Method and device for correcting measurement error of high-temperature strain gauge

Abstract

The invention belongs to the technical field of flight testing, and particularly relates to a high-temperature strain gauge measurement error correction method and system. The method comprises the following steps: S1, acquiring a first dependent variable of a specified component in an aircraft test through a high-temperature strain gauge; s2, obtaining the measuring point temperature and the temperature rise rate of the specified component based on a thermocouple arranged on the specified component; s3, determining a second dependent variable caused by the temperature in a preset interpolation table according to the temperature of the measuring point and the temperature rise rate, wherein the relationship between the dependent variable and the temperature under different temperature rise rates is given in the interpolation table; and S4, subtracting the second dependent variable from the first dependent variable to obtain a third dependent variable, caused by the load, of the specified component. According to the method, the strain of the thermal structure of the aircraft under the high-temperature condition can be accurately calculated, and benchmarking data is provided for heat protection and heat transfer calculation of key components on a full flight envelope.

Description

Technical Field

[0001] The present application belongs to the field of flight test technology, and in particular relates to a method and device for correcting measurement errors of high-temperature strain gauges. Background Art

[0002] Thermal stress damage caused by aerodynamic heating is a prominent problem in the thermal protection design of hypersonic aircraft. Under the action of aerodynamic heating, the structure of the hypersonic aircraft will produce great thermal stress. 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 hypersonic aircraft. To solve the problem of plastic deformation or even damage of material structure caused by thermal stress, it is necessary to measure and analyze the stress field of the structure, obtain the thermal stress of key parts, and estimate the damage probability, which is very critical for analyzing the success and reliability of thermal protection design.

[0003] At present, some research has been carried out in China on high-temperature strain measurement technology. Compared with normal temperature strain measurement, temperature will affect the sensitivity, heat output, zero drift and creep of strain gauges. Effective correction methods are needed to ensure the accuracy of measurement results. Generally, the thermal output curve correction method is used to calibrate the high-temperature strain gauge in a steady-state thermal output within the expected working temperature range of the high-temperature strain gauge, and draw a thermal output curve. According to the actual measurement results, the thermal output value on the corresponding curve is corrected. This method that does not consider the influence of temperature rise rate on high-temperature strain is called steady-state thermal output calibration. For hypersonic vehicles, the flight process is in a complex load environment, and the temperature rise rate of the structure is constantly changing. Using the traditional steady-state thermal output curve for error correction makes the high-temperature strain measurement value differ greatly from the predicted result. Summary of the invention

[0004] In order to solve the above problems, the present application provides a method and device for correcting the measurement error of a high-temperature strain gauge, so as to achieve accurate measurement of the high-temperature strain of a complex structure under a complex load environment during flight.

[0005] The first aspect of the present application provides a method for correcting measurement errors of high temperature strain gauges, mainly comprising:

[0006] Step S1, obtaining a first strain value of a designated component in an aircraft test by using a high temperature strain gauge;

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

[0008] Step S3, determining a second strain caused by temperature in a preset interpolation table according to the temperature of the measuring point and the temperature rise rate, wherein the interpolation table specifies the relationship between the strain and temperature at different temperature rise rates;

[0009] Step S4: subtract the second strain from the first strain to obtain a third strain of the designated component caused by the load.

[0010] Preferably, before step S3, the interpolation table is further constructed in the following manner:

[0011] Step S31, placing the cantilever beam structure test piece horizontally, with one end fixed and the other end being a cantilever end, strain gauges and thermocouples being arranged on the upper and lower surfaces of the cantilever end, and quartz lamp radiation heating arrays being 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 of the set step and the strain value fed back by the strain gauge at the corresponding temperature, and forming the interpolation table.

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

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

[0015] Preferably, in step S32, the setting step is 30-70°C.

[0016] Preferably, in step S32, the setting step is 50°C.

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

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

[0019] Perform interpolation based on the interpolation table to obtain the second strain value; or

[0020] A three-dimensional curve diagram between the temperature rise rate, temperature and strain is fitted based on the interpolation table, and the second strain at the specified temperature rise rate and temperature is calculated according to the three-dimensional curve diagram.

[0021] Preferably, step S4 further includes:

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

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

[0024] A first strain measurement module, used to obtain the first strain of a specified component in an aircraft test through a high-temperature strain gauge;

[0025] A measuring point temperature and temperature rise rate measuring module, used for obtaining the measuring point temperature and temperature rise rate of the designated component based on a thermocouple arranged on the designated component;

[0026] A second strain calculation module, used to determine a second strain caused by temperature in a preset interpolation table according to the temperature of the measuring point and the temperature rise rate, wherein the interpolation table specifies the relationship between the strain and temperature at different temperature rise rates;

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

[0028] This application can accurately calculate the strain of the aircraft's thermal structure under high temperature conditions, provide benchmark data for the thermal protection and heat transfer calculations of key components in the entire flight envelope, verify the thermal-mechanical coupling finite element analysis and calculation technology, complete a comprehensive evaluation of the heat transfer performance under severe flight conditions, and guide the thermal structure design. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of a preferred embodiment of the high temperature strain gauge measurement error correction method of the present application.

