Wind power blade subcomponent structure bending and torsion loading failure analysis and optimization method

Abstract

The application discloses a wind power blade subcomponent structure bending-torsion loading failure analysis and optimization method, and belongs to the technical field of wind power blade structure mechanics analysis. The analysis method establishes a three-dimensional entity finite element model of a wind power blade subcomponent, applies pure oscillation, pure torsion and gradient bending-torsion combined load for nonlinear static force analysis, extracts critical failure point data, compares and analyzes trailing edge buckling waveforms, adhesive failure migration and contact behavior changes, determines the internal correlation between trailing edge adhesive structure failure and buckling waveforms and contact behavior under the bending-torsion coupling condition, determines the migration law of the trailing edge failure position with the torsion angle and the stress distribution difference between the leading edge and the trailing edge, solves the problem that the prior art cannot accurately locate the vulnerable area of the blade under bending-torsion coupling, and provides a mechanical basis for blade structure optimization. The analysis result obtained by the analysis method can be directly used to guide the bending-torsion coupling resistance design of the blade.

Description

Technical Field

[0001] This invention relates to the field of structural mechanical analysis technology for wind turbine blades, specifically to a method for analyzing and optimizing the failure of wind turbine blade sub-components under bending and torsional loading. Background Technology

[0002] With the rapid development of the wind power industry, wind turbine blades are evolving towards larger sizes, exhibiting increasingly pronounced long and flexible characteristics. This leads to deviations in blade torsion angles from design values ​​during actual operation, resulting in unstable operating attitudes. This not only reduces aerodynamic efficiency but may also induce high-frequency aerodynamic noise and structural vibrations. More critically, the reduced torsional natural frequency of large blades makes them prone to coupling with low-order bending modes, triggering torsional deformation transmission in the main beam cap. This results in nonlinear superposition of mechanical responses, altering the blade collapse failure mode, reducing the accuracy of life prediction models, and seriously threatening the safe operation of wind turbine units. Whether improving wind energy utilization or exploring blade aerodynamic performance, related research is based on the stability of the blade structure. If the blade structure is damaged, the above research becomes meaningless. Therefore, conducting research on the mechanical properties of blade structures under torsional and combined bending-torsional loads is of great significance.

[0003] Current research on the mechanical properties of wind turbine blades largely focuses on single load conditions or simplified specimens such as box girders and I-beams, making it difficult to accurately reflect the local mechanical behavior of key sub-regions of large blades under actual bending-torsional coupling conditions. Full-scale testing of large blades is costly, and precise verification of local mechanical behavior is challenging. Existing technologies for blade structural analysis under bending-torsional coupling conditions lack sufficient understanding of the failure mechanisms in the trailing edge critical region, failing to provide accurate mechanical basis for structural optimization of key blade regions and hindering the improvement of the reliability of large wind turbine blade structures. Therefore, there is an urgent need for a blade sub-region mechanical response analysis technique adapted to bending-torsional coupling conditions to provide technical support for blade structural design optimization. Summary of the Invention

[0004] The purpose of this invention is to address the problem of insufficient analysis of the local failure mechanism of wind turbine blades under combined bending and torsional loads in existing technologies. It provides a refined and predictable structural failure analysis method for wind turbine blade sub-components under combined bending and torsional loads to reveal the influence of bending and torsional coupling on the failure behavior of trailing edge bonded structures. Furthermore, the analysis results obtained by the method can be directly used for the structural optimization design of wind turbine blade sub-components to improve the structural reliability and stability of wind turbine blades.

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

[0006] This invention provides a method for analyzing the failure of wind turbine blade components under bending and torsional loading, comprising the following steps:

[0007] (1) Establish a three-dimensional solid finite element model of the wind turbine blade component. The three-dimensional solid finite element model is constructed based on the airfoil and material layup data of the target blade. It includes the leading edge, leading edge plate, trailing edge, trailing edge plate, trailing edge reinforcement area, beam cap, web and corresponding bonding structure. The model is given corresponding composite material properties and cohesive force model of bonding structure for different regions.

[0008] (2) Apply a fixed constraint to one end of the three-dimensional solid finite element model, and apply a swaying displacement load and a torsional load around the aerodynamic center to the other end by means of reference point coupling, respectively or simultaneously, to simulate pure swaying, pure torsional loading and bending-torsional combined loading conditions.

[0009] (3) Under the combined bending and torsion loading condition, the displacement load in the swing direction is kept constant, and a torsion load lower than the critical failure angle of pure torsion loading is applied in a gradient manner to perform nonlinear static analysis;

[0010] (4) By monitoring the force-displacement or moment-rotation curves of the loading reference points RP-1 and RP-2 respectively, the critical structural failure point of the blade sub-component is determined, and the buckling waveform of the trailing edge below the failure point, the failure cloud map of the bonded structure, and the contact behavior data of the trailing edge reinforcement area are extracted; among them, the two reference points RP-1 and RP-2 are used for shimmy and torsional loading respectively. Reference point RP-2 is located at 27.5% of the maximum chord length from the leading edge, which is the aerodynamic center of the airfoil of the blade sub-component. Reference point RP-1 is set at 1.5 times the maximum chord length from the leading edge;

[0011] (5) Compare and analyze the peak-to-peak distribution of the buckling waveform of the trailing edge under different torsional gradients, the migration law of the starting position of the adhesive failure, and the changes in the contact stress and contact area of ​​the trailing edge reinforcement zone. Establish the correlation between the failure of the trailing edge adhesive structure and the buckling waveform and contact behavior under the combined bending and torsional loading condition, so as to predict the failure mode of the blade sub-component under the combined bending and torsional loading condition.

