Optical fiber grating temperature sensor and packaging process thereof
The technical field is as follows:
the invention relates to a temperature sensor, in particular to a fiber grating temperature sensor.
Background art:
with rapid development of aviation technology, the transformable wing can be applied to certain types of airplanes, but no report about a temperature detection method of a wing surface of the transformable wing exists at present. Meanwhile, the variable wing mostly works in the environment of low temperature, strong electric field and strong magnetic field, and has strong electromagnetic interference. The fiber grating is a sensitive and passive device of optical fiber, has the advantages of strong electromagnetic interference resistance, corrosion resistance, light weight, no connection loss and the like, and is increasingly applied to various fields in engineering. The optical fiber Bragg grating is fine and has poor shearing resistance and is easy to break, and if the optical fiber Bragg grating is directly used as a sensing element, the optical fiber Bragg grating cannot be applied to actual engineering, so that a reasonable packaging process is the key point of the optical fiber Bragg grating in the application of aeronautical engineering, the optical fiber Bragg grating must be packaged to protect the optical fiber Bragg grating, the sensing characteristic of the optical fiber Bragg grating is improved, and the optical fiber Bragg grating can accurately, real-timely and reliably measure the temperature of a corresponding part in a system. The reasonable material is used as a substrate to carry out sensitization through belt action, and the requirement of the temperature detection range of the wing surface of the variable wing, particularly the low temperature of minus 60 ℃ to 0 ℃, is met. However, no specific method and report for solving the problems exist in China at present.
The invention content is as follows:
the technical problem to be solved by the invention is as follows: overcome prior art's not enough, provide one kind and improve on the basis of sensitization encapsulation, increase slot and aluminium foil to change the mode of paining of epoxy glue solution, thereby change the encapsulation mode, can give fiber grating with the temperature rapidly, the heat dissipation is also fast in the time of the cooling, simultaneously, increases the fiber grating temperature sensor of thermal expansion effect to FBG's influence, the characteristics of improvement temperature sensitivity.
The technical scheme of the invention is as follows: the utility model provides a fiber grating temperature sensor, includes aluminum plate, aluminium foil and fiber grating, characterized by: the fiber grating is embedded in the groove on the aluminum plate, the two ends of the fiber grating are fixed by structural adhesive, and the aluminum foil covers the aluminum plate and seals the groove and the fiber grating.
Furthermore, epoxy resin glue is uniformly coated on the aluminum plate and the fiber grating.
Furthermore, the aluminum plate and the aluminum foil are bonded by acrylic acid glue.
A packaging process of a fiber grating temperature sensor comprises the following steps: step one, processing a thin groove on an aluminum plate;
placing the fiber grating into a thin groove formed in an aluminum plate, fixing the optical fiber by structural adhesive at two ends of the thin groove, and enabling the fiber grating to be in a loose state;
step three, uniformly coating 0.25ml of epoxy resin glue solution on an aluminum plate and a fiber grating, placing the whole test piece into a thermostat for heat preservation after packaging, recovering to the room temperature, and repeating for three times;
step four, testing the grating wavelength change condition through a Si425 fiber grating demodulator;
and step five, covering the aluminum foil on an aluminum plate and sealing the groove and the fiber bragg grating.
Further, in the first step, the size of the aluminum plate is as follows: 450mm in length, 40mm in width and 4mm in height; the dimensions of the fine groove are: 5mm wide, 1mm deep and 30mm long.
Further, in the third step, before the epoxy resin glue solution is coated, the epoxy resin glue solution is vacuumized by using a vacuum valve, so that bubbles generated in the epoxy resin glue solution are eliminated.
Further, in the third step, the heat preservation process is as follows: the mixture was heated to 60 ℃ for 30min using a DH410 ET incubator.
Further, in the fifth step, the dimensions of the aluminum foil are as follows: the length is 40mm, the width is 40mm, and the thickness is 0.2 mm; the connection mode of the aluminum plate and the aluminum foil is as follows: and (3) polishing the surface of the aluminum plate to be rough by using fine sand paper, treating and cleaning the surface by using a reagent, and finally, uniformly sticking the aluminum plate and the aluminum foil together by using acrylic acid glue.
The invention has the beneficial effects that:
1. the invention improves the sensitization packaging, increases the grooves and the aluminum foil, and changes the coating mode of the epoxy resin glue solution, thereby changing the packaging mode, rapidly transmitting the temperature to the fiber grating, rapidly dissipating the heat when cooling, simultaneously increasing the influence of the thermal expansion effect on the FBG and improving the temperature sensitivity.
