Modular hexahedral mesh model construction method for extruder cone thread structure

Abstract

The application belongs to the technical field of finite element numerical analysis, and particularly relates to a modular hexahedral mesh model construction method for a taper thread structure of an extruding machine, which firstly acquires characteristic parameters of a target taper thread, and then processes the parameters by using a commercial finite element software: an original mesh entity of a single pitch is constructed by drawing and combining a cylindrical ring mesh and a transition mesh; after being scaled by an equal ratio to match a target size, an overall structure original mesh covering a full length of the thread is formed by arraying and merging in an axial direction; based on an accurate geometric expression of the constructed taper thread profile, node coordinate deformation of the above mesh is driven by a linear interpolation algorithm, so that it accurately matches a target geometric shape, thereby automatically generating high-quality hexahedral mesh models of inner and outer taper threads. The method avoids tedious work of manual mesh division of a complex taper thread structure, and significantly improves the efficiency and model accuracy of finite element analysis of a taper thread connecting structure of a perforating system of a heavy extruding machine.

Description

Technical Field

[0001] This invention belongs to the field of finite element numerical analysis technology, specifically relating to a method for constructing a modular hexahedral mesh model of an extruder tapered thread structure. Background Technology

[0002] Tapered thread connections are critical load-bearing and sealing components in the piercing system of heavy-duty extruders. Their stress distribution, contact state, and fatigue life under extreme heavy loads and high torsional loads directly affect the safety and reliability of the entire equipment. Due to the structure's enormous size, complex service conditions, and extremely high experimental costs, precise mechanical analysis using finite element numerical simulation (FEM) technology has become an indispensable core method for optimizing its design and predicting its performance. Tapered thread connections represent a typical problem involving the coupling of geometric and contact nonlinearities, and the quality of the mesh directly determines the convergence, accuracy, and computational efficiency of the finite element analysis. However, due to the complex spatial helical surface and taper characteristics of tapered threads, achieving high-quality, especially fully hexahedral, automated mesh generation has always been a significant technical challenge.

[0003] However, existing methods still have significant limitations when dealing with large-size, multi-pitch tapered threads for heavy-duty extruders: they rely on a lot of manual operations, making it difficult to achieve parameterization and automation. This results in the current tapered thread mesh modeling process being cumbersome and inefficient, and it is difficult to adapt to the rapid adjustment of different design parameters. This seriously restricts the timeliness and reliability of using finite element simulation to guide the design and optimization of tapered thread connection structures for heavy-duty extrusion equipment.

[0004] For example, patent CN106951647B discloses a method for generating a tapered thread hexahedral mesh by creating reference surfaces, intersection lines, and ensuring alignment of mating surface nodes. However, this method heavily relies on multiple manual cutting, point placement, and boundary settings of the specific 3D geometric model. Another example is patent CN117874952A, which discloses a high-precision modeling method for asymmetric threads. This method requires manually drawing 2D meshes and helical lines to generate the thread mesh, resulting in a cumbersome process, a large preprocessing workload, and difficulty in automatically updating the model under rapid changes in design parameters. It lacks the parametric and automated capabilities required for practical engineering applications. Furthermore, patents CN106202639B (a finite element mesh modeling method for MJ bolts and nuts) and CN116070477A (a fine modeling method for a self-locking finite element model of an aero-engine) both establish precise cylindrical coordinate equations for the thread profile and use node offset or interpolation algorithms to generate a hexahedral mesh with shared nodes. However, the methods provided by the two patents are limited to specific thread profiles such as MJ bolts and self-locking nuts. When dealing with models of different sizes and structures of non-standard tapered threads used in heavy equipment applications with varying parameters such as taper and thread length, it is necessary to re-divide and draw the original mesh. There is a lack of a standardized process for quickly constructing an overall long thread model from basic unit modules.

[0005] Therefore, there is an urgent need to develop an automated method for generating tapered thread meshes that can balance modeling efficiency, geometric accuracy, and versatility, so as to achieve rapid construction of high-quality hexahedral meshes, thereby enhancing the engineering practical value of finite element analysis and providing efficient and reliable technical support for the refined design, performance evaluation, and optimization of tapered thread connection structures in heavy extrusion press piercing systems. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a modular hexahedral mesh model construction method for the tapered thread structure of an extruder. Through a parameterized and automated modular process, the cumbersome manual operation required in traditional tapered thread mesh generation is avoided, enabling the rapid generation of high-quality hexahedral meshes. This significantly enhances the convergence, calculation accuracy, and reliability of finite element analysis, providing efficient and reliable technical support for the refined design, performance evaluation, and optimization of the tapered thread connection structure in the piercing system of heavy-duty extruders.

