CN112945127A - Fiber grating strain type rebar meter metering calibration device and method - Google Patents
Fiber grating strain type rebar meter metering calibration device and method Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 claims abstract description 84
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- 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
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- 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
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Abstract
A fiber grating strain type reinforcing steel bar meter metering calibration device and method. The device comprises a fiber grating strain type steel bar meter, a constant-temperature water tank, a platinum resistance thermometer clamping device, a fiber 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 reinforcing steel bar meter metering technical specification exists in China at present, the invention provides a fiber grating strain type reinforcing steel bar meter metering calibration device and a fiber grating strain type reinforcing steel bar meter metering calibration method, which solve the influence of environmental temperature on the measurement precision of the fiber grating strain type reinforcing steel bar meter, provide a technical basis for the performance test of an instrument production unit before the fiber grating strain type reinforcing steel bar meter leaves a factory, provide an effective method for the field data correction of an application unit, and improve the measurement precision and the data reliability of the fiber grating strain type reinforcing steel bar meter.
Description
Technical Field
The invention belongs to the technical field of measurement and calibration of monitoring equipment of traffic and water transportation and highway engineering structures, and particularly relates to a fiber grating strain type rebar meter measurement and calibration device and method.
Background
In the fields of transportation and water transportation and highway engineering, the infrastructures and structures such as bridges and dams are influenced by external environment, material characteristics of the infrastructures and structural design and other factors in the process of construction and long-term use, so that damage accumulation and resistance attenuation are inevitably generated, the service life of the infrastructures is reduced, and if existing potential safety hazards are not checked in time, catastrophic accidents are caused, and major casualties and economic losses are caused, so that the health monitoring of important structures and infrastructures becomes a research hotspot of water transportation and highway engineering. The reinforcing steel bar is one of main bearing members of modern water transportation and highway engineering structures, is easily damaged under the influence of factors such as environmental corrosion, fatigue and material aging, takes strain and stress as one of important parameters for reacting material and structural mechanical characteristics, can obtain strength reserve information of the member according to strain distribution conditions in the material and the structure, determines stress concentration of the local position of the member and the actual load condition of the member, and has great monitoring significance.
At present, the monitoring means which is commonly used is to rigidly connect the measuring sensor with the steel bar into a whole in a cementing or fixing clamp manner, when the steel bar is axially or radially stretched or twisted, the measuring sensor generates the same change with the steel bar, and the generated strain is converted into light and electric signals and transmitted to an analyzer, so as to realize the dynamic and long-term monitoring of the mechanical property of the steel bar. The steel bar meters developed on the market based on the mode mainly comprise a vibrating wire type steel bar meter, a resistance strain type steel bar meter, a fiber grating strain type steel bar meter and the like, wherein the fiber grating strain type steel bar meter plays an important role in stress monitoring of structures such as highways, water transportation roads, dams, bridges and the like due to the advantages of small insertion loss, good reliability and stability, easiness in forming sensor networks and the like.
In the aspect of measurement and calibration of the fiber grating strain type steel bar meter, a 1-level universal material testing machine is used as a standard in the power industry standard 'basic technical conditions of a fiber grating instrument' (DL/T1736-. The building industry standard fiber grating strain sensor for civil engineering (JG/T42-2013) uses a strain sensor calibration frame as a standard device to regulate the mechanical properties of the fiber grating strain sensor, such as comprehensive error, resolution, repeatability and the like, and the strain sensor calibration frame cannot meet the clamping and calibration requirements of the fiber grating strain type steel bar meter in the measurement range and the measurement mode, so that the calibration method in the standard has high precision but cannot be applied to the fiber grating strain type steel bar meter, the environmental test temperature is regulated to be 20-25 ℃, and the influence of temperature change on the calibration result is not considered. The Chenxin stiffness of the hydrological instrument and geotechnical engineering instrument quality supervision, inspection and test center of the department of Water conservancy is tested according to the measurement performance indexes such as nonlinearity, nonrecurring degree, hysteresis, comprehensive error, full-scale output and the like of the fiber grating strain type steel bar meter of GB/T13606-2007 general technical conditions of vibrating string type sensors of geotechnical engineering instruments, but the measurement performance indexes are greatly different in working principle, the measurement method of the vibrating string type steel bar meter cannot completely reflect all the measurement performance of the fiber grating strain type steel bar meter, the effective quality control cannot be carried out on the manufacturers of the instruments, and the product quality leaving factories and the safety of the use engineering of the instruments cannot be ensured.
Therefore, the device and the method for calibrating the measurement of the fiber grating strain type steel bar meter are researched to realize the high-precision calibration of the mechanical performance of the fiber grating strain type steel bar meter, effectively reduce the influence of the environmental temperature change on the calibration result and have important significance for improving the product quality of the fiber grating strain type steel bar meter.
Disclosure of Invention
In order to solve the above problems, an object of the present invention is to provide a fiber grating strain gauge measurement calibration apparatus.
In order to achieve the aim, the fiber grating strain type steel bar meter measuring and calibrating device provided by the invention comprises a fiber grating strain type steel bar meter, a constant-temperature water tank, a platinum resistance thermometer clamping device, a fiber grating demodulator, a digital multimeter, a standard load device and an upper computer; the fiber bragg grating strain type steel bar meter is vertically placed in a constant-temperature water tank during temperature calibration; the platinum resistance thermometer is vertically placed in the constant-temperature water tank through the platinum resistance thermometer clamping device; the fiber bragg grating demodulator is electrically connected with the fiber bragg grating strain type steel bar gauge and the upper computer at the same time; the platinum resistance thermometer is electrically connected with the digital multimeter; the fiber bragg grating strain type steel bar meter is fixed on the standard load device during mechanical property calibration, and the standard load device is electrically connected with the upper computer.
