A method for designing a test sample for evaluating blade vibration fatigue performance

Abstract

The application discloses a kind of blade vibration fatigue performance evaluation test sample design methods, comprising: target real blade model is carried out service state vibration simulation analysis, and the position of fatigue crack initiation, i.e. dangerous area is determined;The cross-sectional profile of dangerous area is measured, and at least including local thickness and arc radius Key geometric parameters are obtained;Based on the key geometric parameters obtained, a single-sided notched plate fatigue specimen model for laboratory is constructed;The consistency of the stress concentration factor of the sample test area and the stress concentration factor of the target area is verified.The application accurately locates the dangerous area through service state vibration simulation analysis, extracts the key geometric parameters and maps them to the sample, and ensures the consistency of the stress concentration factor through geometric equivalent stress criterion, realizes the accurate reproduction of failure mechanism, and significantly improves the confidence of vibration fatigue performance evaluation result.

Description

Technical Field

[0001] This invention relates to the field of research and development and remanufacturing technology for high-end equipment such as aero-engines and gas turbines, and specifically to a method for designing test specimens for evaluating the vibration fatigue performance of blades. Background Technology

[0002] In high-end equipment manufacturing fields such as aerospace and energy, key rotating components like turbine blades are subjected to multi-physical field coupled loads such as centrifugal force and aerodynamic excitation force during service. Their vibration fatigue performance directly affects the reliability and safety of the equipment. To assess the fatigue life of these components under complex service environments, laboratory fatigue tests are typically required. However, due to the complexity and high cost of real blade structures, conducting full-scale component fatigue tests is too expensive and difficult to implement. Therefore, designing laboratory specimens that can represent the fatigue characteristics of key blade components has become a common solution in the industry.

[0003] Existing specimen design methods are mostly based on empirical formulas or standard specifications, focusing on material-level performance testing and often neglecting the complex geometric features and service load environment of the critical areas of real blades. For example, when evaluating the vibration fatigue performance of blades, the geometry of standard specimens differs significantly from the local structure of the critical areas of real blades, resulting in inconsistencies between the stress concentration state in the specimen's testing area and that of the real blade. This difference in geometric features leads to significant deviations in the crack initiation location and propagation mechanism of laboratory specimens from those of real blades. Consequently, fatigue performance evaluation results based on standard specimens fail to accurately reflect the failure behavior of blades under actual service environments, resulting in low confidence levels and an inability to provide accurate data support for blade process optimization (such as surface strengthening and repair processes). Furthermore, existing methods lack a verification step to confirm the consistency of stress concentration coefficients between the specimen and the critical areas of the blade, making it impossible to quantitatively confirm the equivalence of the specimens and further reducing the reliability of the evaluation results. Summary of the Invention

[0004] To address the issues of low accuracy in evaluation results caused by the disconnect between the design of the test specimens and the actual vibration fatigue failure mechanism of blades, as well as the lack of consistency verification of stress concentration factors in existing technologies, this application proposes a test specimen design method for evaluating the vibration fatigue performance of blades. Based on vibration simulation analysis under service conditions, the method accurately locates the critical area, extracts key geometric parameters and maps them to the specimen, and verifies the consistency of stress concentration factors to ensure that the failure mechanism of the specimen and the critical area of ​​the blade are equivalent, thereby achieving a high degree of confidence in the vibration fatigue performance evaluation results.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for designing test specimens for evaluating the vibration fatigue performance of blades includes: performing service-state vibration simulation analysis on a target real blade model to determine the initiation location of fatigue cracks, i.e., the critical area; measuring the cross-sectional profile of the critical area to obtain key geometric parameters, including at least local thickness and radius of curvature; and constructing a single-notch plate-shaped fatigue specimen model for laboratory use based on the obtained key geometric parameters. By accurately locating the fatigue crack initiation location of the blade through service-state vibration simulation analysis and extracting the key geometric parameters of the critical area and mapping them to the specimen model, the consistency of the stress concentration state between the specimen testing area and the critical area of ​​the blade is ensured, achieving accurate reproduction of the failure mechanism.

