Finite Element Analysis Method for Bolt Structure Model Based on Parameter Mapping

Abstract

The present invention relates to a finite element analysis and shaping method for a bolt structure model based on parameter mapping. The method adopts a design parameter series list to transfer the model parameter information of the bolt structure to the geometric model with the design parameters as the carrier, thereby realizing a process of quickly guiding the automatic generation of the geometric model of the bolt structure through the design parameter series list, and effectively improving the efficiency of bolt structure modeling. When generating a finite element model of the bolt structure, the present invention is based on the geometric model of the bolt structure quickly generated in the design parameter series list, and according to the size information of the bolt structure in the design parameter series list, the column structure, hexagonal head structure and thread structure in the bolt structure are quickly identified, and different structural features are divided into blocks, thereby effectively simplifying the geometric complexity of the overall structure of the bolt, and indirectly improving the accuracy and quality of mesh division. Refined mesh division is performed on the main stress-bearing area in the bolt structure, namely the thread structure, to guide the generation of a high-precision thread structure mesh.

Description

Technical Field

[0001] The present invention relates to a mechanical parts design and evaluation technology, and in particular to a finite element analysis and shaping method of a bolt structure model based on parameter mapping. Background Art

[0002] Bolt structures are widely used in the field of mechanical system design. Their simple structure and excellent fastening performance make them an indispensable part of mechanical system design. However, with the rapid development and widespread application of mechanical systems, more stringent requirements have been placed on the design of bolt structures. In the actual mechanical system design process, it is necessary to consider bolt structures of different specifications and thread types. In addition, during the operation of the mechanical system, it is also necessary to ensure that the bolt structure has sufficient reliability under different conditions to ensure the normal operation of the mechanical system. Therefore, how to analyze the overall stress conditions of the bolt structure under the conditions of different specifications, different thread types, and different load conditions, so as to ensure that the bolt structure can maintain normal working conditions during the operation of the mechanical system, is an urgent problem to be solved in the field of engineering machinery system design. In the field of mechanical system design, accurately analyzing the operating performance level of the mechanical system is of great significance to the field of mechanical system design.

[0003] Finite element analysis (FEA) is widely used in structural load analysis. With the rapid development and widespread adoption of computer technology, its application has expanded to nearly all areas of engineering science and technology. Finite element analysis of bolt structures in mechanical systems can quickly and effectively analyze the overall strength and stress conditions of bolt structures, enabling accurate evaluation of the design process.

[0004] In the design of mechanical systems, it is necessary to select bolt structures of different specifications, determine the thread characteristics of the bolts, and select the appropriate specifications, dimensions, and thread types of the bolt structures based on the different load conditions during operation to ensure reliable connections in the system. Therefore, the selection process of bolt structures for mechanical systems involves two important steps: first, determining the specifications, dimensions, and thread types of the bolt structures; and second, verifying whether the selected bolt structures can meet normal operating requirements under different operating conditions of the mechanical system. Summary of the Invention

[0005] To address the design and selection of bolt structures, a finite element analysis method for bolt structure models based on parameter mapping is proposed. Parameter mapping is used to rapidly generate finite element analysis models of bolt structures of varying sizes and thread types, allowing for analysis of the load and stress conditions of the bolt structures. This method can be used in the bolt structure design process during mechanical system design. By rapidly establishing a geometric model and finite element analysis model of the bolt structure through parameter mapping, the load and stress conditions of the bolt structure can be quickly and accurately analyzed to guide mechanical system design.

[0006] The technical solution of the present invention is: a finite element analysis and shaping method of a bolt structure model based on parameter mapping, comprising the following steps:

[0007] 1) Establish a design parameter series table containing bolt structure parameter information, map the parameter information in the design parameter series table to the geometric model through the parameter mapping method, and generate the geometric model of the bolt structure;

[0008] 2) Based on step 1), the geometric model is divided into blocks according to the geometric features, the blocks are divided into finite element meshes that meet the features, and the finite element mesh of the generated bolt structure is generated;

[0009] 3) Apply loads according to the load action coordinates and load action numerical finite element model in the design parameter series table; generate a finite element model for structural analysis.

