Non-type sensitized fiber grating strain sensor

Abstract

The application provides a non-type sensitized fiber grating strain sensor, which comprises an elastic substrate, a hairpin, connecting arms, a left end plate, a right end plate and fiber grating sticking arms, the connecting arms are arranged on both sides of the hairpin and connected to the left end plate and the right end plate; the fiber grating sticking arms are arranged on both sides of the hairpin and fixed with the hairpin, the left end plate, the right end plate and the fiber grating sticking arms form fixing surfaces for fixing the fiber grating, the left end plate and the right end plate are provided with mounting surfaces for fixing a measured substrate; and a fiber grating is fixed on the elastic substrate along the axis of the length direction of the elastic substrate. The application has obvious sensitization effect, so that the fiber grating strain sensor can improve the sensitivity and the measurement accuracy under the condition that the installation space is limited.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber sensing technology, and particularly relates to a non-type sensitized fiber grating strain sensor. BACKGROUND

[0002] In the field of civil engineering, aerospace, petrochemical industry, shipbuilding industry and other structural health monitoring, strain is one of the important physical parameters. Through real-time monitoring of strain, real-time conditions such as equipment, mechanical structure, track operation state can be known in time to prevent safety accidents.

[0003] Optical fiber grating sensing technology is widely used in the health monitoring of various structures due to its electrical insulation, anti-electromagnetic interference, corrosion resistance, strong stability, small size and light weight. According to the strain sensing principle of optical fiber grating, the strain measurement sensitivity of bare optical fiber grating is 1.2 pm / με, but it cannot meet the requirements of monitoring sensitivity and stability in actual application.

[0004] In the health monitoring of large structures, the deformation of the structure is small, the strain generated is small, and the installation space of the strain sensor is limited, so the sensitization effect cannot be improved by changing the fixed distance of the strain sensor, and the sensitivity of the strain sensor is required to be higher. At present, most of the optical fiber grating strain sensors have low sensitization effect and low sensitivity, which cannot meet the measurement of small strain under the condition of limited installation space. SUMMARY

[0005] Therefore, it is necessary to provide a non-type sensitized fiber grating strain sensor to solve the problems of low sensitivity and low measurement accuracy of the existing optical fiber grating strain sensor under the condition of limited installation space in the prior art.

[0006] The present application provides a non-type sensitized fiber grating strain sensor, comprising:

[0007] The elastic substrate comprises a hairpin, connecting arms, a left end plate, a right end plate and fiber grating sticking arms, the connecting arms are symmetrically arranged on both sides of the hairpin, one end of the connecting arm on one side of the hairpin is connected with the hairpin, and the other end is fixed with the left end plate; one end of the connecting arm on the other side of the hairpin is connected with the hairpin, and the other end is fixed with the right end plate; the fiber grating sticking arms are symmetrically arranged on both sides of the hairpin and fixed with the hairpin, the left end plate, the right end plate and the fiber grating sticking arms form a fixing surface for fixing the fiber grating, and the left end plate and the right end plate are provided with a mounting surface for fixing the measured substrate;

[0008] The fiber grating is fixed on the elastic substrate along the axis of the length direction of the elastic substrate.

[0009] Optionally, the elastic substrate is made of metal material and is integrally formed by wire cutting.

[0010] Optionally, a hollow area is formed in the middle of the circular ring.

[0011] Optionally, optical fiber accommodating grooves are provided on the left end plate and the right end plate at positions corresponding to where the optical fiber Bragg gratings are arranged.

[0012] Optionally, a fiber installation groove for installing the fiber Bragg grating is provided on the fiber Bragg grating pasting arm, the fiber installation groove and the fiber accommodating groove are located on the same axis, and the fiber installation groove is filled with resin glue for fixing the fiber Bragg grating.

[0013] Optionally, the fiber grating is arranged in the hollow area, and the pigtails on both sides of the fiber grating are arranged in the fiber installation groove and the fiber accommodating groove.

[0014] Optionally, a protective sleeve is further included, which is sleeved on the pigtail and embedded in the optical fiber receiving groove.

[0015] Optionally, each corner of the elastic substrate is rounded.

[0016] Optionally, there are four connecting arms, two connecting arms are respectively provided on both sides of the circular loop, and the two connecting arms located on the same side of the circular loop are symmetrical.

[0017] Optionally, there are two fiber Bragg grating pasting arms, one fiber Bragg grating pasting arm is provided on each side of the circular ring, and the fiber Bragg grating pasting arm is located between the two connecting arms on the same side.

