CN114295097A - High-temperature dynamic strain calibration device based on resonant beam - Google Patents
High-temperature dynamic strain calibration device based on resonant beam Download PDFInfo
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Abstract
The invention relates to a high-temperature dynamic strain calibration device based on a resonant beam, and belongs to the field of metering test. The device disclosed by the invention comprises a vibration table, a power amplifier, a signal generator, a resonance beam, a differential laser vibration meter, reflective micro-beads, a heating furnace, a temperature control system, a temperature sensor, a test temperature indicator, a heat insulation connecting mechanism, a water circulation cooling system, a numerical control micro-displacement mechanism, a strain signal conditioner, a data acquisition system and a data processing system. The invention provides a standard dynamic strain excitation source for calibrating dynamic parameters of a high-temperature strain sensor.
Description
Technical Field
The invention relates to a high-temperature dynamic strain calibration device based on a resonant beam, in particular to a device for generating high-frequency large-amplitude dynamic strain and dynamically calibrating a strain gauge under a high-temperature condition, and belongs to the field of measurement and testing.
Background
High temperature dynamic strain testing is an important tool for structural design, manufacturing and health monitoring. For example, in specific environments such as temperature strain of blades of aero-engines, the change range of strain is fast, and the measurement result has errors due to the cross sensitivity between the temperature and the strain, so that accurate and reliable dynamic strain measurement data have important significance for judging the reliability of the structure, determining the resonance point of the structure and detecting the damage of the structure under the high-temperature condition. In order to ensure the accuracy of the high-temperature test of the strain gauge and reduce the measurement error of the strain gauge, the problem which needs to be solved urgently is solved, and high-temperature dynamic calibration needs to be carried out on the strain gauge.
Currently, a dynamic strain calibration device is generally used, which can calibrate the sensitivity coefficient of the strain gauge and the error thereof. However, no mature method and device for calibrating the high temperature dynamic strain of strain gauges exist. The invention is characterized in that under the condition of high temperature, the high-frequency large-amplitude sinusoidal strain is generated by adopting a mode of a resonance beam, and the scanning measurement of the displacement of the beam in the vertical direction is realized by adopting the combination of a laser interferometer and a micro-displacement platform, so as to calculate the strain value of each point on the resonance beam.
Disclosure of Invention
The invention aims to provide a resonance type high-temperature dynamic strain calibration method and a device; the invention aims to realize the dynamic calibration of the strain gauge with high frequency and large amplitude under the high-temperature condition.
The purpose of the invention is realized by the following technical scheme.
The invention discloses a dynamic strain tracing calibration method, which comprises the following steps:
step one, opening a water circulation cooling system, a heating furnace and a heating furnace temperature control system to ensure that the water circulation cooling system works normally, heating the resonance beam to a calibration temperature, and stabilizing for more than 15 minutes.
And step two, determining the first-order natural frequency of the rectangular constant-section resonant beam. Calculating the first-order natural frequency f of the resonant beam according to the material and the structural size of the resonant beam0. Randomly selecting a measuring point at the end point close to the surface of the resonant beam, wherein the transverse coordinate of the measuring point is xL(ii) a The amplitude of this point is measured by a laser interferometer. With f0Centering, adjusting the vibration frequency f of the vibration exciter, and observing the output of the laser interferometerWhen the peak value is maximum, the vibration frequency f is the actual first-order natural frequency f of the resonant beam1。
Step three, adjusting the first-order resonant frequency f of the vibration exciter2And an amplitude; enabling the resonance beam to be in a stable vibration state through the vibration exciter; the vibration frequency f2At f1(1 ± 0.5%) at a certain point in the frequency range.
Step four, taking a certain position close to the end point of the surface of the resonance beam as a measuring point, wherein the transverse coordinate of the measuring point is xL(ii) a And measuring the differential dynamic displacement between the free end measuring point and the fixed end in the vertical direction by using a laser interferometer to obtain a relation curve W (t) of the displacement of the point beam in the vertical direction and time. The measurement requirements are as follows: sampling frequency is more than 100 times of vibration frequency, measuring time is more than 10 vibration cycles, M displacement data are obtained by continuous acquisition, and a relation curve of displacement and time is obtained by performing sine fitting on the M displacement data:
W(t)＝ASin(2πf2t+θ) (1)
wherein W (t) is the differential displacement of the measuring point in the vertical direction relative to the fixed end at the time t, A is the amplitude coefficient, t is the time, f2θ is the vibration frequency and θ is the vibration phase.