[0010] Furthermore, the step 1) is implemented as follows:

[0011] 1.1) Design Bolt Structure Parameters: This is established based on the geometric characteristics of the bolt structure. The included design variables include: Bolt structure specifications, including polished rod diameter, polished rod length, bolt diameter, thread length, transition fillet radius, hexagonal head height, hexagonal head radius, nut diameter, and nut height; Bolt thread structure information, including pitch, root height, addendum height, and helix angle; Thread structure load parameters, including load action coordinates and load action values;

[0012] Enter various series of bolt structure parameter values in the design parameter series table, and use this to create a design parameter series table containing thread structure design variable parameters and parameter value information;

[0013] 1.2) Establish the threaded rod structure. The threaded rod structure consists of three regions: the bolt head region, the bolt polished rod region, and the bolt thread region. First, the cylindrical bolt polished rod structure is established using the two design variables of polished rod diameter and polished rod length. Then, the polished rod is sectioned at one end, using the bolt diameter as the circumference and the thread length as the distance, to generate the bolt thread region. Furthermore, a diameter height difference is created between the thread region and the polished rod region, and a rounded corner transition is created using the design variable transition fillet radius. Finally, the bolt head region is constructed at the other end of the polished rod.

[0014] 1.3) Generate a geometric model of the bolt structure's thread features in the threaded region through rotational sectioning. First, a thread guide line is generated on the end face of the bolt threaded region and on the outer wall of the cylinder in the threaded region, using the pitch and thread length as design variables. Next, a thread section is established at one end of the thread guide line, using the tooth root height, tooth addendum height, and helix angle design variables. Finally, the threaded region is sectioned using the thread section as the sectioning reference, the bolt structure's threaded region as the sectioning object, and the thread guide line as the sectioning path, thereby generating the bolt structure's threaded geometric features in the threaded region.

[0015] 1.4) The nut is further established using the bolt structure as the coordinate reference. The connecting end faces of the bolt structure head and the bolt structure polished rod area are used as the starting surfaces. The nut shank geometric model is established using the nut diameter and nut height as design variables. The bolt structure is subtracted from the nut structure through Boolean operations to generate the threaded hole of the nut structure, while ensuring that the nut structure and the threaded area of the bolt structure are properly engaged.

[0016] Furthermore, the step 2) is implemented as follows:

[0017] 2.1) Divide the entire bolt structure into blocks, and divide the bolt into a nut part, a threaded rod part, and a polished rod part based on a plane perpendicular to the screw axis;

[0018] 2.2) The threaded rod is divided into three parts according to the radial coordinates: the solid rod, the transition zone annulus, and the thread teeth from the inside out. The transition zone annulus is the transition part connecting the thread teeth and the internal solid cylinder.

[0019] 2.3) Perform swept meshing on the segmented threads and transition zone torus: First, select the threads and transition zone torus that have a complete half volume and call it the thread swept area. Then, perform mesh seeding on this area. The line segments on the mid-surface of the thread swept area are seeded in a detailed manner, including the number of radial and axial meshes on the teeth and the radial and axial meshes on the transition zone torus. The circumferential line segments of the thread swept area are then seeded. The mesh size setting needs to take into account the influence of the element's aspect ratio and Jacobian matrix.

[0020] 2.4) Directly perform swept meshing on the threaded polished rod area;

[0021] 2.5) Perform free meshing on other parts;

[0022] 2.6) The meshing of the nut structure refers to the meshing of the bolt, and the thread tooth part and its transition area are geometrically processed and meshed according to steps 2.2) and 2.3).

[0023] Furthermore, the transition zone torus network division method in step 2.2) is as follows: the transition zone torus is a torus with the screw axis as the center line, the outer diameter of the transition zone torus is the inner diameter of the thread tooth, and the inner diameter of the torus is half the inner diameter of the thread tooth; since the outer edge of the transition zone torus is connected to the thread tooth, stress concentration will occur in this area when the bolt is tightened, and high-precision mapping grid division is performed; in order to divide the high-precision mapping grid, the transition zone part is divided into blocks, and when dividing the blocks, the outer surface of the transition zone is ensured to be collinear with the spiral line at the root of the thread tooth, and the starting point of the spiral line is perpendicular to the axis of the screw, and then these perpendicular lines are used as reference lines, and spiral surfaces are generated with the spiral line as the generatrix, and the torus is divided into spirals using these spiral surfaces, and the spiral is divided using a plane passing through the axis of the torus to simplify the topological shape of the grid division area; the torus in the transition zone is divided into several half-torus bodies, and the topological shape of these torus bodies is a quadrangular prism with a rectangular cross-section, and mapping grid division is performed.

