A fatigue performance evaluation method for wind turbine sliding bearings

Abstract

This invention relates to the field of fatigue performance testing technology for wind turbine bearings, and discloses a method for evaluating the fatigue performance of wind turbine sliding bearings, comprising the following steps: S1, establishing a sliding bearing model based on finite element method, and analyzing the residual stress of the interference fit between the bushing and the pin in the sliding bearing, as well as the stress state of the sliding bearing under oil film pressure during service; S2, calculating the circumferential stress distribution of the bushing and solving for the structural stress amplitude before and after oil film loading by subtraction; S3, designing a three-point bending test, and using finite element simulation to calculate the structural stress value of the bushing section corresponding to the unit load. This invention addresses the service safety of sliding bearings in wind power systems, fully considering the stress concentration phenomenon that may exist at the interface of dissimilar materials under the coupling effect of working load and interference fit residual stress, and the lateral constraint characteristics under the state of multi-source gradient load acting on the interface of dissimilar materials, and reasonably quantifies the fatigue reliability of the sliding bearing coating and surrounding area.

Description

Technical Field

[0001] This invention relates to the field of fatigue performance testing technology for wind turbine bearings, and specifically to a method for evaluating the fatigue performance of wind turbine sliding bearings. Background Technology

[0002] In wind turbines, sliding bearings play a crucial role in power transmission, and their working environment is extremely unique. On the one hand, wind turbines are typically installed in open outdoor areas, exposed to the natural environment for extended periods, and must withstand complex and variable weather conditions, such as strong winds, low temperatures, and sandstorms. On the other hand, during wind turbine operation, sliding bearings not only bear enormous axial and radial loads but also need to cope with frequent load fluctuations caused by unstable wind speeds. These factors make the working conditions of sliding bearings in wind turbines far more severe than those of general mechanical equipment.

[0003] In terms of service life, wind turbines are typically designed for 20 to 25 years. This means that during such a long period, sliding bearings need to operate continuously and stably, minimizing maintenance and replacement frequency to reduce power generation and repair costs. Therefore, the material properties, structural design, and manufacturing processes of sliding bearings must meet extremely high requirements to ensure their long-term reliability under complex operating conditions.

[0004] In practical applications, sliding bearings face numerous technical challenges, with fatigue performance being a particularly prominent issue. Specifically, during operation, sliding bearings are subjected to cyclic oil film pressure, making the bushings prone to fatigue failure phenomena such as surface cracking and interface peeling. This fatigue failure not only reduces the load-bearing capacity of the sliding bearing but can also lead to the failure and shutdown of the entire wind turbine unit, resulting in significant economic losses.

[0005] However, there is currently no specific evaluation scheme for testing the fatigue performance of wind turbine sliding bearings. If traditional fatigue testing methods are used, such as taking small specimens from different micro-regions of the bushing and conducting axial tension-tension or tension-compression fatigue tests, the following serious problems will exist:

[0006] 1. Inability to accurately assess interface fatigue performance: The interface formed by the interference fit between the bushing and the pin of the sliding bearing is subjected to complex forces in actual operation, involving multiple superimposed load states; traditional axial tension-tension or tension-compression tests only simulate a single load and cannot reproduce the stress concentration phenomenon of the interface under multi-source gradient loads, resulting in inaccurate interface fatigue performance data.

[0007] 2. Neglecting the lateral constraint effect caused by dissimilar materials: In actual sliding bearing structures, the properties of the cladding and the substrate differ significantly, leading to stress distribution being affected by material dimensions. In other words, the size effect caused by lateral constraints has a significant impact on fatigue test results. Traditional small-sample testing methods do not consider the lateral constraints caused by material differences, resulting in significant deviations between test results and actual conditions, failing to provide a reliable basis for design.