[0007] The technical solution of this invention is: A modular hexahedral mesh model construction method for the tapered thread structure of an extruder includes the following steps: Obtain the characteristic parameters of the target tapered thread connection structure; Based on the feature parameters, cylindrical ring meshes of different densities are drawn as the original meshes of the threaded region and cylindrical transition meshes are drawn as the original meshes of the non-threaded region. The original mesh entities of single-pitch tapered external threads and single-pitch tapered internal threads are obtained by merging common nodes. The original mesh entities of single-pitch tapered external threads and single-pitch tapered internal threads are scaled proportionally in both axial and radial dimensions to achieve matching with the pitch and radial dimensions of the target tapered thread. The scaled original mesh entities of the single-pitch tapered external thread and the single-pitch tapered internal thread are arrayed along the axial direction, and the common node merging operation is performed on all the arrayed mesh entities to obtain the original mesh of the overall external thread structure and the original mesh of the overall internal thread structure, respectively. Based on the aforementioned feature parameters, geometric feature expressions for the profiles of single-pitch tapered external threads and single-pitch tapered internal threads are constructed. Then, using a linear interpolation algorithm, the corresponding node coordinates in the original meshes of the overall external thread structure and the overall internal thread structure are adjusted to ensure that the original meshes of the overall external thread structure and the overall internal thread structure accurately match the geometry of the target tapered thread, thereby obtaining the final hexahedral mesh model.

[0008] Preferably, the step of drawing cylindrical annular meshes of different densities as the original mesh of the thread region includes: first drawing two circles with inner and outer diameters to represent the annular surface entities of the inner and outer diameters of the thread region respectively; then, setting mesh nodes in four equal parts on the annular surface entities to make the central non-transition region a radially symmetrical two-dimensional mesh; and finally, stretching the two-dimensional mesh along the axial direction into a hexahedral mesh, and using the obtained hexahedral mesh as the original mesh of the thread region.

[0009] Preferably, the step of drawing cylindrical transition meshes of different densities as the original mesh of the non-threaded region includes: drawing a certain proportion of two-dimensional transition meshes along the axial direction, rotating and stretching them into hexahedral meshes, and then drawing a certain proportion of transition meshes along the radial direction so that the central non-transition region is a radially symmetrical two-dimensional mesh, stretching it along the axial direction into a hexahedral mesh, and the number of stretched meshes meeting the transition requirements from the threaded mesh region to the non-threaded mesh region, thus serving as the original mesh of the non-threaded region.

[0010] Preferably, the original mesh entity of the single-pitch tapered external thread is the original mesh entity that characterizes the generation of a tapered external thread hexahedral mesh structure by changing the nodes under a single pitch size; the original mesh entity of the single-pitch tapered internal thread is the original mesh entity that characterizes the generation of a tapered internal thread hexahedral mesh structure by changing the nodes under a single pitch size.

[0011] Preferably, the proportional axial scaling is based on adjusting the axial coordinates of the original mesh entities of the single-pitch tapered external thread and the single-pitch tapered internal thread based on the pitch of the target tapered thread, and the proportional radial scaling is based on adjusting the radial coordinates of the original mesh entities of the single-pitch tapered external thread and the single-pitch tapered internal thread based on the maximum and minimum diameters of the target tapered thread, so as to achieve matching of the pitch and diameter dimensions of the original mesh entities of the single-pitch tapered external thread and the single-pitch tapered internal thread with the target tapered thread.

[0012] Preferably, the scaled original mesh entities of the single-pitch tapered external thread and the original mesh entities of the single-pitch tapered internal thread are arrayed and then a thread transition section with a length of half a pitch is added to ensure mesh continuity.

