Center twisting type ultra-weak fiber bragg grating temperature and humidity stranded yarn and application method thereof

Abstract

The invention relates to a center twisting type ultra-weak fiber bragg grating temperature and humidity stranded yarn and an application method thereof.A humidity ultra-weak fiber bragg grating array is adopted, the temperature ultra-weak fiber bragg grating array and Kevlar fibers are combined and then wrap a spiral armor pipe, and then a metal wire braid layer is woven in the axial direction to form a temperature and humidity intelligent monofilament; the temperature and humidity intelligent monofilament serves as a center filament and is twisted with the six stainless steel wires to form a cable shape, and the temperature and humidity stranded filament of the ultra-weak fiber grating is manufactured. The long-distance temperature and humidity ultra-weak fiber grating array is adopted to monitor temperature and humidity, temperature compensation is facilitated, temperature and humidity changes can be quickly responded, the filamentation porosity is large, the response speed is high, the mechanical strength is high, adaptability is high, and follow-up machining is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering monitoring, and particularly relates to a central twisted ultra-weak optical fiber grating temperature and humidity 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 a center-twisted ultra-weak fiber Bragg grating temperature and humidity strand and its application method, so as to solve the problems of low safety, complex manufacturing process, low porosity and single detection parameters 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 a central twisted ultra-weak fiber Bragg grating temperature and humidity 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 metal wire braid layer, and a stainless steel wire; The humidity ultra-weak fiber grating array, the temperature ultra-weak fiber grating array and the Kevlar fiber are bundled together and wrapped around the spiral armor tube, and then the metal wire braided layer is woven axially to form a temperature and humidity smart monofilament; the temperature and humidity smart monofilament is used as the central wire and twisted with the six stainless steel wires into a rope shape to make the temperature and humidity strands of the ultra-weak fiber grating.

[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 armored tube has a wall thickness of 0.25 mm, is formed by spiral winding of high-strength steel belt, and has a pitch of 3 mm; the metal wire braided layer is woven from stainless steel wire with a diameter of 0.2 mm-0.3 mm, which is used to improve the tensile properties of the spiral armored tube. The wall thickness of the spiral armored tube is 0.12 mm, is formed by spiral winding of stainless steel belt, and has a pitch of 3 mm.

[0011] Preferably, the humidity ultra-weak fiber grating array and the temperature ultra-weak fiber grating array have a diameter of no more than 0.25 mm, a grating pitch of 0.1 m-1 m, gratings with central wavelengths of 1550 nm and 1548 nm are alternately written, the grating type is an ultra-weak grating, the grating manufacturing process is lossless writing, and the grating coating is not damaged.

[0012] A second aspect of the present invention provides an application method of a center-twisted ultra-weak fiber Bragg grating temperature and humidity strand, which specifically comprises the following steps: Step 1: Bundle the Kevlar fiber, the humidity ultra-weak fiber grating array and the temperature ultra-weak fiber grating array, wrap them with a spiral armor tube, and then weave a metal wire braided layer along the axial direction to form a temperature and humidity smart monofilament; Step 2: Using the temperature and humidity single wire as the central wire, twisting six stainless steel wires to make an ultra-weak fiber grating array temperature and humidity strand wire; Step 3: The ultra-weak fiber grating array temperature and humidity strand is used as the central wire and bundled with other 90 high-strength stainless steel wires to form a cable strand, and the anchor head is cast to form a smart cable strand; Step 4: The smart cable strand is hoisted by two traction belts, so that the smart cable strand is suspended on the traction cable without generating a large bending amplitude, thereby protecting the smart temperature and humidity sensor strand of the ultra-weak fiber Bragg grating during the hanging process. The smart cable strand is pulled by the above method and anchored to become a part of the main cable of the bridge; Step 5: Use the cable gripper to install other common cable strands through the traction cable in sequence, and one smart cable strand and other common cable strands together form the main cable of the bridge; Step six, 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, especially the smart cables. Use the sensor system of the ultra-weak fiber grating smart temperature and humidity sensing strands to conduct preliminary collection and calibration of temperature and humidity data to ensure that the sensitivity and accuracy of the sensor system meet the design requirements.