[0008] To address the aforementioned issues, there is an urgent need to develop a new fatigue performance evaluation method for wind turbine sliding bearings, a special component, capable of accurately assessing the fatigue performance of wind turbine sliding bearing materials under complex operating conditions, particularly the fatigue performance of the bushing cladding. This invention, by combining finite element simulation and three-point bending fatigue testing, aims to fill the gaps in traditional methods, providing a scientific basis for the design, material selection, and life prediction of wind turbine sliding bearings, thereby ensuring the safe and stable operation of wind turbine units, reducing maintenance costs, and improving service stability. Summary of the Invention

[0009] The present invention aims to provide a fatigue performance evaluation method for wind turbine sliding bearings, in order to solve the technical problem that traditional fatigue testing methods are difficult to accurately evaluate the fatigue performance of the interface between the bushing matrix and the coating in wind turbine sliding bearings.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for evaluating the fatigue performance of a wind turbine sliding bearing includes the following steps:

[0012] S1. Establish a sliding bearing model based on finite element method, and analyze the residual stress of the interference fit between the bushing and the pin in the sliding bearing, as well as the stress state of the sliding bearing under oil film pressure in the service environment.

[0013] S2. Calculate the stress distribution of the bushing circumferential structure and solve for the stress amplitude of the structure before and after oil film loading by subtraction.

[0014] S3. Design a three-point bending test and use finite element simulation to calculate the structural stress value of the bushing section corresponding to the unit load;

[0015] S4. Based on the stress calculation results of the sliding bearing service process and the simulation calculation results of the three-point bending test, the loading conditions of the three-point bending fatigue test are determined with the structural stress value as the pivot, and the three-point bending fatigue test is carried out.

[0016] Inventive concept:

[0017] Based on the requirements of practical application environments, the inventors conducted in-depth research and analysis on the special component of wind turbine sliding bearings, and discovered several unique problems in evaluating their fatigue performance. The first is the impact of the sliding bearing manufacturing process, such as... Figure 1 As shown, the sliding bearing includes a bushing and a pin 2. The bushing includes a base 1 and a cladding 11. Its manufacturing process involves three stages: flat plate cladding, longitudinal seam welding (weld 12), and interference fit.

[0018] The load and heat applied during the interference fit stage will significantly release the residual stress of the first two processes. As the final step in the manufacturing process, the residual stress generated by the interference fit will be directly retained in the actual product, thus posing a significant hidden danger to the fatigue reliability design of the sliding bearing. However, the existing fatigue assessment methods for wind power sliding bearings directly ignore the influence of the residual stress of the interference fit.

[0019] Secondly, the bushing base 1 and the cladding 11 of the sliding bearing are made of different materials, so the joint between them is relatively weak, and long-term service may lead to problems such as interface cracking and spalling. Furthermore, under the coupled effect of residual stress from the interference fit, the service reliability of the bushing cladding structure faces even more severe challenges. Therefore, after fully considering the influence of residual stress from the interference fit, this invention studies the service safety of the sliding bearing cladding and the interface position (the weak point in the structural load-bearing structure), verifying the fatigue reliability of the cladding structure under conditions closer to actual working conditions, thereby providing more accurate and reliable support for subsequent fatigue strength design work.

[0020] In fatigue performance evaluation, it is generally assumed that the stress distribution of a single material in an unnotched state is not affected by the component size. However, due to differences in mechanical properties, the dimensions of composite structures must be designed to closely match the actual product to avoid size effects. Figure 2 As shown, traditional dog-bone fatigue specimens undergo transverse shrinkage deformation under axial tensile fatigue loading, thus the transverse dimension has a significant impact on the deformation compatibility between the coating and the substrate. Furthermore, axial tension-tension fatigue testing cannot concentrate the load on the weakest points of the specimen, making it impossible to specifically evaluate the fatigue performance at the target location.

[0021] In comparison, such as Figure 3 As shown, the three-point bending fatigue test can, on the one hand, target the coating and the surrounding area to maximize the stress; on the other hand, the maximum transverse dimension of the specimen can be designed to be the same width as the roller, so as to more reasonably examine the bonding strength between the coating and the substrate in the actual product.

[0022] The specific implementation process of the three-point bending fatigue test is as follows: (1) Calculate the oil film load during the service process of the sliding bearing; (2) Calculate the residual stress of the interference fit; (3) Apply the oil film load on the basis of the residual stress model, calculate the equivalent fatigue driving force of the weld section coating area, and quantify it with structural stress; (4) Calculate the structural stress value of the coating area of ​​the fatigue specimen under three-point bending loading; (5) Back-calculate the fatigue load and carry out ultra-high cycle fatigue test. The stopping condition is when the cycle reaches the preset number or the specimen fails due to fatigue; (6) If the specimen does not fail due to fatigue, observe the surface and cross-section to quantify the degree of fatigue damage; if the specimen fails due to fatigue, observe the fracture surface to conduct failure analysis.

