A method for collecting and processing strain information of intermediate casing of aircraft engine

Abstract

The present invention discloses a method for collecting and processing strain information of the intermediate casing of an aircraft engine. The method integrates regional gradient optimization of measuring point arrangement, cubic spline interpolation and quadratic surface fitting to calculate strain parameters of unmeasured points, and finally further optimizes the arrangement of strain sensor sampling positions through fitness function evaluation, and finally obtains accurate strain information of non-sampling points on the surface of the casing to be measured. The present invention provides a key data source guarantee for the subsequent use of the processed high-precision strain data to complete the reconstruction of the intermediate casing strain field and the intelligent visualization display of the intermediate casing strain.

Description

Technical Field

[0001] The present invention designs a strain information data processing and strain sensor sampling point distribution method, specifically relates to a sensor point distribution iteration method based on regional gradient optimization, a non-measurement point strain parameter calculation method based on cubic spline interpolation and quadratic surface fitting, and a strain measurement point information evaluation optimization method based on fitness function. Background Art

[0002] During the service of an aircraft, harsh working environments can easily lead to structural damage, which can cause malfunctions and mission failures at the least, or even cause aircraft destruction and loss of life. The engine casing, as an important part of an aircraft engine, is the base of the entire engine and the main load-bearing component of an aircraft engine. When the engine casing is in operation, it mainly bears gas loads and mass inertia forces, and secondly, thermal loads, acoustic loads, and some assembly stresses. The state of the casing reflects the working state of the engine, and flight safety is greatly improved by monitoring the health of the engine casing.

[0003] However, the intermediate casing is large in size, complex in structure, and thin in wall, making it very difficult to manufacture. Whether it is the traditional decomposition casting plus welding and riveting, or the modern one-step forming manufacturing method, the casing production process is still complicated and quality control is difficult. At the same time, due to its proximity to the combustion chamber, the intermediate casing needs to work under high temperature and high pressure. During the operation of the engine, the axial load of the casing is about several tons. The harsh environment and performance requirements determine that the casing must have high strength and other properties.

[0004] Strain and deformation information are important physical parameters that characterize the health monitoring of mechanical structures. At present, strain measurement mainly includes strain gauge measurement, acoustic measurement, and optical fiber measurement. The resistance strain gauge measurement method is the most traditional method for measuring strain and is widely used. The strain gauge measurement method has the advantages of high precision and small size, but it cannot form a distributed monitoring network and is also susceptible to noise interference. The acoustic measurement method calculates the stress and strain of the structure based on the relationship between stress and strain and sound velocity in the sound wave formula by the sound velocity method. The optical fiber measurement method calculates the strain of the structure through the relationship between strain and the offset of the optical fiber center wavelength. The optical fiber measurement method has the advantages of high precision, anti-electromagnetic interference, and easy to form a distributed monitoring network. It has been widely used in the field of strain monitoring.

[0005] However, the current measurement method can only monitor the strain at a certain stress measurement point, and cannot accurately obtain the strain value of the non-sensor collection point in the test area, which cannot meet the monitoring needs of the strain parameters of the test area of ​​the casing. It is necessary to develop an efficient intermediate casing strain information sampling and processing method to provide an important basis for the safety assessment of the casing structure. Summary of the invention

[0006] The purpose of the present invention is to provide a method for sampling and processing strain information of an aircraft engine casing in response to the demand for monitoring the strain and deformation of an aircraft engine intermediate casing. The method first calculates the strain data of non-collected points by cubic spline interpolation and quadratic surface fitting, and calculates the surface strain information of the casing to be measured. Then, the regional gradient method is introduced to iteratively optimize the initial layout of the strain sensor. After the three-dimensional model of the casing is established, a finite element simulation is performed on it, and finally the fitness function is evaluated using the interpolation calculation data and the simulation data. After multiple iterations, the optimal layout of the strain sensor of the strain intermediate casing is achieved.

[0007] The present invention is achieved by adopting the following technical solutions:

[0008] A method for collecting and processing strain information of an intermediate casing of an aircraft engine comprises the following steps:

[0009] Step 1: Sampling the strain data of the area to be tested in the casing and performing augmentation processing to calculate the strain values ​​of other unmeasured points in the area to be tested;

[0010] Step 2: Iterative optimization of regional gradient classification is performed according to the change of the augmented calculated strain value in the measured area. After reaching the specified threshold, the iteration stops to obtain the first strain sensor optimization layout position;

[0011] Step 3: Establish a three-dimensional model of the casing and use finite element software to analyze the simulated strain value of the intermediate casing test area under the selected working conditions;

[0012] Step 4: Using the strain data calculated in step 1 and the simulated strain data in step 3, construct a fitness function to iteratively optimize the point placement in step 2 multiple times, and finally obtain the optimal sensor point placement.

