CN103940359B - Fiber grating differential strain gauge and manufacturing and using method thereof - Google Patents

Abstract

The invention provides a fiber grating differential strain gauge. The fiber grating differential strain gauge comprises a first fiber grating, a second fiber grating, an elastomer and installation arms, wherein the elastomer is a deformable body which is hollow and is in axial symmetry and central symmetry, the two ends of the first fiber grating are bonded to one side of the elastomer, the two ends of the second fiber grating are bonded to the other side of the elastomer, the first fiber grating and the second fiber grating are perpendicular to each other, grating bodies of the fiber gratings penetrate through the center of the elastomer and do not make contact with each other, the installation arms are fixed to the two sides of the elastomer, the installation arms and the first fiber grating are arranged in the same direction, the thickness of each installation arm is larger than that of the elastomer, and open grooves which penetrate through a tail fiber of the first fiber grating are formed in the installation arms. According to the fiber grating differential strain gauge, the two-end bonding mode is adopted for the structure, it is ensured that stress of grating parts is uniform, the chirp phenomenon is eliminated, detection accuracy is ensured, a manufacturing process of the fiber grating differential strain gauge can be simpler through the two-end bonding mode, and operation is easier.

Description

A kind of fiber grating differential strain piece and its making and use method

Technical field

The invention belongs to Fibre Optical Sensor part is and in particular to a kind of fiber grating differential strain piece and its making and user Method.

Background technology

Force analysis or monitoring in order to carry out structure is subject to the component of mechanical load, often uses resistance strain gage detection to be added The strain of the structural detail of load power.This resistance strain gage is made up of substrate, sensitive grid, cover layer and lead-out wire, sensitive grid It is the non-sensitive part that resistance-strain amount is converted into resistance change；Substrate and cover layer have positioning and protective resistance silk with tested The effect of body insulation；Lead plays a part to connect measure traverse line；In order to detect and load related strain, these resistance-strains Piece is laid on monitored component, and by measure sensitive grid resistance variations transformation for strain is the signal of telecommunication, this signal with Strain or active force are proportional.The features such as resistance strain gage has small volume, is easily installed, but it is for electromagnetic field or high-voltage field Impact very sensitive, and inflammable and explosive occasion do not allow use.

Optical fiber sensing technology is the important invention producing with Fibre Optical Communication Technology, because this technology uses The mode of optical signal modulation, therefore substantially possesses good anti-electromagnetic interference capability, deeply grinding with processing technology simultaneously Study carefully and improve so as to possess the features such as wide dynamic monitoring scope, high sensitivity, optical signal transmission distance, be easy to networking and realize Distributed measurement, these advantages are engineering monitoring and provide effective solution, have therefore suffered from domestic and international research worker Extensive concern.But, the engineer applied of fiber-optic grating sensor also exists following problem: (1) is due to fiber grating Sensor for temperature and strain are all sensitive, need to solve the problems, such as temperature and strain cross sensitivity during application.(2) fiber grating itself There is certain length, if be directly fixed on monitored component, it is difficult to ensure that the strain field suffered by grating is uniform , thus it is easily caused the chirped of fiber grating, the precision of impact measurement.(3) directly fiber grating is solidified on being supervised Survey on body, be not easy to through engineering approaches construction.

Content of the invention

It is contemplated that overcoming the above-mentioned problem of fiber grating sensing technology, provide that a kind of structure is simple, packaging technology is easy FBG strain gauge in operation.

The present invention by solving the technical scheme that above-mentioned technical problem is taken is: a kind of fiber grating differential strain piece, its Be characterised by: it includes the first fiber grating, the second fiber grating, elastomer and installing arm, elastomer be a hollow, both Axial symmetry centrosymmetric deformable body again；The two ends of the wherein first fiber grating are pasted onto the one side of elastomer, the second optical fiber light The two ends of grid are pasted onto the another side of elastomer, and the first fiber grating and the second fiber grating are mutually perpendicular to, and the grating of the two is equal By the center of elastomer and do not contact；Described installing arm is fixed on the both sides of elastomer, and with the first fiber grating same One direction；The thickness of installing arm is more than the thickness of elastomer, and installing arm is provided with for the tail optical fiber through the first fiber grating Fluting.

By such scheme, first, second fiber grating is respectively equipped with fluting with the affixed points of elastomer.

By such scheme, described elastomer is circular deformable body or hollow regular polygon deformable body.

