CN112945127B - Fiber bragg grating strain type rebar meter metering calibration device and method - Google Patents
Fiber bragg grating strain type rebar meter metering calibration device and method Download PDFInfo
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- 239000000835 fiber Substances 0.000 title claims abstract description 311
- 238000000034 method Methods 0.000 title claims abstract description 83
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 148
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 79
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 74
- 238000005259 measurement Methods 0.000 claims abstract description 46
- 230000003014 reinforcing effect Effects 0.000 claims abstract description 13
- 230000007613 environmental effect Effects 0.000 claims abstract description 11
- 230000008569 process Effects 0.000 claims description 34
- 229910000831 Steel Inorganic materials 0.000 claims description 24
- 239000010959 steel Substances 0.000 claims description 24
- 230000008859 change Effects 0.000 claims description 18
- 238000009529 body temperature measurement Methods 0.000 claims description 17
- 229910001294 Reinforcing steel Inorganic materials 0.000 claims description 12
- 230000000087 stabilizing effect Effects 0.000 claims description 12
- 230000035945 sensitivity Effects 0.000 claims description 8
- 230000001105 regulatory effect Effects 0.000 claims description 6
- 238000011946 reduction process Methods 0.000 claims 1
- 230000002787 reinforcement Effects 0.000 abstract description 15
- 238000012937 correction Methods 0.000 abstract description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 238000011056 performance test Methods 0.000 abstract description 2
- 230000000694 effects Effects 0.000 abstract 1
- 239000000463 material Substances 0.000 description 6
- 238000012544 monitoring process Methods 0.000 description 6
- 238000012360 testing method Methods 0.000 description 5
- 230000001419 dependent effect Effects 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000035882 stress Effects 0.000 description 3
- 238000004154 testing of material Methods 0.000 description 3
- 229910000589 SAE 304 stainless steel Inorganic materials 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
- G01B11/165—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by means of a grating deformed by the object
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
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Abstract
A metering and calibrating device and a method for a fiber bragg grating strain type rebar meter. The device comprises a fiber bragg grating strain type reinforcing bar meter, a constant temperature water tank, a platinum resistance thermometer clamping device, a fiber bragg grating demodulator, a digital multimeter, a standard load device and an upper computer; the invention has the following effects: aiming at the current situation that no special fiber grating strain type reinforcement meter metering technical specification exists in China at present, the invention provides the fiber grating strain type reinforcement meter metering calibration device and method, solves the problem that the influence of the environmental temperature on the measurement precision of the fiber grating strain type reinforcement meter, provides technical basis for the performance test of the fiber grating strain type reinforcement meter before delivery of an instrument production unit, provides an effective method for the field data correction of an application unit, and improves the measurement precision and the data reliability of the fiber grating strain type reinforcement meter.
Description
Technical Field
The invention belongs to the technical field of traffic water transportation and highway engineering structure monitoring equipment metering calibration, and particularly relates to a metering calibration device and method for a fiber grating strain type rebar meter.
Background
In the fields of traffic water transportation and highway engineering, infrastructures and structures such as bridges and dams are affected by the external environment, the characteristics of the materials of the infrastructures and the structures, structural design and other factors in the construction and long-term use processes, damage accumulation and resistance attenuation are inevitably generated, the service life of the infrastructures and the structures is reduced, and if the existing potential safety hazards are not checked in time, catastrophic accidents are caused, and serious casualties and economic losses are caused, so that the health monitoring of important structures and infrastructures becomes a research hot spot of water transportation and highway engineering. The steel bar is one of the main bearing members of modern water transportation and highway engineering structures, is easily damaged due to the influence of environmental corrosion, fatigue, material aging and other factors, strain and stress serve as one of important parameters of reaction materials and structural mechanical properties, strength reserve information of the members can be obtained from strain distribution conditions in the materials and the structures, and the stress concentration at the local positions of the members and the actual load conditions of the members are determined, so that the steel bar has great monitoring significance.
At present, a relatively common monitoring means is to rigidly connect a measuring sensor with a reinforcing steel bar into a whole in a cementing or fixing clamp mode, when the reinforcing steel bar is axially or radially stretched or torqued, the measuring sensor generates the same change with the reinforcing steel bar, and the generated strain quantity is converted into light and an electric signal and is transmitted to an analysis instrument so as to realize dynamic and long-term monitoring of the mechanical property of the reinforcing steel bar. The reinforcing bar meter developed based on the mode in the market mainly comprises a vibrating wire type reinforcing bar meter, a resistance strain type reinforcing bar meter, a fiber grating strain type reinforcing bar meter and the like, wherein the fiber grating strain type reinforcing bar meter has the advantages of small insertion loss, good reliability and stability, easiness in forming a sensor network and the like, and plays an important role in monitoring the stress of structures such as roads, water-borne roads, dams, bridges and the like.
In the aspect of metering and calibrating the fiber bragg grating strain type rebar meter, a 1-level universal material testing machine is used as a standard in the standard of the power industry (DL/T1736-2017) for metering and calibrating the fiber bragg grating type rebar meter, the mechanical characteristics (nonlinearity, hysteresis, repeatability and comprehensive errors) of the fiber bragg grating type rebar meter are regulated by taking the 1-level universal material testing machine as the standard, on one hand, the wavelength range of the fiber bragg grating type rebar meter is usually (1510-1590) nm, the measuring range can reach 1500 mu epsilon, the measuring precision can reach 1 mu epsilon, the 1-level universal material testing machine is used as the standard, the measuring precision can not meet the metering and calibrating requirement of the fiber bragg grating type rebar meter, and in the calibrating process, the environmental temperature requirement (20+/-2 ℃) is only regulated, and the influence of temperature change on the calibrating precision is not considered. The building industry standard fiber bragg grating strain sensor (JG/T42-2013) uses a strain sensor calibration frame as a standard to prescribe the comprehensive error, resolution, repeatability and other mechanical characteristics of the fiber bragg grating strain sensor, and the strain sensor calibration frame cannot meet the clamping and calibration requirements of the fiber bragg grating strain type rebar meter in a measurement range and a measurement mode, so that the calibration method in the standard is high in accuracy, but cannot be applied to the fiber bragg grating strain type rebar meter, the environmental test temperature is regulated to be 20-25 ℃, and the influence of temperature change on a calibration result is not considered. The measuring performance indexes such as nonlinearity, non-repeatability, hysteresis, comprehensive error and full-scale output of the fiber grating strain type rebar meter are tested according to GB/T13606-2007 general technical Condition of vibration string type sensor of geotechnical engineering instruments by Chen Xingang and the like of quality supervision test centers of hydrologic instruments and geotechnical engineering instruments of water conservancy department, but because the two have great differences in working principle, the measuring method of the vibration string type rebar meter cannot fully embody all measuring performances of the fiber grating strain type rebar meter, cannot effectively control quality of manufacturers of instruments, and cannot guarantee quality of products delivered from factories and safety of instruments using engineering.
