High-temperature strain gauge measurement error correction method and device

Abstract

The application belongs to the technical field of flight test, and particularly relates to a high-temperature strain gauge measurement error correction method and system. The method comprises the following steps: S1, obtaining a first strain variable of a specified component in aircraft test through a high-temperature strain gauge; S2, obtaining a measuring point temperature and a temperature rise rate of the specified component based on a thermocouple arranged on the specified component; S3, determining a second strain variable caused by temperature according to the measuring point temperature and the temperature rise rate in a preset interpolation table, wherein the interpolation table gives the relationship between the strain variable and the temperature under different temperature rise rates; and S4, subtracting the second strain variable from the first strain variable to obtain a third strain variable of the specified component caused by load. The application can accurately calculate the strain of the thermal structure of the aircraft under high-temperature conditions, and provide benchmark data for heat protection and heat transfer calculation of key components on the full flight envelope.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flight test, and particularly relates to a high-temperature strain gauge measurement error correction method and device. BACKGROUND

[0002] The thermal stress damage caused by aerodynamic heating is a prominent problem in the heat protection design of a hypersonic vehicle. Under the action of aerodynamic heating, a hypersonic vehicle structure will generate a large thermal stress, and the heated structure will produce plastic deformation or even damage due to thermal stress, which is the primary problem that must be solved in the structural design of a hypersonic vehicle. To solve the problem of plastic deformation or even damage of the material structure caused by thermal stress, stress field measurement and analysis of the structure are needed to obtain the thermal stress of the key parts and estimate the damage probability, which is very crucial for analyzing the success or failure and reliability of the heat protection design.

[0003] At present, some researches have been carried out on high-temperature strain measurement technology in China. Compared with normal-temperature strain measurement, temperature will affect the sensitivity, thermal output, zero drift and creep of the strain gauge, and an effective correction method needs to be adopted to ensure the accuracy of the measurement results. Generally, the thermal output curve correction method is adopted, that is, the steady-state thermal output of the high-temperature strain gauge is calibrated in the expected working temperature range of the high-temperature strain gauge, and a thermal output curve is drawn, and the thermal output value on the corresponding curve is found according to the actual measurement results for correction. This method, which does not consider the influence of temperature rise rate on the high-temperature strain, is called steady-state thermal output calibration. For a hypersonic vehicle, the structure is in a complex load environment during flight, and the temperature rise rate is also changing all the time. Therefore, the use of the traditional steady-state thermal output curve for error correction results in a large difference between the high-temperature strain measurement value and the predicted result. SUMMARY

[0004] To solve the above problems, the application provides a high-temperature strain gauge measurement error correction method and device to realize accurate measurement of high-temperature strain of a complex structure under a complex load environment during flight.

[0005] The first aspect of the application provides a high-temperature strain gauge measurement error correction method, mainly comprising:

[0006] Step S1: obtaining a first strain value of a specified component in an aircraft test by a high-temperature strain gauge;

[0007] Step S2: obtaining a measuring point temperature and a temperature rise rate of the specified component based on a thermocouple arranged on the specified component;

[0008] Step S3: determining a second strain value caused by temperature according to the measuring point temperature and the temperature rise rate in a preset interpolation table, wherein the relationship between the strain value and the temperature under different temperature rise rates is given in the interpolation table;

[0009] Step S4, subtracting the second strain from the first strain to obtain a third strain of the specified component caused by the load.

[0010] Preferably, before step S3, further comprising constructing the interpolation table by:

[0011] Step S31, placing a cantilever beam structure test piece horizontally, one end fixed and the other end as a cantilever end, the upper and lower surfaces of the cantilever end are provided with strain gauges and thermocouples, and a quartz lamp radiation heating array is fixed on the upper and lower sides of the cantilever beam structure test piece;

[0012] Step S32, heating the cantilever beam structure test piece at different temperature rise rates, recording the temperature and the strain value of the strain gauge feedback at the corresponding temperature at a set step to form the interpolation table.

[0013] Preferably, in step S31, the cantilever beam structure test piece is fixed on a vertical beam through a fixed support, and a water cooling channel is arranged on the fixed support.

[0014] Preferably, in step S31, the outer side of the quartz lamp radiation heating array away from the cantilever beam structure test piece is provided with a heat insulation plate.

[0015] Preferably, in step S32, the set step is 30-70℃.

[0016] Preferably, in step S32, the set step is 50℃.

[0017] Preferably, in step S32, the different temperature rise rates at least include 5℃ / s, 10℃ / s, 15℃ / s, 20℃ / s, and 25℃ / s.