[0018] The beneficial effects of the present invention are:

[0019] The non-type enhanced fiber Bragg grating strain sensor of this invention concentrates the long-distance strain of the measured substrate onto a short fiber Bragg grating. The deformation of the measured substrate is amplified by the loop and the connecting arm, significantly improving the sensitivity of the fiber Bragg grating strain sensor. In limited installation space, the key dimensions of the elastic substrate's non-type enhanced structure can be adjusted, enabling the sensitivity and amplification factor of the non-type enhanced fiber Bragg grating strain sensor to be adjusted, achieving higher measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 Schematic diagram of the structure of the non-type enhanced sensitivity fiber Bragg grating strain sensor in the present invention;

[0022] Figure 2 for Figure 1 Schematic diagram of the structure of the elastic substrate;

[0023] Figure 3 for Figure 1 Simplified force analysis diagram of the right end of the elastic substrate;

[0024] Figure 4 Schematic diagram of the dimensions of the non-type enhanced sensitivity fiber Bragg grating strain sensor of the present invention;

[0025] Wherein: 1-elastic substrate, 11-loop ring, 111-hollow area, 12-connecting arm, 13-left end flat plate, 14-right end flat plate, 15-fiber Bragg grating pasting arm, 151-fiber mounting groove, 152-epoxy resin glue, 16-fiber accommodating groove, 2-fiber Bragg grating, 21-pigtail, 3-protective sleeve. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0027] like Figure 1 、 Figure 2 As shown, an embodiment of the present invention provides a non-type enhanced sensitivity fiber Bragg grating strain sensor, which includes: an elastic substrate 1, a fiber Bragg grating 2, the elastic substrate 1 is non-type and has a symmetrical structure, and the fiber Bragg grating 2 is fixed on the elastic substrate 1 along the axis of the length direction of the elastic substrate 1.

[0028] Specifically, the elastic substrate 1 comprises a hairpin ring 11, connecting arms 12, a left end plate 13, a right end plate 14 and fiber grating sticking arms 15, the connecting arms 12 are symmetrically arranged on both sides of the hairpin ring 11, one end of the connecting arm 12 located on one side of the hairpin ring 11 is connected with the hairpin ring 11, and the other end is fixed with the left end plate 13; one end of the connecting arm 12 located on the other side of the hairpin ring 11 is connected with the hairpin ring 11, and the other end is fixed with the right end plate 14; the fiber grating sticking arms 15 are symmetrically arranged on both sides of the hairpin ring 11 and fixed with the hairpin ring 11, the left end plate 13, the right end plate 14 and the fiber grating sticking arms 15 form fixing surfaces for fixing the fiber grating 2, and the left end plate 13 and the right end plate 14 are provided with mounting surfaces for fixing the measured base body.

[0029] In the application, the non-type sensitized fiber grating strain sensor of the application greatly improves the sensitivity of the fiber grating strain sensor by fixing the length of the strain sensor to be greater than the length between the two end fixing points of the fiber grating 2 and combining the non-type structure inside the elastic substrate. Under the condition of limited installation space, by adjusting the key size of the non-type sensitized structure of the elastic substrate, the sensitivity and the sensitization multiple of the non-type sensitized fiber grating strain sensor can be adjusted, and higher measurement accuracy can be realized. The non-type sensitized fiber grating strain sensor can be installed and fixed on the measured base body by structural adhesive pasting, laser welding and bolt connection, and the strain sensor has high sensitivity, low cost, simple structure and convenient installation.

[0030] It should be noted that the distance between the mounting surface of the left end plate 13 and the mounting surface of the right end plate 14 is greater than the distance between the two end fixing points of the fiber grating 2. The purpose of this arrangement is to concentrate the strain of the measured base body on the fiber grating, and the hairpin ring of the elastic substrate cooperates with the four connecting arms to amplify the deformation transmitted to the elastic substrate and transmit it to the fiber grating, and the two effects are realized at the same time to achieve the sensitization effect.

[0031] Further, the elastic substrate 1 is made of metal material, preferably stainless steel material, and is integrally formed by wire cutting processing, which is simple in process.

[0032] Further, during processing, each corner position of the elastic substrate 1 is a rounded corner to avoid stress concentration phenomenon.

[0033] Further, the hairpin ring 11 has a hollow area 111 formed in the middle.

[0034] Further, in the embodiment, there are four connecting arms 12, and two connecting arms 12 are arranged on each side of the hairpin-shaped ring 11.

[0035] Further, the left end plate 13 and the right end plate 14 are provided with fiber accommodating grooves 16 at positions corresponding to the positions where the fiber gratings 2 are arranged.

