A fiber grating strain sensor for a bolt

Abstract

The utility model relates to sensor technical field discloses a kind of fiber grating strain sensors for bolt, including the steel pipe for supporting and protection, the detection component for detecting bolt strain is installed in the steel pipe, the protection component for protecting detection component is installed in the both ends of steel pipe.The utility model is fixed in the bolt inner hole to be detected using special glue with steel pipe, the strain of bolt is directly transmitted to fiber grating by special glue, the strain of fiber grating is measured to reflect the strain of bolt, the anti-electromagnetic interference characteristics of fiber grating ensure stable monitoring under complex working condition, steel pipe structure optimizes stress transmission efficiency and protects fiber grating from mechanical damage, both guarantee long-term stability under dynamic load, adapt to wide temperature range environment, and this embedded design improves the accuracy of bolt health monitoring.

Description

Technical Field

[0001] This utility model relates to the field of sensor technology, specifically to a fiber optic strain sensor for bolts. Background Technology

[0002] Fiber Bragg grating strain sensors are a sensing technology based on the principle that the reflected wavelength of fiber Bragg gratings changes linearly with strain. Their core advantages are resistance to electromagnetic interference, corrosion resistance, and the ability to achieve distributed measurement. They have been widely used in structural health monitoring in aerospace, bridge and tunnel fields. In the field of mechanical fasteners, bolts are key load-bearing components, and their strain state directly reflects the safety and fatigue life of structural connections. Real-time monitoring of bolt strain is crucial for preventing sudden failures.

[0003] Traditional resistive or semiconductor strain gauges are susceptible to electromagnetic interference, resulting in data distortion under conditions of high voltage and high temperature. While conventional fiber optic grating sensors possess anti-interference characteristics, they lack encapsulation protection specific to the unique environment of bolt inner holes, making them prone to fiber breakage due to vibration or impact, leading to low stress transfer efficiency. Furthermore, existing fiber optic grating sensors often employ external mounting, where the adhesive layer is susceptible to creep under dynamic loads, causing strain transfer lag. Additionally, the curvature of the bolt surface affects the uniformity of fiber optic grating adhesion, resulting in significant measurement errors. Therefore, those skilled in the art provide a fiber optic grating strain sensor for bolts to address the problems mentioned in the background. Utility Model Content

[0004] The purpose of this invention is to provide a fiber optic strain sensor for bolts, thereby solving the problems mentioned in the background art.

[0005] This utility model provides the following technical solution: a fiber optic strain sensor for bolts, comprising a steel pipe for support and protection, wherein a detection component for detecting bolt strain is installed inside the steel pipe, and protective components for protecting the detection component are installed at both ends of the steel pipe.

[0006] As a preferred embodiment of the above technical solution, the detection component includes a fixed bracket and a fiber optic grating body. Two fixed brackets are provided and are symmetrically arranged. The two fixed brackets are fixedly connected to both sides of the inner wall of the steel pipe, and the fiber optic grating body is located at the center inside the steel pipe.

[0007] As a preferred embodiment of the above technical solution, each of the two fixed supports has a fixing port at the end away from the steel pipe, and the two fixing ports are symmetrically arranged. A through hole is provided at the center of the inner wall of each of the two fixing ports. The two ends of the fiber grating body are respectively located inside the two through holes, and the inner sidewalls of the two fixing ports are provided with internal threads.

[0008] As a preferred embodiment of the above technical solution, the protective component includes an encapsulation end cap and a protective end cap. Both the encapsulation end cap and the protective end cap are provided with external threads. The encapsulation end cap is threaded into one of the fixing ports, and the protective end cap is threaded into the other fixing port. The pigtail portion of the fiber optic grating body passes through the protective end cap, and the pigtail portion of the fiber optic grating body is located outside the steel pipe.

[0009] As a preferred embodiment of the above technical solution, the two ends of the fiber optic grating are respectively fixed inside two perforations with special adhesive.

[0010] As a preferred embodiment of the above technical solution, a fixing groove is provided on the side of the protective end cap away from the steel pipe, and the pigtail portion of the fiber optic grating body is fixedly connected to the fixing groove on one side of the protective end cap by special adhesive.