[0024] Furthermore, when the bolt is tightened, for the threaded connection area in the bolt structure with complex stress, the surface mesh is generated based on the threaded section. When selecting the body mesh to generate the guide surface, a refined design is used to increase the accuracy of the finite element analysis results. The minimum value of each side length of the threaded section is used as the point distance on the thread spiral guide line to generate a dense mesh layer of the body mesh guide surface, thereby increasing the number of body mesh hexahedrons of the threaded structure finally generated.

[0025] Furthermore, in step 3), the contact relationship between the thread areas of the nut and the bolt structure is established using the geometric relationship and the affiliation between the geometric features for the generated finite element mesh of the bolt structure; the load of the finite element model is applied according to the load action coordinates and load action values in the design parameter series table; the displacement and rotation of the cylindrical outer wall of the nut are fixedly constrained with the nut as the constraint object, and the bolt structure is finalized.

[0026] The beneficial effects of the present invention are as follows: the finite element analysis and shaping method of the bolt structure model based on parameter mapping of the present invention generates a geometric model of the bolt structure by means of parameter mapping. Compared with the traditional method of generating a geometric model, the model parameter information of the bolt structure is transmitted to the geometric model by means of a design parameter series list in the form of design parameters as a carrier, thereby realizing a process of quickly guiding the automatic generation of the geometric model of the bolt structure through the design parameter series list, and effectively improving the efficiency of bolt structure modeling; when generating the finite element model of the bolt structure, the present invention is based on the geometric model of the bolt structure quickly generated in the design parameter write list, and according to the dimensional information of the bolt structure in the design parameter series list, the cylindrical structure, hexagonal head structure and thread structure in the bolt structure are quickly identified, and different structural features are divided into blocks, thereby effectively simplifying the geometric complexity of the overall structure of the bolt and indirectly improving the accuracy and quality of mesh division; when generating the finite element mesh model of the bolt structure, the present invention performs fine mesh division on the main stress-bearing area in the bolt structure, namely the thread structure, mainly by generating a surface mesh based on the thread cross-section as a reference, and performing point scattering and layering on the thread guide line according to the minimum length of each side of the thread cross-section, thereby guiding the generation of a high-precision thread structure mesh. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of the finite element analysis and shaping method of the bolt structure model based on parameter mapping of the present invention;

[0028] Figure 2 A diagram showing a geometric model of a polished rod of a bolt structure in an embodiment of the method of the present invention;

[0029] Figure 3 A geometric model diagram of the threaded area of a bolt structure in a method embodiment;

[0030] Figure 4 A diagram showing a geometric model of a nut structure in an embodiment of the method of the present invention;

[0031] Figure 5 Schematic diagram of the bolt structure blocks in the embodiment of the method of the present invention;

[0032] Figure 6 Schematic diagram of the finite element mesh of the bolt structure in the embodiment of the method of the present invention;

[0033] Figure 7 Schematic diagram of a finite element model of a nut structure in an embodiment of the method of the present invention;

[0034] Figure 8 Schematic diagram of the contact between the bolt and the nut at the thread teeth in the embodiment of the method of the present invention. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0036] The bolt structure commonly seen in mechanical systems plays an important role in fastening the normal operation of the mechanical system. For the modeling and finite element analysis process of the bolt structure, a design parameter series table containing the bolt structure parameter information is first established. The parameter information in the design parameter series table is quickly mapped to the geometric model through the parameter mapping method to generate a geometric model of the bolt structure for system design. On this basis, the geometric model is divided into blocks according to the geometric features, and the blocks are divided into finite element meshes that meet the features. After the mesh of the entire bolt structure is generated, the load of the finite element model is applied according to the load action coordinates and load action values in the design parameter series table. The finite element model is further generated to perform structural analysis of the mechanical system. The specific steps include:

[0037] Step 1: Design a bolt structure parameter series table: This is established based on the geometric characteristics of the bolt structure. The included design variables include: bolt structure specifications, including polished rod diameter, polished rod length, bolt diameter, thread length, transition fillet radius, hexagonal head height, hexagonal head radius, nut diameter, and nut height; bolt thread structure information, including pitch, root height, addendum height, and helix angle; and thread structure load parameters, including load action coordinates and load action values. Enter multiple series of bolt structure parameter values into the design parameter series table to create a design parameter series table containing thread structure design variable parameters and parameter value information.

