Blade vibration fatigue test analysis method and system

Abstract

The present application relates to the technical field of aero-engine, and discloses a kind of blade vibration fatigue test analysis method and system, by using the way of gradient stress test to the vibration fatigue test analysis of the multiple test blades of the test blade type, obtain the test stress value before the crack of corresponding test blade under each test stress and the cycle number when crack occurs, to this analysis obtains the fatigue strength of each test blade;Finally, mathematical statistics is introduced, according to the fatigue strength of each test blade, the number of test blades and test stress gradient, the test results are analyzed, and the statistical minimum fatigue strength of the test blade type is obtained.The test sample required by the step method is less, generally only 3-6 test blades are used as test samples, and the fatigue limit test results obtained by the pass method are more accurate, which is suitable for the case that the test sample is less and the fatigue limit accuracy is high.

Description

Technical Field

[0001] The invention relates to the technical field of aero-engines and discloses a blade vibration fatigue test analysis method and system. Background Art

[0002] Vibration fatigue testing of blades is an important means to obtain the fatigue performance of components, and is also an important link in supporting the design of blades to resist high-cycle fatigue.

[0003] Traditional vibration fatigue testing typically uses the lift method to determine the blade fatigue limit and the passability method to verify the minimum fatigue limit. The lift method requires a relatively large number of test specimens, and the minimum fatigue limit obtained using the passability method may deviate significantly from the actual fatigue limit. However, during aircraft engine development, constraints such as development cycles, production schedules, and iterative design often result in a limited number of test specimens and relatively high accuracy requirements, making it impossible to use existing testing methods. Summary of the Invention

[0004] The purpose of the present invention is to provide a blade vibration fatigue test analysis method and system. By adopting the step method to perform blade vibration fatigue limit analysis, fewer test samples are required, and the fatigue limit test results are more accurate than those obtained by the pass method. It is suitable for situations where there are fewer test samples and high fatigue limit accuracy requirements.

[0005] In order to achieve the above technical effects, the technical solution adopted by the present invention is:

[0006] A blade vibration fatigue test analysis method, comprising:

[0007] The required number of cycles, initial stress value and stress gradient of vibration fatigue test for a given test blade profile;

[0008] Performing vibration fatigue test analysis on multiple test blades of the test blade profile using a gradient stress test method to obtain the test stress value before cracks occur in the corresponding test blade under each test stress, as well as the number of cycles when cracks occur;

[0009] Analyze and obtain the fatigue strength of each test blade based on the test stress value before cracking of the test blade, the required number of cycles, the stress gradient, and the number of cycles when cracking occurs;

[0010] The statistical minimum fatigue strength of the test blade profile is obtained through analysis based on the fatigue strength of each test blade, the number of test blades, and the test stress gradient.

[0011] Furthermore, the initial stress σ0 is determined according to the tensile limit σ of the test blade material. b And the stress concentration degree K of the test blade assessment partt Determine; among which:

[0012] When 1≤K t <2, σ0=0.4σ b ;

[0013] When 2≤K t When <3, σ0=0.25σ b ;

[0014] When K t ≥3, σ0=0.1σ b ;

[0015] The test parts include the blade root, the leading edge of the blade and the trailing edge of the blade.

[0016] Furthermore, the stress gradient is 1% to 10% of the initial stress; and starting from the initial stress, the test is carried out for the required number of cycles. If no cracks occur in the blade after the required number of cycles, a stress gradient is added and the test is continued for the required number of cycles until cracks occur in the blade, and the test is stopped. If cracks occur in the blade at the initial stress, the initial stress is reduced by two stress gradients and the test is restarted.

[0017] Furthermore, the fatigue strength of the test blade is tested according to Analytically obtained, where σ f is the fatigue strength of the test blade, C is the required number of cycles, C n is the number of cycles when cracks occur, σ n-1 is the test stress value before cracks occur in the test blade, Δσ is the stress gradient, and b ranges from 0 to 3.

[0018] Furthermore, the statistical minimum fatigue strength of the test blade is based on Analytically obtained, where σ P is the statistical minimum fatigue strength of the test blade, is the average fatigue strength of the test blades, m is the number of test blades, Δσ is the stress gradient; V is 1 or 1.5, if Then V is 1.5, if Then V takes the value of 1.