And fifthly, aiming at the rectangular beam with the equal section, the central inertia main shaft of the structure is in the same plane, the external load also acts on the plane, the resonant beam vibrates in the plane in the vertical direction, and the resonant beam mainly deforms into bending deformation.
In the first-order resonance frequency state, the first-order mode curve is as follows:
Y(x,T)＝A[cosβx-chβx-0.734(sinβx-shβx)] (2)
wherein A is amplitude coefficient, L is length of the resonance beam, x is abscissa of surface of the resonance beam, and KTA temperature coefficient for a calibration temperature; beta is the resonance coefficient.
β＝1.875/(LKT) (3)
Step six, setting the differential laser vibration meter at x1At a pointSubstituting the measured value Y (x) into (1) to determine the amplitude coefficient A.
In the first-order resonance state, the differential laser vibration meter is in xLMeasured vibration amplitude of the strain beam is YL. Then, according to the resonance theory, the parameter a can be determined as:
step seven, converting the vibration mode curve (2) into a strain curve:
where h is half the thickness of the beam and d2Y(x)/dx2Denotes the second derivative of y (x) with respect to x.
Step eight, standard strain of the mounting point of the resonant beam strain gauge is as follows:
ε(xs,t,T)＝AhKTβ2[cosβxs+chβxs-0.734(sinβxs-shβxs)]sin(2πf2t+θ) (5)
wherein XsThe abscissa of the central point of the mounting area of the strain gauge to be calibrated is used, and the strain gauge to be calibrated is mounted at any position close to the root part of the resonance beam; θ is the initial phase of the resonant beam vibration.
And step nine, the calibrated strain gauge is arranged at a calibration point of the resonant beam, the strain signal conditioner demodulates the strain gauge signal, the data acquisition system synchronously acquires the output signals of the differential laser vibration meter and the strain signal conditioner, and the data processing system compares the standard strain value with the output of the calibrated strain measurement system to realize dynamic calibration of the strain gauge.
The invention discloses a high-temperature dynamic strain tracing calibration method which is realized based on a resonance type high-temperature dynamic strain calibration device. The device comprises: the device comprises a vibration loading module, a temperature loading module, a verification temperature module, a heat insulation cooling module, a laser interference module, a calibrated strain gauge 17, a resonance beam 4, a data acquisition system 10 and a data processing system 11; the resonance beam 4 is arranged on the vibration table 1 through the connecting rod 3 to form a dynamic strain excitation system, and the differential laser vibration meter 8 is connected with the data acquisition system 10 and the data processing system 11 to be used as a standard dynamic strain measurement system; on the basis of this, the strain gauge 17 to be calibrated is mounted on a calibration device, and dynamic calibration of the strain gauge is realized by comparing the standard dynamic strain with the output of the strain gauge.
The vibration loading module comprises a vibration table 1, a connecting rod 3, a power amplifier 18 and a signal generator 19.
The temperature loading module comprises a resistance heating furnace 5, a heating temperature control system 12, a temperature sensor 20 and a test observation window 21.
The laser interference module comprises a differential laser vibration meter 8, a high-precision numerical control micro-displacement platform 6, an interferometer support 7 and reflective micro-beads 15.
The heat insulation cooling module comprises a ceramic gasket 2, a connecting rod 3 and a water circulation cooling system 14. Wherein, the water circulation cooling system comprises a water tank 12, a water temperature thermometer 23, a water pump 24 and cooling water 25.
The certification temperature module includes a temperature sensor 16 and a test temperature indicator 13.
Preferably, the resonant dynamic strain calibration device comprises a series of resonant beams of different materials and structural dimensions, each resonant beam having a different first order resonant frequency. The resonance beam is a rectangular beam with equal cross section, and the resonance beam adopts a symmetrical structure so as to ensure the balance of vibration load.
