A testing method and device for ultra-high cycle fatigue performance of wind turbine blades

Abstract

The present invention provides a method and device for testing the very high cycle fatigue performance of wind turbine blades, which relates to the technical field of performance testing. Through finite element analysis of wind turbine blades, the present invention clarifies the dangerous positions and stress conditions of the blades. On the basis of screening out M potential dangerous nodes with common characteristics, potential resonance risk nodes are further screened out, and several dangerous cross-sections corresponding to each potential resonance risk node are determined. Then, key dangerous cross-sections are screened out from the several dangerous cross-sections. By analyzing the vibration displacement data of each key dangerous cross-section under different loads, a secondary screening strategy for screening out the final dangerous cross-section is obtained. According to the final dangerous cross-section, a blade structure specimen is designed and processed, so that the blade structure specimen undergoes high-frequency forced vibration under the action of a pressing head, and a very high cycle fatigue test of the wind turbine blade structure specimen is carried out using an ultrasonic fatigue testing machine with optimized fixtures; this technology requires a small test site and a short test time.

Description

Technical Field

[0001] The present invention relates to the technical field of performance testing, and in particular to a method and device for testing the ultra-high cycle fatigue performance of a wind turbine blade. Background Art

[0002] Blades are key components of wind power equipment. Their service life is required to be 20 years, and the number of fatigue cycles they endure during their service life reaches 10. 8 When the wind turbine blades are made of glass fiber reinforced plastic (GFRP), there is little research on the ultra-high cycle fatigue of GFRP, and the fatigue failure forms are complex and diverse, resulting in a lack of effective testing methods for the ultra-high cycle fatigue of wind turbine blades. The existing wind turbine blade fatigue testing technology is to load the entire blade with a hydraulic servo motor in a very large special test site. Because the operating frequency of the hydraulic servo motor is usually 50Hz, it takes a very long time to complete the ultra-high cycle fatigue test, so it can only be carried out to the fatigue cycle of 10. 6 High-cycle fatigue performance test; the ultrasonic fatigue testing machine often used for material samples in ultra-high cycle fatigue tests can reach 20KHz, which greatly reduces the test time.

[0003] In the prior art, the publication number is CN110231162B, and the name is a fatigue test method for wind turbine blades, which includes the following steps: installing the wind turbine blade on the test platform with its trailing edge facing upward, the leading edge facing downward, and the chord length perpendicular to the ground; installing multiple vibrators at different counterweight positions on the wind turbine blade in a manner of horizontal loading in the swinging direction; adjusting the parameters of the multiple vibrators so that the multiple vibrators are loaded collaboratively, starting the multiple vibrators, keeping the vibration amplitude stable and meeting the specified target requirements; by changing the traditional vertical loading to horizontal loading, and performing multi-point collaborative loading through multiple vibrators, not only the loading efficiency of a single vibrator can be improved, but also the situation of insufficient loading force when performing fatigue testing of large wind turbine blades can be avoided, thereby meeting the fatigue testing requirements of large wind turbine blades;

[0004] Jin Jiaotong's "Analysis Method of Overall Stiffness of Large Composite Wind Turbine Blades" describes how to establish a 3D model of a megawatt-class wind turbine blade using the large-scale general 3D design software PROE, and import the established 3D model into the general finite element analysis software ANSYS for finite element analysis; the shell element shel81 is used to simulate the composite material characteristics of wind turbine blades, and modal analysis and static analysis are performed; both modal analysis and static analysis show that the analysis results of the first-order natural frequency and deflection of wind turbine blades in the swing and flapping directions are in good agreement with the measured results, which shortens the modeling time and improves work efficiency;

[0005] The shortcomings are: the fatigue test of the wind turbine blade cannot reach the ultra-high cycle fatigue range, and the ultrasonic fatigue testing machine that can perform ultra-high cycle fatigue testing is limited to the testing of small material samples, and has not been applied to the fatigue testing of large equipment or structural specimens; currently, there is a lack of ultra-high cycle fatigue testing methods for wind turbine blades;

[0006] The above information disclosed in the above Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to one of ordinary skill in the art. Summary of the invention

[0007] The object of the present invention is to provide a method and device for testing the ultra-high cycle fatigue performance of wind turbine blades, so as to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for testing ultra-high cycle fatigue performance of a wind turbine blade, comprising the following specific steps:

[0010] Step S1: according to the current actual wind load environment, determine the wind speed range and turbulence level range, and perform simulation tests under the wind speed range and turbulence level range to obtain historical wind load data within different range combinations, the historical wind load data including the actual values ​​of wind speed and air pressure, and the corresponding aerodynamic load value and the angle of attack of the wind turbine blade relative to the wind;

[0011] Step S2: construct a three-dimensional turbulent wind field model based on historical wind load data, and establish a parametric three-dimensional model of a wind turbine blade, apply the three-dimensional turbulent wind field model as an external load to the parametric three-dimensional model of the wind turbine blade, analyze the stress conditions of the wind turbine blade under different wind speeds and turbulence conditions through finite element analysis software, screen out M potential dangerous nodes with common characteristics, and perform modal analysis on the parametric three-dimensional model to screen out potential resonance risk nodes from the M potential dangerous nodes, and obtain the natural frequency and load form vibration mode of each potential resonance risk node;

[0012] Step S3: determining a number of dangerous sections corresponding to each potential resonance risk node according to the potential resonance risk nodes identified by the finite element analysis result;

[0013] Collect the fatigue damage data of each dangerous section under different wind speed and turbulence conditions, and set the upper limit threshold of fatigue damage for each dangerous section based on the finite element analysis results. Screen out the dangerous sections with a value greater than the upper limit threshold of fatigue damage to form key dangerous sections. Combine the natural frequency and load form vibration mode of each key dangerous section to perform incremental aerodynamic load simulation.

[0014] Step S4: During the simulation of the incremental aerodynamic load, the vibration displacement data of each critical dangerous section under different loads are recorded, and the collected vibration displacement data are analyzed to generate a secondary screening strategy for screening the final dangerous section from the critical dangerous sections;

[0015] Step S5: Design a blade structure specimen with the same final dangerous section as that provided by the secondary screening strategy, use the same material as the original wind turbine blade for processing, and perform a high-frequency vibration test on the blade structure specimen.

