Simulation piece design method based on stress gradient fitting and blade root characteristic simulation piece

Abstract

The invention discloses a simulation part design method based on stress gradient fitting and a blade root characteristic simulation part. The simulation part design method comprises the following steps that S1, a dangerous area of a blade root part is determined based on simulation analysis of a turbine blade under a real working condition, and characteristic parameters are extracted; s2, designing a simulation piece examination section configuration based on a low-cycle fatigue simulation piece design criterion and the extracted characteristic parameters; s3, extracting the maximum stress gradient of the maximum first principal stress point of the blade root part of the turbine blade in a preset range in a preset direction, and carrying out normalization processing to obtain a stress gradient range of the blade root part of the real blade; s4, extracting the stress gradient of the simulation piece examination section, performing same normalization processing, comparing stress gradient fitting conditions, and performing fitting on the stress gradient by modifying and adjusting non-characteristic parameters of the simulation piece examination section and simulation piece configuration to control a stress gradient error; s5, a clamping section and a transition section are designed, and the strength of the clamping section and the strength of the transition section meet the requirement; and S6, the overall configuration design of the blade root feature simulation part is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of aero-engine test, and in particular, to a design method for a root feature simulation component based on stress gradient fitting. In addition, the present invention also relates to a root feature simulation component including the above-mentioned design method for a root feature simulation component based on stress gradient fitting. Background Art

[0002] The root part of a gas turbine rotor blade has complex geometric, load and material characteristics, which are specifically reflected in: 1) Geometrically, there are geometric abrupt structures such as chamfers and bosses at the connection of the blade root, which are likely to cause stress concentration and significant stress / strain gradients; the turbulator belongs to a cylindrical protrusion and also has obvious stress concentration; 2) In terms of load, the blade rotates at a high speed, and as the working state of the engine changes, the rotational speed undergoes a large cycle, so the root part of the blade has a complex working environment; 3) In terms of material, most gas turbine rotor blades are made of anisotropic single-crystal superalloys. Under the coupling effect of material anisotropy and blade geometric structure, the root part of the blade also shows significant mechanical property differences, and under the action of the same mechanical and temperature loads, it also shows completely different stress and strain distributions; In addition, under the coupling effect of material anisotropy and blade geometric structure, significant mechanical property differences also appear in different parts of the blade, and under the action of the same mechanical and temperature loads, completely different stress and strain distributions also appear. Under the combined influence of complex geometric, load and material characteristics, gas turbine blades are extremely prone to failure, so they are managed as "critical components". Different parts of a gas turbine rotor blade may have different types of failures, and multiple damages may accumulate in the same part in a coupled manner.

[0003] In summary, it is necessary to design a characteristic simulation component that can consider the life of the root part of a turbine blade with multiple failure modes. At present, the design of the simulation component can only simulate its characteristics and is realized by means of a load test based on this simulation component. The existing simulation components usually mainly consider the simulation of the geometric characteristics of the turbine blade, and there are problems such as complex design, high processing cost and great test difficulty; moreover, the emphasis on the geometric feature design makes the stress concentration phenomenon not obvious in the existing most simulation components during the test, resulting in damage to non-target areas and affecting the accuracy of the test results. Summary of the Invention

[0004] The present invention provides a design method for a simulation component and a root feature simulation component based on stress gradient fitting to solve the technical problem that the existing design method emphasizes the design of geometric features, resulting in the stress concentration phenomenon not being obvious in the existing most simulation components during the test, causing damage to non-target areas and affecting the accuracy of the test results.

[0005] According to one aspect of the present invention, a design method for a root feature simulation component based on stress gradient fitting is provided, including the following: S1. Determine the dangerous area at the root of the turbine blade based on the simulation analysis of the turbine blade under actual working conditions and extract the characteristic parameters; S2. Design the configuration of the assessment section of the simulation component based on the low-cycle fatigue simulation component design criteria and the extracted characteristic parameters; S3. Extract the maximum stress gradient within a preset direction and a preset range at the maximum first principal stress point at the root of the turbine blade, and perform normalization processing to obtain the stress gradient range at the root of the actual blade; S4. Extract the stress gradient of the assessment section of the simulation component and perform the same normalization processing. Compare the stress gradient fitting situation, and control the stress gradient error by modifying and adjusting the non-characteristic parameters of the assessment section of the simulation component and the stress gradient of the simulation component configuration; S5. Design the clamping section and the transition section to meet the strength requirements; S6. Complete the overall configuration design of the root feature simulation component.