Preferably, the connecting rod has the length of 100mm and the diameter of 50 mm; the connecting rod can also be 100mm long and more than 50mm in diameter; the connecting rod can also be a connecting rod with the length less than 100mm and the diameter of 50 mm; or other link structure dimensions having a first order mode greater than 1000Hz using a simplified beam structure mode analysis (see schematic figure 4).
Preferably, the heating device may be a resistance heating type or an electromagnetic heating type.
Preferably, the temperature sensor in the assay temperature module may be a contact temperature sensor, a non-contact temperature sensor, or another type of thermometer or thermometer.
Preferably, the differential laser vibrometer used in the dynamic displacement measurement system may be a laser vibrometer, a laser interferometer, a differential laser interferometer, or a laser displacement sensor. The dynamic displacement measurement system can be arranged on a high-accuracy displacement mechanism to realize scanning measurement of displacement along the upper surface of the resonant beam.
The invention discloses a resonant high-temperature dynamic strain calibration device, which comprises the following working steps:
the method comprises the following steps: the connecting rod 3 is selected. According to the modal analysis of the beam structure, referring to the schematic diagram 5, when the length of the connecting rod is 100mm and the diameter is 50mm, the first-order mode of the connecting rod is 1004 Hz. Therefore, we can choose: a connecting rod with the length of 100mm and the diameter of more than 50 mm; a connecting rod with the length of less than 100mm and the diameter of 50mm can also be selected; or selecting other connecting rod structure sizes with the first-order mode larger than 1000Hz obtained by using beam-rod mode analysis.
And step two, selecting the beam 4 with the uniform cross section for testing. According to the schematic view of fig. 1, the resonance beam 4 is firmly mounted on the vibration table 1. The strain gauge 16 to be calibrated is attached to the lower surface of the resonant beam 4, and the strain signal conditioner 9 is connected to the strain gauge 17 to be calibrated. The differential laser vibration meter 8 is erected on the high-precision numerical control micro-displacement platform 6 through the interferometer support 7, and laser beams are adjusted to scan and measure the upper surface of the resonant beam 2.
And step three, connecting a water circulation cooling system according to a schematic diagram 4. The connection is ensured to be firm, the position is proper, and the sealing safety and reliability of the water circulation cooling system are ensured.
And step four, placing a resistance heating system. According to the schematic diagram of fig. 3, when the heating system is placed, it is ensured that the light beam of the differential laser vibration meter 8 can pass through the observation window 21, and that the moving range of the differential laser vibration meter 8 along with the high-precision numerical control displacement platform 6 is within the range of the observation window 21.
And step five, opening the water circulation cooling system to ensure that the water circulation work of the water circulation cooling system is normal.
And step six, opening the resistance-type heating furnace 5 and the heating temperature control system 12, setting the temperature of the heating target to be tested, and starting the heating device. The resonant beam 4 is heated to the calibration temperature and stabilized for more than 15 minutes. The temperature of water in the water tank is ensured not to exceed 70 ℃, and ice is added for cooling treatment if necessary.
And step seven, starting the power amplifier 18, controlling the vibration frequency and the waveform of the vibration table 1 by using the signal generator 19, and determining the actual first-order natural frequency of the rectangular constant-section resonant beam.
Step eight, adjusting the frequency of the signal generator 19, and enabling the resonance beam 4 to be in a stable vibration state through the vibration exciter; the first order resonance frequency f2At f1(1 + -0.5%) at a point in the actual first-order natural frequency range.
Step nine, taking a certain position close to the end point of the surface of the resonant beam 4 as a measuring point, wherein the transverse coordinate of the measuring point is xL(ii) a The differential dynamic displacement Y of the free end measuring point and the fixed end in the vertical direction is measured by the differential laser vibration meter 8LFrom this deflection value, the standard strain ε (x) of the mounting point of the strain gauge 17 on the resonance beam 4 can be obtaineds,t,T)。
And step ten, adjusting the output current of the signal generator 19, and synchronously acquiring the outputs of the differential laser vibration meter 8 and the calibrated strain gauge 17. The differential dynamic displacement between the free end measuring point and the fixed end in the vertical direction is measured by the differential laser vibration meter 8, so that the different standard strain epsilon (x) of the mounting point of the strain gauge 17 on the resonant beam 4 can be obtained according to the deflection values,t,T)。
Step eleven, after all the test points are sequentially finished, respectively adjusting the output current and the output frequency of the signal generator to be 0, and turning off the power amplifier 18; and turning off the differential laser vibrometer 8, the data acquisition system 10 and the data processing system 11.