A kind of manufacture method of above-mentioned fiber grating differential strain piece it is characterised in that:

It is respectively provided with a cross-notching on the two sides of elastomer, the line of every cross-notching is all by the center of elastomer；

Installing arm is fixed on the both sides of elastomer, and installing arm is also provided with slotting, the fluting of installing arm and elastomer its In a pair of fluting on the same line；

Through pre-stretching the first fiber grating along elastomer one side fluting place, its grating be located at elastomer center On axle and its tail optical fiber is placed on gluing in elastomer and the fluting of installing arm and fixes；Through pre-stretching the second fiber grating along bullet The fluting of gonosome another side is placed, and its grating is located on the central shaft of elastomer and its tail optical fiber is placed in the fluting of elastomer and applies Glue is fixed.

The using method of the fiber grating differential strain piece being made using above-mentioned manufacture method is:

Fiber grating differential strain piece is fixed on monitored body by installing arm, monitored body strain changes and causes change The deformation of shape ring, and then so that the first fiber grating and the second fiber bragg grating center wavelength difference is changed, by detecting two light The variable quantity of fine raster center wavelength difference, draws dependent variable produced by monitored body.

The invention has the benefit that

1st, utilize the FBG strain gauge of present configuration and manufacture method, make the difference of two grating wavelength variable quantities only with The size linear correlation of foil gauge stress, and temperature independent, eliminate the cross sensitivity of strain and temperature；Present configuration is adopted The mode pasted with two ends, it is ensured that grating position uniform force, eliminates chirped phenomenon, thus ensure that the precision of detection, The mode that two ends are pasted also can make the processing technology of foil gauge simpler it is easier to operation, and this will be optical fiber grating sensing skill The promotion and application of art provide strong support；Installing arm is slightly thicker than elastomer, to ensure that foil gauge only perceived by installing arm The stress of monitored body, thus drive elastomer to produce deformation, unbalance stress when can eliminate foil gauge directly contact monitored body The accuracy of impact foil gauge and concordance.

2nd, first, second fiber grating must be pasted on after being pre-stretched on elastomer, and elastomer so can be made to answer to positive and negative Become and all can achieve perception.

Brief description

Fig. 1 is the structural representation of one embodiment of the invention.

Fig. 2 is the top view of Fig. 1.

Fig. 3 is the structural representation of another embodiment of the present invention.

Fig. 4 is the top view of Fig. 3.

In figure: 1- first fiber grating, 2- second fiber grating, 3- cyclical deformation body, 4- first installing arm, 5- second pacifies Dress arm

Specific embodiment

With reference to instantiation and accompanying drawing, the present invention will be further described.

A kind of fiber grating differential strain piece it is characterised in that: it includes the first fiber grating, the second fiber grating, bullet Gonosome and installing arm, elastomer is a hollow, not only axial symmetry but also centrosymmetric deformable body；Wherein first fiber grating Two ends are pasted onto the one side of elastomer, and the two ends of the second fiber grating are pasted onto the another side of elastomer, the first fiber grating and Second fiber grating is mutually perpendicular to, and the grating of the two all by the center of elastomer and does not contact；Described installing arm is fixed on The both sides of elastomer, and with the first fiber grating in same direction；The thickness of installing arm is more than the thickness of elastomer, in installing arm It is provided with the fluting for the tail optical fiber through the first fiber grating.

Embodiment one:

Fig. 1 be the embodiment of the present invention one structural representation, Fig. 2 be Fig. 1 top view, it include the first fiber grating 1, Second fiber grating 2, elastomer and installing arm, elastomer is for being steel used in a circular deformable body 3(the present embodiment Circular deformable body)；The two ends of the wherein first fiber grating 1 are pasted onto the one side of circular deformable body 3, the second fiber grating 2 two ends are pasted onto the another side of circular deformable body 3, and the first fiber grating 1 and the second fiber grating 2 are mutually perpendicular to, the two Grating all by the circle core shaft of circular deformable body 3 and do not contact；Described installing arm is fixed on the two of circular deformable body 3 Side, is divided into the first installing arm 4 and the second installing arm 5, and with the first fiber grating 1 in same direction；The thickness of installing arm is bigger In the thickness of (thickness difference is more than the diameter of optical fiber) circular deformable body 3, installing arm is provided with for through the first optical fiber The fluting of the tail optical fiber of grating 1.The extraction for the second fiber grating 2 tail optical fiber for the fluting is also had on circular deformable body 3.