[0016] A wind turbine blade ultra-high cycle fatigue performance testing device, the device is used to perform the wind turbine blade ultra-high cycle fatigue performance testing method, comprising:

[0017] The test device includes an adjustable spacing fixture for installing a blade structure specimen, and an ultrasonic pressure head connected in sequence through a transducer, an actuator and a width rod, and the blade structure specimen includes a blade circumferential structure specimen or a blade radial structure specimen; the test device also includes an ultrasonic generator connected to the transducer, and the ultrasonic generator is connected to a control system computer;

[0018] Data acquisition module: Determine the wind speed range and turbulence level range according to the current actual wind load environment, and conduct simulation tests under the wind speed range and turbulence level range to obtain historical wind load data within different range combinations. The historical wind load data includes the actual values ​​of wind speed and air pressure, as well as the corresponding aerodynamic load value and the angle of attack of the wind turbine blade relative to the wind;

[0019] Three-dimensional turbulent wind field model construction module: construct a three-dimensional turbulent wind field model based on historical wind load data, and establish a parametric three-dimensional model of wind turbine blades. Apply the three-dimensional turbulent wind field model as an external load to the parametric three-dimensional model of wind turbine blades. Use finite element analysis software to analyze the stress conditions of wind turbine blades under different wind speeds and turbulence conditions, and select M potential dangerous nodes with common characteristics. Perform modal analysis on the parametric three-dimensional model to select potential resonance risk nodes from the M potential dangerous nodes, and obtain the natural frequency and load form vibration mode of each potential resonance risk node;

[0020] Key dangerous section determination module: used to determine several dangerous sections corresponding to each potential resonance risk node according to the potential resonance risk nodes identified by the finite element analysis results;

[0021] Collect the fatigue damage data of each dangerous section under different wind speed and turbulence conditions, and set the upper limit threshold of fatigue damage for each dangerous section based on the finite element analysis results. Screen out the dangerous sections with a value greater than the upper limit threshold of fatigue damage to form key dangerous sections. Combine the natural frequency and load form vibration mode of each key dangerous section to perform incremental aerodynamic load simulation.

[0022] Final dangerous section determination module: used to record the vibration displacement data of each critical dangerous section under different loads during the simulation of incremental aerodynamic loads, analyze the collected vibration displacement data, and generate a secondary screening strategy for screening the final dangerous section from these critical dangerous sections;

[0023] Specimen testing module: used to design blade structure specimens with the same final dangerous cross-section as provided by the secondary screening strategy, and processed using the same material as the original wind turbine blade.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: by performing parameterized three-dimensional modeling and finite element analysis on wind turbine blades, the dangerous positions and stress conditions of the blades are clarified; on the basis of screening out M potential dangerous nodes with common characteristics, potential resonance risk nodes are further screened out, and several dangerous sections corresponding to each potential resonance risk node are determined, and key dangerous sections are screened out from several dangerous sections; the vibration displacement data of each key dangerous section under different loads are analyzed to obtain a secondary screening strategy for screening out the final dangerous section; according to the final dangerous section, the blade structure specimen is designed and processed so that the blade structure specimen undergoes high-frequency forced vibration under the action of the pressure head; and an ultrasonic fatigue testing machine with optimized fixture is used to perform ultra-high cycle fatigue test on the wind turbine blade structure specimen; the technology requires a small test site and a short test time. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall method flow of the present invention;

[0026] Figure 2 This is a schematic diagram of the module flow of the device of the present invention;

[0027] Figure 3 This is the technical roadmap for the ultra-high cycle fatigue test of wind turbine blades of the present invention;

[0028] Figure 4 It is a schematic diagram of an ultra-high cycle fatigue test system of a blade circumferential structure specimen under a shimmying stress state according to the present invention;

[0029] Figure 5 It is a schematic diagram of the ultra-high cycle fatigue testing system of the blade radial structure specimen under the flapping stress state of the present invention.

[0030] Figure numerals: 1, transducer; 2, actuator; 3, edge rod; 4, ultrasonic pressure head; 5, adjustable spacing fixture; 6, ultrasonic generator; 7, control system computer; 8, blade circumferential structure specimen; 9, blade radial structure specimen. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0032] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0033] Embodiment 1:

[0034] See also Figure 1 , the present invention provides a technical solution:

[0035] A method for testing ultra-high cycle fatigue performance of a wind turbine blade, comprising the following specific steps:

[0036] Step S1: Use GH-Bladed, a wind turbine performance and load calculation software, to perform fatigue load calculations on wind turbine blades under multiple working conditions; determine the wind speed range and turbulence level range according to the current actual wind load environment, and perform simulation tests under the wind speed range and turbulence level range to obtain historical wind load data within different range combinations, the historical wind load data including actual values ​​of wind speed and air pressure, and corresponding aerodynamic load values ​​and the angle of attack of the wind turbine blade relative to the wind;

[0037] Step S2: construct a three-dimensional turbulent wind field model based on historical wind load data, and establish a parametric three-dimensional model of a wind turbine blade, apply the three-dimensional turbulent wind field model as an external load to the parametric three-dimensional model of the wind turbine blade, analyze the stress conditions of the wind turbine blade under different wind speeds and turbulence conditions through finite element analysis software, screen out M potential dangerous nodes with common characteristics, and perform modal analysis on the parametric three-dimensional model to screen out potential resonance risk nodes from the M potential dangerous nodes, and obtain the natural frequency and load form vibration mode of each potential resonance risk node;

[0038] Step S3: determining a number of dangerous sections corresponding to each potential resonance risk node according to the potential resonance risk nodes identified by the finite element analysis result;

[0039] Collect the fatigue damage data of each dangerous section under different wind speed and turbulence conditions, and set the upper limit threshold of fatigue damage for each dangerous section based on the finite element analysis results. Screen out the dangerous sections with a value greater than the upper limit threshold of fatigue damage to form key dangerous sections. Combine the natural frequency and load form vibration mode of each key dangerous section to perform incremental aerodynamic load simulation.

[0040] Step S4: During the simulation of the incremental aerodynamic load, the vibration displacement data of each critical dangerous section under different loads are recorded, and the collected vibration displacement data are analyzed to generate a secondary screening strategy for screening the final dangerous section from the critical dangerous sections;

[0041] Step S5: design a blade structure specimen with the same final dangerous section as that provided by the secondary screening strategy, and process it using the same material as the original wind turbine blade;

[0042] Step S6: mounting the blade structure specimen on an adjustable spacing fixture that can adapt to different stress conditions, and connecting it to an ultrasonic fatigue testing machine for high-frequency vibration testing;

[0043] Step S7: setting test parameters, starting the ultrasonic fatigue testing machine, monitoring the response of the blade structure specimen under high-frequency vibration, and recording test data.

[0044] Analyze test data, evaluate fatigue behavior and failure mechanism of wind turbine blade structure specimens under ultra-high cycle fatigue conditions, and generate detailed test reports.