[0023] In summary, this invention designs a fatigue testing scheme for the service safety of sliding bearings in wind power systems. It fully considers the stress concentration phenomenon that may exist at the interface of dissimilar materials under the influence of working load and interference fit residual stress, as well as the lateral constraint characteristics of dissimilar materials under multi-source gradient load, and reasonably quantifies the fatigue reliability of the sliding bearing coating and interface area.

[0024] Furthermore, the specific steps for finite element modeling in S1 are as follows:

[0025] Step 1: Set the interference fit;

[0026] Step-2, Release Boundaries: Release the fully fixed strong constraints on the edge of the shaft, and only set weak constraints that do not produce overall displacement and rotation, and observe the distribution of internal stress caused by the interference fit;

[0027] Step 3: Apply oil film pressure.

[0028] Furthermore, in Step-3, Formula 1 is used to apply the oil film pressure using the finite element method. Formula 1 is as follows:

[0029]

[0030] In the formula, P(x) represents the radial normal stress in MPa, and x represents the distance from the center of the shaft in mm.

[0031] Furthermore, in S2, the stress distribution of the bushing circumferential structure in Step-2 and Step-3 is calculated respectively to obtain the residual stress of the interference fit and the stress state after the residual stress is superimposed on the oil film pressure.

[0032] Furthermore, fatigue performance tests were conducted on the fatigue specimens of the sliding bearing bushing in S4, where the fatigue specimens were plate-shaped.

[0033] Furthermore, the fatigue damage characteristics of the specimen fracture surface, coating area, and interface between the coating and the base layer were observed under a microscopic microscope after fatigue testing. Based on the fatigue test results and the microscopic observation results of fatigue damage, the fatigue performance of the wind turbine sliding bearing was comprehensively evaluated.

[0034] Furthermore, the sliding bearing is a wind power sliding bearing, wherein the outer diameter of the pin is 200-300 mm, the shaft length is 200-300 mm, the bushing wall thickness is 8-11 mm, the cylinder length is 250-300 mm, and the bushing and the pin are centrally interference-fitted.

[0035] Furthermore, the interference fit between the bushing and the pin is 0.05 mm.

[0036] Furthermore, when modeling the sliding bearing using finite element method, the mesh is made of C3D8 solid elements. The finest mesh is distributed on the shaft surface and bushing, with a size of 4~5 mm; the coarsest mesh is distributed at the center of the shaft, with a size of 10 mm, and a gradient transition is made in between. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the manufacturing and processing stages of the sliding bearing of the present invention.

[0038] Figure 2 A schematic diagram of lateral constraint under fatigue loading on a dog bone-like structure.

[0039] Figure 3 This is a schematic diagram of three-point bending loading.

[0040] Figure 4 A schematic diagram showing the setup for the finite element analysis step.

[0041] Figure 5 The diagram shows the circumferential stress distribution of the bearing, where (a) is the circumferential stress distribution of the overall interference fit; (b) is the circumferential stress distribution of the bushing interference fit; (c) is the circumferential stress distribution of the overall interference fit plus oil film; and (d) is the circumferential stress distribution of the bushing interference fit plus oil film.

[0042] Figure 6 The diagram shows the stress distribution of the bushing interference fit and oil film; (a) the distribution of circumferential film stress and bending stress of the bushing interference fit; (b) the distribution of structural stress of the inner and outer walls of the bushing interference fit (in the diagram, Top-SS represents the structural stress of the outer wall and Bottom-SS represents the structural stress of the inner wall); (c) the distribution of circumferential film stress and bending stress of the bushing interference fit and oil film; and (d) the distribution of structural stress of the inner and outer walls of the bushing interference fit and oil film.

[0043] Figure 7 The range of structural stress before and after applying oil film pressure.

[0044] Figure 8 This is a photograph of a three-point fatigue test specimen.

[0045] Figure 9 This is a three-point bending finite element model.

[0046] Figure 10 Configure the finite element mesh.

[0047] Figure 11 Finite element simulation of three-point bending load (load 1 kN, deformation magnification 1000 times); where (a) Mises stress distribution when the cladding is under tension; (b) normal stress distribution in the x direction when the cladding is under tension.

[0048] Figure 12 This is the area for observing microscopic fatigue damage.

