Method for calculating ultimate strength of connecting bolt of main shaft and planet carrier of wind turbine generator

Abstract

The invention discloses a wind turbine generator main shaft and planet carrier connecting bolt ultimate strength calculation method which comprises the following steps: establishing a three-dimensional geometric model for calculating the ultimate strength of a main shaft-planet carrier connecting bolt according to stress analysis on a main transmission chain of a wind turbine generator; finite element models are established for parts except the main shaft-planet carrier connecting bolts in the three-dimensional geometric model; the method comprises the following steps: establishing a finite element model of main shaft-planet carrier connecting bolts, dividing each main shaft-planet carrier connecting bolt into four sections, namely a head nut connecting section, a screw section, a thread section and a tail thread screwing section, and modeling the four sections by adopting beam units with different diameters; setting a model boundary condition, and constraining the degree of freedom of related parts; and setting a load boundary condition and carrying out loading calculation. According to the main shaft-planet carrier connecting bolt, beam unit modeling is adopted, the diameter of each section of the bolt is set according to the stress condition of each section, the actual stress state of the bolt is closer, and the calculation result is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a method for calculating the ultimate strength of bolts connecting a main shaft and a planetary carrier of a wind turbine set. Background Art

[0002] The bolts connecting the main shaft and the planetary frame of the fan play an important role in converting wind energy into mechanical energy. Their strength performance determines the stability and reliability of the fan during normal use. The connection between the main shaft and the planetary frame is very important. According to the previous bolt calculation method, one is to establish a solid model of the bolt for calculation. The two circles of bolts will cause a large workload and low efficiency. In addition, the modeling of the solid bolts for different cross-sectional areas of the screw segment and the thread segment is too cumbersome. If only one cross-sectional area is used, the simulation result is not accurate enough compared with the actual situation; the second is to couple the bolts with the structural parts at the bolt hole attachment surface. However, in the calculation, the change of the contact surface fulcrum caused by the deformation of the structural parts will have a great influence on the bolts, and the results are not accurate enough. Summary of the invention

[0003] A series of simplified concepts are introduced in the Summary of the Invention, which will be further described in detail in the Detailed Description of the Invention. The Summary of the Invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the scope of protection of the claimed technical solution.

[0004] In order to at least partially solve the above problem, according to a first aspect of the present invention, a method for calculating the ultimate strength of bolts connecting a main shaft and a planet carrier of a wind turbine generator set is provided, comprising:

[0005] Based on the stress analysis of the main transmission chain of the wind turbine, a three-dimensional geometric model for calculating the ultimate strength of the main shaft-planet carrier connection bolts was established;

[0006] Establishing a finite element model for the components except the main shaft-planet carrier connection bolts in the three-dimensional geometric model;

[0007] Establish a finite element model of the main shaft-planet carrier connecting bolt, divide each main shaft-planet carrier connecting bolt into four sections: a head nut connecting section, a screw section, a thread section, and a tail thread screwing section, and use different diameter beam elements to model the four sections;

[0008] Set model boundary conditions to constrain the degrees of freedom of related components;

[0009] Set load boundary conditions and perform loading calculations.

[0010] Furthermore, a finite element model is established for the components other than the main shaft-planet carrier connecting bolts in the three-dimensional geometric model, including: solid modeling and meshing of the wheel hub, main frame, main shaft, parts of the front and rear main bearings except the rolling bodies, bearing seats, bearing seat-main frame connecting bolt entities, main shaft-planet carrier connecting nuts, gaskets and bolt sleeves, and planet carrier prostheses, and rolling bodies of the front and rear main bearings are modeled using beam units; and connection relationships between the components are established.

[0011] Furthermore, the connection relationship between the components is established, including: standard contact is set between the main frame and the bearing seat, between the main shaft-planetary carrier connecting nut and the gasket, between the gasket and the bolt sleeve, between the bolt sleeve and the main shaft, between the bolt sleeve and the planetary carrier prosthesis, between the main shaft and the planetary carrier prosthesis, between the front main bearing inner ring and the main shaft, between the front main bearing outer ring and the bearing seat, between the rear main bearing inner ring and the main shaft, and between the rear main bearing outer ring and the bearing seat; the contacts of the remaining components of the model are all set to binding contacts.