Therefore, the metering calibration device and the metering calibration method for the fiber bragg grating strain type reinforcement meter are researched to realize high-precision calibration of the mechanical performance of the fiber bragg grating strain type reinforcement meter, effectively reduce the influence of environmental temperature change on a calibration result, and have great significance for improving the product quality of the fiber bragg grating strain type reinforcement meter.
Disclosure of Invention
In order to solve the problems, the invention aims to provide a fiber bragg grating strain type rebar meter metering calibration device.
In order to achieve the purpose, the metering and calibrating device of the fiber bragg grating strain type rebar meter comprises a fiber bragg grating strain type rebar meter, a constant temperature water tank, a platinum resistance thermometer clamping device, a fiber bragg grating demodulator, a digital multimeter, a standard load device and an upper computer; the fiber bragg grating strain type rebar meter is vertically placed in the constant-temperature water tank during temperature calibration; the platinum resistance thermometer is vertically placed in the constant temperature water tank through a platinum resistance thermometer clamping device; the fiber bragg grating demodulator is simultaneously and electrically connected with the fiber bragg grating strain type rebar meter and the upper computer; the platinum resistance thermometer is electrically connected with the digital multimeter; the fiber bragg grating strain type reinforcing steel bar meter is fixed on a standard load device during mechanical property calibration, and the standard load device is electrically connected with an upper computer.
The fiber bragg grating strain type rebar meter comprises a rebar, a fiber bragg grating strain type sensor and a fiber bragg grating temperature sensor; the fiber grating strain sensor and the fiber grating temperature sensor are fixed at the outer part of the steel bar, the axial direction of the fixed part of the fiber grating strain sensor and the fiber grating temperature sensor is parallel to the axial direction of the steel bar, and the two ends of the fiber grating strain sensor and the fiber grating temperature sensor are connected to the fiber grating demodulator.
The steel bars are made of deformed steel bars or round steel bars, and the section diameters are 12mm, 14mm, 16mm, 18mm or 22mm.
In the constant temperature water tank, the fiber bragg grating strain sensor, the fiber bragg grating temperature sensor and the measuring point of the platinum resistance thermometer are arranged at equal heights.
The platinum resistance thermometer adopts a four-wire system equal-level or equal-level standard platinum resistance thermometer.
The metering calibration method adopting the fiber bragg grating strain type rebar meter metering calibration device comprises the following steps in sequence:
Step 001: vertically placing the fiber bragg grating strain type rebar meter in a constant-temperature water tank; the upper end of a platinum resistance thermometer is fixed on a platinum resistance thermometer clamping device, the lower part of the platinum resistance thermometer clamping device is placed in a constant temperature water tank, the measuring point of the platinum resistance thermometer is arranged at the same height as the measuring point of a fiber bragg grating strain sensor and a fiber bragg grating temperature sensor in a fiber bragg grating strain type steel bar meter, the fiber bragg grating strain type steel bar meter is connected to an upper computer through a fiber bragg grating demodulator, the platinum resistance thermometer is connected with a digital multimeter, the digital multimeter is adjusted to a resistance level, the temperature is started and preheated for 30min, and serial ports of the upper computer are initialized;
Step 002: the water temperature in the constant-temperature water tank is regulated to 0 ℃, after the water temperature is stabilized for 30 minutes, the temperature value of the constant-temperature water tank, which is measured by a platinum resistance thermometer and is displayed by a digital multimeter, at the same height as the fiber bragg grating strain type sensor is read, and the central wavelength value measured by the fiber bragg grating strain type sensor in the fiber bragg grating strain type rebar meter and the temperature value measured by the fiber bragg grating temperature type sensor are respectively read from an upper computer;
Then taking each 10 ℃ as a primary temperature measuring point, gradually increasing the water temperature in the constant-temperature water tank to 60 ℃, stabilizing for 30 minutes at each stage of temperature measuring points, and sequentially recording the measuring data of the platinum resistance thermometer, the fiber bragg grating strain sensor and the fiber bragg grating temperature sensor according to the mode;
Then, from 60 ℃, taking each 10 ℃ as a primary temperature measuring point, gradually reducing the water temperature in the constant-temperature water tank to 0 ℃, stabilizing for 30 minutes at each stage of temperature measuring points, and sequentially recording the measuring data of the platinum resistance thermometer, the fiber bragg grating strain sensor and the fiber bragg grating temperature sensor according to the mode;
The method comprises the steps of taking average values of corresponding measured data of a platinum resistance thermometer, a fiber bragg grating strain type sensor and a fiber bragg grating temperature type sensor at each level of temperature measuring points in the heating and cooling processes and respectively serving as respective final measured values, recording a temperature value measured by the fiber bragg grating temperature type sensor at 0 ℃ as an initial temperature value T F0, and recording a central wavelength value measured by the fiber bragg grating strain type sensor at 0 ℃ as an initial central wavelength value lambda T0;
Step 003: taking out the fiber grating strain type rebar meter from a constant temperature water tank, fixing the upper end and the lower end of the rebar on a standard load device, preloading the fiber grating strain type rebar meter in the range of the fiber grating strain type rebar meter, recovering the fiber grating strain type rebar meter to a zero load state and stabilizing, and reading a central wavelength value measured by a fiber grating strain type sensor demodulated by a fiber grating demodulator from an upper computer to serve as an initial wavelength value lambda 0 of the fiber grating strain type rebar meter;
The preloading method comprises the steps of taking 10% of full range as a primary load measuring point in the range of the fiber grating strain type rebar meter, gradually loading to a full range load value, stabilizing each stage for at least 3min, recording a standard load value applied by a standard load device and a central wavelength value measured by a fiber grating strain type rebar meter corresponding to the fiber grating strain type rebar meter, synchronously recording an ambient temperature value T s near the fiber grating strain type rebar meter measured by a fiber grating temperature type rebar meter corresponding to the load measuring point, gradually reducing the load from the full range load value to a zero load state according to the method, recording each measured value, and circularly measuring for 3 times;