[0049] Figure 13 for Figure 12 Fatigue damage in region ①.

[0050] Figure 14 for Figure 12 Fatigue damage in region ②.

[0051] Figure 15 This is a schematic diagram of the fatigue performance evaluation steps of the present invention. Detailed Implementation

[0052] The following detailed description illustrates the specific implementation method:

[0053] The reference numerals in the accompanying drawings include: substrate 1, cladding 11, weld 12, and pin 2.

[0054] like Figure 15 As shown, a fatigue performance evaluation method for wind turbine sliding bearings includes the following steps:

[0055] S1. Establish a sliding bearing model based on finite element method, and analyze the residual stress of the interference fit between the bushing and the pin in the sliding bearing, as well as the stress state of the sliding bearing under oil film pressure in the service environment.

[0056] This embodiment specifically uses the commercial finite element software Abaqus CAE2021 to perform finite element analysis on the stress state of an interference fit rolled aluminum-tin alloy bushing under oil film pressure during service. Specifically, the model pin is made of 42CrMo steel, and the bushing is made of SAE1010 steel; the model dimensions are the actual product dimensions. In the wind power field, the typical range of sliding bearing dimensions is: pin outer diameter 200-300 mm, shaft length 200-300 mm, with internal cylindrical perforations of 50-100 mm diameter; bushing wall thickness 8-11 mm, cylinder length 250-300 mm, with a centered interference fit to the pin, and an interference amount of 0.05 mm. Considering that no significant plastic deformation occurs during assembly and service, the material parameters are set as Young's modulus E = 212000 MPa and Poisson's ratio μ = 0.3.

[0057] During modeling, C3D8 (8-node hexahedral) solid elements were used for the mesh, employing a gradient transition meshing strategy to significantly reduce computational cost while maintaining computational accuracy. The finest mesh, measuring 4-5 mm, was located on the shaft surface and bushing; the coarsest mesh, measuring 10 mm, was located at the shaft center, with a gradient transition in between. Due to the interference fit involved, the meshes of the shaft and bushing were aligned as much as possible.

[0058] Specifically, the specific steps of finite element modeling in this embodiment are as follows:

[0059] Step 1: Set the interference fit: Set the contact surface and apply the interference constraint according to the actual product specifications. The interference amount is 0.05 mm. At this time, the boundary condition is a fully fixed constraint on one side edge of the pin shaft, that is, a full displacement constraint is applied to the side node of one end of the pin shaft in the x, y, and z directions. It should be noted that the calculation results obtained in this analysis step are affected by the strong constraint on the edge of the shaft and are not representative.

[0060] Step-2, Release Boundaries: Release the fully fixed strong constraints on the edge of the shaft, and only apply weak constraints to prevent the shaft pin as a whole from generating rigid x, y, z displacements or rotations;

[0061] Step 3: Apply oil film pressure.

[0062] It is worth noting that the calculation process is divided into 3 steps, such as... Figure 4 As shown, initially, the pin edge is set to be fully fixed to avoid non-convergence caused by large deformation in the subsequent interference contact analysis; in Step-1, interference fit contact is set. It is worth noting that the calculation results obtained in this analysis step are affected by the strong constraint on the shaft edge and are not representative; in Step-2, the fully fixed strong constraint on the shaft edge is released, and only the weak constraint that does not produce overall displacement and rotation is set to observe the internal stress distribution generated by the interference fit; in Step-3, oil film pressure is applied.

[0063] Specifically, regarding the loading of oil film pressure, based on the inventor's previous experimental research, finite element loading is performed using Formula 1, as follows:

[0064]

[0065] In the formula, P(x) represents the radial normal stress in MPa, and x represents the distance from the center of the shaft in mm.

[0066] Since this study primarily focuses on the cladding and its interface with the substrate, and considering the tensile effect of the interference fit on the bushing cladding, the assessment of the circumferential stress on the bushing is particularly important. Specifically, such as... Figure 5 As shown in Figure (a), the interference fit causes the bushing to bear significant circumferential tensile stress, which is relatively evenly distributed. The maximum load is located on the inner wall of the bushing edge, reaching 71.96 MPa, while the minimum load is located on the outer wall of the bushing, also reaching 66.4 MPa (see Figure (b)). When oil film pressure is applied, the circumferential stress state of the bushing changes significantly, as shown in Figure (b). Figure 5 As shown in (c) and (d): ① The difference between the inner and outer walls is significantly reduced; ② The tensile stress at the edge of the bushing remains basically unchanged, while the circumferential stress at the center position decreases significantly, down to 10.32 MPa.

