Ultra-weak fiber grating multi-parameter sensing strand and application method thereof

Abstract

The invention relates to an ultra-weak fiber bragg grating multi-parameter sensing strand and an application method thereof. A humidity ultra-weak fiber bragg grating array, a temperature ultra-weak fiber bragg grating array and Kevlar fibers are combined and then wrapped with a spiral armor tube, and then a spiral armor braid layer is braided in the length direction to form a temperature and humidity intelligent monofilament; performing hot pultrusion on the strain weak fiber grating array, the carbon fiber layer and the glass fiber layer to prepare a strain intelligent center wire; twisting the temperature and humidity intelligent monofilament and a plurality of outer-layer stainless steel wires into a strain intelligent center wire to form a rope shape, and weaving a strand woven layer along the length direction. According to the invention, while high porosity is maintained, multi-parameter monitoring of stress strain, temperature and humidity is realized, the strength of the sensor is obviously improved, and the manufacturing process is simplified; the ultra-weak fiber grating sensing technology is adopted, accurate temperature and humidity monitoring can be achieved in a complex environment, durability and stability are achieved, and the system is suitable for long-term bridge structure monitoring.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering monitoring, and particularly relates to an ultra-weak fiber grating multi-parameter sensing strand and an application method thereof. Background Art

[0002] In the monitoring of large bridges, fiber optic sensors have become an ideal choice for long-term monitoring of bridge structures due to their small size, light weight, high sensitivity, and strong anti-electromagnetic interference capabilities. However, the application of traditional steel wire fiber optic sensors in bridge monitoring still faces several challenges, especially in humidity sensing, where the porosity of the sensor has an important impact on its performance. Low porosity will lead to poor temperature and humidity exchange efficiency between the sensor and the external environment, thus affecting the accuracy and real-time performance of the measurement. Although increasing the porosity can improve the environmental responsiveness of the sensor, it often leads to a decrease in the strength of the steel pipe, which in turn affects the reliability of the overall structure. In addition, in order to improve the strength of the steel pipe, higher-cost materials are usually required, which not only increases the production cost, but also makes the manufacturing process more complicated, limiting large-scale production and promotion and application.

[0003] In this regard, Zhang Yibo and others proposed a solution to improve accuracy through complex mechanical structures and thermal insulation devices in their invention patent with publication number CN114485451A applied in 2022, a high-precision fiber Bragg grating stress and strain sensor. However, the manufacturing process of this solution is complicated, involving the installation, adjustment and use of inert gas of multiple components. The production process is cumbersome and not conducive to multi-parameter monitoring of fiber Bragg grating sensors. In addition, the compressive and tensile strength of the sensor is not ideal, especially in complex working environments, the strength of the mechanical structure may not be sufficient to ensure long-term stability. Zhang Hong and others proposed an improved fiber optic sensor structure in their utility model patent with publication number CN217358614U applied in 2022, a digital steel wire for measuring the full range of temperature and humidity of the cable structure, but the invention adopts the design of an outer jacket steel pipe with a low porosity, which is not conducive to sufficient temperature and humidity exchange with the external environment. At the same time, in order to improve the temperature and humidity exchange effect, excessive perforation of the outer jacket steel pipe structure may weaken the overall strength of the sensor. In addition, in the patent applied for by Zhang Dongyu and others in 2024, a temperature and humidity self-sensing bridge main cable intelligent steel wire optical fiber sensor and its design and application method, although the manufacturing process was further optimized and the manufacturing efficiency of the sensor was improved, the safety of the manufacturing process was reduced. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an ultra-weak fiber Bragg grating multi-parameter sensing strand and its application method, so as to solve the problems of low safety, complex manufacturing process, low porosity and single detection parameter in the manufacturing process of the prior art. Through innovative structural design, the present invention realizes multi-parameter monitoring of stress strain, temperature and humidity while maintaining high porosity, significantly improves the strength of the sensor, and simplifies the manufacturing process. The invention adopts ultra-weak fiber Bragg grating sensing technology, which can not only realize accurate temperature and humidity monitoring in complex environments, but also has durability and stability, and is suitable for long-term bridge structure monitoring. At the same time, the manufacturing process of the present invention is simple and efficient, which reduces production costs and has the potential for large-scale promotion and application, thereby providing a reliable and economical solution for the field of bridge monitoring.