2. For the packaged temperature sensing device, the thermo-optic coefficient of the optical fiber material is not changed, but the FBG and the heat conducting paste are packaged in the fine groove of the aluminum sheet, the two ends of the FBG are fixed, the thermal expansion coefficient of the aluminum sheet is far larger than that of the FBG, when the temperature rises, the aluminum sheet expands to quickly transfer the temperature to the FBG, and simultaneously, tensile stress is generated on the FBG, so that the grating period changes, and when the temperature falls, the heat dissipation is also quick due to the good thermal conductivity of the aluminum sheet. Therefore, the aluminum foil sheet is packaged under the same temperature change, so that the temperature transfer is accelerated, the variation of the Bragg wavelength is increased, and the temperature sensitization effect is realized.
3. In order to increase the bonding strength of the aluminum plate and the aluminum foil, the surface of the aluminum plate is polished to be rough by using fine abrasive paper, the surface is treated and cleaned by using a reagent before bonding, and the aluminum plate and the aluminum foil are uniformly bonded together by using acrylic acid glue.
4. The temperature sensitization sensing device has small size, simple and easy operation of the packaging method and large measurement range, and meets the wing body fusion requirement, so the temperature sensitization sensing device is used for measuring the surface environment temperature of the variable wing body, particularly the low-temperature environment, and has good application prospect.
Description of the drawings:
fig. 1 is a schematic structural diagram of a fiber grating temperature sensor.
FIG. 2 is a flow chart of a packaging process of the fiber grating temperature sensor.
FIG. 3 is a schematic diagram of a temperature sensitization test system.
FIG. 4 is a graph of center wavelength of fiber grating before and after packaging and temperature.
FIG. 5 is the relationship between the center wavelength of the FBG sensitized packaged sensor and the temperature.
Fig. 6 is a calibration diagram of the temperature sensor No. 1.
Fig. 7 is a calibration diagram of the temperature sensor No. 2.
Fig. 8 is a calibration diagram of the temperature sensor No. 3.
The specific implementation mode is as follows:
example (b): see fig. 1, 2, 3, 4, 5, 6, 7 and 8. In the figure, 1-aluminum plate, 2-aluminum foil, 3-fiber grating, 4-groove, 5-temperature sensing device, 6-digital temperature control box, 7-fiber grating demodulator.
The fiber grating temperature sensor comprises an aluminum plate, an aluminum foil and a fiber grating, wherein the fiber grating is embedded in a groove on the aluminum plate, two ends of the fiber grating are fixed by structural adhesive, and the aluminum foil covers the aluminum plate and seals the groove and the fiber grating; epoxy resin glue solution is uniformly coated on the aluminum plate and the fiber bragg grating; the aluminum plate and the aluminum foil are bonded by acrylic acid glue; improve on the basis of sensitization encapsulation, increase slot and aluminium foil to change the mode of paining of epoxy glue solution, thereby change the encapsulation mode, can give fiber grating with the temperature rapidly, the heat dissipation is also fast in the cooling, simultaneously, increases thermal expansion effect and to FBG's influence, improves temperature sensitivity.
The present application will be described in detail below with reference to examples and the accompanying drawings.
The fiber grating 3 is embedded in the groove 4 on the aluminum plate 1, the two ends of the fiber grating 3 are fixed by structural adhesive, and the aluminum foil 2 covers the aluminum plate 1 and seals the groove 4 and the fiber grating 3.
The aluminum plate 1 and the fiber grating 3 are uniformly coated with epoxy resin glue. The aluminum plate 1 and the aluminum foil 2 are bonded by acrylic acid glue.
This kind of packaging structure does not make the thermo-optic coefficient of fiber material change, but FBG and heat conduction cream encapsulation in the thin in a wretched state of aluminum sheet to both ends are fixed, and the coefficient of thermal expansion of aluminum sheet is again far greater than FBG's coefficient of thermal expansion, and when the temperature rose, the aluminum sheet inflation was given FBG with the temperature transfer rapidly, produced tensile stress to it simultaneously, made the grating cycle change, made the heat dissipation also fast because of the good heat conductivity of aluminum sheet when the temperature rose. Therefore, the aluminum foil sheet is packaged under the same temperature change, so that the temperature transfer is accelerated, the variation of the Bragg wavelength is increased, and the temperature sensitization effect is realized.
The specific packaging process comprises the following steps: step one, processing a thin groove on an aluminum plate;
the size of the aluminum plate is as follows: 450mm in length, 40mm in width and 4mm in height; the dimensions of the fine groove are: 5mm wide, 1mm deep and 30mm long.
