Maximum strain position measuring and positioning method

Abstract

The invention discloses a maximum strain position measuring and positioning method, and relates to the technical field of vibration fatigue strength tests of engine blades and materials, and the method comprises the steps: building a three-dimensional geometric model of a to-be-tested blade 4, carrying out the finite element simulation analysis, obtaining a full-field strain distribution rule, and determining a region where the maximum strain distribution is located; resistance strain gauges are pasted on the central axis of the maximum strain distribution area of the blade back face at equal intervals, and the distance between the sensitive grid center of each resistance strain gauge and the blade root is recorded; applying resident excitation with constant amplitude under the resonant frequency of the to-be-tested blade 4, and collecting the strain value of the resistance strain gauge; constructing a matrix equation set of a strain distribution quadratic function, and solving coefficients to obtain a strain distribution function; and calculating the distance between the maximum strain position point and the blade root according to the strain distribution function, and pasting a resistance strain gauge at the maximum strain position point to carry out stress calibration measurement of the fatigue strength test.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vibration fatigue strength test of engine blades and materials, and particularly relates to a maximum strain position measurement and positioning method. BACKGROUND

[0002] With the development of large-scale rotating machinery structures (such as aero-engine blades, gas turbine blades and wind power blades) towards high performance and light weight, the dynamic load and vibration environment thereof are increasingly complex, resulting in increasingly prominent fatigue damage and fracture problems. In order to master the stress characteristics and fatigue risks of the blades under different vibration modes, strain measurement technology becomes a key experimental means. Traditional strain testing mainly relies on manual experience to select measurement points or on static simulation results to determine the strain gauge sticking position. However, due to the obvious spatial nonlinearity and local concentration characteristics of the vibration mode distribution of the blades at the resonance frequency, the traditional method is difficult to ensure the accurate capture of the maximum strain point. In addition, the surface of the blade has complex curvature and torsion structure, and the sticking position error of the strain gauge is easy to cause stress calibration deviation, thereby affecting the reliability of fatigue life evaluation. Especially in the resonance fatigue test, if the strain gauge is not accurately arranged in the maximum strain area, the collected data will not match the actual stress state, thereby reducing the representativeness and precision of the test. Therefore, how to combine finite element simulation and high-precision measurement means to accurately measure and quantitatively position the maximum strain position of the blade surface has become a problem to be solved in the current structure test and fatigue verification field.

[0003] CN14964135A discloses a method for positioning strain gauges on blades, and relates to the field of rotating machinery blade testing. The method first obtains the stress distribution of the blade through CAE software simulation calculation, then selects a strain gauge sticking area and determines a strain gauge positioning window in the area, and then realizes the repeated positioning of multiple blades by using surface unfolding and mask technology. The present application controls the sticking position of the strain gauge by the mask template, thereby significantly improving the repeated positioning accuracy and measurement consistency of the strain gauge. However, the core of this technology still stays at the geometric positioning level, although it can ensure the consistency of the strain gauge positions among different blades, it does not consider the strain distribution variation law of the blade under a specific vibration mode, and cannot realize the dynamic identification and automatic determination of the maximum strain position, so that the calibration accuracy in the fatigue test is still limited by manual point selection and static simulation results.

[0004] CN102141015A discloses a method for attaching a load sensor to the surface of a rotor blade and a rotor blade with a load sensor. The method includes preparing a plurality of holes on the surface of the blade and installing threaded inserts, and fixing a support with a plurality of strain gauges by bolts to achieve measurement of load distribution. This technology can form a stable sensor mounting system on the surface of the structure, and improve the stability and repeatability of load measurement. However, this scheme focuses on the structural installation method of fixing the sensor, is only suitable for static or low-frequency load monitoring scenarios, does not combine the modal characteristics of the blade for strain distribution analysis, lacks spatial quantitative calculation and automatic positioning ability for the maximum strain area, and cannot meet the demand for high-precision identification of the maximum strain point in high-frequency dynamic fatigue testing.