[0007] As one implementation method, the vibration simulation analysis of the target real blade model under service conditions specifically includes: establishing an initial three-dimensional model of the component; setting the operating speed of the initial three-dimensional model of the component and applying a simple harmonic aerodynamic excitation force under the first-order vibration mode, and performing modal superposition harmonic response analysis; based on the equivalent stress distribution cloud map of the initial three-dimensional model obtained from the analysis, identifying the alternating stress concentration area as the dangerous area of ​​vibration fatigue, and obtaining the spatial coordinates of the fatigue crack initiation location in this dangerous area through the coordinate query function. Through modal superposition harmonic response analysis, the coupling effect of centrifugal force and aerodynamic excitation force is comprehensively considered, which can accurately identify the alternating stress concentration area of ​​the blade under actual service conditions, and accurately locate the dangerous area through spatial coordinates, providing a clear location basis for subsequent geometric parameter extraction.

[0008] As one implementation method, the service condition simulation analysis includes a combination of modal stress, centrifugal force, and airflow excitation force analysis to simulate the actual service environment of the blade. It provides a variety of simulation analysis methods for selection, allowing for flexible configuration of the method for determining the critical area based on the actual service conditions of the blade.

[0009] As one implementation method, the method further includes verifying the consistency between the stress concentration coefficient of the test area of ​​the plate-shaped fatigue specimen model and the stress concentration coefficient of the target area: obtaining the blade critical area of ​​the blade model and the clamping area of ​​the plate-shaped fatigue specimen model, and performing mesh generation; based on the mesh generation, applying loads to the blade critical area of ​​the blade model and the clamping area of ​​the plate-shaped fatigue specimen model respectively; after applying the load, obtaining the theoretical stress concentration coefficient of the blade critical area and the theoretical stress concentration coefficient at the specimen transition fillet; comparing the theoretical stress concentration coefficient of the blade critical area and the theoretical stress concentration coefficient at the specimen transition fillet, if the relative error between the two is less than a preset threshold, then it is determined that the stress concentration state of the specimen model is consistent with that of the actual blade critical area. Quantitatively verifying the consistency of the stress concentration coefficient between the specimen and the blade critical area through finite element analysis provides an objective numerical criterion for the equivalence of the specimen, eliminates the subjectivity and blindness of specimen design, and ensures the reliability of the fatigue performance evaluation results.

[0010] As one implementation method, applying loads to the blade critical area of ​​the blade model and the clamping area of ​​the plate fatigue specimen model respectively includes: applying a local vibration load boundary condition equivalent to the actual operating condition to the blade critical area of ​​the meshed blade model within the critical point threshold range; and applying a bending load equivalent to the blade vibration mode within the clamping area threshold range of the meshed plate fatigue specimen model. By applying vibration loads equivalent to the actual blade operating condition and bending loads equivalent to the blade vibration mode respectively, the comparison of stress concentration factors is ensured to be based on load equivalence, thus improving the accuracy of the verification results.

[0011] As one implementation method, when verifying the consistency between the stress concentration factor of the test area and the stress concentration factor of the target area of ​​the plate-shaped fatigue specimen model, the method further includes: setting a thinning region in the gauge length of the plate-shaped fatigue specimen model, wherein the minimum thickness of the thinning region is less than the thickness of the clamping region, to ensure that fracture occurs in the thinning region; the geometric definition of the thinning region follows the geometric equivalent stress criterion; based on the geometric equivalent stress criterion, the consistency between the stress concentration factor of the test area and the stress concentration factor of the target area is verified. The geometric equivalent stress criterion is introduced as the core theoretical basis for specimen design. The geometric definition of the thinning region ensures that the stress concentration factor of the test area matches the critical area of ​​the blade, while the thickness difference between the thinning region and the clamping region ensures that fracture occurs at a predetermined location.

[0012] In one implementation, the minimum thickness of the thinning region is determined based on the local minimum thickness of the critical region; the radius of the arc of the thinning region is determined based on the radius of the arc of the cross-sectional profile of the critical region; the width of the thinning region is determined according to the chord-length dimension of the critical region or the simulated damage range; and the thinning region smoothly transitions to other regions. The specific determination method for each geometric parameter of the thinning region is clarified. By mapping the local minimum thickness, arc radius, and chord-length dimension of the critical region to the corresponding parameters of the thinning region, the precise geometric correspondence between the specimen and the blade is ensured, and the smooth transition design eliminates additional stress concentration sources in non-test areas.