[0067] S2. Calculate the stress distribution of the bushing circumferential structure in Step-2 and Step-3 respectively, and calculate the difference to solve the stress amplitude of the structure before and after oil film loading.

[0068] The stress distribution of the bushing under interference fit and subsequent loading is as follows: Figure 6 As shown, the horizontal axis represents the distance from the edge of the bushing; when only an interference fit is applied, the membrane stress of the bushing section is dominant and the bending stress is low (see...). Figure 6 (a)), the overall stress of the inner wall structure is greater than that of the cladding (see Figure 6 (b) The maximum structural stress is located at the inner wall edge, at 72.07 MPa. When oil film pressure is applied, the film stress in the central region of the bushing cross-section decreases significantly (see...). Figure 6 (c) The structural stress distribution of the inner and outer walls is not significantly different (see […]). Figure 6 (d) The maximum structural stress is located at the inner wall edge, which is 70.52 MPa, and the minimum structural stress is located at the center of the cladding, which is 10.624 MPa.

[0069] Subtracting the structural stress values ​​obtained in Step-2 from those obtained in Step-3 yields the circumferential structural stress range (maximum stress minus minimum stress) experienced by the bushing section during cyclic loading. Figure 7As shown, the maximum structural stress range borne by the inner and outer walls is basically the same, at 55.63 MPa. Considering the average stress, the most dangerous location of the bushing is the middle region of the inner wall, with a maximum cyclic load of 71 MPa, a minimum load of 15.37 MPa, and a stress ratio of 0.22. Although the rolled cladding material of the bushing is located on the outer wall, in order to retain a certain load-bearing margin, the fatigue test in this embodiment is set to a tension-tension cyclic loading with a maximum of 75 MPa and a minimum of 16.5 MPa.

[0070] The structural stress method used in this embodiment has one advantage over conventional evaluation methods such as the notch stress method and the hot spot stress method: it is mesh insensitive, eliminating calculation errors caused by mesh size. This makes the structural stress method significantly advantageous for analyzing large and complex structures. Because structural stress consists of membrane stress and bending stress calculated using nodal forces, finite element software (most finite element software) with displacement as a fundamental unknown can only guarantee the balance of nodal forces and nodal moments at the node locations, but not the balance of stresses.

[0071] For a two-dimensional problem, in order to calculate the structural stress at the potential failure section, the nodal forces F(1)1, F(2)1, F(1)2, ..., F(2)i on the critical section are first extracted. Since F(1)1, F(2)1, F(1)2, ..., F(2)i are in equilibrium with the external forces, the membrane stress and bending stress calculated therefrom are also in equilibrium with the external forces and can be solved by the equilibrium formula (2).

[0072] It is known from the equilibrium relationship that: (2)

[0073] Summarized as follows: (3)

[0074] In the above formula, Fx is the resultant force of external forces, My is the resultant moment of external forces, Fxi is the nodal force; t is the plate thickness, yi is the nodal coordinate, and σm and σb are the membrane stress and bending stress, respectively.

[0075] Specifically, in the actual three-dimensional structural stress process, this calculation process can be quickly solved using the Verity module in the DS SIMULIA fe-safe software.

[0076] S3. Design a three-point bending test and use finite element simulation to calculate the structural stress value of the bushing section corresponding to the unit load.

[0077] To fully investigate the fatigue performance of the coating and its bonding strength with the substrate, this invention employs a three-point bending loading scheme in the fatigue test. Specifically, in this embodiment, the fatigue specimen is plate-shaped, such as... Figure 8As shown, the dimensions are designed to be 100*30*10 mm; the actual thickness is 10.41 mm, of which the cladding thickness is 1.39 mm; the surface material is aluminum-tin alloy, and the base is SAE1010 steel; the support end span is 40 mm.

[0078] Based on the specimen dimensions, a finite element analysis of three-point bending loading was conducted to determine the experimental load. Specifically, the model is as follows: Figure 9 As shown, the top of the specimen is made of SAE1010 steel, the narrow strip at the bottom is coated with aluminum-tin alloy, the support span is 40mm, and the load is located at the center of the specimen. The mesh is as follows. Figure 10 As shown, local mesh refinement was performed at high-stress locations.