[0012] Furthermore, the finite element model of the main shaft-planet carrier connecting bolt is established, each main shaft-planet carrier connecting bolt is divided into four sections: a head nut connecting section, a screw section, a thread section and a tail thread screwing section, and the four sections are modeled using different diameter beam units, including:

[0013] The head nut connection section, thread section and tail thread engagement section are modeled according to the diameter corresponding to the stress cross-sectional area, and the screw section is modeled according to the nominal diameter of the bolt;

[0014] The head nut connection section and the tail thread screwing section establish a plurality of equally spaced beam unit layers along their entire axial lengths, and each beam unit layer includes a plurality of beam units which are distributed in an umbrella shape with equal angular distances and extend radially.

[0015] Furthermore, each beam unit of the head nut connecting section extends radially outward to the inner ring surface of the main shaft-planetary carrier connecting nut and merges a node with the inner ring surface of the main shaft-planetary carrier connecting nut to simulate the tightening of the bolt and the nut; each beam unit of the tail threaded screwing section extends radially outward to the inner ring surface of the planetary carrier prosthesis screwing part and merges a node with the inner ring surface of the planetary carrier prosthesis screwing part to simulate the tightening of the bolt and the structural part.

[0016] Furthermore, the finite element model of the main shaft-planet carrier connecting bolt is established, each main shaft-planet carrier connecting bolt is divided into four sections: a head nut connecting section, a screw section, a thread section and a tail thread screwing section, and the four sections are modeled using different diameter beam units, including:

[0017] Establishing a first stress concentration region beam unit, wherein the beam unit extends from the inner side of the head nut connection section toward the screw section by a distance equal to the pitch of the bolt; and

[0018] A second stress concentration region beam unit is established, and the beam unit extends from the inner side of the tail thread engagement section toward the screw section by a distance equal to the pitch of the bolt.

[0019] Furthermore, the finite element model of the main shaft-planet carrier connecting bolt is established, each main shaft-planet carrier connecting bolt is divided into four sections: a head nut connecting section, a screw section, a thread section and a tail thread screwing section, and the four sections are modeled using different diameter beam units, and also includes:

[0020] A portion of a certain depth is cut out on the planet carrier prosthesis along the outer ring surface of each bolt sleeve, and each main shaft-planet carrier connecting bolt assembly and the cut-out portion of the planet carrier prosthesis connected thereto are cut into two symmetrical halves along the radial plane. The mesh is divided using hexahedral units, and the nodes of the cut-out portion of the planet carrier prosthesis are merged with those of the planet carrier prosthesis; the remaining solid structures are meshed using tetrahedral units.

[0021] Furthermore, each beam unit layer includes six beam units distributed in an umbrella shape at an angular distance of 60 degrees and extending in the radial direction.

[0022] Furthermore, the model boundary conditions are set to constrain the degrees of freedom of related components, including: constraining the translational and rotational freedom of the bottom end of the main frame in the X, Y, and Z directions; and constraining the rotational freedom of the planetary frame prosthesis in the X direction.

[0023] Furthermore, the setting of load boundary conditions and the performing of loading calculations include: the bearing seat and the main frame are clamped with solid bolts, the main shaft and the planetary carrier prosthesis are clamped with beam unit modeling bolts, and in the analysis model, the bolt preload is simulated and applied to the screw segment unit; a remote point is established at the origin of the hub center coordinate system, and a load is applied to the remote point.

[0024] The method of the present invention is suitable for static strength calculation and analysis of connecting bolts between main shafts and planetary carriers of different wind turbines, and has wide applicability. In the specific modeling step, relevant components that have an impact on the stress of the main shaft-planetary carrier connecting bolts are solid modeled, and the main shaft-planetary carrier connecting bolts themselves are modeled using beam units. In addition, considering the factor that the stress area of ​​the threaded end of the high-strength bolt is reduced due to the existence of the thread, the diameters of the screw section, the threaded section, the nut connecting section and the threaded engagement section are set according to their respective stress conditions. Compared with the use of bolt solid modeling, it can be closer to the actual stress state of the bolt and the calculation result is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following drawings of the present invention are used as part of the present invention for understanding the present invention. The drawings show the embodiments of the present invention and their descriptions, and are used to explain the device and principle of the present invention. In the drawings,