[0013] Compared with the existing methods, the central twisted ultra-weak fiber Bragg grating temperature and humidity strand and its application method provided by the present invention have the following beneficial effects: (1) Large porosity, fast response speed and high mechanical strength The long-distance temperature and humidity ultra-weak fiber grating array is used to monitor temperature and humidity, which is convenient for temperature compensation and can quickly respond to changes in temperature and humidity; the sensing optical fiber is coated with spiral armor and the metal braided structure has a large porosity, and is twisted around the central stainless steel wire, which is convenient for temperature and humidity exchange with the external environment, ensuring 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; (2) Strong adaptability and convenient for subsequent processing The twisted steel wire structure can be stretched directly in the cable, which significantly enhances the adaptability and stability of the sensor in complex environments. The outer braided layer can prevent the temperature and humidity smart monofilament from being squeezed out of the slot, adapting to the working conditions of cable formation and hanging cable.

[0014] (3) Simple structure 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 costs. This simple structure and production process greatly reduces production costs, improves manufacturing efficiency, and has the potential for large-scale promotion and application, thereby further enhancing the practicality and economy of the present invention in the field of bridge monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic structural diagram of an embodiment of a center-twisted ultra-weak fiber Bragg grating temperature and humidity strand provided by the present invention.

[0016] 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.

[0017] Figure 3 The present invention provides a schematic structural diagram of an embodiment of a domestic suspension bridge.

[0018] In the above drawings: 1. reinforced concrete structure of the bridge; 2. main cable of the bridge; 21. ultra-weak fiber grating multi-parameter sensing smart strand; 211. humidity ultra-weak fiber grating array; 212. temperature ultra-weak fiber grating array; 213. the Kevlar fiber; 214. spiral armor tube; 215. spiral armor braided layer; 216. outer stainless steel wire; 22. high-strength stainless steel wire. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with specific implementation modes.

[0020] This embodiment provides a central twisted ultra-weak fiber Bragg grating temperature and humidity 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 metal wire braided layer 215, and a stainless steel wire 216; 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 around the spiral armor tube 214, and then the metal wire braided layer 215 is woven axially to form a temperature and humidity smart monofilament; the temperature and humidity smart monofilament is used as the central wire and twisted with the six stainless steel wires 216 into a rope shape to make the temperature and humidity strands of the ultra-weak fiber grating.

[0021] 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.

[0022] Among them, the coating thickness of common polyimide and moisture-sensitive polyimide materials is 10 um.

[0023] 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.

[0024] 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.

[0025] In other preferred embodiments, the spiral armor tube 214 has a wall thickness of 0.25 mm and is formed by spiral winding of a high-strength steel belt with a pitch of 3 mm; the metal wire braided layer 215 is woven from stainless steel wire with a diameter of 0.2 mm-0.3 mm to improve the tensile performance of the spiral armor tube, and the wall thickness of the spiral armor tube 214 is 0.12 mm.

[0026] In some embodiments, the diameter of the humidity ultra-weak fiber grating array 211 and the temperature ultra-weak fiber grating array 212 is not greater than 0.25 mm, the grating pitch is 0.1m-1m, the gratings with central wavelengths of 1550nm and 1548nm are alternately engraved, the grating type is ultra-weak grating, the grating manufacturing process is lossless writing, and the grating coating is not damaged.

[0027] As another preferred embodiment of the present invention, Figure 1-3 As shown, this embodiment provides an application method of a center-twisted ultra-weak fiber Bragg grating temperature and humidity strand, which is characterized by specifically comprising the following steps: Step 1: Bundle the Kevlar fiber filament 213, the humidity ultra-weak fiber grating array 211 and the temperature ultra-weak fiber grating array 212, wrap them with a spiral armor tube 214, and then weave a metal wire braided layer 215 along the axial direction to form a temperature and humidity smart monofilament; Step 2: Using the temperature and humidity monofilament as the central wire, twisting six stainless steel wires 216 to make ultra-weak fiber grating array temperature and humidity strands; Step 3: The ultra-weak fiber grating array temperature and humidity strand 21 is used as the central strand and bundled with other 90 high-strength stainless steel wires 22 to form a cable strand, and an anchor head is cast to form a smart cable strand; Step 4: The smart cable strand is hoisted by two traction belts, so that the smart cable strand is suspended on the traction cable without generating a large bending amplitude, thereby protecting the smart temperature and humidity sensor strand of the ultra-weak fiber Bragg grating during the hanging process. The smart cable strand is pulled by the above method and anchored to become a part of the main cable 2 of the bridge; Step 5: Use a cable gripper to install other common cable strands through the traction cable in sequence, and a smart cable strand and other common cable strands together form the main cable 2 of the bridge; Step six, 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, especially the smart cable. Then the main cable 2 of the bridge and the reinforced concrete structure 1 of the bridge together form a domestic suspension bridge. The sensor system of the ultra-weak fiber grating smart temperature and humidity sensing strands 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.