[0030] Figure 2 It is a schematic diagram of the transient heat output calibration test device of the present 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-thermal insulation board. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the implementation of this application will be described in more detail in combination with the drawings in the implementation of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and cannot be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in combination with the drawings.

[0033] The first aspect of the present application provides a method for correcting measurement errors of high temperature strain gauges, such as Figure 1 As shown, the method includes:

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

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

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

[0037] Step S4: subtract the second strain from the first strain to obtain a third strain of the designated component caused by the load.

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

[0039] The cantilever beam is mechanically loaded at room temperature, and the ratio of the elongation to the original length is the first strain ε1. Since at room temperature, the first strain ε1 is entirely the third strain ε3 = σ / E caused by mechanical loading, and the second strain ε2 caused by thermal stress is 0, the cantilever beam structural strain should be ε3 = ε1-ε2 = σ / E.

[0040] When the cantilever beam is heated freely and without mechanical load, the ratio of the elongation of the cantilever beam to its original length is the first strain ε1=α*ΔT, where α is the linear expansion coefficient. The first strain ε1 is entirely the second strain ε2 caused by temperature change. At this time, the structural strain of the cantilever beam should be ε3=ε1-ε2=0, and there is no stress in the cantilever beam.

[0041] When the cantilever beam is loaded with both force and heat, the first strain ε1 is caused by both temperature change and mechanical load, that is, ε1=α*ΔT+σ / E. Excluding the ratio of the elongation caused by temperature change under free heating to the original length ε2=α*ΔT, 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 constantly changing, then the ratio of the elongation caused by the temperature change to the original length ε2 under free heating conditions cannot reach the steady-state value α*ΔT during the transient temperature change process, that is, ε2 = α*ΔT*K, where K is a coefficient whose value is less than 1.

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

[0044] In some optional implementations, before step S3, the interpolation table is further constructed in the following manner:

[0045] Step S31, place the cantilever beam structure test piece 1 horizontally, with one end fixed and the other end being 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 quartz lamp radiation heating arrays 4.

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

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

[0048] In step S31, the test device is as follows Figure 2 As shown, the cantilever beam structure test piece 1 is placed horizontally and fixed on the vertical beam 6 by bolts on the fixed support 5. A densely arranged quartz lamp radiation heating array 4 is installed at a certain distance from the upper and lower surfaces of the arm beam structure test piece 1 to heat the upper and lower surfaces of the test piece at the same time, thereby generating a dynamically changeable high-temperature thermal test environment. A thermal isolation plate with a water cooling channel 7 is provided between the fixed support 5 and the vertical beam 6 of the cantilever beam structure test piece 1. During the test, the flowing water takes away part of the heat, thereby forming a temperature buffer zone between the arm beam structure test piece 1 and the vertical beam 6. In addition, a high-temperature resistant ceramic insulation board 8 is installed on the outside of the quartz lamp radiation heating array 4 to thermally shield the high-temperature heating area, thereby ensuring the heating effect and the safety of the sensor and power supply line. The upper and lower symmetrical points in the middle area of ​​the outer surface of the cantilever beam structure test piece 1 are selected as measurement points, and a high-temperature strain gauge 2 is pasted, and a pair of thermocouples 3 are pasted at adjacent positions to detect and control the temperature of the measurement point; the heating system adopts a transient thermal test control system, which can implement continuous, rapid and accurate dynamic control of the temperature rise rate according to the temperature change.

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

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

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

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

[0053] In step S32, by adjusting the temperature control system, first set the temperature rise rate to 5°C / s, heat through the quartz lamp, and start circulating the liquid in the water cooling channel. The thermocouple detects that the temperature rises by 50°C every time and collects the corresponding strain gauge reading and records the temperature value at this time. When the cantilever beam temperature reaches 900°C, stop heating. Cool the test piece to room temperature, adjust the temperature control system, and set the temperature rise rate to 10°C / s, 15°C / s, 20°C / s, and 25°C / s in sequence. Repeat the above steps to obtain the temperature-heat output strain curves corresponding to the five temperature rise rates.

[0054] The present application controls the heat flux of quartz lamp radiation heating and adjusts the heating temperature rise rate by adjusting the temperature rise rate of the heating system, thereby measuring the thermal output strain in different temperature states under different temperature rise rates. The method is simple and feasible and is suitable for the complex thermal load environment that changes rapidly in aircraft flight tests.