[0036] Further, in the embodiment, there are two fiber grating sticking arms 15, and one fiber grating sticking arm 15 is arranged on each side of the hairpin-shaped ring 11, and the fiber grating sticking arms 15 are arranged between the two connecting arms 12 on the same side.

[0037] Further, the fiber grating sticking arm 15 is provided with a fiber mounting groove 151 for mounting the fiber grating 2, and the fiber mounting groove 151 is on the same axis as the fiber accommodating groove 16. The fiber mounting groove 151 is filled with epoxy resin glue 152 for fixing the fiber grating 2.

[0038] Specifically, the fiber grating 2 is at the hollow area 111, and the pigtails 21 on both sides of the fiber grating 2 are arranged in the fiber mounting groove 151 and the fiber accommodating groove 16.

[0039] Specifically, the protection sleeve 3 is sleeved on the pigtails 21 and embedded in the fiber accommodating groove 16.

[0040] The manufacturing process of the non-type sensitized fiber grating strain sensor is as follows: the fiber is fixed in the fiber mounting groove 151 by the epoxy resin glue 152, the fiber grating 2 is suspended in the middle of the hollow area 111, after the fiber grating 2 is fixed, the protection sleeve 3 is sleeved on the pigtails 21 at both ends of the fiber grating 2 for protection, and the protection sleeve 3 is fixed in the fiber accommodating groove 16 by quick-drying glue.

[0041] Before the fiber grating 2 is fixed and pasted to the hollow area 111, the coating layer of the pasted fiber needs to be peeled off, and a pre-stress is applied to the fiber grating 2, so that when the elastic substrate 1 produces axial compression deformation, the fiber grating 2 can accurately sense the negative strain.

[0042] The non-type sensitized fiber grating strain sensor needs to fix the elastic substrate 1 on the measured substrate when measuring strain, and the fixing method includes:

[0043] Adopting the way of installing and fixing by gluing, coating high-strength structural glue on the left end plate 13 and the right end plate 14 of the elastic base sheet 1, and pasting the sensor on the measured substrate, when the structural glue is completely solidified, the non-type sensitized fiber grating strain sensor is installed.

[0044] The laser welding way can also be adopted to install and fix, welding the left end plate 13 and the right end plate 14 on the measured substrate, when the material characteristics of the measured substrate are similar to those of the elastic base sheet 1, the welding effect is the best, and during the laser welding process, the elastic base sheet 1 should be kept from deforming as much as possible.

[0045] The bolt connection way can also be adopted to install and fix, setting threaded holes on the left end plate 13, the right end plate 14 and the measured substrate respectively, and fixing the elastic base sheet 1 of the application on the measured substrate through bolts.

[0046] As shown in Figure 3 The elastic base sheet 1 right end half is simplified as a simply supported beam under two concentrated loads, and the calculation process of the strain sensitization multiple of the non-type sensitized fiber grating strain sensor of the application is as follows:

[0047] Supposing that the axial deformation of the right end plate 14 is Δx1, the two connecting arms 12 generate forces F1 and F2 to make the meander ring 11 deformed, the axial deformation of the connecting points A and B of the connecting arms 12 and the meander ring 11 is about equal to Δx1, and the deformation is amplified by the meander ring 11 and applied to the fixed point of the fiber grating 2, so that the axial deformation of the fixed point C of the fiber grating 2 is Δx2.

[0048] According to the displacement superposition principle of the beam in material mechanics, during the axial deformation of the elastic base sheet 1, the points A and B are deformed under the joint action of the two equal concentrated loads F1 and F2, and the fixed point C of the fiber grating 2 will produce the maximum deformation.

[0049] The deflection of the point A under the action of F1 is:

[0050]

[0051] The deflection of the point A under the action of F2 is:

[0052]

[0053] And F1=F2=F, the deflection of the point A is:

[0054]

[0055] Then w A =w B= Δx1, where E is the modulus of elasticity of the elastic substrate 1, I is the moment of inertia of the loop 11, I is the length of the loop 11, and a is the distance from the end of the loop 11 to the point of connection A, B of the connecting arm 12 to the loop 11.

