Fatigue performance evaluation method for wind power sliding bearing

Abstract

The invention relates to the technical field of wind power bearing fatigue performance test, and discloses a wind power sliding bearing fatigue performance evaluation method comprising the following steps: S1, building a sliding bearing model based on a finite element, and analyzing the residual stress of interference fit between a shaft sleeve and a pin shaft in a sliding bearing; the stress state of the sliding bearing under the oil film pressure in the service environment is determined; s2, calculating axial structural stress distribution of the shaft sleeve, and solving structural stress amplitudes before and after oil film loading through difference; and S3, designing a three-point bending test, and calculating a structural stress value of a shaft sleeve section corresponding to a unit load by adopting finite element simulation. Aiming at the service safety of the sliding bearing in the wind power system, the stress concentration phenomenon possibly existing in the dissimilar material interface under the coupling influence of the working load and the interference fit residual stress and the transverse constraint characteristic of the multi-source gradient load acting on the dissimilar material interface state are fully considered; and the fatigue reliability of the sliding bearing coating and the nearby area is reasonably quantified.

Description

Technical Field

[0001] The present invention relates to the technical field of fatigue performance testing of wind power bearings, and in particular to a fatigue performance evaluation method for wind power sliding bearings. Background Art

[0002] In wind turbines, sliding bearings play a crucial role in power transmission, and their operating environment is extremely unique. On the one hand, wind turbines are typically installed in open areas, exposed to the elements for extended periods, and must withstand complex and changing climatic conditions such as strong winds, low temperatures, and dust storms. On the other hand, during operation, sliding bearings must not only withstand enormous axial and radial loads, but also cope with frequent load fluctuations caused by unstable wind speeds. These factors make the operating conditions of sliding bearings in wind turbines even harsher 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 this long period, sliding bearings must operate continuously and stably, minimizing maintenance and replacement to reduce power generation and repair costs. Therefore, the material properties, structural design, and manufacturing processes of sliding bearings must meet extremely high standards to ensure long-term reliability under complex operating conditions.

[0004] In actual use, sliding bearings face numerous technical challenges, particularly fatigue performance. Specifically, sliding bearings are subject to periodic oil film pressure during operation, which can cause fatigue failures such as surface cracking and interface delamination in the sleeve. This fatigue failure not only reduces the bearing's load-bearing capacity but can also cause the entire wind turbine to shut down, resulting in significant economic losses.

[0005] However, there is currently no dedicated evaluation program for fatigue performance testing of wind turbine sliding bearings. If traditional fatigue testing methods are used, such as cutting small specimens from different micro-regions of the sleeve and performing axial tension-tension or tension-compression fatigue tests, the following serious problems will occur: 1. Unable to accurately evaluate the fatigue performance of the interface: The interface formed by the interference fit between the sleeve and the pin of the sliding bearing is subjected to complex forces in actual work, involving the superposition of multiple 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.

[0006] 2. Ignoring the influence of lateral constraints caused by dissimilar materials: In actual sliding bearing structures, the performance of the coating and the substrate differ significantly, resulting in stress distribution being affected by material size. This dimensional effect of lateral constraints has a significant impact on fatigue test results. Traditional small specimen testing methods fail to account for the lateral constraints caused by material differences, resulting in significant deviations between test results and actual conditions, making them ineffective in providing a reliable basis for design.