[0006] As a further improvement of the above technical solution, step S1 includes: S11. Obtain the material parameters of the turbine blade, import the three-dimensional model, and use ANSYS Workbench to perform simulation analysis on the turbine blade according to the service temperature, working speed, and load spectrum of the blade under actual working conditions. Analyze the stress distribution at the root of the turbine blade, and determine the dangerous part of the turbine blade according to the stress calculation results; S12. Determine the test load of the characteristic simulation component; S13. Extract the geometric parameters of the dangerous part, and the extracted geometric parameters are used as the invariants for the design of the characteristic simulation component; S14. Perform sub-model segmentation on the turbine blade and ensure that the model can be swept. Import the boundary conditions obtained in step S11 to obtain a more accurate stress distribution of the dangerous part.

[0007] As a further improvement of the above technical solution, step S12 includes: S121. Calculate the total creep damage for a preset time; S122. Based on the linear damage principle, calculate the equivalent hours of the total creep damage for a preset time reduced to the assessment working condition; S123. According to the load ratio of the main cycles corresponding to the preset time, evenly distribute the equivalent hours to the corresponding number of main cycles; S124. Use the formula , Evaluate creep damage, where T is the nominal temperature, θ is the actual temperature of the structural component (°C), x is the nominal stress, σ is the first principal stress, and t is the life of the structural component.

[0008] As a further improvement of the above technical solution, step S14 includes: S141. Determine the position of the maximum first principal stress at the dangerous part, and derive the first principal stress data table within the preset range of the maximum first principal stress position. The table includes the magnitude of the first principal stress, the direction of the first principal stress, and the node coordinates corresponding to the first principal stress. S142. Import the extracted first principal stress data table into MATLAB, process the data using MATLAB, and extract the steepest stress gradient in the vertical direction of the maximum principal stress point at the dangerous part of the blade root.

[0009] As a further improvement of the above technical solution, step S142 includes: Select an appropriate Δr as the radius step according to the blade root size, draw a preset number of arcs with the maximum first principal stress point as the center, find the minimum first principal stress point corresponding to each arc within the arc range, and draw a connection line based on the points (O, 1, 2…n - 1, n) to obtain the maximum first principal stress gradient path; based on the extracted maximum first principal stress gradient path, establish a preset path, and extract the first principal stress value table on the preset path based on the calculation result of step S13. The first principal stress value table includes the magnitude of the first principal stress and the distance from the maximum first principal stress point.

[0010] As a further improvement of the above technical solution, step S2 includes: Based on step S14, extract the maximum stress gradient in the vertical direction of the first principal stress within 1 mm of the maximum principal stress part of the test section of the feature simulation component, obtain a 1 - mm path, and extract the first principal stress value table on the path. The first principal stress value table includes the magnitude of the first principal stress and the distance from the maximum first principal stress point.

[0011] As a further improvement of the above technical solution, step S3 further includes: Based on the stress gradient tables obtained in step S142 and step S2, normalize the first principal stress with the magnitude of the maximum first principal stress as 1, draw a scatter plot, and analyze the stress gradient fitting situation of the test section of the feature simulation component.

[0012] As a further improvement of the above technical solution, step S4 further includes: Compare the stress gradients of the real blade root part and the test section of the simulation component, and iteratively design the configuration of the test section of the feature simulation component to control the stress gradient error within 5%.

[0013] As a further improvement of the above technical solution, the characteristic dimensions include the fillet size, the flange thickness, the turbine blade length ratio, and the curvature radius, and the non-characteristic dimensions include the boss size, the thickness of the simulation part, the width of the simulation part, and the chamfer of the non-evaluated surface of the boss.

[0014] According to another aspect of the present invention, there is also provided a root feature simulation part, which includes the above-mentioned root feature simulation part design method based on stress gradient fitting.

[0015] The present invention has the following beneficial effects: This design method selects a root feature simulation part of a gas turbine to explore the influence laws of geometric mutation structure features, multi-field loads, gas environment, etc. of the turbine blade on the damage evolution of the blade root part. When designing, first determine the dangerous area of the blade root part based on the simulation analysis of the turbine blade under actual working conditions and extract characteristic parameters. According to the geometric similarity principle and the stress / strain distribution similarity principle of the low-cycle fatigue simulation part design, through the extraction of the characteristic dimensions of the dangerous part of the turbine blade root and the fitting of the stress gradient, accurately characterize the stress concentration situation of the dangerous part of the turbine blade root. At the same time, through multiple iterative designs, control the stress gradient error between the evaluation section of the characteristic simulation part and the stress gradient of the actual dangerous part of the blade root. Comprehensively consider the influence of the complex geometric configuration, stress distribution, and stress gradient of the blade root part on the life. While achieving the same characteristic dimensions, simplify the configuration of the simulation part, weaken the non-essential dimensions of the simulated blade root feature part, reduce costs and increase efficiency, and improve the life prediction accuracy of the turbine blade root part while reducing the test difficulty.