[0038] Step 2: Establish the threaded rod structure. The threaded structure consists of three areas: the bolt hexagonal head area, the bolt polished rod area, and the bolt thread area. First, the cylindrical bolt polished rod structure is established using the two design variables of polished rod diameter and polished rod length. Then, the polished rod is sectioned at one end of the polished rod with the bolt diameter as the circumference and the thread length as the distance to generate the bolt thread area. Furthermore, there is a diameter height difference between the thread area and the polished rod area, and the rounded corner transition is performed using the design variable transition fillet radius. Finally, the bolt hexagonal head area is constructed at the other end of the polished rod. The design variables involved include hexagonal head height and hexagonal head radius. Figure 2 shown.

[0039] Step 3: Generate a geometric model of the bolt structure thread features by rotating the section in the thread area. First, generate a thread spiral guide line on the end face of the bolt thread area and on the outer wall of the cylinder in the thread area with the pitch and thread length as design variables. Then, at one end of the thread spiral guide line, establish a thread section with the tooth root height, tooth addendum height and helix angle design variables. Finally, use the thread section as the sectioning reference, the bolt structure thread area as the sectioning object, and the thread spiral guide line as the sectioning path to section the thread area and generate the thread geometric features of the bolt structure in the thread area. Figure 3 shown.

[0040] Step 4: Use the bolt structure as the coordinate reference to further establish the nut. Take the hexagonal head of the bolt structure and the connecting end face of the polished rod area of the bolt structure as the starting surface, and use the nut diameter and nut height as design variables to establish the nut rod geometry model. Subtract the bolt structure from the nut structure through Boolean operations to generate the threaded hole of the nut structure, while ensuring that the nut structure and the threaded area of the bolt structure are normally engaged; Figure 4 shown.

[0041] Step 5: The next step is to perform finite element meshing on the bolt structure. First, the entire bolt structure is divided into blocks so that the meshing of the entire bolt structure can be performed later. Based on the plane perpendicular to the axis of the screw, the bolt is divided into the nut part, the threaded rod part, and the polished rod part; Figure 5 shown.

[0042] Step 6: Geometrically process the threaded rod to facilitate subsequent finite element meshing. Divide the rod into three parts according to radial coordinates: from the inside out, the solid rod, the transition zone annulus, and the thread. The transition zone annulus refers to the transition portion connected to the thread, connecting the thread and the internal solid cylinder. The transition annulus is a circular ring centered on the screw axis. Its outer diameter is equal to the inner diameter of the thread, and its inner diameter is half the inner diameter of the thread. Because the outer edge of the transition annulus connects to the thread, stress concentration occurs in this area when the bolt is tightened, requiring high-precision mapping meshing. To achieve high-precision mapping meshing, the transition zone needs to be divided into blocks. The block division should ensure that the outer surface of the transition zone is collinear with the helix at the root of the thread. Draw perpendicular lines from the starting point of the helix to the screw axis. These perpendicular lines are used as reference lines, and helical surfaces are generated with the helix as the generatrix. These helical surfaces are used to divide the annulus into helices. Considering the meshing limitations of commercial finite element software, the spiral was segmented using a plane passing through the torus' axis to simplify the topology of the meshing area. This series of operations split the torus in the transition zone into several halves. These halves have the topological shape of a quadrangular prism with a rectangular cross-section, facilitating mapping meshing.

[0043] Step 7: Sweep the cut threads and transitions. First, select the thread and transition area that represents half of the complete volume, calling it the thread sweep region. Then, mesh seeding is performed on this area, refining the line segments on the mid-surface of the thread sweep region. This includes the number of radial and axial meshes for the teeth and the radial and axial meshes for the transitions. Mesh seeding is then performed on the circumferential line segments of the thread sweep region. The mesh size should be adjusted based on factors such as the element's slenderness ratio and Jacobian matrix.