[0013] Preferably, the geometric characteristic expression of the profile of the single-pitch tapered external thread is based on the radial distance dimension of the profile of the single-pitch tapered external thread within one pitch, by dividing the profile of the single-pitch tapered external thread according to the pitch. Project to 0-2 In a cylindrical coordinate system, the radial coordinates of the cross-section used to calculate a single-pitch tapered external thread. With angle The relationship is determined by the following formula: , in, , , , , ; In the formula, The radial coordinates of the cross-section of a single-pitch tapered external thread. The maximum outer diameter of the target tapered external thread is the single-pitch tapered external thread. The pitch of the target tapered thread for a single-pitch tapered external thread. This is the original triangle height of the tooth profile angle of a single-pitch tapered external thread, used to define the profile height of the single-pitch tapered external thread. The taper of a single-pitch tapered external thread. This is the axial distance from the profile of a single-pitch tapered external thread to the major diameter of the external thread. The tooth radius of a single-pitch tapered external thread. For the angle parameters in the cylindrical coordinate system, , , and These are all boundary parameters of the profile of a single-pitch tapered external thread, used to distinguish between the root fillet, the working surface of the thread, and the tip of the thread.

[0014] Preferably, the geometric characteristic expression of the profile of the single-pitch tapered internal thread is based on the radial distance dimension of the profile of the single-pitch tapered internal thread within one pitch, and the profile of the single-pitch tapered internal thread is expressed according to the pitch. Project to 0-2 In cylindrical coordinate system, the radial coordinate of the cross section of a single-pitch tapered internal thread With angle The relationship is determined by the following formula: , in, , , , , , ; In the formula, The radial coordinates of the cross-section of a single-pitch tapered internal thread. The maximum inner diameter of the target tapered thread. The minimum inner diameter of the target tapered thread for a single-pitch tapered internal thread. The pitch of the target tapered thread for a single-pitch tapered internal thread. The height of the original triangle representing the tooth profile angle of a single-pitch tapered internal thread. The taper of a single-pitch tapered internal thread. This is the axial distance from the profile of a single-pitch tapered internal thread to the major diameter of the internal thread. The tooth profile radius of a single-pitch tapered internal thread. For the angle parameters in the cylindrical coordinate system, , , and These are all boundary parameters of the profile of a single-pitch tapered internal thread, used to distinguish between the root fillet, the working surface of the thread, and the tip of the thread.

[0015] Preferably, the step of adjusting the node coordinates by the linear interpolation algorithm includes: reading the node coordinates of the original mesh of the external thread integral structure or the original mesh of the internal thread integral structure, calculating the new coordinates of each node by linear interpolation according to the corresponding profile geometric feature expression, and updating the original mesh of the external thread integral structure or the original mesh of the internal thread integral structure to achieve accurate matching of geometric shapes.

[0016] Compared with the prior art, the modular hexahedral mesh model construction method for the extruder tapered thread structure of the present invention has the following advantages: This invention avoids the complex preprocessing process of converting a solid model into a mesh model for tapered thread connection structures. By using modular original mesh components, based on the geometric features of the tapered thread profile, it realizes the construction of a refined, dimensionally controllable hexahedral mesh model of the tapered thread connection structure, improving the accuracy and efficiency of finite element numerical analysis of the tapered thread connection structure, and providing theoretical support for the design optimization of tapered thread connection structures in heavy extrusion press piercing systems. Attached Figure Description