[0016] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The present invention will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is the design flow chart of the preferred embodiment of the present invention; Figure 2 is a schematic diagram of the ANSYS Workbench finite element analysis calculation results of the dangerous part of the gas turbine blade root in the preferred embodiment of the present invention; Figure 3 is a schematic diagram of the low-cycle fatigue test load spectrum of the root simulation part in the preferred embodiment of the present invention; Figure 4 is a schematic diagram of the creep test load spectrum of the root simulation part in the preferred embodiment of the present invention; Figure 5Schematic diagram of creep-fatigue compliance test load spectrum of blade root simulation component in the preferred embodiment of the present invention; Figure 6 Schematic diagram of extraction of characteristic parameters of turbine blade in the preferred embodiment of the present invention; Figure 7 Schematic diagram of ANSYS Workbench finite element analysis result of assessment section of blade root characteristic simulation component in the preferred embodiment of the present invention; Figure 8 Schematic diagram of blade root characteristic simulation component in the preferred embodiment of the present invention Figure One ; Figure 9 Schematic diagram of blade root characteristic simulation component in the preferred embodiment of the present invention Figure Two ; Figure 10 Schematic diagram of blade root characteristic simulation component in the preferred embodiment of the present invention Figure Three ; Figure 11 Schematic diagram of comparison result of stress gradient between dangerous part of blade root of real blade and assessment section of simulation component in the preferred embodiment of the present invention. Specific embodiments

[0018] The following will describe the embodiments of the present invention in detail with reference to the accompanying drawings, but the present invention can be implemented in many different ways defined and covered by the following.

[0019] Figure 1 Design flow chart of the preferred embodiment of the present invention; Figure 2 Schematic diagram of ANSYS Workbench finite element analysis calculation result of dangerous part of blade root of gas turbine blade in the preferred embodiment of the present invention; Figure 3 Schematic diagram of low cycle fatigue test load spectrum of blade root simulation component in the preferred embodiment of the present invention; Figure 4 Schematic diagram of creep test load spectrum of blade root simulation component in the preferred embodiment of the present invention; Figure 5 Schematic diagram of creep-fatigue compliance test load spectrum of blade root simulation component in the preferred embodiment of the present invention; Figure 6 Schematic diagram of extraction of characteristic parameters of turbine blade in the preferred embodiment of the present invention; Figure 7 Schematic diagram of ANSYS Workbench finite element analysis result of assessment section of blade root characteristic simulation component in the preferred embodiment of the present invention; Figure 8 Schematic diagram of blade root characteristic simulation component in the preferred embodiment of the present invention Figure One ; Figure 9 Schematic diagram of blade root characteristic simulation component in the preferred embodiment of the present invention Figure Two ; Figure 10 Schematic diagram of blade root characteristic simulation component in the preferred embodiment of the present invention Figure Three ; Figure 11It is a schematic diagram of the stress gradient comparison results between the dangerous part of the real blade root and the test section of the simulation part in the preferred embodiment of the present invention.

[0020] like Figures 1 to 11 As shown, the blade root characteristic simulation component design method based on stress gradient fitting in this embodiment includes the following contents: S1. Determine the dangerous area at the blade root and extract characteristic parameters based on the simulation analysis of turbine blades under real working conditions; S2. Design the simulation component test section configuration based on the low cycle fatigue simulation component design criteria and extracted characteristic parameters; S3. extracting the maximum stress gradient within a preset range of a preset direction of the maximum first principal stress point at the root of the turbine blade and performing normalization processing to obtain the stress gradient range of the root of the real blade; S4. extract the stress gradient of the simulation test section and perform the same normalization process, compare the stress gradient fitting, and control the stress gradient error by fitting the stress gradient by modifying and adjusting the non-characteristic parameters of the simulation test section and the simulation configuration; S5. Design the clamping section and transition section so that the strength of the clamping section and transition section meet the requirements; S6. Complete the overall configuration design of the blade root feature simulation part.