And step twelve, adjusting the set temperature of the heating temperature control system 12 to room temperature.
And step thirteen, when the beam 4 to be resonated and the resistance-type heating furnace 5 are cooled to below 50 ℃, closing the test temperature indicator 13, the water circulation cooling system, the resistance-type heating furnace 5 and the heating temperature control system 12.
Has the advantages that:
1. the invention discloses a resonance type high-temperature dynamic strain calibration method and device, and provides a high-temperature dynamic strain calibration method based on a resonance beam structure aiming at a strain gauge, so that high-frequency large-amplitude high-temperature dynamic strain calibration is realized.
2. The invention discloses a resonant high-temperature dynamic strain calibration device, which is suitable for tracing the dynamic strain of a resonant beam in any structural form by using laser interferometry as a means under a high-temperature condition, fitting a deformation curve in the vertical direction of the surface of the beam and then calculating the second derivative of the fitted curve.
Drawings
FIG. 1 is a schematic structural view of the structure of the present invention.
Fig. 2 is a schematic structural view of a resonant beam used in the case of the present invention, in which fig. 2(a) is a front view and fig. 2(b) is a sectional view a-a.
Fig. 3 is a schematic diagram of a temperature loading module used in the case of the present invention.
Fig. 4 is a schematic view of an insulated cooling module used in the case of the present invention.
Fig. 5 is a result of modal analysis of a beam structure used in the case of the present invention.
Fig. 6 is a mechanical design drawing of the connecting rod 3 used in the case of the present invention.
Wherein, 1, a vibration table; 2-ceramic spacer; 3, connecting rods; 4-resonant beam; 5-resistance heating mechanism; 6-high precision numerical control micro-displacement platform; 7-interferometer holder; 8-differential laser vibrometer; 9-strain signal conditioner; 10-a data acquisition system-; 11-a data processing system; 12-heating temperature control system; 13-testing a temperature indicator; 14-water circulation cooling system; 15-reflective microbeads; 16-a strain gauge to be tested; 17-temperature sensor-; 18-a power amplifier; 19-a signal generator; 20-a temperature sensor; 21-test observation window; 22-a water tank; 23-water temperature thermometer; 24-a water pump; 25-cooling water.
Detailed Description
The invention is further illustrated by the following figures and examples.
Example 1:
as shown in fig. 1, the resonance type dynamic strain calibration device disclosed in this embodiment includes a vibration table 1, a ceramic spacer 2, a connecting rod 3, a resonance beam 4, a resistance heating type heating mechanism 5, a high-precision numerical control micro-displacement platform 6, an interferometer support 7, and a differential laser vibrometer 8; a strain signal conditioner 9; a data acquisition system 10; a data processing system 11; heating the temperature control system 12; a test temperature indicator 13; a water circulation cooling system 14; the device comprises a reflective microbead 15, a temperature sensor 16, a strain gauge 17 to be tested and a power amplifier 18; a signal generator 19, a temperature sensor 20; the observation window 21 is tested. A water tank 22; a water temperature thermometer 23; a water pump 24; cooling water 25.
The resonance beam 4 is arranged on the vibration excitation table 1 through the connecting rod 3, and the installation point is arranged at the center of the resonance beam 4 to form a dynamic strain generating system; the resistance heating type heating mechanism 3, the heating furnace temperature control system 8 and the temperature sensor 12 form a high-temperature test environment; the differential laser vibration meter 8, the data acquisition system 10 and the data processing system 11 are used as a standard dynamic strain measurement system; the reflective micro-beads 15 are adhered to the end part of the upper surface of the resonant beam 4; two beams of measuring laser emitted by the differential laser vibration meter 8 irradiate the reflective micro-beads 15, and the reflected light is received by the differential laser vibration meter 8, so that the displacement of the point II relative to the point I is measured; the strain gauge 17 to be calibrated is mounted on the upper surface of the resonant beam 2, and the standard strain of the region where the strain gauge to be calibrated is compared with the strain measured by the strain gauge to realize dynamic strain calibration.
