Implementation method of bolt finite element mesh 3-1 transition layer

Abstract

The invention discloses an implementation method of a bolt finite element mesh 3-1 transition layer. The arrangement mode and position information of the whole transition layer are controlled by using three parameters of a base point coordinate, a generation plane and a generation direction. In combination with dot matrix generation, special point abandoning and node re-numbering methods, all possible arrangement and position conditions of 3-1 transition layers involved in bolt precision finite elements are covered through a reasonable mode with few parameters. According to the method, the bolt finite element 3-1 transition layer mesh meeting the requirements can be automatically generated at the base point position, a practitioner in the bolt precision finite element industry is helped to rapidly generate the bolt mesh of a plurality of transition layers, and the problem that manual drawing of the bolt precision finite element transition area is too tedious and complex is solved.

Description

Technical Field

[0001] This invention belongs to the field of precision finite element technology for bolts, specifically involving the design of a method for implementing a 3-1 transition layer of a bolt finite element mesh. Background Technology

[0002] The 3-1 transition layer in finite element meshing is a special method in the finite element method (FEM) field, used to transition dense meshes to sparse meshes. In the field of precision finite element subdivision for bolts, to ensure a sufficiently dense mesh at the threads while reducing the number of meshes in non-interesting regions, it is typically necessary to transition the dense mesh at the threads inwards to a sparse mesh in the bolt core. Compared to ordinary finite element methods, precision finite element methods for bolts often involve hundreds of thousands to millions of dense meshes, making manual operation extremely tedious. Therefore, a technique for automatically implementing the 3-1 transition layer is needed. Summary of the Invention

[0003] The purpose of this invention is to solve the problem that manually drawing the precision finite element transition zone of bolts is too cumbersome and complicated. It provides a method for realizing the 3-1 transition layer of the finite element mesh of bolts, which solves the dependence on manual operation in the prior art.

[0004] The technical solution of the present invention is: a method for implementing a 3-1 transition layer of a bolt finite element mesh, comprising the following steps: S1. Obtain the physical parameters of the bolt and the Cartesian coordinates of the base point.

[0005] S2. Set the number of cycles according to the physical parameters of the bolt, convert the Cartesian coordinates of the base point to cylindrical coordinates, and generate a 3*3 dot matrix.

[0006] S3. Select the nodes in the 3*3 dot matrix and renumber them.

[0007] S4. Determine if the last loop has been entered. If yes, proceed to step S6; otherwise, proceed to step S5.

[0008] S5. Generate 4 C2D4 meshes, increment the loop count by 1, and return to step S4.

[0009] S6. Redirect the renumbered nodes.

[0010] S7. Generate a columnar C3D8 transition mesh based on the C2D4 mesh.

[0011] S8. Determine whether the r-axis direction of the generated dot matrix is ​​the positive r-axis direction. If yes, proceed to step S9; otherwise, proceed to step S10.

[0012] S9. Keep the θ and Z coordinates of the base point unchanged, and shift the r coordinate by +2Δr, then proceed to step S11.

[0013] S10. Keep the θ and Z coordinates of the base point unchanged, and shift the r coordinate by -2Δr. Proceed to step S11.

[0014] S11. Convert the cylindrical coordinates of the base point to Cartesian coordinates and output a 3-1 transition layer mesh in C3D8 format.

[0015] Furthermore, the physical parameters of the bolt in step S1 include the diameter of the current transition layer mesh, the number of layers per pitch, the number of circumferential layers, and the orientation and plane of the mesh to be generated.

[0016] Furthermore, in step S2, if the plane containing the mesh to be generated is the Z=C plane, then the number of iterations is set to i=2π / 3Δθ, where C is an arbitrary constant; if the plane containing the mesh to be generated is the θ=0 plane, then the number of iterations is set to i=2π / Δθ.

[0017] Furthermore, the specific method for generating the 3*3 dot matrix in step S2 is as follows: If the plane containing the mesh to be generated is the Z=C plane with the direction of the negative r-axis, then the base point is taken as the upper left corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the Z=C plane, i 3*3 lattices with intervals of -Δr and +Δθ between the r-axis and θ-axis are generated, and numbered sequentially from 9i-8 to 9i.