[0021] It is understandable that the root section of the blade is subjected to the centrifugal load generated by the high-speed rotation of the blade body, and there is a geometric mutation when transitioning with the edge plate. Therefore, although the temperature near the blade root is lower than that of the blade body, the stress level is higher. This design method selects the design feature simulation parts of the gas turbine blade root to explore the influence of the geometric mutation structural characteristics of the turbine blade, multi-field loads, and gas environment on the damage evolution of the blade root. When designing, first determine the dangerous area of ​​the blade root based on the simulation analysis of the turbine blade under real working conditions and extract the characteristic parameters. According to the geometric similarity principle of the low-cycle fatigue simulation part design and the stress / strain distribution similarity, the stress / strain distribution similarity is used. Based on the principle of similarity, the stress concentration in the dangerous part of the turbine blade root is accurately characterized by extracting the characteristic dimensions of the dangerous part of the turbine blade root and fitting the stress gradient. At the same time, through multiple iterative designs, the stress gradient error between the stress gradient of the test section of the characteristic simulation part and the stress gradient of the real dangerous part of the blade root is controlled. The influence of the complex geometric configuration, stress distribution and stress gradient of the blade root on the life is comprehensively considered. While achieving consistent characteristic dimensions, the configuration of the simulation part is simplified, the unnecessary dimensions of the characteristic part of the simulated blade root are deemphasized, the cost is reduced and the efficiency is increased. While reducing the difficulty of the test, the accuracy of the life prediction of the root part of the turbine blade is improved.

[0022] In some embodiments, step S1 includes: S11. Obtain the material parameters of the turbine blade, import the 3D model, and use ANSYS Workbench to perform simulation analysis on the turbine blade according to the service temperature, operating speed, and load spectrum under the actual working conditions of the blade. Analyze the stress distribution at the blade root part of the turbine blade, and determine the dangerous part of the turbine blade according to the stress calculation results. Specifically, obtain the basic parameters, density, elastic constants, Poisson's ratio, etc. of the alloy material of the current model of gas turbine blade, import the constitutive model of the component material into ANSYS Workbench, insert the material parameters after importing the 3D model of the blade, and use ANSYS Workbench to perform simulation analysis on the turbine blade according to the service temperature, operating speed, and load spectrum under the actual working conditions of the blade. Analyze the stress distribution at the blade root part of the turbine blade, and determine the dangerous part at the blade root part of the turbine blade according to the stress calculation results. S12. Determine the test load of the characteristic simulation part; among them, the low-cycle fatigue is a typical triangular wave, the nominal stress is a cyclic triangular wave from the minimum to the maximum and finally to the minimum, and the stress value and temperature value are selected as the numerical values at the most dangerous point under the most dangerous working conditions. Under the creep state, the applied temperature and stress are kept unchanged at the maximum state, and the test load is consistent with the maximum state of the low-cycle fatigue load. S13. Extract the geometric parameters of the dangerous part, and the extracted geometric parameters are used as the invariants for the design of the characteristic simulation part. For example, in a specific embodiment, select to measure the thickness of the flange at the blade root part as 1.2 mm, the blade above the flange as 22 mm, the tenon below the flange as 11 mm, and the fillet radius at the blade root as R2 mm. Based on the geometric similarity principle of the low-cycle fatigue characteristic simulation part design, initially determine that the configuration of the assessment section of the blade root characteristic simulation part based on stress gradient fitting of the present invention is a flat plate part or a round bar part with a boss, and the characteristic size of the assessment section is consistent with the geometric parameters of the extracted blade root part. S14. Perform sub-model segmentation on the turbine blade and ensure that the model can be swept, and import the boundary conditions obtained in step S11 to obtain a more accurate stress distribution of the dangerous part. Specifically, step S12 includes: S121. Calculate the total creep damage for a preset time; take 2000 h as an example for the preset time. S122. Based on the linear damage principle, calculate the equivalent hours of the total creep damage for the preset time converted to the assessment working conditions. S123. According to the load ratio of the main cycles corresponding to the preset time, evenly distribute the equivalent hours to the corresponding number of main cycles. S124. Use the formula 、 Evaluate creep damage. In the formula, T is the nominal temperature, θ is the actual temperature of the structural component (°C), x is the nominal stress, σ is the first principal stress, and t is the life of the structural component; the creep-fatigue composite is a typical trapezoidal wave, and the nominal stress or strain changes from the minimum to the maximum, passes through the hold time, and then returns to the minimum. The test load is consistent with the maximum state of the low-cycle fatigue load; according to the endurance stress-life equation, the highest stress point on the blade root fillet blade basin side is determined as the assessment part, and the stress state at this part is dominated by the first principal stress. The process of the characteristic structure from service to failure is manifested as the accumulation of damage under different failure modes. When designing the characteristic simulation component, the damage accumulation process of the actual characteristic structure is fully reflected. For creep, its microscopic damage mechanism and accumulation rate are controlled by temperature and stress levels, so the temperature and stress levels at the assessment part of the simulation component and the real structure are ensured to be consistent. After analysis, the failure modes considered in the design of this characteristic simulation component are creep, low-cycle fatigue, and creep-low-cycle fatigue composite.

