A method for CAE parametric modeling and preload simulation of fine threads

Abstract

The present invention provides a method for fine thread CAE parametric modeling and pre-tightening simulation, including software and working directory settings; inputting geometric feature parameters and generating a MAC file; calling MAPDL.exe and the MAC file for modeling; generating a single pitch ring and meshing it; decoupling elements from geometric features; moving nodes to generate thread features; duplicating single-pitch elements to generate a complete thread; completing remaining features to form a complete bolt; exporting a finite element model in cdb format; and applying torque and rotation angle to the bolt head for calculation. The present invention has the beneficial effects of achieving parametric modeling of a fine thread CAE model using only ANSYS software, significantly reducing software purchase costs. The principles of this modeling method are not limited to ANSYS but can also be applied to simulation software such as ABAQUS.

Description

Technical Field

[0001] The present invention belongs to the technical field of thread modeling, and in particular relates to a fine thread CAE parametric modeling and pre-tightening simulation method. Background Art

[0002] Bolt connection is one of the most common mechanical connections. The tightness of the contact surface of the connected parts and the degree of pre-tightening are the key to ensure a reliable connection. Tightening the bolts can make the bolts obtain a certain pre-tightening load. The pre-tightening load must not only make the quality of the bolt connection meet the requirements, but also make the strength of the bolts meet the requirements. Therefore, accurately simulating the bolt pre-tightening during the simulation process is of great significance for analyzing the reliability issues of bolted structures. The currently disclosed model modeling methods are complex, require a high level of finite element modeling foundation, and take a lot of time. They even require cross-calling of multiple modeling software, which greatly increases the difficulty of modeling. Due to the lack of a direct and effective parametric modeling program, refined thread CAE models and numerical simulations cannot be effectively promoted and used in engineering. Summary of the Invention

[0003] In view of this, the present invention aims to propose a fine thread CAE parametric modeling and pre-tightening simulation method to address the deficiencies of the above-mentioned prior art.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0005] A fine thread CAE parametric modeling and preload simulation method includes the following steps:

[0006] S1. Set the path of MAPDL.exe and the location of the working directory required for modeling;

[0007] S2. Set the geometric features and mesh specifications of the thread model in the main interface. Click Confirm to import the parameters into the Mac file.

[0008] S3. Click the execute modeling button, the software will start the ANSYS batch processing function and call the mac file for modeling;

[0009] S4. After setting the unit and material properties, a pitch ring geometry model is established and meshed;

[0010] S5. Use the MODMSH,DETACH command to disassociate the generated elements and nodes from the geometric model, thereby achieving the independence of the finite element model and the geometric model;

[0011] S6. Modify the position coordinates of each node according to the spatial geometric characteristics of the thread so that the unit shape conforms to the geometric characteristics of the thread;

[0012] S7, copying a finite element model of a pitch to generate finite element models of threads with multiple pitches;

[0013] S8, and complete the finite element model of the rest of the bolt to form a complete bolt connection structure;

[0014] S9. Use the CDWRITE command to output the bolt finite element model in cdb format and import it into the workbench for calculation and solution;

[0015] S10. Apply torque to the bolt head and perform torque loading method simulation calculation; after obtaining the angle result, in a new simulation calculation, apply the angle as a load to the nut to perform angle loading method simulation calculation.

[0016] Furthermore, the meshing method in step S4 is sweeping, and the unit adopts SOILD185 unit, which is a hexahedral unit with 8 nodes, and each node has translational degrees of freedom in three directions.

[0017] Furthermore, in step S6, the spatial geometric characteristics of the thread include equations (1), (2), (3), (4) and (5). For the external thread, the do loop is used to judge each node of the single pitch ring. According to the axial and circumferential coordinates of the node, the radial coordinates of the outermost node to be modified are calculated using equation (3). The radial outermost nodes form the geometric characteristics of the thread. For the non-radial outermost nodes, it is necessary to perform interpolation processing based on the radial coordinates of the nodes to obtain the radial coordinates of the corresponding nodes to be modified, and then use the nmodify command to modify the position coordinates of each node so that the unit shape conforms to the geometric characteristics of the thread.

[0018] Furthermore, the expressions of formula (1) and formula (2) are:

[0019] (1)

[0020] (2)

[0021] in: 、 、 、 、 、 , r represents the distance from the bolt axis at different positions, θ represents the cylindrical coordinate angle of the cross section, is the rotation angle.