[0045] Further explanation: the acquisition of historical wind load data includes:

[0046] 1.1) Determine wind turbine parameters and operating conditions:

[0047] Select wind turbine model: Select a representative wind turbine model based on actual application, and use a 3MW horizontal axis wind turbine;

[0048] Setting the test range: taking the maximum wind speed in the historical wind load data as the upper limit of the wind speed range, and taking the minimum wind speed as the lower limit of the wind speed range. In this embodiment, the wind speed range is determined to be from 3m / s to 25m / s, and the turbulence level classification is determined according to the international standard IEC61400, and the historical turbulence condition data of the area where the wind turbine blades are located is matched with the turbulence level to cover all operating conditions;

[0049] 1.2) Wind load calculation software settings:

[0050] Install and configure GH-Bladed. The configuration setup includes inputting the wind turbine geometry, material properties and initial conditions.

[0051] Input parameters: Determine the design parameters of the wind turbine blades on the wind turbine, which are blade length, width, thickness, curvature, mass, and stiffness, and input the design parameters into the load calculation software GH-Bladed, and set the aerodynamic model parameters of the angle of attack, lift, and drag coefficients;

[0052] 1.3) Working condition simulation and historical wind load data collection:

[0053] Perform wind load simulation: Use GH-Bladed to calculate wind loads under various set wind speeds and turbulence conditions, obtain wind load data under different working conditions, and summarize these wind load data as historical wind load data;

[0054] Record wind speed and air pressure data: During the simulation process, record the wind speed, air pressure and corresponding aerodynamic load values ​​under each simulated working condition, and also record the angle of attack of the wind turbine blades relative to the wind;

[0055] Data storage: The above collected data is stored in a structured manner to form a database for subsequent analysis.

[0056] 1.4) Analysis and collation of historical wind load data:

[0057] Analyze historical data: Sort and analyze the collected historical wind load data, and calculate the statistical characteristics of wind load under different working conditions. The statistical characteristics are mean, variance and extreme value;

[0058] Develop test standards: Based on the analysis results, develop standard operating conditions for ultra-high cycle fatigue performance testing of wind turbine blades. These standards should cover the most risky operating conditions.

[0059] 1.5) Output and report generation:

[0060] Generate reports: Integrate simulation results with analysis data to generate a system test report, including graphs of wind speed, air pressure, aerodynamic loads, and angle of attack;

[0061] Turbulence conditions include turbulence intensity, wind speed distribution, and turbulence structure parameters;

[0062] The angle of attack refers to the angle between the chord direction of the wind turbine blade and the incoming wind. The chord direction is the straight line connecting the leading edge and the trailing edge of the blade.

[0063] The aerodynamic load value refers to the aerodynamic load value borne by the wind turbine blade under different combinations of wind speed, air pressure and attack angle.

[0064] Further explanation: screening out M potential dangerous nodes with common characteristics and determining the natural frequency and load form vibration mode of each potential dangerous node specifically include:

[0065] 2.1) Parametric 3D modeling of wind turbine blades:

[0066] According to the blade design parameters obtained in step S1, select SolidWorks, CATIA or Creo to perform parametric 3D modeling on the wind turbine blade;

[0067] Define a visual user interface for each design parameter, making subsequent parameter adjustments more intuitive;

[0068] 2.2) Import finite element analysis software:

[0069] Select finite element analysis software as ANSYS, ABAQUS or COMSOL Multiphysics;

[0070] Export the established parametric 3D model of wind turbine blades to STEP or IGES format, and then import it into the selected finite element analysis software;

[0071] Use the meshing tool in the finite element software to divide the imported parameterized 3D model into N mesh regions, and set i to represent the i-th mesh region, and i∈[1,N]; ensure that there is sufficient mesh density near the potential dangerous nodes to obtain higher calculation accuracy;

[0072] 2.3) Construct a three-dimensional turbulent wind field model:

[0073] Obtain historical data of wind speed, air pressure, angle of attack and aerodynamic load values ​​from the historical wind load data derived in step S1, perform statistical analysis, and determine the turbulence characteristics of the wind field;

[0074] Use fluid dynamics software FLUENT or OpenFOAM to establish a three-dimensional turbulent wind field model consistent with historical wind load data;

[0075] Set boundary conditions and initial conditions to ensure that the simulation results can truly reproduce the turbulence characteristics of the actual wind field;

[0076] The turbulent wind field model is coupled with the finite element model of the wind turbine blade to ensure that the wind load can act on the parametric 3D model of the wind turbine blade in real time during the analysis process;

[0077] 2.4) Apply external loads and perform finite element analysis:

[0078] In the finite element analysis software, the constructed three-dimensional turbulent wind field model is applied as an external load to the parametric three-dimensional modeling of the wind turbine blades;

[0079] Select dynamic analysis to analyze the stress of wind turbine blades under different wind speeds and turbulence conditions, and obtain the stress analysis results under each simulated working condition;

[0080] And record the stress, strain and displacement results under each simulation condition;

[0081] 2.5) Identify potentially dangerous nodes:

[0082] The stress analysis results are post-processed to screen out M potential dangerous nodes with common characteristics under different wind speed and turbulence conditions, including:

[0083] According to the yield strength of the material used in the wind turbine blade, 55% of the yield strength is defined as the stress threshold ST. In this embodiment, ST = 300 MPa. The stress threshold ST can also be analyzed based on the existing fatigue test data to analyze the fatigue life of the material under different stress levels. The lowest stress value at which material failure begins to occur in the historical data is selected as ST.

[0084] In the N grid areas divided by the parameterized three-dimensional model of the wind turbine blade, the maximum principal stress exceeding ST under different wind speed and turbulence conditions is used as a screening rule, and the grid areas that meet the screening rule are screened out as potential dangerous nodes with common characteristics;

[0085] The M potential dangerous nodes are represented by a sequence set {1, 2, ..., j, ..., M}, where j represents the jth potential dangerous node index, and each potential dangerous node has a corresponding position in the N grid areas;

[0086] If the number of potential dangerous nodes M finally identified is within 5, that is, M≤5, it means that the safety of the wind turbine blade design is good. When M>5, it means that the safety of the wind turbine blade design is poor and the safety of the wind turbine blade design needs to be improved.