The fiber grating strain type steel bar meter comprises steel bars, a fiber grating strain type sensor and a fiber grating temperature type sensor; the fiber grating strain sensor and the fiber grating temperature sensor are fixed outside the steel bar, the axial direction of the fixed part on the fiber grating strain sensor and the fiber grating temperature sensor is parallel to the axial direction of the steel bar, and two ends of the fiber grating strain sensor and the fiber grating temperature sensor are connected to the fiber grating demodulator.
The reinforcing steel bar is made of deformed steel bars or round steel bars, and the section diameter is 12mm, 14mm, 16mm, 18mm or 22 mm.
In the constant temperature water tank, the fiber grating strain sensor, the fiber grating temperature sensor and the platinum resistance thermometer are arranged at the same height as each other.
The platinum resistance thermometer adopts a four-wire first-class or second-class standard platinum resistance thermometer.
The metering calibration method adopting the fiber grating strain type rebar meter metering calibration device comprises the following steps in sequence:
step 001: vertically placing a fiber bragg grating strain type steel bar 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 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 grating strain sensor and the measuring point of a fiber grating temperature sensor in a fiber grating strain type reinforcing bar meter, the fiber grating strain type reinforcing bar meter is connected to an upper computer through a fiber grating demodulator, the platinum resistance thermometer is connected with a digital multimeter, the digital multimeter is adjusted to a resistance level, the platinum resistance thermometer is preheated for 30min after being started up, and the serial port of the upper computer;
step 002: adjusting the water temperature in the constant-temperature water tank to 0 ℃, after stabilizing for 30 minutes, reading the temperature value at the height of the constant-temperature water tank, which is measured by a platinum resistance thermometer and is equal to the fiber grating strain sensor, displayed by a digital multimeter, and respectively reading the central wavelength value measured by the fiber grating strain sensor and the temperature value measured by the fiber grating temperature sensor in the fiber grating strain type steel bar gauge from an upper computer;
then, taking every 10 ℃ as a first-stage temperature measuring point, gradually increasing the water temperature in the constant-temperature water tank to 60 ℃, and after the water temperature is stabilized for 30 minutes at each stage of temperature measuring point, sequentially recording the measuring data of the platinum resistance thermometer, the fiber grating strain type sensor and the fiber grating temperature type sensor according to the mode;
then, from 60 ℃, taking every 10 ℃ as a first-stage temperature measuring point, reducing the water temperature in the constant-temperature water tank to 0 ℃ step by step, and after the temperature at each stage is stabilized for 30 minutes, sequentially recording the measurement data of the platinum resistance thermometer, the fiber grating strain type sensor and the fiber grating temperature type sensor according to the mode;
averaging corresponding measurement data of the platinum resistance thermometer, the fiber grating strain sensor and the fiber grating temperature sensor at each temperature measurement point in the temperature rising and lowering processes, respectively taking the average value as respective final measurement value, and recording the temperature value measured by the fiber grating temperature sensor at 0℃ asInitial temperature value TF0Recording the central wavelength value measured by the fiber grating strain sensor at 0 ℃ as the initial central wavelength value lambdaT0；
Step 003: taking the fiber grating strain type reinforcing steel bar meter out of the constant-temperature water tank, fixing the upper end and the lower end of a reinforcing steel bar on a standard load device, preloading the fiber grating strain type reinforcing steel bar meter within the measuring range of the fiber grating strain type reinforcing steel bar meter, recovering the fiber grating strain type reinforcing steel bar meter to be in a zero load state and after the fiber grating strain type reinforcing steel bar meter is stabilized, reading a central wavelength value measured by a fiber grating strain type sensor demodulated by a fiber grating demodulator from an upper computer, and taking the central wavelength value as an initial wavelength value lambda of the fiber grating strain type reinforcing steel bar meter0；
The preloading method comprises the steps of taking 10% of full range as a first-level load measuring point within the range of the fiber grating strain type steel bar meter, gradually loading to a full-range load value, stabilizing each level for at least 3min, recording a standard load value applied by a standard load device and a corresponding central wavelength value measured by a fiber grating strain type sensor on the fiber grating strain type steel bar meter, and synchronously recording an environmental temperature value T near the fiber grating strain type steel bar meter measured by the fiber grating temperature type sensor at the corresponding load measuring pointsThen, 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: temperature value T measured by platinum resistance thermometer at each temperature measuring point in constant-temperature water tankRi(i is 0, 1,2,3, 4, 5, 6) as an independent variable, and temperature values T corresponding to different temperature measurement points in a constant-temperature water tank measured by a fiber grating temperature sensorFi(i ═ 0, 1,2,3, 4, 5, 6) as a dependent variable, and by performing least square linear fitting according to equation (1), a correspondence relationship between the platinum resistance thermometer and the temperature value measured by the fiber grating temperature sensor is established, so as to realize calibration of the temperature value measured by the fiber grating temperature sensor:
TFWi＝kT×TRi+bR (1)
in the formula,
TFWi-on the least squares line with TRiCorresponding TFi，i＝0，1，2，3，4，5，6
kT-temperature sensitivity factor;
bRthe fiber grating temperature sensor on the least square straight line measures the temperature value at 0 ℃ in the constant temperature water tank measured by the platinum resistance thermometer;
step 005: the temperature value of each temperature measuring point in the constant temperature water tank measured by the fiber grating temperature sensor calibrated by the platinum resistance thermometer is relative to the initial temperature value TF0Change amount of (Δ T)Fi(ΔTFi＝TFi-TF0I is 0, 1,2,3, 4, 5, 6) as an independent variable, and a central wavelength value lambda is measured at each temperature measurement point at a height level such as a fiber grating temperature sensor in a constant temperature water tank measured by the fiber grating strain sensorTiRelative to the initial central wavelength value λT0Change amount of (a) λTi(ΔλTi＝λTi-λT0I-0, 1,2,3, 4, 5, 6) as a dependent variable, where λTiPerforming least square linear fitting according to a formula (2) for central wavelength values of all levels of temperature measurement points at the same height as the fiber grating temperature type sensor in a constant-temperature water tank measured by the fiber grating strain type sensor, and thus establishing a corresponding relation between the temperature calibration value of the fiber grating temperature type sensor and the central wavelength value measured by the fiber grating strain type sensor;
ΔλTi＝kλ×ΔTFi+bF (2)
in the formula,
ΔλTWi-least squares on-line with Δ TFiCorresponding delta lambdaTi(i＝0，1，2，3，4，5，6)，nm；
kλ-a strain sensitivity coefficient;
bFthe variation of the central wavelength of the fiber grating strain type sensor on the least square straight line is nm when the platinum resistance thermometer measures the temperature value in the constant-temperature water tank to be 0 ℃.