[0007] To address these challenges, there is an urgent need to develop a new fatigue performance evaluation method for wind turbine sliding bearings, a specialized component. This method can accurately assess the fatigue performance of wind turbine sliding bearing materials under complex operating conditions, particularly the fatigue performance of the sleeve coating. By combining finite element simulation with three-point bending fatigue testing, this method aims to bridge the gaps in traditional methods and provide a scientific basis for the design, material selection, and lifespan prediction of wind turbine sliding bearings, thereby ensuring the safe and stable operation of wind turbines, reducing maintenance costs, and improving service reliability. Summary of the Invention

[0008] The present invention aims to provide a fatigue performance evaluation method for wind turbine sliding bearings to solve the technical problem that traditional fatigue test methods are difficult to accurately evaluate the fatigue performance of the interface between the sleeve substrate and the coating in wind turbine sliding bearings.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions: A method for evaluating the fatigue performance of a wind turbine sliding bearing comprises the following steps: S1. Establish a sliding bearing model based on finite element analysis and analyze the residual stress of the sleeve and pin interference fit in the sliding bearing, as well as the stress state of the sliding bearing when subjected to oil film pressure in the service environment; S2. Calculate the annular structural stress distribution of the sleeve and perform a differential calculation to determine the structural stress amplitude before and after oil film loading. S3. Design a three-point bending test and use finite element simulation to calculate the structural stress value of the sleeve section corresponding to the unit load; 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.

[0010] Invention concept: Based on the needs of the actual application environment, the inventor conducted in-depth research and analysis on the special component of wind power sliding bearings and found that there are several unique problems in the fatigue performance evaluation of them. The first is the impact of the sliding bearing processing and manufacturing process, such as Figure 1As shown, the sliding bearing includes a sleeve and a pin 2, wherein the sleeve includes a base 1 and a cladding 11, and its manufacturing process involves three stages: flat plate cladding, longitudinal seam welding (weld 12) and interference fit.

[0011] Among them, the load and heat applied during the interference fit stage will significantly release the residual stress of the first two processes. The interference fit itself is the last link in the processing and manufacturing process, and the residual stress generated will directly remain in the actual product, thereby posing a major hidden danger to the fatigue reliability design of the sliding bearing; however, the existing fatigue assessment method of wind power sliding bearings directly ignores the influence of the residual stress of the interference fit.

[0012] Secondly, the sleeve base 1 and cladding 11 of the sliding bearing are made of different materials, so the junction between them is inherently weak, potentially leading to interfacial cracking and spalling during long-term service. Coupled with the residual stresses of the interference fit, the service reliability of the sleeve cladding structure faces even more severe challenges. Therefore, after fully considering the impact of the residual stresses of the interference fit, the present invention studies the service safety of the sliding bearing cladding and interface (a weak point in the structural load-bearing structure). This verifies the fatigue resistance of the cladding structure under conditions closer to actual operating conditions, thereby providing more accurate and reliable support for subsequent fatigue strength design.

[0013] When evaluating fatigue performance, it is generally believed that the stress distribution of a single material in an unnotched state will not be affected by the size of the component. However, due to differences in mechanical properties, the size design of a composite structure must be as close to the actual product as possible to avoid size effects. Figure 2 As shown, conventional dogbone fatigue specimens shrink and deform laterally when subjected to axial tensile fatigue loading. Therefore, the lateral dimensions significantly influence the deformation coordination between the cladding and the substrate. Furthermore, axial tension-tension fatigue testing cannot concentrate the load at the specimen's weakest locations, making it impossible to perform targeted fatigue performance assessments at these locations.

[0014] In contrast, Figure 3 As shown, the three-point bending fatigue test can, on the one hand, specifically maximize the stress on the coating and the surrounding area; on the other hand, the maximum lateral dimension of the specimen can be designed to be the same as the width of the roller, thereby more reasonably examining the bonding strength between the coating and the substrate in actual products.

[0015] The specific implementation process of the three-point bending fatigue test is as follows: (1) Calculate the oil film load of the sliding bearing during service; (2) Calculate the residual stress of the interference fit; (3) Apply the oil film load based on the residual stress model, calculate the equivalent fatigue driving force of the weld cross-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) Inversely calculate the fatigue load and carry out ultra-high cycle fatigue test, with the stopping condition being the preset number of cycles or fatigue failure of the specimen; (6) If the specimen does not fail due to fatigue, perform surface and cross-section observations to quantify the degree of fatigue damage; if the specimen fails due to fatigue, perform fracture observations to conduct failure analysis.

