High-precision fiber grating bolt stress sensor

Abstract

The utility model discloses a high-precision fiber bragg grating bolt stress sensor which comprises a bolt. A temperature compensation terminal mounting hole, an adjusting terminal mounting hole and a wire pressing terminal mounting hole are sequentially formed in the part, close to a bolt head, of the bolt from inside to outside, a temperature compensation terminal is mounted in the temperature compensation terminal mounting hole, an adjusting terminal is fixedly connected in the adjusting terminal mounting hole through an adjusting nut, and the wire pressing terminal mounting hole is used for mounting a wire pressing terminal; an outer sheath is sleeved outside the wire pressing terminal, a strain grating is fixed between the temperature compensation terminal and the adjusting terminal, and a temperature compensation grating is pasted on the temperature compensation terminal. The device is simple in overall structure, rapid to install, high in testing precision, suitable for different bolts and capable of reflecting external tested stress changes through compression and stretching of the high-strength strain grating, and temperature compensation is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of fiber Bragg grating sensors, and particularly relates to a high-precision fiber Bragg grating bolt stress sensor. Background Art

[0002] Since the advent of fiber Bragg gratings, they have been widely used in the field of fiber optic sensing. Due to the advantages of fiber Bragg grating sensors such as anti-electromagnetic interference, anti-corrosion, electrical insulation, high sensitivity, low cost, and good compatibility with ordinary optical fibers, they have attracted more and more attention. Since the resonant wavelength of the fiber Bragg grating is sensitive to changes in stress, strain, and temperature, it is mainly used for the measurement of temperature, stress, and strain.

[0003] Bolts are usually used to connect and fasten two or more components, with high reliability and removability, and are widely used in fields such as large machinery and civil engineering. However, since these structures usually work in heavy-load environments, under long-term heavy-load environments, due to the influence of factors such as vibration, shock, and alternating loads, bolt connections often exhibit phenomena such as sliding, loosening, and even separation. In addition, the influence of temperature will also cause creep and non-uniform deformation of the structure. These influences will reduce the reliability and stability of the structure and pose safety hazards. Therefore, the monitoring of bolt stress is of great significance to the safety and reliability of bolt connection facilities.

[0004] Fiber Bragg gratings have the advantages of small size, explosion-proof, electrical insulation, anti-electromagnetic interference, high precision, high reliability, and good environmental adaptability, and are suitable for use in complex working condition environments. The Chinese patent "A Fiber Bragg Grating Bolt Stress Sensor with a Pre-Tensioning Device" with the patent number CN 105403337B opens a through hole in the center of the bolt, causing great damage to the bolt and reducing the strength of the bolt. The Chinese patent "A Fiber Sensor for Composite Sensing of Bolt Preload and Temperature with a Cavity" with the patent number CN 117629291A opens holes on the side and fixes the optical fiber by flowing glue into the hole. The glue is directly exposed outside and is easily affected by external pressure. The pressure is transmitted to the optical fiber through the glue, affecting the wavelength of the optical fiber and thus affecting the test results; the diameter of the cavity described therein is relatively large, reaching half of the bolt, which will cause damage to the bolt and reduce the bolt strength. At the same time, the inside of the cavity is large while the hole leading to the outside is very small, making actual processing difficult and increasing costs.

[0005] In summary, the existing threaded connection stress measurement devices cause relatively large damage to the bolt structure, reducing the bolt strength. At the same time, the accuracy of the existing threaded connection stress measurement devices is relatively low and cannot meet the high-precision requirements. Therefore, it is particularly important to develop a bolt stress sensor with high precision and less damage to the bolt structure. Summary of the Utility Model

[0006] To solve the above technical problems, the purpose of the present utility model is to provide a high-precision fiber Bragg grating bolt stress sensor, which causes less damage to the bolt structure and has a higher measurement accuracy.