[0019] To achieve the above technical effects, the present invention also provides a blade vibration fatigue test analysis system, comprising:

[0020] A data acquisition module is used to obtain the required number of cycles, initial stress value and stress gradient of the vibration fatigue test of the test blade;

[0021] a data acquisition module for performing a vibration fatigue test analysis on a plurality of test blades of the test blade profile using a gradient stress test method, and obtaining a test stress value before cracks are generated in the corresponding test blade under each test stress, and a number of cycles when cracks are generated;

[0022] A first analysis module is configured to analyze and obtain the fatigue strength of each test blade based on the test stress value before cracks occur in the test blade, the required number of cycles, the stress gradient, and the number of cycles when cracks occur;

[0023] The second analysis module is used to analyze and obtain the statistical minimum fatigue strength of the test blade profile according to the fatigue strength of each test blade, the number of test blades and the test stress gradient.

[0024] Furthermore, in the data acquisition module, the initial stress σ0 is calculated based on the tensile limit σ of the test blade material. b And the stress concentration degree K of the test blade assessment part t Determine; among which:

[0025] When 1≤K t <2, σ0=0.4σ b ;

[0026] When 2≤K t When <3, σ0=0.25σ b ;

[0027] When K t ≥3, σ0=0.1σ b ;

[0028] The test parts include the blade root, the leading edge of the blade and the trailing edge of the blade.

[0029] Furthermore, in the data acquisition module, the stress gradient is 1% to 10% of the initial stress; and starting from the initial stress, the test is performed according to the required number of cycles. If no cracks are generated in the blade after the required number of cycles, a stress gradient is added and the test is continued according to the required number of cycles until cracks are generated in the blade, and the test is stopped. If cracks are generated in the blade at the initial stress, the initial stress is reduced by two stress gradients and the test is restarted.

[0030] Furthermore, in the first analysis module, the fatigue strength of the test blade is determined according to Analytically obtained, where σ f is the fatigue strength of the test blade, C is the required number of cycles, C n is the number of cycles when cracks occur, σ n-1 is the test stress value before cracks occur in the test blade, Δσ is the stress gradient, and b ranges from 0 to 3.

[0031] Furthermore, in the second analysis module, the statistical minimum fatigue strength of the test blade is calculated based on Analytically obtained, where σ P is the statistical minimum fatigue strength of the test blade, is the average fatigue strength of the test blades, m is the number of test blades, Δσ is the stress gradient; V is 1 or 1.5, if Then V is 1.5, if Then V takes the value of 1.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention introduces mathematical statistics and analyzes the test results according to the fatigue strength of each test blade, the number of test blades and the test stress gradient to obtain the statistical minimum fatigue strength of the test blade profile.

[0034] 2. The step method adopted in the present invention requires fewer test samples, generally only 3 to 6 test blades are needed as test samples. Compared with the fatigue limit test results obtained by the pass method, it is more accurate and suitable for situations where there are fewer test samples and high fatigue limit accuracy requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of the blade vibration fatigue test analysis method in the embodiment;

[0036] Figure 2 This is a structural block diagram of the blade vibration fatigue test analysis system in the embodiment;

[0037] Among them, 1. Data acquisition module; 2. Data collection module; 3. First analysis module; 4. Second analysis module. DETAILED DESCRIPTION

[0038] The present invention will be described in further detail below with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the present invention to the following embodiments, as all technologies implemented based on the present invention fall within the scope of the present invention.

[0039] Example 1

[0040] See also Figure 1 and Figure 2 , a blade vibration fatigue test analysis method, comprising:

[0041] The required number of cycles, initial stress value and stress gradient of vibration fatigue test for a given test blade profile;

[0042] Performing vibration fatigue test analysis on multiple test blades of the test blade profile using a gradient stress test method to obtain the test stress value before cracks occur in the corresponding test blade under each test stress, as well as the number of cycles when cracks occur;

[0043] Analyze and obtain the fatigue strength of each test blade based on the test stress value before cracking of the test blade, the required number of cycles, the stress gradient, and the number of cycles when cracking occurs;

[0044] The statistical minimum fatigue strength of the test blade profile is obtained through analysis based on the fatigue strength of each test blade, the number of test blades, and the test stress gradient.

[0045] In this embodiment, given the required number of cycles, initial stress value, and stress gradient for a given test blade profile, a vibration fatigue test analysis is performed on multiple test blades of the test blade profile using a gradient stress test. The test stress value before cracking and the number of cycles until cracking occur are obtained for each test stress, thereby analyzing the fatigue strength of each test blade. Finally, mathematical statistics are introduced to analyze the test results based on the fatigue strength of each test blade, the number of test blades, and the test stress gradient, to obtain the statistical minimum fatigue strength of the test blade profile. The step-by-step method employed in this invention requires fewer test specimens, typically only 3 to 6 test blades. Compared to the fatigue limit test results obtained using the pass method, this method is more accurate and is suitable for situations where fewer test specimens are required and high fatigue limit accuracy is required.