[0079] Figure 11 The stress distribution cloud map is shown under a 1 kN load and magnified 1000 times. The results show that when three-point bending loads the substrate and puts the cladding under tension, a clear stress stratification characteristic appears at the interface between the cladding and the substrate. The high-stress area is located on the substrate side of the interface. This is mainly because when the component is subjected to a three-point bending load, the overall displacement continuity is still satisfied; that is, under the same strain, the substrate side with greater stiffness bears a greater load. The difference in material stiffness leads to stress stratification at the interface. Furthermore, the stress corresponding to the cladding structure under a 1 kN load is 8.24 MPa. To achieve a maximum tension-tension cyclic loading of 75 MPa and a minimum of 16.5 MPa, the three-point bending load is set to a maximum of 9.1 kN and a minimum of 2 kN.

[0080] S4. Based on the stress calculation results of the sliding bearing service process and the simulation calculation results of the three-point bending test, the loading conditions of the three-point bending fatigue test are determined with the structural stress value as the pivot.

[0081] Specifically, the method for determining the three-point bending loading conditions is: target position service stress result * safety factor / stress corresponding to the unit load of the three-point bending. In this embodiment, based on the oil film pressure borne by the sliding bearing during service and the residual stress of the interference fit during the assembly process of the bearing assembly, combined with the correlation obtained from the above finite element analysis, fatigue performance test loading conditions are designed, and fatigue performance tests are carried out using four three-point bending specimens to verify the fatigue reliability and service safety of the rolled cladding during its 20-year service life. Among them, the number of cyclic loadings reaches 8.0 × 10⁻⁶. 7 .

[0082] S5. Conduct fatigue performance tests on the fatigue test specimens of sliding bearing bushings.

[0083] The fatigue test was conducted using the QBG-20 high-frequency fatigue testing system. Cyclic loading was performed using a sinusoidal wave with a maximum load of 9.1 kN, a minimum load of 2 kN, and a stress ratio of 0.22. The support span was 40 mm, and the loading was located at the center of the specimen. The test environment was room temperature of 22℃ and humidity of 30%. The frequency was controlled at around 140 Hz. The test was stopped after specimen failure or after 8.0 × 10⁷ cycles.

[0084] S6. Microscopic observation of the fatigue damage characteristics of the fracture surface, bushing surface, and interference fit interface between bushing and pin after fatigue testing.

[0085] The surface fatigue damage of the specimen was observed using an optical microscope or a scanning electron microscope. The observation area was as follows: Figure 12 As shown, ① represents the surface coating and interface area of ​​the specimen; ② represents the coating and interface area of ​​the cross section of the specimen, both of which are located at the position of maximum tensile stress.

[0086] S7. Based on the fatigue test results and the results of fatigue damage microscopic observation, the fatigue performance of the wind turbine sliding bearing is comprehensively evaluated.

[0087] Specifically, microscopic observation revealed that fatigue crack initiation in the coating is the main mode of fatigue damage in sliding bearing structures under fatigue loading.

[0088] like Figure 13 As shown, (a) is a micrograph of the coating and interface area on the surface of the specimen after the fatigue test; (b) is an enlarged view of the area within the yellow dashed box in (a); in (a), ① indicates the coating and ② indicates the matrix; the arrow in (b) indicates the crack. According to 13, the bushing structure of the sliding bearing may develop longitudinal cracks under three-point bending fatigue loading; the actual crack is affected by multiple factors such as interface resistance and microstructure anisotropy, and presents an expansion path that is not completely perpendicular to the loading direction.

[0089] like Figure 14 As shown, (a) is a cross-sectional micrograph of the specimen after fatigue test without considering the residual stress of the interference fit; (b) is a cross-sectional micrograph of the specimen after fatigue test with consideration of the residual stress of the interference fit; (c) is a micrograph of the interface where fatigue failure occurs; (d) is an enlarged view of the interface region in (c); (e) is a macroscopic photograph of the location in (c); where ① in Figure (a) indicates the cladding layer and ② indicates the substrate.