The dynamic strain tracing calibration method disclosed by the embodiment specifically comprises the following implementation steps:
step one, opening a water circulation cooling system, a heating furnace 5 and a heating furnace temperature control system to ensure that the water circulation cooling system works normally, heating the resonance beam 4 to a calibration temperature, and stabilizing for more than 15 minutes.
And step two, selecting a resonance beam with an equal cross section for work, and installing and connecting according to the figure 1. The first-order natural frequency of the resonance beam 4 with the uniform section is 1000Hz, and the specific structure dimension refers to the attached figure 2 of the specification. I.e. a length of 110mm, a thickness of 15mm and a natural frequency of1000Hz, the material is the constant section resonance beam 4 of steel, and the constant section resonance beam 4 is firmly installed on the vibration table 1. The strain-to-be-calibrated gauge 17 is attached to the upper surface of the resonant beam 4, and the strain signal conditioner 9 is connected to the strain-to-be-calibrated gauge 17. Erecting a differential laser vibration meter 8 on a high-precision numerical control micro-displacement platform 6 through an interferometer support 7, and adjusting laser beams so that the laser beams can scan and measure the free-section reflective microspheres on the upper surface of the resonant beam 4 through a test observation window 21 and the laser beam measuring point xLThe coordinates are 105 mm. Mounting a calibration strain gauge 17 on the upper surface x of the constant-section resonant beam 2sA, xsThe coordinate is at 15 mm.
And step three, determining the first-order natural frequency of the rectangular constant-section resonant beam. Randomly selecting a measuring point at the end point close to the surface of the resonant beam, wherein the transverse coordinate of the measuring point is xL(ii) a The amplitude of the measuring point is YL(ii) a Adjusting the vibration frequency f of the vibration exciter and observing the differential amplitude Y of the measuring pointLWhen a differential amplitude Y is presentLWhen it becomes suddenly larger, it is the actual first-order natural frequency f of the resonant beam1。
And step four, starting the vibration exciter 1 to enable the constant-section resonant beam 2 to be in a stable resonance coordination state, wherein the resonance coordination frequency is 1000 Hz.
Step five, taking a certain position close to the end point of the surface of the resonance beam as a measuring point, wherein the transverse coordinate of the measuring point is xL(ii) a And opening the differential laser vibration meter 4, adjusting the light path, measuring the differential vibration state of the glass beads 15 in the direction vertical to the upper surface of the constant-section resonant beam 2, setting the measurement frequency to be 2MHz, and continuously measuring. The data acquisition system 10 synchronously acquires output signals of the differential laser vibration meter 8 and the strain signal conditioner 9, and data analysis is performed through the data processing system 11. And measuring the differential dynamic displacement of the free end measuring point and the fixed end in the vertical direction by using the differential laser vibration meter 4 to obtain a relation curve W (t) of the displacement of the point beam in the vertical direction and time.
And sixthly, aiming at the rectangular constant-section beam, the central inertia main shaft of the structure is in the same plane, the external load also acts on the plane, the constant-section resonant beam vibrates in the plane in the vertical direction, and the constant-section resonant beam mainly deforms into bending deformation. In the first-order resonance frequency state, the first-order mode curve is as follows: the maximum value Y of the vibration of the measuring point is recorded.
The resonance coefficient β is:
β＝1.875/(0.11K600℃) (6)
substituting the resonance coefficient beta into the vibration mode curve of the surface of the constant-section resonance beam:
Y＝A{[cos(16.8984x)-ch(16.8984x)-0.734·[sin(16.8984x)-sh(16.8984x)]} (7)
wherein KTThe values in (1) are as follows:
TABLE 1KTTemperature coefficient of (steel)
| Calibration temperature/(° c) | KT(Steel) |
| 100 | 1.00104 |
| 200 | 1.00243 |
| 300 | 1.003892 |
| 400 | 1.005434 |
| 500 | 1.007056 |
| 600 | 1.008700 |
| … | … |
Step seven, the obtained coordinates (0.105, Y) of the measuring pointL) And substituting the value into (1) to obtain the amplitude coefficient A.