Step 004: taking a temperature value T Ri (i=0, 1,2,3,4,5, 6) of each stage of temperature measurement points in a constant-temperature water tank measured by a platinum resistance thermometer as an independent variable, and taking a temperature value T Fi (i=0, 1,2,3,4,5, 6) of each stage of temperature measurement points in the constant-temperature water tank measured by a fiber grating temperature sensor as a dependent variable, and performing least square straight line fitting according to a formula (1), thereby establishing a corresponding relation between the platinum resistance thermometer and the temperature values measured by the fiber grating temperature sensor so as to realize the temperature value calibration measured by the fiber grating temperature sensor:
TFWi＝kT×TRi+bR (1)
In the method, in the process of the invention,
T FWi -T Fi corresponding to T Ri on least squares line, i=0, 1,2,3,4,5,6
K T —temperature sensitivity coefficient;
b R -measuring the temperature value measured when the temperature value in the constant-temperature water tank is 0 ℃ by the fiber bragg grating temperature sensor on the least square straight line by a platinum resistance thermometer;
Step 005: the method comprises the steps of taking the variation delta T Fi(ΔTFi＝TFi-TF0, i=0, 1,2,3,4,5, 6) of a temperature value of each stage of temperature measuring points in a constant-temperature water tank measured by a fiber bragg grating temperature sensor after being calibrated by a platinum resistance thermometer relative to an initial temperature value T F0 as an independent variable, and taking the variation delta lambda Ti(ΔλTi＝λTi-λT0, i=0, 1,2,3,4,5, 6) of a central wavelength value lambda Ti of each stage of temperature measuring points, such as the fiber bragg grating temperature sensor, in the constant-temperature water tank measured by the fiber bragg grating strain sensor relative to the initial central wavelength value lambda T0, wherein lambda Ti is the central wavelength value of each stage of temperature measuring points, such as the fiber bragg grating temperature sensor, in the constant-temperature water tank measured by the fiber bragg grating strain sensor, as a minimum square straight line fitting is carried out according to a formula (2), so that the corresponding relation between the temperature calibration value of the fiber bragg grating temperature sensor and the central wavelength value measured by the fiber bragg grating strain sensor is established;
ΔλTi＝kλ×ΔTFi+bF (2)
In the method, in the process of the invention,
Δλ TWi —Δλ Ti (i=0, 1,2,3,4,5, 6) corresponding to Δt Fi on the least squares straight line, nm;
k λ —strain sensitivity coefficient;
b F -the central wavelength variation of the fiber bragg grating strain sensor on the least square straight line when the temperature value in the constant temperature water tank is 0 ℃ is measured by a platinum resistance thermometer, and nm.
Step 006: substituting an ambient temperature value T Fij (i=1, 2, … …,10, j=1, 2,3, … …, 6) recorded by the fiber bragg grating temperature sensor in step 005 into formula (2), and calculating a central wavelength change delta lambda Tij (i=1, 2, … …,10, j=1, 2,3, … …, 6) of the fiber bragg grating strain sensor due to ambient temperature change at each stage of load measurement points;
Calculating the average value of the difference value between the central wavelength value lambda ij and the initial wavelength value lambda 0 measured by the fiber bragg grating strain sensor in the 3-time cyclic measurement process of each load measurement point according to the formula (3):
In the method, in the process of the invention,
Δλ i —the average value of the difference between the central wavelength value and the initial wavelength value measured by the fiber bragg grating strain sensor on the fiber bragg grating strain rebar meter in the 3-cycle measurement process of the i-th stage load measurement point (i=1, 2,3, … …, 10), nm;
Lambda ij -the central wavelength value measured by a fiber bragg grating strain sensor on a fiber bragg grating strain type rebar meter in the j-th (j=1, 2,3, … …, m) measurement process of the i-th level load measuring point (i=1, 2,3, … …, 10);
Δλ Tij —the amount of change in center wavelength (i=1, 2, … …,10, j=1, 2,3, … …, 6) measured by a fiber bragg grating strain sensor due to a change in ambient temperature, nm;
m—number of times of measurement of loading and unloading strokes, m=6.
Taking an average value delta lambda i of the difference value between the central wavelength value and the initial wavelength value measured by a fiber grating strain sensor on the fiber grating strain type reinforcement meter as an independent variable, taking a load average value F i applied by a standard load device as an independent variable, and carrying out least square method linear fitting according to a formula (5) to obtain a load measurement value F Wi of the fiber grating type reinforcement meter:
wherein,
In the method, in the process of the invention,
F Pi, standard load applied by each stage of load measuring points in the loading stroke of the standard load device, and kN;
F Mi, standard load applied by each stage of load measuring points in the load reducing stroke of the standard load device, and kN;
FWi＝k×Δλi+C (5)
Wherein:
F Wi —f i (i=0, 1,2,3,4,5, 6) corresponding to Δλ i on the least square straight line, nmk —the sensitivity coefficient of the fiber bragg grating strain gauge, kN/nm;
and C, measuring the load of the fiber bragg grating strain type steel bar meter in a free state, and kN.
Step 007: and (3) calculating the maximum error delta L between the load measured value F Wi of the fiber bragg grating strain type reinforcing steel bar gauge and the load average value F i applied by the standard load device according to the formula (6).
In the method, in the process of the invention,
F FS -full scale load value, kN, of the fiber bragg grating strain gauge 10.
The invention has the beneficial effects that: aiming at the current situation that no special fiber grating strain type reinforcement meter metering technical specification exists in China at present, the invention provides the fiber grating strain type reinforcement meter metering calibration device and method, solves the problem that the influence of the environmental temperature on the measurement precision of the fiber grating strain type reinforcement meter, provides technical basis for the performance test of the fiber grating strain type reinforcement meter before delivery of an instrument production unit, provides an effective method for the field data correction of an application unit, and improves the measurement precision and the data reliability of the fiber grating strain type reinforcement meter.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
Fig. 1 is a diagram of a structure of a fiber grating strain type rebar meter metering calibration device provided by the invention.
Fig. 2 is a flow chart of a method for calibrating the metering of the fiber bragg grating strain type rebar meter.
Fig. 3 is a diagram of the structure of the fiber grating strain type rebar meter in the fiber grating strain type rebar meter metering calibration device.
Fig. 4 is a graph of a least square method straight line fitting result of a temperature measurement point corresponding to a fiber grating temperature sensor and a platinum resistance thermometer.
Fig. 5 is a graph of a result of least square line fitting of a temperature correction value between a central wavelength value of a fiber grating strain sensor and a temperature measurement point corresponding to the fiber grating temperature sensor.