[0018] If the plane containing the mesh to be generated is the Z=C plane with the positive direction of the r-axis, then the base point is taken as the lower left corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the Z=C plane, i 3*3 lattices with intervals of +Δr and +Δθ between the r-axis and θ-axis are generated, and numbered sequentially from 9i-8 to 9i.

[0019] If the plane containing the mesh to be generated is the θ=0 plane with the negative direction of the r-axis, then the base point is taken as the upper right corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the θ=0 plane, i 3*3 lattices with intervals of -Δr and +ΔZ between the r-axis and Z-axis are generated, and numbered sequentially from 9i-8 to 9i.

[0020] If the plane containing the mesh to be generated is the θ=0 plane with the positive direction of the r-axis, then the base point is taken as the lower right corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the θ=0 plane, i 3*3 lattices with intervals of +Δr and +ΔZ between the r-axis and Z-axis are generated, and numbered sequentially from 9i-8 to 9i.

[0021] Further, in step S3, nodes numbered [9i-8, 9i-6, 9i-5, 9i-4, 9i-2, 9i-1] in the 3*3 matrix are selected and renumbered sequentially from 6i-5 to 6i.

[0022] Furthermore, in step S5, if the plane where the mesh to be generated is located is the Z=C plane, then in the cylindrical coordinate plane of Z=C, four C2D4 meshes are generated in each cycle, with node combinations of [6i-5,6i-4,6i-2,6i-3], [6i-3,6i-2,6i,6i-1], [6i-4,6i-2,6i,6i+2] and [6i-1,6i,6i+2,6i+1].

[0023] If the plane containing the mesh to be generated is the θ=0 plane, then in the cylindrical coordinate plane of θ=0, each cycle generates 4 C2D4 meshes with node combinations of [6i-5,6i-4,6i-2,6i-3], [6i-3,6i-2,6i,6i-1], [6i-4,6i-2,6i,6i+2] and [6i-1,6i,6i+2,6i+1].

[0024] Further, in step S6, node number 6i+1 is redirected to 1, and node number 6i+2 is redirected to 2.

[0025] Furthermore, in step S7, if the plane in which the mesh to be generated is located is the Z=C plane, then the C2D4 mesh in the Z=C cylindrical coordinate plane is stretched in the positive Z-axis direction to generate a cylindrical C3D8 transition mesh.

[0026] If the plane containing the mesh to be generated is the θ=0 plane, then rotate the C2D4 mesh in the θ=0 cylindrical coordinate plane in the positive direction of the θ axis to generate a ring-shaped C3D8 transition mesh, and then stretch it in the positive direction of the Z axis to generate a cylindrical C3D8 transition mesh.

[0027] The beneficial effects of this invention are: it can automatically generate a 3-1 transition layer mesh for bolts at the base point location, helping practitioners in the bolt precision finite element industry to quickly generate bolt meshes with multiple transition layers. For users, after drawing the mesh of the outer threaded component, specifying the base point location for the transition layer and the physical parameters of the bolt, a single-layer 3-1 transition mesh can be generated. Repeating this operation can quickly generate a complete multi-layer transition mesh. After simple processing, a complete bolt model can be quickly obtained, and the arrangement of the transition layers can be freely modified according to the user's wishes. Attached Figure Description

[0028] Figure 1 The diagram shown is a flowchart of a method for implementing a transition layer of a bolt finite element mesh 3-1 according to an embodiment of the present invention.

[0029] Figure 2 The diagram shown is a schematic diagram of the 3-1 transition layer between the θ=0 plane and the Z=C plane provided in an embodiment of the present invention.

[0030] Figure 3 The diagram shown is a schematic diagram of node renumbering provided in an embodiment of the present invention.

[0031] Figure 4 The figure shown is a schematic diagram of a local precision finite element model of a bolt with a 5-layer 3-1 transition layer provided in an embodiment of the present invention. Detailed Implementation

[0032] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the invention, and are not intended to limit the scope of the invention.

[0033] This invention provides a method for implementing a transition layer of a bolt finite element mesh 3-1, such as... Figure 1 As shown, it includes the following steps S1~S11: S1. Obtain the physical parameters of the bolt and the Cartesian coordinates of the base point.

