Finite element fine modeling method for semi-automatic threaded connection structure

Abstract

The invention provides a finite element fine modeling method for a semi-automatic threaded connection structure, and the method comprises the steps: 1, building a grid model with the nominal diameter of d according to the engineering demands, and determining the node coordinates of a grid in the grid model; 2, specification parameters of threads needing to be generated are determined; 3, establishing a polar coordinate system on the thread starting plane, and setting the origin of coordinates as the intersection point of the axis of the cylindrical grid model and the thread starting plane; 4, the node coordinates are converted into polar coordinates (r,) for projection of a single circle of threads on a plane under a polar coordinate system, and r represents the polar diameter of the grid nodes and represents the lead angle of the grid nodes; 5, calculating the radial distance r from any point on the thread profile to the thread rotating shaft according to the thread specification parameters and the thread lead angle; and 6, editing the cylindrical grid model according to the radial distance r.

Description

Technical Field

[0001] This application relates to the field of finite element simulation of aerospace machinery, specifically to a fine finite element modeling method for semi-automated threaded connection structures. Background Technology

[0002] Today, threaded connections play a vital role in all aspects of industrial production and daily life. In the aerospace field, with advancements in research and design capabilities, the probability of failure due to insufficient structural strength has decreased. Instead, sporadic and detailed issues such as failures at the connections between different mechanisms have become the focus of future research. Consequently, there is a need for refined modeling during the initial simulation calculation stage of product design.

[0003] In typical finite element simulation workflows, threaded structures are often simplified due to their small size or insufficient detail in the original 3D model. This simplification includes methods such as merging mesh nodes between different structures, coupling different structures, or simulating threaded connections using beam elements. However, to meet the demand for higher simulation model detail, it is necessary to perform refined modeling of the threaded connections.

[0004] To perform detailed modeling of threaded connections, the following finite element meshing methods are commonly used: One method involves separately meshing the cylinder at the thread neck and the thread itself, which requires increasing the mesh density at the thread tooth profile locations; the other method involves accurately modeling the thread's 3D geometry and then meshing the entire geometric model, which requires a significant amount of time during the finite element model creation process. Both methods result in a decrease in mesh size while increasing the number of meshes, and the combined effect of these two factors significantly increases computation time. Summary of the Invention

[0005] This invention proposes a semi-automated finite element fine modeling method for threaded connection structures, which can solve the problem of difficult mesh generation in threaded finite element models.

[0006] Technical solution: A semi-automated finite element fine modeling method for threaded connection structures, the method including: Step 1: Establish a mesh model with a nominal diameter of d according to the project requirements, and determine the node coordinates of the mesh in the mesh model; Step 2: Determine the required thread specifications; Step 3: Establish a polar coordinate system on the thread starting plane, with the origin set as the intersection of the mesh model's axis and the thread starting plane; Step 4: Convert the node coordinates into polar coordinates (r, ..., ...) representing the projection of a single turn of the thread onto a plane. ), where r represents the polar radius of the grid node, Indicates the helix angle of the mesh node; Step 5: According to the thread specification parameters and thread helix angle Calculate the radial distance r from any point on the thread profile to the thread rotation axis; Step 6: Edit the cylindrical mesh model according to the radial distance r.

[0007] Specifically, step 2 includes: Step 21: Determine the thread pitch P and thread profile height H; Step 22: Set a fillet with a radius of R at the crest of the thread.

[0008] Specifically, the pitch P of a thread is the axial distance between two corresponding points on the pitch diameter of two adjacent threads; The thread profile height H is the vertical distance from the crest of the thread to the root of the thread.

[0009] Specifically, the fillet radius R and the pitch P satisfy... .

[0010] Specifically, step 5 includes: When the helix angle The range is At that time, radial distance ; Specifically, step 5 includes: When the helix angle The range is At that time, radial distance ; Specifically, step 5 includes: When the helix angle The range is At that time, radial distance ; Specifically, step 5 includes: When the helix angle The range is At that time, radial distance ; Specifically, step 5 includes: When the helix angle The range is At that time, radial distance ; Specifically, step 5 includes: When the helix angle The range is At that time, radial distance .

[0011] In summary, this invention provides a semi-automated finite element fine modeling method for threaded connection structures. It only requires establishing a mesh model of the nominal thread diameter, and the original mesh file is directly edited through the program to automatically adjust the coordinate positions of the mesh nodes, thereby generating a mesh structure of the thread shape. This method does not require fine 3D geometric modeling of the thread structure, nor does it increase the number of meshes in the original model. For thread modeling with different thread profiles, different thread major diameters, and different pitches, only some pre-output parameters in the program need to be adjusted, making it universally applicable and very helpful for fine thread modeling. Attached Figure Description

[0012] Figure 1 A comparison diagram showing the original finite element mesh model required by simulation engineers and the model automatically adjusted by this invention.