Step 006: the environmental temperature value T recorded by the fiber bragg grating temperature type sensor in the step 005 at each level of load measuring pointFijSubstituting ( i 1,2, … …, 10, j 1,2,3, … …, 6) into equation (2), and calculating the central wavelength variation Δ λ of the fiber grating strain gauge sensor due to the change of the environmental temperature at each stage of the load measuring pointTij(i＝1，2，……，10，j＝1，2，3，……，6)；
Calculating the central wavelength value lambda measured by the fiber grating strain sensor in the 3 times cyclic measurement process of each load measurement point according to the formula (3)ijWith an initial wavelength value λ0Average value of difference:
in the formula,
Δλi-the average value of the difference between the central wavelength value and the initial wavelength value measured by the fiber grating strain gauge sensor on the fiber grating strain gauge during 3 times of cyclic measurement at the i-th level load measurement point (i ═ 1,2,3, … …, 10);
λij-the central wavelength value, nm, measured by the fiber grating strain gauge sensor on the fiber grating strain gauge during the ith load measurement point (i ═ 1,2,3, … …, 10) and the jth (j ═ 1,2,3, … …, m) measurement;
ΔλTijthe amount of change in the center wavelength measured by the fiber grating strain gauge sensor due to a change in the ambient temperature ( i 1,2, … …, 10, j 1,2,3, … …, 6), nm;
m is the number of times of measuring the loading and unloading travel, and m is 6.
Average value delta lambda of difference value between central wavelength value and initial wavelength value measured by fiber grating strain type sensor on fiber grating strain type reinforcing bar meteriAs independent variable, average value F of the load applied by a standard loading deviceiPerforming least square method linear fitting according to a formula (5) as a dependent variable, and calculating to obtain a load measurement value of the fiber grating type reinforcing steel bar meterFWi：
Wherein,
in the formula,
FPi-standard load applied by each level of load measuring point during the loading stroke of the standard load device, kN;
FMithe standard load applied by each level of load measuring point during the load reduction stroke of the standard load device is kN;
FWi＝k×Δλi+C (5)
in the formula:
FWi-on the least squares line with Δ λiCorresponding Fi(i ═ 0, 1,2,3, 4, 5, 6), nmk — coefficient of sensitivity of fiber grating strain gauge, kN/nm;
c is the load measurement value kN of the fiber grating strain type reinforcing steel bar meter in the free state.
Step 007: calculating the load measurement value F of the fiber grating strain type reinforcing steel bar meter according to the formula (6)WiAverage value F of load applied by standard load deviceiMaximum error delta betweenL。
In the formula,
FFSthe full-scale load value kN of the fiber grating strain gauge type rebar meter 10.
The invention has the beneficial effects that: aiming at the current situation that no special fiber grating strain type reinforcing steel bar meter metering technical specification exists in China at present, the invention provides a fiber grating strain type reinforcing steel bar meter metering calibration device and a fiber grating strain type reinforcing steel bar meter metering calibration method, which solve the influence of environmental temperature on the measurement precision of the fiber grating strain type reinforcing steel bar meter, provide a technical basis for the performance test of an instrument production unit before the fiber grating strain type reinforcing steel bar meter leaves a factory, provide an effective method for the field data correction of an application unit, and improve the measurement precision and the data reliability of the fiber grating strain type reinforcing steel bar meter.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention.
Fig. 1 is a structural diagram of a fiber grating strain gauge measurement calibration device provided by the invention.
Fig. 2 is a flow chart of a metering calibration method of a fiber grating strain gauge steel bar meter provided by the invention.
Fig. 3 is a structural diagram of a fiber grating strain gauge steel bar meter in the fiber grating strain gauge steel bar meter measuring and calibrating device provided by the invention.
FIG. 4 is a least square linear fitting result diagram of the corresponding temperature measurement points of the fiber grating temperature sensor and the platinum resistance thermometer.
FIG. 5 is a least square method straight line fitting result diagram of the central wavelength value of the fiber grating strain sensor and the temperature correction value of the corresponding temperature measurement point of the fiber grating temperature sensor.
FIG. 6 is a least square method straight line fitting result diagram of the standard load value output by the standard load device and the central wavelength variation measured by the corresponding load measuring point of the fiber grating strain type reinforcing steel meter.