[0026] Figure 1 It is a flow chart of a method for calculating the ultimate strength of bolts connecting the main shaft and the planet carrier of a wind turbine generator set according to an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of a geometric model used in a method for calculating the ultimate strength of bolts connecting the main shaft and the planet carrier of a wind turbine generator set according to an embodiment of the present invention;

[0028] Figure 3 for Figure 2 a cross-sectional view of the geometric model shown;

[0029] Figure 4 The beam unit model of the front and rear main bearing rolling elements is established by the method for calculating the ultimate strength of the connecting bolts between the main shaft and the planet carrier of the wind turbine generator set according to the embodiment of the present invention;

[0030] Figure 5 A schematic diagram of a main shaft-planet carrier connection bolt, a nut, a bolt sleeve and a cut-out portion of a planet carrier dummy according to an embodiment of the present invention;

[0031] Figure 6 A single main shaft-planet carrier connection bolt beam unit model of a method for calculating the ultimate strength of the main shaft and planet carrier connection bolts of a wind turbine generator set according to an embodiment of the present invention;

[0032] Figure 7 A schematic diagram of bolt connection between the main shaft and the planet carrier prosthesis of a wind turbine generator set according to a method for calculating the ultimate strength of bolts connecting the main shaft and the planet carrier of an embodiment of the present invention;

[0033] Figure 8 A schematic diagram of the main frame structure constraints of a method for calculating the ultimate strength of bolts connecting the main shaft and the planetary frame of a wind turbine generator set according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] Hereinafter, the present application will be described in more detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are not intended to limit the protection scope of the present application.

[0035] The present invention proposes a method for calculating the ultimate strength of the bolts connecting the main shaft and the planetary carrier of a wind turbine. Figure 1 As shown, the method includes:

[0036] Step 1: Based on the stress analysis of the main transmission chain of the wind turbine, a three-dimensional geometric model for calculating the ultimate strength of the main shaft-planet carrier connection bolts is established;

[0037] Step 2: establishing a finite element model for the components in the three-dimensional geometric model except the main shaft-planet carrier connection bolts;

[0038] Step 3: Establish a finite element model of the main shaft-planet carrier connecting bolt, divide each main shaft-planet carrier connecting bolt into four sections: a head nut connecting section, a screw section, a thread section, and a tail thread screwing section, and use different diameter beam elements to model the four sections;

[0039] Step 4: Set the model boundary conditions to constrain the degrees of freedom of related components;

[0040] Step 5: Set load boundary conditions and perform loading calculations.

[0041] like Figure 2 , Figure 3 and Figure 7 As shown, the three-dimensional model specifically includes a wheel hub 1, a main frame 2, a bearing seat 3, a main shaft 4, a planetary carrier prosthesis 5, a front main bearing outer ring 6, a front main bearing inner ring 7, a rear main bearing outer ring 8, a rear main bearing inner ring 9, a front main bearing rolling element 10, a rear main bearing rolling element 11, a main shaft rear end cover 12, a main shaft-planetary carrier connecting bolt 13, a bolt sleeve 14, a gasket 15, a nut 16, a bearing seat-main frame connecting bolt and nut 17, and a planetary carrier prosthesis cut-out portion 18.

[0042] The above step 2 may specifically include: solid modeling of the wheel hub 1, the main frame 2, the bearing seat 3, the main shaft 4, the front main bearing outer ring 6, the front main bearing inner ring 7, the rear main bearing outer ring 8, the rear main bearing inner ring 9, the bearing seat-main frame connecting bolts 17 (solid), the bolt sleeve 14, the gasket 15, the nut 16, and the main body of the planet carrier dummy 5, and meshing them using tetrahedral units; the rolling elements 10 and 11 of the front and rear main bearings are as follows: Figure 4 The Beam188 beam unit is used for modeling; the unit type and mesh size of each component of the model are shown in Table 1. The connection relationship between each component is established, and the main frame 2 and the bearing seat 3, the nut 16 and the gasket 15, the gasket 15 and the bolt sleeve 14, the bolt sleeve 14 and the main shaft 4, the bolt sleeve 14 and the planetary carrier prosthesis 5, the main shaft 4 and the planetary carrier prosthesis 5, the front main bearing inner ring 7 and the main shaft 4, the front main bearing outer ring 6 and the bearing seat 3, the rear main bearing inner ring 9 and the main shaft 4, and the rear main bearing outer ring 8 and the bearing seat 3 are set to standard contact with a friction coefficient of 0.2; the contact of the remaining components of the model is set to binding contact; the cut-out part 18 of the planetary carrier prosthesis is merged with the node of the planetary carrier prosthesis 5.