[0012] Furthermore, in step (1), the cohesive model selected for the bonded structure is a bilinear constitutive model, and the stiffness degradation initiation determination adopts the secondary stress criterion.

[0013] Furthermore, in step (3), the critical failure angle of pure torsional loading is determined in the following way: during the simulation of pure torsional loading, a torsional load around the aerodynamic center is applied to the three-dimensional solid finite element model until the structure fails, and the torsional angle corresponding to the load drop point is obtained.

[0014] Furthermore, in step (4), by extracting the Mises stress distribution along different positions along the span and along the chord path of the blade sub-component, the stress distribution in the leading edge region under combined bending and torsion loading is similar to that under pure torsion conditions, and the stress distribution in the trailing edge region is similar to that under pure oscillation conditions.

[0015] This invention also provides a method for optimizing the structure of wind turbine blade components, based on the failure analysis results of the aforementioned method for analyzing the failure of wind turbine blade component structures under bending and torsional loading, specifically including:

[0016] (1) Based on the analysis results of high stress concentration in the rear edge reinforcement zone under combined bending and torsion loading, strengthen the layup design of the composite laminate in this area or add reinforcing materials.

[0017] (2) Based on the analysis results of the high stress band that appears in the width direction of the rear edge web under the combined bending and torsion loading condition, optimize the geometric parameters of the web and beam cap bonding structure or select a higher performance structural adhesive.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0019] This invention, through gradient bending-torsional combined loading, multi-dimensional data extraction, and correlation analysis, clarifies the intrinsic relationship between the failure of the trailing edge adhesive structure and the buckling waveform and contact behavior of blades under bending-torsional coupling conditions. It also clarifies the migration law of the trailing edge failure location with the torsional angle and the difference in stress distribution between the leading and trailing edges, solving the problem of accurately locating vulnerable areas of blades under bending-torsional coupling in existing technologies, and providing a mechanical basis for blade structure optimization. The analytical results obtained through the analytical method of this invention can be directly used to guide the design of blades to resist bending-torsional coupling. Compared with expensive full-size blade tests, this method, through refined finite element analysis at the sub-component level, can predict and evaluate the weak points of blades under complex loads at a lower cost, accelerating the research and development process. Attached Figure Description

[0020] Figure 1 This is a diagram showing the region division of the wind turbine blade airfoil selected in Embodiment 1 of the present invention;

[0021] Figure 2 This refers to the three-dimensional solid finite element model of the blade sub-component constructed in Embodiment 1 of the present invention;

[0022] Figure 3 This is a schematic diagram of the blade layup direction in Embodiment 1 of the present invention;

[0023] Figure 4 The cohesive bilinear constitutive model in Embodiment 1 of this invention;

[0024] Figure 5 This refers to the three-dimensional solid finite element model of the blade sub-component and its boundary conditions in Embodiment 1 of the present invention.

[0025] Figure 6 When the oscillation is loaded in Embodiment 1 of the present invention Figure 5 Force-displacement curve at point RP-1;

[0026] Figure 7 These are trailing edge buckling waveforms at different stages under oscillation loading in Embodiment 1 of the present invention.

[0027] Figure 8 The following are failure contour maps of the blade sub-component bonding structure under tumbling loading in Embodiment 1 of the present invention: (a) is the failure contour map under 30% buckling load, and (b)-(e) are respectively... Figure 6 Failure cloud map of points A1, A2, A3, and A4;

[0028] Figure 9 This describes the trailing edge contact behavior of a blade sub-component when bonding fails under oscillation loading in Embodiment 1 of the present invention.

[0029] Figure 10 When the torsional direction is loaded in Embodiment 1 of the present invention Figure 5 The torque-rotation angle curve at point RP-2;

[0030] Figure 11 This is a naming diagram of the bonding structure at the web position in Embodiment 1 of the present invention;

[0031] Figure 12 The above are failure cloud diagrams of the bonding structure of the blade sub-component under torsional loading in Embodiment 1 of the present invention. (a)-(e) are respectively Figure 10 Failure cloud map of points TA1, TA2, TA3, TA4, and TA5;

[0032] Figure 13 The force-displacement curves at point RP-1 under bending-torsion combined loading conditions with different torsional angles in Embodiment 1 of the present invention are shown.

[0033] Figure 14 This refers to the trailing edge buckling wave in Embodiment 1 of the present invention when subjected to combined bending and torsion loading to the point of critical structural failure.

[0034] Figure 15 This refers to the initial debonding position of the trailing edge under combined bending and torsion loading in Embodiment 1 of the present invention.

[0035] Figure 16 This describes the contact behavior of the trailing edge under combined bending and torsion loading in Embodiment 1 of the present invention.