[0013] Figure 2 A schematic diagram of local information in an editable preprocessing file exported from the original finite element mesh.

[0014] Figure 3 This is a schematic diagram of a single-turn helix cross-section.

[0015] Figure 4 This is a schematic diagram showing the original positions of the cylindrical finite element mesh nodes in three-dimensional space and the node coordinates after being edited by the program.

[0016] Figure 5 This is a schematic diagram of the cross-sectional view of the internal thread mesh.

[0017] Figure 6 This is a schematic diagram of the mesh model after the internal and external threads are combined. Detailed Implementation

[0018] This invention provides a semi-automated finite element fine modeling method for threaded connection structures. First, simulation engineers need to create a cylindrical finite element mesh model with the nominal diameter of the thread. Then, this cylindrical mesh model is exported as a pre-processing file for secondary development and programming. This file contains the element and node information of the initial finite element mesh model. Subsequently, the coordinate parameters of these nodes are edited using the mathematical formulas employed in this invention, finally obtaining the threaded finite element mesh model required for finite element simulation.

[0019] To demonstrate the effects achievable by this invention, an external thread profile is used as an example. Figure 1 (Left) shows the original mesh required for the finite element mesh. Figure 1 (Right) is the model after being automatically adjusted by the program.

[0020] Example 1 This invention provides a semi-automatic finite element fine modeling method for threaded connection structures. Taking external threads as an example, the specific steps are as follows: Step 1: Establish a cylindrical mesh model with a nominal diameter of d according to the project requirements, and determine the node coordinates of the mesh in the cylindrical mesh model; like Figure 2 As shown, the node coordinates of the cylindrical mesh are (X, Y, Z). This application only processes the values ​​of X and Y, while the Z coordinate value remains unchanged.

[0021] In practical applications, cylindrical mesh models can be exported as pre-processed files that can be used for secondary development and programming.

[0022] Step 2: As Figure 3 As shown, the required external thread specifications are clearly defined.

[0023] Specifically, step 2 includes: Step 21: Determine the pitch P and thread height H of the external thread; Wherein, the pitch P of the external thread is the axial distance between two corresponding points on the pitch diameter of two adjacent threads; the thread profile height H is the vertical distance from the crest to the root of the thread. Step 22: Set a fillet with a radius of R at the thread crest; It should be noted that setting a fillet with a radius of R at the thread crest can prevent stress concentration at the thread crest.

[0024] Specifically, the fillet radius R and the pitch P satisfy... .

[0025] Step 3: Establish a polar coordinate system on the thread starting plane, with the origin set as the intersection of the axis of the cylindrical mesh model and the thread starting plane; Step 4: Convert the node coordinates into polar coordinates (r, ..., ...) representing the projection of a single turn of the thread onto a plane. ), where r represents the polar radius of the grid node, Indicates the helix angle of the mesh node; It should be noted that the polar coordinate system is used to facilitate the editing of cylindrical mesh cell nodes.

[0026] Step 5: Based on the external thread specifications and thread helix angle Calculate the radial distance r from any point on the thread profile to the thread rotation axis; Specifically, step 5 includes: When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance .

[0027] Step 6: Edit the cylindrical mesh model according to the radial distance r.

[0028] In practical applications, the preprocessing file is edited, focusing on the coordinate values ​​of the mesh nodes. For multi-turn thread meshes, a loop statement defined within the total thread length is sufficient to traverse all element nodes. This ultimately generates the external thread preprocessing file required by simulation engineers, whose visualization is shown below. Figure 4 As shown.

[0029] Example 2 like Figure 5 As shown, taking the ISO metric single-turn standard internal thread profile as an example, this invention can provide a semi-automatic finite element fine modeling method for threaded connection structures. The specific steps are as follows: Step 1: The simulation engineer creates a cylindrical mesh model with a nominal diameter of d according to the engineering requirements; and determines the node coordinates of the cylindrical mesh in the cylindrical mesh model. In practical applications, the cylindrical mesh model is exported as a pre-processing file that can be used for secondary development and programming.

[0030] Step 2: As Figure 3 As shown, the required internal thread specifications are clearly defined.

