Fiber Bragg grating sensor capable of measuring both strain and displacement and its assembly and use method
By designing a fiber grating sensor with both strain and displacement measurement functions, the problem that the prior art cannot accurately monitor small strain and large displacement at the same time is solved, and high-precision structural health monitoring is achieved.
Patent Information
- Application Number
- CN202411161708.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-23
- Publication Date
- 2025-04-04
AI Technical Summary
Existing strain gauge and displacement sensors cannot accurately monitor tiny strains and large displacements at the same time, resulting in insufficient application in structural health monitoring.
A fiber grating sensor that can measure both strain and displacement is designed. Through the combination of sensing unit and measuring unit, the measurement unit is conveniently replaced by threaded connections to achieve both strain and displacement. The sensing unit includes a joint, a housing, an optical fiber fixing rod, an optical fiber grating and an elastic mechanism. The optical fiber grating passes through multiple components and is fixed in different positions, and the pretension and release of the optical fiber grating is achieved through the elastic mechanism.
The same sensor is used to measure both strain and displacement, ensuring good accuracy when monitoring small strain and large displacement, improving the accuracy of grating pretension and reducing production difficulty.
Smart Images
Figure CN119756188A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a sensor and an assembly and use method thereof, in particular to a fiber grating sensor capable of measuring strain and displacement and an assembly and use method thereof. Background Art
[0002] As the infrastructure frenzy gradually fades, large-scale buildings and structures gradually enter the heavy maintenance stage. In order to ensure the safety and reliability of the structure and reduce the engineering risks during operation, the importance of structural health monitoring and early warning is becoming increasingly prominent. Strain and displacement are both key parameters that reflect component deformation and structural safety in detection and monitoring work.
[0003] The physical and chemical properties of quartz, the material of the optical fiber itself, are stable. Therefore, fiber grating sensors that use optical fiber for sensing and signal transmission have the advantages of anti-electromagnetic interference, high durability and long-term stability, and are gradually being widely used in structural monitoring.
[0004] However, although strain and displacement are both deformation parameters of the structure, relatively speaking, strain is a small deformation. For example, the maximum deformation measured by a strain gauge with a gauge length of 100mm is usually no more than 0.3mm; while displacement generally refers to a larger deformation, which can generally reach tens or even hundreds of centimeters. Therefore, the existing strain gauges and displacement sensors generally belong to two different sensor types, which have great differences in structure. No fiber Bragg grating sensor has been found that can accurately monitor both small strains and large displacements. Summary of the invention
[0005] The technical problem to be solved by the present invention is to provide a fiber grating sensor that can measure both strain and displacement and its assembly and use method, so as to achieve good accuracy in monitoring both small strains and large displacements, and promote the application of fiber optic sensing technology in structural health monitoring.
[0006] The technical solution to the above technical problem is: a fiber grating sensor capable of measuring both strain and displacement, comprising a sensing unit and a measuring unit, wherein the measuring unit comprises a strain measuring unit or a displacement measuring unit, and the strain measuring unit or the displacement measuring unit is respectively connected to the sensing unit by threads.
[0007] A further technical solution of the present invention is: the sensing unit comprises a joint, a shell I, an optical fiber fixing rod I, an optical fiber Bragg grating, and an elastic mechanism; one end of the shell I is connected to the joint, and the other end is connected to one end of the elastic mechanism; the diameters of the inner hole at both ends of the shell I are different, the inner hole at the large diameter end is clearance-matched with the optical fiber fixing rod I; the inner hole at the small diameter end is clearance-matched with one end of the elastic mechanism, and the inner hole at the small diameter end is smaller than the outer diameter of the optical fiber fixing rod I; the other end of the elastic mechanism is connected to a strain measurement unit or a displacement measurement unit; the optical fiber Bragg grating passes through the joint, the optical fiber fixing rod I, the shell I, the elastic mechanism, the strain measurement unit or the displacement measurement unit in sequence, and the optical fiber Bragg grating is fixed to the optical fiber fixing rod I and the elastic mechanism respectively.