Step eight, converting the vibration mode curve into a strain curve:
step nine, standard strain of the mounting point of the constant-section resonant beam strain gauge is as follows:
ε(xs,t,600℃)＝AhK600℃β2[cosβxs+chβxs-0.734(sinβxs-shβxs)]sin(2000πt+θ) (9)
the standard strain is a function of the ordinate Y of the measuring point, and the value of the ordinate reflects the excitation strength of the vibration excitation source. When Y isLThe amplitude factor A and the standard strain ε (t) (0.015) are shown below for different values:
TABLE 2600 deg.C vibration excitation x corresponding to different excitation intensities Y2Standard strain at 15mm
| YL/μm | A/10-4 | ε(t)(0.015) |
| 263.5 | -1.4226 | ε(t)＝-0.0005sin(2000πt) |
| 316.0 | -1.7061 | ε(t)＝-0.0006sin(2000πt) |
| 368.5 | -1.9895 | ε(t)＝-0.0007sin(2000πt) |
| 421.0 | -2.2730 | ε(t)＝-0.0008sin(2000πt) |
| 474.0 | -2.5591 | ε(t)＝-0.0009sin(2000πt) |
| 526.5 | -2.8426 | ε(t)＝-0.001sin(2000πt) |
| … | … | … |
Step ten, installing the calibrated strain gauge 17 at a calibration point of the constant-section resonant beam 4, demodulating a signal of the strain gauge 17 by using the strain signal conditioner 9, synchronously acquiring output signals of the differential laser vibration meter 4 and the strain signal conditioner 5 by using the data acquisition system 6, and comparing a standard strain value with the output of the calibrated strain measurement system by using the data processing system 11 to realize dynamic calibration of the calibrated strain gauge 17.
The operation working process of the device is as follows:
the method comprises the following steps: the connecting rod 3 is selected. According to the structural modal analysis of the beam and the rod, referring to the schematic diagram 5, when the length of the connecting rod is 100mm and the diameter is 50mm, the first-order mode of the connecting rod is 1004Hz, so that the connecting rod can be selected from the following modes: a connecting rod with the length of 100mm and the diameter of more than 50 mm; a connecting rod with the length of less than 100mm and the diameter of 50mm can also be selected; or selecting other connecting rod structure sizes with the first-order mode larger than 1000Hz obtained by using beam-rod mode analysis. A connecting rod with the length of 100mm and the diameter of 60mm is selected. The specific mechanical structure is shown in figure 6.
And step two, selecting a first-order constant-section beam 4 with the natural frequency of 1000Hz, and referring to the attached figure 2 of the specification for the specific structure size. According to the schematic diagram 1, a constant-section resonant beam 4 is firmly mounted on a vibration table 1 through a connecting rod 3. The strain-to-be-calibrated gauge 17 is attached to the upper surface of the constant cross-section resonant beam 4, and the strain signal conditioner 9 is connected to the strain-to-be-calibrated gauge 17. The differential laser vibration meter 8 is erected on the high-precision numerical control micro-displacement platform 6 through the interferometer support 7, and laser beams are adjusted to scan and measure the upper surface of the constant-section resonant beam 2.
And step three, connecting a water circulation cooling system according to a schematic diagram 4. The connection is ensured to be firm, the position is proper, and the sealing safety and reliability of the water circulation cooling system are ensured.
And step four, placing the position of the resistance heating system. The position of the resistance heating system is adjusted according to the schematic diagram 3. And the light beam of the differential laser vibration meter 8 can pass through the observation window 21, and the moving range of the differential laser vibration meter 8 along with the high-precision numerical control displacement platform 6 is ensured to be within the range of the observation window 21.
And step five, opening the water circulation cooling system to ensure that the water circulation cooling system works normally.
And step six, opening the resistance-type heating furnace 5 and the heating temperature control system 12, setting the temperature of the heating target to be tested, and starting the heating device. The constant section resonant beam 4 is heated to a calibration temperature of 600 ℃ and stabilized for more than 15 minutes. The temperature of water in the water tank is ensured not to exceed 70 ℃, and ice is added for cooling treatment if necessary.