[0044] Step 8: Perform swept meshing on the polished rod area. Since the polished rod has a very regular shape, swept meshing can be performed directly. First, mesh seeding is performed using radial, axial, and circumferential line segments. The topology of the polished rod is a cylinder, with the plane passing through the cylinder axis as the longitudinal symmetry plane. Using the longitudinal symmetry plane as the starting plane, perform swept meshing on the polished rod area by rotating around the central axis.

[0045] Step 9: Free meshing of other parts. After high-precision hexahedral meshing of the area of interest, free meshing of the remaining parts can be performed. Mesh adaptation is performed on the sweeping area and the transition area between the free mesh to ensure the continuity of the finite element mesh, formulate an appropriate mesh growth rate, and reduce the number of meshes as much as possible to save computing resources. Figure 6 shown.

[0046] Step 10: The meshing of the nut structure refers to the meshing of the bolt, and the thread tooth part and its transition area refer to steps 6 and 7 to perform geometric processing and meshing of the nut. Figure 7 shown.

[0047] Step 11: Use the geometric relationship and the affiliation between geometric features to establish the contact relationship between the thread areas of the nut and bolt structure, and complete the establishment of the finite element model of the entire bolt structure.

[0048] Step 12: Apply the load of the finite element model to the generated finite element mesh of the bolt structure according to the load action coordinates and load action values in the design parameter series table; use the nut as the constraint object and clamp the displacement and rotation of the outer wall of the nut cylinder.

[0049] In step 1, the design parameter series table is established, and the transmission and representation of the bolt structure model data are realized by using the design variables as the actual specific model numerical carriers of the bolt structure; the design parameter series table is established to establish multiple series of structural parameters of the bolt structure, including the specification and size information of the bolt structure, the characteristic information of the bolt structure thread and the force information of the bolt structure. By adding, deleting and modifying the parameter series in the design parameter series table, the management and archiving of the bolt structure model parameter information is realized through the design parameter series table.

[0050] In step 2, in the overall geometric model project of the bolt structure, the design parameters in the design parameter series table are used as the actual parameter values of the geometric model, and the mapping of the bolt structure series parameter information stored in the design parameter series table to the actual parameter values in the bolt structure geometric model is realized, thereby realizing the indirect parameterization and rapid management of the bolt structure model with the design parameter series table as the intermediate medium.

[0051] In step 4, when generating the thread features of the nut result, the Boolean operation method is used to quickly generate the thread features corresponding to the bolt structure. At the same time, since the Boolean operation can ensure that there is no structural interference between the threads of the bolt structure and the nut result, the normal engagement of the threads between the bolt structure and the nut structure is ensured.

[0052] In step five, when generating the mesh of the entire bolt structure, the entire bolt structure is first divided into blocks. The hexagonal head area, the bare rod area, and the threaded area without a threaded structure in the bolt structure, as well as the cylindrical structure without a threaded structure in the nut structure are divided into blocks. At the same time, the threaded areas in the bolt structure and the nut structure are separated, and the entire bolt structure is divided into blocks according to its geometric features, simplifying the complex bolt structure into a block structure with a single geometric feature.

[0053] In step six, for the threaded connection area with complex stress in the bolt structure, the surface mesh is generated based on the threaded section. When selecting the body mesh to generate the guide surface, refined design can be used to increase the accuracy of the finite element analysis results. The minimum value of the side lengths of the threaded section is used as the point distance on the thread spiral guide line to generate a dense mesh layer on the body mesh guide surface, thereby increasing the number of hexahedrons of the threaded structure body mesh generated in the end.

[0054] The adaptability of the present invention will be illustrated below using a bolt assembly comprising a bolt and a nut. Based on the bolt's structural dimensions, a design parameter series is established, as shown in Table 1. The design variables included are: bolt structural specifications, including polished rod diameter, polished rod length, bolt diameter, thread length, transition fillet radius, hexagonal head height, hexagonal head radius, nut diameter, and nut height; and bolt thread structural information, including pitch, tooth root height, tooth addendum height, and helix angle.