[0008] A further technical solution of the present invention is: the elastic mechanism includes an optical fiber fixing rod II, a stretcher, an extrusion ring, and an outer shell II. The inner hole of the outer shell II has threaded holes at both ends and a light hole in the middle. The threaded holes at both ends of the outer shell II are threadedly connected with the outer shell I and the extrusion ring respectively. The middle light hole of the outer shell II is gap-matched with the middle step of the stretcher. The stretcher is provided with elastic elements on the shoulders between the end faces at both ends of the middle step and the end faces of the outer shell I and the extrusion ring respectively. The optical fiber fixing rod II passes through the inner hole of the small diameter end of the outer shell I, the stretcher, and the extrusion ring in sequence and is threadedly connected with the strain measurement unit or the displacement measurement unit.
[0009] A further technical solution of the present invention is: the elastic element is a spring.
[0010] A further technical solution of the present invention is that the optical fiber fixing rods I and II are respectively provided with through-length optical fiber installation grooves along their axial directions, and the optical fiber gratings buried in the bottom of the optical fiber installation grooves are respectively located at the central axis of the optical fiber fixing rods I and II.
[0011] A further technical solution of the present invention is that the fiber Bragg grating includes a strain grating and a temperature compensation grating connected in series, the strain grating is arranged between the fiber fixing rod I and the fiber fixing rod II, and the temperature compensation grating is arranged in the fiber installation groove of the fiber fixing rod I.
[0012] A further technical solution of the present invention is: the strain measurement unit includes a connector A and a strain measurement joint for leading out the optical fiber, one end of the connector A extends into the housing II and is threadedly connected to the optical fiber fixing rod II, and the other end of the connector is threadedly connected to the strain measurement joint.
[0013] A further technical solution of the present invention is: the displacement measuring unit includes a shell III, a connector B, a tension spring, a stretching rod and a limiter which are sequentially installed axially in the shell III; one end of the connector B is provided with an internal threaded hole, and is threadedly connected to the optical fiber fixing rod II through the internal threaded hole, the other end of the connector B is provided with a tension spring connecting hole, and the outer diameter of the connector B and the inner diameter of the shell III are clearance matched; the stretching rod is a variable diameter round rod with a short large end and a long small end, the large diameter end of the stretching rod is clearance matched with the shell III, and the end face of the large diameter end of the stretching rod and the tension spring connecting hole of the connector B are respectively connected to the two ends of the tension spring, and the small diameter end of the stretching rod is clearance matched with the inner hole of the limiter.
[0014] Another technical solution of the present invention is: a method for assembling a fiber grating sensor capable of measuring both strain and displacement, comprising the following steps: S1. Assemble the fiber anchoring structure: The fiber grating is respectively pasted and fixed in the fiber installation grooves of the fiber fixing rod I and the fiber fixing rod II to form a fiber anchoring structure; S2. Install the optical fiber fixing rod II: Insert the optical fiber fixing rod II into the inner hole of the large diameter end of the housing I; S3. Pre-tensioning the fiber Bragg grating: Install the elastic element and the stretcher on the left side in sequence, tighten the stretcher, stretch the fiber Bragg grating to the wavelength change amount a, and realize the pre-tensioning of the fiber Bragg grating; S4. Expand the fiber Bragg grating: Install the elastic element and housing II on the right side, install the extrusion ring, and tighten the extrusion ring to squeeze the elastic element to achieve the expansion of the fiber Bragg grating. The wavelength change of the expansion is b, b<a. The fiber Bragg grating is still in a stretched state, so that the sensor has basically the same tensile and compressive stiffness; S5. Install the measuring unit: According to the size of the measured strain or displacement, a strain measuring unit or a displacement measuring unit is installed to realize the conversion of strain and displacement measurement.