[0005] In summary, the existing blade strain measurement and positioning technology still has obvious deficiencies: first, there is a lack of full-field strain distribution rule extraction method based on modal analysis; second, quantitative solution of the maximum strain point cannot be achieved through a mathematical model; and third, strain gauge layout still relies on manual experience or template positioning, and it is difficult to adapt to dynamic changes in vibration state. In view of the above problems, the present application provides a maximum strain position measurement and positioning method to realize accurate calculation and automatic positioning of the maximum strain point. SUMMARY

[0006] This section is intended to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0007] In view of the problems of the existing blade strain measurement and positioning technology, such as insufficient dynamic modal identification, low strain gauge layout accuracy, and difficulty in quantitative positioning of the maximum strain point, the present application is proposed.

[0008] Therefore, the problem to be solved by the present application is how to combine finite element simulation and strain measurement technology to establish a mathematical model that can reflect the strain distribution rule of the blade under a specific modal, and to realize automatic identification and high-precision positioning of the maximum strain position, so as to provide accurate and reliable stress calibration basis for fatigue strength test.

[0009] To solve the above technical problems, the present application provides the following technical solutions: In a first aspect, the present application provides a maximum strain position measurement and positioning method, which comprises, A three-dimensional geometric model of the blade to be tested 4 is established, finite element simulation analysis is performed, the full-field strain distribution rule of the blade disc surface and the blade back surface under the specified modal vibration shape is obtained, and the maximum strain distribution area and the continuous distribution characteristics are determined; Based on the central axis of the maximum strain distribution area on the back of the blade, resistance strain gauges are attached at equal intervals along the blade root-to-blade tip direction, and the distance from the center of the sensitive grid of the resistance strain gauge to the blade root is recorded. At the resonant frequency of the blade 4 to be tested, a constant amplitude dwell excitation is applied, and the strain value of the resistance strain gauge is collected by the strain measurement system 5. Based on the strain value and the distance, a matrix equation system of the quadratic function of strain distribution is constructed, and the coefficients are solved by calculating the determinant to obtain the strain distribution function; The distance from the blade root to the location of maximum strain is calculated based on the strain distribution function. A resistance strain gauge is then attached to the location of maximum strain for stress calibration measurement in a fatigue strength test.

[0010] As a preferred embodiment of the maximum strain location measurement and positioning method described in this invention, the finite element simulation analysis includes: Obtain the three-dimensional geometric dimensions of the blade 4 to be tested, and establish a three-dimensional geometric model; The three-dimensional geometric model is meshed using the finite element method, and fixed constraint boundary conditions and free boundary conditions are applied. Modal analysis calculations were performed on the three-dimensional geometric model after the domain conditions were applied, and the modal vibrations of the blade 4 under test were extracted within the specified operating frequency range. The target modal vibrations corresponding to the test conditions were selected. The stress-strain field is calculated based on the target mode shape to obtain the full-field strain distribution data of the blade disk surface and the full-field strain distribution data of the blade back surface under the target mode shape.

[0011] As a preferred embodiment of the maximum strain location measurement and positioning method of the present invention, it further includes: A comparative analysis was conducted on the full-field strain distribution data of the blade disk surface and the full-field strain distribution data of the blade back surface. When the peak strain of the full-field strain distribution data of the blade back surface was greater than the peak strain of the full-field strain distribution data of the blade disk surface, the strain distribution curve was extracted. The strain distribution curve was fitted to verify that the strain distribution law conformed to the characteristics of a quadratic function.

[0012] As a preferred embodiment of the maximum strain position measurement and positioning method of the present invention, the resistance strain gauge includes a first resistance strain gauge bonded at equal intervals. Second resistance strain gauge and the third resistance strain gauge The first resistance strain gauge Second resistance strain gauge and the third resistance strain gauge The distance from the center of the sensitive grid to the edge of the leaf root is recorded as the first distance. , the second distance , and the third distance .

[0013] As a preferred solution of the maximum strain position measurement and positioning method, the distance of the maximum strain position point from the blade root is calculated according to the strain distribution function, and the specific formula is as follows: ; Wherein, is the distance of the maximum strain position point from the blade root, is the maximum strain value corresponding to the maximum strain position point, and a, b and c are the coefficients of the quadratic term, the linear term and the constant term of the quadratic function satisfying the strain distribution law.