Fig. 6 is a graph of a result of linear fitting of a standard load value output by the standard load device and a central wavelength variation measured by a corresponding load measuring point of the fiber grating strain type rebar meter.
Detailed Description
The fiber bragg grating strain type rebar meter metering calibration device and method provided by the invention are described in detail below with reference to the accompanying drawings and specific embodiments.
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
As shown in fig. 1, the fiber bragg grating strain type rebar meter metering and calibrating device provided by the invention comprises a fiber bragg grating strain type rebar meter 10, a constant temperature water tank 20, a platinum resistance thermometer 30, a platinum resistance thermometer clamping device 40, a fiber bragg grating demodulator 50, a digital multimeter 60, a standard load device 70 and an upper computer 80; wherein, the fiber bragg grating strain type rebar meter 10 is vertically placed in the constant temperature water tank 20 during temperature calibration; the platinum resistance thermometer 30 is vertically placed in the constant temperature water tank 20 by the platinum resistance thermometer clamping device 40; the fiber bragg grating demodulator 50 is electrically connected with the fiber bragg grating strain type rebar meter 10 and the upper computer 80 at the same time; the platinum resistance thermometer 30 is electrically connected with the digital multimeter 60; the fiber bragg grating strain type rebar meter 10 is fixed on a standard load device 70 during mechanical characteristic calibration, and the standard load device 70 is electrically connected with an upper computer 80.
As shown in fig. 3, the fiber bragg grating strain gauge 10 includes a reinforcing bar 101, a fiber bragg grating strain sensor 102, and a fiber bragg grating temperature sensor 103; wherein, the steel bar 101 can be in the form of deformed steel bar, round steel and the like, the material can be 304 steel and the like, and the section diameter can be 12mm, 14mm, 16mm, 18mm, 22mm and other conventional dimensions; the middle parts of the fiber bragg grating strain sensor 102 and the fiber bragg grating temperature sensor 103 are fixed on the outer part of the steel bar 101, the axial direction of the fixed parts of the fiber bragg grating strain sensor 102 and the fiber bragg grating temperature sensor 103 is parallel to the axial direction of the steel bar 101, and two ends of the fiber bragg grating strain sensor are connected to the fiber bragg grating demodulator 50.
The temperature measurement range of the fiber grating temperature sensor 103 in the fiber grating strain type rebar meter 10 is (-30- +/-125) DEG C, and the temperature resolution is 0.1 ℃.
In the constant temperature water tank 20, the fiber bragg grating strain type sensor 102, the fiber bragg grating temperature type sensor 103 and the measuring point of the platinum resistance thermometer 30 in the fiber bragg grating strain type rebar meter 10 are placed at equal heights.
The temperature variation range of the constant temperature water tank 20 is (-5- +/-100) DEG C, the temperature fluctuation degree is +/-0.05 ℃ and the temperature uniformity is +/-0.05 ℃.
The platinum resistance thermometer 30 is a four-wire standard platinum resistance thermometer of one class or two class.
The strain measurement range of the fiber bragg grating strain type rebar meter metering calibration device is (-1500- +/-1500) mu epsilon, when the diameter of the selected rebar 101 is 16mm, the material is 304 steel, and the shape is round steel, the measurement uncertainty is U=0.74 kN, and k=2.
As shown in fig. 2, the method for measuring and calibrating the fiber bragg grating strain type rebar meter by adopting the device comprises the following steps in sequence:
step 001: device connection initialization:
placing the fiber bragg grating strain type rebar meter 10 vertically in a constant temperature water tank 20; the upper end of a platinum resistance thermometer 30 is fixed on a platinum resistance thermometer clamping device 40, the lower part of the platinum resistance thermometer is arranged in a constant temperature water tank 20, the measuring points of the platinum resistance thermometer 30 and the measuring points of a fiber bragg grating strain type sensor 102 and a fiber bragg grating temperature type sensor 103 in a fiber bragg grating strain type rebar meter 10 are arranged at the same height, the fiber bragg grating strain type rebar meter 10 is connected to an upper computer 80 through a fiber bragg grating demodulator 50, the platinum resistance thermometer 30 is connected with a digital multimeter 60, the digital multimeter 60 is adjusted to a resistance gear, the machine is started and preheated for 30min, and the serial port of the upper computer 80 is initialized;
step 002, temperature calibration:
After the water temperature in the constant-temperature water tank 20 is regulated to 0 ℃ and is stabilized for 30 minutes, reading the temperature value of the same height as the fiber grating strain type sensor 102 in the constant-temperature water tank 20 measured by the platinum resistance thermometer 30 shown in the digital multimeter 60, and respectively reading the central wavelength value measured by the fiber grating strain type sensor 102 and the temperature value measured by the fiber grating temperature type sensor 103 in the fiber grating strain type rebar meter 10 from the upper computer 80;
then, taking each 10 ℃ as a primary temperature measuring point, gradually increasing the water temperature in the constant-temperature water tank 20 to 60 ℃, and sequentially recording the measurement data of the platinum resistance thermometer 30, the fiber bragg grating strain type sensor 102 and the fiber bragg grating temperature type sensor 103 in the manner after stabilizing for 30 minutes at each stage of temperature measuring points;
then, from 60 ℃, taking each 10 ℃ as a primary temperature measuring point, gradually reducing the water temperature in the constant-temperature water tank 20 to 0 ℃, stabilizing for 30 minutes at each stage of temperature measuring points, and sequentially recording the measuring data of the platinum resistance thermometer 30, the fiber bragg grating strain sensor 102 and the fiber bragg grating temperature sensor 103 in the manner;
The corresponding measured data of the platinum resistance thermometer 30, the fiber bragg grating strain type sensor 102 and the fiber bragg grating temperature type sensor 103 at each level of temperature measuring points in the temperature increasing and reducing processes are averaged and respectively used as respective final measured values, the temperature value measured by the fiber bragg grating temperature type sensor 103 at 0 ℃ is recorded as an initial temperature value T F0, and the central wavelength value measured by the fiber bragg grating strain type sensor 102 at 0 ℃ is recorded as an initial central wavelength value lambda T0; .