[0016] In summary, the present 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 residual stress of interference fit, as well as the lateral constraint characteristics under the state of dissimilar materials under multi-source gradient load, and reasonably quantifies the fatigue reliability of the sliding bearing coating and interface area.

[0017] Furthermore, the specific steps of finite element modeling in S1 are: Step-1, set the interference fit; Step 2: Release the boundary: Release the strong constraint of the axis edge and set only weak constraints that do not produce overall displacement and rotation to observe the internal stress distribution caused by the interference fit. Step-3, apply oil film pressure.

[0018] Furthermore, in Step-3, Formula 1 is used to perform finite element loading of oil film pressure. Formula 1 is as follows:

[0019] Where P(x) represents the radial normal stress in MPa, and x represents the distance from the center of the shaft in mm.

[0020] Furthermore, the annular structural stress distribution of the sleeve in Step-2 and Step-3 is calculated in S2 to obtain the interference fit residual stress and the stress state after the residual stress is superimposed on the oil film pressure.

[0021] Furthermore, in S4, fatigue performance testing is carried out on a sliding bearing sleeve fatigue specimen, wherein the fatigue specimen is in a plate shape.

[0022] Furthermore, the fatigue damage characteristics of the specimen fracture, coating area and the coating-base interface after fatigue testing were observed microscopically. Based on the fatigue test results and fatigue damage microscopic observation results, the fatigue performance of the wind turbine sliding bearing was comprehensively evaluated.

[0023] Furthermore, 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 sleeve wall thickness is 8-11 mm, the tube length is 250-300 mm, and the sleeve and the pin shaft are centrally interference fit.

[0024] Furthermore, the interference fit between the sleeve and the pin is 0.05 mm.

[0025] Furthermore, when using finite element method to model the sliding bearing, the mesh adopts C3D8 solid element. The finest mesh is distributed on the surface of the shaft and the sleeve, 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 performed in the middle. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the manufacturing process stages of the sliding bearing of the present invention.

[0027] Figure 2 Schematic diagram of lateral restraint for dog-bone fatigue loading.

[0028] Figure 3 Schematic diagram of three-point bending loading.

[0029] Figure 4 Schematic diagram for setting up the finite element analysis steps.

[0030] Figure 5 The hoop stress distribution diagram of the bearing, including (a) overall interference hoop stress distribution; (b) sleeve interference hoop stress distribution; (c) overall interference + oil film hoop stress distribution; (d) sleeve interference + oil film hoop stress distribution.

[0031] Figure 6 Schematic diagram of the sleeve interference and oil film stress distribution; among them, (a) the sleeve interference annular film stress and bending stress distribution; (b) the sleeve interference annular inner wall and outer wall structural stress distribution (in the figure, Top-SS represents the outer wall structural stress, and Bottom-SS represents the inner wall structural stress); (c) the sleeve interference + oil film annular film stress and bending stress distribution; (d) the sleeve interference + oil film annular inner wall and outer wall structural stress distribution.

[0032] Figure 7 is the structural stress range before and after the oil film pressure is applied.

[0033] Figure 8 This is a physical picture of the three-point fatigue specimen.

[0034] Figure 9 It is a three-point bending finite element model.

[0035] Figure 10 Settings for the finite element mesh.

[0036] Figure 11 Finite element simulation of three-point bending loading (load 1 kN, deformation magnification 1000 times); (a) mises stress distribution when the cladding is in tension; (b) normal stress distribution in the x-direction when the cladding is in tension.

[0037] Figure 12 This is the micro fatigue damage observation area.

[0038] Figure 13 for Figure 12 Fatigue damage in the middle area ①.

[0039] Figure 14 for Figure 12 Fatigue damage in the middle area ②.