[0090] Figure (a) shows that, without considering the residual stress of the interference fit, no obvious fatigue damage was observed in the three-point bending fatigue specimen after loading; Figure (b) shows that, considering the residual stress of the interference fit and thus increasing the fatigue load, slight cracking traces are visible at the interface between the specimen coating and the substrate; Figure (c) shows the case where severe fatigue cracking occurs at the interface between the specimen coating and the substrate after considering the residual stress of the interference fit; Figure (d) shows that interface delamination caused by fatigue cracks does not necessarily occur entirely at the interface location, and the vicinity of the interface is also a weak area; Figure (e) shows the location of the interface delamination area in the macroscopic photograph of the specimen.

[0091] In summary, when the three-point bending fatigue specimen undergoes 8.0 × 10⁻⁶ cycles... 7 After several cycles of loading, if no significant deformation, coating peeling, or coating cracking occurs, the sliding bearing structure is considered to have good fatigue reliability and can meet service requirements. Conversely, if no problems occur, the structure is considered to have poor fatigue reliability and does not meet service requirements. In other words, the fatigue performance evaluation method of this invention can more accurately and realistically evaluate whether the bonding between the sliding bearing matrix and the coating has reliable fatigue performance, thus providing reliable support for the fatigue strength design of wind turbine sliding bearings.

[0092] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for evaluating the fatigue performance of a wind turbine plain bearing, characterized in that Comprise the following steps: S1, based on finite element to establish sliding bearing model, and analyze the residual stress of the interference fit between the shaft sleeve and the pin shaft in the sliding bearing, and the stress state of the sliding bearing under the service environment of oil film pressure; The specific steps of finite element modeling are: Step-1, set the interference fit; Step-2, release the boundary: release the full fixed strong constraint of the edge of the shaft body, only set the weak constraint which does not produce overall displacement and rotation, and observe the internal stress distribution generated by the interference fit; Step-3, apply oil film pressure; Formula one is used to load oil film pressure in finite element, and formula one is as follows: ； In the formula, P(x) represents the radial normal stress, unit MPa, and x represents the distance from the center position of the shaft, unit mm; S2, calculate the circumferential stress distribution of the shaft sleeve, and make difference to solve the structure stress amplitude before and after oil film loading; S3, design three-point bending test, and calculate the structure stress value of the shaft sleeve section corresponding to unit load by using finite element simulation; S4, based on the stress calculation results of the service process of the sliding bearing and the simulation calculation results of the three-point bending test, taking the structure stress value as the pivot, the loading conditions of the three-point bending fatigue test are determined, and the three-point bending fatigue test is carried out.

2. The method for evaluating the fatigue performance of a wind power sliding bearing according to claim 1, characterized in that, In S2, the circumferential stress distribution of the shaft sleeve of Step-2 and Step-3 is calculated respectively, so as to obtain the residual stress of the interference fit and the stress state after the residual stress is superimposed with the oil film pressure.

3. The method for evaluating the fatigue performance of a wind power sliding bearing according to claim 2, characterized in that, In S4, the fatigue performance test of the sliding bearing shaft sleeve fatigue test piece is carried out, wherein the fatigue test piece is a plate.

4. The method for evaluating the fatigue performance of a wind power sliding bearing according to claim 3, characterized in that, The fatigue damage characteristics of the fracture, coating area and the combination interface of the coating and the base layer of the test piece after fatigue test are observed by microscope, and based on the fatigue test results and the fatigue damage microscopic observation results, the fatigue performance of the wind power sliding bearing is comprehensively evaluated.

5. The method for evaluating the fatigue performance of a wind power sliding bearing according to claim 1, characterized in that, The sliding bearing is a wind power sliding bearing, wherein the outer diameter of the pin shaft is 200-300 mm, the shaft length is 200-300 mm, the shaft sleeve wall thickness is 8-11 mm, the barrel length is 250-300 mm, and the shaft sleeve and the pin shaft are centrally interference fitted.

6. The method for evaluating the fatigue performance of a wind power sliding bearing according to claim 5, characterized in that, The interference amount of the interference fit between the shaft sleeve and the pin shaft is 0.05 mm.

7. The method for evaluating the fatigue performance of a wind power sliding bearing according to claim 6, characterized in that, When modeling the sliding bearing by using finite element, the grid adopts C3D8 solid element, wherein the grid is most dense at the surface of the shaft body and the shaft sleeve, and the size is 4-5 mm; The grid is most coarse at the center of the shaft body, and the size is 10 mm, and the gradient transition is carried out in the middle.

Images