[0017] Figure 1 This is a geometric model of the piercing system of a heavy-duty extruder in an embodiment of the present invention; Figure 2 This is a schematic diagram of the original mesh of the thread region in the original mesh of a single-pitch conical external thread structure, where cylindrical and annular meshes of different densities are drawn in commercial finite element software in an embodiment of the present invention. Figure 3 This is a schematic diagram of the original mesh of the thread transition region in the original mesh of the single-pitch conical external thread structure, which is drawn in commercial finite element software with cylindrical transition meshes of different densities in an embodiment of the present invention. Figure 4 This is a schematic diagram illustrating the merging of the original meshes of the threaded region and the original meshes of the non-threaded region in an embodiment of the present invention. Figure 5 This is a schematic diagram of the single-pitch original model array and common node merging operation in an embodiment of the present invention; Figure 6 This is a schematic diagram of the thread profile of the tapered external thread structure in an embodiment of the present invention; Figure 7 This is a schematic diagram of the grid nodes of the original grid tapered external thread region of the overall structure modified according to the specific tapered external thread connection structure characteristics in this embodiment of the invention; Figure 8 This is a schematic diagram of the overall refined thread hexahedral mesh model of the tapered external thread structure obtained by adjusting the nodes according to the specific characteristics of the tapered external thread connection structure in an embodiment of the present invention. Figure 9 This is a roadmap for constructing a modular, fine hexahedral mesh model of the tapered external thread connection structure in this invention embodiment; Figure 10 This is a schematic diagram of the original mesh of the thread region in the original mesh of a single-pitch conical internal thread structure, where cylindrical annular meshes of different densities are drawn in commercial finite element software in an embodiment of the present invention. Figure 11 This is a schematic diagram of the original mesh of the thread transition region in the original mesh of a single-pitch conical external thread structure, using cylindrical annular transition meshes of different densities drawn in commercial finite element software. Figure 12This is a schematic diagram illustrating the merging of the original meshes of the threaded region and the original meshes of the non-threaded region in an embodiment of the present invention. Figure 13 This is a schematic diagram of the single-pitch original model array and common node merging operation in an embodiment of the present invention; Figure 14 This is a schematic diagram of the thread profile of the tapered internal thread structure in an embodiment of the present invention; Figure 15 This is a schematic diagram of the grid nodes of the original grid tapered external thread region of the overall structure modified according to the specific tapered internal thread connection structure characteristics in this embodiment of the invention; Figure 16 This is a schematic diagram of the overall refined thread mesh model of the tapered internal thread structure obtained by adjusting the nodes according to the specific characteristics of the tapered internal thread connection structure in an embodiment of the present invention. Figure 17 This is a roadmap for constructing a modular, fine hexahedral mesh model of the tapered internal thread connection structure in this invention embodiment; Figure 18 This is a schematic diagram of a hexahedral mesh model of the tapered thread structure of the heavy extruder piercing system constructed by the modeling method in this embodiment of the invention; Figure 19 This is a schematic diagram of a hexahedral mesh model of a multi-segment tapered thread structure of a heavy-duty extruder piercing system constructed by the modeling method in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0020] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0021] See Figures 1 to 19As shown, in order to avoid the tediousness of manual operation in traditional tapered thread mesh generation, achieve rapid generation of high-quality hexahedral meshes, and enhance the convergence, computational accuracy, and reliability of finite element analysis, this embodiment provides a modular hexahedral mesh model construction method for the tapered thread connection structure of an extruder, mainly including the following steps: Obtain the characteristic parameters of the target tapered thread connection structure, including pitch, maximum diameter, thread taper, tooth angle, tooth radius, and thread segment length; Based on the characteristic parameters of the target tapered thread connection structure, cylindrical ring meshes of different densities were drawn in commercial finite element software (Hypermesh) as the original meshes of the threaded region and cylindrical transition meshes as the original meshes of the non-threaded region. The original mesh entities of single-pitch tapered external threads and single-pitch tapered internal threads were created respectively through common node operation. By combining commercial finite element software (Abaqus) and open-source programming language (Python), the original mesh entities of single-pitch tapered external threads and single-pitch tapered internal threads are scaled proportionally in both axial and radial dimensions to achieve matching with the pitch and diameter dimensions of the target tapered thread. In the commercial finite element software (Abaqus), the scaled original mesh entities of single-pitch tapered external thread and single-pitch tapered internal thread are arrayed along the axial direction, with the array spacing being the pitch. The number of arrays is determined by dividing the actual thread length by the pitch and rounding up, thus obtaining the external thread model array and the internal thread model array respectively. By merging the external thread model array and the internal thread model array through common node operation, the original mesh of the overall external thread structure and the original mesh of the overall internal thread structure are obtained. Based on the profile geometric feature expressions of single-pitch tapered external threads and single-pitch tapered internal threads, the node coordinates of the original meshes of the external thread and internal thread integral structures are adjusted by linear interpolation algorithm using commercial finite element software (Abaqus) and open-source programming language (Python). This ensures that the original meshes of the external thread and internal thread integral structures accurately match the geometry of the target tapered thread, thus obtaining the final hexahedral mesh model.