Step 003, mechanical characteristic calibration:
Taking the fiber grating strain type rebar meter 10 out of the constant temperature water tank 20, fixing the upper end and the lower end of the rebar 101 on the standard load device 70, preloading the fiber grating strain type rebar meter 10 in the range of the fiber grating strain type rebar meter 10, recovering the fiber grating strain type rebar meter 10 to a zero load state and stabilizing, and reading a central wavelength value measured by the fiber grating strain type sensor 102 demodulated by the fiber grating demodulator 50 from the upper computer 80 to serve as an initial wavelength value lambda 0 of the fiber grating strain type rebar meter 10;
The preloading method comprises the steps of taking 10% of full range as a primary load measuring point in the range of the fiber grating strain type rebar meter 10, gradually loading to a full range load value, stabilizing each stage for at least 3min, recording a standard load value applied by a standard load device 70 and a central wavelength value measured by a fiber grating strain type rebar meter 102 on the corresponding fiber grating strain type rebar meter 10, synchronously recording an ambient temperature value T s near the fiber grating strain type rebar meter 10 measured by a fiber grating temperature sensor 103 when the corresponding load measuring point, gradually reducing the load from the full range load value to a zero load state according to the method, recording each measured value, and circularly measuring for 3 times;
step 004, establishing a corresponding relation between the platinum resistance thermometer 30 and the temperature value measured by the fiber bragg grating temperature sensor 103:
Taking the temperature value T Ri (i=0, 1,2,3,4,5, 6) of each stage of temperature measurement points in the constant temperature water tank 20 measured by the platinum resistance thermometer 30 as an independent variable, taking the temperature value T Fi (i=0, 1,2,3,4,5, 6) of each stage of temperature measurement points in the constant temperature water tank 20 measured by the fiber grating temperature sensor 103 as a dependent variable, and performing least square straight line fitting according to the formula (1), thereby establishing the corresponding relation between the platinum resistance thermometer 30 and the temperature values measured by the fiber grating temperature sensor 103 so as to realize the temperature value calibration measured by the fiber grating temperature sensor 103:
TFWi＝kT×TRi+bR (1)
In the method, in the process of the invention,
T FWi -T Fi corresponding to T Ri on least squares line, i=0, 1,2,3,4,5,6
K T —temperature sensitivity coefficient;
b R -the temperature value measured by the fiber grating temperature sensor 103 on the least square straight line when the temperature value in the constant temperature water tank 20 is 0 ℃ is measured by the platinum resistance thermometer 30;
step 005, establishing a corresponding relation between a temperature calibration value of the fiber grating temperature sensor 103 and a central wavelength value measured by the fiber grating strain sensor 102:
taking the variation delta T Fi(ΔTFi＝TFi-TF0, i=0, 1,2,3,4,5, 6) of the temperature value of each stage of temperature measurement point in the constant temperature water tank 20 measured by the fiber bragg grating temperature type sensor 103 after being calibrated by the platinum resistance thermometer 30 relative to the initial temperature value T F0 as an independent variable, and taking the variation delta lambda Ti(ΔλTi＝λTi-λT0, i=0, 1,2,3,4,5, 6) of the central wavelength value lambda Ti of each stage of temperature measurement point in the constant temperature water tank 20 measured by the fiber bragg grating strain type sensor 102 at the same height as the fiber bragg grating temperature type sensor 103 relative to the initial central wavelength value lambda T0 as a dependent variable, wherein lambda Ti is the central wavelength value of each stage of temperature measurement point in the constant temperature water tank 20 measured by the fiber bragg grating strain type sensor 102 at the same height as the fiber bragg grating temperature type sensor 103, and performing a least square straight line fitting according to formula (2), thereby establishing a corresponding relation between the temperature calibration value of the fiber bragg grating temperature calibration type sensor 103 and the central wavelength value measured by the fiber bragg grating strain type sensor 102;
ΔλTi＝kλ×ΔTFi+bF (2)
In the method, in the process of the invention,
Δλ TWi —Δλ Ti (i=0, 1,2,3,4,5, 6) corresponding to Δt Fi on the least squares straight line, nm;
k λ —strain sensitivity coefficient;
b F -least square linear fiber grating strain sensor 102 measures the central wavelength variation, nm, when the temperature value in the constant temperature water tank 20 is 0 ℃ by the platinum resistance thermometer 30.
Step 006, solving a load measurement value of the fiber bragg grating type rebar meter 10:
Substituting the environmental temperature value T Fij (i=1, 2, … …,10, j=1, 2,3, … …, 6) recorded by the fiber bragg grating temperature sensor 103 in step 005 into the formula (2), and calculating the central wavelength variation Δλ Tij (i=1, 2, … …,10, j=1, 2,3, … …, 6) of the fiber bragg grating strain sensor 102 due to environmental temperature variation at each stage of load measurement points;
Calculating the average value of the difference value between the central wavelength value lambda ij and the initial wavelength value lambda 0 measured by the fiber bragg grating strain sensor 102 in the 3-time cyclic measurement process of each load measurement point according to the formula (3):
In the method, in the process of the invention,
Δλ i —the average value of the difference between the central wavelength value and the initial wavelength value measured by the fiber bragg grating strain type sensor 102 on the fiber bragg grating strain type rebar meter 10 in the 3-cycle measurement process of the i-th stage load measurement point (i=1, 2,3, … …, 10), nm;
lambda ij -the central wavelength value measured by the fiber bragg grating strain sensor 102 on the fiber bragg grating strain type rebar meter 10 in the j-th (j=1, 2,3, … …, m) measurement process of the i-th level load measuring point (i=1, 2,3, … …, 10);
Δλ Tij —the amount of change in center wavelength (i=1, 2, … …,10, j=1, 2,3, … …, 6) measured by the fiber bragg grating strain sensor 102 due to the change in ambient temperature, nm;
m—number of times of measurement of loading and unloading strokes, m=6.
Taking the average value delta lambda i of the difference value between the central wavelength value and the initial wavelength value measured by the fiber bragg grating strain sensor 102 on the fiber bragg grating strain type reinforcing steel bar meter 10 as an independent variable, taking the average value F i of the load applied by the standard load device 70 as the dependent variable, performing least square method straight line fitting according to a formula (5), and calculating to obtain a load measurement value F Wi of the fiber bragg grating type reinforcing steel bar meter 10:
wherein,
In the method, in the process of the invention,
F Pi, standard load applied by each stage of load measuring points in the loading stroke of the standard load device 70, and kN;
F Mi, standard load applied by each stage of load measuring points in the load reducing stroke of the standard load device 70, and kN;
FWi＝k×Δλi+C (5)
Wherein:
F Wi —f i (i=0, 1,2,3,4,5, 6) corresponding to Δλ i on the least squares line, nm
K-sensitivity coefficient of fiber bragg grating strain gauge 10, kN/nm;
c-load measurement value in the free state of the fiber grating strain type reinforcing steel bar meter 10, kN.
