Method for generating precise finite element model of multi-thread multi-thread thread profile
By constructing the profile equation and node offset operation of multi-line multi-turn threads, a precise finite element model of multi-line multi-turn threads was generated, which solved the problem of lack of profile formula in the existing technology, realized efficient and accurate model generation, and laid the foundation for the performance research of multi-line multi-turn threads.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-04-03
AI Technical Summary
The lack of a profile formula for multi-line, multi-turn threads in existing technologies makes it impossible to generate precise finite element models, thus limiting the research on the performance of multi-line, multi-turn threads.
By constructing the profile equation of a multi-line, multi-turn thread, performing a Cartesian coordinate to cylindrical coordinate transformation, generating a finite element mesh node information matrix, and drawing the thread profile through node offset operations, the multi-line, multi-turn thread profile is generated by iteratively using the ordinary metric thread formula.
It has achieved rapid, efficient, and accurate generation of precise finite element models of multi-line, multi-turn threads such as DTB threads and Tang threads, providing a foundation for subsequent research on stress distribution and anti-loosening performance, and overcoming the technical difficulties of contour mesh drawing.
Smart Images
Figure CN121787183A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of precision finite element technology for bolts, specifically relating to the design of a method for generating a precision finite element model of a multi-line, multi-turn thread profile. Background Technology
[0002] Currently, in the field of precision finite element analysis for bolts, domestic and international research primarily focuses on standard metric threads. Performance studies on special anti-loosening threads with multiple starts or turns, such as Tang threads and Double Thread (DTB) threads, are hampered by limitations in finite element model technology and the lack of relevant research on profile formulas for multi-start, multi-turn threads in domestic and international literature. This lack of profile formulas and theoretical techniques has resulted in a lack of research on precise finite element calculations for multi-start, multi-turn threads. Summary of the Invention
[0003] The purpose of this invention is to solve the problem that existing multi-line multi-turn thread profiles lack corresponding contour formulas, which makes it impossible to generate precise finite element models. A method for generating precise finite element models of multi-line multi-turn thread profiles is proposed.
[0004] The technical solution of this invention is: a method for generating a precise finite element model of a multi-line, multi-turn thread profile, comprising the following steps: S1. Obtain the physical parameters of multiple bolts with multi-line and multi-turn threads and the finite element three-dimensional node information before transformation.
[0005] S2. Construct the profile equation for each thread profile of the multi-line multi-turn thread that needs to be generated.
[0006] S3. Convert the finite element 3D node information before transformation to Cartesian coordinates to cylindrical coordinates within the range of 0~2πrad to obtain the original mesh node cylindrical coordinate data.
[0007] S4. Obtain the initial phase of the bolt physical parameters corresponding to the first thread profile.
[0008] S5. Based on the original grid node cylindrical coordinate data and the current thread profile contour equation, obtain the complete finite element mesh of the current thread profile, and store the finite element mesh node information into a separate node information matrix.
[0009] S6. Determine if there is a next thread profile. If so, obtain the physical parameters of the bolt corresponding to the next thread profile and return to step S5. Otherwise, proceed to step S7.
[0010] S7. For each thread profile, the node information of the node information matrix is compared sequentially. The node information with the smallest r-axis under the same node number is selected. The node number is kept unchanged. All the node information that meets the conditions is stored as a new node information matrix.
[0011] S8. Convert the cylindrical coordinates of the nodes in the new node information matrix to Cartesian coordinates, keep the node numbers unchanged, replace the finite element 3D node information before the transformation, and output the precise finite element model of the multi-line multi-turn thread profile.
[0012] Furthermore, the bolt physical parameters in step S1 include thread type, nominal diameter, pitch, thread direction, initial phase, and the general bearing surface equivalent diameter, number of pitches drawn, pitch division and circumferential division, and number of dense mesh layers.
[0013] Furthermore, the finite element 3D node information before transformation in step S1 is the finite element node information of the untransformed thread with a dense mesh in inp format.
[0014] Furthermore, the profile equation for each thread profile constructed in step S2 is as follows: in , and These are the coordinates along the three axes of a cylindrical coordinate system. This represents the radial distance from the point to the Z-axis. Indicates the azimuth of a point. Indicates the height of the point. Indicates the nominal diameter of the bolt. This represents the tooth height of the original triangle of the thread. Indicates the pitch. Indicates the radius of the tooth base arc. , , and These are the four phase values corresponding to the inflection point of the thread profile.