[0013] As one implementation method, constructing the plate-shaped fatigue specimen model includes: constructing the plate-shaped fatigue specimen model using parametric modeling; performing finite element analysis on the plate-shaped fatigue specimen model to calculate the stress concentration factor of the specimen's test area; comparing the stress concentration factor of the test area with the stress concentration factor of the target area to obtain the relative error; and correcting the plate-shaped fatigue specimen model based on the relative error to obtain the final plate-shaped fatigue specimen model. Parametric modeling enables rapid construction and adjustment of the specimen, and finite element analysis quantitatively calculates the relative error of the stress concentration factor, providing accurate numerical basis for the equivalence verification of the specimen.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0015] By using vibration simulation analysis under service conditions, the fatigue crack initiation location of the blade is accurately located. Key geometric parameters such as the local thickness and radius of the arc of the critical area are extracted and mapped onto the specimen. This ensures that the stress concentration factor of the specimen test area is highly consistent with the critical area of ​​the blade, thus fundamentally guaranteeing that the crack initiation location and propagation mechanism of the laboratory specimen are completely consistent with the failure mechanism of the real blade.

[0016] The theoretical stress concentration coefficients of the blade critical area and the test area of ​​the specimen were calculated by finite element analysis, and the consistency between the two was quantitatively verified by using relative error as a criterion, thus eliminating the subjectivity and blindness of the specimen design.

[0017] A geometric equivalent stress criterion is introduced as the theoretical basis for the geometric definition of the thinning region of the specimen, ensuring that the stress concentration factor of the specimen test area matches the critical area of ​​the blade. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0019] Figure 1 This is a flowchart illustrating the fatigue specimen design method in an embodiment of the present invention.

[0020] Figure 2 This is a stress cloud diagram for blade harmonic response analysis in an embodiment of the present invention;

[0021] Figure 4 This is a stress cloud diagram of the sample clamping analysis in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the plate-shaped vibration fatigue specimen structure in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0025] Example 1:

[0026] like Figure 1 As shown, this embodiment provides a test specimen design method for evaluating the vibration fatigue performance of blades. This method aims to address the problem of existing specimen designs being disconnected from the failure mechanisms of real components. By constructing a core logical framework for parameter mapping, it ensures that laboratory specimens can accurately reproduce the stress concentration state in key areas of the component. The method includes the following steps:

[0027] Step S100: Determine the target area of ​​the component.

[0028] In this embodiment, the target region refers to the critical area on the component that requires fatigue performance evaluation. This region is typically the location where the component experiences the most severe alternating loads under service conditions and is most prone to fatigue crack initiation. The determination of the target region can be achieved in various ways, such as through service condition simulation analysis of the component, etc. Figure 2As shown, the region with the highest stress concentration coefficient is identified as the target region based on the stress cloud map; alternatively, based on historical failure data or engineering experience, specific geometric feature regions on the component (such as the minimum cross-section or transition fillet) can be directly designated as the target region; furthermore, initial defect regions on the component can be discovered through non-destructive testing and used as the target region. This embodiment does not impose a unique limitation on the specific method of determining the target region, as long as the local area to be assessed can be located.

[0029] Step S200: Obtain the thickness parameters and transition fillet parameters of the target area.

[0030] After identifying the target region, it is necessary to extract key parameters that characterize the local geometry of that region. In this embodiment, thickness and transition fillet parameters are two sensitive geometric variables that determine the local stress concentration factor. The thickness parameter reflects the local load-bearing cross-sectional dimensions of the component, directly affecting the average stress level in that region; the transition fillet parameter reflects the smoothness at the abrupt change in geometry, directly affecting the direction of stress flow and the degree of stress concentration. Compared to the average or nominal thickness of the component, the local thickness and transition fillet of the target region more accurately describe the causes of stress concentration.

[0031] Step S300: Set the thickness parameter and transition fillet parameter to the thickness of the sample test area and the radius of the transition fillet, respectively.