[0014] As a preferred solution of the maximum strain position measurement and positioning method, the strain distribution function is obtained by: Based on the continuous quadratic function distribution law, a strain distribution quadratic function of the blade to be tested 4 along the blade root-blade tip direction is established; The three groups of strain data , and obtained by the stress distribution test are substituted into the strain distribution quadratic function, and a three-element linear equation group is established; The quadratic term coefficient a, the linear term coefficient b and the constant term coefficient c are solved by using the Cramer rule to determine the strain distribution function.

[0015] In a second aspect, an embodiment of the present application provides a computer device, including a memory and a processor, and the memory stores a computer program, wherein: the processor executes the computer program to realize any step of the above-mentioned maximum strain position measurement and positioning method.

[0016] In a third aspect, an embodiment of the present application provides a computer readable storage medium, which stores a computer program, wherein: the computer program is executed by a processor to realize any step of the above-mentioned maximum strain position measurement and positioning method.

[0017] Compared with the prior art, the application has the beneficial effects that: through finite element simulation for full-field strain analysis of the blade, the maximum strain distribution area and continuous characteristics are determined in the virtual space, the blindness of physical test is fundamentally avoided, a theoretical basis and target area are provided for subsequent actual measurement, and especially the technical problem that the curved surface part cannot be directly pasted is solved; based on the simulation results, equidistant pasting is performed along the central axis of the maximum strain area, complex two-dimensional strain field measurement is simplified to one-dimensional linear sampling, through few measuring points, the cost of multi-channel instrument, process error and system additional mass effect are significantly reduced; under the resonance condition, a steady excitation is applied and strain data are collected, the signal-to-noise ratio and repeatability of the working condition data are ensured; a strain distribution quadratic function model is constructed by using the discrete measuring point data, and the coefficients are solved through matrix operation, the accurate extrapolation from limited data to continuous strain field is realized, the traditional experience speculation is replaced by the mathematical model, and the measurement uncertainty is quantitatively reduced; the maximum strain point is accurately positioned through function calculation and single-point calibration, so that accurate data can be obtained at the most critical part without relying on a large number of pasting in subsequent fatigue test, and the unity of test cost optimization and result reliability is realized. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor. Among them: Figure 1 Flow chart of the maximum strain position measurement and positioning method; Figure 2 Modal vibration shape diagram of the FEA simulation result of the maximum strain position measurement and positioning method; Figure 3 Blade disc stress diagram of the FEA simulation result of the maximum strain position measurement and positioning method; Figure 4 Suction surface stress diagram of the FEA simulation result of the maximum strain position measurement and positioning method; Figure 5 Resistance strain gauge pasting and strain distribution schematic diagram of the maximum strain position measurement and positioning method; Figure 6 Typical test system principle block diagram of the maximum strain position measurement and positioning method; Figure 7 Simulation result and pasting schematic diagram of the maximum strain position measurement and positioning method. DETAILED DESCRIPTION

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort should fall within the scope of protection of this invention.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] As mentioned in the background section, existing blade strain measurement and location technologies still have significant shortcomings: firstly, they lack a method for extracting the full-field strain distribution based on modal analysis; secondly, they cannot quantitatively solve for the maximum strain point through mathematical models; and thirdly, strain gauge placement still relies on manual experience or template positioning, making it difficult to adapt to dynamic changes in vibration conditions. To address these problems, this invention provides a method for measuring and locating the maximum strain position.

[0023] Reference Figures 1-6 , Figure 1 This is a flowchart of a method for measuring and locating the maximum strain position according to an embodiment of the present invention. Figure 1 As shown, a method for measuring and locating the location of maximum strain includes: S1: Establish a three-dimensional geometric model of the blade 4 to be tested, perform finite element simulation analysis, obtain the full-field strain distribution law of the blade disk surface and blade back surface under the specified mode vibration, and determine the region of maximum strain distribution and continuous distribution characteristics. S1.1: Obtain the three-dimensional geometric dimension data of the blade 4 to be tested and establish a three-dimensional geometric model; It should be noted that the three-dimensional geometric model of the mobile phone includes the complete geometric features of the leaf disc, leaf underside, leaf root region, and leaf tip region.

[0024] S1.2: Perform finite element mesh generation on the three-dimensional geometric model and apply fixed constraint boundary conditions and free boundary conditions; Specifically, a refined mesh is set in the blade root region and the expected maximum strain distribution region, and the mesh element size is adaptively adjusted according to the blade geometry. After the mesh is generated, fixed constraint boundary conditions are applied in the blade root region and free boundary conditions are applied in the blade tip region.