[0087] Use the post-processing tools in the finite element analysis software to generate stress distribution diagrams and deformation diagrams to visually display potential dangerous nodes;

[0088] 2.6) Perform modal analysis:

[0089] Select the "Modal Analysis" module in the finite element software and set the analysis scope to ensure that the natural frequencies of all potentially dangerous nodes are examined, including:

[0090] Simulate the dynamic response of wind turbine blades at different frequencies to identify potential resonant frequencies; set the natural frequency threshold to 85% of the first resonant frequency in modal analysis, and record the natural frequency threshold as NFT;

[0091] When the natural frequency of a potential dangerous node is less than NFT, it is recorded as a potential resonance risk node, and each potential resonance risk node is represented by a sequence set as ju = {j1, j2, ..., jU}, where ju represents the index of the juth potential resonance risk node, and ju∈{1, 2, ..., j, ..., M};

[0092] Run a modal analysis to obtain the natural frequencies and load mode shapes for each node at potential resonance risk, including flapping and shimmy modes.

[0093] The modal analysis results are recorded and an analysis report of the natural frequency and load form vibration mode is generated to provide a basis for subsequent fatigue performance evaluation.

[0094] Further explanation: several dangerous sections corresponding to each potential resonance risk node are determined, dangerous sections greater than the upper threshold of fatigue damage are screened out, and incremental aerodynamic load simulation is performed in combination with the natural frequency and load form vibration mode of each potential resonance risk node, specifically including:

[0095] For the juth potential resonance risk node, determine the corresponding several dangerous sections to form a dangerous section sequence set {S ju,1 ,S ju,2 ,…,S ju,k ,…,S ju,K}, where S ju,k represents the index of the kth dangerous section in the juth potential resonance risk node, and K represents the total number of dangerous sections in the corresponding potential resonance risk node;

[0096] The dangerous section is determined as follows:

[0097] 3.1) Locate potential resonance risk nodes:

[0098] According to the parameterized three-dimensional model, determine the central three-dimensional coordinates of the j-th potential resonance risk node;

[0099] 3.2) Define the cross-section extraction area:

[0100] Select the cross-section extraction area, take the central three-dimensional coordinates of the potential resonance risk node as the origin, and take the origin as the center and the cylindrical area with a radius of r1 as the dangerous cross-section extraction area; in this embodiment, the radius r1 is 50 mm;

[0101] 3.3) Extract stress data:

[0102] Calculate the stress distribution in the dangerous section extraction area; in finite element analysis, extract the stress data of all cells or nodes in the grid;

[0103] 3.4) Select the dangerous section:

[0104] Based on the stress distribution, the following critical sections are identified:

[0105] Principal stress section: Select the section parallel to the maximum principal stress, located at the center of the maximum stress and stress concentration area;

[0106] Shear stress section: Select the corresponding shear stress section in the direction of the principal stress; this helps to evaluate shear fatigue;

[0107] Cross-section: Select a section perpendicular to the principal stress direction to fully evaluate the stress state;

[0108] 3.5) Calculate the stress value on the cross section:

[0109] For each selected section, calculate the corresponding stress value and record it;

[0110] Fatigue damage data include the number of load cycles, stress amplitude and fatigue limit of wind turbine blade materials under different wind speed and turbulence conditions;

[0111] The stress amplitude is the stress variation amplitude of the wind turbine blade material under cyclic load;

[0112] The number of load cycles represents the number of load cycles that the wind turbine blade material can withstand under a given stress variation amplitude;

[0113] The fatigue limit represents the maximum stress amplitude at which the wind turbine blade material will not fail due to fatigue in the number of cycles under different wind speed and turbulence conditions;

[0114] Based on historical wind load data and a three-dimensional turbulent wind field model, the extreme environmental parameters of the kth dangerous section in the juth potential resonance risk node are determined. The extreme environmental parameters include the maximum wind speed, the maximum turbulence condition, and the corresponding aerodynamic load value and angle of attack.

[0115] A simulation test is performed on the wind turbine blade under extreme environmental parameters to obtain the fatigue damage data corresponding to the kth dangerous section, and the number of load cycles, stress amplitude and fatigue limit included in the fatigue damage data are marked as {N f,k , Δσ k , σ fl,k}; and k∈{1,2,…,K};

[0116] Under extreme environmental parameters, through experimental simulation or expert group system analysis, the upper limit threshold of fatigue damage of the kth dangerous section is expressed as {N f,k,th , Δσ k,th , σ fl,k,th}; where N f,k,th , Δσ k,th , σ fl,k,th For {N f,k , Δσ k , σ fl,k}The upper limit threshold of fatigue damage corresponding to the data in;

[0117] {N f,k , Δσ k , σ fl,k} and {N f,k,th , Δσ k,th , σ fl,k,th The corresponding values ​​in} are calculated in a ratio manner to obtain the following analysis results, and S ju,k The analysis result is defined as the fatigue damage value D ju,k , the analysis content is as follows:

[0118] If {N f,k , Δσ k , σ fl,k When the ratios of all values ​​in} to the corresponding fatigue damage upper limit threshold are less than 1, D ju,k The output value is 0, indicating that the dangerous section S ju,k The condition is normal and the fatigue damage is within the safe range;

[0119] If {N f,k , Δσ k , σ fl,k When the ratio between at least one value and the corresponding fatigue damage upper threshold is equal to 1, and the ratio between the remaining values ​​and the corresponding fatigue damage upper threshold is less than 1, D ju,k The output value is 1; it indicates the dangerous section S ju,k At the safety threshold limit;

[0120] If {N f,k , Δσ k , σ fl,k}There is at least one value that matches When the corresponding comparison results are ju,k The output value is 2; it indicates the dangerous section S ju,k It is the key dangerous section;

[0121] The key dangerous sections are screened out to form a sequence set of key dangerous sections at the juth potential resonance risk node {S ju,1 ,S ju,2 ,…,S ju,h ,…,S ju,H}, where S ju,h represents the index of the hth critical dangerous section in the juth potential resonance risk node, and H is the total number of critical dangerous sections in the corresponding potential resonance risk node; H≤K, and {S ju,1 ,S ju,2 ,…,S ju,h ,…,S ju,H}∈{S ju,1 ,S ju, 2,…,S ju,k ,…,S ju,K};

[0122] For each critical dangerous section, extract the corresponding load form vibration shape;

[0123] Set the incremental pneumatic load starting from 1, and increase by 10% of the previous load each time, and increase by 10N each time until the maximum load value is reached. The sequence set of incremental pneumatic load is expressed as Among them, Qd 1 with Qd V Respectively represent the initial value and maximum value of the aerodynamic load; Qd v represents the vth aerodynamic load value, and v∈[1,V]; ensure that the loading process simulates the changes in actual wind conditions; the maximum load value is determined based on historical monitoring data or determined by an expert group through experimental data.

