CN115824075A - Non-type sensitization fiber grating strain sensor - Google Patents
Non-type sensitization fiber grating strain sensor Download PDFInfo
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- CN115824075A CN115824075A CN202211041459.7A CN202211041459A CN115824075A CN 115824075 A CN115824075 A CN 115824075A CN 202211041459 A CN202211041459 A CN 202211041459A CN 115824075 A CN115824075 A CN 115824075A
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Abstract
The invention provides a non-type sensitization fiber grating strain sensor, which comprises an elastic substrate, a flexible substrate and a sensing device, wherein the elastic substrate comprises a loop ring, connecting arms, a left end flat plate, a right end flat plate and fiber grating pasting arms; the fiber grating pasting arms are arranged on two sides of the circular ring and fixed with the circular ring, fixing surfaces for fixing the fiber gratings are formed on the left end flat plate, the right end flat plate and the fiber grating pasting arms, and mounting surfaces for fixing the fiber gratings with a measured substrate are arranged on the left end flat plate and the right end flat plate; and the fiber grating is fixed on the elastic substrate along the axis of the elastic substrate in the length direction. The invention has obvious sensitization effect, and can improve the sensitivity and the measurement precision of the fiber grating strain sensor under the condition of limited installation space.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a non-type sensitization optical fiber grating strain sensor.
Background
In structural health monitoring in the fields of civil engineering, aerospace, petrochemical industry, ship industry and the like, strain is one of important physical parameters. By monitoring the strain in real time, real-time conditions such as equipment, mechanical structures, track running states and the like can be known in time, and safety accidents are prevented.
The fiber grating sensing technology has the characteristics of electric insulation, electromagnetic interference resistance, corrosion resistance, strong stability, small volume, light weight and the like, and is widely used for health monitoring of various structures, and according to the fiber grating strain sensing principle, the strain measurement sensitivity of a bare fiber grating is 1.2 pm/mu epsilon, but the strain measurement sensitivity and the stability requirements in practical application cannot be met.
In the health monitoring of large-scale structure, the structure deflection is little, and the strain that produces is little to strain sensor installation space is limited, can not improve the sensitization effect through changing strain sensor fixed distance, has higher requirement to strain sensor's sensitivity. At present, most of fiber grating strain sensors are not obvious in sensitivity enhancement effect and low in sensitivity, and cannot meet the requirement of measuring micro strain under the condition of being limited by installation space.
Disclosure of Invention
In view of this, it is necessary to provide a non-type sensitivity-enhanced fiber grating strain sensor, which solves the problems of low sensitivity and low measurement accuracy of the fiber grating strain sensor in the prior art under the condition of limited installation space.
The invention provides a non-type sensitization fiber grating strain sensor, comprising:
the elastic substrate comprises a loop ring, connecting arms, a left end flat plate, a right end flat plate and fiber bragg grating pasting arms, wherein the connecting arms are symmetrically arranged on two sides of the loop ring, one end of each connecting arm positioned on one side of the loop ring is connected with the loop ring, and the other end of each connecting arm is fixed with the left end flat plate; one end of the connecting arm positioned on the other side of the loop-shaped ring is connected with the loop-shaped ring, and the other end of the connecting arm is fixed with the right end flat plate; the fiber grating pasting arms are symmetrically arranged on two sides of the loop-shaped ring and fixed with the loop-shaped ring, fixing surfaces for fixing fiber gratings are formed on the left end flat plate, the right end flat plate and the fiber grating pasting arms, and mounting surfaces for fixing the fiber gratings with a tested substrate are arranged on the left end flat plate and the right end flat plate;
and the fiber grating is fixed on the elastic substrate along the axis of the elastic substrate in the length direction.
Optionally, the elastic substrate is made of a metal material and is integrally formed by wire cutting.
Optionally, a hollow-out area is formed in the middle of the loop.
Optionally, the left end flat plate and the right end flat plate are provided with optical fiber accommodating grooves at positions corresponding to the optical fiber gratings.
Optionally, an optical fiber mounting groove for mounting the optical fiber grating is formed in the optical fiber grating pasting arm, the optical fiber mounting groove and the optical fiber accommodating groove are located on the same axis, and the optical fiber mounting groove is filled with resin glue for fixing the optical fiber grating.
Optionally, the fiber grating is disposed at the hollow area, and the tail fibers on two sides of the fiber grating are disposed in the fiber mounting groove and the fiber accommodating groove.
Optionally, the optical fiber connector further comprises a protective sleeve, wherein the protective sleeve is sleeved on the tail optical fiber and embedded in the optical fiber accommodating groove.
Optionally, each corner position of the elastic substrate is a round corner.
Optionally, the connecting device is provided with four connecting arms, two connecting arms are respectively arranged on two sides of the loop, and the two connecting arms located on the same side of the loop are symmetrical.
