Blade vibration fatigue test analysis method and system

Abstract

The invention relates to the technical field of aero-engines, and discloses a blade vibration fatigue test analysis method and system, and the method comprises the steps: carrying out the vibration fatigue test analysis of a plurality of test blades of a test blade type in a gradient stress test mode; obtaining a test stress value before the corresponding test blade generates cracks under each test stress and a cycle index when the cracks are generated, and analyzing to obtain the fatigue strength of each test blade; and finally, mathematical statistics is introduced, a test result is analyzed according to the fatigue strength of each test blade, the number of the test blades and the test stress gradient, and the lowest statistical fatigue strength of the test blade profile is obtained. According to the method, fewer test samples are needed by the stepping method, generally, only 3-6 test blades are needed as the test samples, compared with a trafficability method, the obtained fatigue limit test result is more accurate, and the method is suitable for the conditions that the number of the test samples is small, and the fatigue limit precision requirement is high.

Description

Technical Field

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

[0002] The vibration fatigue test of blades is an important means to obtain the fatigue performance of components, and is also an important link in supporting the high-cycle fatigue resistance design of blades.

[0003] Traditional vibration fatigue tests generally use the lifting method to obtain the fatigue limit of the blade, and the passability method to test the minimum fatigue limit of the blade. The lifting method requires relatively more test specimens, and the minimum fatigue limit result taken by the passability method may deviate greatly from the actual fatigue limit. In the process of aircraft engine development, due to the constraints of development cycle, production schedule and iterative design, there are often fewer test specimens and relatively high requirements for result accuracy, and the existing methods cannot be used for testing. 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] A vibration fatigue test analysis is performed on multiple test blades of the test blade type by 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, and the number of cycles when cracks are generated;

[0009] Analyze and obtain the fatigue strength of each test blade according to 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;

[0010] 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 profile is analyzed and obtained.

[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 locations include the blade root, the leading edge of the blade body and the trailing edge of the blade body.

[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 a 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 blades was 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.

[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 tested blade type, 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. Then V is 1.5, if Then V takes the value of 1.

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

[0020] A data acquisition module, 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 is used to perform vibration fatigue test analysis on multiple test blades of the test blade type by 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, and the number of cycles when cracks are generated;

[0022] A first analysis module is used to analyze and obtain the fatigue strength of each test blade according to 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;

[0023] The second analysis module is used to analyze and obtain the statistical minimum fatigue strength of the test blade type 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 locations include the blade root, the leading edge of the blade body and the trailing edge of the blade body.

[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 tested blade type, 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. Then V is 1.5. 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, analyzes the test results according to the fatigue strength of each test blade, the number of test blades and the test stress gradient, and obtains the statistical minimum fatigue strength of the test blade type.

[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 It is a flow chart of the blade vibration fatigue test analysis method in the embodiment;

[0036] Figure 2 It 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 is further described in detail below in conjunction with the embodiments and drawings. However, it should not be understood that the scope of the above subject matter of the present invention is limited to the following embodiments, and all technologies realized based on the content of the present invention belong to 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] A vibration fatigue test analysis is performed on multiple test blades of the test blade type by 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, and the number of cycles when cracks are generated;

[0043] Analyze and obtain the fatigue strength of each test blade according to 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;

[0044] 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 profile is analyzed and obtained.

[0045] In this embodiment, under the conditions of the required number of cycles, initial stress value and stress gradient of the vibration fatigue test of a given test blade type, a vibration fatigue test analysis is performed on multiple test blades of the test blade type by adopting a gradient stress test method, and the test stress value before the crack of the corresponding test blade under each test stress and the number of cycles when the crack is generated are obtained, so as to analyze and obtain the fatigue strength of each test blade; finally, mathematical statistics are introduced, and the test results are analyzed according to the fatigue strength of each test blade, the number of test blades and the test stress gradient, so as to obtain the statistical minimum fatigue strength of the test blade type. The step method adopted by the present invention requires fewer test samples, generally only 3 to 6 test blades are required as test samples, and the fatigue limit test results obtained by the pass method are more accurate, which is suitable for the situation where there are fewer test samples and high fatigue limit accuracy requirements.

[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] The data acquisition module 2 is used to perform vibration fatigue test analysis on multiple test blades of the test blade type by using a gradient stress test method, and 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] The first analysis module 3 is used to analyze and obtain the fatigue strength of each test blade according to the test stress value before the test blade cracks, the required number of cycles, the stress gradient and the number of cycles when cracks occur;

[0050] The second analysis module 4 is used to analyze and obtain the statistical minimum fatigue strength of the test blade type 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: Given the required number of cycles, initial stress value and stress gradient of the vibration fatigue test of the test blade;

[0054] In this embodiment, according to different blade materials, 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 (3×10 7 cycle, taking 0.9 times coefficient according to test results).