[0034] In this embodiment of the invention, the physical parameters of the bolt include the diameter of the current transition layer mesh, the number of layers per pitch, the number of circumferential layers, and the orientation and plane of the mesh to be generated. The physical parameters of the bolt can be used to calculate the size information of the smallest elements, such as Δθ, Δr, and ΔZ.

[0035] In this embodiment of the invention, the θ axis, r axis, and Z axis are the three axes of the cylindrical coordinate system, where r represents the radial distance from the point to the Z axis, θ represents the azimuth angle of the point, Z represents the height of the point, and Δθ, Δr, and ΔZ refer to the coordinate difference between two adjacent points.

[0036] S2. Set the number of cycles according to the physical parameters of the bolt, convert the Cartesian coordinates of the base point to cylindrical coordinates, and generate a 3*3 dot matrix.

[0037] In this embodiment of the invention, if the plane containing the mesh to be generated is the Z=C plane, the number of iterations is set to i=2π / 3Δθ, where C is an arbitrary constant. If the plane containing the mesh to be generated is the θ=0 plane, the number of iterations is set to i=2π / Δθ. Different planar meshes are as follows... Figure 2 As shown.

[0038] In this embodiment of the invention, the specific method for generating a 3*3 dot matrix is ​​as follows: If the plane containing the mesh to be generated is the Z=C plane with the direction of the negative r-axis, then the base point is taken as the upper left corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the Z=C plane, i 3*3 lattices with intervals of -Δr and +Δθ between the r-axis and θ-axis are generated, and numbered sequentially from 9i-8 to 9i.

[0039] If the plane containing the mesh to be generated is the Z=C plane with the positive direction of the r-axis, then the base point is taken as the lower left corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the Z=C plane, i 3*3 lattices with intervals of +Δr and +Δθ between the r-axis and θ-axis are generated, and numbered sequentially from 9i-8 to 9i.

[0040] If the plane containing the mesh to be generated is the θ=0 plane with the negative direction of the r-axis, then the base point is taken as the upper right corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the θ=0 plane, i 3*3 lattices with intervals of -Δr and +ΔZ between the r-axis and Z-axis are generated, and numbered sequentially from 9i-8 to 9i.

[0041] If the plane containing the mesh to be generated is the θ=0 plane with the positive direction of the r-axis, then the base point is taken as the lower right corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the θ=0 plane, i 3*3 lattices with intervals of +Δr and +ΔZ between the r-axis and Z-axis are generated, and numbered sequentially from 9i-8 to 9i.

[0042] S3. Select the nodes in the 3*3 dot matrix and renumber them.

[0043] In this embodiment of the invention, nodes numbered [9i-8, 9i-6, 9i-5, 9i-4, 9i-2, 9i-1] in a 3*3 matrix are selected and sequentially renumbered from 6i-5 to 6i. For example... Figure 3 As shown, Figure 3 (a) represents the initial node numbering in the 3x3 dot matrix. Figure 3 (b) represents the selected node. Figure 3 (c) The result of renumbering the nodes.

[0044] S4. Determine if the last loop has been entered. If yes, proceed to step S6; otherwise, proceed to step S5.

[0045] S5. Generate 4 C2D4 meshes, increment the loop count by 1, and return to step S4.

[0046] like Figure 3 As shown in (c), if the plane where the mesh to be generated is the Z=C plane, then in the cylindrical coordinate plane of Z=C, each cycle generates 4 C2D4 meshes with node combinations of [6i-5,6i-4,6i-2,6i-3], [6i-3,6i-2,6i,6i-1], [6i-4,6i-2,6i,6i+2] and [6i-1,6i,6i+2,6i+1].

[0047] If the plane containing the mesh to be generated is the θ=0 plane, then in the cylindrical coordinate plane of θ=0, each cycle generates 4 C2D4 meshes with node combinations of [6i-5,6i-4,6i-2,6i-3], [6i-3,6i-2,6i,6i-1], [6i-4,6i-2,6i,6i+2] and [6i-1,6i,6i+2,6i+1].

[0048] S6. Redirect the renumbered nodes.

[0049] In this embodiment of the invention, since the maximum value of the node number is 6i, the numbers 6i+1 and 6i+2 generated in the last step will exceed the matrix dimension. In order to ensure that the nodes are closed in a circular manner, the node number 6i+1 is redirected to 1 and the node number 6i+2 is redirected to 2.