[0015] Furthermore, step S5 includes the following sub-steps: S51. Select the multi-layer dense mesh nodes in the original mesh node cylindrical coordinate data that require contour offset operation at the external thread.
[0016] S52. Based on the profile equation of the current thread profile, perform a profile offset operation on the outermost dense grid nodes of the external thread.
[0017] S53. Keeping the position of the innermost dense mesh node at the external thread unchanged, perform a positional distribution operation on the multi-layer dense mesh nodes between the innermost and outermost dense meshes at the external thread to obtain the finite element mesh of the thread body.
[0018] S54. Select the multi-layer dense grid nodes in the original grid node cylindrical coordinate data that require transition processing at the spiral tail.
[0019] S55. Based on the current thread profile equation, define an offset coefficient along the Z-axis to perform a profile offset operation on the outermost dense mesh nodes at the thread tail, so that the offset of the nodes gradually decreases to 0 as the Z coordinate value increases.
[0020] S56. Keeping the position of the innermost dense mesh node at the screw tail unchanged, perform a positional distribution operation on the multi-layer dense mesh nodes between the innermost and outermost dense meshes at the screw tail to obtain the finite element mesh of the screw tail part.
[0021] S57. Combine the finite element mesh of the main thread body and the finite element mesh of the thread tail to obtain the complete finite element mesh of the current thread profile.
[0022] S58. Store the finite element mesh node information into a separate node information matrix.
[0023] The beneficial effects of this invention are: (1) This invention uses the common metric thread profile formula to generate multi-line multi-turn threads, which can quickly generate multi-line multi-turn thread profiles such as DTB thread and Tang thread. It can also generate new anti-loosening thread profiles with more complex structures than DTB thread and Tang thread. It is a necessary condition and prerequisite for finite element research on the anti-loosening performance of multi-line multi-turn threads.
[0024] (2) This invention can obtain precise finite element models of DTB threads and Tang threads under various size parameters with high efficiency, high accuracy and large quantity under fully automatic calculation. It breaks through the technical difficulties of the precise finite element theory of bolts and advances the complex contour mesh drawing work from the inability to draw based on the original theory to pure algorithm drawing after inputting the calculation contour formula. It lays the technical foundation for subsequent research and improvement on stress distribution and anti-loosening performance of multi-line multi-turn thread contours. Attached Figure Description
[0025] Figure 1 The diagram shown is a flowchart of a method for generating a precise finite element model of a multi-line, multi-turn thread profile according to an embodiment of the present invention.
[0026] Figure 2 The figure shown is a schematic diagram of a finite element model of a bolt with a dense mesh and untransformed thread provided in an embodiment of the present invention.
[0027] Figure 3 The diagram shown is a complete finite element mesh of the thread profile provided in an embodiment of the present invention.
[0028] Figure 4 The diagram shows a double-line thread and a double-helix thread after the node information matrix is filtered according to an embodiment of the present invention.
[0029] Figure 5 The diagram shown is a complete and precise finite element model of the DTB bolt and the Tang bolt provided in the embodiment of the present invention. Detailed Implementation
[0030] 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.
[0031] This invention provides a method for generating a precise finite element model of a multi-line, multi-twist thread profile, such as... Figure 1 As shown, the process includes the following steps S1 to S8: S1. Obtain the physical parameters of multiple bolts with multi-line and multi-turn threads and the finite element three-dimensional node information before transformation.
[0032] In this embodiment of the invention, the multi-line multi-turn thread includes multiple sets of bolt physical parameters, all of which need to be input during generation. Each set of bolt physical parameters includes thread type, nominal diameter, pitch, thread direction, initial phase, and the common support surface equivalent diameter, number of pitches drawn, pitch division and circumferential division, and number of dense grid layers.
[0033] In this embodiment of the invention, the finite element three-dimensional node information before transformation is the finite element node information of the untransformed thread with a dense mesh in inp format, such as... Figure 2 As shown.
[0034] S2. Construct the profile equation for each thread profile of the multi-line multi-turn thread that needs to be generated.
[0035] In multi-start, multi-turn threads, each thread profile corresponds to a complete set of bolt physical parameters. In this embodiment of the invention, the profile equation for each thread profile is specifically as follows: in , and Let be the coordinates in the three axes (r-axis, θ-axis, and Z-axis) of the cylindrical coordinate system. This represents the radial distance from the point to the Z-axis. Indicates the azimuth of a point. Indicates the height of the point. Indicates the nominal diameter of the bolt. This represents the tooth height of the original triangle of the thread. Indicates the pitch. Indicates the radius of the tooth base arc. , , and The four phase values corresponding to the inflection point of the thread profile are as follows: In the metric thread profile, the phase values are: , , , .