[0032] The test area is the test section on a fatigue specimen used to simulate component failure behavior. By setting the thickness of the test area to be consistent with or proportional to the thickness parameter of the target area of ​​the component, and setting the transition fillet radius of the test area to be consistent with or proportional to the transition fillet parameter of the target area, the geometric topology of the test area is made highly similar to that of the target area. This correspondence is not a simple shape imitation, but an equivalent design based on the stress concentration mechanism. Since the stress concentration factor is mainly controlled by the local thickness and the transition fillet radius, when these two parameters are accurately mapped, the theoretical stress concentration factor of the test area will tend to be consistent with the theoretical stress concentration factor of the target area. That is, under the same loading mode, the test area will generate the same stress gradient distribution as the target area, thereby forcing fatigue cracks to initiate and propagate at the predetermined location of the specimen using the same mechanism.

[0033] Example 2:

[0034] Based on Example 1, this embodiment provides detailed specifications for the specific methods and parameter types for obtaining the geometric parameters of the target region.

[0035] In step S200, the thickness parameter specifically refers to the local minimum thickness of the target area. The transition fillet parameter specifically refers to the transition radius of the target area. At geometric discontinuities in the component, the stress concentration factor is mainly controlled by the local geometry. The local minimum thickness directly determines the nominal stress level of the critical section, representing the weakest link in the load-bearing capacity; while the transition radius directly controls the smoothness of the stress flow. The smaller the radius, the higher the stress concentration, and the easier it is for cracks to initiate at this location. In contrast, the average thickness or nominal thickness of the component cannot reflect the details of stress concentration in local areas. If used for specimen design, it will lead to a deviation between the specimen and the component's failure mechanism. Therefore, extracting these two geometric variables that are most sensitive to the local stress concentration factor ensures that the specimen accurately reproduces the component's failure behavior.

[0036] Furthermore, the specific process of obtaining the thickness parameters and transition fillet parameters of the target area includes: measuring the cross-sectional profile of the target area to obtain the local minimum thickness and transition arc radius.

[0037] Example 3:

[0038] This embodiment provides a technical solution parallel to Embodiment 2, the main difference being the different means of obtaining parameters.

[0039] In step S200, the thickness parameters and transition fillet parameters of the target area are obtained, including obtaining the local minimum thickness and transition arc radius by performing digital simulation analysis on the component.

[0040] In this embodiment, digital simulation analysis refers to the process of geometric feature extraction and analysis based on a three-dimensional digital model of the component. It is necessary to create or import a three-dimensional geometric model of the component, which should accurately reflect the component's design dimensions and geometric topological relationships. Obtaining key geometric parameters through digital simulation analysis breaks the limitation of physical object dependence, enabling the pre-design and performance evaluation of fatigue test specimens during the product design stage.

[0041] Example 4:

[0042] Based on Example 1, this embodiment provides a detailed definition of the specific implementation method for determining the target area of ​​the component in step S100, specifically including:

[0043] The target area of ​​the component is determined by performing service condition simulation analysis, identifying the stress concentration area as the target area. Service condition simulation analysis refers to using finite element analysis to simulate the stress state of the component under real working conditions. Therefore, a high-precision three-dimensional geometric model of the component is first established and assigned corresponding material properties. Then, according to the actual working conditions of the component, appropriate boundary conditions and load conditions are applied.

[0044] As a specific implementation method, for rotating components (such as turbine blades and compressor disks), service condition simulation analysis can include centrifugal load analysis, aerodynamic load analysis, and vibration modal analysis. For example, when analyzing high-pressure turbine blades, their operating speed (e.g., 12000 rpm) needs to be set to simulate centrifugal tensile stress, while airflow excitation force is applied to simulate vibration stress. By solving the mechanical equilibrium equations, the stress distribution cloud map inside the component is calculated.

[0045] After obtaining the stress distribution cloud map, the regions with the highest stress values ​​or the steepest stress gradients are identified. According to fatigue failure theory, fatigue cracks in components often initiate at the locations of the most severe local stress concentrations. Therefore, in this embodiment, the region with the highest stress concentration factor or the peak equivalent stress in the simulation results is directly identified as the target region. This step transforms the determination of the target region from empirical guesswork to data-driven analysis, ensuring that the specimen design has a clear focus. Through this precise positioning, the subsequently extracted geometric parameters can truly represent the characteristics of the weakest link in the component, thereby ensuring that the designed specimen can effectively assess the fatigue failure behavior most likely to occur in the component during actual service.