[0025] S1.3: Perform modal analysis calculation on the three-dimensional geometric model after applying conditions to the domain, extract the modal vibration shape of each order of the blade 4 to be tested in the specified operating frequency range, and select the target modal vibration shape corresponding to the test operating condition; S1.4: Perform stress-strain field calculation according to the target modal vibration shape to obtain the full-field strain distribution data on the blade disc surface and the full-field strain distribution data on the blade back surface of the blade 4 to be tested under the target modal vibration shape; It should be noted that the target modal vibration shape is a first-order bending vibration shape or other specified order vibration shape; as shown in Figure 2 、 Figure 3 and Figure 4 , the full-field strain distribution data on the blade disc surface and the full-field strain distribution data on the blade back surface are presented in the form of a cloud chart, showing the spatial distribution characteristics of the strain value.

[0026] S1.5: Compare and analyze the full-field strain distribution data on the blade disc surface and the full-field strain distribution data on the blade back surface. When the peak strain of the full-field strain distribution data on the blade back surface is greater than the peak strain of the full-field strain distribution data on the blade disc surface, the strain distribution curve is extracted, and the strain distribution law is verified to conform to the quadratic function characteristic by fitting the strain distribution curve.

[0027] Further, when the peak strain of the full-field strain distribution data on the blade back surface is less than or equal to the peak strain of the full-field strain distribution data on the blade disc surface, the blade disc surface is underestimated as the region where the maximum strain is distributed.

[0028] Extract the strain distribution curve and verify that the strain distribution law conforms to the quadratic function characteristic by fitting the strain distribution curve; Still further, the strain distribution curve contains multiple discrete strain data points; the quadratic function characteristic is that the strain value changes continuously along the blade root-blade tip direction, presenting a parabolic distribution, thereby determining that the maximum strain distribution has a continuous distribution characteristic in the blade root-blade tip direction; the continuous distribution characteristic provides a theoretical basis for subsequent interpolation calculation of the maximum strain position by a limited number of measurement points.

[0029] S2: Based on the central axis of the maximum strain distribution region on the blade back surface, paste resistance strain gauges at equal intervals along the blade root-blade tip direction, and record the distance from the center of the sensitive grid of the resistance strain gauge to the blade root; S2.1: Based on the full-field strain distribution data on the blade back surface, identify the central axis of the strain peak value distribution in the region where the maximum strain is distributed; It should be noted that the central axis is the connecting line of the strain peak value points along the blade root-blade tip direction; the central axis represents the one-dimensional path with the maximum strain in the region where the maximum strain is distributed.

[0030] S2.2: Determine the size specification of the sensitive grid of the resistance strain gauge according to the total length L of the blade root-blade tip direction of the blade 4 to be tested; Specifically, the sensitive gate size of the resistance strain gauge is not greater than 1 / 15 of the total length L in the blade root-blade tip direction; the limitation of the sensitive gate size avoids the averaging effect of the strain gauge with an excessively large size on the measurement of the strain gradient change region; and the limitation of the sensitive gate size reduces the influence of the additional mass of the resistance strain gauge and its lead wire on the vibration characteristics of the blade 4 to be tested.

[0031] In an optional embodiment, the total length L in the blade root-blade tip direction is 15 mm, and the sensitive gate length of the resistance strain gauge is 1 mm.

[0032] S2.3: On the central axis of the region where the maximum strain distribution is located, three equally spaced patch position points are determined, wherein the three equally spaced patch position points are sequentially marked as a first patch position point, a second patch position point, and a third patch position point from the blade root side to the blade tip side; Further, the first patch position point is located on the section close to the blade root on the central axis; the second patch position point is located on the middle section of the central axis; the third patch position point is located on the section close to the blade tip on the central axis; the intervals between the three equally spaced patch position points are equal; the interval is determined according to the span range of the region where the maximum strain distribution is located in the blade root-blade tip direction; and the interval is set to 1 / 3 to 1 / 2 of the span range.