[0036] S3. Convert the finite element 3D node information before transformation to Cartesian coordinates to cylindrical coordinates within the range of 0~2πrad to obtain the original mesh node cylindrical coordinate data.
[0037] S4. Obtain the initial phase of the bolt physical parameters corresponding to the first thread profile.
[0038] S5. Based on the original grid node cylindrical coordinate data and the current thread profile contour equation, obtain the complete finite element mesh of the current thread profile, and store the finite element mesh node information into a separate node information matrix.
[0039] Step S5 includes the following sub-steps S51 to S58: S51. Select the multi-layer dense mesh nodes in the original mesh node cylindrical coordinate data that require contour offset operation at the external thread.
[0040] S52. Based on the profile equation of the current thread profile, perform a profile offset operation on the outermost dense grid nodes of the external thread.
[0041] S53. Keeping the position of the innermost dense mesh node at the external thread unchanged, perform a positional distribution operation on the multi-layer dense mesh nodes between the innermost and outermost dense meshes at the external thread to obtain the finite element mesh of the thread body.
[0042] S54. Select the multi-layer dense grid nodes in the original grid node cylindrical coordinate data that require transition processing at the spiral tail.
[0043] S55. Based on the current thread profile equation, define an offset coefficient along the Z-axis to perform a profile offset operation on the outermost dense mesh nodes at the thread tail, so that the offset of the nodes gradually decreases to 0 as the Z coordinate value increases.
[0044] S56. Keeping the position of the innermost dense mesh node at the screw tail unchanged, perform a positional distribution operation on the multi-layer dense mesh nodes between the innermost and outermost dense meshes at the screw tail to obtain the finite element mesh of the screw tail part.
[0045] S57. Combine the finite element mesh of the main thread section and the finite element mesh of the thread tail section to obtain the complete finite element mesh of the current thread profile, such as... Figure 3 As shown.
[0046] S58. Store the finite element mesh node information into a separate node information matrix.
[0047] S6. Determine if there is a next thread profile. If so, obtain the physical parameters of the bolt corresponding to the next thread profile and return to step S5. Otherwise, proceed to step S7.
[0048] S7. For each thread profile, the node information in the node information matrix is compared sequentially by number. The node information with the smallest r-axis value for the same node number is selected, keeping the node number unchanged. All node information that meets the selection criteria is stored in a new node information matrix. The state of the double-threaded thread after filtering the node information matrices obtained from multiple sets of thread profile parameters is as follows: Figure 4 As shown in (a), the double-helix thread state is as follows: Figure 4 As shown in (b).
[0049] S8. Using a general coordinate transformation method, convert the cylindrical coordinates of the nodes in the new node information matrix to Cartesian coordinates, keeping the node numbers unchanged. Write the updated node coordinates into the finite element mesh node file before the transformation, replacing the finite element 3D node information before the transformation, and output the precise finite element model of the multi-line multi-turn thread profile, i.e., the multi-line multi-turn thread finite element model mesh node file in .inp format.
[0050] In this embodiment of the invention, the complete and precise finite element model of the DTB bolt is as follows: Figure 5 As shown in (a), it needs to be matched with two ordinary nuts with corresponding pitches. The complete precision finite element model of the Tang bolt is as follows: Figure 5 As shown in (b), it needs to be used with two nuts with the same pitch but different directions of thread (one left-handed nut and one right-handed nut).
[0051] In this embodiment of the invention, multiple sets of node information matrices are generated by repeatedly calling the contour formula of ordinary metric threads, and the matrices are filtered to generate a precise finite element model of multi-line and multi-turn thread contours under various standard and non-standard size parameters, thus laying a theoretical and technical foundation for the finite element calculation of multi-line and multi-turn threads.
[0052] In this embodiment of the invention, the dense mesh is simultaneously offset into multiple different contours by node offsetting. The contours that need to be retained are merged, and the contours that do not need to be retained are deleted, so that multi-line multi-turn threads can be generated without a dedicated contour formula.