[0040] Figure 15 Schematic diagram of the fatigue performance evaluation steps of the present invention. DETAILED DESCRIPTION

[0041] The following is further described in detail through specific implementation methods: The reference numerals in the drawings of the specification include: substrate 1 , coating 11 , weld 12 , and pin 2 .

[0042] like Figure 15 As shown, a fatigue performance evaluation method for a wind turbine sliding bearing includes the following steps: S1. Establish a sliding bearing model based on finite element analysis, and analyze the residual stress of the interference fit between the sleeve and the pin in the sliding bearing, as well as the stress state of the sliding bearing when it is subjected to oil film pressure in the service environment.

[0043] This embodiment specifically uses the commercial finite element software Abaqus CAE2021 to perform finite element analysis on the stress state of the interference-fit laminated aluminum-tin alloy sleeve under oil film pressure in the service environment. Specifically, the model pin is made of 42CrMo steel, the sleeve is made of SAE1010 steel, and the model size is the actual product size; in the wind power field, the range of sliding bearing sizes is usually: the pin outer diameter is 200-300 mm, the shaft length is 200-300 mm, and the inner cylindrical hollow is arranged with a hollow diameter of 50-100 mm; the sleeve wall thickness is 8-11 mm, the tube length is 250-300 mm, and it is centered with the pin with an interference fit of 0.05 mm. Among them, considering that no obvious plastic deformation occurs during the assembly and service process, the material parameters are set to Young's modulus E=212000 MPa and Poisson's ratio μ=0.3.

[0044] The modeling process uses C3D8 (8-node hexahedron) solid elements with a gradient transition partitioning strategy to ensure accuracy while significantly reducing computational effort. The finest mesh is located on the shaft surface and sleeve, measuring 4-5 mm; the coarsest is located at the center of the shaft, measuring 10 mm, with a gradient transition in between. Due to interference fit, the meshes of the shaft and sleeve are aligned as closely as possible.

[0045] Specifically, the specific steps of finite element modeling in this embodiment are: Step 1. Set the interference fit: Set the contact surface and apply an interference constraint based on the actual product specifications, with an interference of 0.05 mm. At this time, the boundary condition is a full fixed constraint on the edge of one side of the pin, that is, a full displacement constraint is applied to the side node of one end of the pin 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.

[0046] Step 2: Release the boundary: Release the strong constraint on the axis edge and only apply the weak constraint that prevents the entire axis pin from generating x, y, z rigid displacement or rotation. Step-3, apply oil film pressure.

[0047] It is worth noting that the calculation process is divided into 3 steps, such as Figure 4 As shown in the figure, a fully fixed constraint on the pin edge is initially set to avoid large deformation in the subsequent interference contact analysis and resulting in non-convergence; interference fit contact is set in Step-1. 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; Step-2 releases the fully fixed strong constraint on the shaft edge and only sets a weak constraint that does not produce overall displacement and rotation to observe the internal stress distribution caused by the interference fit; Step-3 applies oil film pressure.

[0048] Specifically, in terms of loading of the oil film pressure, according to the inventor's previous experimental research, finite element loading is performed using Formula 1, which is as follows:

[0049] Where P(x) represents the radial normal stress in MPa, and x represents the distance from the center of the shaft in mm.

[0050] Since this study focuses on the coating and its interface with the substrate, and considering the tensile effect of interference fit on the sleeve coating, the evaluation of the hoop stress on the sleeve is particularly important. Figure 5As shown in Figure (a), the interference fit causes the sleeve to bear significant circumferential tensile stress, and the distribution is relatively uniform. The maximum load is located on the inner wall of the sleeve edge, reaching 71.96 MPa, and the minimum load is located on the outer wall of the sleeve, also 66.4 MPa (see Figure (b)). When the oil film pressure is applied, the circumferential stress state of the sleeve 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 strength of the sleeve edge remains basically unchanged, and the circumferential stress at the center position decreases significantly, as low as 10.32 MPa.