[0050] S7. Generate a columnar C3D8 transition mesh based on the C2D4 mesh.

[0051] In this embodiment of the invention, if the plane in which the mesh to be generated is the Z=C plane, then the C2D4 mesh in the Z=C cylindrical coordinate plane is stretched in the positive Z-axis direction to generate a cylindrical C3D8 transition mesh.

[0052] If the plane containing the mesh to be generated is the θ=0 plane, then rotate the C2D4 mesh in the θ=0 cylindrical coordinate plane in the positive direction of the θ axis to generate a ring-shaped C3D8 transition mesh, and then stretch it in the positive direction of the Z axis to generate a cylindrical C3D8 transition mesh.

[0053] S8. Determine whether the r-axis direction of the generated dot matrix is ​​the positive r-axis direction. If yes, proceed to step S9; otherwise, proceed to step S10.

[0054] S9. Keep the θ and Z coordinates of the base point unchanged, and shift the r coordinate by +2Δr, then proceed to step S11.

[0055] S10. Keep the θ and Z coordinates of the base point unchanged, and shift the r coordinate by -2Δr. Proceed to step S11.

[0056] S11. Convert the cylindrical coordinates of the base point to Cartesian coordinates and output a 3-1 transition layer mesh in C3D8 format.

[0057] In this embodiment of the invention, C2D4 refers to a 2D 4-node mesh, and C3D8 refers to a 3D hexahedral 8-node mesh.

[0058] This invention uses a method of dot matrix generation, special point discarding, and node address renumbering to generate four different shaped meshes within a single loop of the transition layer. The operation steps are as follows: generate a 3*3 dot matrix and number it, discard nodes without corresponding mesh nodes, and renumber the remaining points in the dot matrix. Finally, through four numbering pointer groups [6i-5,6i-4,6i-2,6i-3], [6i-3,6i-2,6i,6i-1], [6i-4,6i-2,6i,6i+2], and [6i-1,6i,6i+2,6i+1], the four different shaped meshes within a single loop are obtained.

[0059] This invention uses three parameters—base point coordinates, generation plane, and generation direction—to control the arrangement and position information of the entire transition layer. By using fewer and more reasonable parameters, it covers all possible arrangements and positions of the 3-1 transition layer involved in bolt precision finite element analysis.

[0060] In this embodiment of the invention, the diameter of the current transition layer, the number of layers per pitch, and the number of circumferential layers are used to calculate Δr, Δθ, and ΔZ to control the dimensional information of the transition layer. No bolt contour information or any mechanical parameters are required; all possible dimensions of the 3-1 transition layer in the complete model can be determined using only these three parameters.

[0061] This embodiment of the invention will output updated base point information for convenient use in subsequent operations. If multiple transition layers need to be generated, simply re-enter the output base point information and the physical parameters of the bolts into the program; no manual calculation is required. Figure 4 The image shows a local bolt model (excluding the threaded region mesh) generated by the implementation method of the bolt finite element mesh 3-1 transition layer provided in this embodiment of the invention, which is used 5 times in a cycle.

[0062] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for implementing a 3-1 transition layer of a bolt finite element mesh, characterized in that, Includes the following steps: S1. Obtain the physical parameters of the bolt and the Cartesian coordinates of the base point; S2. Set the number of cycles according to the physical parameters of the bolt, convert the Cartesian coordinates of the base point to cylindrical coordinates, and generate a 3*3 matrix; S3. Select the nodes in the 3*3 dot matrix and renumber them; S4. Determine whether to enter the last loop. If yes, proceed to step S6; otherwise, proceed to step S5. S5. Generate 4 C2D4 meshes, increment the loop count by 1, and return to step S4; S6. Redirect the renumbered nodes; S7. Generate a columnar C3D8 transition mesh based on the C2D4 mesh; S8. Determine whether the r-axis direction of the generated dot matrix is ​​the positive r-axis direction. If yes, proceed to step S9; otherwise, proceed to step S10. S9. Keep the θ and Z coordinates of the base point unchanged, and shift the r coordinate by +2Δr. Proceed to step S11. S10. Keep the θ and Z coordinates of the base point unchanged, and shift the r coordinate by -2Δr. Proceed to step S11. S11. Convert the cylindrical coordinates of the base point to Cartesian coordinates and output a 3-1 transition layer mesh in C3D8 format.