[0046] Example 5:

[0047] This embodiment, based on the above embodiments, provides a detailed description of the specific construction process of the sample model and the simulation method for specific damage scenarios. The method in this embodiment also includes:

[0048] A plate-shaped fatigue specimen model was constructed, with a thinned region in the specimen's testing area, smoothly transitioning from the other areas of the specimen. The construction of the plate-shaped fatigue specimen model was based on an optimized scheme using general laboratory fixtures and standard test conditions. During model construction, a thinned region was first designed in the gauge length of the specimen based on the thickness parameters (e.g., local minimum thickness) and transition fillet parameters (e.g., transition radius) obtained in the preceding steps. This thinned region is the aforementioned specimen testing area, and its minimum thickness and transition fillet radius directly adopt the mapped parameter values. By setting the thinned region, a geometric discontinuity is created on the specimen, making the local stress level in this region higher than in other areas. This ensures that during fatigue testing, cracks can stably initiate within the predetermined testing area, rather than unexpectedly fracturing at the clamping end or other stress concentration points. Specifically, the thinned region smoothly transitions from the other areas of the specimen (e.g., clamping section, etc.) to the other areas of the specimen. Figure 3A smooth transition design must be adopted between the points shown. A smooth transition refers to a continuous change in geometric curvature at the connection point, without sharp corners. This prevents the specimen from breaking in the transition area, thereby ensuring the validity of the test results. It should be understood that although this embodiment uses a plate-shaped specimen as an example, in other embodiments, depending on the actual shape of the component (such as a shaft component), a cylindrical rod-shaped or other irregularly shaped cross-section specimen model can also be constructed, as long as the geometric parameters of its test area satisfy the mapping relationship.

[0049] Example 6:

[0050] To verify the effectiveness of the fatigue specimen design method provided by this invention, this embodiment takes the vibration fatigue specimen design of a certain type of high-pressure turbine blade as an example for detailed explanation.

[0051] The steps for determining the target region of a component are as follows: The component can be a high-pressure turbine blade. A precise three-dimensional model of the high-pressure turbine blade is established, and its operating speed is set in the finite element analysis software. A simple harmonic aerodynamic excitation force under the first-order vibration mode is applied, and modal superposition harmonic response analysis is performed. Through service state simulation analysis of the blade, an equivalent stress distribution cloud map is obtained. The cloud map shows a significant alternating stress concentration zone near the blade crown in the middle of the blade. Using the software's coordinate query function, the spatial coordinates of this danger point are accurately determined as P_danger, and this location is identified as the target region.

[0052] Perform the steps to obtain the thickness and transition fillet parameters of the target area. Draw a tangent plane perpendicular to the blade surface through point P_danger and extract the cross-sectional profile data at that location. Measure the geometric characteristics of this dangerous section through digital simulation analysis of the component.

[0053] Next, the thickness and transition fillet parameters are set to the thickness and radius of the specimen's testing area, respectively. Based on the geometric equivalent stress criterion, a plate-shaped fatigue specimen model is designed, such as... Figure 4 As shown.

[0054] Finally, the effectiveness of the designed specimen was verified. High-precision finite element meshes were generated for the blade's dangerous region (including local features at the P_danger point) and the designed specimen model. Local vibration load boundary conditions equivalent to actual operating conditions were applied to the blade model near the P_danger point, and bending loads equivalent to the blade's vibration modes were applied to the specimen model at the clamping end. Calculation results were obtained within the high-precision range allowed by engineering.

[0055] The fatigue specimens designed using the method of this invention exhibit stress concentration factors in their test regions that are highly consistent with those in the critical areas of real components. This consistency demonstrates that the specimens can accurately reproduce the failure mechanism of the blade, ensuring that fatigue cracks will initiate and propagate in the thinned region of the specimen using the same mechanism as in real blades. Compared to traditional standard specimens, the specimens designed in this embodiment provide high-confidence experimental data, offering solid support for subsequent life prediction and process optimization.