[0036] Figure 17 This is a stress analysis path diagram in Embodiment 1 of the present invention;

[0037] Figure 18 In Embodiment 1 of the present invention Figure 17Stress distribution on the pressure side of path 1, where (a) is the stress distribution along the chord length, and (b) is the stress distribution box diagram;

[0038] Figure 19 In Embodiment 1 of the present invention Figure 17 Stress distribution on the suction side of path 1, where (a) is the stress distribution along the chord length and (b) is the stress distribution box diagram;

[0039] Figure 20 In Embodiment 1 of the present invention Figure 17 Stress distribution on the pressure side of path 2, where (a) is the stress distribution along the chord length and (b) is the stress distribution box diagram;

[0040] Figure 21 In Embodiment 1 of the present invention Figure 17 Stress distribution on the suction side of path 2, where (a) is the stress distribution along the chord length, and (b) is the stress distribution box diagram;

[0041] Figure 22 In Embodiment 1 of the present invention Figure 17 Stress distribution on the pressure side of path 3, where (a) is the stress distribution along the chord length, and (b) is the stress distribution box diagram;

[0042] Figure 23 In Embodiment 1 of the present invention Figure 17 Stress distribution on the suction side of path 3, where (a) is the stress distribution along the chord length and (b) is the stress distribution box diagram;

[0043] Figure 24 The diagram shows the web stress cloud diagrams of the blade sub-components under different load conditions when the critical structure fails. (a) is the leading edge web and (b) is the trailing edge web. Detailed Implementation

[0044] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0045] Example 1

[0046] This embodiment uses a 61.5m long wind turbine blade as the target blade, selecting a transition region of 5m in length from 14.5m to 19.5m from the blade root as the research object for a sub-component. This length is slightly longer than the maximum chord length of the airfoil in this region (4.65m). This section of the blade has an airfoil of DU99-W-350 and adopts a double-web structure. The blade cross-sectional information is as follows: Figure 1 As shown, it includes a leading edge, a leading edge plate, a trailing edge, a trailing edge plate, a trailing edge reinforcement zone, a beam cap, and a web; used to verify the effectiveness of the failure analysis method of this invention. The specific implementation steps are as follows:

[0047] 1. Establishment of 3D Solid Finite Element Model: A 3D solid finite element model of the sub-component is constructed using ABAQUS finite element software, such as... Figure 2 As shown.

[0048] 2. Load and Constraint Settings: Set material properties and divide the model into 22 regions to facilitate material layup, including the leading edge, leading edge plate, trailing edge, trailing edge plate, trailing edge reinforcement zone, beam cap, web, and related bonding structures (including the web-beam cap bonding structure). Except for the bonding structures, which only have thickness direction settings, the other composite material layup regions have local coordinate systems set according to the actual layup direction, such as... Figure 3 As shown, the layers are laid inwards, with fibers along the spanning direction. Material properties were added using the "Create Composite Layer" module in the ABAQUS finite element software. The material property data used for the blades were referenced from the DOE / MSU database.

[0049] Table 1 Blade layup materials and their properties

[0050] ;

[0051] As shown in Table 1, E 11 This represents the elastic modulus of the composite material along the fiber direction, corresponding to the spanwise direction of the blade. E 22 This represents the elastic modulus of the composite material in the layup plane, perpendicular to the fiber direction, corresponding to the chord direction of the blade. E 33 It represents the elastic modulus of the composite material along the thickness of the layup, and its properties are mainly dominated by the matrix resin. ν 12 The Poisson effect represents the relationship between the principal direction of the fiber and the in-plane transverse direction. ν 13 This represents the Poisson effect between the principal fiber direction and the thickness direction. ν 23 This represents the Poisson effect between the transverse and thickness directions within the fiber plane. G 12 It represents the ability to undergo in-plane shear deformation, which is composed of the principal direction of the fiber and the transverse direction within the plane. G 13 It represents the ability to undergo in-plane shear deformation along the principal fiber direction and the thickness direction. G 23This represents the in-plane shear deformation capability formed by the transverse and thickness directions within the fiber plane. For missing material properties, the following method was used to supplement them: assuming the unidirectional composite material is transversely anisotropic, the modulus and Poisson's ratio in the layup direction of the unidirectional composite material are equivalent to the modulus and Poisson's ratio perpendicular to the fiber direction, while the shear modulus in the layup direction is estimated using methods for isotropic materials. The structural adhesive type used at the trailing edge and web is AV138. This type of structural adhesive is widely used in blade bonding, and its material properties are shown in Table 2. E Here is the elastic modulus in the thickness direction. G Shear modulus σ f For tensile failure strength, τ f Shear failure strength, GC I For tensile fracture toughness. GC II For shear fracture toughness, the critical fracture energy is determined using the Benzeggaggh-Kenane fracture criterion. η The mixing coefficient is the fracture energy.

[0052] Table 2 Material properties of bonded structures

[0053] ;

[0054] The cohesive bilinear constitutive model was selected as the failure model for the bonded structure. The cohesive bilinear constitutive model is a constitutive model used to describe the cracking or crack propagation behavior at material interfaces. It simulates the progressive interface failure process during fracture by introducing the relationship between cohesion and interfacial separation displacement. This model is widely used in composite materials, bonded joints, fracture mechanics, and other fields.