[0051] S2. Calculate the annular structural stress distribution of the sleeve in Step-2 and Step-3 respectively, and make a difference to obtain the structural stress amplitude before and after oil film loading.

[0052] The structural stress distribution of sleeve interference and loading after interference is as follows Figure 6 As shown in the figure, the horizontal axis is the distance from the edge of the sleeve. When only the interference fit is applied, the membrane stress of the sleeve cross section is dominant and the bending stress is low (see Figure 6 (a)), the 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 edge of the inner wall, which is 72.07 MPa. When the oil film pressure is superimposed, the film stress in the center area of ​​the sleeve cross section decreases significantly (see Figure 6 (c)), the structural stress distribution of the inner and outer walls is not much different (see Figure 6 (d)), the maximum structural stress is located at the edge of the inner wall, which is 70.52 MPa, and the minimum structural stress is located at the center of the cladding, which is 10.624 MPa.

[0053] The difference between the structural stress values ​​obtained in Step-2 and Step-3 can be used to obtain the circumferential structural stress range (Structural Stress Range, the maximum stress minus the minimum stress in the cyclic process) borne by the sleeve section during the cyclic loading process, as shown in the figure. Figure 7 As shown, the maximum structural stress range experienced by the inner and outer walls is essentially the same, at 55.63 MPa. Considering the average stress, the most critical location for the sleeve is the middle area of ​​the inner wall, where the maximum cyclic load is 71 MPa, the minimum load is 15.37 MPa, and the stress ratio is 0.22. Although the sleeve's roll-coated cladding material is located on the outer wall, to maintain a certain load margin, the fatigue test in this example was set to a pull-pull cyclic loading of a maximum of 75 MPa and a minimum of 16.5 MPa.

[0054] One advantage of the structural stress method used in this example over conventional assessment methods such as the notch stress method and the hot spot stress method is its mesh insensitivity, eliminating calculation errors caused by mesh size. This significantly enhances the structural stress method's effectiveness in analyzing large, complex structures. Because structural stresses are composed of membrane and bending stresses calculated using nodal forces, finite element software using displacement as a fundamental unknown (as is the case with most finite element software) can only guarantee equilibrium of nodal forces and bending moments at nodes, not stress equilibrium.

[0055] For two-dimensional problems, in order to calculate the structural stress of the potential failure section, the nodal forces F(1) 1, F(2) 1, F(1) 2, …, F(2) i on the dangerous 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 from them are also in equilibrium with the external forces and can be solved using the equilibrium formula (2).

[0056] From the equilibrium relationship we know: (2) Arranged: (3) In the above formula, Fx is the resultant external force, My is the resultant external moment, Fxi is the nodal force; t is the plate thickness, yi is the nodal coordinate, σm and σb are the membrane stress and bending stress, respectively.

[0057] Specifically, in the actual three-dimensional structural stress process, this calculation process can be quickly solved through the Verity module in DS SIMULIA fe-safe software.

[0058] S3. Design a three-point bending test and use finite element simulation to calculate the structural stress value of the sleeve section corresponding to the unit load.

[0059] In order to fully examine the fatigue performance of the coating and its bonding strength with the substrate, the fatigue test adopts a three-point bending loading scheme. Specifically, the fatigue specimen in this embodiment is a plate-shaped specimen. Figure 8 As shown, the design size is 100*30*10 mm; the actual thickness data is 10.41 mm, of which the coating thickness is 1.39 mm; the surface material is aluminum-tin alloy, and the substrate is SAE1010 steel; the support end span is 40 mm.

[0060] Based on the specimen size, a finite element study of three-point bending loading was carried out to determine the test load. Specifically, the model is as follows Figure 9 As shown in the figure, the top of the specimen is set as SAE1010 steel substrate, the narrow strip at the bottom is set as aluminum-tin alloy coating, the support end span is 40mm, and the load is located at the center of the specimen. Figure 10As shown, local mesh refinement is performed at high stress locations.