[0013] A further improvement of the present invention is that in step 1, based on the strain monitoring requirements and taking into account the structural mechanical properties of the casing itself and the ambient temperature, an optimal sensor layout area is selected in the intermediate casing of the aircraft engine, and the strain sensors are evenly arranged in the area to be measured.

[0014] A further improvement of the present invention is that in step 1, the strain parameter values ​​of the points in the intermediate casing to be measured area are measured multiple times under the selected working conditions of the aircraft engine and the average value is taken as the original strain data of the intermediate casing to be measured area under the working conditions.

[0015] A further improvement of the present invention is that in step 1, the strain region is expanded into a plane, a strain (x, y, l) three-dimensional coordinate system is established through the azimuth coordinates x, y, and the strain variable l, and a cubic spline interpolation calculation is performed on the strain measuring points in the same plane to obtain multiple interpolation surface functions g i(x), select 4-10 interpolation points between the two measuring points, and calculate the strain surface equation ξ of the augmented strain data by the quadratic surface fitting method to achieve effective data augmentation and calculate the strain values ​​of any other unmeasured points.

[0016] A further improvement of the present invention is that, in step 2, the casing is gradient-divided into different intervals according to the size of the strain gradient in the area to be measured, the strain sensor arrangement density is increased in the high strain gradient change interval, and the strain sensor arrangement density is reduced in the gentle strain change interval.

[0017] A further improvement of the present invention is that in step 2, after the sampling points are updated based on the regional gradient optimization method, the strain data measurement and augmentation in step 1 are performed, and the strain gradient division value and the distribution density of strain sensors within the same gradient are further adjusted according to the strain calculation results. After multiple iterations, the process is stopped after the change in the strain fitting surface and the change in the sensor position are lower than the specified threshold.

[0018] A further improvement of the present invention is that in step 3, the intermediate casing of the aircraft engine is scanned by a high-precision three-dimensional coordinate measuring instrument to obtain the three-dimensional structural data of the casing, and the data is preprocessed, meshed and optimized, and finally a three-dimensional model of the casing is reconstructed.

[0019] A further improvement of the present invention is that, in step 3, the mechanical conditions, environmental changes and stress characteristics of the casing under the working condition are analyzed, finite element simulation is performed on the three-dimensional model of the casing, and the strain simulation value of the casing area to be tested is obtained.

[0020] A further improvement of the present invention is that in step 4, the strain average value b is calculated by interpolation of each area in the measuring point arrangement. i Compared with the average strain value a of finite element simulation i Establish the fitness function J based on the similarity in two-dimensional direction i , through J i The similarity of strain calculation data at different points of the calculation box is calculated to determine the deviation between the calculation results of the unarranged measuring points and the actual finite element simulation values.

[0021] A further improvement of the present invention is that in step 4, the sensor arrangement points around the place where the simulation calculation and the interpolation calculation have larger interpolation values ​​are corrected, and steps 1 and 4 are repeated after correction. i When the value is less than the specified threshold, the iteration stops and the optimal sensor layout position is obtained.

[0022] The present invention has at least the following beneficial technical effects:

[0023] The present invention is an invention for strain sensor data processing and strain sensor point optimization of the intermediate casing of an aircraft engine. By using the point arrangement method of the present invention, high-precision measurement of the overall strain of the intermediate casing can be achieved when sensors with the same precision level collect strain parameters, which can better meet the research on strain sensitive information of the intermediate casing. It more truly reflects the working state and working environment of the aircraft engine during operation, and provides necessary data support for health detection of the engine casing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of the present invention;

[0025] Figure 2 It is the cubic spline interpolation process and the quadratic fitting surface process;

[0026] Figure 3 is the interpolation schematic diagram;

[0027] Figure 4 This is a comparison chart of the smoothness of non-interpolated surface and interpolated surface. Figure 4 (a) is direct fitting, Figure 4 (b) is the fitting after interpolation;

[0028] Figure 5 Optimization diagram for regional gradient method;

[0029] Figure 6 (a) and (b) are simplified three-dimensional structure models of the casing;

[0030] Figure 7 It is the fitness function evaluation process;

[0031] Figure 8 (a) and (b) are schematic diagrams showing the decrease in fitness function value after iteration.

[0032] Fig. 9 This is a schematic diagram of the three-dimensional model of the intermediate casing of a certain type of engine.

