack sensor further comprises a WiFi module, which is integrated with the single-chip microcomputer so as to enable the single-chip microcomputer (500) to communicate with a remote terminal.

9. The method for preparing the grid-type crack sensor according to any one of claims 1 to 8, characterized in that: include: S1, preparing a flexible base layer; S2, coating the prepared conductive ink on the flexible base layer by a screen printer and curing at room temperature; S3, printing an insulating layer on the flexible base layer; S4, coating the prepared conductive ink on the insulating layer by a screen printer and curing at room temperature; S5, spraying a protective layer on the insulating layer, or spraying a protective layer on the outermost sensing layer after preparing multiple insulating layers and sensing layers, to obtain a grid-type crack sensor.

10. The method for preparing the grid-type crack sensor according to claim 9, characterized in that: The preparation method of the conductive ink is: Adding a leveling agent to the self-drying ink and stirring evenly to obtain a first mixture; Adding flaky conductive particles to the first mixture and stirring evenly to obtain a second mixture; A curing agent is added to the second mixture, and the mixture is stirred evenly to obtain the conductive ink.

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