[0005] The first aspect of the present invention provides an ultra-weak fiber Bragg grating multi-parameter sensing strand, comprising: a humidity ultra-weak fiber Bragg grating array, a temperature ultra-weak fiber Bragg grating array, Kevlar fiber, a spiral armor tube, a spiral armor braided layer, a strain-weak fiber Bragg grating array, a carbon fiber layer, a glass fiber layer, an outer stainless steel wire and a strand braided layer; The humidity ultra-weak fiber grating array, the temperature ultra-weak fiber grating array and the Kevlar fiber are bundled together and wrapped with the spiral armor tube, and then the spiral armor braided layer is woven along the length direction to form a temperature and humidity smart monofilament; the strain-weak fiber grating array, the carbon fiber layer and the glass fiber layer are formed by hot pultrusion to form a strain-wise central wire; The temperature and humidity smart monofilament is twisted with a plurality of the outer stainless steel wires to form a strain smart central wire, which is then twisted into a rope shape, and then a strand braided layer is woven along the length direction.

[0006] Preferably, the humidity ultra-weak fiber grating array is made of a thin-diameter ultra-weak fiber grating that is coated with ordinary polyimide once and then coated with humidity-sensitive polyimide material twice.

[0007] Preferably, the coating thickness of the common polyimide and moisture sensitive polyimide materials is 10 um.

[0008] Preferably, the temperature ultra-weak fiber grating array is prepared by coating an ultra-weak fiber grating with an acrylic coating once.

[0009] Preferably, the Kevlar fiber is made of high-strength polyamide fiber with a diameter of 50 um and is a continuous filament without breakage or entanglement during the bundling process.

[0010] Preferably, the spiral armor braided layer is woven from stainless steel wire with a diameter of 0.2 mm and is wrapped around the spiral armor tube to enhance the tensile strength of the spiral armor tube.

[0011] Preferably, the carbon fiber layer is composed of 28 bundles of 12K carbon fiber bundles, whose tensile strength is not less than 2800Mpa and elongation at break is 2%; the glass fiber layer is composed of 4 bundles of 600 tex glass fiber bundles, whose tensile strength is not less than 2000MPa and elongation at break is 2%.

[0012] Preferably, the temperature and humidity smart monofilament adopts an empty sleeve structure, so that the humidity ultra-weak fiber grating array and the temperature ultra-weak fiber grating array can slide freely in the empty sleeve structure, thereby eliminating the influence of stress and strain on temperature and humidity measurement.

[0013] Preferably, the strand braided layer is woven from stainless steel wire with a diameter of 0.2 mm, and is used to prevent the temperature and humidity smart single wire from escaping from the slot and being squeezed and damaged by other structures.

[0014] A second aspect of the present invention provides an application method of ultra-weak fiber Bragg grating multi-parameter sensing strand, characterized in that it specifically comprises the following steps: In the first step, the humidity ultra-weak fiber grating array, the temperature ultra-weak fiber grating array and the Kevlar fiber are bundled and then wrapped with a spiral armor tube, and then the spiral armor braided layer is woven along the length of the cable body to form a temperature and humidity smart monofilament; the strain-weak fiber grating array is coated with a carbon fiber layer, and then a glass fiber layer is wrapped on the outer layer, fixed with an impregnated adhesive, and heated to form a stress-strain smart central wire; In the second step, the temperature and humidity smart monofilament and five outer stainless steel wires are twisted with a stress-strain smart central wire to form a rope shape, and then the outer braided layer strands are braided along the length direction as a protective layer to form an ultra-weak fiber Bragg grating multi-parameter sensing strand; In the third step, the ultra-weak fiber Bragg grating multi-parameter sensing smart strand is used as the central wire and bundled with other 90 high-strength stainless steel wires to form a cable strand, and then the anchor head is cast to form a smart cable strand; In the fourth step, the smart cable strand is pulled to control the bending amplitude of the cable strand, and the ultra-weak fiber Bragg grating multi-parameter strand is protected during the hanging process, and is anchored to become a component of the main cable of the bridge; Step 5: Use the cable gripper to install the other 216 ordinary cable strands through the traction cable in sequence. One smart cable strand and the other 216 ordinary cable strands together form the main cable of the bridge. The sixth step is to calibrate the tension of the installed main cable of the bridge and measure the tension of all cables to ensure that each cable is evenly stressed. After the main cable and the reinforced concrete structure of the bridge are installed, the temperature and humidity data are preliminarily collected and calibrated through the ultra-weak fiber grating multi-parameter sensing smart cable sensor system to ensure that the sensitivity and accuracy of the sensor system meet the design requirements.