[0053] In this embodiment of the invention, the thread profile mesh is generated by deforming the dense mesh in the undeformed bolt model into a thread profile through node offsetting. The node offsetting operation only affects the shape of the dense mesh and does not change the original mechanical parameters in the input bolt model.
[0054] In this embodiment of the invention, the outermost mesh is kept unchanged, the innermost mesh is fitted to the contour, and then the intermediate layer nodes are uniformly offset. The advantage of this method is that the number of dense mesh layers can be arbitrarily set without modifying the method itself, making it highly applicable.
[0055] 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 generating a precise finite element model of a multi-line, multi-twist thread profile, characterized in that, Includes the following steps: S1. Obtain the physical parameters of multiple bolts with multi-line and multi-turn threads and the finite element three-dimensional node information before transformation; S2. Construct the profile equation for each thread profile of the multi-line multi-turn thread that needs to be generated; S3. Convert the finite element 3D node information before transformation to Cartesian coordinates to cylindrical coordinates within the range of 0~2πrad to obtain the original mesh node cylindrical coordinate data. S4. Obtain the initial phase of the bolt physical parameters corresponding to the first thread profile; S5. Based on the original grid node cylindrical coordinate data and the current thread profile contour equation, obtain the complete finite element mesh of the current thread profile, and store the finite element mesh node information into a separate node information matrix. S6. Determine if there is a next thread profile. If so, obtain the physical parameters of the bolt corresponding to the next thread profile and return to step S5. Otherwise, proceed to step S7. S7. For each thread profile, the node information of the node information matrix is compared sequentially, and the node information with the smallest r-axis under the same node number is selected. Keeping the node number unchanged, all the node information that meets the conditions is stored as a new node information matrix. S8. Convert the cylindrical coordinates of the nodes in the new node information matrix to Cartesian coordinates, keep the node numbers unchanged, replace the finite element 3D node information before the transformation, and output the precise finite element model of the multi-line multi-turn thread profile.
2. The method for generating a precise finite element model of a multi-line, multi-turn thread profile according to claim 1, characterized in that, The bolt physical parameters in step S1 include thread type, nominal diameter, pitch, thread direction, initial phase, and the equivalent diameter of the common support surface, the number of pitches drawn, the number of pitch divisions and circumferential divisions, and the number of dense mesh layers.
3. The method for generating a precise finite element model of a multi-line, multi-turn thread profile according to claim 1, characterized in that, In step S1, the finite element three-dimensional node information before transformation is the finite element node information of the untransformed thread with a dense mesh in inp format.
4. The method for generating a precise finite element model of a multi-line, multi-turn thread profile according to claim 3, characterized in that, The specific contour equation for each thread profile constructed in step S2 is as follows: in , and These are the coordinates along the three axes of a cylindrical coordinate system. This represents the radial distance from the point to the Z-axis. Indicates the azimuth of a point. Indicates the height of the point. Indicates the nominal diameter of the bolt. This represents the tooth height of the original triangle of the thread. Indicates the pitch. Indicates the radius of the tooth base arc. , , and These are the four phase values corresponding to the inflection point of the thread profile.
5. The method for generating a precise finite element model of a multi-line, multi-turn thread profile according to claim 4, characterized in that, Step S5 includes the following sub-steps: S51. Select the multi-layer dense mesh nodes in the original mesh node cylindrical coordinate data that require contour offset operation at the external thread. S52. Based on the profile equation of the current thread profile, perform a profile offset operation on the outermost dense mesh node of the external thread. S53. Keep the position of the innermost dense mesh node at the external thread unchanged, and perform a position distribution operation on the multi-layer dense mesh nodes between the innermost and outermost dense meshes at the external thread to obtain the finite element mesh of the thread body. S54. Select the multi-layer dense grid nodes in the original grid node cylindrical coordinate data that require transition processing at the spiral tail. S55. Based on the current thread profile equation, define an offset coefficient along the Z-axis direction to perform a profile offset operation on the outermost dense mesh nodes at the thread tail, so that the offset of the nodes gradually decreases to 0 as the Z coordinate value increases. S56. Keeping the position of the innermost dense mesh node at the screw tail unchanged, perform a positional distribution operation on the multi-layer dense mesh nodes between the innermost and outermost dense meshes at the screw tail to obtain the finite element mesh of the screw tail part. S57. Combine the finite element mesh of the main thread body and the finite element mesh of the thread tail to obtain the complete finite element mesh of the current thread profile. S58. Store the finite element mesh node information into a separate node information matrix.