Step 007, calculating the maximum error:
and calculating the maximum error delta L between the load measured value F Wi of the fiber bragg grating strain type rebar meter 10 and the load average value F i applied by the standard load device 70 according to the formula (6).
In the method, in the process of the invention,
F FS -full scale load value, kN, of the fiber bragg grating strain gauge 10.
When the device works, a 304-material round steel fiber bragg grating type rebar meter with the section diameter of 22mm is selected for verification, the range of the fiber bragg grating type rebar meter 10 is 0-40kN, firstly, temperature correction is carried out on the fiber bragg grating strain type rebar meter 10, a platinum resistance thermometer 30 is used as a measurement standard, the platinum resistance thermometer 30 and a fiber bragg grating temperature sensor 103 on the fiber bragg grating strain type rebar meter 10 are placed in the constant temperature water tank 20 at the same height, in the range of 0-60 ℃, each 10 ℃ is used as a primary temperature measuring point, heating and cooling tests are carried out, and measured data in the heating and cooling processes of each sensor at each temperature measuring point are averaged to obtain a final measured value, as shown in table 1.
Table 1 measurement data of each sensor in constant temperature water tank
The correspondence between the temperature value measured by the platinum resistance thermometer 30 and the temperature value at the same height as the platinum resistance thermometer 30 in the constant temperature water tank 30 measured by the fiber bragg grating temperature sensor 103 at the corresponding temperature measurement point is established according to the formula (1), and as shown in fig. 4, there is:
TFWi＝1.002×TRi+0.249 (7)
The values of T FWi thus obtained are shown in Table 2.
TABLE 2 temperature correction value of fiber bragg grating temperature sensor
| Sequence number | Fiber grating temperature sensor temperature measurement value (DEG C) | Temperature correction value (DEG C) of fiber bragg grating temperature type sensor |
| 1 | 0.289 | 0.284 |
| 2 | 10.261 | 10.293 |
| 3 | 20.334 | 20.296 |
| 4 | 30.325 | 30.292 |
| 5 | 40.346 | 40.308 |
| 6 | 50.331 | 50.301 |
| 7 | 60.332 | 60.311 |
The correspondence between the difference value of the temperature correction value at each temperature measurement point in the constant temperature water tank 30 and the temperature correction value at the initial temperature value of the fiber bragg grating temperature sensor 103 and the central wavelength variation value of the fiber bragg grating strain sensor 102 at the corresponding temperature measurement point is established according to the formula (2), and the central wavelength variation value is amplified 1000 times and then the least square method straight line fitting is performed, as shown in fig. 5, because the central wavelength variation is small:
ΔλTi＝0.631×ΔTFi-0.288 (8)
The fiber grating strain type rebar meter 10 is fixed on a standard load device 70, a 0.1-level microcomputer control superposition type force standard machine is selected, the measuring range is 0-100kN, the fiber grating strain type rebar meter 10 is loaded and unloaded step by step in the measuring range of 0-40kN according to the full range of 10% (F.S), and the measuring data are shown in table 3.
Table 3 central wavelength value in loading-unloading process of fiber grating strain type rebar meter
During the measurement, keeping the laboratory temperature within (21+ -2) deg.C, when the temperature reaches the upper limit of 22deg.C, it is obtained according to formula (8):
ΔλTi＝[0.631×(23-0)-0.288]/1000＝0.0142nm
Then when the temperature reaches the lower limit of 19 ℃, it is obtainable according to formula (8):
ΔλTi＝[0.631×(19-0)-0.288]/1000＝0.0117nm
When the temperature is maintained at 21 ℃, it is obtainable according to formula (8):
ΔλTi＝[0.631×(21-0)-0.288]/1000＝0.0130nm
In this example, for convenience of calculation, when the center wavelength change value at the upper limit of the temperature change at 23 ℃ is Δλ Tij, i.e., Δλ Tij =0.0142 nm, as measured at the upper limit and lower limit of the temperature change at 0 ℃ at the time of test λ 0, the result of calculating Δλ i according to formula (3) is shown in table 4, wherein λ 0 = 1584.785nm, and the result of calculating F i according to formula (4) is also shown in table 4.
TABLE 4 fiber bragg grating strain type rebar meter center wavelength variation value and standard load value during loading-unloading process
The corresponding relation between the standard load value F i and the central wavelength change value delta lambda i of the fiber bragg grating strain type rebar meter is calculated according to the formula (5), and as shown in fig. 6, the corresponding relation is as follows:
FWi＝16.123×Δλi+2.395 (9)
The temperature-compensated load values measured by the fiber grating strain gauge 10 for each stage of standard load value F i applied to the standard load device 70 are shown in table 5.
Table 5 standard and measured load values at each load measurement point
In table 5, when the load is 0kN, that is, the fiber bragg grating strain gauge 10 is in the free state, the fiber bragg grating strain gauge 10 does not return to the unstressed state after three preloading-unloading processes and forward and backward stroke test processes, and therefore the error is large when the load is 0kN, and the data can be removed when the load is calculated, and the method according to the formula (6) comprises:
In field application, the k and C values are generally provided for the usage units, if the steady compensation calibration is not performed according to the method provided by the invention, the fiber bragg grating strain type rebar meter 10 has a central wavelength variation delta lambda Tij =0.0142 nm caused by temperature change at 23 ℃, and the load measurement value of the fiber bragg grating strain type rebar meter 10 has an error of 16.123 ×0.0142=0.229 kN, so that the accuracy and the reliability of field measurement data are affected.
The above-described embodiments are only for illustrating the technical spirit and features of the present invention, and it is intended to enable those skilled in the art to understand the content of the present invention and to implement it accordingly, and the scope of the present invention is not limited to the embodiments, i.e. equivalent changes or modifications to the spirit of the present invention are still within the scope of the present invention.