[0022] To further elaborate on the above steps, each step will be explained in detail below: In the commercial finite element software (Hypermesh), annular solids with inner and outer diameters representing the inner and outer diameters of the threaded region are drawn. Mesh nodes are evenly distributed on the annular solids to generate a two-dimensional (2D) mesh that makes the central non-transition region radially symmetrical. This mesh is then stretched axially into a three-dimensional (3D) mesh, i.e., a hexahedral mesh. The obtained 3D mesh serves as the original mesh for the threaded region in the original mesh of the single-pitch tapered external thread structure. The obtained original mesh for the threaded region is shown below. Figure 2 As shown; In Hypermesh, a 2D transition mesh of a certain scale is drawn along the axial direction, then rotated and stretched into a 3D mesh. A transition mesh of a certain scale is also drawn along the radial direction, making the central non-transition region a radially symmetrical 2D mesh, which is then stretched along the axial direction into a 3D mesh, i.e., a hexahedral mesh. The number of stretched meshes meets the transition requirements from the threaded mesh region to the non-threaded mesh region. This serves as the original mesh for the non-threaded region in the original mesh of the single-pitch tapered external thread structure. The resulting original mesh for the threaded region is as follows: Figure 3 As shown

[0023] Align the inner diameter nodes of the original threaded mesh entity with the outer diameter nodes of the non-threaded mesh entity, and merge the two entities using the Hypermesh common node operation to form a tapered internal thread single-pitch mesh mold. The result is as follows. Figure 4 As shown; Export the merged mesh entity as an .inp file as the original mesh for the single-pitch tapered external thread structure; The characteristics of the tapered external thread connection structure of the piercing system of the heavy extruder are determined as follows: taper is 10°, pitch is 6mm, maximum diameter of tapered thread is 520mm, length of tapered thread section is 485mm, and tooth angle is 55°.

[0024] By combining commercial finite element software (Abaqus) and open-source programming language (Python), the node information in the inp file of the original mesh model of a single-pitch tapered thread is scaled and adjusted. The axial coordinates of the original mesh nodes are changed proportionally to the axial dimension according to the pitch size, so that the height of the original mesh model is equal to one pitch. By combining the commercial finite element software (Abaqus) and the open-source programming language (Python), the node information in the original mesh model in the .inp file of the single-pitch tapered external thread was adjusted so that the coordinates of the original mesh portion of the external thread segment were changed proportionally to the radial dimension to meet the outer diameter dimension requirements of the thread area in the external thread structure. The coordinates of each intermediate node were set according to the linear interpolation of the inner and outer diameter dimensions. The adjusted mesh of the original mesh model inp file of the single-pitch tapered external thread was then imported into the commercial finite element software (Abaqus). The imported model was arrayed using the commercial finite element software (Abaqus). The array spacing was equal to the thread pitch. The length after arraying met the requirements for the external thread segment. Two thread transition segments with a length of half a thread pitch were added. The common nodes of the model array were merged in the assembly state, as shown below. Figure 5 As shown; Export the model as an inp file as the original mesh for the overall external thread structure; Construct the geometric characteristic expression of the tapered external thread profile. Based on the radial distance dimension of the tapered thread profile within one pitch, divide the thread profile according to the pitch. Project to 0-2 In a cylindrical coordinate system, the radial coordinate of the external thread section and The expression is: , In the formula, The radial coordinates of the cross-section of a single-pitch tapered external thread. The maximum outer diameter of the target tapered external thread is the single-pitch tapered external thread. The pitch of the target tapered thread for a single-pitch tapered external thread. This is the original triangle height of the tooth profile angle of a single-pitch tapered external thread, used to define the profile height of the single-pitch tapered external thread. The taper of a single-pitch tapered external thread. This is the axial distance from the profile of a single-pitch tapered external thread to the major diameter of the external thread. The tooth radius of a single-pitch tapered external thread. For the angle parameters in the cylindrical coordinate system, , , and These are all boundary parameters of the profile of a single-pitch tapered external thread, used to distinguish between the root fillet, the working surface of the thread, and the tip of the thread.

[0025] in, , , , , .

[0026] Tapered external thread structure thread profile as shown Figure 6 As shown.