[0055] like Figure 4 As shown, the functional expression of the cohesive bilinear constitutive model can be written as: σ=L( 1 -D)K ,in: σ For normal contact stress, K For normal contact stiffness, L For contact gap, D The model consists of three stages: elasticity, stiffness degradation, and complete failure. In this invention, the secondary stress criterion is used to determine the initiation point of stiffness degradation, and its expression is as follows:

[0056]

[0057] In the above formula, σ n This represents the normal stress at the bonding interface. Indicates the normal failure strength of the adhesive material. σ sThis represents the first shear (tangential) stress at the adhesive interface. This indicates the failure strength of the adhesive material in the first shear direction. σ t This represents the second shear (tangential) stress at the adhesive interface. This indicates the failure strength of the adhesive material in the second shear direction.

[0058] After completing the geometric modeling and material settings for the blade, the model needs to be configured with element types, boundary conditions, contact behavior, analysis steps, and mesh generation. The finite element model of the blade is as follows: Figure 5 As shown, the X direction is the flapping direction of the blade, the Y direction is the flaring direction, and the Z direction is the spanwise direction of the blade. First, mesh generation is performed. Computers cannot directly process continuous physical structures; they need to be discretized into simple elements (such as triangles, tetrahedrons, etc.) connected by nodes to form an approximate mathematical model. Mesh quality directly affects the accuracy and efficiency of finite element analysis. High-quality meshes require regular elements, smooth size transitions, fine meshing in critical areas, and good boundary fit. Mesh density needs to balance problem complexity and computational resources; areas with stress concentration require fine meshes, while uniform areas can have coarser meshes. The model of this invention uses a structured mesh. After setting the global size, the trailing edge and web bonding structure areas are locally refined while ensuring node alignment to accurately capture the mechanical behavior of critical areas. After mesh generation, the element type needs to be set: C3D8R elements are used for solid composite materials, and COH3D8 elements are used for bonded structures. Both are based on structured meshes, possessing advantages such as simple structure, high accuracy, and high efficiency.

[0059] The model boundary conditions are set as follows: one end face is fixed, and the other end is used to apply tumbling and torsional loads to simulate the constraint state during blade testing. In the finite element analysis, to simplify the setting of section loads / constraints (avoiding the tediousness and errors of node-by-node operation), the model introduces reference points RP-1 (tumbling load) and RP-2 (torsional load). RP-2 is located at 27.5% of the maximum chord length from the leading edge (the aerodynamic center of the airfoil), and RP-1 is located at 1.5 times the maximum chord length from the leading edge (for easy modeling selection). Through the coupling constraint between the section and the reference point, loads / constraints can be applied to the reference point in a concentrated manner, which simplifies modeling and improves accuracy and efficiency. At the same time, it is necessary to avoid excessive constraints (coupling of the same node with multiple reference points). Therefore, the coupling region of RP-1 is the aerodynamic shape region 90mm from the loading end face, and the coupling region of RP-2 is the loading end face.

[0060] This invention uses the critical instability point where the blade's load-bearing capacity drops sharply under tumbling loading as a benchmark. Mesh convergence analysis is performed by monitoring the load-displacement response at reference point RP-1 (the load during the sudden drop in blade load-bearing capacity is the failure load, and the corresponding displacement at RP-1 is the failure displacement). Mesh verification is performed at six gradients, with a maximum global size of 180mm (6322 nodes) and a minimum of 40mm (92732 nodes). Due to the use of the "Create Composite Layer" function, only one mesh layer is set in the blade thickness direction, and accuracy is controlled by integration points (5 for the flange, and 10-24 for the remaining composite laminates). Analysis shows that the failure load and displacement exhibit good convergence with mesh refinement. When the number of nodes is 22476-92732 (global mesh 90-40mm), the failure load stabilizes at 2805.14-2925.58kN, and the displacement at 88.40-94.01mm, with relative variation decreasing to 4.20% and 6.09%, respectively. After weighing accuracy and efficiency, a global mesh size of 90mm (22476 nodes) was selected.

[0061] 3. Multi-condition loading and mechanical response analysis of wind turbine blade components:

[0062] (1) Loading in the pure oscillation direction: The displacement load of RP-1 in the oscillation direction is 120mm, pointing in the negative direction of the Z-axis. After the calculation is completed, the force-displacement curve of point RP-1 is extracted, as follows: Figure 6 The results show that the curve consists of four stages: a linear stage, a buckling stage, a sudden load drop stage, and a post-failure evolution stage. The period before point A1 is the linear stage, with stable trailing edge stiffness. The period from A1 to A2 is the buckling stage, where the trailing edge stiffness slightly decreases at point A1, and the structure buckles. The normalized slope of the curve decreases from 0.78 to 0.70 because the rapid increase in the trailing edge buckling wave amplitude during the linear stage alters the blade section's moment of inertia. Point A3 is the location of the blade sub-component's structural failure, where the load drops sharply. The failure load is 2871.31 kN, and the failure displacement is 92.05 mm. This response mode is similar to the results of previous trailing edge compression tests. Previous studies have shown that loading after point A3 is accompanied by composite material damage. Since this invention explores the influence of torsional load on structural failure behavior dominated by adhesive failure, and the established failure model does not consider the composite material damage mechanism, the calculation was terminated to avoid interfering with the analysis results and to achieve the intended research objectives.