[0055] Table 1

[0056] Design variables Numerical Design variables Numerical Polished rod diameter 8.2mm Pitch 3 Polished rod length 18mm Tooth root height 41.952mm Bolt diameter 10mm Tooth addendum height 38.752mm Thread length 27mm Helix angle 30° Transition fillet radius 3mm Nut diameter 76mm Hexagon head height 10mm Nut height 32mm Hexagonal head circumscribed circle radius 3.5mm

[0057] Further establish the overall geometric model of the bolt, and establish the bolt hexagonal head area, bolt polished rod area and bolt thread area in the overall bolt model according to the design variables in the design parameter series table. The overall geometric model of the bolt is as follows: Figure 2 Then, the geometric model of the bolt structure thread features is generated by rotating the section in the thread area. The design variables in the design variable system table are also used to generate the thread geometric features of the bolt structure in the thread area. Figure 3 shown.

[0058] Further establish the nut corresponding to the bolt, generate the threaded hole of the nut structure through Boolean operation, and ensure the normal meshing of the threaded area of the nut structure and the bolt structure. The geometric model of the nut structure is as follows Figure 4 shown.

[0059] Then we start to build a finite element mesh model for the geometric model. First, we divide the whole bolt structure into blocks, such as Figure 5 As shown in the figure, it is divided into three parts: threaded rod, nut and polished rod. The geometric models of the three parts are meshed and the volume mesh is established, as shown in the figure. Figure 6 The mesh division of the nut structure refers to the mesh division of the bolt, as shown in Figure 7 As shown. And according to the coordinates and geometric relationships, the contact pair is established, as shown Figure 8 The schematic diagram of the contact between the bolt and the nut at the thread teeth completes the establishment of the complete finite element model.

[0060] The present invention realizes the automatic establishment of contact pairs of thread teeth. The contact pairs include the selection of contact surfaces on the thread teeth of the bolt and nut and the establishment of contact pairs. The specific process is: first, line segments on the plane passing through the axis of the torus body are selected. These line segments include the reference plane geometric lines of the thread teeth and the geometric lines of the transition body area; then, the radial geometric lines of the thread teeth are selected using radial coordinates; then, the geometric surfaces associated with these geometric lines are selected, and the geometric surfaces on the plane passing through the axis of the torus body are removed; then, the nodes associated with the geometric surfaces are selected; according to the above steps, the thread surface nodes of the bolt and nut can be selected; finally, the contact pairs of the thread surface nodes of the bolt and nut are established.

[0061] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A finite element analysis method for bolt structure model based on parameter mapping, characterized in that: The steps include: 1) Establish a design parameter series table containing bolt structure parameter information, map the parameter information in the design parameter series table to the geometric model through the parameter mapping method, and generate the geometric model of the bolt structure; 2) Based on step 1), the geometric model is divided into blocks according to the geometric features, and the blocks are divided into finite element meshes that meet the features to generate the finite element mesh of the bolt structure; 3) Apply loads to the finite element model according to the load action coordinates and load action values in the design parameter series table to generate a finite element model structural analysis; the implementation method of step 1) is as follows: 1.1) Design Bolt Structural Parameters: Create a design parameter list based on the geometric characteristics of the bolt structure. Design variables include: Bolt structural specifications, including polished rod diameter, polished rod length, bolt diameter, thread length, transition fillet radius, hexagonal head height, hexagonal head radius, nut diameter, and nut height; Bolt thread structural information, including pitch, root height, addendum height, and helix angle; Thread structural load parameters, including load action coordinates and load action values; Enter various series of bolt structure parameter values in the design parameter series table, and use this to create a design parameter series table containing thread structure design variable parameters and parameter value information; 1.2) Establish the threaded rod structure. The threaded rod structure consists of three regions: the bolt head region, the bolt polished rod region, and the bolt thread region. First, the cylindrical bolt polished rod region is established using the two design variables of polished rod diameter and polished rod length. Then, the polished rod is sectioned at one end face, using the bolt diameter as the circumference and the thread length as the distance, to generate the bolt thread region. The thread region and the polished rod region have a height difference in diameter, and a transition fillet radius is used to create the transition. Finally, the bolt head region is constructed at the other end face of the polished rod. 1.3) Generate a geometric model of the bolt structure's thread features by rotating the threaded area. Generate a thread guide line on the outer wall of the cylinder in the threaded area, using the pitch and thread length as design variables. Next, establish a thread section at one end of the thread guide line, using the tooth root height, tooth addendum height, and helix angle as design variables. Finally, section the threaded area using the thread section as the sectioning reference, the bolt structure's threaded area as the sectioning target, and the thread guide line as the sectioning path. This generates the bolt structure's threaded geometric features within the threaded area. 1.4) The nut is further established using the bolt structure as the coordinate reference. The bolt structure head and the connecting end surface of the bolt structure polished rod area are used as the starting surfaces. The nut diameter and nut height are used as design variables to establish the nut shank geometric model. The bolt structure is subtracted from the nut structure through Boolean operations to generate the threaded hole of the nut structure, while ensuring that the nut structure and the threaded area of the bolt structure are properly engaged.