[0015] Another technical solution of the present invention is: a method for using a fiber grating sensor capable of measuring both strain and displacement. When strain measurement is required, after installing a strain measurement unit, the sensor is strain calibrated to obtain a strain calibration coefficient. When working, the housing I and connector A are fixed to the object to be measured with the designed gauge length. By directly stretching the optical fiber, the wavelength of the grating changes, and then according to the strain calculation formula Calculate strain value ,in: is the fiber Bragg grating central wavelength; is the change in the central wavelength of the fiber Bragg grating; is the elastic-optical coefficient of the fiber Bragg grating; is the optical fiber deformation; is the length of the optical fiber deformation section. When displacement measurement is required, the displacement measurement unit is installed, and after displacement calibration, the strain calibration coefficient is obtained. The sensor housing I and the stretching rod are installed at the two positions where relative displacement needs to be measured. When the two positions are relatively displaced, the force is transmitted to the fiber Bragg grating through the stretching rod, tension spring, connector B and optical fiber fixing rod II, causing the wavelength to change. Then, according to the displacement calculation formula Calculate displacement value ,in: is the fiber Bragg grating central wavelength; is the change in the central wavelength of the fiber Bragg grating; is the elastic-optical coefficient of the fiber Bragg grating; is the optical fiber deformation; is the length of the optical fiber deformation section.
[0016] Due to the above structure, the fiber grating sensor capable of measuring strain and displacement and its assembly and use method of the present invention have the following beneficial effects compared with the prior art: 1. The same sensor can measure both strain and displacement The sensor provided by the present invention comprises a sensing unit and a measuring unit, wherein the measuring unit comprises a strain measuring unit or a displacement measuring unit, and the strain measuring unit or the displacement measuring unit is respectively connected to the sensing unit by threads. The sensor of the present invention has a conveniently detachable measuring unit, and the same sensor can measure strain and displacement by only replacing the measuring unit.
[0017] 2. Good accuracy in monitoring both small strains and large displacements Since the conventional strain measurement range is ±1500με, the corresponding deformation under 100mm gauge length is ±0.15mm, and the conventional displacement measurement range is 10mm, 20mm, 30mm, 50mm and 100mm or even larger, the measurement range is increased by a hundred times, and conventional strain gauges cannot perform measurements. However, the present invention can adapt a suitable measurement unit (so that the measured deformation is within 20% to 80% of the sensor range) according to the deformation range to be measured, thereby ensuring the accuracy of different measurement ranges, that is, it has good accuracy when monitoring both small strains and large displacements.
[0018] 3. It can improve the accuracy of grating pre-tensioning and reduce the difficulty of production The elastic mechanism design of the sensing unit in the present invention allows the grating to be pre-tensioned during the sensor assembly process without the need to tension the optical fiber when it is pasted, thereby improving the accuracy of the grating pre-tensioning and avoiding the overlap of the grating tensioning and pasting processes, reducing the difficulty of production, and ensuring that the tension and compression strokes of the sensing unit of the sensor have basically the same stiffness.
[0019] 4. Reasonable structure Since the optical fiber fixing rod I of the present invention is installed in the inner hole of the large diameter end of the housing I, and is not fixedly connected to the joint and the housing I, the optical fiber fixing rod I is an independent structure. The present invention sets the temperature compensation grating in the optical fiber installation groove of the optical fiber fixing rod I, which greatly avoids the erroneous compensation caused by the change of temperature grating data due to external force, and its structure is relatively reasonable.