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

[0056] Perform interpolation based on the interpolation table to obtain the second strain value; or

[0057] A three-dimensional curve diagram between the temperature rise rate, temperature and strain is fitted based on the interpolation table, and the second strain at the specified temperature rise rate and temperature is calculated according to the three-dimensional curve diagram.

[0058] This embodiment can obtain the second strain value by means of two interpolations, or can construct a three-dimensional curve graph in advance, thereby providing heat output correction at any temperature rise rate and temperature for high-temperature strain measurement.

[0059] In some optional implementations, step S4 further includes:

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

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

[0062] A first strain measurement module, used to obtain the first strain of a specified component in an aircraft test through a high-temperature strain gauge;

[0063] A measuring point temperature and temperature rise rate measuring module, used for obtaining the measuring point temperature and temperature rise rate of the designated component based on a thermocouple arranged on the designated component;

[0064] A second strain calculation module, used to determine a second strain caused by temperature in a preset interpolation table according to the temperature of the measuring point and the temperature rise rate, wherein the interpolation table specifies the relationship between the strain and temperature at different temperature rise rates;

[0065] The strain parameter correction module is used to subtract the second strain from the first strain to obtain a third strain of the designated component caused by the load.

[0066] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for correcting measurement errors of high temperature strain gauges, characterized in that: include: Step S1, obtaining a first strain value of a designated component in an aircraft test by using a high temperature strain gauge; Step S2, obtaining the measuring point temperature and temperature rise rate of the designated component based on the thermocouple arranged on the designated component; Step S3, determining a second strain caused by temperature in a preset interpolation table according to the temperature of the measuring point and the temperature rise rate, wherein the interpolation table specifies the relationship between the strain and temperature at different temperature rise rates; Step S4: subtract the second strain from the first strain to obtain a third strain of the designated component caused by the load.

2. The high temperature strain gauge measurement error correction method according to claim 1, characterized in that: Before step S3, the method further includes constructing the interpolation table in the following manner: Step S31, placing the cantilever beam structure test piece (1) horizontally, with one end fixed and the other end being a cantilever end, the upper and lower surfaces of the cantilever end being provided with strain gauges (2) and thermocouples (3), and the upper and lower sides of the cantilever beam structure test piece (1) being fixed with quartz lamp radiation heating arrays (4); Step S32, heating the cantilever beam structure test piece (1) at different temperature rise rates, recording the temperature of the set step and the strain value fed back by the strain gauge (2) at the corresponding temperature, and forming the interpolation table.

3. The high temperature strain gauge measurement error correction method according to claim 2, characterized in that: In step S31, the cantilever beam structure test piece (1) is fixed on the vertical beam (6) through a fixed support (5), and a water cooling channel (7) is provided on the fixed support (5).

4. The high temperature strain gauge measurement error correction method according to claim 2, characterized in that: In step S31, a heat insulation board (8) is provided on the outer side of the quartz lamp radiation heating array (4) facing away from the cantilever beam structure test piece (1).

5. The high temperature strain gauge measurement error correction method according to claim 2, characterized in that: In step S32, the setting step is 30-70°C.

6. The high temperature strain gauge measurement error correction method according to claim 5, characterized in that: In step S32, the setting step is 50°C.

7. The high temperature strain gauge measurement error correction method according to claim 2, characterized in that: In step S32, the different temperature rise rates include at least 5°C / s, 10°C / s, 15°C / s, 20°C / s, and 25°C / s.

8. The high temperature strain gauge measurement error correction method according to claim 1, characterized in that: In step S3, determining the correction parameter includes: Perform interpolation based on the interpolation table to obtain the second strain value; or A three-dimensional curve diagram between the temperature rise rate, temperature and strain is fitted based on the interpolation table, and the second strain at the specified temperature rise rate and temperature is calculated according to the three-dimensional curve diagram.

9. The high temperature strain gauge measurement error correction method according to claim 1, characterized in that: Step S4 further includes: Step S5: determining the thermal stress and the structural stress of the designated component according to the second strain and the third strain respectively, and evaluating the strength of the designated component or optimizing the designated component according to the thermal stress and the structural stress.

10. A high temperature strain gauge measurement error correction device, characterized in that: include: A first strain measurement module, used to obtain the first strain of a specified component in an aircraft test through a high-temperature strain gauge; A measuring point temperature and temperature rise rate measuring module, used for obtaining the measuring point temperature and temperature rise rate of the designated component based on a thermocouple arranged on the designated component; A second strain calculation module, used to determine a second strain caused by temperature in a preset interpolation table according to the temperature of the measuring point and the temperature rise rate, wherein the interpolation table specifies the relationship between the strain and temperature at different temperature rise rates; The strain parameter correction module is used to subtract the second strain from the first strain to obtain a third strain of the designated component caused by the load.

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