Detailed Description
The following describes in detail the measurement and calibration device and method of the fiber grating strain gauge rebar meter according to the present invention with reference to the accompanying drawings and specific embodiments.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
As shown in fig. 1, the fiber grating strain gauge measurement and calibration device provided by the invention comprises a fiber grating strain gauge 10, a constant temperature water tank 20, a platinum resistance thermometer 30, a platinum resistance thermometer clamping device 40, a fiber grating demodulator 50, a digital multimeter 60, a standard load device 70 and an upper computer 80; the fiber bragg grating strain type steel bar meter 10 is vertically placed in a constant-temperature water tank 20 during temperature calibration; the platinum resistance thermometer 30 is vertically placed in the constant-temperature water tank 20 through a platinum resistance thermometer clamping device 40; the fiber grating demodulator 50 is simultaneously electrically connected with the fiber grating strain type steel bar meter 10 and the upper computer 80; the platinum resistance thermometer 30 is electrically connected with the digital multimeter 60; the fiber grating strain type steel bar meter 10 is fixed on the standard load device 70 during mechanical property calibration, and the standard load device 70 is electrically connected with the upper computer 80.
As shown in fig. 3, the fiber grating strain gauge 10 includes a steel bar 101, a fiber grating strain sensor 102 and a fiber grating temperature sensor 103; 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 sizes; the fiber grating strain sensor 102 and the fiber grating temperature sensor 103 are fixed at the middle part outside the steel bar 101, the axial direction of the fixed part on the fiber grating strain sensor 102 and the fiber grating temperature sensor 103 is parallel to the axial direction of the steel bar 101, and the two ends are connected to the fiber grating demodulator 50.
In the fiber grating strain gauge 10, the temperature measuring range of the fiber grating temperature sensor 103 is (-30- + 125) DEG C, and the temperature resolution is 0.1 ℃.
In the constant-temperature water tank 20, the fiber grating strain gauge 102 and the fiber grating temperature gauge 103 in the fiber grating strain gauge 10 are placed at the same height as the measurement points of the platinum resistance thermometer 30.
The temperature variation range of the constant temperature water tank 20 is (-5- + 100 ℃), the temperature fluctuation degree is +/-0.05 ℃, and the temperature uniformity degree is +/-0.05 ℃.
The platinum resistance thermometer 30 is a four-wire first-class or second-class standard platinum resistance thermometer.
The strain measuring range of the fiber bragg grating strain type steel bar meter measuring and calibrating device is (-1500- + 1500) mu epsilon, the diameter of the selection steel bar 101 is 16mm, the material is 304 steel, and when the shape is round steel, the measuring uncertainty is U-0.74 kN, and k-2.
As shown in fig. 2, the measurement calibration method using the fiber grating strain gauge measurement calibration apparatus includes the following steps performed in sequence:
step 001: device connection initialization:
vertically placing the fiber bragg grating strain type steel bar meter 10 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 30 is placed in a constant temperature water tank 20, the measuring point of the platinum resistance thermometer 30 is arranged to be equal to the measuring point of a fiber grating strain sensor 102 and a fiber grating temperature sensor 103 in a fiber grating strain type rebar meter 10 in height, the fiber grating strain type rebar meter 10 is connected to an upper computer 80 through a fiber grating demodulator 50, the platinum resistance thermometer 30 is connected with a digital multimeter 60, the digital multimeter 60 is adjusted to a resistance level, the machine is started to preheat for 30min, and the serial port of the upper computer 80 is initialized;
adjusting the water temperature in the constant-temperature water tank 20 to 0 ℃, after stabilizing for 30 minutes, reading the temperature value at the height of the fiber grating strain sensor 102 and the like in the constant-temperature water tank 20, which is measured by the platinum resistance thermometer 30 and is displayed by the digital multimeter 60, and respectively reading the central wavelength value measured by the fiber grating strain sensor 102 in the fiber grating strain type steel bar meter 10 and the temperature value measured by the fiber grating temperature type sensor 103 from the upper computer 80;
then, taking every 10 ℃ as a first-stage temperature measuring point, gradually increasing the water temperature in the constant-temperature water tank 20 to 60 ℃, and after the water temperature is stabilized for 30 minutes at each stage of temperature measuring point, sequentially recording the measuring data of the platinum resistance thermometer 30, the fiber grating strain type sensor 102 and the fiber grating temperature type sensor 103 according to the mode;
then, from 60 ℃, taking every 10 ℃ as a first-stage temperature measuring point, gradually reducing the water temperature in the constant-temperature water tank 20 to 0 ℃, and after the temperature at each stage is stabilized for 30 minutes, sequentially recording the measurement data of the platinum resistance thermometer 30, the fiber grating strain sensor 102 and the fiber grating temperature sensor 103 according to the above mode;
a platinum resistance thermometer 30 in the temperature rising and reducing process,Corresponding measurement data of the fiber grating strain sensor 102 and the fiber grating temperature sensor 103 at each temperature measurement point are averaged and respectively used as respective final measurement values, and the temperature value measured by the fiber grating temperature sensor 103 at 0 ℃ is recorded as an initial temperature value TF0The central wavelength value measured by the fiber grating strain sensor 102 at 0 ℃ is recorded as the initial central wavelength value lambdaT0；。
taking the fiber grating strain type reinforcing steel bar meter 10 out of the constant-temperature water tank 20, fixing the upper end and the lower end of a reinforcing steel bar 101 on the standard load device 70, preloading the fiber grating strain type reinforcing steel bar meter 10 within the measuring range of the fiber grating strain type reinforcing steel bar meter 10, recovering the fiber grating strain type reinforcing steel bar meter 10 to be in a zero-load state and stable, 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, and taking the central wavelength value as an initial wavelength value lambda of the fiber grating strain type reinforcing steel bar meter 100；