[0033] Fig.10 This is the point distribution diagram of a certain model of engine casing.

[0034] Fig.11 Expand the strain gradient variation diagram for the outer surface of the casing.

[0035] Fig.12 The strain gradient change contour map of the outer surface of the casing after iteration.

[0036] Fig.13 The strain gradient change map and sensor layout point map of the outer surface of the casing after iteration are developed.

[0037] Fig.14The strain gradient change map and gradient contour map of the outer surface of the casing are developed for the finite element simulation.

[0038] Fig.15 The contour map of the adaptive reading function value and the arrangement of strain sensor points are developed for the outer surface of the casing in the finite element simulation before iteration.

[0039] Fig.16 The contour map of the adaptive reading function value and the arrangement of strain sensor points are developed for the outer surface of the final finite element simulation casing after iteration. DETAILED DESCRIPTION

[0040] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0041] like Figure 1 As shown, the present invention provides a method for sampling and processing strain information of an aircraft engine casing, comprising the following steps: the first step is to select the optimal sensor layout area in the intermediate casing of the aircraft engine according to the strain monitoring requirements and taking into account the structural mechanical properties of the casing itself and the ambient temperature, and to evenly arrange the strain sensors in the area to be measured.

[0042] The second step is to measure the strain parameter values ​​of the points in the test area of ​​the intermediate casing multiple times under the selected working conditions of the aircraft engine and take the average as the original strain data of the test area of ​​the intermediate casing under the working conditions.

[0043] The third step is to interpolate the points on the same plane through cubic spline interpolation, and then use the quadratic surface fitting method to fit the strain surface of the intermediate casing, and calculate the strain values ​​of other unmeasured points through the calculated interpolation curve surface function.

[0044] The fourth step is to divide the casing into different gradient areas according to the strain gradient of the casing to be tested area after fitting, and arrange different density sensors in each area.

[0045] The fifth step is to update the arrangement of strain sensors, measure the strain data of the intermediate casing of the aircraft engine under the same working conditions, repeat the interpolation calculation steps, and further modify the gradient division value, the distribution density of strain sensors within the same gradient and other parameters according to the measurement results. After multiple iterations, the process stops when the change in the strain fitting surface and the change in the sensor position are lower than a certain threshold.

[0046] Step 6: Use the three-dimensional simulation model to perform finite element simulation on the casing strain under the working condition. The strain data of the casing to be tested area under the working condition is obtained through the finite element strain simulation test of the casing to be tested area.

[0047] Step 7: Establish a fitness function based on the similarity between the actual calculated displacement components of each node in the measurement point layout and the finite element displacement components in the two-dimensional direction. Determine the deviation between the estimated value of the undeployed measurement point and the actual finite element simulation value, and correct the sensor point position near the position with large deviation. Then repeat the calculation of the strain variables of other undeployed points, and repeat the fitness function test, and finally obtain the optimal sensor point position after multiple iterations.

[0048] Specifically, the present invention is implemented by the following steps:

[0049] Step 1: Sensor initialization layout

[0050] Based on the actual monitoring needs, and combined with the structure, material properties, mechanical properties, operating temperature, etc. of the casing itself, select the optimal strain sensor acquisition area. According to the number and type of sensors, the sensor sampling density is reasonably selected and evenly arranged on the surface to be measured. Ensure the measurement accuracy of the initial strain value. Meet the subsequent calculation requirements as much as possible and reduce the number of iterations.

[0051] Step 2: Strain measurement under common working conditions

[0052] The working condition to be tested is selected, and the strain parameters of the points in the test area of ​​the intermediate casing are measured multiple times. After eliminating the gross errors, the average value is taken as the original strain data of the test area of ​​the intermediate casing under the working condition.

[0053] Step 3: Strain data processing

[0054] The strain area is expanded into a plane, and the position-strain (x, y, l) three-dimensional coordinate system is established using the horizontal coordinate x, vertical coordinate y, and strain l of the distribution point. The strain measurement points on the same plane are calculated by cubic spline interpolation. After traversal calculation, multiple interpolation surface functions g are obtained. i (x), 4-10 interpolation points can be selected between each measuring point as strain data augmentation, and the strain surface equation ξ is calculated by quadratic surface fitting for the augmented strain data, and finally the data is effectively augmented, and the strain value of any area without measuring points can be calculated. Figure 2 Figure 3 shown.

[0055] Step 4: Gradient Optimization Sensor Distribution

[0056] The casing is divided into different intervals according to the strain gradient of the area to be tested. The density of sensor layout is increased in the high strain gradient change interval, and the density of sensor layout is reduced in the interval with gentle strain change. Figure 5 shown.