[0028] In the measurement process of the present invention, when the external temperature changes, the ultra-weak fiber grating is affected by the thermo-optical effect and the thermal expansion of the acrylic resin 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 211 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; In the application of the present invention, the temperature and humidity measurement range and measurement accuracy of the sensor array can also be adjusted by adjusting the thickness of the moisture-sensitive polyimide material or the non-moisture-sensitive material coating layer.

[0029] 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. A center-twisted ultra-weak fiber Bragg grating temperature and humidity 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), metal wire braid layer (215), stainless steel wire (216); 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 around the spiral armor tube (214), and then the metal wire braided layer (215) is woven axially to form a temperature and humidity intelligent monofilament; the temperature and humidity intelligent monofilament is used as a central wire and twisted with six stainless steel wires (216) to form a rope shape to form the temperature and humidity strands of the ultra-weak fiber grating.

2. The central twisted ultra-weak fiber Bragg grating temperature and humidity 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 common polyimide once and then coated with humidity-sensitive polyimide material twice.

3. A center-twisted ultra-weak fiber Bragg grating temperature and humidity strand according to claim 2, characterized in that: The coating thickness of common polyimide and moisture sensitive polyimide materials is 10 um.

4. The central twisted ultra-weak fiber Bragg grating temperature and humidity strand according to claim 1, characterized in that: The temperature ultra-weak fiber grating array (212) is prepared by coating an ultra-weak fiber grating with an acrylic coating once.

5. The central twisted ultra-weak fiber Bragg grating temperature and humidity 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 central twisted ultra-weak fiber Bragg grating temperature and humidity strand according to claim 1, characterized in that: The spiral armor tube (214) has a wall thickness of 0.25 mm and is formed by spirally winding a high-strength steel strip, with a pitch of 3 mm; the metal wire braided layer (215) is woven from stainless steel wires with a diameter of 0.2 mm-0.3 mm, and is used to improve the tensile strength of the spiral armor tube; the spiral armor tube (214) has a wall thickness of 0.12 mm and is formed by spirally winding a stainless steel strip, with a pitch of 3 mm.

7. The central twisted ultra-weak fiber Bragg grating temperature and humidity strand according to claim 1, characterized in that: The humidity ultra-weak fiber grating array (211) and the temperature ultra-weak fiber grating array (212) have a diameter of no more than 0.25 mm, a grating pitch of 0.1 m-1 m, gratings with central wavelengths of 1550 nm and 1548 nm are alternately written, the grating type is an ultra-weak grating, the grating manufacturing process is lossless writing, and the grating coating layer is not damaged.

8. The center-twisted ultra-weak fiber Bragg grating temperature and humidity strand according to claim 1, characterized in that: The diameter of the stainless steel wire (216) is consistent with that of the temperature and humidity smart monofilament.

9. The application method of the center-twisted ultra-weak fiber Bragg grating temperature and humidity strand according to claims 1-8, characterized in that: The specific steps include: Step 1: Bundle the Kevlar fiber (213), the humidity ultra-weak fiber grating array (211), and the temperature ultra-weak fiber grating array (212), wrap them with a spiral armor tube (214), and then weave a metal wire braided layer (215) along the axial direction to form a temperature and humidity smart monofilament; Step 2: Using the temperature and humidity single wire as the central wire, twisting six stainless steel wires (216) to make an ultra-weak fiber grating array temperature and humidity strand wire; Step 3: The ultra-weak fiber grating array temperature and humidity strand (21) is used as the central strand and bundled with other 90 high-strength stainless steel wires (22) to form a cable strand, and an anchor head is cast to form a smart cable strand; Step 4: The smart cable strand is hoisted by two traction belts, so that the smart cable strand is suspended on the traction cable without generating a large bending amplitude, thereby protecting the smart temperature and humidity sensor strand of the ultra-weak fiber Bragg grating during the hanging process. The smart cable strand is pulled by the above method and anchored to become a part of the main cable of the bridge; Step 5: Use the cable gripper to install other common cable strands through the traction cable in sequence, and one smart cable strand and other common cable strands together form the main cable of the bridge; Step six, 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, especially the smart cables. Use the sensor system of the ultra-weak fiber grating smart temperature and humidity sensing strands to conduct 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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