[0124] Further explanation: the acquisition of the secondary screening strategy specifically includes:

[0125] Apply a preset incremental pneumatic load {Qd 1 ,Qd 2 ,…,Qd v ,…,Qd V}, gradually increase the load intensity and record the response of each critical dangerous section under different aerodynamic loads;

[0126] Under each aerodynamic load condition, high-precision sensors are used to record the vibration displacement data of each critical dangerous section, and the critical dangerous section S ju,h Under aerodynamic load Qd v The vibration displacement under

[0127] Analyze the relationship between vibration displacement data and aerodynamic loads, and the specific judgment criteria for the secondary screening strategy are:

[0128] If the critical dangerous section S ju,h Upper aerodynamic load Qd v Every 10% increase, i.e. Qd v →Qd v+1 , then the corresponding vibration displacement The change is less than or equal to 5%, indicating that the system is stable;

[0129] If the critical dangerous section S ju,h Upper aerodynamic load Qd v For every 10% increase in vibration displacement The change is (5%, 15%), indicating that the vibration response is average;

[0130] If the critical dangerous section S ju,h Upper aerodynamic load Qd v For every 10% increase in vibration displacement If the change is more than 15%, the critical dangerous section is a high-risk area and needs to be monitored;

[0131] The corresponding critical dangerous section in the high-risk area is taken as the final dangerous section.

[0132] Further explanation: 4.1) Design of blade structure specimen:

[0133] Software tool selection: Choose computer-aided design software SolidWorks or AutoCAD for specimen design;

[0134] Parametric design: Establish a parametric 3D model of the specimen based on the dangerous sections determined in the secondary screening strategy; ensure that the design parameters in the parametric 3D model include blade length, width, thickness, curvature, mass, and stiffness;

[0135] Use finite element analysis software ANSYS or Abaqus to conduct preliminary verification of the above parametric design, check the stress distribution and deformation under the expected load, and ensure the safety and stability of the structure;

[0136] 4.2) Material selection and processing:

[0137] Material specification confirmation: Confirm that the same material as the wind turbine blade is used, obtain the material technical specification, and ensure that the material performance meets the requirements of fatigue resistance, elastic modulus, and strength;

[0138] Processing technology selection: Select the appropriate processing technology according to the material type:

[0139] For composite materials, choose compression molding or vacuum assisted resin transfer molding (VARTM) processes;

[0140] For metal materials, choose CNC milling or laser cutting.

[0141] Further explanation: installing the blade structure test piece;

[0142] 5.1) Fixture setting:

[0143] Fixture design: Design an adjustable spacing fixture to ensure that it can adapt to different stress conditions, and adjust the length and clamping force of the fixture to adapt to the characteristics of the specimen;

[0144] Material selection: The fixture is made of high-strength aluminum alloy or steel to ensure that it does not deform during the test;

[0145] Install the test piece: Fix the machined blade structure test piece on the fixture to ensure that it does not slide or loosen during the test; use bolts, fixtures and dowel pins to enhance the fixing effect;

[0146] 5.2) Connect the test equipment:

[0147] Ultrasonic fatigue testing machine connection: Connect the fixture to the ultrasonic fatigue testing machine through an adapter to ensure good mechanical contact between the fixture and the testing machine to avoid unnecessary vibration interference during the test.

[0148] Further, ultrasonic fatigue testing was performed;

[0149] 6.1) Test parameter setting:

[0150] Load setting: Set the load amplitude according to the force of the wind turbine blade under actual working conditions, and set the test at different frequencies and amplitudes to ensure a comprehensive assessment of the fatigue characteristics of the structure;

[0151] Frequency selection: The frequency of the ultrasonic fatigue testing machine is set between 50Hz and 20kHz, and is selected according to the operating instructions of the equipment;

[0152] Monitoring system setup: Use the data acquisition system NIDAQ or LabVIEW to monitor the response of the blade structure specimen in real time, and set strain gauges and accelerometers on the blade structure specimen to collect vibration data;

[0153] 6.2) Start the testing machine:

[0154] After starting the test machine, the vibration of the blade structure specimen is monitored in real time, and the vibration data and surface state of the blade structure specimen are recorded. The vibration data includes vibration displacement and stress response, and the surface state includes judging whether cracks and deformation occur on the blade structure specimen;

[0155] Description of cracks: If cracks appear on the blade structure specimen at a given high-frequency vibration frequency, the given high-frequency vibration frequency is used as the warning threshold for cracks on the blade structure specimen;

[0156] Explanation of deformation: If the blade structure specimen has a deformation of more than 5% of its surface area at a given high-frequency vibration frequency, the given high-frequency vibration frequency shall be used as the warning threshold for deformation of the blade structure specimen;

[0157] 6.4) Test data analysis:

[0158] Data collation: Import the collected vibration displacement, stress response and other related data into the data analysis software MATLAB;

[0159] Graphical analysis: Generate response curves, strain-time graphs, and frequency response graphs to intuitively analyze the fatigue behavior of blade structure specimens under different loads;

[0160] 6.5) Failure mechanism evaluation:

[0161] Analyze fatigue behavior: Based on the data analysis results, evaluate the fatigue life of the specimen, identify the fatigue failure mode under different loads, and focus on the appearance and propagation of cracks;

[0162] Combining material properties and test results, the failure mechanisms of high cycle fatigue, low cycle fatigue and transient stress concentration are analyzed.

[0163] Fatigue life assessment:

[0164] For the force-life curve represented by the SN curve: establish the relationship between the stress amplitude Δσ and the fatigue life:

[0165]

[0166] Where N′ is the number of cycles of fatigue life, e1 and e2 are material constants, which are determined according to the expert group system;

[0167] The design range of Δσ is set to be within Δσ=50MPa, and the fatigue life N′ is ≥10 8 Number of cycles;

[0168] If Δσ increases by 10%, that is, Δσ becomes 55MPa, then N′ decreases by 20%, otherwise, N′ increases by 20%;

[0169] Fatigue failure mode identification, including:

[0170] The judgment criteria for crack monitoring are as follows:

[0171] On the surface of the blade structure specimen, when the length of each crack exceeds 0.1mm, it is judged as a crack; if the number of cracks exceeds 5, it is judged as a serious failure; for each crack that appears, the failure risk of the blade structure specimen is judged to increase by 20%;

[0172] The judgment criteria for deformation monitoring are as follows:

[0173] If the surface area deformation of the blade structure specimen exceeds 5%, it is judged to be deformation failure; at this time, if the deformation range expands to 10%, the failure risk increases to 40%;

[0174] Use a laser distance meter to quantify. If the deformation of the specimen surface is 7%, the machine needs to be stopped immediately for inspection.