[0007] To achieve the above technical purpose and reach the above technical effect, the present utility model is realized through the following technical solutions:

[0008] A high-precision fiber Bragg grating bolt stress sensor includes a bolt; a part of the bolt near the bolt head is successively provided with a temperature compensation terminal installation hole, an adjustment terminal installation hole, and a wire pressing terminal installation hole from inside to outside. A temperature compensation terminal is installed in the temperature compensation terminal installation hole, an adjustment terminal is fixedly connected in the adjustment terminal installation hole through an adjustment nut, and the wire pressing terminal installation hole is used for installing a wire pressing terminal; an outer sheath is sleeved outside the wire pressing terminal, a strain grating is fixed between the temperature compensation terminal and the adjustment terminal, and a temperature compensation grating is pasted on the temperature compensation terminal.

[0009] Further, an external lead is fixed on the wire pressing terminal.

[0010] Further, the temperature compensation terminal includes a temperature compensation grating pasting part, a fixed thread part, and a small-diameter thread part arranged in sequence. The temperature compensation terminal is installed in the temperature compensation terminal installation hole through its fixed thread part. The center of the temperature compensation terminal has a strain grating fixing hole. One end of the strain grating is fixed on the adjustment terminal, and the other end is pasted and fixed in the strain grating fixing hole. The temperature compensation grating pasting part has a temperature compensation grating pasting surface, and the temperature compensation grating is pasted on the temperature compensation grating pasting surface.

[0011] Further, the rotation of the adjustment nut can pre-tension the strain grating.

[0012] Further, the strain grating is a high-strength femtosecond grating.

[0013] Further, the temperature compensation grating and the strain grating are two grating regions on the same optical fiber.

[0014] Further, a fixing groove is provided on the adjustment terminal, and one end of the strain grating is fixed in the fixing groove.

[0015] Further, the external lead is an armored optical cable.

[0016] Further, the outer sheath adopts a PVC rubber sleeve.

[0017] Further, both the temperature compensation terminal and the adjustment terminal are 316L stainless steel terminals, and the wire pressing terminal is a 304 stainless steel terminal.

[0018] The beneficial effects of the present utility model are:

[0019] When the present utility model is in use, the fiber Bragg grating bolt stress sensor is installed into the corresponding threaded hole. When there is a stress change in the external environment, the external stress will act on the bolt, thereby compressing / stretching the bolt, driving the fiber Bragg grating installed inside it to deform, thus compressing / stretching the strain grating, affecting the wavelength change of the internal light, and finally reflecting the external stress change. The wavelength change of the strain grating has a linear relationship with the external stress change amount, providing a large amount of high-precision data for subsequent bolt stress monitoring; while the temperature compensation grating can perform temperature compensation on the strain grating to eliminate the influence of temperature on stress monitoring. The strain grating in the present utility model adopts a high-strength femtosecond grating, with a wavelength change of more than 30 nm and a resolution accuracy of up to 0.3%. 00 。

[0020] The present utility model opens an installation hole at a position of the bolt close to the bolt head, with less damage to the bolt structure.

[0021] The strain grating in the present utility model is fixed at a fixed point through a temperature compensation terminal and an adjustment terminal, and the temperature compensation grating is fixed through the temperature compensation terminal. The fixing method will not affect the fiber wavelength, thus ensuring the accuracy of the test results;

[0022] The adjustment terminal in the present utility model is fixed through an adjustment nut, so that the strain grating can be pre-tensioned by rotating the adjustment nut, and the pre-tensioned wavelength is more than 10 nm.

[0023] The overall structure of the present utility model is simple, convenient for transportation, quick to install, with self-temperature compensation, high test accuracy, applicable to different bolts, and can reflect the change of the external measured stress through the compression and stretching of the high-strength strain grating; the high-strength strain grating in the present utility model adopts a high-strength femtosecond written grating, which is sensitive and has high precision, solving the problems of low precision and inaccurate measurement of existing sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the overall structure of the high-precision optical grating bolt stress sensor of the present utility model;

[0025] Figure 2 is a cross-sectional view of the high-precision optical grating bolt stress sensor of the present utility model;

[0026] Figure 3 is a schematic diagram of the exploded structure of the high-precision optical grating bolt stress sensor of the present utility model;