[0063] like Figure 7As shown, the displacement of the trailing edge along the Y direction at different loading stages was extracted, with the extraction locations referencing the four stages of the force-displacement curve. For ease of description, the displacement of the trailing edge in the Y direction is defined as a buckling wave. It can be observed that the trailing edge buckling waveform exhibits periodic characteristics as the load increases. In the linear stage, the peak-to-peak value of the trailing edge buckling wave increases rapidly with increasing load, reaching its maximum value (85 mm) at point A1. In the A1-A2 stage, the peak-to-peak value of the buckling wave remains relatively stable. When the load decreases sharply, the waveform of the trailing edge buckling wave becomes distorted, with the distortion location between the maximum peak and the minimum trough. Therefore, when loaded in the oscillating direction, the trailing edge exhibits a periodic buckling wave. The peak-to-peak value of the buckling wave increases the fastest in the linear stage, remains stable after buckling, and becomes distorted after structural failure.

[0064] like Figure 8 As shown, failure contour maps of the bonded structure at different loading stages were plotted, and the location reference force-displacement curves for four stages were extracted. Point A4 represents the location of the failure load at 1.1 times the structure. Blue indicates the bonded structure, and red indicates bond failure. It can be seen that bond failure begins on the inner side of the trailing edge of the structure (…). Figure 8 (a)), the bond failure extends along the width direction as the load increases. At point A1, when the structure buckles, the bond failure does not completely penetrate the width direction; that is, the bond failure is difficult to observe externally during structural buckling. The load increases to point A2 ( Figure 8 (c) The adhesive failure completely penetrated the width direction, causing a sharp drop in the force-displacement curve amplitude at point RP-1, leading to trailing edge structural failure. After structural failure, continued loading caused the adhesive failure to propagate along the blade spanwise. Throughout the process, no adhesive failure occurred at the two webs. Therefore, under yaw loading, adhesive failure first occurred at the trailing edge, propagating along the width direction inside the structure until buckling, ultimately penetrating the width direction and causing trailing edge structural failure.

[0065] like Figure 9 As shown, when structural failure occurs, the suction and pressure sides of the trailing edge reinforced region come into contact due to deformation of the trailing edge region. It can be seen that the contact occurs at the two troughs of the trailing edge buckling wave, and the contact stress near the adhesive failure site is greater (1.82 MPa). However, overall, the contact stress is at a relatively low level.

[0066] (2) Pure Torsional Loading: Before analyzing the structural response of the blade sub-component under combined bending and torsional loading, it is necessary to determine the blade's mechanical behavior under pure torsional load. In the model of this invention, the torsional loading point is located at the aerodynamic center RP-2 of the sub-component, with a maximum load of 5 degrees, restricting all degrees of freedom of RP-2 except for torsion in the Z-axis direction. The torque-rotation curve of RP-2 under torsional loading is extracted, as shown below. Figure 10As shown in the figure. The results show that when the torsional load increases to 2.49, 3.27, and 3.77 degrees, the slope of the curve decreases three times, with normalized slopes of 1.14, 0.94, and 0.75, respectively. Finally, when the load reaches 4.82 degrees, the load drops sharply, indicating structural failure, with a failure load of 7343.36 kN·m.

[0067] like Figure 11 As shown in the model of the present invention, in order to facilitate the description of the bonding structure position at the web, the two webs are respectively referred to as the front edge side web and the rear edge side web. The bonding area between the front edge side web and the beam cap is marked as L-J1 and L-J2, and the bonding area between the rear edge side web and the beam cap is marked as T-J1 and T-J2.

[0068] like Figure 12 Failure contour plots of bonded structures at different loading stages under torsional load were plotted, and the moment-rotation curves at reference point RP-2 were extracted. The results show that when the torsional load reaches point TA1, the bonding failures at loading ends T-J1 and T-J2 occur first. Figure 12 (a) causes a decrease in the slope of the torque-rotation curve and structural instability. As the load increases, the adhesive failure slowly propagates along the spanwise direction. Figure 12 (b) and (c) repeatedly caused the slope of the curve to decrease. After point TA3, the rate of adhesive failure propagation accelerated, and at point TA4, the load dropped sharply, leading to structural failure. Figure 12 (d) is the failure contour diagram at the instant of load drop. It can be seen that near the boundary condition, the bonded structure of the trailing edge web plate fails, and the propagation rate accelerates after the load drop. Figure 12 (e) Throughout the torsion process, the leading-edge web and trailing-edge bonded structure did not fail. The maximum damage factor at the trailing edge was 0.46, located at the loading end; the maximum damage factors for the leading-edge webs L-J1 and L-J2 were 0.30 and 0.44, respectively. Torsional load had a more significant impact on the failure of the trailing-edge web bonded structure. For the three-web wind turbine blade, the trailing-edge auxiliary web bonded structure alleviated the pressure of the torsional load on the trailing-edge main web.