[0175] Fatigue behavior analysis, including:

[0176] The judgment criteria for cyclic load analysis are as follows:

[0177] Analyze the stress amplitude Δσ at each high-frequency vibration frequency; when the maximum value of the stress amplitude Δσ exceeds 10% of the design value, a detailed analysis is required; if the maximum value of the stress amplitude Δσ is 110MPa, it needs to be recorded and analyzed;

[0178] Failure mechanism classification and quantification, including:

[0179] Judgment criteria for high cycle fatigue and low cycle fatigue:

[0180] High cycle fatigue: when the number of cycles N′≥10 6 , and the stress amplitude Δσ is less than 100MPa, which is defined as high cycle fatigue; at this time, the failure probability is 10%;

[0181] Low cycle fatigue: When the number of cycles N' is less than 10 6 , and the stress amplitude Δσ is greater than 200MPa, which is defined as low-cycle fatigue; at this time, the failure probability is 60%;

[0182] The criteria for judging instantaneous force concentration are as follows:

[0183] If the peak stress caused by the instantaneous load is 150% of the average stress, it is judged as instantaneous force concentration;

[0184] If the average force is 80MPa and the instantaneous force peak reaches 120MPa, a detailed analysis is required because the failure probability increases from 10% to 50%.

[0185] Embodiment 2:

[0186] See also Figures 2 to 5 , a wind turbine blade ultra-high cycle fatigue performance test device, the device is used to perform the wind turbine blade ultra-high cycle fatigue performance test method, comprising:

[0187] The test device includes an adjustable spacing fixture 5 for installing a blade structure specimen, and an ultrasonic pressure head 4 connected in sequence through a transducer 1, an actuator 2 and a margin rod 3, a working end of the ultrasonic pressure head 4 contacts a point to be tested on the blade structure specimen, and the blade structure specimen includes a blade circumferential structure specimen 8 or a blade radial structure specimen 9; the test device also includes an ultrasonic generator 6 connected to the transducer 1, and the ultrasonic generator 6 is connected to a control system computer 7 to realize the generation of test signals and data processing;

[0188] The transducer 1 converts the electrical signal into mechanical vibration, transmits it to the amplitude rod 3 to adjust the amplitude, and then optimizes the system configuration through the actuator 2. Finally, the ultrasonic pressure head 4 efficiently transmits the vibration energy to the blade structure specimen;

[0189] Data acquisition module: collects historical wind load data of wind turbine blades under different wind speed and turbulence conditions, including the actual values ​​of wind speed and air pressure measured under these conditions, as well as the corresponding aerodynamic load values ​​and the angle of attack of the wind turbine blades relative to the wind;

[0190] 3D turbulent wind field model building module: used to build a parametric 3D model of wind turbine blades and import it into finite element analysis software to obtain the collected historical wind load data and build a 3D turbulent wind field model that is consistent with the current actual wind load environment;

[0191] The three-dimensional turbulent wind field model is applied as an external load to the parametric three-dimensional model of the wind turbine blade. The force of the wind turbine blade under different wind speeds and turbulence conditions is analyzed by finite element analysis software, and M potential dangerous nodes with common characteristics are screened out.

[0192] At the same time, modal analysis is performed on the parameterized three-dimensional model to screen out potential resonance risk nodes from the M potential dangerous nodes, and obtain the natural frequency and load form vibration shape of each potential resonance risk node;

[0193] Key dangerous section determination module: used to determine several dangerous sections corresponding to each potential resonance risk node according to the potential resonance risk nodes identified by the finite element analysis results;

[0194] Collect the fatigue damage data of each dangerous section under different wind speed and turbulence conditions, and set the upper limit threshold of fatigue damage for each dangerous section based on the finite element analysis results. Screen out the dangerous sections with a value greater than the upper limit threshold of fatigue damage to form key dangerous sections. Combine the natural frequency and load form vibration mode of each key dangerous section to perform incremental aerodynamic load simulation.

[0195] Final dangerous section determination module: used to record the vibration displacement data of each critical dangerous section under different loads during the simulation of incremental aerodynamic loads, analyze the collected vibration displacement data, and generate a secondary screening strategy for screening the final dangerous section from these critical dangerous sections;

[0196] Test specimen test module: used to design a blade structure specimen with the same final dangerous section as the secondary screening strategy, and processed with the same material as the original wind turbine blade;

[0197] The blade structure specimen is mounted on an adjustable spacing fixture that can adapt to different stress conditions, and the fixture is connected to an ultrasonic fatigue testing machine for high-frequency vibration testing;

[0198] Set the test parameters, start the ultrasonic fatigue testing machine, monitor the response of the blade structure specimen under high-frequency vibration, and record the test data.

[0199] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0200] The above embodiments may be implemented in whole or in part by software, hardware, firmware or any other combination thereof. When implemented by software, the above embodiments may be implemented in whole or in part in the form of a computer program product. Those skilled in the art may appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein may be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed by hardware or software methods depends on the specific application and design constraints of the technical solution.

[0201] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, and may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0202] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A method for testing the ultra-high cycle fatigue performance of wind turbine blades, characterized in that: The specific steps include: Step S1: according to the current actual wind load environment, determine the wind speed range and turbulence level range, and perform simulation tests under the wind speed range and turbulence level range to obtain historical wind load data within different range combinations, the historical wind load data including the actual values ​​of wind speed and air pressure, and the corresponding aerodynamic load value and the angle of attack of the wind turbine blade relative to the wind; Step S2: construct a three-dimensional turbulent wind field model based on historical wind load data, and establish a parametric three-dimensional model of a wind turbine blade, apply the three-dimensional turbulent wind field model as an external load to the parametric three-dimensional model of the wind turbine blade, analyze the stress conditions of the wind turbine blade under different wind speeds and turbulence conditions through finite element analysis software, screen out M potential dangerous nodes with common characteristics, and perform modal analysis on the parametric three-dimensional model to screen out potential resonance risk nodes from the M potential dangerous nodes, and obtain the natural frequency and load form vibration mode of each potential resonance risk node; Step S3: determining a number of dangerous sections corresponding to each potential resonance risk node according to the potential resonance risk nodes identified by the finite element analysis result; Collect the fatigue damage data of each dangerous section under different wind speed and turbulence conditions, and set the upper limit threshold of fatigue damage for each dangerous section based on the finite element analysis results. Screen out the dangerous sections with a value greater than the upper limit threshold of fatigue damage to form key dangerous sections. Combine the natural frequency and load form vibration mode of each key dangerous section to perform incremental aerodynamic load simulation. Step S4: During the simulation of the incremental aerodynamic load, the vibration displacement data of each critical dangerous section under different loads are recorded, and the collected vibration displacement data are analyzed to generate a secondary screening strategy for screening the final dangerous section from the critical dangerous sections; Step S5: Design a blade structure specimen with the same final dangerous section as that provided by the secondary screening strategy, use the same material as the original wind turbine blade for processing, and perform a high-frequency vibration test on the blade structure specimen.