The preloading method comprises the steps of within the range of the fiber grating strain type reinforcing steel bar meter 10, taking 10% of the full range as a first-stage load measuring point, 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 corresponding central wavelength value measured by a fiber grating strain type sensor 102 on the fiber grating strain type reinforcing steel bar meter 10, and synchronously recording an environmental temperature value T near the fiber grating strain type reinforcing steel bar meter 10 measured by a fiber grating temperature type sensor 103 at the corresponding load measuring pointsThen, 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;
temperature value T measured by platinum resistance thermometer 30 at each temperature measurement point in constant temperature water tank 20Ri(i is 0, 1,2,3, 4, 5, 6) as an independent variable, and the constant temperature water tank 20 measured by the fiber grating temperature sensor 103 corresponds toTemperature value T at different temperature measurement pointsFi(i is 0, 1,2,3, 4, 5, 6) as a dependent variable, and performing least square linear fitting according to formula (1), thereby establishing a corresponding relationship between the platinum resistance thermometer 30 and the temperature value 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 formula,
TFWi-on the least squares line with TRiCorresponding TFi，i＝0，1，2，3，4，5，6
kT-temperature sensitivity factor;
bRthe fiber grating temperature sensor 103 on the least square straight line measures the temperature value at 0 ℃ in the constant temperature water tank 20 measured by the platinum resistance thermometer 30;
005, establishing a corresponding relation between the temperature calibration value of the fiber grating temperature type sensor 103 and the central wavelength value measured by the fiber grating strain type sensor 102:
the temperature value at each temperature measuring point in the constant temperature water tank 20 measured by the fiber bragg grating temperature type sensor 103 calibrated by the platinum resistance thermometer 30 is relative to the initial temperature value TF0Change amount of (Δ T)Fi(ΔTFi＝TFi-TF0I is 0, 1,2,3, 4, 5, 6) as an independent variable, and the center wavelength value λ at each temperature measurement point at a position such as a height of the fiber grating temperature sensor 103 in the constant temperature water tank 20 measured by the fiber grating strain sensor 102TiRelative to the initial central wavelength value λT0Change amount of (a) λTi(ΔλTi＝λTi-λT0I-0, 1,2,3, 4, 5, 6) as a dependent variable, where λTiThe central wavelength value of each temperature measurement point at each level at the same height as the fiber grating temperature sensor 103 in the constant temperature water tank 20 measured by the fiber grating strain sensor 102 is subjected to least square linear fitting according to the formula (2), thereby establishing the temperature calibration value of the fiber grating temperature sensor 103The corresponding relation between the central wavelength value measured by the fiber bragg grating strain gauge sensor 102;
ΔλTi＝kλ×ΔTFi+bF (2)
in the formula,
ΔλTWi-least squares on-line with Δ TFiCorresponding delta lambdaTi(i＝0，1，2，3，4，5，6)，nm；
kλ-a strain sensitivity coefficient;
bFthe fiber grating strain gauge sensor 102 on the least squares straight line measures the central wavelength variation, nm, of the temperature value in the constant temperature water tank 20 at 0 ℃ in the platinum resistance thermometer 30.
the environmental temperature value T recorded by the fiber bragg grating temperature type sensor 103 in the step 005 at each level of load measuring pointFij(i is 1,2, … …, 10, j is 1,2,3, … …, 6) is substituted into the formula (2), and the central wavelength variation quantity delta lambda of the fiber grating strain gauge sensor 102 caused by the environmental temperature variation at each stage of load measuring point is calculatedTij(i＝1，2，……，10，j＝1，2，3，……，6)；
Calculating the central wavelength value lambda measured by the fiber grating strain sensor 102 in the 3-time cyclic measurement process of each load measurement point according to the formula (3)ijWith an initial wavelength value λ0Average value of difference:
in the formula,
Δλithe average value of the difference between the central wavelength value and the initial wavelength value measured by the fiber grating strain gauge 102 on the fiber grating strain gauge 10 in the 3-cycle measurement process at the i-th-level load measurement point (i ═ 1,2,3, … …, 10) is nm;
λij-the ith load measuring point (i ═ 1,2,3, … …, 10) for the jth time(j ═ 1,2,3, … …, m) the central wavelength value, nm, measured by the fiber grating strain gauge sensor 102 on the fiber grating strain gauge 10 during the measurement;
ΔλTijthe amount of change in the center wavelength measured by the fiber grating strain gauge sensor 102 due to a change in the ambient temperature ( i 1,2, … …, 10, j 1,2,3, … …, 6), nm;
m is the number of times of measuring the loading and unloading travel, and m is 6.
The average value delta lambda of the difference value between the central wavelength value and the initial wavelength value measured by the fiber grating strain type sensor 102 on the fiber grating strain type steel bar meter 10iAs independent variable, the average value F of the load applied by the standard load device 70 is usediPerforming least square method linear fitting according to a formula (5) as a dependent variable, and calculating to obtain a load measurement value F of the fiber grating type reinforcing steel bar meter 10Wi：
Wherein,
in the formula,
FPithe standard load applied by each level of load measuring point during the loading stroke of the standard load device 70, kN;
FMithe standard load applied by each level of load measuring point during the load reduction stroke of the standard load device 70 is kN;
FWi＝k×Δλi+C (5)
in the formula:
FWi-on the least squares line with Δ λiCorresponding Fi(i＝0，1，2，3，4，5，6)，nm
k is the sensitivity coefficient of the fiber grating strain type steel bar meter 10, kN/nm;
c is the load measurement value kN of the fiber grating strain type reinforcing steel bar meter 10 in the free state.
calculating the fiber grating response according to the formula (6)Load measurement value F of variable reinforcing bar meter 10WiAverage value F of load applied by standard load device 70iMaximum error delta betweenL。
In the formula,
FFSthe full-scale load value kN of the fiber grating strain gauge type rebar meter 10.