[0033] S2.4: Surface pretreatment is performed on the patch area of the blade back surface; Still further, the surface pretreatment includes sequentially performed coarse grinding, fine grinding, cleaning, and drying operations; the coarse grinding uses coarse sandpaper to remove the oxidation layer and oil stains on the patch area of the blade back surface; the fine grinding uses fine sandpaper to polish the patch area of the blade back surface to a smooth state; the cleaning uses acetone or alcohol solvent to remove the residual impurities on the patch area of the blade back surface; and the drying uses natural air drying or a hair dryer to remove the residual solvent on the patch area of the blade back surface.

[0034] S2.5: Based on the pretreated patch area, the resistance strain gauges are pasted on the patch position points; It should be noted that the resistance strain gauges include the first resistance strain gauge , the second resistance strain gauge , and the third resistance strain gauge .

[0035] Specifically, the sensitive gate directions of the first resistance strain gauge , the second resistance strain gauge , and the third resistance strain gauge are parallel to the blade root-blade tip direction; during the pasting process, special strain gauge glue is applied to the back surface of the resistance strain gauges, the resistance strain gauges are pressed and pasted on the blade back surface and kept for 30 to 60 seconds, and the pasting is completed after the strain gauge glue is solidified.

[0036] S2.6: Measure the distance from the center of the sensitive grid of the resistance strain gauge to the edge of the blade root, and record it as the first distance. Second distance and the third distance ; Furthermore, the first distance First resistance strain gauge The distance from the center of the sensitive grid to the edge of the leaf root; the second distance For the second resistance strain gauge The distance from the center of the sensitive grid to the edge of the leaf root; the third distance The third resistance strain gauge The distance from the center of the sensitive grid to the edge of the leaf root.

[0037] It should be noted that the center of the sensitive grid is the geometric center point of the sensitive grid area of ​​the resistance strain gauge; the blade root edge is the starting boundary line of the contact between the blade root of the blade 4 to be tested and the fixture; the first distance Second distance and the third distance The measurement is performed using a vernier caliper or laser rangefinder, with a measurement accuracy of not less than 0.1 mm.

[0038] S2.7: Perform lead wire welding and insulation protection treatment on the resistance strain gauge; Furthermore, the lead wires are soldered to the lead-out ends of the resistance strain gauge using thin wires; the insulation protection involves covering the resistance strain gauge and solder joints with moisture-proof adhesive or insulating tape to prevent the influence of environmental humidity and vibration on the electrical performance of the resistance strain gauge; the other end of the lead wire is connected to the signal acquisition port of the strain measurement system 5 to complete the installation and recording of the resistance strain gauge.

[0039] S3: At the resonant frequency of the blade 4 to be tested, a constant amplitude dwell excitation is applied, and the strain value of the resistance strain gauge is collected by the strain measurement system 5. Specifically, such as Figure 6 As shown, an experiment was conducted based on a typical blade vibration fatigue testing system. This system includes a vibration controller 1, a displacement sensor 2, and a resistance strain gauge 3 (i.e.,...). Figure 5 middle , , ), 4. Blade to be tested, 5. Strain measurement system, 6. Power amplifier, 7. Accelerometer, 8. Fixture body, 9. Moving coil, and 10. Vibration table.

[0040] S3.1: Conduct blade vibration characteristic tests to obtain the resonant frequency; Further, the vibration level is preset in the upper computer software of the vibration controller 1, and a driving electric signal is generated; after the electric signal is amplified by the power amplifier 6, the moving coil 9 of the vibration table 10 is driven to generate vibration excitation of the set level; the vibration excitation is transmitted to the blade 4 to be tested through the rigidly connected clamping body 8, so that the forced vibration is generated.

[0041] It should be noted that the acceleration sensor 7 attached near the root of the clamping body 8 and the blade 4 to be tested collects the acceleration signal in real time and feeds back to the vibration controller 1; the vibration controller 1 corrects the vibration output of the vibration table 10 in real time according to the deviation of the input and output signals, so as to realize the closed-loop high-precision vibration level control.

[0042] Further, the displacement sensor 2 collects the blade tip amplitude signal in real time and transmits it to the vibration controller 1; the upper computer software of the vibration controller 1 processes the acceleration signal and the blade tip amplitude signal in real time, calculates the transmission relationship between the two, and thus obtains the resonance frequency and amplification factor and other vibration characteristic parameters of the blade 4 to be tested.