Claims (4)
1. The utility model provides a fiber bragg grating strain type reinforcing bar meter measurement calibrating device which characterized in that: the fiber bragg grating strain type steel bar meter metering and calibrating device comprises a fiber bragg grating strain type steel bar meter (10), a constant temperature water tank (20), a platinum resistance thermometer (30), a platinum resistance thermometer clamping device (40), a fiber bragg grating demodulator (50), a digital multimeter (60), a standard load device (70) and an upper computer (80); wherein, the fiber bragg grating strain type rebar meter (10) is vertically placed in the constant temperature water tank (20) during temperature calibration; the platinum resistance thermometer (30) is vertically arranged in the constant temperature water tank (20) through the platinum resistance thermometer clamping device (40); the fiber bragg grating demodulator (50) is electrically connected with the fiber bragg grating strain type rebar meter (10) and the upper computer (80) at the same time; the platinum resistance thermometer (30) is electrically connected with the digital multimeter (60); the fiber bragg grating strain type reinforcing steel bar meter (10) is fixed on a standard load device (70) when the mechanical characteristics are calibrated, and the standard load device (70) is electrically connected with an upper computer (80);
The fiber bragg grating strain type rebar meter (10) comprises a rebar (101), a fiber bragg grating strain type sensor (102) and a fiber bragg grating temperature type sensor (103); the fiber bragg grating strain sensor (102) and the fiber bragg grating temperature sensor (103) are fixed at the outer part of the steel bar (101), the axial direction of the fixed part of the fiber bragg grating strain sensor (102) and the fiber bragg grating temperature sensor (103) is parallel to the axial direction of the steel bar (101), and two ends of the fiber bragg grating strain sensor are connected to the fiber bragg grating demodulator (50);
in the constant temperature water tank (20), the fiber grating strain sensor (102), the fiber grating temperature sensor (103) and the measuring points of the platinum resistance thermometer (30) are arranged at equal heights;
Taking the variation delta T Fi of the temperature value of each stage of temperature measuring points in the constant-temperature water tank (20) measured by the fiber grating temperature sensor (103) after the calibration of the platinum resistance thermometer (30) relative to the initial temperature value T F0 as an independent variable, wherein delta T Fi＝TFi-TF0, i=0, 1,2,3,4,5,6, and taking the variation delta lambda Ti of the central wavelength value lambda Ti of each stage of temperature measuring points in the constant-temperature water tank (20) measured by the fiber grating strain sensor (102) and the same height as the fiber grating temperature sensor (103) relative to the initial central wavelength value lambda T0, wherein delta lambda Ti＝λTi-λT0,i＝0,1,2,3,4,5,6,λTi is the central wavelength value of each stage of temperature measuring points in the constant-temperature water tank (20) measured by the fiber grating strain sensor (102) and the same height as the fiber grating temperature sensor (103), and performing least square straight line fitting according to a formula (2), thereby establishing the corresponding relation between the temperature calibration value of the fiber grating temperature sensor (103) and the central wavelength of the fiber grating strain sensor (102);
ΔλTWi＝kλ×ΔTFi+bF (2)
In the method, in the process of the invention,
Δλ TWi —Δλ Ti, nm, i=0, 1,2,3,4,5,6 on the least squares line corresponding to Δt Fi;
k λ —strain sensitivity coefficient;
b F -least square linear fiber grating strain sensor (102) is used for measuring the central wavelength variation, nm when the temperature value in the constant temperature water tank (20) is 0 ℃ by a platinum resistance thermometer (30).
2. The fiber bragg grating strain gauge rebar meter metering calibration device of claim 1, wherein: the steel bar (101) adopts screw steel or round steel, and the section diameter is 12mm, 14mm, 16mm, 18mm or 22mm.
3. The fiber bragg grating strain gauge rebar meter metering calibration device of claim 1, wherein: the platinum resistance thermometer (30) adopts a four-wire standard platinum resistance thermometer with equal or equal level.
4. A metering calibration method using the fiber bragg grating strain type rebar meter metering calibration device according to any one of claims 1 to 3, characterized in that: the metering calibration method comprises the following steps in sequence:
Step 001: the fiber bragg grating strain type rebar meter (10) is vertically placed in a constant-temperature water tank (20); the upper end of a platinum resistance thermometer (30) is fixed on a platinum resistance thermometer clamping device (40), the lower part of the platinum resistance thermometer is arranged in a constant temperature water tank (20), the measuring point of the platinum resistance thermometer (30) is arranged at the same height as the measuring point of a fiber bragg grating strain type sensor (102) and a fiber bragg grating temperature type sensor (103) in a fiber bragg grating strain type rebar meter (10), the fiber bragg grating strain type rebar meter (10) is connected to an upper computer (80) through a fiber bragg grating demodulator (50), the platinum resistance thermometer (30) is connected with a digital multi-purpose meter (60), the digital multi-purpose meter (60) is adjusted to a resistance grade, the temperature is started and preheated for 30min, and the serial port of the upper computer (80) is initialized;
Step 002: after the water temperature in the constant-temperature water tank (20) is regulated to 0 ℃ and is stabilized for 30 minutes, reading the temperature value, which is displayed by a digital multimeter (60), of the same height as the fiber grating strain sensor (102) in the constant-temperature water tank (20) and measured by a platinum resistance thermometer (30), and respectively reading the central wavelength value measured by the fiber grating strain sensor (102) and the temperature value measured by a fiber grating temperature sensor (103) in the fiber grating strain rebar meter (10) from an upper computer (80);
Then, taking each 10 ℃ as a primary temperature measuring point, gradually increasing the water temperature in the constant-temperature water tank (20) to 60 ℃, stabilizing for 30 minutes at each stage of temperature measuring points, and sequentially recording the measuring data of the platinum resistance thermometer (30), the fiber bragg grating strain type sensor (102) and the fiber bragg grating temperature sensor (103) according to the mode;
then, from 60 ℃, taking each 10 ℃ as a primary temperature measuring point, gradually reducing the water temperature in the constant-temperature water tank (20) to 0 ℃, stabilizing for 30 minutes at each stage of temperature measuring points, and sequentially recording the measuring data of the platinum resistance thermometer (30), the fiber bragg grating strain sensor (102) and the fiber bragg grating temperature sensor (103) according to the mode;
The method comprises the steps of taking average values of corresponding measurement data of a platinum resistance thermometer (30), a fiber bragg grating strain sensor (102) and a fiber bragg grating temperature sensor (103) at each stage of temperature measurement points in the temperature rise and temperature reduction processes and respectively serving as respective final measurement values, recording a temperature value measured by the fiber bragg grating temperature sensor (103) at 0 ℃ as an initial temperature value T F0, and recording a central wavelength value measured by the fiber bragg grating strain sensor (102) at 0 ℃ as an initial central wavelength value lambda T0;