And step seven, starting the power amplifier 18, controlling the vibration frequency and the waveform of the vibration table 1 by using the signal generator 19, and determining the first-order natural frequency of the rectangular constant-section resonant beam.
Step eight, adjusting the frequency of the signal generator 19, and enabling the constant-section resonant beam 4 to be in a stable vibration state through the power amplifier 18, the vibration table 1 and the connecting rod 3; the resonant frequency f2At f1(1 ± 0.5%) at a certain point in the frequency range.
Step nine, taking a certain position close to the end point of the surface of the constant-section resonant beam 4 as a measuring point, wherein the transverse coordinate of the measuring point is xL(ii) a The differential dynamic displacement Y of the free end measuring point and the fixed end in the vertical direction is measured by the differential laser vibration meter 8LFrom this deflection value YLThe standard strain epsilon (x) of the mounting point of the strain gauge 17 on the constant-section resonant beam 4 can be obtaineds,t,T)。
And step ten, adjusting the output current of the signal generator 19, and simultaneously collecting the outputs of the differential laser vibration meter 8 and the calibrated strain gauge 17. The differential dynamic displacement Y of the free end measuring point and the fixed end in the vertical direction is measured by the differential laser vibration meter 8LAnd therefore, different standard strains of the mounting points of the strain gauges 16 on the constant-section resonant beam 4 can be obtained according to the deflection value.
Step eleven, after all the test points are sequentially completed, the output current of the signal generator 9 is slowly adjusted to be 0, then the output frequency of the signal generator 19 is adjusted to be 0, and the power amplifier 18 is turned off.
And step twelve, closing the differential laser vibrometer 8, the data acquisition system 10 and the data processing system 11 in sequence.
And step thirteen, adjusting the temperature of the resistance type heating furnace 5 to the room temperature.
And step fourteen, when the constant section resonant beam 4 and the resistance type heating furnace 5 are cooled to below 50 ℃, the test temperature indicator 13 and the water circulation cooling system 14 are closed.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention. The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. High temperature developments calibration device that traces to source based on resonance beam, its characterized in that: the method comprises the following steps: the device comprises a vibration exciter, a resonance beam, a heat insulation cooling module, a heating furnace and a differential laser vibration meter; the resonant beam is connected with the vibrating table through a connecting rod, so that the aim of same-frequency resonance is fulfilled; the resonance beam is arranged in the heating furnace; the heating furnace is provided with a measuring hole, and the laser vibration meter realizes real-time dynamic measurement and acquisition of the differential displacement of the resonance beam through the measuring hole; the heat insulation cooling module comprises a ceramic gasket, a connecting rod and a water circulation cooling system; the ceramic gasket is arranged between the connecting rod and the vibrating table; the connecting rod is of a hollow structure; and cooling water in the water circulation cooling system flows out through the connecting rod to cool the connecting rod so as to isolate the temperature of the resonant beam from the temperature of the vibration exciter.
2. The apparatus of claim 1, wherein: further comprising: the device comprises a test temperature indicator, a heating furnace and a heating furnace temperature control system, wherein the test temperature indicator is arranged on the resonant beam, the heating furnace and the heating furnace temperature control system are mainly used for heating and maintaining the test temperature of the resonant beam, and the test temperature indicator is mainly used for monitoring the actual temperature of the resonant beam.
3. The apparatus of claim 1, wherein: according to the simplified beam-rod structure modal analysis, the first-order mode of the connecting rod with the height of 100mm and the diameter of 50mm is 1004Hz, so that in the mechanical design of the connecting rod, the connecting rod with the height of 100mm and the diameter of 60mm is adopted.
4. The connecting rod of claim 2, wherein: the connecting rod can be selected from the following components: a connecting rod with the length of 100mm and the diameter of more than 50 mm; a connecting rod with the length of less than 100mm and the diameter of 50mm can also be selected; or selecting other connecting rod structure sizes with a first-order mode larger than 1000Hz obtained by using the mode analysis of the simplified beam structure.