[0027] Based on the original model mesh node coordinates and the geometric characteristic expression of the tapered external thread profile, the node coordinates of the original mesh of the overall external thread structure are read. Combining commercial finite element software (Abaqus) and the open-source programming language (Python), linear interpolation is used to modify and determine the node coordinates of the overall refined tapered internal thread mesh. Figure 7 As shown; Export the overall refined thread mesh .inp model file of the tapered external thread structure. The overall refined thread mesh model of the tapered external thread structure is as follows: Figure 8 As shown; The flowchart of the modular fine hexahedral mesh model construction of the tapered external thread connection structure proposed in this invention is as follows: Figure 9 As shown In Hypermesh, two annular solids, one with inner and one with outer diameters, are drawn to represent the inner and outer diameters of the threaded region, respectively. Mesh nodes are evenly distributed on these annular solids to generate a 2D mesh. This mesh is then stretched axially to create a 3D mesh. The resulting 3D mesh serves as the original mesh for the threaded region within the original mesh of the single-pitch tapered internal thread structure. The resulting original mesh for the threaded region is shown below. Figure 10 As shown; In Hypermesh, a 2D transition mesh of a certain scale is drawn along the axial direction and then rotated and stretched into a 3D mesh. A transition mesh of a certain scale is also drawn along the radial direction, making the central non-transition region a radially symmetrical 2D mesh, which is then stretched into a 3D mesh along the axial direction. The number of stretched meshes meets the transition requirements from the threaded mesh region to the non-threaded mesh region. This serves as the original mesh for the non-threaded region in the original mesh of the single-pitch tapered internal thread structure. The resulting original mesh for the threaded region is shown below. Figure 11 As shown Align the inner diameter nodes of the original threaded mesh entity with the outer diameter nodes of the non-threaded mesh entity, and merge the two entities using the hypermesh common node operation to form a tapered internal thread single-pitch mesh mold, as shown below. Figure 12 As shown; The characteristics of the tapered internal thread connection structure of the piercing system of the heavy extruder are determined. The characteristics of the tapered internal thread connection structure in the example are the same as those of the external thread, with a taper of 10°, a pitch of 6mm, a maximum inner diameter of 520mm for the tapered internal thread, a tapered thread section length of 485mm, and a tooth angle of 55°.

[0028] By combining commercial finite element software (Abaqus) and open-source programming language (Python), the node information in the inp file of the original mesh model of a single-pitch tapered internal thread is adjusted. The axial coordinates of the original mesh nodes are changed proportionally to the axial dimension according to the pitch size, so that the height of the original mesh model is equal to one pitch. By combining commercial finite element software (Abaqus) and open-source programming language (Python), the node information in the inp file of the original mesh model of the single-pitch tapered internal thread is adjusted so that the coordinates of the original mesh part of the internal thread segment are changed proportionally to the radial dimension to meet the requirements of the inner and outer diameter dimensions of the internal thread structure within the thread area. The coordinates of each intermediate node are set according to the linear interpolation of the inner and outer diameter dimensions. Import the adjusted original mesh model inp file of the single-pitch tapered internal thread into the commercial finite element software (Abaqus). The imported model was arrayed using the commercial finite element software (Abaqus). The array spacing was equal to the thread pitch. The length after arraying met the requirements for the external thread segment length. Two thread transition segments with a length of half a thread pitch were added, such as... Figure 13 As shown; Array of shared-node merging models: Export the model as an inp file as the original mesh for the overall internal thread structure; Construct the geometric characteristic expression of the tapered internal thread profile. Based on the radial distance dimension of the tapered thread profile within one pitch, divide the thread profile according to the pitch. Project to 0-2 In a cylindrical coordinate system, the radial coordinate of the external thread section and The expression is: , In the formula, The radial coordinates of the cross-section of a single-pitch tapered internal thread. The maximum inner diameter of the target tapered thread. The minimum inner diameter of the target tapered thread for a single-pitch tapered internal thread. The pitch of the target tapered thread for a single-pitch tapered internal thread. The height of the original triangle representing the tooth profile angle of a single-pitch tapered internal thread. The taper of a single-pitch tapered internal thread. This is the axial distance from the profile of a single-pitch tapered internal thread to the major diameter of the internal thread. The tooth profile radius of a single-pitch tapered internal thread. For the angle parameters in the cylindrical coordinate system, , , and These are all boundary parameters of the profile of a single-pitch tapered internal thread, used to distinguish between the root fillet, the working surface of the thread, and the tip of the thread.