When the device works, a 304-material round steel type fiber grating type reinforcing steel bar meter with the section diameter of 22mm is selected for verification, the measuring range of the fiber grating type reinforcing steel bar meter 10 is 0-40kN, temperature correction is firstly carried out on the fiber grating strain type reinforcing steel bar meter 10, a platinum resistance thermometer 30 is used as a measuring standard, the platinum resistance thermometer 30 and a fiber grating temperature type sensor 103 on the fiber grating strain type reinforcing steel bar meter 10 are placed in the constant-temperature water tank 20 at the same height, in the range of 0-60 ℃, every 10 ℃ is used as a first-level temperature measuring point, temperature rise and temperature reduction tests are carried out, and the measurement data of each sensor in the temperature rise and temperature reduction process at each temperature measuring point are averaged to be used as a final measurement value, as shown in table 1.
TABLE 1 measurement data of various sensors in constant-temperature water tank
The corresponding relationship between the temperature value measured by the platinum resistance thermometer 30 and the temperature value measured by the fiber grating temperature sensor 103 at the corresponding temperature measurement point at the same height as the platinum resistance thermometer 30 in the constant temperature water tank 30 is established according to the formula (1), as shown in fig. 4, there are:
TFWi＝1.002×TRi+0.249 (7)
thereby obtaining TFWiThe values of (A) are shown in Table 2.
TABLE 2 temperature correction value of fiber grating temperature sensor
| Serial number | Temperature measurement value (. degree. C.) of fiber grating temperature sensor | Temperature correction value (DEG C) of fiber bragg grating |
| 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 |
According to the formula (2), the corresponding relationship between the difference value of the temperature correction value of the fiber grating temperature sensor 103 at each temperature measurement point in the constant temperature water tank 30 relative to the temperature correction value at the initial temperature value and the central wavelength variation value of the fiber grating strain gauge sensor 102 at the corresponding temperature measurement point is established, and because the central wavelength variation is small, the central wavelength variation value is amplified by 1000 times and then subjected to least square method straight line fitting, as shown in fig. 5, the method comprises the following steps:
ΔλTi＝0.631×ΔTFi-0.288 (8)
the fiber grating strain type steel bar meter 10 is fixed on a standard load device 70, a 0.1-level microcomputer control superposition type force standard machine is selected, the measurement range is 0-100kN, the fiber grating strain type steel bar meter 10 is loaded and unloaded step by step according to 10% of full range (F.S) within the measurement range of 0-40kN, and the measurement data are shown in table 3.
TABLE 3 center wavelength values during loading-unloading of fiber grating strain type rebar gauges
During the measurement, the laboratory temperature is kept within (21 ± 2) ° c, and when the temperature reaches the upper limit of 22 ℃, the temperature can be obtained according to the formula (8):
ΔλTi＝[0.631×(23-0)-0.288]/1000＝0.0142nm
then when the temperature reaches the lower limit of 19 ℃, it can be obtained according to equation (8):
ΔλTi＝[0.631×(19-0)-0.288]/1000＝0.0117nm
when the temperature is maintained at 21 ℃, it can be obtained according to the formula (8):
ΔλTi＝[0.631×(21-0)-0.288]/1000＝0.0130nm
then within the range of the upper and lower limits of the temperature change, lambda is tested0Is measured at 0 deg.C, in this embodiment, for the convenience of calculation, the change value of the central wavelength at 23 deg.C of the upper limit value of the temperature change is temporarily taken as Δ λTijA value of (1), i.e. let Δ λTijWhen the average particle diameter is 0.0142nm, Δ λ is calculated according to the formula (3)iThe results are shown in Table 4, where λ0F is calculated by equation (4) at 1584.785nmiThe results are also shown in Table 4.
Table 4 central wavelength variation value and standard load value of fiber grating strain type reinforcing bar meter in loading-unloading process
Calculating a standard load value F according to the formula (5)iCentral wavelength variation delta lambda of strain type steel bar meter with fiber bragg gratingiThe correspondence between them, as shown in fig. 6, includes:
FWi＝16.123×Δλi+2.395 (9)
each level of the standard loading value F applied to the standard loading device 70iThe temperature compensated load values measured by the fiber grating strain gauge 10 are shown in table 5.
TABLE 5 Standard and measured load values at the load measurement points
In table 5, when the load is 0kN, that is, the fiber grating strain gauge 10 is in a free state, through the three preloading-unloading processes and the forward and backward stroke test processes, although the load is 0, the fiber grating strain gauge 10 does not return to an unstressed state, so that the error is large when the load is 0kN, and this data can be rejected during calculation, which is shown in formula (6):
when the fiber grating strain type steel bar gauge is applied on site, the k and C values are generally provided for a using unit, and if the stable compensation calibration is not carried out according to the method provided by the invention, the fiber grating strain type steel bar gauge 10 has central wavelength variation delta lambda caused by temperature variation at 23 DEG CTijThe load measurement value of the fiber grating strain gauge 10 has an error of 16.123 × 0.0142 ═ 0.229kN at 0.0142nm, which affects the accuracy and reliability of the field measurement data.
The above-mentioned embodiments are only for illustrating the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and to carry out the same, and the present invention shall not be limited to the embodiments, i.e. the equivalent changes or modifications made within the spirit of the present invention shall fall within the scope of the present invention.