As the end positions loading force f of the first fiber grating solidification on circular deformable body, the first fiber grating The dependent variable producing with the second fiber grating is respectively:

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_1=\frac{{\mathrm{\δl}}_1}{2r}=\frac{{\mathrm{\π}}^2-8}{8\mathrm{\π}}\frac{{\mathrm{fr}}^2}{\mathrm{ei}}\\ {\mathrm{\ϵ}}_2=\frac{{\mathrm{\δl}}_2}{2r}=-\frac{{\mathrm{\π}}^2-8}{8\mathrm{\π}}\frac{{\mathrm{fr}}^2}{\mathrm{ei}}\end{array}\right.---\left(1\right),$

In formula 1, ε₁And ε₂For the dependent variable of the first fiber grating and the generation of the second fiber grating, δ l₁With δ l₂It is respectively First fiber grating and the dependent variable of the second fiber grating generation, e is the elastic modelling quantity of Shape-changeable ring, and r is circular Shape-changeable ring Internal-and external diameter average, i is the rotary inertia in Shape-changeable ring section face.

According to Monitoring-fiber Bragg Grating axial strain sensing principle, the then center of the first fiber grating and the second fiber grating Wavelength amount of movement is respectively as follows:

$\left\{\begin{array}{c}\frac{{\mathrm{\δ\λ}}_1}{{\mathrm{\λ}}_1}=(1-p_e){\mathrm{\ϵ}}_1+{\mathrm{\δt}}_1(\mathrm{\α}+\mathrm{\ξ})\\ \frac{{\mathrm{\δ\λ}}_2}{{\mathrm{\λ}}_2}=(1-p_e){\mathrm{\ϵ}}_2+{\mathrm{\δt}}_2(\mathrm{\α}+\mathrm{\ξ})\end{array}\right.---\left(2\right),$

λ in formula₁And λ₂It is respectively the centre wavelength of the first fiber grating and the second fiber grating, δ λ₁With δ λ₂It is respectively First fiber grating and the drift value of the second fiber bragg grating center wavelength, p_eFor elasto-optical coefficient, δ t₁With δ t₂It is respectively the first light The temperature variation of fine grating and the second fiber grating is it is contemplated that two gratings are under equivalent environment it is believed that δ t₁=δt₂, Introduce parameter first fiber grating and the second fiber bragg grating center wavelength difference d=λ₁-λ₂, then in equation 2 above, two equatioies subtract each other:

$\frac{{\mathrm{\δd\λ}}_1-{\mathrm{\δ\λ}}_{2}d}{{\mathrm{\λ}}_1{\mathrm{\λ}}_2}=(1-p_e)({\mathrm{\ϵ}}_1-{\mathrm{\ϵ}}_2)---\left(3\right),$

δ λ is understood by grating parameter feature₂d<<λ₁λ₂, omit event, and formula 1 substituted in formula 3:

$\mathrm{\&delta;d}=\frac{{\mathrm{\&pi;}}^2-8}{4\mathrm{\&pi;}}\frac{(1-p_e){\mathrm{\&lambda;}}_1{\mathrm{fr}}^2}{\mathrm{ei}}---\left(4\right),$

In formula, δ d is the first fiber grating and the variable quantity of the second fiber bragg grating center wavelength difference, δ λ₂For the second optical fiber The variable quantity of raster center wavelength, it is clear that not containing temperature term, the FBG strain gauge made using this structure in formula 4, makes two The size linear correlation only with foil gauge stress for the difference of grating wavelength variable quantity, and temperature independent, eliminate strain and temperature Cross sensitivity.

The manufacture method of above-mentioned fiber grating differential strain piece is as follows: is respectively provided with a pair on the two sides of circular deformable body Fluting, the line of every cross-notching is all by the center of circular deformable body；Installing arm is fixed on the both sides of circular deformable body, and Installing arm is also provided with slotting, and the fluting of installing arm is slotted on the same line with the one pair of which of circular deformable body；Through pre- First fiber grating of stretching is placed along the fluting of circular deformable body one side, and its grating is located at the circle core shaft of circular deformable body Upper and its tail optical fiber is placed on gluing in circular deformable body and the fluting of installing arm and fixes；The second fiber grating through pre-stretching Fluting along circular deformable body another side is placed, and its grating is located on the circle core shaft of circular deformable body and its tail optical fiber is placed on In the fluting of circular deformable body, gluing is fixed.