[0057] Step 5: Initial iteration of sensor layout

[0058] After updating the arrangement of the casing strain sensors, the strain data of the intermediate casing of the aircraft engine is measured under the same working conditions, and steps 2 to 4 are repeated. According to the measurement results, the gradient division value, the distribution density of strain sensors within the same gradient and other parameters are further modified. After multiple iterations, the method stops when the variation of the strain fitting surface and the variation of the sensor position are lower than the specified threshold. Figure 5 shown.

[0059] Step 6: 3D modeling and finite element simulation of the receiver area to be tested

[0060] The intermediate casing of the aircraft engine is scanned by a high-precision sensor to obtain the casing structure data and perform data preprocessing, mesh patching, mesh optimization and other operations. The three-dimensional simulation model of the intermediate casing is reconstructed. The mechanical conditions, environmental changes and stress characteristics of the casing under this working condition are analyzed, and the finite element simulation of the casing is performed to obtain the strain simulation data of the casing to be tested under this working condition.

[0061] Step 7: Fitness function optimization

[0062] According to the finite element simulation results, the casing is divided into different strain regions. The strain magnitudes in the regions are similar. The average value b of the interpolated strain of the measuring points in the region is calculated. i Compared with the average strain value a of finite element simulation i Establish the fitness function J based on the similarity in the two-dimensional direction. Set the threshold H and pass b i 、a i , Δb, Δa, Δh to calculate J i And compare it with H to determine the deviation between the calculated value of the unarranged measuring point in the area and the actual finite element simulation value, and find out whether the existing fitting surface interpolation meets the use requirements, and correct the sensor point arrangement in the strain difference area. Figure 7 shown.

[0063] Step 8: Iterative correction:

[0064] After adjusting the sensor point locations in the area with large difference after fitness function calculation, repeat the strain calculation of other undistributed points in step 3, and repeat the fitness function test in step 7. After multiple iterations, i The iteration stops when it is less than the specified threshold, such as Figure 8 As shown. At this time, the optimal sensor layout position is obtained.

[0065] Example:

[0066] like Fig. 9 As shown, the intermediate casing of a certain model of aircraft engine is analyzed as follows:

[0067] In the first step, strain sensors are evenly arranged on the outer surface of a certain type of intermediate casing, and the strain on the outer surface is measured after the working conditions are selected to obtain the strain data of the sensor points, such as Fig.10 shown.

[0068] In the second step, the outer surface of the intermediate casing is processed, a three-dimensional coordinate system is added, and the three-dimensional coordinates (x position, y position, l strain) of each strain point are determined. The strain data is augmented, and the surface strain data set of the casing in this area is finally obtained through quadratic surface fitting. The strain change gradient is calculated based on the strain data set, and the strain is plotted. Fig.11 The surface shown.

[0069] The third step is to divide the casing surface into n gradient regions of different sizes according to the strain change gradient surface diagram. i Represents the gradient level of the region (from high to low: n~1) and the area of ​​each region is s i , the total area is s, a is the regularization hyperparameter, and the original number of x strain sensors are arranged respectively. The number of strain sensors arranged in different areas is calculated as follows:

[0070]

[0071] Then measure the strain data of the casing under the same working conditions, repeat the interpolation calculation steps, and further modify the gradient division value, the distribution density of strain sensors within the same gradient and other parameters according to the measurement results. After multiple iterations, stop when the change of the strain fitting surface and the change of the sensor position are lower than a certain threshold. The final result is as follows Fig.12 and Fig.13 As shown:

[0072] The fourth step is to use the intermediate casing three-dimensional model to perform finite element simulation under the selected working condition, obtain the outer surface strain value of the casing under the working condition, and expand the outer surface to calculate the strain gradient change, and obtain the strain gradient change diagram, such as Fig.14 As shown:

[0073] Step 5: According to the finite element simulation results, the casing is divided into different strain regions. The strain magnitudes in the regions are similar. The fitness function is established based on the similarity between the average value bi of the interpolated strain calculated by the measuring points in the region and the average value ai of the finite element simulation strain in the two-dimensional direction:

[0074]

[0075] The threshold value H is specified, and Ji is calculated through bi, ai, Δb, Δa, and Δh and compared with H to determine the deviation between the calculated value of the undeployed measurement points in the area and the actual finite element simulation value, and to determine whether the existing fitted surface interpolation meets the use requirements, and to correct the sensor point distribution in the strain difference area. After the fitness function is calculated, the sensor point distribution position is adjusted in the area with a large difference, and the calculation of other undeployed strain variables and fitness function detection are repeated. After multiple iterations, when Ji is less than the specified threshold, the iteration stops and the optimal point distribution is obtained, such as Fig.15 and Fig.16 As shown:

[0076] The final position of the strain sensor is obtained by iterating the two methods, which avoids as much as possible the situation of insufficient data collection at key points and redundant information collection at non-key points, and realizes the accurate measurement and calculation of the intermediate casing strain information.