[0043] Model part Unit Type Grid size (mm) Wheels Solid185 150 Main frame Solid185 100 Front and rear bearings, planet carrier dummy, main shaft Solid185 40 Bearing seat Solid185 60 Bearing seat-main frame connecting bolt Solid185 25 Gasket, planet carrier prosthesis cut-out part Solid185 10 Pin bushing, large nut Solid185 20 Roller Beam188 bolt Beam188

[0044] Table 1

[0045] The bolts connecting the main shaft and the planet carrier of the wind turbine set of the present invention are ordinary high-strength bolts, which are divided into two circles, inner and outer, with 26 bolts in each circle. Figure 5In the above step 3, the head nut connection section, screw section, thread section and tail thread engagement section of each main shaft-planet carrier connection bolt 13 are modeled using different diameter beam units, which can specifically include: the head nut connection section, thread section and tail thread engagement section are modeled according to the diameter corresponding to the stress cross-sectional area, and the screw section is modeled according to the nominal diameter of the bolt; Figure 6 As shown in the figure (the left side view is the view of the bolt beam unit observed from the front, and the right side view is the view observed from the top), the head nut connection section and the tail threaded engagement section establish multiple equally spaced beam unit layers along their entire axial lengths, and each beam unit layer includes multiple beam units distributed in an umbrella shape with equal angular distances and extending radially. The number of beam unit layers can be determined according to the size of the bolt unit. Taking the head nut connection section as an example, if the nut height is 40mm, 6 beam unit layers can be set, and the distance between adjacent layers is 8mm; preferably, each beam unit layer includes 6 beam units distributed in an umbrella shape with an angular distance of 60° and extending radially, that is, each layer of "thread umbrella" extends 6 beam units radially outward from the center axis of the bolt to the inner ring surface of the nut, and the diameter of the "thread umbrella" is the same as the diameter of the thread section. Modeling with an angular distance of 60° can make its mesh divided into a symmetrical form, thereby eliminating the additional bending moment caused by mesh asymmetry. The nodes of each beam unit in the "thread umbrella" are merged with the inner ring surface of the nut to simulate the tightening of the bolt and the nut. Similarly, the number of beam unit layers of the tail bolt screwing section is also determined according to its own length. According to one embodiment of the present invention, the thread screwing section is evenly divided into 11 layers of "thread umbrellas" along its axial direction. Each layer of "thread umbrella" extends radially outward with the central axis of the bolt as the center, and 6 beam units are distributed at an angular distance of 60° to the inner ring surface of the screwing part of the planetary carrier prosthesis 5. The diameter of the "thread umbrella" is the same as the diameter of the threaded section. The nodes of each beam unit in the "thread umbrella" are merged with the inner ring surface of the screwing part of the planetary carrier prosthesis to simulate the tightening of the bolt and the structural part. Figure 6 The upper end of the left side view is the head nut connection section, and the lower end is the tail thread screwing section.

[0046] like Figure 5 As shown, step 3 of the present invention also includes cutting a certain depth portion on the planet carrier dummy along the outer ring surface of each bolt sleeve 14, cutting each main shaft-planet carrier connection bolt assembly and the cut-out portion of the planet carrier dummy connected thereto into two symmetrical halves along the radial plane, and using hexahedral units for meshing. The main shaft-planet carrier connection bolt assembly includes a bolt 13, a bolt sleeve 14, a gasket 15 and a nut 16. This setting facilitates hexahedral meshing and can eliminate the additional bending moment effect caused by mesh asymmetry.

[0047] The present invention also establishes beam units for the area where the bolt is subjected to the greatest stress, so as to accurately evaluate the results when calculating the bolt strength. Specifically, a first stress concentration area beam unit is established, and the beam unit extends from the inner side of the head nut connection section to the screw section by a distance equal to the pitch of the bolt; and a second stress concentration area beam unit is established, and the beam unit extends from the inner side of the tail thread engagement section to the screw section by a distance equal to the pitch of the bolt. Taking a bolt with a pitch of 5mm as an example, a beam unit with a length of 5mm is established from the inner side of the nut connection section and the thread engagement section at both ends of the head and tail toward the screw section.