Step 003: taking out the fiber grating strain type rebar meter (10) from the constant temperature water tank (20), fixing the upper end and the lower end of the rebar (101) on the standard load device (70), preloading the fiber grating strain type rebar meter (10) in the range of the fiber grating strain type rebar meter (10), recovering the fiber grating strain type rebar meter (10) to a zero load state and stabilizing, and reading a central wavelength value measured by the fiber grating strain type sensor (102) demodulated by the fiber grating demodulator (50) from the upper computer (80) to serve as an initial wavelength value lambda 0 of the fiber grating strain type rebar meter (10);
The preloading method comprises the steps of gradually loading to a full-scale load value by taking 10% of the full-scale as a first-stage load measuring point in the range of the fiber bragg grating strain type reinforcing bar gauge (10), stabilizing each stage for at least 3min, recording a standard load value applied by a standard load device (70) and a central wavelength value measured by a fiber bragg grating strain type sensor (102) on the corresponding fiber bragg grating strain type reinforcing bar gauge (10), synchronously recording an environmental temperature value T s near the fiber bragg grating strain type reinforcing bar gauge (10) measured by a fiber bragg grating temperature type sensor (103) at the corresponding load measuring point, gradually reducing the load from the full-scale load value to a zero load state according to the method, recording the measured values, and circularly measuring for 3 times;
Step 004: taking a temperature value T Ri of each stage of temperature measurement points in a constant-temperature water tank (20) measured by a platinum resistance thermometer (30) as an independent variable, wherein i=0, 1,2,3,4,5,6, and a temperature value T Fi of the constant-temperature water tank (20) measured by a fiber grating temperature sensor (103) corresponding to different temperature measurement points as an independent variable, wherein i=0, 1,2,3,4,5,6, performing least square straight line fitting according to a formula (1), thereby establishing a corresponding relation between the platinum resistance thermometer (30) and the temperature values measured by the fiber grating temperature sensor (103) and realizing temperature value calibration measured by the fiber grating temperature sensor (103):
TFWi＝kT×TRi+bR (1)
In the method, in the process of the invention,
T FWi -T Fi corresponding to T Ri on least squares line, i=0, 1,2,3,4,5,6
K T —temperature sensitivity coefficient;
b R -the temperature value measured by the fiber grating temperature sensor (103) on the least square straight line when the temperature value in the constant temperature water tank (20) is 0 ℃ is measured by the platinum resistance thermometer (30), and the temperature is lower than the temperature value;
Step 005: taking the variation delta T Fi of the temperature value of each stage of temperature measuring points in the constant-temperature water tank (20) measured by the fiber grating temperature sensor (103) after the calibration of the platinum resistance thermometer (30) relative to the initial temperature value T F0 as an independent variable, wherein delta T Fi＝TFi-TF0, i=0, 1,2,3,4,5,6, and taking the variation delta lambda Ti of the central wavelength value lambda Ti of each stage of temperature measuring points in the constant-temperature water tank (20) measured by the fiber grating strain sensor (102) and the same height as the fiber grating temperature sensor (103) relative to the initial central wavelength value lambda T0, wherein delta lambda Ti＝λTi-λT0,i＝0,1,2,3,4,5,6,λTi is the central wavelength value of each stage of temperature measuring points in the constant-temperature water tank (20) measured by the fiber grating strain sensor (102) and the same height as the fiber grating temperature sensor (103), and performing least square straight line fitting according to a formula (2), thereby establishing the corresponding relation between the temperature calibration value of the fiber grating temperature sensor (103) and the central wavelength of the fiber grating strain sensor (102);
ΔλTWi＝kλ×ΔTFi+bF (2)
In the method, in the process of the invention,
Δλ TWi —Δλ Ti, nm, i=0, 1,2,3,4,5,6 on the least squares line corresponding to Δt Fi;
k λ —strain sensitivity coefficient;
b F -the central wavelength variation, nm when the temperature value in the constant temperature water tank (20) is 0 ℃ measured by the fiber bragg grating strain sensor (102) on the least square straight line by the platinum resistance thermometer (30);
Step 006: substituting the environmental temperature value T Fij recorded by the fiber bragg grating temperature sensor (103) in the step 005 into a formula (2), wherein i=1, 2, … …,10, j=1, 2,3, … …,6, and calculating the central wavelength change delta lambda Tij of the fiber bragg grating strain sensor (102) caused by environmental temperature change at each stage of load measurement points, wherein i=1, 2, … …,10, j=1, 2,3, … …,6;
Calculating the average value of the difference value between the central wavelength value lambda ij and the initial wavelength value lambda 0 measured by the fiber bragg grating strain sensor (102) in the 3-cycle measurement process of each load measurement point according to the formula (3):
In the method, in the process of the invention,
Deltalambda i -the average value of the difference value between the central wavelength value and the initial wavelength value measured by the fiber bragg grating strain sensor (102) on the fiber bragg grating strain type reinforcing steel bar meter (10) in the 3-time cycle measurement process of the ith level load measurement point, and nm; wherein i=1, 2,3, … …,10;
Lambda ij -the central wavelength value measured by the fiber bragg grating strain sensor (102) on the fiber bragg grating strain type rebar meter (10) in the j-th measurement process of the i-th level load measurement point, nm; wherein i=1, 2,3, … …,10; j=1, 2,3, … …, m;
Δλ Tij —the amount of change in center wavelength measured by a fiber bragg grating strain sensor (102) due to ambient temperature changes, nm; wherein i=1, 2, … …,10, j=1, 2,3, … …,6;
m—number of times of measurement of loading and unloading strokes, m=6;
Taking an average value delta lambda i of the difference value between the central wavelength value and the initial wavelength value measured by a fiber grating strain sensor (102) on a fiber grating strain type reinforcing bar meter (10) as an independent variable, taking a load average value F i applied by a standard load device (70) as an independent variable, and carrying out least square method straight line fitting according to a formula (5), so as to obtain a load measurement value F Wi of the fiber grating type reinforcing bar meter (10):
wherein,
In the method, in the process of the invention,
F Pi, standard load applied by each stage of load measuring points in the loading stroke of the standard load device (70), and kN;
f Mi, standard load applied by each stage of load measuring points in the load reducing stroke of the standard load device (70), and kN;
FWi＝k×Δλi+C (5)
Wherein:
F Wi —f i, nm corresponding to Δλ i on the least squares line, where i=0, 1,2,3,4,5,6
K-sensitivity coefficient of fiber bragg grating strain type rebar meter (10), kN/nm;
c, measuring a load measured value and kN of the fiber bragg grating strain type reinforcing steel bar meter (10) in a free state;
Step 007: calculating the maximum error delta L between a load measurement value F Wi of the fiber bragg grating strain type rebar meter (10) and a load average value F i applied by a standard load device (70) according to a formula (6):
In the method, in the process of the invention,
F FS -full scale load value, kN, of the fiber bragg grating strain type rebar meter (10).
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