[0061] Figure 11 The stress distribution cloud diagram under a 1 kN load and a 1000x deformation magnification shows that when three-point bending is applied to the substrate, causing the cladding to be tensile, the interface between the cladding and the base layer exhibits distinct stress distribution stratification, with the high-stress area located on the substrate side of the interface. This is primarily due to the fact that when the component is subjected to three-point bending, the overall displacement continuity requirement is maintained. That is, under the same strain, the stiffer substrate side bears greater load. This material stiffness difference leads to stress stratification at the interface. Furthermore, a 1 kN load corresponds to a stress of 8.24 MPa in the cladding structure. To achieve a maximum tension-tension cyclic loading of 75 MPa and a minimum of 16.5 MPa, the three-point bending load was set to a maximum of 9.1 kN and a minimum of 2 kN.

[0062] S4. Based on the stress calculation results of the sliding bearing during service 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.

[0063] Specifically, the method for determining the three-point bending loading condition is: target position service stress result * safety factor / stress corresponding to the three-point bending unit load; in this embodiment, based on the oil film pressure borne by the sliding bearing during service and the interference fit residual stress during the shaft sleeve assembly process, combined with the correlation obtained by the above finite element analysis, the fatigue performance test loading conditions are designed and four three-point bending specimens are used to carry out fatigue performance tests to verify the fatigue reliability and service safety of the roll-bonded coating during its 20-year service life. The number of cyclic loading cycles reaches 8.0×10 7 .

[0064] S5. Conduct fatigue performance test on sliding bearing sleeve fatigue specimens.

[0065] The fatigue test was conducted using a QBG-20 high-frequency fatigue testing system. Cyclic loading was performed using a sinusoidal load 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 load was located at the center of the specimen. The test environment was room temperature of 22°C and humidity of 30%. The frequency was controlled at approximately 140 Hz. Cyclic loading was stopped after specimen failure or 8.0 × 107 cycles.

[0066] S6. Microscopic observation of fatigue damage characteristics of the fracture surface, sleeve surface, and interference fit interface between sleeve and pin after fatigue testing.

[0067] Use an optical microscope or scanning electron microscope to observe the surface fatigue damage of the specimen. Figure 12As shown in the figure, ① is the coating and interface area on the surface of the specimen; ② is the coating and interface area in the cross section of the specimen, both of which are located at the position of maximum tensile stress.

[0068] S7. Based on the fatigue test results and fatigue damage microscopic observation results, the fatigue performance of wind turbine sliding bearings is comprehensively evaluated.

[0069] 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.

[0070] like Figure 13 As shown in Figure 1, (a) is a micrograph of the surface coating and interface area of ​​the specimen after the fatigue test; (b) is an enlarged view of the yellow dotted box area in Figure (a); among them, the position marked ① in Figure (a) is the coating, and the position marked ② is the substrate; the position indicated by the arrow in Figure (b) is the crack. According to 13, the sleeve structure of the sliding bearing may have 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 extension path that is not completely perpendicular to the loading direction.

[0071] like Figure 14 As shown in the figure, (a) is a cross-sectional micrograph of the specimen after fatigue test without considering the residual stress of interference fit; (b) is a cross-sectional micrograph of the specimen after fatigue test considering the residual stress of interference fit; (c) is a micrograph of fatigue damage at the interface; (d) is an enlarged view of the interface area in Figure (c); (e) is a macrograph of the position in Figure (c); among them, the position marked ① in Figure (a) is the coating, and the position marked ② is the substrate.