[0043] It should be noted that the clamping body 8 rigidly connects the blade root area of the blade 4 to be tested; the moving coil 9 of the vibration table and the clamping body 8 are rigidly connected by bolts; the rigid connection mode ensures that the vibration excitation is effectively transmitted from the vibration table to the blade 4 to be tested; the acceleration sensor 7 is used to monitor the acceleration signal of the root of the vibration table and the blade 4 to be tested in real time; the displacement sensor 2 is a non-contact laser displacement sensor 2 or an eddy current displacement sensor 2; the measurement beam or probe of the displacement sensor 2 is aligned with the end face of the blade tip area; the displacement sensor 2 is used to collect the blade tip amplitude signal of the blade 4 to be tested during the vibration process.

[0044] S3.2: Apply constant amplitude stationary excitation at the resonance frequency to carry out vibration stress distribution test; Specifically, based on the resonance frequency, the blade 4 to be tested is applied with constant amplitude stationary excitation; the strain measurement system 5 collects the strain electric signals of the first resistance strain gauge , the second resistance strain gauge and the third resistance strain gauge .

[0045] Further, the strain measurement system 5 processes and calculates the collected strain electric signals in real time, displays the vibration strain values, and records the first strain value , the second strain value and the third strain value respectively; wherein the first strain value corresponds to the measurement result of the first resistance strain gauge , the second strain value corresponds to the measurement result of the second resistance strain gauge the measurement result of the third strain value corresponding to the third resistance strain gauge the measurement result of the third strain value

[0046] In an optional embodiment, the blade tip amplitude target value is set to 2mm to 5mm, and the blade tip amplitude target value is set to avoid plastic deformation or fatigue damage of the blade 4 to be tested during the test.

[0047] S4: Based on the strain value and the distance, a matrix equation of the strain distribution quadratic function is constructed, the coefficients are solved by determinant calculation, and the strain distribution function is obtained; S4.1: Based on the continuous quadratic function distribution rule, a strain distribution quadratic function of the blade 4 to be tested along the blade root-blade tip direction is established , and the specific formula is as follows: ; Wherein, a, b and c are respectively the coefficients of the quadratic term, the linear term and the constant term of the quadratic function satisfying the strain distribution rule.

[0048] S4.2: Substitute the three groups of strain data 、 and obtained by the stress distribution test into the strain distribution quadratic function, and establish a three-order linear equation group, and the specific formula is as follows: ; Specifically, the three-order linear equation group is converted into a matrix equation, and the expression of the matrix equation is: ; That is, the above matrix equation is converted into the mathematical expression of the determinant as follows: ; Wherein, is the result of the determinant calculation of the matrix, which is a scalar.

[0049] According to the three groups of strain measurement data, the T value is calculated, and when T≠0, the formula is obtained: ; In an optional embodiment, since the first patch position point, the second patch position point and the third patch position point are equidistantly distributed, the discriminant value T must not be equal to zero.

[0050] S4.3: The Cramer rule is used to solve the quadratic coefficient a, the linear coefficient b and the constant coefficient c, and the strain distribution function is determined; Preferably, the specific formula of the strain distribution function is as follows: .

[0051] S5: calculating the distance between the maximum strain position point and the blade root according to the strain distribution function, and pasting a resistance strain gauge at the maximum strain position point for stress calibration measurement in the fatigue strength test.

[0052] Specifically, the maximum strain position point is calculated according to the following formula, and the specific formula is as follows: ; wherein, is the distance between the maximum strain position point and the blade root, is the maximum strain value corresponding to the maximum strain position point, and a, b and c are respectively the coefficients of the quadratic term, the linear term and the constant term of the quadratic function satisfying the strain distribution law.

[0053] Preferably, the image of the strain distribution function opens upward or degenerates into a linear function, indicating that the selection range of the first, second and third patch position points fails to cover the maximum strain position point, and the distribution positions of the first, second and third patch position points in the blade root-blade tip direction need to be adjusted until the quadratic term coefficient a is less than zero.