[0029] in, , , , , , .

[0030] Tapered external thread structure thread profile as shown Figure 14 As shown.

[0031] Based on the original model mesh node coordinates and the geometric characteristic expression of the conical internal thread profile, the node coordinates of the original mesh of the overall internal thread structure are read. Combining commercial finite element software (Abaqus) and the open-source programming language (Python), linear interpolation is used to modify and determine the node coordinates of the overall refined conical internal thread mesh. Figure 15 As shown Export the overall refined thread mesh (.inp) model file to obtain the tapered internal thread structure, such as... Figure 16 As shown; The flowchart of the modular fine hexahedral mesh model construction of the tapered internal thread connection structure proposed in this invention is as follows: Figure 17 As shown Based on the established refined thread mesh of the conical internal and external thread structure and the assembly relationship of the geometric model, a modular hexahedral mesh model of the conical thread connection structure of the piercing system of a heavy-duty extruder is constructed, resulting in an analytical model as follows: Figure 18 As shown; Based on this method, modular construction of multi-connection models of tapered thread connection structures in the piercing system of heavy-duty extruders can be achieved, such as... Figure 19 As shown.

[0032] The above description is merely an example of one embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

[0033] The embodiments of this invention use Hypermesh software as a pre-processing mesh drawing tool and Abaqus software and its Python interface as a parametric programming and model operation environment. However, the core idea of ​​the method described in this invention is not limited to a specific software platform and can also be implemented in other CAE software systems with similar functions.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for constructing a modular hexahedral mesh model of an extruder tapered thread structure, characterized in that, Includes the following steps: Obtain the characteristic parameters of the target tapered thread connection structure; Based on the feature parameters, cylindrical ring meshes of different densities are drawn as the original meshes of the threaded region and cylindrical transition meshes are drawn as the original meshes of the non-threaded region. The original mesh entities of single-pitch tapered external threads and single-pitch tapered internal threads are obtained by merging common nodes. The original mesh entities of single-pitch tapered external threads and single-pitch tapered internal threads are scaled proportionally in both axial and radial dimensions to achieve matching with the pitch and radial dimensions of the target tapered thread. The scaled original mesh entities of the single-pitch tapered external thread and the single-pitch tapered internal thread are arrayed along the axial direction, and the common node merging operation is performed on all the arrayed mesh entities to obtain the original mesh of the overall external thread structure and the original mesh of the overall internal thread structure, respectively. Based on the aforementioned feature parameters, geometric feature expressions for the profiles of single-pitch tapered external threads and single-pitch tapered internal threads are constructed. Then, using a linear interpolation algorithm, the corresponding node coordinates in the original meshes of the overall external thread structure and the overall internal thread structure are adjusted to ensure that the original meshes of the overall external thread structure and the overall internal thread structure accurately match the geometry of the target tapered thread, thereby obtaining the final hexahedral mesh model.

2. The modular hexahedral mesh model construction method for the tapered thread structure of an extruder according to claim 1, characterized in that, The steps of drawing cylindrical ring meshes of different densities as the original mesh of the thread region include: first drawing two circles with inner and outer diameters to represent the ring surface entities of the inner and outer diameters of the thread region respectively; setting mesh nodes in four equal parts on the ring surface entities to make the central non-transition region a radially symmetrical two-dimensional mesh; stretching the two-dimensional mesh along the axial direction into a hexahedral mesh; and using the obtained hexahedral mesh as the original mesh of the thread region.

3. The modular hexahedral mesh model construction method for the tapered thread structure of an extruder according to claim 1, characterized in that, The steps of drawing cylindrical transition meshes of different densities as the original mesh of the non-threaded region include: drawing a certain proportion of two-dimensional transition meshes along the axial direction, rotating and stretching them into hexahedral meshes, and then drawing a certain proportion of transition meshes along the radial direction so that the central non-transition region is a radially symmetrical two-dimensional mesh, stretching it along the axial direction into a hexahedral mesh, and the number of stretched meshes meeting the transition requirements from the threaded mesh region to the non-threaded mesh region, thus serving as the original mesh of the non-threaded region.