Optionally, two fiber grating pasting arms are provided, two fiber grating pasting arms are respectively arranged on two sides of the loop, and the fiber grating pasting arms are located between the two connecting arms on the same side.
The invention has the beneficial effects that:
the non-type sensitization fiber grating strain sensor concentrates the long-distance strain of the measured substrate on the short fiber grating, and amplifies the deformation of the measured substrate through the matching of the annular ring and the connecting arm, thereby greatly improving the sensitivity of the fiber grating strain sensor. Under the condition of limited installation space, the key size of the non-type sensitization structure of the elastic substrate can be adjusted, the sensitivity and sensitization multiple of the non-type sensitization fiber grating strain sensor can be adjusted, and higher measurement precision can be realized.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a non-type sensitization fiber grating strain sensor according to the present invention;
FIG. 2 is a schematic view of the structure of the elastomeric substrate of FIG. 1;
FIG. 3 is a simplified force analysis diagram of the right end of the resilient substrate of FIG. 1;
FIG. 4 is a schematic diagram showing the dimensions of a non-type sensitization fiber grating strain sensor according to the present invention;
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 grating pasting arm, 151-fiber mounting groove, 152-epoxy resin glue, 16-fiber accommodating groove, 2-fiber grating, 21-tail fiber and 3-protective sleeve.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.
As shown in fig. 1 and fig. 2, an embodiment of the present invention provides a non-type sensitized fiber grating strain sensor, which includes: the optical fiber grating comprises an elastic substrate 1 and an optical fiber grating 2, wherein the elastic substrate 1 is in a non-word shape and is in a symmetrical structure, and the optical fiber grating 2 is fixed on the elastic substrate 1 along the axis of the elastic substrate 1 in the length direction.
Specifically, the elastic substrate 1 includes a loop 11, a connecting arm 12, a left end flat plate 13, a right end flat plate 14 and a fiber grating pasting arm 15, the connecting arm 12 is symmetrically arranged on two sides of the loop 11, one end of the connecting arm 12 located on one side of the loop 11 is connected with the loop 11, and the other end is fixed with the left end flat plate 13; one end of the connecting arm 12 positioned at the other side of the loop 11 is connected with the loop 11, and the other end is fixed with the right end flat plate 14; the fiber grating pasting arm 15 is symmetrically arranged on two sides of the loop 11 and fixed with the loop 11, the left end flat plate 13, the right end flat plate 14 and the fiber grating pasting arm 15 form a fixing surface for fixing the fiber grating 2, and the left end flat plate 13 and the right end flat plate 14 are provided with installation surfaces for fixing a measured substrate.
In the invention, the fixed length of the non-type sensitization fiber grating strain sensor is greater than the length between the fixed points at two ends of the fiber grating 2, and the non-type sensitization fiber grating strain sensor is combined with the non-type structure in the elastic substrate to greatly improve the sensitivity of the fiber grating strain sensor. Under the condition of limited installation space, the adjustment of the sensitivity and the sensitivity enhancement multiple of the non-type sensitivity enhancement fiber grating strain sensor can be realized by adjusting the key size of the non-type sensitivity enhancement structure of the elastic substrate, and higher measurement precision can be realized. The non-type sensitization fiber grating strain sensor can be installed and fixed on a measured base body in structural adhesive sticking, laser welding and bolt connecting modes, and is high in sensitivity, low in cost, simple in structure and convenient to install.
It should be noted that the distance between the mounting surface of the left end flat plate 13 and the mounting surface of the right end flat plate 14 is greater than the distance between the fixing points at the two ends of the fiber grating 2, so that the strain of the measured substrate can be concentrated on the fiber grating, and the deformation transmitted to the elastic substrate is amplified and transmitted to the fiber grating by the matching of the loop-shaped ring of the elastic substrate and the four connecting arms, and the two functions simultaneously realize the sensitivity enhancing effect.
Furthermore, the elastic substrate 1 is made of metal materials, preferably stainless steel materials, and is integrally formed by wire cutting, so that the process is simple.
Furthermore, when the elastic substrate 1 is processed, each corner position is a fillet, so that the stress concentration phenomenon is avoided.
Further, a hollow-out area 111 is formed in the middle of the clip 11.
Further, in the present embodiment, there are four connecting arms 12, and two connecting arms 12 are respectively disposed on two sides of the loop 11. The two connecting arms 12 on the same side of the loop 11 are symmetrical.
Further, the left end flat plate 13 and the right end flat plate 14 are provided with an optical fiber accommodating groove 16 at positions corresponding to the optical fiber grating 2.
Further, in this embodiment, there are two fiber grating pasting arms 15, two sides of the loop 11 are respectively provided with one fiber grating pasting arm 15, and the fiber grating pasting arms 15 are located between the two connecting arms 12 on the same side.