[0011] Compared with the prior art, the beneficial effects of this utility model are:

[0012] A special adhesive is used to fix a steel pipe inside the bolt hole to be tested. The strain of the bolt is directly transmitted to the fiber optic grating through the special adhesive. The strain of the bolt is reflected by measuring the strain of the fiber optic grating. The electromagnetic interference resistance of the fiber optic grating ensures stable monitoring under complex working conditions. The steel pipe structure optimizes stress transmission efficiency and protects the fiber optic grating from mechanical damage. It not only ensures long-term stability under dynamic loads but also adapts to a wide temperature range environment. This embedded design improves the accuracy of bolt health monitoring. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a fiber optic strain sensor for bolts.

[0014] Figure 2 This is a schematic diagram of the detection component structure of a fiber optic strain sensor for bolts;

[0015] Figure 3 This is a schematic diagram of the protective component structure of a fiber optic strain sensor for bolts.

[0016] Figure 4 This is a cross-sectional view of the structure of a bolt-mounted fiber optic strain sensor after installation.

[0017] Legend:

[0018] 1. Steel pipe; 2. Detection component; 201. Fixing bracket; 202. Fiber grating body; 203. Fixing port; 204. Perforation; 3. Protective component; 301. Encapsulation end cap; 302. Protective end cap. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0020] Please see Figures 1-4 As shown, this utility model provides a technical solution: a fiber optic strain sensor for bolts, including a steel pipe 1 for support and protection, a detection component 2 for detecting bolt strain installed inside the steel pipe 1, and protective components 3 for protecting the detection component 2 installed at both ends of the steel pipe 1.

[0021] As one implementation method in this embodiment, please refer to Figure 1 , Figure 2 and Figure 4 As shown, the detection component 2 includes a fixed bracket 201 and a fiber optic grating body 202. There are two fixed brackets 201, and the two fixed brackets 201 are symmetrically arranged. The two fixed brackets 201 are fixedly connected to both sides of the inner wall of the steel pipe 1. The fiber optic grating body 202 is located at the center inside the steel pipe 1.

[0022] Each of the two fixed supports 201 has a fixed opening 203 at the end away from the steel pipe 1, and the two fixed openings 203 are symmetrically arranged. A through hole 204 is opened at the center of the inner wall of each of the two fixed openings 203. The two ends of the fiber optic grating body 202 are respectively set inside the two through holes 204, and the inner sidewalls of the two fixed openings 203 are provided with internal threads.

[0023] Furthermore, a special adhesive is used to fix the steel pipe 1 inside the bolt hole to be tested. The strain of the bolt is directly transmitted to the fiber grating body 202 inside the steel pipe 1 through the special adhesive. The strain of the bolt is reflected by measuring the strain of the fiber grating body 202. The steel pipe 1 encapsulation and special adhesive bonding technology realize precise strain monitoring. The electromagnetic interference resistance of the fiber grating body 202 ensures stable monitoring under complex working conditions. The structure of the steel pipe 1 optimizes stress transmission efficiency and protects the fiber grating body 202 from mechanical damage. The bonding of the special adhesive realizes the tight coupling between the device and the bolt to be tested, which not only ensures long-term stability under dynamic loads, but also adapts to a wide temperature range environment. This embedded design improves the accuracy of bolt health monitoring.

[0024] The fixed bracket 201 not only avoids non-axial strain interference caused by bolt vibration or deformation in the fiber grating body 202, but also concentrates the strain of the inner wall of the bolt to the sensitive area of ​​the fiber grating body 202 through the rigid structure, while providing uniform stress distribution for the special adhesive bonding interface, thereby significantly improving the signal-to-noise ratio and long-term reliability of the monitoring data.

[0025] As one implementation method in this embodiment, please refer to Figures 1-3As shown, the protective component 3 includes an encapsulation end cap 301 and a protective end cap 302. Both the encapsulation end cap 301 and the protective end cap 302 are provided with external threads. The encapsulation end cap 301 is threaded into one of the fixing ports 203, and the protective end cap 302 is threaded into the other fixing port 203. The pigtail portion of the fiber optic grating body 202 passes through the protective end cap 302, and the pigtail portion of the fiber optic grating body 202 is located outside the steel pipe 1.

[0026] Furthermore, the encapsulation end cap 301 and the protective end cap 302 seal the internal cavity of the steel pipe 1 through the sealing and fixing port 203, thereby isolating the external environment from the corrosion of the internal fiber optic grating body 202 and ensuring the stability of strain transmission. The protective end cap 302 achieves non-destructive output of photoelectric signals through the through-type fiber optic grating body 202 pigtail design. Its detachable feature facilitates later maintenance and calibration, ensuring both long-term reliable operation of the device and convenient installation.