[0069] (3) Combined Bending and Torsional Loading: As mentioned above, the structural response characteristics of the blade sub-component in the pure torsional direction were analyzed. The results show that the structure enters the critical failure state when the torsional load reaches 4.82 degrees. Based on the conservative design principle, the torsional parameters were limited to within the critical value (all less than the critical value of 4.82 degrees) under the combined bending and torsional load condition. To this end, four sets of comparative conditions were constructed: gradient torsional loads of 1, 2, 3 and 4 degrees, and the displacement load in the yaw direction was kept to be 100 mm. By comparing the mechanical response with that of the 0-degree torsional angle (i.e., the pure yaw condition), it is easy to separate the effect introduced by the torsional load alone and quantify its influence on trailing edge buckling and adhesion failure migration behavior.

[0070] Plot the force-displacement curves at point RP-1 under different torsion angles. Stop the calculation when the curve first shows a sudden drop in load. The results are as follows: Figure 13 As shown in the figure. The results show that the trailing edge stiffness of the blade sub-component under combined bending and torsion loading is slightly increased compared to that under tumbling loading, with an increase of 7.15%-14.68%, which may be due to the change in the moment of inertia of the cross section caused by the torsion effect. Under combined bending and torsion loading, the structural failure load and failure displacement recorded at point RP-1 are not significantly different from those under pure tumbling loading. The structural failure loads are 2790.67kN, 2789.64kN, 2714.59kN, and 2745.06kN (1-4 degrees), which are 2.60%-5.46% lower than those under pure tumbling loading (2871.31kN); the failure displacements are 87.04mm, 81.50mm, 78.54mm, and 75.48mm (1-4 degrees), which are 8.47%-14.78% lower than those under pure tumbling loading (92.05mm).

[0071] Figure 14 This is the trailing-edge buckling waveform under combined bending and torsion loading to the critical failure state. The waveform exhibits similar periodicity under different torsional gradients. When the torsion angle increases to 3 degrees, the peak-to-peak value on the fixed-end side of the waveform is first greater than that on the loading-end side, as shown below. Figure 14 The green waveform is shown. The location of the maximum peak-to-peak value of the trailing edge waveform coincides with the initial failure location of the bonded structure. When the torsional load is 0, 1, and 2 degrees, the maximum peak-to-peak region of the buckling wave ranges from 1339.81 mm to 2678.63 mm from the loading end, and the initial failure location of the bonded structure also occurs in this region. As the torsional load increases, the maximum peak-to-peak region shifts to 3214.75 mm to 4553.52 mm from the loading end, and the initial failure location of the bonded structure also shifts accordingly. This indicates that, compared to pure tumbling loading, introducing torsional load causes a shift in the trailing edge buckling waveform, leading to a change in the initial debonding location at the trailing edge.

[0072] Compare the starting positions of trailing edge bonded structures under different torsional gradients, such as Figure 15 As shown, adhesive failure originates on the inner side of the blade structure and propagates along the width direction as the load increases. However, with increasing torsional angle, the initiation location of adhesive failure shifts from the side closer to the loaded end to the side closer to the fixed end. This indicates that torsional load reconstructs the blade deformation morphology, inducing a migration of the adhesive failure initiation location.

[0073] Figure 16The trailing edge contact behavior under different torsional gradients under combined bending and torsion loading was extracted. It can be seen that under different torsional gradients, two contact points appeared in the trailing edge reinforced region, located near the two troughs of the buckling waveform. Furthermore, the contact stress and contact area near the fixed end were positively correlated with the torsion angle, while the contact stress and contact area near the loaded end were negatively correlated with the torsion angle. Combined with previous analysis results, this shows that the initiation location of adhesive failure is related to the contact changes in the trailing edge reinforced region; when the initiation location of adhesive failure shifts to the fixed end side, the contact stress and contact area near that location also increase accordingly.

[0074] To further analyze the vulnerable areas of blade components under three load conditions—shimmy, torsion, and bending-torsion—it is necessary to analyze their stress distribution patterns under different load conditions. For example... Figure 17 Three paths were selected on the model to extract data. These paths passed through the leading edge, leading edge plate, beam cap, trailing edge plate, trailing edge reinforcement zone, and trailing edge on both the pressure and suction sides of the blade. The distances of the three paths from the fixed end were 1250mm (path 1), 2500mm (path 2), and 3750mm (path 3), respectively. The Mises stress extraction rule was: when the damage factor of the bonded structure at a certain point in the model first reached a value of 1 in the simulation diagram under the corresponding loading condition, the stress for that analysis step was extracted. The torsional angle under the bending-torsional load condition was 4 degrees. Figure 18 Figure (a) shows a line graph where the horizontal axis represents the actual distance of the blade along the chord length (starting from the leading edge), and the vertical axis represents the Mises stress. Figure 18 (b) Stress distribution box diagrams describe the stress distribution under different loading conditions. These diagrams can reflect the stress distribution trend in the aerodynamic shape region of the blade sub-component.