[0058] In addition, the initial stress σ0 is 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:

[0059] When 1≤K t <2,σ0=0.4σ b ;

[0060] When 2≤K t <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: Perform vibration fatigue test analysis on multiple test blades of the test blade type by 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 according to the required number of cycles. If the blade does not crack after the required number of cycles, a stress gradient is added and the test is continued according to the required number of cycles until the blade cracks. The test is stopped. If the blade cracks at the initial stress, the initial stress is reduced by two stress gradients, the test is restarted, and the test stress value (previous gradient stress value) before the crack occurs in the corresponding test blade under the test stress is recorded.

[0065] Step 3, analyzing and obtaining the fatigue strength of each test blade according to 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;

[0066] In this embodiment, the damage accumulation method is used to calculate the test fatigue strength σ of each sample. f , at least two stress gradients must be considered to 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 value before cracks occur in the test blade, Δσ is the stress gradient, and b is 0 to 3. The calculation of fatigue strength takes into account the influence of the low stress cycle part, and has better calculation accuracy for materials such as titanium alloy and aluminum alloy that are sensitive to damage accumulation.

[0067] Step 4: Analyze and obtain the statistical minimum fatigue strength of the test blade type according to 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 tested blade type, 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. Then V is 1.5. Then V takes the value of 1. The calculation of the statistical minimum fatigue strength takes into account the dispersion of the blade test results, and the minimum fatigue limit value of the blade can be obtained, which can be used for test result verification and vibration reserve analysis. In addition, the multiple effects of the number of test blades, the average fatigue strength value, and the test stress gradient are also considered, and the statistical minimum fatigue strength value of the test blade with higher accuracy can be obtained under the condition of fewer test specimens. In particular, a result equivalent to a 50% confidence level -3 sigma value can be obtained under the condition of 6 test specimens, while the traditional lifting method requires at least 12 pieces to obtain this result.

[0069] It should be noted that although the blade vibration fatigue test analysis method of this embodiment can be applied to the situation where there are fewer test samples and the fatigue limit accuracy is required to be high. However, in the actual engineering test process, in order to obtain the median fatigue strength, it is recommended to complete at least 3 sample tests; in order to obtain the safety fatigue strength, it is recommended to complete at least 6 sample tests.

[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 protection scope 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; A vibration fatigue test analysis is performed on multiple test blades of the test blade type by 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, and the number of cycles when cracks are generated; Analyze and obtain the fatigue strength of each test blade according to 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; 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 profile is analyzed and obtained.

2. The blade vibration fatigue test analysis method according to claim 1, characterized in that: The initial stress σ0 is 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 Sure; in: When 1≤K t <2,σ0=0.4σ b ; When 2≤K t When <3,σ0=0.25σ b ; When K t ≥3,σ0=0.1σ b ; The test locations include the blade root, the leading edge of the blade body and the trailing edge of the blade body.

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 according to 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 according to 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. The blade vibration fatigue test analysis method according to claim 3, characterized in that: 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 value before cracks occur in the test blade, Δσ is the stress gradient, and b ranges from 0 to 3.

5. The blade vibration fatigue test analysis method according to claim 1, characterized in that: The statistical minimum fatigue strength of the tested blade type is based on Analytically obtained, where σ P is the statistical minimum fatigue strength of the tested blade type, 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. Then V is 1.

5. Then V takes the value of 1.

6. A blade vibration fatigue test analysis system, characterized in that: include: A data acquisition module, 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 is used to perform vibration fatigue test analysis on multiple test blades of the test blade type by 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, and the number of cycles when cracks are generated; A first analysis module is used to analyze and obtain the fatigue strength of each test blade according to the test stress value before the test blade generates cracks, the required number of cycles, the stress gradient, and the number of cycles when cracks are generated; The second analysis module is used to analyze and obtain the statistical minimum fatigue strength of the test blade type according to the fatigue strength of each test blade, the number of test blades and the test stress gradient.

7. The blade vibration fatigue test and analysis system according to claim 6, characterized in that: 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 Sure; in: When 1≤K t <2,σ0=0.4σ b ; When 2≤K t When <3,σ0=0.25σ b ; When K t ≥3,σ0=0.1σ b ; The test locations include the blade root, the leading edge of the blade body and the trailing edge of the blade body.

8. The blade vibration fatigue test and analysis system according to claim 6, 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 carried out according to 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 according to 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.

9. The blade vibration fatigue test and analysis system according to claim 8, characterized in that: In the first analysis module, 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 value before cracks occur in the test blade, Δσ is the stress gradient, and b ranges from 0 to 3.

10. The blade vibration fatigue test analysis system according to claim 6, characterized in that: In the second analysis module, 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 tested blade type, 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. Then V is 1.5, if Then V takes the value of 1.

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