[0077] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for collecting and processing strain information of an aircraft engine intermediate casing, characterized in that: The following steps are involved: Step 1: Sampling the strain data of the area to be tested in the casing and performing augmentation processing to calculate the strain values ​​of other unarranged measuring points in the area to be tested; expanding the strain area into a plane, establishing a strain (x, y, l) three-dimensional coordinate system through the azimuth coordinates x, y, and strain l, performing cubic spline interpolation calculation on the strain measuring points in the same plane, and obtaining multiple interpolation surface functions g i (x), select 4-10 interpolation points between the two measuring points, calculate the strain surface equation ξ of the augmented strain data by the quadratic surface fitting method, realize effective data augmentation, and calculate the strain value of any other unmeasured points; Step 2: Iterative optimization of regional gradient classification is performed according to the change of the augmented calculated strain value in the measured area. After reaching the specified threshold, the iteration stops to obtain the first strain sensor optimization layout position; After updating the sampling points based on the regional gradient optimization method, the strain data measurement and augmentation in step 1 are performed, and the strain gradient division value and the distribution density of strain sensors within the same gradient are further adjusted according to the strain calculation results. After multiple iterations, the process stops when the change in the strain fitting surface and the change in the sensor position are lower than the specified threshold. Step 3: Establish a three-dimensional model of the casing and use finite element software to analyze the simulated strain value of the intermediate casing test area under the selected working conditions; Step 4: Using the strain data calculated in step 1 and the simulated strain data in step 3, construct a fitness function to iterate and optimize the point arrangement in step 2 multiple times, and finally obtain the optimal sensor point arrangement position; interpolate the strain average value b of each area in the measurement point arrangement i Compared with the average strain value a of finite element simulation i Establish the fitness function J based on the similarity in two-dimensional direction i , through J i The similarity of strain calculation data at different points of the calculation box is calculated to determine the deviation between the calculation results of the unarranged measuring points and the actual finite element simulation values.

2. The method for collecting and processing strain information of an aircraft engine intermediate casing according to claim 1 is characterized in that: In step 1, according to the strain monitoring requirements and taking into account the structural mechanical properties of the casing itself and the ambient temperature, the optimal sensor layout area is selected in the intermediate casing of the aircraft engine, and the strain sensors are evenly arranged in the area to be tested.

3. The method for collecting and processing strain information of an aircraft engine intermediate casing according to claim 1 is characterized in that: In step 1, the strain parameter values ​​of the points in the test area of ​​the intermediate casing are measured multiple times under the selected working conditions of the aircraft engine, and the average value is taken as the original strain data of the test area of ​​the intermediate casing under the working conditions.

4. The method for collecting and processing strain information of an aircraft engine intermediate casing according to claim 1, characterized in that: In step 2, the casing is divided into different intervals according to the strain gradient of the area to be measured, the strain sensor arrangement density is increased in the high strain gradient change interval, and the strain sensor arrangement density is reduced in the gentle strain change interval.

5. The method for collecting and processing strain information of an aircraft engine intermediate casing according to claim 1, characterized in that: In step 3, the aircraft engine intermediate casing is scanned by a high-precision three-dimensional coordinate measuring instrument to obtain the three-dimensional structure data of the casing, and the data is preprocessed, meshed, and optimized to finally reconstruct the three-dimensional model of the casing.

6. The method for collecting and processing strain information of an aircraft engine intermediate casing according to claim 1, characterized in that: In step 3, the mechanical conditions, environmental changes and stress characteristics of the casing under the working condition are analyzed, and the finite element simulation of the casing three-dimensional model is performed to obtain the strain simulation value of the casing area to be tested.

7. The method for collecting and processing strain information of an aircraft engine intermediate casing according to claim 1, characterized in that: In step 4, the sensor arrangement points around the place where the interpolation value between the simulation calculation and the interpolation calculation is larger are corrected. After the correction, steps 1 and 4 are repeated. After multiple iterations, J i When the value is less than the specified threshold, the iteration stops and the optimal sensor layout position is obtained.

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