[0046] Based on the same inventive concept, this embodiment also provides a blade vibration fatigue test analysis system, including:

[0047] Data acquisition module 1, used to obtain the required number of cycles, initial stress value and stress gradient of the vibration fatigue test of the test blade;

[0048] Data acquisition module 2 is used to perform vibration fatigue test analysis on multiple test blades of the test blade profile using a gradient stress test method to obtain the test stress value before cracks are generated in the corresponding test blade under each test stress, as well as the number of cycles when cracks are generated;

[0049] A first analysis module 3 is configured to analyze and obtain the fatigue strength of each test blade based on the test stress value before cracks occur in the test blade, the required number of cycles, the stress gradient, and the number of cycles when cracks occur;

[0050] The second analysis module 4 is configured to analyze and obtain the statistical minimum fatigue strength of the test blade profile according to the fatigue strength of each test blade, the number of test blades, and the test stress gradient.

[0051] Example 2

[0052] See also Figure 1 , a blade vibration fatigue test analysis method, comprising:

[0053] Step 1: The required number of cycles, initial stress value and stress gradient of the vibration fatigue test of the given test blade are given;

[0054] In this embodiment, depending on the blade material, the prescribed number of cycles C are:

[0055] Steel parts (including nickel-based high-temperature alloys): 10 7 cycle;

[0056] Non-ferrous metal alloy parts: 3×10 7 cycle;

[0057] Titanium alloy: 10 9 Cycle (in actual test, 3×10 7 cycle, taking a 0.9 factor based on the test results).

[0058] In addition, the initial stress σ0 is determined according to the tensile strength limit σ of the test blade material. b And the stress concentration degree K of the test blade assessment part t Determine; among which:

[0059] When 1≤K t <2, σ0=0.4σ b ;

[0060] When 2≤K t When <3, σ0=0.25σ b ;

[0061] When K t ≥3, σ0=0.1σ b ;

[0062] The test parts include the blade root, the leading edge of the blade and the trailing edge of the blade.

[0063] Step 2: Performing a vibration fatigue test analysis on multiple test blades of the test blade profile using a gradient stress test method to obtain the test stress value before cracks are generated in the corresponding test blade under each test stress, as well as the number of cycles when cracks are generated;

[0064] In this embodiment, the stress gradient is 1% to 10% of the initial stress. Starting from the initial stress, the test is performed for the required number of cycles. If no cracks occur in the blade after the required number of cycles, the test is continued for the required number of cycles with an increased stress gradient until cracks occur in the blade, at which point the test is terminated. If cracks occur in the blade at the initial stress, the initial stress is reduced by two stress gradients, the test is restarted, and the test stress value (the previous gradient stress value) before cracks occur in the corresponding test blade under the test stress is recorded.

[0065] Step 3: Analyze and obtain the fatigue strength of each test blade based on the test stress value before cracking of the test blade, the required number of cycles, the stress gradient, and the number of cycles when cracking occurs;

[0066] In this embodiment, the damage accumulation method is used to calculate the test fatigue strength σ of each sample. f , it is necessary to consider at least two stress gradients that damage the blade. Therefore, the fatigue strength of the test blade is based on Analytically obtained, where σ f is the fatigue strength of the test blade, C is the required number of cycles, C n is the number of cycles when cracks occur, σ n-1 is the test stress before cracks in the blade, Δσ is the stress gradient, and b ranges from 0 to 3. The fatigue strength calculation takes into account the effects of the low-stress portion of the cycle, resulting in better accuracy for materials sensitive to damage accumulation, such as titanium and aluminum alloys.

[0067] Step 4: Analyze and obtain the statistical minimum fatigue strength of the test blade profile based on the fatigue strength of each test blade, the number of test blades, and the test stress gradient;

[0068] In this embodiment, the statistical minimum fatigue strength of the test blade is based on Analytically obtained, where σ P is the statistical minimum fatigue strength of the test blade, is the average fatigue strength of the test blades, m is the number of test blades, Δσ is the stress gradient; V is 1 or 1.5, if Then V is 1.5, if Then V takes the value of 1. This statistical minimum fatigue strength calculation takes into account the dispersion of blade test results, resulting in a minimum fatigue limit value for the blade, which can be used for test result verification and vibration reserve analysis. Furthermore, the multiple effects of the number of test blades, the average fatigue strength value, and the test stress gradient are considered, enabling the accurate statistical minimum fatigue strength value of the test blade profile to be obtained with fewer test specimens. In particular, a result equivalent to a 50% confidence level -3 sigma value can be obtained with only six test specimens, whereas the traditional lift method requires at least 12 specimens to achieve this result.