[0015] Compared with the existing methods, the ultra-weak fiber Bragg grating temperature and humidity sensing smart strand and its application method provided by the present invention have the following beneficial effects: (1) Multi-parameter monitoring to significantly reduce the number of strands The functions of two or more traditional sensing strands are concentrated on one strand, which greatly reduces the number of expensive strands. The large-scale monitoring of temperature, humidity and strain on the same strand can avoid the differences in monitoring of multiple strands, perform temperature compensation well, and reduce the cross-influence of temperature on strain and humidity.

[0016] (2) Large porosity and fast temperature and humidity response The sensing optical fiber is coated with a spiral armor and a metal braided structure, which has a large porosity and is twisted on the outside of the strands, which facilitates the exchange of temperature and humidity with the external environment, improves the temperature and humidity response speed, and ensures real-time and accurate monitoring of temperature and humidity data; Kevlar fiber is introduced to bundle with the sensing optical fiber, and the combined optical fiber can well avoid local excessive stretching; the spiral armor is braided with metal wire to improve the tensile strength of the spiral armor tube; (3) High tensile strength and stable mechanical properties The use of carbon fiber / glass fiber to composite the ultra-weak fiber grating array effectively reduces the impact of thermal expansion and ensures the long-term working life of the sensor. The composite material has high tensile strength, stable mechanical properties, high stress transfer efficiency, and can monitor the strain distribution of the cable with high precision.

[0017] (4) Simple structure and high cost performance The processes of bundling, armoring and twisting used in the strand processing are all used in batches in traditional optical cable processing, with mature production and low manufacturing cost. This simple structure and production process reduces production costs, improves manufacturing efficiency, and enhances the practicality and economy of the present invention in the field of bridge monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic structural diagram of an embodiment of an ultra-weak fiber Bragg grating multi-parameter sensing strand provided by the present invention.

[0019] Figure 2 This is a structural schematic diagram of an embodiment of a smart cable strand of a domestic suspension bridge provided by the present invention.

[0020] Figure 3 The present invention provides a schematic structural diagram of an embodiment of a domestic suspension bridge.

[0021] In the above drawings: 1. reinforced concrete structure of the bridge; 2. main cable of the bridge; 21. ultra-weak fiber Bragg grating multi-parameter sensing smart strand; 211. ultra-weak humidity fiber Bragg grating array; 212. ultra-weak temperature fiber Bragg grating array; 213. Kevlar fiber; 214. spiral armor tube; 215. spiral armor braided layer; 216. strain-weak fiber Bragg grating array; 217. carbon fiber layer; 218. glass fiber layer; 22. high-strength stainless steel wire. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with specific implementation modes.

[0023] This embodiment provides an ultra-weak fiber Bragg grating multi-parameter sensing strand, such as Figure 1-Figure 2 As shown, it includes: a humidity ultra-weak fiber grating array 211, a temperature ultra-weak fiber grating array 212, a Kevlar fiber 213, a spiral armor tube 214, a spiral armor braided layer 215, a strain-weak fiber grating array 216, a carbon fiber layer 217, a glass fiber layer 218, an outer stainless steel wire 219 and a strand braided layer 2110; The humidity ultra-weak fiber grating array 211, the temperature ultra-weak fiber grating array 212 and the Kevlar fiber 213 are bundled together and wrapped with the spiral armor tube 214, and then the spiral armor braided layer (215) is woven along the length direction to form a temperature and humidity smart monofilament; the strain-weak fiber grating array 216, the carbon fiber layer 217, and the glass fiber layer 218 are formed by hot pultrusion to form a strain-wise central filament; The temperature and humidity smart monofilament and the plurality of outer stainless steel wires 219 are twisted with a strain smart central wire, twisted into a rope shape, and then a strand braided layer 2110 is woven along the length direction.

[0024] In the above embodiment, the humidity ultra-weak fiber grating array 211 is made of a thin-diameter ultra-weak fiber grating that is coated with ordinary polyimide once and then coated with humidity-sensitive polyimide material twice.

[0025] Among them, the coating thickness of common polyimide and moisture-sensitive polyimide materials is 10 um.

[0026] In some embodiments, the temperature ultra-weak fiber grating array 212 is prepared by coating an ultra-weak fiber grating with an acrylic coating once.

[0027] In some preferred embodiments, the Kevlar fiber 213 is made of high-strength polyamide fiber with a diameter of 50 um and is a continuous filament without breakage or entanglement during the bundling process.

[0028] In some other preferred embodiments, the spiral armor braided layer 215 is woven from stainless steel wires with a diameter of 0.2 mm and is wrapped around the spiral armor tube 214 to enhance the tensile strength of the spiral armor tube 214 .