[0018] Preferably, in step S3, determining the correction parameter comprises:

[0019] interpolating the second strain based on the interpolation table; or

[0020] fitting a three-dimensional graph between the temperature rise rate, temperature and strain based on the interpolation table, and calculating the second strain at a specified temperature rise rate and temperature according to the three-dimensional graph.

[0021] Preferably, after step S4, further comprising:

[0022] Step S5, determining the thermal stress and structural stress of the specified component according to the second strain and the third strain respectively, and evaluating the strength of the specified component or optimizing the specified component according to the thermal stress and structural stress.

[0023] The second aspect of the present application provides a high-temperature strain gauge measurement error correction device, mainly comprising:

[0024] The first strain measurement module is used to obtain the first strain of a specified component in aircraft testing using high-temperature strain gauges.

[0025] The measuring point temperature and temperature rise rate measurement module is used to obtain the measuring point temperature and temperature rise rate of the specified component based on the thermocouples arranged on the specified component.

[0026] The second strain calculation module is used to determine the second strain caused by temperature based on the temperature at the measuring point and the temperature rise rate in a preset interpolation table, wherein the interpolation table provides the relationship between the strain and temperature under different temperature rise rates.

[0027] The strain parameter correction module is used to subtract the second strain from the first strain to obtain the third strain of the specified component caused by the load.

[0028] This application can accurately calculate the strain of the thermal structure of an aircraft under high temperature conditions, provide benchmark data for the heat protection and heat transfer calculation of key components throughout the flight envelope, verify the thermo-mechanical coupled finite element analysis calculation technology, complete the comprehensive evaluation of heat transfer performance under severe flight conditions, and guide the design of thermal structures. Attached Figure Description

[0029] Figure 1 This is a flowchart of a preferred embodiment of the high-temperature strain gauge measurement error correction method of this application.

[0030] Figure 2 This is a schematic diagram of the transient thermal output calibration test device of this application.

[0031] Among them, 1-cantilever beam structure test piece, 2-strain gauge, 3-thermocouple, 4-quartz lamp radiation heating array, 5-fixed support, 6-vertical beam, 7-water cooling channel, 8-insulation board. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0033] The first aspect of the present application provides a high-temperature strain gauge measurement error correction method, as shown in the formula (1), the method comprises: Figure 1

[0034] Step S1, obtaining a first strain of a specified component in an aircraft test by a high-temperature strain gauge;

[0035] Step S2, obtaining a measuring point temperature and a temperature rise rate of the specified component based on a thermocouple arranged on the specified component;

[0036] Step S3, determining a second strain caused by temperature according to the measuring point temperature and the temperature rise rate in a preset interpolation table, wherein the interpolation table gives the relationship between the strain and the temperature under different temperature rise rates;

[0037] Step S4, subtracting the second strain from the first strain to obtain a third strain of the specified component caused by load.

[0038] The first strain ε1 obtained in step S1 of the present application mainly consists of two parts, one is a second strain ε2 caused by thermal stress, and the other is a third strain ε3 caused by mechanical loading. The relationship between the above three strains of the present application is described below by taking a cantilever beam as an example.

[0039] The cantilever beam is mechanically loaded in a normal temperature state, and the ratio of the elongation to the original length, i.e. the first strain ε1, is all the third strain ε3 caused by mechanical loading σ / E, and the second strain ε2 caused by thermal stress is 0, so the structural strain of the cantilever beam should be ε3=ε1-ε2=σ / E.

[0040] In the case of free heating and no mechanical load, the ratio of the elongation to the original length of the cantilever beam, i.e. the first strain ε1=α*ΔT, wherein α is the linear expansion coefficient, and the first strain ε1 is all the second strain ε2 caused by temperature change, so the structural strain of the cantilever beam should be ε3=ε1-ε2=0, and there is no stress in the cantilever beam at this time.

[0041] In the case of simultaneous force and heat loading, the first strain ε1 is caused by temperature change and mechanical load, i.e. ε1=α*ΔT+σ / E, and the ratio of the elongation to the original length caused by temperature change in the case of free heating is ε2=α*ΔT, so the structural strain of the cantilever beam at this time is ε3=ε1-ε2=σ / E.

[0042] If the ambient temperature of the cantilever beam is always changing, then the ratio of the elongation to the original length caused by temperature change in the case of free heating ε2 cannot reach the steady-state value α*ΔT in the transient temperature change process, i.e. ε2=α*ΔT*K, wherein K is a coefficient and its value is less than 1. ​

[0043] Step S3 of this application is to calculate the second strain ε2 by calibrating the thermal output of the strain gauge in the high-temperature strain measurement test.