[0020] The technical features of the fiber grating sensor capable of measuring both strain and displacement and its assembly and use methods of the present invention are further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 : In the first embodiment, the structural diagram of the sensing unit of the present invention when connected to the strain measuring unit, Figure 2 : In the first embodiment, the structural diagram of the sensing unit of the present invention when connected with the displacement measuring unit, Figure 3 : In the first embodiment, the structural diagram of the sensor unit is as follows: Figure 4 : In the first embodiment, the structural diagram of the stretcher is as follows: Figure 5 : In the first embodiment, the structural diagram of the strain measurement unit is as follows: Figure 6 : In the first embodiment, the structural diagram of the displacement measurement unit is as follows: Figure 7 : In embodiment 1, a schematic diagram of the structure of the stretching rod; In the above drawings, the descriptions of the reference numerals are as follows: 1- Sensing unit, 11-connector, 12-housing Ⅰ, 13-optical fiber fixing rod Ⅰ, 14-optical fiber grating, 15-elastic mechanism, 151-optical fiber fixing rod II, 152-elastic element, 153-tensioner, 1531-middle step, 1532-shaft shoulder, 154-extrusion ring, 155-housing II, 2- Strain measurement unit, 21-Connector A, 22-Strain gauge connector, 3- Displacement measurement unit, 31-connector B, 32-housing III, 33-tension spring, 34-stretching rod, 341-large diameter end, 342-small diameter end, 35-limiter. DETAILED DESCRIPTION Embodiment 1
[0022] A fiber grating sensor capable of measuring both strain and displacement comprises a sensing unit 1 and a measuring unit, wherein the measuring unit comprises a strain measuring unit 2 or a displacement measuring unit 3, wherein the strain measuring unit 2 or the displacement measuring unit 3 is respectively connected to the sensing unit 1 by threads, thereby realizing convenient connection and disassembly between the measuring unit and the sensing unit.
[0023] The sensing unit 1 comprises a connector 11, a housing Ⅰ12, an optical fiber fixing rod Ⅰ13, an optical fiber Bragg grating 14, and an elastic mechanism 15; the connector 11 is used to lead out the optical fiber, one end of the housing Ⅰ12 is provided with an external thread and connected to the connector 11 through the external thread, and the other end of the housing Ⅰ12 is also provided with an external thread and connected to one end of the elastic mechanism 15 through the external thread; the diameters of the inner hole of the housing Ⅰ12 at both ends are different, the inner hole at the large diameter end is clearance-matched with the optical fiber fixing rod Ⅰ13, so that the optical fiber fixing rod Ⅰ13 is independently located in the inner hole at the large diameter end; the inner hole at the small diameter end is clearance-matched with one end of the elastic mechanism 15, and the inner hole at the small diameter end is smaller than the outer diameter of the optical fiber fixing rod Ⅰ13; the optical fiber Bragg grating 14 passes through the connector 11, the optical fiber fixing rod Ⅰ13, the housing Ⅰ12, the elastic mechanism 15, the strain measurement unit 2 or the displacement measurement unit 3 in sequence, and the optical fiber Bragg grating 14 is fixed on the optical fiber fixing rod Ⅰ13 and the elastic mechanism 15 respectively.
[0024] The elastic mechanism 15 includes an optical fiber fixing rod II 151, a tensioner 153, an extrusion ring 154, and a shell II 155. The inner hole of the shell II 155 has threaded holes at both ends and a light hole in the middle. The threaded holes at both ends of the shell II 155 are threadedly connected to the shell I 12 and the extrusion ring 154 respectively. The middle light hole of the shell II 155 is clearance-matched with the middle step 1531 of the tensioner 153. The tensioner 153 has elastic elements 152, i.e., springs, installed on the shoulders 1532 at the left and right ends of the tensioner 153. One end of the spring abuts against the end face of the middle step 1531, and the other end abuts against the end face of the shell I 12 or the end face of the extrusion ring 154. The optical fiber fixing rod II 151 passes through the inner hole of the small diameter end of the outer shell I 12, the stretcher 153, and the extrusion ring 154 in sequence and is connected to the strain measurement unit 2 or the displacement measurement unit 3 by means of threads. The optical fiber fixing rod II 151 is provided with a full-length optical fiber installation groove along the axial direction, and the optical fiber Bragg grating 14 buried in the bottom of the optical fiber installation groove is located at the central axis of the optical fiber fixing rod II 151.
[0025] The optical fiber fixing rod I13 and the optical fiber fixing rod II151 are respectively provided with a full-length optical fiber installation groove along their axial direction, and the optical fiber grating 14 buried in the bottom of the optical fiber installation groove is respectively located at the central axis of the optical fiber fixing rod I13 and the optical fiber fixing rod II151.
[0026] The fiber grating 14 comprises a strain grating and a temperature compensation grating connected in series. The strain grating is arranged between the fiber fixing rod Ⅰ13 and the fiber fixing rod Ⅱ151, and the temperature compensation grating is arranged in the fiber installation groove of the fiber fixing rod Ⅰ13.