2. The method for implementing the bolt finite element mesh 3-1 transition layer according to claim 1, characterized in that, The physical parameters of the bolt in step S1 include the diameter of the current transition layer mesh, the number of layers per pitch, the number of circumferential layers, and the orientation and plane of the mesh to be generated.

3. The method for implementing the transition layer of the bolt finite element mesh 3-1 according to claim 2, characterized in that, In step S2, if the plane containing the mesh to be generated is the Z=C plane, then the number of iterations is set to i=2π / 3Δθ, where C is an arbitrary constant. If the plane containing the mesh to be generated is the θ=0 plane, then the number of iterations is set to i=2π / Δθ.

4. The method for implementing the bolt finite element mesh 3-1 transition layer according to claim 3, characterized in that, The specific method for generating the 3*3 dot matrix in step S2 is as follows: If the plane containing the mesh to be generated is the Z=C plane with the direction of the negative r-axis, then the base point is taken as the upper left corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the Z=C plane, i 3*3 lattices with intervals of -Δr and +Δθ between the r-axis and θ-axis are generated, and numbered sequentially from 9i-8 to 9i. If the plane containing the mesh to be generated is the Z=C plane with the positive direction of the r-axis, then the base point is taken as the lower left corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the Z=C plane, i 3*3 lattices with intervals of +Δr and +Δθ between the r-axis and the θ-axis are generated, and numbered sequentially from 9i-8 to 9i. If the plane containing the mesh to be generated is the θ=0 plane and the direction is the negative direction of the r-axis, then the base point is taken as the upper right corner of the point matrix to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the θ=0 plane, i 3*3 point matrices with intervals of -Δr and +ΔZ between the r-axis and Z-axis are generated, and numbered sequentially from 9i-8 to 9i. If the plane containing the mesh to be generated is the θ=0 plane with the positive direction of the r-axis, then the base point is taken as the lower right corner of the lattice to be generated, and the Cartesian coordinates of the base point are converted to cylindrical coordinates. On the θ=0 plane, i 3*3 lattices with intervals of +Δr and +ΔZ between the r-axis and Z-axis are generated, and numbered sequentially from 9i-8 to 9i.

5. The method for implementing the bolt finite element mesh 3-1 transition layer according to claim 4, characterized in that, In step S3, nodes numbered [9i-8, 9i-6, 9i-5, 9i-4, 9i-2, 9i-1] in the 3*3 matrix are selected and renumbered sequentially from 6i-5 to 6i.

6. The method for implementing the bolt finite element mesh 3-1 transition layer according to claim 5, characterized in that, In step S5, if the plane where the mesh to be generated is located is the Z=C plane, then in the cylindrical coordinate plane of Z=C, four C2D4 meshes are generated in each cycle, with node combinations of [6i-5,6i-4,6i-2,6i-3], [6i-3,6i-2,6i,6i-1], [6i-4,6i-2,6i,6i+2] and [6i-1,6i,6i+2,6i+1], respectively. If the plane containing the mesh to be generated is the θ=0 plane, then in the cylindrical coordinate plane of θ=0, each cycle generates 4 C2D4 meshes with node combinations of [6i-5,6i-4,6i-2,6i-3], [6i-3,6i-2,6i,6i-1], [6i-4,6i-2,6i,6i+2] and [6i-1,6i,6i+2,6i+1].

7. The method for implementing the bolt finite element mesh 3-1 transition layer according to claim 6, characterized in that, In step S6, node number 6i+1 is redirected to 1, and node number 6i+2 is redirected to 2.

8. The method for implementing the bolt finite element mesh 3-1 transition layer according to claim 2, characterized in that, If the plane in which the mesh to be generated is located is the Z=C plane in step S7, then the C2D4 mesh in the Z=C cylindrical coordinate plane is stretched in the positive direction of the Z-axis to generate a cylindrical C3D8 transition mesh. If the plane containing the mesh to be generated is the θ=0 plane, then rotate the C2D4 mesh in the θ=0 cylindrical coordinate plane in the positive direction of the θ axis to generate a ring-shaped C3D8 transition mesh, and then stretch it in the positive direction of the Z axis to generate a cylindrical C3D8 transition mesh.

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