[0031] Specifically, step 2 includes: Step 21: Determine the pitch P and thread height H of the internal thread; Wherein, the pitch P of the internal thread is the axial distance between two corresponding points on the pitch diameter of two adjacent threads; the thread profile height H is the vertical distance from the crest to the root of the internal thread. Step 22: Set a fillet with a radius of R at the root of the thread; It should be noted that setting a fillet with a radius of R at the root of the thread can prevent stress concentration at the root of the thread.

[0032] Specifically, the fillet radius R and the pitch P satisfy... .

[0033] Step 3: Establish a polar coordinate system on the thread starting plane, with the origin set as the intersection of the axis of the cylindrical mesh model and the thread starting plane; Step 4: Convert the node coordinates into polar coordinates (r, ..., ...) representing the projection of a single turn of the thread onto a plane. ), where r represents the polar radius of the grid node, Indicates the helix angle of the mesh node; It should be noted that the polar coordinate system is used to facilitate the editing of cylindrical mesh cell nodes.

[0034] Step 5: According to the internal thread specifications and thread helix angle Calculate the radial distance r from any point on the thread profile to the thread rotation axis; Specifically, step 5 includes: When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance ; When the helix angle The range is At that time, radial distance .

[0035] Step 6: Edit the cylindrical mesh model according to the radial distance r.

[0036] In practical applications, the preprocessing file is edited, focusing on the coordinate values ​​of the mesh nodes. For multi-turn thread meshes, a loop statement defined within the total thread length is sufficient to traverse all element nodes. This ultimately generates the internal thread preprocessing file required by simulation engineers, whose visualization is shown below. Figure 4 As shown.

[0037] like Figure 6 The image shown is a schematic diagram of the assembly cross-section of the final generated internal thread mesh model.

[0038] The method described above only uses the ISO standard thread profile as an example to illustrate the implementation process of this invention. For different thread sizes or different thread profiles, it is only necessary to obtain the polar coordinates r of the thread profile helix angle. The mathematical relationship between them can also be used to obtain other commonly used thread mesh models based on this method.

[0039] Furthermore, the method described in this invention directly edits the original mesh coordinate values ​​and has no special requirements on the program format and mesh type (i.e., both hexahedral and tetrahedral meshes are applicable). Verification has shown that the method described in this invention can process *.inp files and *.k files, etc., which are general finite element model files, and has certain universal characteristics.

Claims

1. A semi-automated finite element fine modeling method for threaded connection structures, characterized in that, The methods include: Step 1: Establish a mesh model with a nominal diameter of d according to the project requirements, and determine the node coordinates of the cylindrical mesh in the mesh model; Step 2: Determine the required thread specifications; Step 3: Establish a polar coordinate system on the thread starting plane, with the origin set as the intersection of the axis of the cylindrical mesh model and the thread starting plane; Step 4: Convert the node coordinates into polar coordinates (r, ..., ...) representing the projection of a single turn of the thread onto a plane. ), where r represents the polar radius of the grid node, Indicates the helix angle of the mesh node; Step 5: According to the thread specification parameters and thread helix angle Calculate the radial distance r from any point on the thread profile to the thread rotation axis; Step 6: Edit the cylindrical mesh model according to the radial distance r.

2. The finite element fine modeling method according to claim 1, characterized in that, Step 2 includes: Step 21: Determine the thread pitch P and thread profile height H; Step 22: Set a fillet with a radius of R at the crest of the thread.

3. The finite element fine modeling method according to claim 2, characterized in that, The pitch P of a thread is the axial distance between two corresponding points on the pitch diameter of two adjacent threads; The thread profile height H is the vertical distance from the crest of the thread to the root of the thread.

4. The finite element fine modeling method according to claim 2, characterized in that, The fillet radius R and the pitch P satisfy .

5. The finite element fine modeling method according to claim 1, characterized in that, Step 5 includes: When the helix angle The range is At that time, radial distance .

6. The finite element fine modeling method according to claim 1, characterized in that, Step 5 includes: When the helix angle The range is At that time, radial distance .

7. The finite element fine modeling method according to claim 1, characterized in that, Step 5 includes: When the helix angle The range is At that time, radial distance 。 8. The finite element fine modeling method according to claim 1, characterized in that, Step 5 includes: When the helix angle The range is At that time, radial distance 。 9. The finite element fine modeling method according to claim 1, characterized in that, Step 5 includes: When the helix angle The range is At that time, radial distance .

10. The finite element fine modeling method according to claim 1, characterized in that, Step 5 includes: When the helix angle The range is At that time, radial distance .

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