Placing the fiber grating into a thin groove formed in an aluminum plate, fixing the optical fiber by structural adhesive at two ends of the thin groove, and enabling the fiber grating to be in a loose state;
and step three, uniformly coating 0.25ml of epoxy resin glue solution on an aluminum plate and the fiber bragg grating, placing the whole test piece into a thermostat after packaging, keeping the temperature, recovering to the room temperature, and repeating for three times.
Before coating the epoxy resin glue solution, the epoxy resin glue solution is vacuumized by a vacuum valve to eliminate bubbles generated in the epoxy resin glue solution.
The heat preservation process comprises the following steps: the mixture was heated to 60 ℃ for 30min using a DH410 ET incubator.
And step four, testing the grating wavelength change condition through a Si425 fiber grating demodulator.
And step five, covering the aluminum foil on an aluminum plate and sealing the groove and the fiber bragg grating.
The dimensions of the aluminum foil are: the length is 40mm, the width is 40mm, and the thickness is 0.2 mm; the connection mode of the aluminum plate and the aluminum foil is as follows: and (3) polishing the surface of the aluminum plate to be rough by using fine sand paper, treating and cleaning the surface by using a reagent, and finally, uniformly sticking the aluminum plate and the aluminum foil together by using acrylic acid glue.
As shown in fig. 3, the testing apparatus is configured to place the packaged and cured temperature sensing device 5 in the DH410 ET digital temperature control box 6, access the device to the SI425 fiber grating demodulator 7 through an optical fiber jumper, directly read the wavelength of the fiber grating reflected wave through the SI425 fiber grating demodulator, and directly read the temperature value through the DH410 ET.
In the experiment, the temperature of the temperature control box is controlled by taking the temperature of minus 60 ℃ as a starting point and controlling the temperature of the temperature control box to gradually rise, wherein the temperature of the temperature control box is kept for 8-10min every time the temperature rises by 5 ℃ so as to ensure that the temperature of the FBG sensor is fully heated, and the purpose is to reduce errors brought by the experiment. And after the parameters are stabilized, reading the temperature and the wavelength of the reflected wave of the corresponding FBG sensor from a DH410 ET digital temperature control box and an SI425 fiber grating demodulator respectively. A tabulation of lines was run from the data of fig. 4, with a pre-package fit curve of Y =0.011X +1539.325, and a theoretical device temperature sensitivity of Y = 0.029029X +1538.9648 temperature sensitivity of 29.03 pm/deg.c, and a linear fit correlation coefficient of 0.9999 and 0.9993, respectively.
FIG. 5 shows that the device has no defects of aging, cracks, FBG separation from a substrate material and the like in a temperature detection range, particularly at the temperature of minus 60 ℃ to 0 ℃ in a low-temperature environment, and the temperature-sensitizing sensing device packaged by the aluminum plate has good temperature stability and repeatability and good binding property with the fiber bragg grating.
The temperature sensitization sensing device obtained through experiments has good sensitization effect, the sensitization multiple is 2.636 times, the error between the sensitization multiple and the theoretical sensitization multiple 2.540 is only 3.78%, and the two are basically consistent. The main reason for the error is caused by 0.25ml of epoxy resin adhesive connected with the grid point, meanwhile, the central wavelength drift and the temperature change show good linear relation, the linear fitting degree reaches 0.9993, and the sensor shows good repeatability.
In the experiment, 3 temperature sensors are manufactured according to the conclusion, the manufactured temperature sensors are placed in an oven to measure the relation between the central wavelength and the temperature, and the calibration result is shown in the table 1, and fig. 6, 7 and 8.
TABLE 1 Experimental data
Temperature/. degree.C
|
Sensor number 1 (nm)
|
Sensor number 2 (nm)
|
Sensor No. 3 (nm)
|
5
|
1550.196
|
1551.063
|
1537.832
|
10
|
1550.244
|
1551.11
|
1537.88
|
15
|
1550.294
|
1551.16
|
1537.927
|
20
|
1550.341
|
1551.209
|
1537.973
|
25
|
1550.392
|
1551.263
|
1538.02
|
30
|
1550.444
|
1551.324
|
1538.069
|
35
|
1550.498
|
1551.379
|
1538.118
|
40
|
1550.552
|
1551.434
|
1538.167
|
45
|
1550.608
|
1551.486
|
1538.218
|
50
|
1550.666
|
1551.538
|
1538.267
|
55
|
1550.733
|
1551.591
|
1538.32
|
60
|
1550.815
|
1551.644
|
1538.37
|
65
|
1550.922
|
1551.698
|
1538.422
|
70
|
1551.023
|
1551.752
|
1538.475
|
75
|
1551.117
|
1551.806
|
1538.528 |
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications, equivalent variations and modifications made to the above embodiment according to the technical spirit of the present invention still fall within the scope of the technical solution of the present invention.