[0075] Figure 19 The stress data for the suction side of path 1 are shown. The results indicate that the stress distribution under tumbling loading is the widest on this path, mainly ranging from 66.89 MPa to 216.11 MPa, while the stress level is highest under combined bending and torsion loading, mainly distributed between 170.26 MPa and 254.94 MPa. Furthermore, the stress in the rear-edge reinforced region reaches its maximum value (483.50 MPa) under combined bending and torsion loading, located at the same position as the pressure side under the same load condition. Compared to the pressure side on this path, the stress level relationship on the suction side under the three loads is more intuitive. Specifically, under combined bending and torsion loading, the stress distribution in the leading edge and leading edge plate regions is similar to that under torsional loading, while the stress distribution in the beam cap, rear edge plate, rear-edge reinforced region, and rear edge is similar to that under tumbling loading. This indicates that the contribution areas of tumbling load and torsional load to the stress distribution under combined bending and torsion loading are significantly different; the contribution of bending load is mainly concentrated in the rear edge region, while the contribution of torsional load is mainly concentrated in the leading edge region.

[0076] Figure 20 Stress data were extracted from the pressure side of path 2. It can be seen that, similarly, the main stress distribution area is widest under tumbling loading, ranging from 67.40 MPa to 222.95 MPa, while the main stress level is highest under combined bending and torsion loading, ranging from 141.47 MPa to 223.26 MPa. The stress distribution patterns under the three load conditions on this path are similar to those on path 1. It is noteworthy that the relative difference between the main stress peak values ​​(223.26 MPa, 222.95 MPa) under combined bending and torsion loading and tumbling loading on this path is only 0.14%, while the relative difference between the maximum values ​​(452.45 MPa, 417.53 MPa) is only 7.72%, and both are located in the rear edge reinforcement region. This indicates that under combined bending and torsion loading, the structure in the rear edge region on this path mainly bears the bending load in the tumbling direction, while the introduction of torsional load has a relatively small impact on this region.

[0077] Figure 21 The stress on the suction side of trajectory line 2 was extracted. It can be seen that the main stress distribution under torsional loading has the widest range for the first time, ranging from 157.15 MPa to 52.15 MPa. The stress distribution in the trailing edge region is still dominated by bending load. It is worth noting that although the stress peaks under tumbling and bending-torsional loads still appear in the trailing edge reinforced area, they are closer to the laminate rather than the trailing edge bonded structure.

[0078] Figure 22 This represents the stress distribution on the pressure side of path 3, which is closest to the loading end. From... Figure 22 (b) It can be seen that, compared with other regions, the main stress distribution under the three load conditions is more concentrated in this region. Moreover, the maximum stress under tumbling loading, whether at the trailing edge (426.38 MPa) or in the reinforced trailing edge region (383.48 MPa), is significantly greater than the maximum stress under combined bending and torsional loading (353.03 MPa and 314.43 MPa). This indicates that the trailing edge region of the composite laminate is more susceptible to damage under bending loading on the side closer to the loading end, and the introduction of torsional loading can alleviate this phenomenon to some extent.

[0079] Figure 23 The stress distribution on the suction side of path 3 is shown. It can be seen that under combined bending and torsion loading, the stress distribution pattern in the trailing edge region is similar to that under tumbling loading, while the leading edge region is similar to that under torsional loading. Furthermore, the maximum stress value under tumbling loading is significantly higher than that under combined bending and torsion loading. Specifically, the maximum stress value in the trailing edge region under tumbling loading is 381.56 MPa, which is 14.28% higher than the maximum stress value of 333.87 MPa under combined bending and torsion loading. At the same time, the maximum value of the main stress distribution under tumbling loading (381.56 MPa) is also higher than that under combined bending and torsion loading (360.51 MPa).

[0080] Figure 24 This is a stress contour plot of the web of the blade sub-component under different load conditions when the critical structure fails. The results show that under tumbling loading, both webs exhibit significant stress concentration on one side of the loading end, but the overall stress is at a low level. Under torsional loading, the stress level of the trailing edge web is significantly higher than that of the leading edge web. Under combined bending and torsional loading, both webs show high stress levels, especially the trailing edge web, which exhibits a high stress band running through the width direction.

[0081] Based on the failure analysis method described above in this embodiment, the following analysis results can be obtained:

[0082] ① When loaded in the yaw direction, the trailing edge first experiences a decrease in stiffness due to structural deformation. The failure of the trailing edge bonded structure begins on the inner side, expands along the width as the load increases, and eventually penetrates the width, causing the blade sub-component to fail. The initial debonding zone is between the buckling crests, and the contact behavior of the trailing edge reinforcement zone is also nearby. During loading, the stress on the two webs is low, and the bonded structure is not damaged.

[0083] ② When loaded in the torsional direction, the adhesive structure of the trailing edge web fails first, causing a decrease in the torsional stiffness of the sub-component. The adhesive failure propagates along the spanwise direction, causing the torsional stiffness to decrease multiple times, ultimately leading to structural failure. During loading, the stress on the trailing edge web is higher than that on the leading edge.

[0084] ③ Under combined bending and torsion loading, the trailing edge stiffness increases slightly with the increase of the torsional angle. The change in buckling waveform causes the initial debonding position to shift, but it is still between the peak and peak values. The contact behavior of the trailing edge reinforced zone also changes accordingly. When the structure fails, a high-stress band with a through width appears in the trailing edge web.