[0027] Figure 4 is a schematic diagram of the structure of the temperature compensation terminal in the high-precision optical grating bolt stress sensor of the present utility model;

[0028] Figure 5 is a schematic diagram of the structure of the adjustment terminal in the high-precision optical grating bolt stress sensor of the present utility model;

[0029] In the figure, 1: bolt, 11: installation hole for temperature compensation terminal, 12: installation hole for adjustment terminal, 13: installation hole for wire pressing terminal; 2: temperature compensation terminal, 21: temperature compensation grating pasting part, 22: fixing thread part, 23: small diameter thread part, 24: strain grating fixing hole; 3: adjustment terminal, 31: fixing groove; 4: wire pressing terminal; 5: adjusting nut; 6: outer sheath; 7: strain grating; 8: temperature compensation grating; 9: external lead. Specific embodiments

[0030] The following describes in detail the preferred embodiments of the present invention with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0031] As Figures 1 to 5 shown in the preferred embodiment of a high-precision fiber grating bolt stress sensor, which includes a bolt 1; the part of the bolt 1 close to the bolt head is successively provided with an installation hole 11 for temperature compensation terminal, an installation hole 12 for adjustment terminal and an installation hole 13 for wire pressing terminal from inside to outside. A temperature compensation terminal 2 is installed in the installation hole 11 for temperature compensation terminal. An adjustment terminal 3 is fixedly connected in the installation hole 12 for adjustment terminal through an adjusting nut 5. A wire pressing terminal 4 is installed in the installation hole 13 for wire pressing terminal; an outer sheath 6 is sleeved outside the wire pressing terminal 4. A strain grating 7 is fixed between the temperature compensation terminal 2 and the adjustment terminal 3, and a temperature compensation grating 8 is pasted on the temperature compensation terminal 2.

[0032] An external lead 9 is fixed on the wire pressing terminal 4, and the external lead 9 is an armored optical cable; the external lead 9 passes through the outer sheath 6 to protect the internal optical fiber.

[0033] The temperature compensation terminal 2 includes a temperature compensation grating pasting part 21, a fixing thread part 22 and a small diameter thread part 23 arranged in sequence; the temperature compensation terminal 2 is installed in the installation hole 11 for temperature compensation terminal through its fixing thread part 22; when installing the temperature compensation terminal 2, the small diameter thread part can be used as an operation end to install the temperature compensation terminal in the installation hole for temperature compensation terminal of the bolt; the temperature compensation grating pasting part 21 is a semi-cylindrical structure with a plane, and the plane of the temperature compensation grating pasting part 21 is used as the temperature compensation grating pasting surface, and the temperature compensation grating 8 is pasted on the temperature compensation grating pasting surface; a strain grating fixing hole 24 is provided at the centers of the fixing thread part 22 and the small diameter thread part 23 of the temperature compensation terminal 2. One end of the strain grating 7 is fixed on the adjustment terminal 3, and the other end is fixedly pasted in the strain grating fixing hole 24.

[0034] The diameter of the wire-pressing terminal mounting hole 13 is larger than that of the adjusting terminal mounting hole 12. The wire-pressing terminal mounting hole 13 penetrates through the bolt head of the bolt 1. The end of the wire-pressing terminal 4 is mounted in the wire-pressing terminal mounting hole 13.

[0035] The adjusting terminal 3 is a cylindrical terminal. The adjusting nut 5 is sleeved on the adjusting terminal 3, and the adjusting nut 5 is located in the wire-pressing terminal mounting hole 13. A fixing groove 31 is provided on the adjusting terminal 3, and the strain grating 7 is fixed in the fixing groove 31.

[0036] The adjusting nut 5 cooperates with the adjusting terminal 3. The wavelength of the strain grating 7 can be adjusted by rotating the adjusting nut 5, so as to pre-tension the strain grating 7, and the pre-tension wavelength is above 10 nm.

[0037] The temperature compensation grating 8 and the strain grating 7 are two grating regions on the same optical fiber.

[0038] The strain grating 7 is a high-strength femtosecond grating, and its wavelength change can reach 30 nm, which can ensure that the resolution accuracy of the sensor reaches 0.3% 00 (three ten-thousandths).