Further, an optical fiber installation groove 151 for installing the optical fiber grating 2 is formed in the optical fiber grating pasting arm 15, and the optical fiber installation groove 151 and the optical fiber accommodating groove 16 are located on the same axis. The optical fiber installation groove 151 is filled with an epoxy adhesive 152 for fixing the fiber bragg grating 2.
Specifically, the fiber bragg grating 2 is located at the hollow-out area 111, and the pigtails 21 at two sides of the fiber bragg grating 2 are disposed in the fiber mounting groove 151 and the fiber accommodating groove 16.
Specifically, the optical fiber connector further comprises a protective sleeve 3, wherein the protective sleeve 3 is sleeved on the tail optical fiber 21 and embedded in the optical fiber accommodating groove 16.
The manufacturing process of the non-type sensitization fiber grating strain sensor comprises the following steps: fix optic fibre in optic fibre mounting groove 151 through epoxy glue 152, fiber grating 2 should hang in the middle of the fretwork district 111 between two parties, after finishing fiber grating 2 is fixed, the suit is in fiber grating 2 both ends the last 21 of tail optical fiber go up protective sleeve 3 protects, and will through rapid-curing cutback glue protective sleeve 3 fixes in optic fibre storage tank 16.
Before the fiber grating 2 is fixedly adhered to the hollow-out area 111, a coating layer adhered with an optical fiber needs to be peeled off, and prestress is applied to the fiber grating 2, so that the fiber grating 2 can accurately sense negative strain when the elastic substrate 1 generates axial compression deformation.
The non-type sensitization fiber grating strain sensor of the invention needs to fix the elastic substrate 1 on a matrix to be measured when measuring strain, and the fixing mode comprises the following steps:
and (2) adopting an adhesive mode for installation and fixation, coating high-strength structural adhesive on the left end flat plate 13 and the right end flat plate 14 of the elastic substrate 1, adhering the sensor on a base body to be detected, and completing the installation of the non-type sensitization fiber grating strain sensor after the structural adhesive is completely cured.
The left end flat plate 13 and the right end flat plate 14 can also be fixedly installed by laser welding, and are welded on a base body to be measured, when the material characteristics of the base body to be measured and the elastic substrate 1 are similar, the welding effect is the best, and in the laser welding process, the elastic substrate 1 is kept from deforming as much as possible.
Or the elastic substrate 1 can be fixed by adopting a bolt connection mode, threaded holes are respectively formed in the left end flat plate 13, the right end flat plate 14 and the base body to be tested, and the elastic substrate is fixed on the base body to be tested through bolts.
As shown in fig. 3, the half of the right end of the elastic substrate 1 is simplified into a simple beam subjected to two concentrated loads, and the calculation process of the strain sensitization multiple of the non-type sensitization fiber grating strain sensor of the invention is as follows:
let the axial deformation of the right end plate 14 be Δ x 1 Two of said connecting arms 12 generating a force F respectively 1 、F 2 The annular loop 11 is deformed, and the axial deformation quantity of the joints A and B of the connecting arms 12 and the annular loop 11 is approximately equal to deltax 1 The deformation is applied to the fixing point of the fiber grating 2 by the amplification of the loop 11, so that the axial deformation amount generated at the fixing point C on the fiber grating 2 side is Δ x 2 。
According to the displacement superposition principle of a beam in the mechanics of materials, in the axial deformation process of the elastic substrate 1, the points A and B are positioned at two equal concentrated loads F 1 、F 2 The maximum deformation will be generated at the point C where the fiber grating 2 is fixed.
At F 1 The deflection of the point A under the action is as follows:
at F 2 The deflection of the point A under the action is as follows:
and F 1 ＝F 2 And F, the deflection of the point A is as follows:
then w A ＝w B ＝Δx 1 Where E is the elastic modulus 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 points a and B at the connection point of the connecting arm 12 and the loop 11 to the end of the loop 11.
The deflection of the fixed point C of the fiber grating 2 under the action of F1 and F2 can be obtained by the same method as follows:
then w c ＝Δx 2 . From this, it can be obtained that the coefficient of sensitization K of the loop 11 at the right end in the elastic substrate 1 1 Comprises the following steps:
is provided with a base bodyTotal deformation of Δ x Base of The total deformation of the fiber grating 2 is Deltax FBG Then the sensitization coefficient K of the non-type structure inside the non-type elastic substrate 1 2 Comprises the following steps:
setting the gauge length between the left end flat plate 13 and the right end flat plate 14 of the elastic substrate 1 as L 1 The length between the two ends of the fiber grating 2 and the fixed points is L 2 Such that the strain ε of the matrix structure 1 Comprises the following steps:
strain epsilon generated by the fiber grating 2 2 Comprises the following steps:
the sensitization coefficient K of the non-type sensitization fiber grating strain sensor 3 Comprises the following steps:
when the fiber bragg grating 2 is in a 1500nm wave band, the strain sensitivity of the bare grating is 1.2 pm/mu epsilon, and then the sensitivity of the non-type sensitization fiber bragg grating strain sensor is as follows:
assuming that the critical dimensions of the elastic substrate 1 are as shown in fig. 4, the remaining dimensions can be adjusted appropriately, bringing the dimensions into K, and the sensitivity of the non-type sensitized fiber grating strain sensor is K =11.478 pm/. Mu.epsilon. Under the condition of limited installation space, the sensitization effect can be changed by adjusting the length l of the loop-shaped ring 11 and the distances a between the points A and B of the connection between the connecting arm 12 and the loop-shaped ring 11 and the tail end of the loop-shaped ring 11.