[0048] like Figure 8 As shown, the above step 4 may include constraining the translational and rotational freedom of the bottom end of the main frame 2 in the X, Y, and Z directions and constraining the rotational freedom of the planet carrier prosthesis 5 in the X direction.

[0049] In step 5, since the bearing seat 3 and the main frame 2 are not the main focus positions, they are clamped with solid bolts; the main shaft 4 and the planetary frame prosthesis 5 are clamped with bolts 13 modeled by beam elements. In the analysis model, the bolt preload is simulated and applied to the screw segment unit; in the static strength analysis of the main shaft-planetary frame connection bolt 13, the load is applied through the hub center, that is, the origin of the hub center coordinate system establishes a remote point, and the load is applied to the remote point. Then calculate the deformation and stress cloud map, check the calculation results, pay attention to the 5mm beam unit part below the nut connection section and the threaded screwing section at both ends of the bolt head and tail, and obtain the maximum stress and deformation of the dangerous part of the bolt.

[0050] The method of the present invention is suitable for static strength calculation and analysis of connecting bolts between main shafts and planetary carriers of different wind turbines, and has wide applicability. In the specific modeling step, relevant components that have an impact on the stress of the main shaft-planetary carrier connecting bolts are solid modeled, and the main shaft-planetary carrier connecting bolts themselves are modeled using beam units. In consideration of the fact that the stress area of ​​the threaded end of the high-strength bolt is reduced due to the existence of the thread, the diameters of the screw section, the threaded section, the nut connecting section and the threaded engagement section are set according to their respective stress conditions. Compared with the solid modeling of the bolts, the method can more truly reflect the actual stress state and the calculation result is more accurate. In addition, the present invention also specifically establishes beam units for the parts of the bolts where stress concentration is prone to occur. Part of the prosthesis is cut out of the component connected to the bolts, and hexahedral meshing is performed together with the bolts to eliminate the influence of the additional bending moment caused by the asymmetric mesh, so that the result of the bolt ultimate strength calculation is more accurate.

[0051] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software may depend on the specific application and design constraints of the technical solution. The technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the embodiments of the present disclosure.

[0052] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0053] In the embodiments disclosed herein, the disclosed methods and products (including but not limited to devices, equipment, etc.) can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units can be only a logical function division. There can be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, and the indirect coupling or communication connection of devices or units can be electrical, mechanical or other forms.

[0054] The present invention has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above-mentioned embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention. The protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for calculating the ultimate strength of the bolts connecting the main shaft and the planetary carrier of a wind turbine generator set, characterized in that: include: Based on the stress analysis of the main transmission chain of the wind turbine, a three-dimensional geometric model for calculating the ultimate strength of the main shaft-planet carrier connection bolts was established; Establishing a finite element model for the components except the main shaft-planet carrier connection bolts in the three-dimensional geometric model; Establish a finite element model of the main shaft-planet carrier connecting bolt, divide each main shaft-planet carrier connecting bolt into four sections: a head nut connecting section, a screw section, a thread section, and a tail thread screwing section, and use different diameter beam elements to model the four sections; Set model boundary conditions to constrain the degrees of freedom of related components; Set load boundary conditions and perform loading calculations.

2. The method for calculating the ultimate strength of the connecting bolts between the main shaft and the planetary carrier of a wind turbine according to claim 1, characterized in that: The finite element model is established for the components other than the main shaft-planet carrier connecting bolts in the three-dimensional geometric model, including: solid modeling and meshing of the wheel hub, main frame, main shaft, parts of the front and rear main bearings except the rolling bodies, bearing seat, bearing seat-main frame connecting bolt entities, main shaft-planet carrier connecting nuts, gaskets and bolt sleeves, and planet carrier prostheses, and the rolling bodies of the front and rear main bearings are modeled using beam units; and the connection relationship between the components is established.