[0085] ④ Under different load conditions, the average stress in each region of the blade sub-components is significantly higher under combined bending and torsion loading than under yawing and pure torsion loading. Under combined bending and torsion loading, the stress distribution at the trailing edge is similar to that under pure yawing, while that at the leading edge is similar to that under pure torsion.

[0086] Example 2

[0087] Based on the failure analysis results of Example 1, the structure of the target blade sub-component is optimized. The specific optimization measures are as follows:

[0088] (1) Optimization of the trailing edge reinforcement zone: In response to the problem of high stress concentration in the trailing edge reinforcement zone, an additional reinforcing layer (such as 2mm thick SNL (Triax)) is added to this area. The layup direction is consistent with the original layup to improve the stress resistance of this area.

[0089] (2) Optimization of web bonding structure: In response to the problem of high stress zone on the rear edge web, the chamfer size of the web and beam cap bonding structure was optimized from 5mm to 8mm to increase the bonding contact area. At the same time, structural adhesive with higher shear strength was selected to replace the original AV138 structural adhesive.

[0090] The above description is a preferred embodiment of the present invention, used to explain the technical solution of the present invention, and is not intended to limit the present invention. Those skilled in the art can make conventional modifications, equivalent substitutions and improvements within the spirit and principles of the present invention, all of which are still included within the protection scope of the present invention.

Claims

1. A method for analyzing the failure of wind turbine blade components under bending and torsional loading, characterized in that, Includes the following steps: (1) Establish a three-dimensional solid finite element model of the wind turbine blade component. The three-dimensional solid finite element model is constructed based on the airfoil and material layup data of the target blade. It includes the leading edge, leading edge plate, trailing edge, trailing edge plate, trailing edge reinforcement area, beam cap, web and corresponding bonding structure. The model is given corresponding composite material properties and cohesive force model of bonding structure for different regions. (2) Apply a fixed constraint to one end of the three-dimensional solid finite element model, and apply a swaying displacement load and a torsional load around the aerodynamic center to the other end by means of reference point coupling, respectively or simultaneously, to simulate pure swaying, pure torsion and bending-torsion combined loading conditions. (3) Under the combined bending and torsion loading condition, the displacement load in the oscillation direction is kept constant, and a torsional load lower than the critical failure angle of pure torsion is applied in a gradient manner to perform nonlinear static analysis; (4) By monitoring the force-displacement or moment-rotation curves of the loading reference points RP-1 and RP-2 respectively, the critical structural failure point of the blade sub-component is determined, and the buckling waveform of the trailing edge below the failure point, the failure cloud map of the bonded structure, and the contact behavior data of the trailing edge reinforcement area are extracted; among them, the two reference points RP-1 and RP-2 are used for shimmy and torsional loading respectively. Reference point RP-2 is located at 27.5% of the maximum chord length from the leading edge, which is the aerodynamic center of the airfoil of the blade sub-component. Reference point RP-1 is set at 1.5 times the maximum chord length from the leading edge; (5) Compare and analyze the peak-to-peak distribution of the buckling waveform of the trailing edge under different torsional gradients, the migration law of the starting position of the adhesive failure, and the changes in the contact stress and contact area of ​​the trailing edge reinforcement zone. Establish the correlation between the failure of the trailing edge adhesive structure and the buckling waveform and contact behavior under the combined bending and torsional loading condition, so as to predict the failure mode of the blade sub-component under the combined bending and torsional loading condition.

2. The method for analyzing the failure of a wind turbine blade component under bending and torsional loading according to claim 1, characterized in that: In step (1), the cohesive model selected for the bonded structure is a bilinear constitutive model, and the second stress criterion is used to determine the initiation of stiffness degradation.

3. The method for analyzing the failure of a wind turbine blade component structure under bending and torsional loading according to claim 1, characterized in that: In step (3), the critical failure angle of pure torsional loading is determined in the following way: during the simulation of pure torsional loading, a torsional load around the aerodynamic center is applied to the three-dimensional solid finite element model until the structure fails, and the torsional angle corresponding to the load drop point is obtained.

4. The method for analyzing the failure of a wind turbine blade component under bending and torsional loading according to claim 1, characterized in that, In step (4), by extracting the Mises stress distribution along different positions along the span and along the chord path of the blade sub-component, the stress distribution in the leading edge region under combined bending and torsion loading is similar to that under pure torsion loading, and the stress distribution in the trailing edge region is similar to that under pure oscillation.

5. A method for optimizing the structure of wind turbine blade components, characterized in that, The failure analysis is based on the failure analysis results of the wind turbine blade sub-component structure bending and torsional loading failure analysis method according to any one of claims 1-4, specifically including: (1) Based on the analysis results of high stress concentration in the rear edge reinforcement zone under combined bending and torsion loading, strengthen the layup design of the composite laminate in this area or add reinforcing materials. (2) Based on the analysis results of the high stress band that appears in the width direction of the rear edge web under the combined bending and torsion loading condition, optimize the geometric parameters of the web and beam cap bonding structure or select a higher performance structural adhesive.

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