The invention has the beneficial effects that:
in the invention, the fixed length of the non-type sensitization fiber grating strain sensor is greater than the length between the fixed points at two ends of the fiber grating, and the non-type sensitization fiber grating strain sensor is combined with the non-type structure in the elastic substrate to greatly improve the sensitivity of the fiber grating strain sensor. Under the condition of limited installation space, the adjustment of the sensitivity and the sensitivity enhancement multiple of the non-type sensitivity enhancement fiber grating strain sensor can be realized by adjusting the key size of the non-type sensitivity enhancement structure of the elastic substrate, and higher measurement precision can be realized. The non-type sensitization fiber grating strain sensor can be installed and fixed on a measured base body in the modes of structural adhesive adhesion, laser welding and bolt connection, and is high in sensitivity, low in cost, simple in structure and convenient to install.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also included in the scope of the present invention.
Claims (10)
1. A non-type sensitization fiber grating strain sensor is characterized by comprising:
the elastic substrate comprises a loop ring, connecting arms, a left end flat plate, a right end flat plate and fiber bragg grating pasting arms, wherein the connecting arms are symmetrically arranged on two sides of the loop ring, one end of each connecting arm positioned on one side of the loop ring is connected with the loop ring, and the other end of each connecting arm is fixed with the left end flat plate; one end of the connecting arm positioned on the other side of the loop-shaped ring is connected with the loop-shaped ring, and the other end of the connecting arm is fixed with the right end flat plate; the fiber grating pasting arms are symmetrically arranged on two sides of the loop-shaped ring and fixed with the loop-shaped ring, fixing surfaces for fixing fiber gratings are formed on the left end flat plate, the right end flat plate and the fiber grating pasting arms, and mounting surfaces for fixing the fiber gratings with a tested substrate are arranged on the left end flat plate and the right end flat plate;
and the fiber grating is fixed on the elastic substrate along the axis of the elastic substrate in the length direction.
2. The non-type sensitized fiber grating strain sensor according to claim 1, wherein the elastic substrate is made of metal and is integrally formed by wire cutting.
3. The non-type sensitized fiber grating strain sensor according to claim 1, wherein a hollow-out area is formed in the middle of the loop.
4. The non-type sensitization fiber grating strain sensor according to claim 1, wherein fiber accommodating grooves are formed at positions of the left end flat plate and the right end flat plate corresponding to the fiber grating.
5. The non-type sensitivity-enhanced fiber grating strain sensor according to claim 4, wherein the fiber grating pasting arm is provided with a fiber mounting groove for mounting the fiber grating, the fiber mounting groove and the fiber accommodating groove are located on the same axis, and the fiber mounting groove is filled with resin glue for fixing the fiber grating.
6. The non-type sensitization fiber grating strain sensor according to claim 5, wherein the fiber grating is arranged at the hollow area, and tail fibers at two sides of the fiber grating are arranged in the fiber mounting groove and the fiber accommodating groove.
7. The non-type sensitized fiber grating strain sensor according to claim 6, further comprising a protective sleeve, wherein the protective sleeve is sleeved on the tail fiber and embedded in the fiber accommodating groove.
8. The non-form, sensitized fiber grating strain sensor according to claim 1, characterized in that each corner position of said elastic substrate is rounded.
9. The non-type sensitized fiber grating strain sensor according to claim 1, wherein there are four connecting arms, two connecting arms are respectively disposed on two sides of the loop, and two connecting arms on the same side of the loop are symmetrical.
10. The non-type sensitized fiber grating strain sensor according to claim 9, wherein there are two fiber grating pasting arms, one on each side of the loop, and the fiber grating pasting arm is located between the two connecting arms on the same side.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117073571A (en) * | 2023-10-18 | 2023-11-17 | 武汉理工大学 | Temperature self-compensating optical fiber strain sensor with hinge and stepped reducing grating combined |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117073571A (en) * | 2023-10-18 | 2023-11-17 | 武汉理工大学 | Temperature self-compensating optical fiber strain sensor with hinge and stepped reducing grating combined |
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