2. The finite element analysis and shaping method of the bolt structure model based on parameter mapping according to claim 1 is characterized in that: The implementation method of step 2) is as follows: 2.1) Divide the entire bolt structure into blocks, dividing the bolt into the nut part, the threaded rod part, and the polished rod part based on a plane perpendicular to the screw axis; 2.2) The threaded rod is divided into three parts according to the radial coordinates. From the inside out, they are the solid rod, the transition zone annulus, and the thread teeth. The transition zone annulus is the transition part connecting the thread teeth and the internal solid cylinder. 2.3) Perform swept meshing on the segmented threads and transition zone torus: First, select the thread threads and transition zone torus that have a complete half volume and call it the thread swept area. Then, perform mesh seeding on this area. The line segments on the mid-surface of the thread swept area are seeded in a detailed manner, including the number of radial and axial meshes on the teeth and the radial and axial meshes on the transition zone torus. The circumferential line segments of the thread swept area are then seeded. The mesh size should take into account the influence of the element's aspect ratio and Jacobian matrix. 2.4) Directly perform swept meshing on the threaded polished rod area; 2.5) Perform free meshing on other parts; 2.6) The meshing of the nut structure refers to the meshing of the bolt, and the thread tooth part and its transition area are geometrically processed and meshed according to steps 2.2) and 2.3).

3. The finite element analysis and shaping method of the bolt structure model based on parameter mapping according to claim 2 is characterized in that: The transition zone torus meshing method in step 2.2) is as follows: the transition zone torus is a torus with the screw axis as the centerline, the outer diameter of the transition zone torus is equal to the inner diameter of the thread, and the inner diameter of the torus is half the inner diameter of the thread. Since the outer edge of the transition zone torus is connected to the thread, stress concentration will occur in this area when the bolt is tightened, requiring high-precision mapping meshing. To divide the high-precision mapping-type mesh, the transition zone is divided into blocks. During the block division, the outer surface of the transition zone is ensured to be collinear with the helix line at the root of the thread. The starting point of the helix line is perpendicular to the axis of the screw. Then, helical surfaces are generated using these perpendicular lines as reference lines and the helix line as the generatrix. The torus is divided into helices using these helical surfaces. The helices are divided using a plane passing through the torus axis to simplify the topology of the meshing area. The transition zone torus is then divided into a plurality of half toruses. The topology of these toruses is a quadrangular prism with a rectangular cross-section, and then mapping meshing is performed.

4. The finite element analysis and shaping method of a bolt structure model based on parameter mapping according to claim 3 is characterized in that: When the bolt is tightened, a surface mesh is generated based on the threaded connection area in the bolt structure that is subjected to complex forces, using the threaded section as a reference. When selecting the body mesh to generate the guide surface, a refined design is used to increase the accuracy of the finite element analysis result. The minimum value of each side length of the threaded section is used as the point scattering distance on the thread spiral guide line, and a dense mesh layer of the body mesh guide surface is generated, thereby increasing the number of hexahedrons of the threaded structure body mesh that is finally generated.

5. The finite element analysis and shaping method of a bolt structure model based on parameter mapping according to any one of claims 1 to 4, characterized in that: In step 3), for the generated finite element mesh of the bolt structure, a contact relationship between the thread areas of the nut and the bolt structure is established using the geometric relationship and the membership relationship between the geometric features; the load of the finite element model is applied according to the load action coordinates and load action values in the design parameter series table; the displacement and rotation of the cylindrical outer wall of the nut are fixedly constrained with the nut as the constraint object, and the bolt structure is finalized.

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