Claims (6)
1. The utility model provides a fiber grating strain gauge rebar meter measurement calibrating device which characterized in that: the fiber grating strain type steel bar meter measuring and calibrating device comprises a fiber 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 grating demodulator (50), a digital multimeter (60), a standard load device (70) and an upper computer (80); the fiber bragg grating strain type steel bar meter (10) is vertically placed in a constant-temperature water tank (20) during temperature calibration; the platinum resistance thermometer (30) is vertically placed in the constant-temperature water tank (20) through a platinum resistance thermometer clamping device (40); the fiber grating demodulator (50) is simultaneously electrically connected with the fiber grating strain type steel bar meter (10) and the upper computer (80); the platinum resistance thermometer (30) is electrically connected with the digital multimeter (60); the fiber bragg grating strain type steel bar meter (10) is fixed on a standard load device (70) during mechanical property calibration, and the standard load device (70) is electrically connected with an upper computer (80).
2. The fiber grating strain gauge rebar gauge metering and calibrating device of claim 1, wherein: the fiber grating strain type steel bar meter (10) comprises steel bars (101), a fiber grating strain type sensor (102) and a fiber grating temperature type sensor (103); the fiber grating strain sensor (102) and the fiber grating temperature sensor (103) are fixed at the middle parts outside the steel bar (101), the axial directions of the fixed parts on the fiber grating strain sensor (102) and the fiber grating temperature sensor (103) are parallel to the axial direction of the steel bar (101), and two ends of the fixed parts are connected to the fiber grating demodulator (50).
3. The fiber grating strain gauge rebar gauge metering and calibrating device of claim 2, wherein: the steel bar (101) is made of deformed steel bars or round steel bars, and the section diameter is 12mm, 14mm, 16mm, 18mm or 22 mm.
4. The fiber grating strain gauge rebar gauge metering and calibrating device of claim 1, wherein: in the constant temperature water tank (20), the fiber grating strain type sensor (102) and the fiber grating temperature type sensor (103) are arranged at the same height as the measuring point of the platinum resistance thermometer (30).
5. The fiber grating strain gauge rebar gauge metering and calibrating device of claim 1, wherein: the platinum resistance thermometer (30) adopts a four-wire first-class or second-class standard platinum resistance thermometer.
6. A measurement calibration method using the measurement calibration device for the fiber grating strain gauge steel bar according to any one of claims 1 to 5, characterized in that: the metering calibration method comprises the following steps which are carried out in sequence:
step 001: vertically placing the fiber bragg grating strain type steel bar meter (10) 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 placed in a constant-temperature water tank (20), the measuring point of the platinum resistance thermometer (30) and the measuring points of a fiber grating strain sensor (102) and a fiber grating temperature sensor (103) in a fiber grating strain type rebar meter (10) are arranged at the same height, the fiber grating strain type rebar meter (10) is connected to an upper computer (80) through a fiber grating demodulator (50), the platinum resistance thermometer (30) is connected with a digital multimeter (60), the digital multimeter (60) is adjusted to a resistance level, the platinum resistance thermometer is started to be preheated for 30min, and the serial port of the upper computer (80) is initialized;
step 002: adjusting the water temperature in the constant-temperature water tank (20) to 0 ℃, after stabilizing for 30 minutes, reading the temperature value which is displayed by a digital multimeter (60) and is measured by a platinum resistance thermometer (30) and is at the same height as the fiber grating strain sensor (102) in the constant-temperature water tank (20), and respectively reading the central wavelength value measured by the fiber grating strain sensor (102) in the fiber grating strain type steel bar meter (10) and the temperature value measured by the fiber grating temperature type sensor (103) from an upper computer (80);
then, taking every 10 ℃ as a first-stage temperature measuring point, gradually increasing the water temperature in the constant-temperature water tank (20) to 60 ℃, and after the temperature in each stage of temperature measuring point is stabilized for 30 minutes, sequentially recording the measuring data of the platinum resistance thermometer (30), the fiber grating strain type sensor (102) and the fiber grating temperature type sensor (103) according to the mode;
then, from 60 ℃, taking every 10 ℃ as a first-stage temperature measuring point, reducing the water temperature in the constant-temperature water tank (20) to 0 ℃ step by step, and after the temperature at each stage is stabilized for 30 minutes, sequentially recording the measuring data of the platinum resistance thermometer (30), the fiber grating strain type sensor (102) and the fiber grating temperature type sensor (103) according to the mode;
corresponding measurement data of the platinum resistance thermometer (30), the fiber grating strain sensor (102) and the fiber grating temperature sensor (103) at each temperature measurement point in the temperature rising and reducing processes are averaged and respectively taken as respective final measurement values, and the temperature value measured by the fiber grating temperature sensor (103) at 0 ℃ is recorded as an initial temperature value TF0The center of the measurement of the fiber bragg grating strain-type sensor (102) at 0 DEG CThe wavelength value is recorded as the initial central wavelength value lambdaT0；
Step 003: taking the fiber grating strain type steel bar meter (10) out of the constant-temperature water tank (20), fixing the upper end and the lower end of a steel bar (101) on a standard load device (70), preloading the fiber grating strain type steel bar meter (10) within the measuring range of the fiber grating strain type steel bar meter (10), recovering the fiber grating strain type steel bar meter (10) to a zero-load state and stabilizing, reading a central wavelength value measured by a fiber grating strain type sensor (102) demodulated by a fiber grating demodulator (50) from an upper computer (80) and taking the central wavelength value as an initial wavelength value lambda of the fiber grating strain type steel bar meter (10)0；