2. A method for testing ultra-high cycle fatigue performance of wind turbine blades according to claim 1, characterized in that: Acquisition of historical wind load data, including: 1.1) Determine wind turbine parameters and operating condition settings: Use the wind speed range consisting of the maximum wind speed and the minimum wind speed in the historical wind load data as the value range of different wind speeds, determine the turbulence level classification according to the international standard IEC61400, and match the historical turbulence condition data of the area where the wind turbine blades are located with the turbulence level to cover all operating conditions; 1.2) Wind load calculation software settings; determine the design parameters of the wind turbine blades on the wind turbine, which are blade length, width, thickness, curvature, mass, and stiffness, and input the design parameters into the load calculation software GH-Bladed, and set the aerodynamic model parameters of angle of attack, lift, and drag coefficients; 1.3) Working condition simulation and historical wind load data collection: Use GH-Bladed to calculate the wind load under various set wind speeds and turbulence conditions, obtain wind load data under different working conditions, and summarize these wind load data as historical wind load data; 1.4) Analysis and compilation of historical wind load data; 1.5) Output and report generation: turbulence conditions including turbulence intensity, wind speed distribution and turbulence structure parameters; The angle of attack refers to the angle between the chord direction of the wind turbine blade and the incoming wind; The aerodynamic load value refers to the aerodynamic load value borne by the wind turbine blade under different combinations of wind speed, air pressure and attack angle.

3. A method for testing ultra-high cycle fatigue performance of wind turbine blades according to claim 2, characterized in that: Screen out M potential dangerous nodes with common characteristics, and determine the natural frequency and load form vibration mode of each potential dangerous node, including: 2.1) Parametric 3D modeling of wind turbine blades: According to the blade design parameters, choose SolidWorks, CATIA or Creo to perform parametric 3D modeling for wind turbine blades; 2.2) Import parametric 3D modeling into finite element analysis software: Use the meshing tool in the finite element software to divide the imported parameterized 3D model into N mesh regions, and set i to represent the i-th mesh region, and i∈[1,N]; 2.3) Construct a three-dimensional turbulent wind field model: Use fluid dynamics software FLUENT or OpenFOAM to establish a three-dimensional turbulent wind field model consistent with historical wind load data; The three-dimensional turbulent wind field model is coupled with the finite element model of the wind turbine blade to ensure that the wind load can act on the parametric three-dimensional modeling of the wind turbine blade in real time during the analysis process; 2.4) Apply external loads and perform finite element analysis: In the finite element analysis software, the constructed three-dimensional turbulent wind field model is applied as an external load to the parametric three-dimensional modeling of the wind turbine blades; Select dynamic analysis to analyze the stress of wind turbine blades under different wind speeds and turbulence conditions, and obtain the stress analysis results under each simulated working condition; 2.5) Identify potentially dangerous nodes: The stress analysis results are post-processed to screen out M potential dangerous nodes with common characteristics under different wind speed and turbulence conditions, including: According to the yield strength of the material used in the wind turbine blade, 55% of the yield strength is defined as the stress threshold ST; In the N grid areas divided by the parameterized three-dimensional model of the wind turbine blade, the maximum principal stress exceeding ST under different wind speed and turbulence conditions is used as a screening rule, and the grid areas that meet the screening rule are screened out as potential dangerous nodes with common characteristics; The M potential dangerous nodes are represented by a sequence set {1, 2, ..., j, ..., M}, where j represents the index of the jth potential dangerous node, and each potential dangerous node has a corresponding position in the N grid areas; If the number of potential dangerous nodes M finally identified is within 5, that is, M≤5, it means that the safety of the wind turbine blade design is good. When M>5, it means that the safety of the wind turbine blade design is poor and the safety of the wind turbine blade design needs to be improved. 2.6) Perform modal analysis: Select the "Modal Analysis" module in the finite element software and set the analysis scope to ensure that the natural frequencies of all potentially dangerous nodes are examined, including: Simulate the dynamic response of wind turbine blades at different frequencies to identify potential resonant frequencies; set the natural frequency threshold to 85% of the first resonant frequency in modal analysis, and record the natural frequency threshold as NFT; When the natural frequency of a potential dangerous node is less than NFT, it is recorded as a potential resonance risk node, and each potential resonance risk node is represented by a sequence set as ju = {j1, j2, ..., jU}, where ju represents the index of the juth potential resonance risk node, JU represents the total number of potential resonance risk nodes, and ju∈{1,2, ..., j, ..., M}; Run a modal analysis to obtain the natural frequencies and load mode shapes for each node at potential resonance risk, including flapping and shimmy modes.