[0056] Similarly, the deflection of the fixed point C of the fiber grating 2 under the action of F1 and F2 is:

[0057]

[0058] Then w c = Δx2. Thus, the sensitivity coefficient K1 of the right end of the loop 11 in the elastic substrate 1 is:

[0059]

[0060] Let the total deformation of the substrate be Δx 基 , and the total deformation of the fiber grating 2 be Δx FBG , then the sensitivity coefficient K2 of the non-type structure inside the non-type elastic substrate 1 is:

[0061]

[0062] Let the gauge length between the left plate 13 and the right plate 14 of the elastic substrate 1 be L1, and the length between the two fixed points of the fiber grating 2 be L2, so the strain ε1 of the substrate structure is:

[0063]

[0064] The strain ε2 generated by the fiber grating 2 is:

[0065]

[0066] Then the sensitivity coefficient K3 of the non-type sensitive fiber grating strain sensor is:

[0067]

[0068] When the fiber grating 2 is in the 1500 nm waveband, the bare grating strain sensitivity is 1.2 pm / με, and the sensitivity of the non-type sensitive fiber grating strain sensor is:

[0069]

[0070] Assuming that the key dimensions of the elastic substrate 1 are as follows Figure 4As shown, the rest of the size can be properly adjusted, the size is brought into K, then the sensitivity of the non-type sensitized fiber grating strain sensor is K=11.478pm / με. Under the condition of limited installation space, the sensitization effect can be changed by adjusting the length l of the loop 11, the distance a between the connecting points A and B of the connecting arm 12 and the loop 11 and the end of the loop 11.

[0071] The present application has the following advantages:

[0072] In the present application, the non-type sensitized fiber grating strain sensor of the present application greatly improves the sensitivity of the fiber grating strain sensor by fixing the length of the strain sensor to be greater than the length between the two fixed points of the fiber grating, and combining the non-type structure inside the elastic substrate. Under the condition of limited installation space, by adjusting the key size of the non-type sensitization structure of the elastic substrate, the sensitivity and the sensitization multiple of the non-type sensitized fiber grating strain sensor can be adjusted, and higher measurement accuracy can be achieved. The non-type sensitized fiber grating strain sensor can be installed and fixed on the measured substrate by structural adhesive paste, laser welding and bolt connection, and the strain sensor has high sensitivity, low cost, simple structure and convenient installation.

[0073] The above is only a preferred embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A "non" type enhanced sensitivity fiber Bragg grating strain sensor, characterized in that: include: An elastic substrate comprises a loop, a connecting arm, a left end plate, a right end plate and a fiber Bragg grating pasting arm, wherein the connecting arms are symmetrically arranged on both sides of the loop, one end of the connecting arm located on one side of the loop is connected to the loop, and the other end is fixed to the left end plate; one end of the connecting arm located on the other side of the loop is connected to the loop, and the other end is fixed to the right end plate; the fiber Bragg grating pasting arms are symmetrically arranged on both sides of the loop and fixed to the loop, a fixing surface for fixing the fiber Bragg grating is formed on the left end plate, the right end plate and the fiber Bragg grating pasting arm, and a mounting surface for fixing to a substrate to be measured is provided on the left end plate and the right end plate; A fiber Bragg grating (FBG) is fixed on the elastic substrate along an axis in the length direction of the elastic substrate; There are four connecting arms, two of which are respectively provided on both sides of the circular loop, and the two connecting arms located on the same side of the circular loop are symmetrical. There are two fiber grating pasting arms, one of which is respectively provided on both sides of the circular loop, and the fiber grating pasting arm is located between the two connecting arms on the same side.

2. The "non" type enhanced sensitivity fiber Bragg grating strain sensor according to claim 1, characterized in that: The elastic substrate is made of metal material and is integrally formed by wire cutting.

3. The "non" type enhanced sensitivity fiber Bragg grating strain sensor according to claim 1, characterized in that: A hollow area is formed in the middle of the circular ring.

4. The "non" type enhanced sensitivity fiber Bragg grating strain sensor according to claim 3, characterized in that: Fiber accommodating grooves are provided at positions of the left end plate and the right end plate corresponding to where the fiber gratings are arranged.

5. The "non" type enhanced sensitivity fiber Bragg grating strain sensor according to claim 4, characterized in that: The fiber grating pasting arm is provided with a fiber installation groove for installing the fiber grating. The fiber installation groove and the fiber accommodating groove are located on the same axis. The fiber installation groove is filled with resin glue for fixing the fiber grating.

6. The "non" type enhanced sensitivity fiber Bragg grating strain sensor according to claim 5, characterized in that: The fiber grating is arranged at the hollow area, and the pigtails on both sides of the fiber grating are arranged in the fiber installation groove and the fiber accommodating groove.

7. The "non" type enhanced sensitivity fiber Bragg grating strain sensor according to claim 6, characterized in that: It also includes a protective sleeve, which is sleeved on the pigtail and embedded in the optical fiber accommodating groove.

8. The "non" type enhanced sensitivity fiber Bragg grating strain sensor according to claim 1, characterized in that: Each corner of the elastic substrate is rounded.

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