[0044] In some alternative implementations, prior to step S3, the interpolation table is further constructed by:

[0045] Step S31: Place the cantilever beam structure test piece 1 horizontally, fix one end and the other end as the cantilever end. Strain gauges 2 and thermocouples 3 are provided on the upper and lower surfaces of the cantilever end. Quartz lamp radiation heating arrays 4 are fixed on the upper and lower sides of the cantilever beam structure test piece 1.

[0046] In some alternative embodiments, in step S31, the cantilever beam structure test piece 1 is fixed to the vertical beam 6 by a fixed support 5, and a water cooling channel 7 is provided on the fixed support 5.

[0047] In some alternative embodiments, in step S31, a heat insulation plate 8 is provided on the outer side of the quartz lamp radiation heating array 4 away from the cantilever beam structure test piece 1.

[0048] In step S31, the test apparatus is as follows: Figure 2 As shown, the cantilever beam test specimen 1 is placed horizontally and fixed to the vertical beam 6 by bolts on the fixed support 5. A densely arranged array of quartz lamps for radiant heating 4 is installed at a certain distance between the upper and lower surfaces of the test specimen 1, simultaneously heating both surfaces to create a dynamically changing high-temperature thermal test environment. A thermal isolation plate with a water-cooling channel 7 is located between the fixed support 5 of the cantilever beam test specimen 1 and the vertical beam 6. During the test, the flowing water carries away some of the heat, thus forming a temperature buffer zone between the test specimen 1 and the vertical beam 6. Furthermore, a high-temperature resistant ceramic heat shield 8 is installed on the outside of the quartz lamp radiant heating array 4 to thermally shield the high-temperature heating area, ensuring both heating effectiveness and the safety of the sensors and power supply lines. Symmetrical points on the upper and lower parts of the middle area of ​​the outer surface of the cantilever beam test specimen 1 are selected as measurement points, and high-temperature strain gauges 2 are attached thereon. A pair of thermocouples 3 are attached nearby to detect and control the temperature at the measurement points. The heating system adopts a transient thermal test control system, which can continuously, rapidly, and accurately control the temperature rise rate according to temperature changes.

[0049] Step S32: Heating the cantilever beam structure test piece 1 at different temperature rise rates, recording the temperature at the set step size and the strain value fed back by the strain gauge 2 at the corresponding temperature, and forming the interpolation table.

[0050] In some alternative implementations, in step S32, the set step size is 30-70°C.

[0051] In some alternative implementations, in step S32, the set step size is 50°C.

[0052] In some optional embodiments, in step S32, the different temperature rise rates at least include 5℃ / s, 10℃ / s, 15℃ / s, 20℃ / s, and 25℃ / s.

[0053] In step S32, by adjusting the temperature control system, the temperature rise rate is first set to 5℃ / s, the quartz lamp is heated, and the liquid in the water cooling channel starts to circulate. The thermocouple detects the temperature every 50℃, collects the corresponding strain gauge reading, and records the temperature value at this time. When the temperature of the cantilever beam reaches 900℃, the heating is stopped. The test piece is cooled to room temperature, the temperature control system is adjusted, the temperature rise rate is set to 10℃ / s, 15℃ / s, 20℃ / s, and 25℃ / s in turn, and the above steps are repeated to obtain the corresponding temperature-thermal output strain curve at five temperature rise rates.

[0054] The application controls the thermal output strain at different temperature states at different temperature rise rates by adjusting the temperature rise rate control command of the heating system, controlling the radiation heating thermal flux of the quartz lamp, and adjusting the heating temperature rise rate. The method is simple and feasible, and is suitable for the complex thermal load environment rapidly changed in the flight test of the aircraft.

[0055] In some optional embodiments, in step S3, determining the correction parameter includes:

[0056] obtaining the second strain value based on the interpolation table; or

[0057] fitting a three-dimensional graph between the temperature rise rate, the temperature, and the strain value based on the interpolation table, and calculating the second strain value at the specified temperature rise rate and the temperature according to the three-dimensional graph.

[0058] The embodiment can obtain the second strain value by twice interpolation, or can construct a three-dimensional graph in advance, thereby providing the thermal output correction at any temperature rise rate and temperature for high-temperature strain measurement.

[0059] In some optional embodiments, after step S4, the method further includes:

[0060] Step S5, determining the thermal stress and the structural stress of the specified component according to the second strain value and the third strain value respectively, and evaluating the strength of the specified component or optimizing the specified component according to the thermal stress and the structural stress.

[0061] The second aspect of the application provides a high-temperature strain gauge measurement error correction device corresponding to the above method, mainly including:

[0062] A first strain value measurement module is configured to obtain a first strain value of a specified component in an aircraft test by a high-temperature strain gauge.