[0069] It should be noted that while the blade vibration fatigue test analysis method of this embodiment is applicable to situations where there are fewer test specimens and high fatigue limit accuracy is required, in actual engineering testing, it is recommended to complete at least three specimen tests to obtain the median fatigue strength, and at least six specimen tests to obtain the safety fatigue strength.

[0070] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A blade vibration fatigue test analysis method, characterized in that: include: The required number of cycles, initial stress value and stress gradient of vibration fatigue test for a given test blade profile; Performing vibration fatigue test analysis on multiple test blades of the test blade profile using a gradient stress test method to obtain the test stress value before cracks occur in the corresponding test blade under each test stress, as well as the number of cycles when cracks occur; The fatigue strength of each test blade is obtained by analyzing the test stress value before the crack occurs, the required number of cycles, the stress gradient, and the number of cycles when the crack occurs. ,in To test the fatigue strength of the blade, To request the number of cycles, is the number of cycles when cracks occur, is the test stress value before cracks occur in the test blade, is the stress gradient, The value ranges from 0 to 3; According to the fatigue strength of each test blade, the number of test blades and the test stress gradient, the statistical minimum fatigue strength of the test blade is obtained by analysis. The statistical minimum fatigue strength of the test blade is obtained according to The analysis obtained is the statistical minimum fatigue strength of the test blade, is the average fatigue strength of the test blade, is the number of test leaves, is the stress gradient; The value is 1 or 1.

5. ,but The value is 1.5, if ,but The value is 1.

2. The blade vibration fatigue test analysis method according to claim 1, characterized in that: The initial stress According to the tensile limit of the blade material And the stress concentration degree of the test blade assessment part Determine; among which: When 1≤ <2 o'clock, =0.4 ; When 2≤ <3 o'clock, =0.25 ; when ≥3, =0.1 ; The test parts include the blade root, the leading edge of the blade and the trailing edge of the blade.

3. The blade vibration fatigue test analysis method according to claim 1, characterized in that: The stress gradient is 1% to 10% of the initial stress; and starting from the initial stress, the test is carried out for the required number of cycles. If no cracks occur in the blade after the required number of cycles, a stress gradient is added and the test is continued for the required number of cycles until cracks occur in the blade, and the test is stopped. If cracks occur in the blade at the initial stress, the initial stress is reduced by two stress gradients and the test is restarted.

4. A blade vibration fatigue test analysis system, characterized in that: include: A data acquisition module is used to obtain the required number of cycles, initial stress value and stress gradient of the vibration fatigue test of the test blade; a data acquisition module for performing a vibration fatigue test analysis on a plurality of test blades of the test blade profile using a gradient stress test method, and obtaining a test stress value before cracks are generated in the corresponding test blade under each test stress, and a number of cycles when cracks are generated; The first analysis module is used to analyze and obtain the fatigue strength of each test blade based on the test stress value before the test blade cracks, the required number of cycles, the stress gradient, and the number of cycles when the cracks occur. ,in To test the fatigue strength of the blade, To request the number of cycles, is the number of cycles when cracks occur, is the test stress value before cracks occur in the test blade, is the stress gradient, The value ranges from 0 to 3; The second analysis module is used to analyze and obtain the statistical minimum fatigue strength of the test blade according to the fatigue strength of each test blade, the number of test blades and the test stress gradient; the statistical minimum fatigue strength of the test blade is based on The analysis obtained is the statistical minimum fatigue strength of the test blade, is the average fatigue strength of the test blade, is the number of test leaves, is the stress gradient; The value is 1 or 1.

5. ,but The value is 1.5, if ,but The value is 1.

5. The blade vibration fatigue test and analysis system according to claim 4, characterized in that: In the data acquisition module, the initial stress According to the tensile limit of the blade material And the stress concentration degree of the test blade assessment part Determine; among which: When 1≤ <2 o'clock, =0.4 ; When 2≤ <3 o'clock, =0.25 ; when ≥3, =0.1 ; The test parts include the blade root, the leading edge of the blade and the trailing edge of the blade.

6. The blade vibration fatigue test and analysis system according to claim 4, characterized in that: In the data acquisition module, the stress gradient is 1% to 10% of the initial stress; and starting from the initial stress, the test is performed according to the required number of cycles. If no cracks are generated in the blade after the required number of cycles, a stress gradient is added and the test is continued according to the required number of cycles until cracks are generated in the blade, and the test is stopped. If cracks are generated in the blade at the initial stress, the initial stress is reduced by two stress gradients and the test is restarted.

Images