3. The method for calculating the ultimate strength of the connecting bolts between the main shaft and the planetary carrier of a wind turbine generator set according to claim 2, characterized in that: The connection relationship between the components is established, including: setting standard contact between the main frame and the bearing seat, between the main shaft-planetary carrier connecting nut and the gasket, between the gasket and the bolt sleeve, between the bolt sleeve and the main shaft, between the bolt sleeve and the planetary carrier prosthesis, between the main shaft and the planetary carrier prosthesis, between the front main bearing inner ring and the main shaft, between the front main bearing outer ring and the bearing seat, between the rear main bearing inner ring and the main shaft, and between the rear main bearing outer ring and the bearing seat; the contacts of the remaining components of the model are all set to binding contacts.

4. The method for calculating the ultimate strength of the connecting bolts between the main shaft and the planetary carrier of a wind turbine according to claim 1, characterized in that: The finite element model of the main shaft-planet carrier connecting bolt is established, each main shaft-planet carrier connecting bolt is divided into four sections: a head nut connecting section, a screw section, a thread section and a tail thread screwing section, and the four sections are modeled using different diameter beam units, including: The head nut connection section, thread section and tail thread engagement section are modeled according to the diameter corresponding to the stress cross-sectional area, and the screw section is modeled according to the nominal diameter of the bolt; The head nut connection section and the tail thread screwing section establish a plurality of equally spaced beam unit layers along their entire axial lengths, and each beam unit layer includes a plurality of beam units which are distributed in an umbrella shape with equal angular distances and extend radially.

5. The method for calculating the ultimate strength of the connecting bolts between the main shaft and the planetary carrier of a wind turbine generator set according to claim 4, characterized in that: Each beam unit of the head nut connecting section extends radially outward to the inner ring surface of the main shaft-planetary carrier connecting nut and merges a node with the inner ring surface of the main shaft-planetary carrier connecting nut to simulate the tightening of the bolt and the nut; each beam unit of the tail threaded screwing section extends radially outward to the inner ring surface of the planetary carrier prosthesis screwing part and merges a node with the inner ring surface of the planetary carrier prosthesis screwing part to simulate the tightening of the bolt and the structural part.

6. The method for calculating the ultimate strength of the connecting bolts between the main shaft and the planetary carrier of a wind turbine generator set according to claim 4, characterized in that: Also includes: Establishing a first stress concentration region beam unit, wherein the beam unit extends from the inner side of the head nut connection section toward the screw section by a distance equal to the pitch of the bolt; and A second stress concentration region beam unit is established, and the beam unit extends from the inner side of the tail thread engagement section toward the screw section by a distance equal to the pitch of the bolt.

7. The method for calculating the ultimate strength of the connecting bolts between the main shaft and the planetary carrier of a wind turbine generator set according to claim 4, characterized in that: Also includes: A portion of a certain depth is cut out on the planet carrier prosthesis along the outer ring surface of each bolt sleeve, and each main shaft-planet carrier connecting bolt assembly and the cut-out portion of the planet carrier prosthesis connected thereto are cut into two symmetrical halves along the radial plane. The mesh is divided using hexahedral units, and the nodes of the cut-out portion of the planet carrier prosthesis are merged with those of the planet carrier prosthesis; the remaining solid structures are meshed using tetrahedral units.

8. The method for calculating the ultimate strength of the connecting bolts between the main shaft and the planetary carrier of a wind turbine generator set according to claim 4, characterized in that: Each beam unit layer includes six beam units distributed in an umbrella shape at an angular distance of 60 degrees and extending in the radial direction.

9. The method for calculating the ultimate strength of the connecting bolts between the main shaft and the planetary carrier of a wind turbine generator set according to claim 1, characterized in that: The model boundary conditions are set to constrain the degrees of freedom of related components, including: constraining the translation and rotational degrees of freedom of the bottom end of the main frame in the X, Y, and Z directions; and constraining the rotational degree of freedom of the planetary frame prosthesis in the X direction.

10. The method for calculating the ultimate strength of the connecting bolts between the main shaft and the planetary carrier of a wind turbine generator set according to any one of claims 1 to 9, characterized in that: The load boundary conditions are set and the loading calculation is performed, including: the bearing seat and the main frame are clamped by solid bolts, the main shaft and the planetary frame dummy are clamped by beam unit modeling bolts, in the analysis model, the bolt preload is simulated and applied to the screw segment unit; a remote point is established at the origin of the hub center coordinate system, and a load is applied to the remote point.

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