[0023] Specifically, step S14 includes: S141. Determine the position of the maximum first principal stress at the dangerous part, and export the first principal stress data table within the preset range of the maximum first principal stress position. The preset range is a spherical area with a radius of 5 mm. The table includes the magnitude of the first principal stress, the direction of the first principal stress, and the node coordinates corresponding to the first principal stress. S142. Import the extracted first principal stress data table into MATLAB, process the data using MATLAB, and extract the minimum stress gradient in the vertical direction of the maximum principal stress point at the dangerous part of the blade root. Specifically, step S142 includes: Select an appropriate Δr as the radius step according to the blade root size, draw a preset number of arcs with the maximum first principal stress point as the center, find the minimum first principal stress point corresponding to each arc within the arc range, draw a connection line based on the points of (O, 1, 2…n - 1, n) to obtain the maximum first principal stress gradient path; based on the extracted maximum first principal stress gradient path, establish a preset path, and extract the first principal stress value table on the preset path based on the calculation result of step S13. The first principal stress value table includes the magnitude of the first principal stress and the distance from the maximum first principal stress point. By performing submodel segmentation on the turbine blade, a more accurate stress distribution at the dangerous part is obtained.

[0024] In some embodiments, step S2 includes: Based on step S14, extract the maximum stress gradient in the vertical direction of the first principal stress within 1 mm of the maximum principal stress part of the assessment section of the characteristic simulation component, obtain a 1-mm path, and extract the first principal stress value table on the path. The first principal stress value table includes the magnitude of the first principal stress and the distance from the maximum first principal stress point.

[0025] In some embodiments, step S3 further includes: respectively normalizing the first principal stress with the maximum magnitude of the first principal stress as 1 based on the stress gradient tables obtained in step S142 and step S2, plotting a scatter diagram, and analyzing the stress gradient fitting condition of the assessment section of the characteristic simulation part.

[0026] In some embodiments, step S4 further includes: comparing the stress gradients of the root part of the real blade and the assessment section of the simulation part, iteratively designing the configuration of the assessment section of the characteristic simulation part, controlling the stress gradient error within 5%, and ensuring approximate stress distribution; In some embodiments, step S3 further includes: In some embodiments, the characteristic dimensions include the fillet size, the flange thickness, the length ratio of the turbine blade, and the radius of curvature, and the non-characteristic dimensions include the boss size, the thickness of the simulation part, the width of the simulation part, and the chamfer of the non-assessment surface of the boss. While ensuring the consistency of the characteristic dimensions, the configuration of the simulation part is simplified, the non-essential dimensions of the characteristic part of the simulated blade root are de-emphasized, and iterative design can be carried out by adjusting the non-characteristic parameters of the assessment section of the simulation part, reducing the test difficulty and improving the accuracy of the life prediction of the root part of the turbine blade.

[0027] On the other hand, the preferred embodiment of the present invention also provides a root characteristic simulation part to which the above-mentioned design method of the root characteristic simulation part based on stress gradient fitting is applied.

[0028] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0029] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0030] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A design method for a blade root feature simulation part based on stress gradient fitting, characterized in that, It includes the following contents: S1. Determine the dangerous area at the blade root part based on the simulation analysis of the turbine blade under real working conditions and extract characteristic parameters; S2. Design the configuration of the test section of the simulation part based on the low-cycle fatigue simulation part design criterion and the extracted characteristic parameters; S3. Extract the maximum stress gradient within the preset direction and preset range of the maximum first principal stress point at the blade root part of the turbine blade to obtain the stress gradient range at the blade root part of the real blade; S4. Extract the stress gradient of the test section of the simulation part, compare the stress gradient fitting situation, and control the stress gradient error by modifying and adjusting the non-characteristic parameters of the test section of the simulation part and the stress gradient of the simulation part configuration; S5. Design the clamping section and the transition section to make the strength of the clamping section and the transition section meet the requirements; S6. Complete the overall configuration design of the blade root characteristic simulation part.