[0027] As one implementation method in this embodiment, please refer to Figure 2 As shown, the two ends of the fiber grating body 202 are fixed inside the two perforations 204 respectively by special adhesive.

[0028] Furthermore, by utilizing the high adhesion and stress-matching properties of the special adhesive, rigid coupling between the fiber grating body 202 and the perforation 204 is achieved, ensuring maximum strain transfer efficiency. At the same time, the elastic buffering effect of the adhesive layer absorbs thermal expansion differences and micro-vibration interference.

[0029] As one implementation method in this embodiment, please refer to Figure 3 As shown, a fixing groove is provided on the side of the protective end cap 302 away from the steel pipe 1, and the pigtail of the fiber optic grating body 202 is fixedly connected to the fixing groove on one side of the protective end cap 302 by special adhesive.

[0030] Furthermore, by using the fixing groove structure of the protective end cap 302, the fiber optic grating body 202 pigtail is precisely anchored with special adhesive. On the one hand, this ensures the anti-displacement stability of the fiber optic grating body 202 pigtail under the vibration of the steel pipe 1 or external tension, and avoids the interruption of the signal transmission path due to mechanical disturbance. On the other hand, the adhesive layer buffers stress concentration and extends the fatigue life of the fiber optic grating body 202 pigtail in harsh environments.

[0031] Working principle: A special adhesive is used to fix a steel pipe 1 inside the bolt hole to be tested. The strain of the bolt is directly transmitted to the fiber optic grating body 202 inside the steel pipe 1 through the special adhesive. The strain of the bolt is reflected by measuring the strain of the fiber optic grating body 202. The use of steel pipe 1 encapsulation and special adhesive bonding technology achieves accurate strain monitoring. The anti-electromagnetic interference characteristics of the fiber optic grating body 202 ensure stable monitoring under complex working conditions. The structure of the steel pipe 1 optimizes stress transmission efficiency and protects the fiber optic grating body 202 from mechanical damage. The bonding of the special adhesive achieves tight coupling between the device and the bolt to be tested, which not only ensures long-term stability under dynamic loads but also adapts to a wide temperature range environment. This embedded design improves the accuracy of bolt health monitoring.

[0032] The above embodiments are only used to illustrate the technical solution of this utility model, and are not intended to limit it.

Claims

1. A fiber optic strain sensor for bolts, comprising a steel tube (1) for support and protection, characterized in that: The steel pipe (1) is equipped with a detection component (2) for detecting bolt strain, and protective components (3) for protecting the detection component (2) are installed at both ends of the steel pipe (1).

2. The fiber optic strain sensor for bolts according to claim 1, characterized in that: The detection component (2) includes a fixed bracket (201) and a fiber optic grating body (202). There are two fixed brackets (201), and the two fixed brackets (201) are arranged symmetrically. The two fixed brackets (201) are fixedly connected to both sides of the inner wall of the steel pipe (1). The fiber optic grating body (202) is located at the center inside the steel pipe (1).

3. A fiber optic strain sensor for bolts according to claim 2, characterized in that: Each of the two fixed brackets (201) has a fixed opening (203) at the end away from the steel pipe (1), and the two fixed openings (203) are symmetrically arranged. A through hole (204) is provided at the center of the inner wall of each of the two fixed openings (203). The two ends of the fiber grating body (202) are respectively located inside the two through holes (204). The inner sidewalls of the two fixed openings (203) are provided with internal threads.

4. A fiber optic strain sensor for bolts according to claim 3, characterized in that: The protective component (3) includes an encapsulation end cap (301) and a protective end cap (302). Both the encapsulation end cap (301) and the protective end cap (302) are provided with external threads. The encapsulation end cap (301) is threaded into one of the fixing ports (203), and the protective end cap (302) is threaded into the other fixing port (203). The pigtail portion of the fiber grating body (202) passes through the protective end cap (302), and the pigtail portion of the fiber grating body (202) is located outside the steel pipe (1).

5. A fiber optic strain sensor for bolts according to claim 3, characterized in that: The two ends of the fiber grating body (202) are fixed inside the two perforations (204) by special adhesive.

6. A fiber optic strain sensor for bolts according to claim 4, characterized in that: The protective end cap (302) has a fixing groove on the side away from the steel pipe (1), and the pigtail of the fiber grating body (202) is fixedly connected to the fixing groove on the side of the protective end cap (302) by special adhesive.

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