4. The modular hexahedral mesh model construction method for the tapered thread structure of an extruder according to claim 1, characterized in that, The original mesh entity of the single-pitch tapered external thread is the original mesh entity used to generate a tapered external thread hexahedral mesh structure by changing the nodes under a single pitch size; the original mesh entity of the single-pitch tapered internal thread is the original mesh entity used to generate a tapered internal thread hexahedral mesh structure by changing the nodes under a single pitch size.

5. The modular hexahedral mesh model construction method for the tapered thread structure of an extruder according to claim 1, characterized in that, The proportional axial scaling is based on the pitch adjustment of the target tapered thread, adjusting the axial coordinates of the original mesh entities of the single-pitch tapered external thread and the single-pitch tapered internal thread. The proportional radial scaling is based on the maximum and minimum diameters of the target tapered thread, adjusting the radial coordinates of the original mesh entities of the single-pitch tapered external thread and the single-pitch tapered internal thread, to achieve pitch and diameter matching between the original mesh entities of the single-pitch tapered external thread and the single-pitch tapered internal thread and the target tapered thread.

6. The modular hexahedral mesh model construction method for the tapered thread structure of an extruder according to claim 1, characterized in that, The scaled original mesh entities of the single-pitch tapered external thread and the original mesh entities of the single-pitch tapered internal thread are arrayed and then a thread transition section with a length of half a pitch is added to ensure mesh continuity.

7. The modular hexahedral mesh model construction method for the tapered thread structure of an extruder according to claim 1, characterized in that, The geometric characteristic expression of the profile of the single-pitch tapered external thread is based on the radial distance dimension of the profile of the single-pitch tapered external thread within one pitch, expressed as a percentage of the pitch. Project to 0-2 In a cylindrical coordinate system, the radial coordinates of the cross-section used to calculate a single-pitch tapered external thread. With angle The relationship is determined by the following formula: ， in, , , , , ; In the formula, The radial coordinates of the cross-section of a single-pitch tapered external thread. The maximum outer diameter of the target tapered external thread is the single-pitch tapered external thread. The pitch of the target tapered thread for a single-pitch tapered external thread. This is the original triangle height of the tooth profile angle of a single-pitch tapered external thread, used to define the profile height of the single-pitch tapered external thread. The taper of a single-pitch tapered external thread. This is the axial distance from the profile of a single-pitch tapered external thread to the major diameter of the external thread. The tooth radius of a single-pitch tapered external thread. For the angle parameters in the cylindrical coordinate system, , , and These are all boundary parameters of the profile of a single-pitch tapered external thread, used to distinguish between the root fillet, the working surface of the thread, and the tip of the thread.

8. The modular hexahedral mesh model construction method for the tapered thread structure of an extruder according to claim 1, characterized in that, The geometric characteristic expression of the profile of the single-pitch tapered internal thread is based on the radial distance dimension of the profile of the single-pitch tapered internal thread within one pitch, and is expressed as follows: Project to 0-2 In cylindrical coordinate system, the radial coordinate of the cross section of a single-pitch tapered internal thread With angle The relationship is determined by the following formula: ， in, , , , , , ; In the formula, The radial coordinates of the cross-section of a single-pitch tapered internal thread. The maximum inner diameter of the target tapered thread. The minimum inner diameter of the target tapered thread for a single-pitch tapered internal thread. The pitch of the target tapered thread for a single-pitch tapered internal thread. The height of the original triangle representing the tooth profile angle of a single-pitch tapered internal thread. The taper of a single-pitch tapered internal thread. This is the axial distance from the profile of a single-pitch tapered internal thread to the major diameter of the internal thread. The tooth radius of a single-pitch tapered internal thread. For the angle parameters in the cylindrical coordinate system, , , and These are all boundary parameters of the profile of a single-pitch tapered internal thread, used to distinguish between the root fillet, the working surface of the thread, and the tip of the thread.

9. The method for constructing a modular hexahedral mesh model of the tapered thread structure of an extruder according to claim 1, characterized in that, The steps of adjusting node coordinates using the linear interpolation algorithm include: obtaining the node coordinates of the original mesh of the overall external thread structure or the original mesh of the overall internal thread structure; calculating the new coordinates of each node through linear interpolation based on the corresponding profile geometric feature expression; and updating the original mesh of the overall external thread structure or the original mesh of the overall internal thread structure to achieve accurate matching of geometric shapes.

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