The preloading method comprises the steps of within the range of the fiber grating strain type reinforcing steel bar meter (10), taking 10% of full range as a first-stage load measuring point, 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 sensor (102) on the corresponding fiber grating strain type reinforcing steel bar meter (10), and synchronously recording an environmental temperature value T near the fiber grating strain type reinforcing steel bar meter (10) measured by the fiber grating temperature type sensor (103) at the corresponding load measuring pointsThen, 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: temperature value T measured by platinum resistance thermometer (30) at each temperature measuring point in constant temperature water tank (20)RiAs an independent variable, i is 0, 1,2,3, 4, 5, 6, and a temperature value T corresponding to different temperature measurement points in a constant temperature water tank (20) measured by a fiber grating temperature sensor (103)FiAs a dependent variable, i is 0, 1,2,3, 4, 5, 6, and a least square method straight line fitting is carried out according to the formula (1), thereby establishing a corresponding relation between the platinum resistance thermometer (30) and the temperature value measured by the fiber grating temperature sensor (103) to realize the temperature value calibration measured by the fiber grating temperature sensor (103):
TFWi＝kT×TRi+bR (1)
in the formula,
TFWi-on the least squares line with TRiCorresponding TFi，i＝0，1，2，3，4，5，6
kT-temperature sensitivity factor;
bR-the fiber grating temperature sensor (103) on the least squares line measures the temperature value, deg.c, at 0 deg.c in the constant temperature water bath (20) measured by the platinum resistance thermometer 30;
step 005: the temperature value of each stage of temperature measuring points in the constant temperature water tank (20) measured by the fiber grating temperature type sensor (103) calibrated by the platinum resistance thermometer (30) is relative to the initial temperature value TF0Change amount of (Δ T)FiAs an independent variable, where Δ TFi＝TFi-TF0I is 0, 1,2,3, 4, 5, 6, and the center wavelength value lambda is measured at each temperature measurement point at a level equal to the fiber grating temperature sensor 103 in the constant temperature water tank 20 measured by the fiber grating strain sensor 102TiRelative to the initial central wavelength value λT0Change amount of (a) λTiAs a dependent variable, where Δ λTi＝λTi-λT0，i＝0，1，2，3，4，5，6，λTiPerforming least square linear fitting according to a formula (2) for central wavelength values of all levels of temperature measurement points at the same height as the fiber grating temperature type sensor (103) in a constant-temperature water tank (20) measured by the fiber grating strain type sensor (102), thereby establishing a corresponding relation between the temperature calibration value of the fiber grating temperature type sensor (103) and the central wavelength value measured by the fiber grating strain type sensor (102);
ΔλTi＝kλ×ΔTFi+bF (2)
in the formula,
ΔλTWi-least squares on-line with Δ TFiCorresponding delta lambdaTi，i＝0，1，2，3，4，5，6，nm；
kλ-a strain sensitivity coefficient;
bF-the fiber grating strain gauge sensor (102) on the least squares line is measured on the platinum resistance thermometer 30Measuring the change quantity of the central wavelength at the temperature of 0 ℃ in the constant-temperature water tank (20), namely nm;
step 006: the environmental temperature value T recorded by the fiber bragg grating temperature type sensor (103) in the step 005 at each level of load measuring pointFijSubstituting the formula (2) into the formula (2), wherein i is 1,2, … …, 10, j is 1,2,3, … …, 6, and calculating the central wavelength variation delta lambda of the fiber grating strain gauge sensor (102) caused by the environmental temperature change at each stage of load measuring pointTijWherein i is 1,2, … …, 10, j is 1,2,3, … …, 6;
calculating the central wavelength value lambda measured by the fiber grating strain sensor (102) in the 3-time cyclic measurement process of each load measurement point according to the formula (3)ijWith an initial wavelength value λ0Average value of difference:
in the formula,
Δλi-average value of difference between central wavelength value and initial wavelength value, nm, measured by fiber grating strain gauge sensor (102) on fiber grating strain gauge (10) in 3 times of cyclic measurement process of i-th level load measurement point; wherein i is 1,2,3, … …, 10;
λijthe central wavelength value, nm, measured by the fiber grating strain gauge sensor (102) on the fiber grating strain gauge (10) in the jth measurement process of the ith-level load measurement point; wherein i is 1,2,3, … …, 10; j ═ 1,2,3, … …, m;
ΔλTij-the amount of change in the center wavelength, nm, measured by the fiber grating strain gauge sensor (102) due to changes in ambient temperature; wherein, i is 1,2, … …, 10, j is 1,2,3, … …, 6;
m is the number of times of measuring the loading and unloading strokes, and m is 6;
the average value delta lambda of the difference value between the central wavelength value and the initial wavelength value measured by the fiber grating strain type sensor (102) on the fiber grating strain type steel bar meter (10)iAs a self-variationAmount, as average value F of the load applied by the standard loading device (70)iAs a dependent variable, performing least square method linear fitting according to a formula (5), and calculating to obtain a load measurement value F of the fiber grating type reinforcing steel bar meter (10)Wi：
Wherein,
in the formula,
FPi-the standard load applied by each level of load measuring point during the loading stroke of the standard load device (70), kN;
FMi-standard load applied by each level of load measuring point during load-down stroke of the standard load device (70), kN;
FWi＝k×Δλi+C (5)
in the formula:
FWi-on the least squares line with Δ λiCorresponding FiNm, wherein i is 0, 1,2,3, 4, 5, 6
k is the sensitivity coefficient of the fiber grating strain type steel bar meter (10), kN/nm;
c is the load measurement value kN of the fiber bragg grating strain type reinforcing steel bar meter (10) in a free state;
step 007: calculating the load measurement value F of the fiber grating strain type steel bar meter (10) according to the formula (6)WiAverage value F of load applied by standard load device (70)iMaximum error delta betweenL：
In the formula,
FFS-a full scale load value, kN, of the fiber grating strain gauge rebar gauge (10).
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