[0027] The strain measurement unit 2 includes a connector A21 and a strain measurement connector 22 for leading out the optical fiber. The connector A21 is provided with a through hole for passing the optical fiber grating 14, and one end of the through hole is also provided with an internal thread matching the external thread of the optical fiber fixing rod II151; one end of the connector A21 extends into the housing II155 and is threadedly connected to the optical fiber fixing rod II151, and the other end of the connector 21 is threadedly connected to the strain measurement connector 22, and the strain measurement connector 22 is used to lead out the optical fiber.
[0028] The displacement measuring unit 3 includes a shell III32, a connector B31, a tension spring 33, a stretching rod 34 and a limiter 35 which are sequentially installed axially in the shell III32; one end of the connector B31 is provided with an internal threaded hole, and is threadedly connected to the optical fiber fixing rod II151 through the internal threaded hole, and the other end of the connector B31 is provided with a tension spring connecting hole, and the outer diameter of the connector B31 and the inner diameter of the shell III32 are clearance matched; the stretching rod 34 is a variable diameter round rod with a short large end and a long small end, the large diameter end 341 of the stretching rod 34 is clearance matched with the shell III32, and the end face of the large diameter end of the stretching rod 34 and the tension spring connecting hole of the connector B31 are respectively connected to the two ends of the tension spring 33, and the small diameter end 342 of the stretching rod 34 is clearance matched with the inner hole 35 of the limiter.
[0029] As a variation of the first embodiment, the elastic element 152 may also be another element made of a material that can undergo elastic deformation. Embodiment 2
[0030] A method for assembling a fiber grating sensor capable of measuring both strain and displacement comprises the following steps: S1. Assembling the optical fiber anchoring structure: The optical fiber Bragg grating 14 is respectively pasted and fixed in the optical fiber mounting groove of the optical fiber fixing rod Ⅰ13 and the optical fiber fixing rod Ⅱ151 to form an optical fiber anchoring structure; S2. Install the optical fiber fixing rod Ⅱ: Insert the optical fiber fixing rod Ⅱ151 from the inner hole of the large diameter end of the housing Ⅰ12; S3 pre-tensioning the fiber Bragg grating: sequentially install the elastic element 152 and the tensioner 153 on the left, tighten the tensioner 153, stretch the fiber Bragg grating 14 to the wavelength change a, and pre-tension the fiber Bragg grating 14; S4. Release the fiber Bragg grating: install the elastic element 152 and the housing II 155 on the right side, install the extrusion ring 154, and squeeze the elastic element 152 by tightening the extrusion ring 154 to achieve the release of the fiber Bragg grating 14. The wavelength change of the release is b, b < a, and the fiber Bragg grating 14 is still in a stretched state, so that the entire sensing unit of the sensor has substantially the same tensile and compressive stiffness; S5. Install the measuring unit: Install the strain measuring unit 2 or the displacement measuring unit 3 according to the magnitude of the strain or displacement to be measured, so as to realize the transformation between the strain and displacement measurement. Embodiment 3
[0031] A method for using a fiber grating sensor capable of measuring both strain and displacement. When strain measurement is required, after installing a strain measurement unit 2, the sensor is strain calibrated to obtain a strain calibration coefficient. When working, the housing Ⅰ12 and the connector A21 are fixed to the object to be measured with the designed gauge length. By directly stretching the optical fiber, the wavelength of the grating is changed, and then the strain calculation formula is used. Calculate strain value ,in: is the fiber Bragg grating central wavelength; is the change in the central wavelength of the fiber Bragg grating; is the elastic-optical coefficient of the fiber Bragg grating; is the optical fiber deformation; is the length of the optical fiber deformation section. When displacement measurement is required, the displacement measurement unit 3 is installed, and after displacement calibration, the strain calibration coefficient is obtained. The housing Ⅰ12 and the stretching rod 34 of the sensor are respectively installed at the two positions where relative displacement needs to be measured. When the two positions are relatively displaced, the force is transmitted to the fiber Bragg grating 14 through the stretching rod 34, the tension spring 33, the connector B31 and the optical fiber fixing rod Ⅱ151, causing the wavelength to change. Then, according to the displacement calculation formula Calculate displacement value ,in: is the fiber Bragg grating central wavelength; is the change in the central wavelength of the fiber Bragg grating; is the elastic-optical coefficient of the fiber Bragg grating; is the optical fiber deformation; is the length of the optical fiber deformation section.