2. The design method of the blade root feature simulation part based on stress gradient fitting according to claim 1, characterized in that, Step S1 includes: S11. Obtain the material parameters of the turbine blade, import the 3D model, and use ANSYS Workbench to perform simulation analysis on the turbine blade according to the service temperature, working speed and load spectrum under the real working conditions of the blade. Analyze the stress distribution at the blade root part of the turbine blade, and determine the dangerous part of the turbine blade according to the stress calculation results; S12. Determine the test load of the characteristic simulation part; S13. Extract the geometric parameters of the dangerous part, and the extracted geometric parameters are used as the invariants for the design of the characteristic simulation part; S14. Perform sub-model segmentation on the turbine blade and ensure that the model can be swept. Import the boundary conditions obtained in step S11 to obtain a more accurate stress distribution of the dangerous part.

3. The design method of the blade root feature simulation part based on stress gradient fitting according to claim 2, characterized in that Step S12 includes: S121. Calculate the total creep damage for the preset time; S122. Based on the linear damage principle, calculate the equivalent hours of the total creep damage for the preset time converted to the test working condition; S123. According to the load ratio of the main cycles corresponding to the preset number of times for the preset time, evenly distribute the equivalent hours to the corresponding number of main cycles; S124. Adopt the formula , to evaluate creep damage, where T is the nominal temperature, θ is the actual temperature (°C) of the structural member, x is the nominal stress, σ is the first principal stress, and t is the life of the structural member.

4. The design method of the blade root feature simulation part based on stress gradient fitting according to claim 2, characterized in that Step S14 includes: S141. Determine the position of the maximum first principal stress of the dangerous part, and export the first principal stress data table within the preset range of the maximum first principal stress position. The table includes the magnitude of the first principal stress, the direction of the first principal stress, and the node coordinates corresponding to the first principal stress; S142. Import the extracted first principal stress data table into MATLAB, use MATLAB to process the data, and extract the steepest stress gradient in the vertical direction of the maximum principal stress point at the blade root dangerous part.

5. The design method of the blade root feature simulation part based on stress gradient fitting according to claim 4, wherein Step S142 includes: Select an appropriate Δr as the radius step according to the blade root size, draw a preset number of arcs with the maximum first principal stress point as the center, find the minimum first principal stress point corresponding to each arc within the arc range, and draw a connection line according to the points (O, 1, 2…n-1, n) to obtain the maximum first principal stress gradient path; Based on the extracted maximum first principal stress gradient path, establish a preset path, and extract the first principal stress value table on the preset path based on the calculation results of step S13. The first principal stress value table includes the magnitude of the first principal stress and the distance from the maximum first principal stress point.

6. The design method of the blade root feature simulation part based on stress gradient fitting according to claim 5, characterized in that, Step S2 includes: Extract the maximum stress gradient in the direction perpendicular to the first principal stress within 1 mm of the maximum principal stress part of the feature simulation part assessment section based on step S14, obtain a 1-mm path, and extract the table of the first principal stress values on the path. The table of the first principal stress values includes the magnitude of the first principal stress and the distance from the maximum first principal stress point.

7. The design method of the blade root feature simulation part based on stress gradient fitting according to claim 6, characterized in that, Step S3 further includes: normalizing the first principal stress with the magnitude of the maximum first principal stress being 1 respectively based on the stress gradient tables obtained in step S142 and step S2, plotting a scatter diagram, and analyzing the stress gradient fitting condition of the feature simulation part assessment section.

8. The design method of the blade root feature simulation part based on stress gradient fitting according to claim 7, characterized in that Step S4 further includes: comparing the stress gradients of the real blade root part and the simulation part assessment section, iteratively designing the configuration of the feature simulation part assessment section, and controlling the stress gradient error within 5%.

9. The design method of the blade root feature simulation part based on stress gradient fitting according to claim 1, characterized in that The feature dimensions include the fillet size, the flange thickness, the turbine blade length ratio, and the radius of curvature. The non-feature dimensions include the boss size, the simulation part thickness, the simulation part width, and the chamfer of the non-assessment surface of the boss.

10. A blade root feature simulation part, characterized in that, Apply the blade root feature simulation part design method based on stress gradient fitting according to any one of claims 1-9.

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