4. A method for testing ultra-high cycle fatigue performance of wind turbine blades according to claim 3, characterized in that: Determine several dangerous sections corresponding to each potential resonance risk node, screen out dangerous sections that are greater than the upper threshold of fatigue damage, and perform incremental aerodynamic load simulation based on the natural frequency and load form of each potential resonance risk node, including: For the juth potential resonance risk node, determine the corresponding several dangerous sections to form a dangerous section sequence set {S ju,1 ,S ju,2 ,…,S ju,k ,…,S ju,K }, where S ju,k represents the index of the kth dangerous section in the juth potential resonance risk node, and K is the total number of dangerous sections in the corresponding potential resonance risk node; Fatigue damage data include the number of load cycles, stress amplitude and fatigue limit of wind turbine blade materials under different wind speed and turbulence conditions; The stress amplitude is the stress variation amplitude of the wind turbine blade material under cyclic load; The number of load cycles represents the number of load cycles that the wind turbine blade material can withstand under a given stress variation amplitude; The fatigue limit represents the maximum stress amplitude at which the wind turbine blade material will not fail due to fatigue in the number of cycles under different wind speed and turbulence conditions; Based on historical wind load data and a three-dimensional turbulent wind field model, the extreme environmental parameters of the kth dangerous section in the juth potential resonance risk node are determined. The extreme environmental parameters include the maximum wind speed, the maximum turbulence condition, and the corresponding aerodynamic load value and angle of attack. A simulation test is performed on the wind turbine blade under extreme environmental parameters to obtain the fatigue damage data corresponding to the kth dangerous section, and the number of load cycles, stress amplitude and fatigue limit included in the fatigue damage data are marked as {N f,k , Δσ k , σ fl,k }; and k∈{1,2,…,K}; Under extreme environmental parameters, through experimental simulation or expert group system analysis, the upper limit threshold of fatigue damage of the kth dangerous section is expressed as {N f,k,th , Δσ k,th , σ fl,k,th }; where N f,k,th , Δσ k,th , σ fl,k,th For {N f,k , Δσ k , σ fl,k }The upper limit threshold of fatigue damage corresponding to the data in; {N f,k , Δσ k , σ fl,k } and {N f,k,th , Δσ k,th , σ fl,k,th The corresponding values ​​in} are calculated in a ratio manner to obtain the following analysis results, and S ju,k The analysis result is defined as the fatigue damage value D ju,k , the analysis content is as follows: If {N f,k , Δσ k , σ fl,k When the ratios of all values ​​in} to the corresponding fatigue damage upper limit threshold are less than 1, D ju,k The output value is 0, indicating that the dangerous section S ju,k The condition is normal and the fatigue damage is within the safe range; If {N f,k , Δσ k , σ fl,k When the ratio between at least one value and the corresponding fatigue damage upper threshold is equal to 1, and the ratio between the remaining values ​​and the corresponding fatigue damage upper threshold is less than 1, D ju,k The output value is 1, indicating the dangerous section S ju,k At the safety threshold limit; If {N f,k , Δσ k , σ fl,k }There is at least one value that matches When the corresponding comparison results are ju,k The output value is 2, indicating the dangerous section S ju,k It is the key dangerous section; The key dangerous sections are screened out to form a sequence set of key dangerous sections at the juth potential resonance risk node {S ju,1 ,S ju,2 ,…,S ju,h ,…,S ju,H }, where S ju,h represents the index of the hth critical dangerous section in the juth potential resonance risk node, and H is the total number of critical dangerous sections in the corresponding potential resonance risk node; H≤K, and {S ju,1 ,S ju,2 ,…,S ju,h ,…,S ju,H }∈{S ju,1 ,S ju,2 ,…,S ju,k ,…,S ju,K }; For each critical dangerous section, extract the corresponding load form vibration shape; The incremental aerodynamic load is set to start from 1 and increase by 10% each time until the maximum load value is reached. The sequence set of incremental aerodynamic load is expressed as The maximum load value is determined based on historical monitoring data or experimental data by an expert group; Among them, Qd1 and Qd V Respectively represent the initial value and maximum value of the aerodynamic load; Qd v represents the vth aerodynamic load value, and v∈[1,V].

5. A method for testing ultra-high cycle fatigue performance of wind turbine blades according to claim 4, characterized in that: The acquisition of secondary screening strategies includes: Apply a preset incremental aerodynamic load {Qd1, Qd2, …, Qd v ,…,Qd V }, gradually increase the load intensity and record the response of each critical dangerous section under different aerodynamic loads; Under each aerodynamic load condition, record the vibration displacement data of each critical dangerous section and calculate the critical dangerous section S ju,h At the vth aerodynamic load Qd v The vibration displacement under Analyze the relationship between vibration displacement data and aerodynamic loads, and the specific judgment criteria for the secondary screening strategy are: If the critical dangerous section S ju,h Upper aerodynamic load Qd v Every 10% increase, i.e. Qd v →Qd v+1 , then the corresponding vibration displacement The change is less than or equal to 5%, indicating that the system is stable; If the critical dangerous section S ju,h Upper aerodynamic load Qd v For every 10% increase in vibration displacement The change is (5%, 15%), indicating that the vibration response is average; If the critical dangerous section S ju,h Upper aerodynamic load Qd v For every 10% increase in vibration displacement If the change is more than 15%, the critical dangerous section is a high-risk area and needs to be monitored; The corresponding critical dangerous section in the high-risk area is taken as the final dangerous section.

6. A wind turbine blade ultra-high cycle fatigue performance test device, characterized in that: The device is used to perform the wind turbine blade ultra-high cycle fatigue performance test method according to any one of claims 1 to 5, comprising: The test device includes an adjustable spacing fixture for installing a blade structure specimen, and an ultrasonic pressure head connected in sequence through a transducer, an actuator and a width rod, and the blade structure specimen includes a blade circumferential structure specimen or a blade radial structure specimen; the test device also includes an ultrasonic generator connected to the transducer, and the ultrasonic generator is connected to a control system computer; Data acquisition module: Determine the wind speed range and turbulence level range according to the current actual wind load environment, and conduct simulation tests under the wind speed range and turbulence level range to obtain historical wind load data within different range combinations. The historical wind load data includes the actual values ​​of wind speed and air pressure, as well as the corresponding aerodynamic load value and the angle of attack of the wind turbine blade relative to the wind; Three-dimensional turbulent wind field model construction module: construct a three-dimensional turbulent wind field model based on historical wind load data, and establish a parametric three-dimensional model of wind turbine blades. Apply the three-dimensional turbulent wind field model as an external load to the parametric three-dimensional model of wind turbine blades. Use finite element analysis software to analyze the stress conditions of wind turbine blades under different wind speeds and turbulence conditions, and select M potential dangerous nodes with common characteristics. Perform modal analysis on the parametric three-dimensional model to select potential resonance risk nodes from the M potential dangerous nodes, and obtain the natural frequency and load form vibration mode of each potential resonance risk node; Key dangerous section determination module: used to determine several dangerous sections corresponding to each potential resonance risk node according to the potential resonance risk nodes identified by the finite element analysis results; Collect the fatigue damage data of each dangerous section under different wind speed and turbulence conditions, and set the upper limit threshold of fatigue damage for each dangerous section based on the finite element analysis results. Screen out the dangerous sections with a value greater than the upper limit threshold of fatigue damage to form key dangerous sections. Combine the natural frequency and load form vibration mode of each key dangerous section to perform incremental aerodynamic load simulation. Final dangerous section determination module: used to record the vibration displacement data of each critical dangerous section under different loads during the simulation of incremental aerodynamic loads, analyze the collected vibration displacement data, and generate a secondary screening strategy for screening the final dangerous section from these critical dangerous sections; Specimen testing module: used to design blade structure specimens with the same final dangerous cross-section as the secondary screening strategy, and process them with the same material as the original wind turbine blades, and perform high-frequency vibration tests on the blade structure specimens.

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