[0063] a temperature and temperature rise rate measuring module, configured to obtain the temperature and temperature rise rate of the designated component based on thermocouples arranged on the designated component;

[0064] a second strain amount calculating module, configured to determine a second strain amount caused by temperature according to the temperature and the temperature rise rate in a preset interpolation table in which the relationship between strain amount and temperature under different temperature rise rates is given;

[0065] a strain parameter correcting module, configured to subtract the second strain amount from the first strain amount to obtain a third strain amount of the designated component caused by load.

[0066] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of correcting measurement errors of a high-temperature strain gauge, characterized by, The method comprises the following steps: Step S1, obtaining a first strain of a specified component in an aircraft test through a high-temperature strain gauge; Step S2, obtaining a measuring point temperature and a temperature rise rate of the specified component based on a thermocouple arranged on the specified component; Step S3, determining a second strain caused by temperature according to the measuring point temperature and the temperature rise rate in a preset interpolation table, wherein the interpolation table gives the relationship between the strain and the temperature under different temperature rise rates; Step S4, subtracting the second strain from the first strain to obtain a third strain of the specified component caused by load; Before step S3, the method further comprises the following steps of constructing the interpolation table: Step S31, horizontally placing a cantilever beam structure test piece (1), fixing one end and making the other end a cantilever end, arranging strain gauges (2) and thermocouples (3) on the upper and lower surfaces of the cantilever end, and fixing quartz lamp radiation heating arrays (4) on the upper and lower sides of the cantilever beam structure test piece (1); Step S32, heating the cantilever beam structure test piece (1) through different temperature rise rates, recording the temperature and the strain value fed back by the strain gauges (2) under the corresponding temperature at a set step to form the interpolation table.

2. The high-temperature strain gauge measurement error correction method of claim 1, wherein, In step S31, the cantilever beam structure test piece (1) is fixed on a vertical beam (6) through a fixed support (5), and a water cooling channel (7) is arranged on the fixed support (5).

3. The high-temperature strain gauge measurement error correction method of claim 1, wherein, In step S31, a heat insulation plate (8) is arranged on the outer side of the quartz lamp radiation heating array (4) away from the cantilever beam structure test piece (1).

4. The high-temperature strain gauge measurement error correction method of claim 1, wherein, In step S32, the set step is 30-70℃.

5. The high-temperature strain gauge measurement error correction method of claim 4, wherein, In step S32, the set step is 50℃.

6. The high-temperature strain gage measurement error correction method of claim 1, wherein, In step S32, the different temperature rise rates at least include 5℃ / s, 10℃ / s, 15℃ / s, 20℃ / s and 25℃ / s.

7. The high-temperature strain gage measurement error correction method of claim 1, wherein, In step S3, the determination of the correction parameter comprises: obtaining the second strain through interpolation based on the interpolation table; or fitting a three-dimensional curve diagram among the temperature rise rate, the temperature and the strain based on the interpolation table, and calculating the second strain under the specified temperature rise rate and the temperature according to the three-dimensional curve diagram.

8. The high-temperature strain gage measurement error correction method of claim 1, wherein, After step S4, the method further comprises the following step: Step S5, determining a thermal stress and a structural stress of the specified component according to the second strain and the third strain respectively, and evaluating the strength of the specified component or optimizing the specified component according to the thermal stress and the structural stress.

9. A high temperature strain gauge measurement error correction device, characterized by, The method comprises: a first strain measurement module, configured to obtain a first strain of a specified component in an aircraft test through a high-temperature strain gauge; a measuring point temperature and temperature rise rate measurement module, configured to obtain a measuring point temperature and a temperature rise rate of the specified component based on a thermocouple arranged on the specified component; a second strain calculation module, configured to determine a second strain caused by temperature according to the measuring point temperature and the temperature rise rate in a preset interpolation table, wherein the interpolation table gives the relationship between the strain and the temperature under different temperature rise rates; a strain parameter correction module, configured to subtract the second strain from the first strain to obtain a third strain of the specified component caused by load; wherein the interpolation table is constructed by the following method: The cantilever beam structure test piece (1) is horizontally placed, one end is fixed, the other end is a cantilever end, the upper and lower surfaces of the cantilever end are provided with strain gauges (2) and thermocouples (3), and the upper and lower sides of the cantilever beam structure test piece (1) are fixed with a quartz lamp radiation heating array (4); The cantilever beam structure test piece (1) is heated by different temperature rising rates, the temperature of the set step and the strain value fed back by the strain gauge (2) at the corresponding temperature are recorded, and the interpolation table is formed.

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