[0054] Further, when the quadratic term coefficient a of the quadratic function is greater than 0, the parabolic opening of the strain distribution function opens upward, and the maximum strain point cannot be calculated; for the case where the quadratic term coefficient a of the quadratic function is greater than 0, appropriate patch positions are selected again according to the simulation results, three groups of measurement values are obtained again, and the coefficient a value is calculated again until it is less than 0, and the method will be applicable. When the quadratic term coefficient a of the quadratic function is less than 0, the parabolic opening of the strain distribution function opens downward, and the maximum strain point position can be directly calculated .

[0055] In summary, the present application determines the maximum strain distribution area and continuity in the virtual space by full-field strain analysis of the blade through finite element simulation, fundamentally avoids the blindness of physical testing, and provides a theoretical basis and target area for subsequent actual measurement, especially solving the technical problem that the curved surface cannot be directly pasted; based on the simulation results, equal-interval pasting is performed along the central axis of the maximum strain area, the complex two-dimensional strain field measurement is simplified to one-dimensional linear sampling, and through a small number of measuring points, the cost of multi-channel instruments, process errors and system additional mass effects are significantly reduced; under the resonance condition, a steady-state excitation is applied and strain data is collected, ensuring the signal-to-noise ratio and repeatability of the working condition data; a strain distribution quadratic function model is constructed using the discrete measuring point data, and the coefficients are solved through matrix operation, realizing accurate extrapolation from limited data to continuous strain field, replacing the traditional empirical speculation with a mathematical model, and quantitatively reducing the measurement uncertainty; the maximum strain point is accurately positioned through function calculation and single-point calibration, so that subsequent fatigue tests do not need to rely on a large number of pastes to obtain accurate data at the most critical position, and the unity of test cost optimization and result reliability is realized.

[0056] The embodiment also provides a computer device suitable for the maximum strain position measurement and positioning method, including a memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions to realize the maximum strain position measurement and positioning method proposed in the above embodiment.

[0057] The computer device can be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected through a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operating system and the computer program in the non-volatile storage medium to run. The communication interface of the computer device is used to communicate with external terminals in a wired or wireless manner. The wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer overlaid on the display screen, or a key, trackball or touchpad arranged on the shell of the computer device. The input device of the computer device can also be an external keyboard, touchpad or mouse, etc.

[0058] The embodiment also provides a storage medium having a computer program stored thereon, and the program is executed by a processor to realize the maximum strain position measurement and positioning method proposed in the above embodiment.

[0059] The storage medium provided in the embodiment belongs to the same inventive concept as the data storage method provided in the above embodiment, and the technical details not described in detail in the embodiment can be referred to the above embodiment, and the embodiment has the same beneficial effects as the above embodiment.

[0060] Embodiment 2 Reference Figure 7 For the second embodiment of the application, the embodiment provides a regulation resource planning method considering risk prevention and control needs. In order to verify the beneficial effects of the application, economic benefit calculation and simulation experiments are used for scientific demonstration.

[0061] Specifically, the blade is a certain ten-stage rotor blade, the simulation shows that the maximum stress is distributed on the blade disc surface, close to the position of the blade root arc surface, and the stress distribution in the blade root-blade tip direction satisfies a quadratic function distribution relationship. Three strain monitoring points are selected in the strain change gentle area, which are 7mm, 9mm and 11mm away from the bottom of the tenon, and the strain results are measured based on the stress distribution test after the patching according to the requirements, as shown in Table 1.

[0062] Table 1, strain measurement results Paste position First resistance strain gauge Second resistance strain gauge Third resistance strain gauge Distance from tenon base (mm) 7 9 11 Strain measurement (με) 518.5 468.5 392.1 Further, according to step S4.2, the determinant is verified: .

[0063] Further, according to step S4.3, the coefficients a, b and c are calculated: Specifically, according to step S5, when the quadratic term coefficient a of the quadratic function is less than 0, the maximum strain point position and value are calculated according to the following formula: Further, in order to verify the accuracy of the method, the calculated maximum strain point position is compared with the maximum position determined by simulation analysis, and strain gauges are pasted for measurement, and the comparison results are shown in Table 2.