The using method of above-mentioned fiber grating differential strain piece is: fiber grating differential strain piece is fixed by installing arm On monitored body, using the stress of below equation acquisition fiber grating differential strain piece:

$\mathrm{\&delta;d}=\frac{{\mathrm{\&pi;}}^2-8}{4\mathrm{\&pi;}}\frac{(1-p_e){\mathrm{\&lambda;}}_1{\mathrm{fr}}^2}{\mathrm{ei}}.$

Using the direct bonding method in grating position, it is difficult to ensure that the uniformity of alite paste thickness in manufacturing process, easily Cause fiber grating chirped, this will directly influence accuracy of detection.The present invention is by the way of the stickup of two ends it is ensured that grating Position uniform force, eliminates chirped phenomenon, thus ensure that the precision of detection, the mode that two ends are pasted also can make foil gauge Processing technology simpler it is easier to operation.In the present invention, the first fiber grating and the second fiber grating must be pre-stretched ability It is pasted on circular deformable body, foil gauge so can be made to align negative strain and all can achieve perception.

The present invention can change foil gauge by changing the size (such as internal diameter, external diameter and thickness etc.) of circular deformable body Sensitivity, for be fabricated to different sensitivity foil gauge provide facility.In addition, the present invention conducts stress using installing arm, When can eliminate foil gauge directly contact monitored body, unbalance stress affects accuracy and the concordance of foil gauge.

Embodiment two:

The present embodiment structure and principle are all essentially identical with embodiment one, and its difference is: described elastomer is Hollow regular polygon deformable body.

It is that as a example square deformable body, as shown in Figure 3 and Figure 4, it includes the first fiber grating 1, second by square Fiber grating 2, elastomer, the first installing arm 4 and the second installing arm 5, elastomer is a square deformable body 3；The present embodiment Installation method identical with the installation method of embodiment one.The present embodiment is fixed on monitored body by installing arm, utilizes Below equation obtains the differential variable quantity of raster center wavelength of fiber grating differential strain piece:

$\mathrm{\&delta;d}=\frac{(1-p_e){\mathrm{\&lambda;}}_1{\mathrm{fa}}^2}{12\sqrt{2}\mathrm{ei}};$

In formula: δ d is the first fiber grating and the variable quantity of the second fiber bragg grating center wavelength difference, and f is that fiber grating is poor The stress of dynamic strain piece, p_eFor elasto-optical coefficient, λ₁For the centre wavelength of the first fiber grating, a is the foursquare length of side, and e is pros The elastic modelling quantity of deformation body, i is the rotary inertia of square deformation body section.

Above example by way of example only, as long as elastomer is hollow, not only axial symmetry but also centrosymmetric deformable body All can reach the purpose of the present invention.The scheme that the FBG strain gauge of the present invention adopts, solve fiber grating pair strain and Temperature cross-over sensitive issue, moreover it is possible to be easily achieved processing and fabricating while ensureing accuracy of detection, this will pass for fiber grating The promotion and application of sense technology provide strong support.

Claims (2)

1. a kind of manufacture method of fiber grating differential strain piece, described fiber grating differential strain piece includes the first optical fiber light Grid, the second fiber grating, elastomer and installing arm, elastomer is a hollow, not only axial symmetry but also centrosymmetric deformable body； The two ends of the wherein first fiber grating are pasted onto the one side of elastomer, and the two ends of the second fiber grating are pasted onto the another of elastomer Face, the first fiber grating and the second fiber grating are mutually perpendicular to, and the grating of the two all by the center of elastomer and does not contact；Institute The installing arm stated is fixed on the both sides of elastomer, and with the first fiber grating in same direction；The thickness of installing arm is more than elasticity The thickness of body, installing arm is provided with the fluting for the tail optical fiber through the first fiber grating；It is characterized in that:

It is respectively provided with a cross-notching on the two sides of elastomer, the line of every cross-notching is all by the center of elastomer；

Installing arm is fixed on the both sides of elastomer, and installing arm is also provided with slotting, the fluting of installing arm and wherein the one of elastomer Cross-notching is on the same line；

Through pre-stretching the first fiber grating along elastomer one side fluting place, its grating be located at elastomer central shaft on And its tail optical fiber is placed on gluing in elastomer and the fluting of installing arm and fixes；Through pre-stretching the second fiber grating along elastomer The fluting of another side is placed, and its grating is located on the central shaft of elastomer and its tail optical fiber is placed in the fluting of elastic strain piece and applies Glue is fixed.

2. utilize the fiber grating differential strain piece that the manufacture method of the fiber grating differential strain piece described in claim 1 makes Using method be:

Fiber grating differential strain piece is fixed on monitored body by installing arm, monitored body strain changes and causes elastomer Deformation, and then so that the first fiber grating and the second fiber bragg grating center wavelength difference is changed, by detecting two optical fiber light The variable quantity of grid central wavelength difference, draws dependent variable produced by monitored body.