[0056] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for designing test specimens for evaluating the vibration fatigue performance of blades, characterized in that, include: Vibration simulation analysis of the actual blade model under service conditions was performed to determine the initiation location of fatigue cracks, i.e., the dangerous area. The cross-sectional profile of the hazardous area is measured to obtain key geometric parameters, including at least the local thickness and the radius of the arc. Based on the key geometric parameters obtained, a single-sided notched plate fatigue specimen model for laboratory use was constructed.

2. The method for designing test specimens for evaluating the vibration fatigue performance of blades according to claim 1, characterized in that, The vibration simulation analysis of the target real blade model under service conditions specifically includes: Establish the initial three-dimensional model of the component; Set the operating speed of the initial three-dimensional model of the component, apply a simple harmonic aerodynamic excitation force under the first vibration mode, and perform harmonic response analysis using the modal superposition method; Based on the analysis, the equivalent stress distribution cloud map of the initial three-dimensional model was obtained, and the alternating stress concentration area was identified as the dangerous area for vibration fatigue. The spatial coordinates of the fatigue crack initiation location in this dangerous area were obtained through the coordinate query function.

3. The method for designing test specimens for evaluating the vibration fatigue performance of blades according to claim 2, characterized in that, The service condition simulation analysis includes a combination of modal stress, centrifugal force and airflow excitation force analysis to simulate the actual service environment of the blade.

4. The method for designing test specimens for evaluating the vibration fatigue performance of blades according to claim 1, characterized in that, It also includes verifying the consistency between the stress concentration factor of the test region of the plate fatigue specimen model and the stress concentration factor of the target region: Obtain the blade critical area of ​​the blade model and the clamping area of ​​the plate fatigue specimen model, and perform mesh generation; Based on the divided mesh, loads are applied to the blade critical area of ​​the blade model and the clamping area of ​​the plate fatigue specimen model, respectively. After applying the load, the theoretical stress concentration factor of the critical area of ​​the blade and the theoretical stress concentration factor of the transition fillet of the specimen are obtained. Compare the theoretical stress concentration factor of the critical area of ​​the blade with the theoretical stress concentration factor at the transition fillet of the specimen. If the relative error between the two is less than a preset threshold, it is determined that the stress concentration state of the specimen model is consistent with that of the actual critical area of ​​the blade.

5. The method for designing test specimens for evaluating the vibration fatigue performance of blades according to claim 4, characterized in that, The application of loads to the critical area of ​​the blade model and the clamping area of ​​the plate fatigue specimen model specifically includes: For the critical area of ​​the blade model after meshing, apply local vibration load boundary conditions equivalent to the actual working conditions within the critical point threshold range; A bending load equivalent to the blade vibration mode is applied to the clamping region of the plate fatigue specimen model after meshing.

6. The method for designing test specimens for evaluating the vibration fatigue performance of blades according to claim 5, characterized in that, When verifying the consistency between the stress concentration factor of the test area of ​​the plate fatigue specimen model and the stress concentration factor of the target area, the method further includes: A thinning region is provided in the gauge length of the plate fatigue specimen model. The minimum thickness of the thinning region is less than the thickness of the clamping region to ensure that the fracture occurs in the thinning region. The geometric definition of the thinned region follows the geometric equivalent stress criterion; Based on the geometric equivalent stress criterion, the consistency between the stress concentration factor of the test area of ​​the sample and the stress concentration factor of the target area is verified.

7. The method for designing test specimens for evaluating the vibration fatigue performance of blades according to claim 4, characterized in that, The minimum thickness of the thinning region is determined based on the local minimum thickness of the danger zone; The radius of the arc in the thinned region is determined based on the radius of the arc in the cross-sectional profile of the hazardous region; The width of the thinned region is determined based on the chord-length dimension of the hazardous region or the simulated damage range; The thinned area transitions smoothly to other areas.

8. The method for designing test specimens for evaluating the vibration fatigue performance of blades according to claim 1, characterized in that, The construction of the plate-shaped fatigue specimen model includes: The plate-shaped fatigue specimen model was constructed using parametric modeling. Finite element analysis was performed on the plate-shaped fatigue specimen model to calculate the stress concentration factor in the test area of ​​the specimen. The stress concentration factor of the test area of ​​the sample is compared with the stress concentration factor of the target area to obtain the relative error; Based on the relative error correction plate fatigue specimen model, the final plate fatigue specimen model is obtained.

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