[0064] Table 2, comparison of method measurement data / Distance from tenon base Strain measurement The method 4.2 mm 537 με Simulation analysis 4.0 mm 501 με Contrast deviation 5.0% -7.2% Further, as shown in Figure 7 , 1 is the maximum strain position point given by simulation. Compared with the simulation results, the maximum strain position calculated by the method has a maximum position deviation of 5.0%, and the highest strain measurement deviation is-7.2%. The results show that the method can quickly and effectively locate the maximum strain position and obtain more accurate maximum strain measurement results.

[0065] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalent replaced without departing from the spirit and scope of the technical solutions of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A maximum strain location measurement and positioning method, characterized by: Comprising, A three-dimensional geometric model is established for the blade (4) to be tested, finite element simulation analysis is performed, full-field strain distribution rules of the blade face and the back face under a specified modal shape are obtained, and the region where the maximum strain distribution is located and the continuous distribution characteristics are determined; Based on the central axis of the maximum strain distribution region of the back face, resistance strain gauges are pasted at equal intervals along the blade root-blade tip direction, and the distance from the center of the sensitive grid of the resistance strain gauge to the blade root is recorded; At the resonance frequency of the blade (4) to be tested, a constant amplitude of the standing excitation is applied, and the strain values of the resistance strain gauges are collected through the strain measurement system (5); Based on the strain values and the distances, a matrix equation of the strain distribution quadratic function is constructed, the coefficients are solved through determinant calculation, and the strain distribution function is obtained; The distance from the maximum strain position point to the blade root is calculated according to the strain distribution function, and a resistance strain gauge is pasted at the maximum strain position point for stress calibration measurement of the fatigue strength test.

2. The maximum strain location measurement and positioning method of claim 1, wherein: The finite element simulation analysis comprises: Three-dimensional geometric size data of the blade (4) to be tested is obtained, and a three-dimensional geometric model is established; The three-dimensional geometric model is subjected to finite element mesh division, and fixed constraint boundary conditions and free boundary conditions are applied; The three-dimensional geometric model after the domain is subjected to conditions is subjected to modal analysis calculation, each order modal shape of the blade (4) to be tested in a specified working frequency range is extracted, and a target modal shape corresponding to the test working condition is selected; According to the target modal shape, stress and strain field calculation is performed, and blade face full-field strain distribution data and back face full-field strain distribution data of the blade (4) to be tested under the target modal shape are obtained.

3. The maximum strain location measurement and positioning method of claim 2, wherein: Further comprising, The blade face full-field strain distribution data and the back face full-field strain distribution data are compared and analyzed, when the peak strain of the back face full-field strain distribution data is greater than the peak strain of the blade face full-field strain distribution data, the strain distribution curve is extracted, and the strain distribution rule is verified to conform to the quadratic function characteristics by fitting the strain distribution curve.

4. The maximum strain location measurement and positioning method of claim 1, wherein: The resistance strain gauge includes a first resistance strain gauge bonded at equal intervals. Second resistance strain gauge and the third resistance strain gauge The first resistance strain gauge Second resistance strain gauge and the third resistance strain gauge The distance from the center of the sensitive grid to the edge of the leaf root is recorded as the first distance. Second distance and the third distance .

5. The maximum strain location measurement and positioning method of claim 1, wherein: The distance from the maximum strain position point to the blade root is calculated according to the strain distribution function, and the specific formula is as follows: ； wherein, is the distance from the maximum strain position point to the blade root, is the maximum strain value corresponding to the maximum strain position point, a, b and c are respectively the coefficients of the quadratic term, the linear term and the constant term of the quadratic function satisfying the strain distribution law.

6. The maximum strain location measurement and positioning method of claim 5, wherein: The method for obtaining the strain distribution function is, Based on the continuous quadratic function distribution rule, a strain distribution quadratic function of the blade (4) to be tested along the blade root-blade tip direction is established; Three sets of strain data obtained from stress distribution test , and Substituting the quadratic function of strain distribution into the equations, we establish a system of three linear equations in three variables. The Cramer's rule is used to solve the quadratic term coefficient a, the linear term coefficient b and the constant term coefficient c, and the strain distribution function is determined. 7.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is characterized in that: The processor executes the computer program to realize the steps of the maximum strain position measurement and positioning method of any one of claims 1-6.

8. A computer readable storage medium having stored thereon a computer program, characterized in that: The computer program is executed by the processor to realize the steps of the maximum strain position measurement and positioning method of any one of claims 1-6.

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