[0029] In some preferred embodiments, the carbon fiber layer 217 is composed of 28 bundles of 12K carbon fiber bundles, whose tensile strength is not less than 2800 MPa and whose elongation at break is 2%; the glass fiber layer 218 is composed of 4 bundles of 600 tex glass fiber bundles, whose tensile strength is not less than 2000 MPa and whose elongation at break is 2%.

[0030] In some embodiments, the temperature and humidity smart monofilament adopts an empty sleeve structure, so that the humidity ultra-weak fiber grating array 211 and the temperature ultra-weak fiber grating array 212 can slide freely in the empty sleeve structure, thereby eliminating the influence of stress and strain on temperature and humidity measurement.

[0031] In other embodiments, the strand braided layer 2110 is woven from stainless steel wire with a diameter of 0.2 mm, and is used to prevent the temperature and humidity smart monofilament from escaping from the slot and being squeezed and damaged by other structures.

[0032] As another preferred embodiment of the present invention, this embodiment provides an application method of ultra-weak fiber Bragg grating multi-parameter sensing strand, characterized in that it specifically includes the following steps: In the first step, the humidity ultra-weak fiber grating array 211, the temperature ultra-weak fiber grating array 212 and the Kevlar fiber 213 are bundled and then wrapped with a spiral armor tube 214, and then a spiral armor braided layer 215 is woven along the length direction of the cable body to form a temperature and humidity smart monofilament; a carbon fiber layer 217 is coated on the outside of the strain-weak fiber grating array 216, and a glass fiber layer 218 is wrapped on the outer layer, fixed with an impregnated adhesive, and heated to form a stress-strain smart central wire; In the second step, the temperature and humidity smart monofilament and five outer stainless steel wires 219 are twisted with a stress-strain smart central wire to form a rope shape, and then an outer braided layer strand braided layer 2110 is woven along the length direction as a protective layer to form an ultra-weak fiber Bragg grating multi-parameter sensing strand; The third step is to use the ultra-weak fiber Bragg grating multi-parameter sensing smart strand 21 as the central wire and bundle it with other 90 high-strength stainless steel wires 22 to form a cable strand, and then cast an anchor head to form a smart cable strand; In the fourth step, the smart cable strand is pulled to control the bending amplitude of the cable strand, and the ultra-weak fiber Bragg grating multi-parameter strand is protected during the hanging process, and is anchored to become a component of the main cable of the bridge; Step 5: Use the cable gripper to install the other 216 ordinary cable strands through the traction cable in sequence, and one smart cable strand and the other 216 ordinary cable strands together form the main cable 2 of the bridge; The sixth step is to calibrate the tension of the installed main cable 2 of the bridge and measure the tension of all cables to ensure that each cable is evenly stressed. After the installation of the main cable 2 and the reinforced concrete structure 1 of the bridge is completed, the temperature and humidity data are preliminarily collected and calibrated through the ultra-weak fiber grating multi-parameter sensing smart cable sensor system to ensure that the sensitivity and accuracy of the sensor system meet the design requirements.

[0033] During measurement, when the external temperature changes, the ultra-weak fiber grating is affected by the thermo-optical effect and the thermal expansion of the acrylic coating, causing the central wavelength of the ultra-weak fiber grating to change, thereby realizing the measurement of the external temperature change; when the external humidity changes, the humidity-sensitive polyimide material of the humidity ultra-weak fiber grating array expands or contracts, causing the central wavelength of the thin-diameter ultra-weak fiber grating to change, and the external humidity change is measured according to the change in the central wavelength of the thin-diameter ultra-weak fiber grating.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. An ultra-weak fiber Bragg grating multi-parameter sensing strand, characterized in that: It includes: humidity ultra-weak fiber Bragg grating array (211), temperature ultra-weak fiber Bragg grating array (212), Kevlar fiber (213), spiral armor tube (214), spiral armor braided layer (215), strain-weak fiber Bragg grating array (216), carbon fiber layer (217), glass fiber layer (218), outer stainless steel wire (219) and strand braided layer (2110); The humidity ultra-weak fiber grating array (211), the temperature ultra-weak fiber grating array (212) and the Kevlar fiber (213) are bundled together and then wrapped with the spiral armor tube (214), and then the spiral armor braided layer (215) is woven along the length direction to form a temperature and humidity smart monofilament; the strain-weak fiber grating array (216) and the carbon fiber layer (217) and the glass fiber layer (218) are formed by hot pultrusion to form a strain-intelligent central filament; The temperature and humidity smart single wire and a plurality of the outer stainless steel wires (219) are twisted with a strain smart central wire, twisted into a rope shape, and then a strand braided layer (2110) is woven along the length direction.