5. The method for high-temperature dynamic strain tracing calibration by using the device of claim 1, wherein the method comprises the following steps: the method comprises the following steps:
opening a water circulation cooling system, a heating furnace and a heating furnace temperature control system to ensure that the water circulation cooling system works normally, heating a resonance beam to a calibration temperature, and stabilizing for more than 15 minutes;
step two, determining the first-order natural frequency f of the rectangular constant-section resonant beam1；
Randomly selecting a measuring point at the end point close to the surface of the resonant beam, wherein the transverse coordinate of the measuring point is xL(ii) a The amplitude of the measuring point is YL(ii) a Adjusting the vibration frequency f of the vibration exciter and observing the differential amplitude Y of the measuring pointLWhen a differential amplitude Y is presentLWhen it becomes suddenly larger, it is the actual first-order natural frequency f of the resonant beam1；
Step three, at the first-order resonant frequency f of the vibration exciter2Under the condition, adjusting the amplitude of the vibration exciter and collecting the amplitude of the corresponding resonant beam;
the first order harmonic frequency f2At f1(1 +/-0.5%); determining a first order harmonic frequency f2Then adjusting the excitation of the vibration exciter, and acquiring the differential amplitude Y of the corresponding resonance beam under the same frequency and different excitationsL；
Step four, obtaining the differential dynamic amplitude of the fixed end of the resonance beam and the measuring point according to the measurement, and obtaining the relation curve of the amplitude of the measuring point in the vertical direction and the time:
Y(t)＝ASin(2πf2t+θ) (1)
wherein,y (t) is the differential displacement of the measuring point in the vertical direction relative to the fixed end at time t, A is the amplitude coefficient, t is the time, f2Is a first order resonant frequency, theta is a vibration phase;
fifthly, the central inertia main shafts of the rectangular constant-section resonance beams are in the same plane, external loads also act on the plane, the resonance beams vibrate in the vertical direction in the plane, and the resonance beams mainly deform into bending deformation;
under the state of first-order resonance frequency, the first-order vibration mode curve of the resonance beam is as follows:
Y(x,T)＝A[cosβx-chβx-0.734(sinβx-shβx)] (2)
wherein A is amplitude coefficient, L is length of the resonant beam, x is transverse coordinate of the resonant beam, and KTA temperature coefficient for a calibration temperature; beta is a resonance coefficient; t is a calibration temperature;
β＝1.875/(LKT) (3)
by taking the measured value Y at the measuring pointLSubstituting formula (2) and determining an amplitude coefficient A;
under the first-order resonance state, according to the resonance theory and the amplitude obtained in the third step, determining the parameter A as follows:
wherein xLThe horizontal coordinate of the position of the probe II of the laser vibrometer is shown;
step six, converting the vibration mode curve (2) into a strain curve:
where h is half the thickness of the beam and d2Y(x)/dx2Denotes the second derivative of y (x) with respect to x;
step seven, the standard strain of the mounting point of the strain gauge is calibrated on the resonance beam:
ε(xs,t,T)＝AhKTβ2[cosβxs+chβxs-0.734(sinβxs-shβxs)]sin(2πf2t+θ) (6)
wherein xsThe horizontal coordinate of the central point of the installation area of the strain gauge to be calibrated; the calibrated strain gauge is arranged at any position close to the root of the resonance beam; theta is the initial phase of the vibration of the resonance beam;
step eight, outputting the strain of the strain gauge to be calibrated and the standard strain epsilon (x)sT, T) to realize dynamic calibration of the strain gauge.
6. The method of claim 5, wherein: the method for rapidly determining the first-order natural frequency in the step two comprises the following steps: calculating the first-order natural frequency f of the resonant beam according to the material and the structural size of the resonant beam0(ii) a With f0Adjusting the vibration frequency f of the vibration exciter as the center, observing the amplitude of the measuring point of the laser vibrometer, and obtaining the actual first-order natural frequency f of the resonant beam when the amplitude is suddenly increased1。
7. The apparatus of claim 1, wherein the differential laser vibrometer used in the dynamic displacement measurement system is a laser vibrometer, a laser interferometer, a differential laser interferometer, or a laser displacement sensor.
8. The apparatus of claim 2, wherein: the heating device may be a resistance heating type or an electromagnetic heating type.
9. A high temperature dynamic strain calibration device as defined in claim 2, wherein: the temperature sensor connected in the test temperature indicator can be a contact temperature sensor, a non-contact temperature sensor, or other thermometers or thermometers.
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