[0039] The temperature compensation grating 8 is used to compensate for the deviation caused by the influence of temperature on the strain grating 7, so as to ensure the accuracy of the sensor measurement.

[0040] The outer sheath 6 adopts a PVC rubber sleeve; the temperature compensation terminal 2, the adjusting terminal 3 and the adjusting nut 5 are made of 316L stainless steel, and the wire-pressing terminal 4 is made of 304 stainless steel. The structural parts in the present utility model can prevent rust and water, can overcome the problems of condensation inside the sensor and electromagnetic interference in humid air, greatly prolong the service life of the sensor, and improve the reliability of the sensor.

[0041] During use, the bolt 1 is installed on the stress-bearing device. When there is a stress change in the outside world, the external stress will directly act on the bolt 1, squeezing / stretching the bolt, so that the bolt is compressed / stretched, and then driving the strain grating 7 inside the bolt to be compressed / stretched, thereby affecting the wavelength change of the internal light, and finally reflecting the external stress change, while the temperature compensation grating 8 can perform temperature compensation on the strain grating to eliminate the influence of temperature on stress monitoring.

[0042] For those skilled in the art, it is obvious that the present utility model is not limited to the details of the above-mentioned exemplary embodiments, and the present utility model can be implemented in other specific forms without departing from the spirit or basic characteristics of the present utility model. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present utility model.

[0043] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-precision fiber Bragg grating bolt stress sensor, characterized in that, It includes a bolt; a portion of the bolt near the bolt head is successively provided with a temperature compensation terminal mounting hole, an adjustment terminal mounting hole, and a wire pressing terminal mounting hole from inside to outside. A temperature compensation terminal is installed in the temperature compensation terminal mounting hole, an adjustment terminal is fixedly connected in the adjustment terminal mounting hole through an adjustment nut, and the wire pressing terminal mounting hole is used for installing a wire pressing terminal; an outer sheath is sleeved outside the wire pressing terminal, a strain grating is fixed between the temperature compensation terminal and the adjustment terminal, and a temperature compensation grating is pasted on the temperature compensation terminal.

2. The high-precision fiber Bragg grating bolt stress sensor according to claim 1, wherein An external lead is fixed on the wire pressing terminal.

3. The high-precision fiber Bragg grating bolt stress sensor according to claim 1, characterized in that, The temperature compensation terminal includes a temperature compensation grating pasting portion, a fixed thread portion, and a small diameter thread portion which are successively arranged. The temperature compensation terminal is installed in the temperature compensation terminal mounting hole through its fixed thread portion. The center of the temperature compensation terminal has a strain grating fixing hole. One end of the strain grating is fixed on the adjustment terminal, and the other end is pasted and fixed in the strain grating fixing hole. The temperature compensation grating pasting portion has a temperature compensation grating pasting surface, and the temperature compensation grating is pasted on the temperature compensation grating pasting surface.

4. The high-precision fiber Bragg grating bolt stress sensor according to claim 1, characterized in that, The rotation of the adjustment nut can pre-tension the strain grating.

5. The high-precision fiber Bragg grating bolt stress sensor according to claim 1, characterized in that, The strain grating is a high-strength femtosecond grating.

6. The high-precision fiber Bragg grating bolt stress sensor according to claim 1, wherein The temperature compensation grating and the strain grating are two grating regions on the same optical fiber.

7. The high-precision fiber Bragg grating bolt stress sensor according to claim 1, wherein, A fixed groove is provided on the adjustment terminal, and one end of the strain grating is fixed in the fixed groove.

8. The high-precision fiber Bragg grating bolt stress sensor according to claim 2, wherein, The external lead is an armored optical cable.

9. The high-precision fiber grating bolt stress sensor according to claim 1, characterized in that, The outer sheath is made of a PVC rubber sleeve.

10. The high-precision fiber Bragg grating bolt stress sensor according to claim 1, characterized in that, Both the temperature compensation terminal and the adjustment terminal are 316L stainless steel terminals, and the wire pressing terminal is a 304 stainless steel terminal.

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