2. The ultra-weak fiber Bragg grating multi-parameter sensing strand according to claim 1, characterized in that: The humidity ultra-weak fiber grating array (211) is made of a thin-diameter ultra-weak fiber grating that is coated with ordinary polyimide once and then coated with humidity-sensitive polyimide material twice.

3. The ultra-weak fiber Bragg grating multi-parameter sensing strand according to claim 2, characterized in that: The coating thickness of common polyimide and moisture sensitive polyimide materials is 10 um.

4. The ultra-weak fiber Bragg grating multi-parameter sensing strand according to claim 1, characterized in that: The temperature ultra-weak fiber grating array (212) is prepared by coating the ultra-weak fiber grating with an acrylic resin coating once.

5. The ultra-weak fiber Bragg grating multi-parameter sensing strand according to claim 1, characterized in that: The Kevlar fiber (213) is made of high-strength polyamide fiber, has a diameter of 50 μm, is a continuous filament, and has no breakage or entanglement during the bundling process.

6. The ultra-weak fiber Bragg grating multi-parameter sensing strand according to claim 1, characterized in that: The spiral armor braided layer (215) is braided from stainless steel wire with a diameter of 0.2 mm and is wrapped around the spiral armor tube (214) to enhance the tensile strength of the spiral armor tube (214).

7. The ultra-weak fiber Bragg grating multi-parameter sensing strand according to claim 1, characterized in that: The carbon fiber layer (217) is composed of 28 bundles of 12K carbon fiber bundles, the tensile strength of which is not less than 2800 MPa, and the elongation at break is 2%. The glass fiber layer (218) is composed of 4 bundles of 600 tex glass fiber bundles, the tensile strength of which is not less than 2000 MPa, and the elongation at break is 2%.

8. The ultra-weak fiber Bragg grating multi-parameter sensing strand according to claim 1, characterized in that: The temperature and humidity intelligent monofilament adopts an empty sleeve structure, so that the humidity ultra-weak fiber grating array (211) and the temperature ultra-weak fiber grating array (212) can slide freely in the empty sleeve structure, thereby eliminating the influence of stress and strain on temperature and humidity measurement.

9. The ultra-weak fiber Bragg grating multi-parameter sensing strand according to claim 1, characterized in that: The strand braided layer (2110) is woven from stainless steel wire with a diameter of 0.2 mm, and is used to prevent the temperature and humidity intelligent single wire from escaping from the slot and being squeezed and damaged by other structures.

10. The application method of the ultra-weak fiber Bragg grating multi-parameter sensing strand according to claims 1 to 9, characterized in that: The specific steps include: In the first step, a humidity ultra-weak fiber grating array (211), a temperature ultra-weak fiber grating array (212) and a Kevlar fiber (213) are bundled together and then wrapped with a spiral armor tube (214), and then a spiral armor braided layer (215) is woven along the length direction of the cable body to form a temperature and humidity smart monofilament; a carbon fiber layer (217) is coated on the outside of the strain-weak fiber grating array (216), and a glass fiber layer (218) is wrapped on the outside, fixed with an impregnated adhesive, and heated to form a stress-strain smart central wire; The second step is to twist the temperature and humidity smart single wire and five outer stainless steel wires (219) with a stress-strain smart central wire to form a rope shape, and then weave an outer braided layer of strands (2110) along the length direction as a protective layer to form an ultra-weak fiber Bragg grating multi-parameter sensing strand; The third step is to use the ultra-weak fiber Bragg grating multi-parameter sensing smart strand (21) as the central wire and bundle it with other 90 high-strength stainless steel wires (22) to form a cable strand, and then cast an anchor head to form a smart cable strand; In the fourth step, the smart cable strand is pulled to control the bending amplitude of the cable strand, and the ultra-weak fiber Bragg grating multi-parameter strand is protected during the hanging process, and is anchored to become a component of the main cable of the bridge; Step 5: Use a cable gripper to install the other 216 ordinary cable strands through the traction cable in sequence, so that one smart cable strand and the other 216 ordinary cable strands together form the main cable of the bridge (2); The sixth step is to calibrate the tension of the main cable (2) of the bridge that has been installed, and measure the tension of all cable strands to ensure that the force on each cable strand is uniform. After the main cable (2) of the bridge and the reinforced concrete structure (1) of the bridge are installed, the sensor system of the ultra-weak fiber Bragg grating multi-parameter sensing smart strand is used to perform preliminary collection and calibration of temperature and humidity data to ensure that the sensitivity and accuracy of the sensor system meet the design requirements.

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