[0072] Figure (a) shows that when the interference fit residual stress is not considered, no obvious fatigue damage is observed in the three-point bending fatigue specimen after loading is completed; Figure (b) shows that when the interference fit residual stress is considered and the fatigue load is increased, slight cracking marks are visible at the bonding interface between the specimen coating and the substrate; Figure (c) shows that when the interference fit residual stress is considered, serious fatigue cracking occurs at the bonding interface between the specimen coating and the substrate; Figure (d) shows that the interface debonding caused by fatigue cracks does not necessarily occur entirely at the interface position, and the area near the interface is also a weak area; Figure (e) shows the position of the interface debonding area in the macroscopic photograph of the specimen.

[0073] In summary, when the three-point bending fatigue specimen is subjected to 8.0×10 7After the first loading cycle, if no significant deformation, coating shedding, or coating cracking occurs, the sliding bearing structure is considered to have good fatigue reliability and can meet service requirements. Otherwise, the structure is considered to have poor fatigue reliability and cannot meet service requirements. In other words, the fatigue performance evaluation method of the present invention can more accurately and realistically assess whether the combination of the sliding bearing substrate and coating has reliable fatigue performance, thereby providing reliable support for the fatigue strength design of wind turbine sliding bearings.

[0074] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A fatigue performance evaluation method for wind turbine sliding bearings, characterized in that: The steps include: S1. Establish a sliding bearing model based on finite element analysis and analyze the residual stress of the sleeve and pin interference fit in the sliding bearing, as well as the stress state of the sliding bearing when subjected to oil film pressure in the service environment; S2. Calculate the annular structural stress distribution of the sleeve and perform a differential calculation to determine the structural stress amplitude before and after oil film loading. S3. Design a three-point bending test and use finite element simulation to calculate the structural stress value of the sleeve section corresponding to the unit load; 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.

2. The fatigue performance evaluation method of a wind turbine sliding bearing according to claim 1, characterized in that: The specific steps of finite element modeling in S1 are: Step-1, set the interference fit; Step 2: Release the boundary: Release the strong constraint of the axis edge and set only weak constraints that do not produce overall displacement and rotation to observe the internal stress distribution caused by the interference fit. Step-3, apply oil film pressure.

3. The fatigue performance evaluation method of a wind turbine sliding bearing according to claim 2, characterized in that: In Step-3, Formula 1 is used to perform finite element loading of oil film pressure. Formula 1 is as follows: Where P(x) represents the radial normal stress in MPa, and x represents the distance from the center of the shaft in mm.

4. The fatigue performance evaluation method of a wind turbine sliding bearing according to claim 3, characterized in that: In S2, the annular structural stress distribution of the sleeve in Step-2 and Step-3 is calculated respectively to obtain the interference fit residual stress and the stress state after the residual stress is superimposed on the oil film pressure.

5. The fatigue performance evaluation method of a wind turbine sliding bearing according to claim 4, characterized in that: In S4, fatigue performance tests were carried out on the fatigue specimens of sliding bearing sleeves, where the fatigue specimens were in plate shape.

6. The fatigue performance evaluation method of a wind turbine sliding bearing according to claim 5, characterized in that: The fatigue damage characteristics of the specimen fracture, coating area and the interface between coating and base layer after fatigue test were observed microscopically. Based on the fatigue test results and fatigue damage microscopic observation results, the fatigue performance of wind turbine sliding bearings was comprehensively evaluated.

7. The fatigue performance evaluation method of a wind turbine 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 sleeve wall thickness is 8-11 mm, the tube length is 250-300 mm, and the sleeve and the pin shaft are centrally interference fit.

8. The fatigue performance evaluation method of a wind turbine sliding bearing according to claim 7, characterized in that: The interference fit between the sleeve and the pin is 0.05 mm.

9. The fatigue performance evaluation method of a wind turbine sliding bearing according to claim 8, characterized in that: When using finite element method to model the sliding bearing, the mesh adopts C3D8 solid element. The finest mesh is distributed on the surface of the shaft and the sleeve, with a size of 4~5mm; the coarsest mesh is distributed at the center of the shaft, with a size of 10mm, and a gradient transition is made in the middle.

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