Claims
1. A fiber Bragg grating sensor capable of measuring both strain and displacement, comprising a sensing unit (1) and a measuring unit, characterized in that: The measuring unit comprises a strain measuring unit (2) or a displacement measuring unit (3), and the strain measuring unit (2) or the displacement measuring unit (3) is respectively connected to the sensing unit (1) via threads.
2. The fiber Bragg grating sensor capable of measuring both strain and displacement according to claim 1, characterized in that: The sensing unit (1) comprises a joint (11), a housing I (12), an optical fiber fixing rod I (13), an optical fiber Bragg grating (14), and an elastic mechanism (15); one end of the housing I (12) is connected to the joint (11), and the other end is connected to one end of the elastic mechanism (15); the diameters of the inner hole at the two ends of the housing I (12) are different, the inner hole at the large diameter end is clearance-matched with the optical fiber fixing rod I (13); the inner hole at the small diameter end is clearance-matched with one end of the elastic mechanism (15), and the inner hole at the small diameter end is smaller than the outer diameter of the optical fiber fixing rod I (13); the other end of the elastic mechanism (15) is connected to the strain measurement unit (2) or the displacement measurement unit (3); the optical fiber Bragg grating (14) passes through the joint (11), the optical fiber fixing rod I (13), the housing I (12), the elastic mechanism (15), the strain measurement unit (2) or the displacement measurement unit (3) in sequence, and the optical fiber Bragg grating (14) is respectively fixed to the optical fiber fixing rod I (13) and the elastic mechanism (15).
3. The fiber Bragg grating sensor capable of measuring both strain and displacement according to claim 2, characterized in that: The elastic mechanism (15) comprises an optical fiber fixing rod II (151), a tensioner (153), an extrusion ring (154), and a shell II (155). The inner hole of the shell II (155) has threaded holes at both ends and a light hole in the middle. The threaded holes at both ends of the shell II (155) are respectively threadedly connected to the shell I (12) and the extrusion ring (154). The middle light hole of the shell II (155) is clearance-matched with the middle step (1531) of the tensioner (153). The tensioner (153) has elastic elements (152) installed on the shaft shoulders (1532) between the end faces at both ends of the middle step (1531) and the end faces of the shell I (12) and the extrusion ring (154). The optical fiber fixing rod II (151) passes through the inner hole of the small diameter end of the shell I (12), the tensioner (153), and the extrusion ring (154) in sequence, and is then threadedly connected to the strain measurement unit (2) or the displacement measurement unit (3).
4. The fiber Bragg grating sensor capable of measuring both strain and displacement according to claim 3, characterized in that: The elastic element (152) is a spring.
5. The fiber Bragg grating sensor capable of measuring both strain and displacement according to claim 3, characterized in that: The optical fiber fixing rod I (13) and the optical fiber fixing rod II (151) are respectively provided with a full-length optical fiber installation groove along their axial direction, and the optical fiber grating (14) buried in the bottom of the optical fiber installation groove is respectively located at the central axis of the optical fiber fixing rod I (13) and the optical fiber fixing rod II (151).
6. The fiber Bragg grating sensor capable of measuring both strain and displacement according to claim 5, characterized in that: The fiber grating (14) comprises a strain grating and a temperature compensation grating connected in series, the strain grating is arranged between the fiber fixing rod I (13) and the fiber fixing rod II (151), and the temperature compensation grating is arranged in the fiber installation groove of the fiber fixing rod I (13).
7. The fiber Bragg grating sensor capable of measuring both strain and displacement according to claim 3, characterized in that: The strain measurement unit (2) comprises a connector A (21) and a strain measurement connector (22) for leading out an optical fiber, one end of the connector A (21) extends into the housing II (155) and is threadedly connected to the optical fiber fixing rod II (151), and the other end of the connector (21) is threadedly connected to the strain measurement connector (22).
8. The fiber Bragg grating sensor capable of measuring both strain and displacement according to claim 3, characterized in that: The displacement measuring unit (3) comprises a housing III (32), a connector B (31) axially mounted in the housing III (32), a tension spring (33), a stretching rod (34) and a stopper (35); one end of the connector B (31) is provided with an internal threaded hole and is threadedly connected to the optical fiber fixing rod II (151) through the internal threaded hole; the other end of the connector B (31) is provided with a tension spring connection hole, and the outer diameter of the connector B (31) and the inner diameter of the housing III (32) are clearance matched; the stretching rod (34) is a variable diameter round rod with a short large end and a long small end; the large diameter end (341) of the stretching rod (34) is clearance matched with the housing III (32), and the end surface of the large diameter end of the stretching rod (34) and the tension spring connection hole of the connector B (31) are respectively connected to the two ends of the tension spring (33), and the small diameter end (342) of the stretching rod (34) is clearance matched with the inner hole (35) of the stopper.
9. A method for assembling a fiber grating sensor capable of measuring both strain and displacement, characterized in that: The steps include: S1. Assemble the fiber anchoring structure: The optical fiber grating (14) is respectively adhered and fixed in the optical fiber installation grooves of the optical fiber fixing rod I (13) and the optical fiber fixing rod II (151) to form an optical fiber anchoring structure; S2. Install the optical fiber fixing rod II: Insert the optical fiber fixing rod II (151) through the inner hole of the large diameter end of the housing I (12); S3. Pre-tensioning the fiber Bragg grating: The elastic element (152) and the stretcher (153) on the left are sequentially installed, and the stretcher (153) is tightened to stretch the optical fiber Bragg grating (14) to a wavelength change amount a, thereby achieving pre-tensioning of the optical fiber Bragg grating (14); S4. Expand the fiber Bragg grating: Install the elastic element (152) and the housing II (155) on the right side, install the extrusion ring (154), and tighten the extrusion ring (154) to squeeze the elastic element (152) to achieve the expansion of the fiber Bragg grating (14). The wavelength change of the expansion is b, b<a. The fiber Bragg grating (14) is still in a stretched state, so that the sensor has basically the same tensile and compressive stiffness; S5. Install the measuring unit: According to the magnitude of the strain or displacement to be measured, a strain measuring unit (2) or a displacement measuring unit (3) is installed to achieve the conversion between strain and displacement measurement.
10. A method for using a fiber grating sensor capable of measuring both strain and displacement, characterized in that: When strain measurement is required, after installing the strain measurement unit (2), the sensor is strain calibrated to obtain the strain calibration coefficient. When working, the housing I (12) and the connector A (21) are fixed to the object to be measured with the designed gauge length, and the wavelength of the grating is changed by directly stretching the optical fiber. Then, according to the strain calculation formula Calculate strain value ,in: is the fiber Bragg grating central wavelength; is the change in the central wavelength of the fiber Bragg grating; is the elastic-optical coefficient of the fiber Bragg grating; is the optical fiber deformation; is the length of the optical fiber deformation section. When displacement measurement is required, the displacement measurement unit (3) is installed, and after displacement calibration, the strain calibration coefficient is obtained. The housing I (12) and the stretching rod (34) of the sensor are respectively installed at two positions where relative displacement needs to be measured. When the two positions are relatively displaced, the force is transmitted to the fiber Bragg grating (14) through the stretching rod (34), the tension spring (33), the connector B (31) and the optical fiber fixing rod II (151), causing the wavelength to change. Then, according to the displacement calculation formula Calculate displacement value ,in: is the fiber Bragg grating central wavelength; is the change in the central wavelength of the fiber Bragg grating; is the elastic-optical coefficient of the fiber Bragg grating; is the optical fiber deformation; is the length of the optical fiber deformation section.