[0022] Furthermore, the expression of formula (3) is:

[0023] (3)

[0024] in: 、 、 、 、 、 .

[0025] Furthermore, the expression of formula (4) is:

[0026] (4)

[0027] Where r represents the distance from the bolt axis at different positions, and θ represents the cylindrical coordinate angle of the cross section.

[0028] Furthermore, the expression of formula (5) is:

[0029] (5)

[0030] in: 、 、 、 、 ,r represents the distance from the bolt axis at different positions, and θ represents the cylindrical coordinate angle of the cross section.

[0031] Compared with the existing technology, the fine thread CAE parametric modeling and preload simulation method described in the present invention has the following advantages:

[0032] (1) Compared with other modeling methods, the modeling method established by the present invention, a fine thread CAE parametric modeling and pre-tightening simulation method, can realize the parametric modeling of the fine thread CAE model by using only the ANSYS software, which greatly saves the software purchase cost. The principle of this modeling method is not limited to ANSYS, but can also be extended to apply to simulation software such as ABAQUS.

[0033] (2) The present invention discloses a method for fine thread CAE parametric modeling and pre-tightening simulation, which uses the CDWRITE command to output the bolt finite element model in cdb format and imports it into the workbench for calculation and solution, thereby maximizing the advantages of APDL parametric modeling and the good interactivity of the workbench. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0035] Figure 1 This is a schematic diagram of the overall method flow according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the main interface of the program according to an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of a single-pitch circular grid according to an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of the cross-sectional outline of the external thread according to an embodiment of the present invention;

[0039] Figure 5 Schematic diagram of the variation of r with respect to θ in cylindrical coordinates of the thread profile according to an embodiment of the present invention;

[0040] Figure 6 A schematic diagram of thread feature formation by modifying coordinates of an external thread node according to an embodiment of the present invention;

[0041] Figure 7 This is a schematic diagram of thread features generated after moving a node according to an embodiment of the present invention;

[0042] Figure 8 A schematic diagram of a finite element model of a plurality of pitch external threads according to an embodiment of the present invention;

[0043] Figure 9 This is a schematic diagram of a finite element model of a nut according to an embodiment of the present invention;

[0044] Figure 10 This is a schematic diagram of a finite element model of a complete bolt connection structure according to an embodiment of the present invention;

[0045] Figure 11 Schematic diagram of the fitting characteristics between internal and external threads according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0048] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0049] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0050] like Figures 1 to 11 As shown in the figure, a fine thread CAE parametric modeling and pre-tightening simulation method can automatically generate a CAE finite element model with thread features after determining the bolt specifications.

[0051] Modeling method:

[0052] Step 1: Set the path of MAPDL.exe and the location of the working directory required for modeling;

[0053] Step 2: Set the geometric features and mesh specifications of the thread model on the main interface. Click Confirm to import the parameters into the Mac file.

[0054] Step 3: Click the Execute Modeling button, the software will start the ANSYS batch function and call the mac file for modeling;

[0055] Step 4: After setting the unit and material properties, create a pitch ring geometry model and divide it into meshes;

[0056] Step 5: Use the MODMSH,DETACH command to disassociate the generated elements and nodes from the geometric model, thereby achieving the independence of the finite element model and the geometric model;

[0057] Step 6: According to the spatial geometric characteristics of the thread, modify the position coordinates of each node so that the unit shape conforms to the geometric characteristics of the thread;

[0058] Step 7: Copy the finite element model of one pitch to generate finite element models of threads with multiple pitches;

[0059] Step 8: Complete the finite element model of the rest of the bolt to form a complete bolt connection structure;

[0060] Step 9: Use the CDWRITE command to output the bolt finite element model in cdb format and import it into the workbench for calculation and solution;

[0061] Step 10: Apply torque to the bolt head and perform the torque loading method. After obtaining the angle of rotation result, in a new calculation, apply the angle of rotation as a load to the nut and perform the angle loading method calculation.

[0062] The present invention can modify the position coordinates of each node based on the spatial geometric characteristics of the thread, making the unit shape conform to the geometric characteristics of the thread. Furthermore, the present invention can apply torque to the bolt head to perform torque loading calculations. After obtaining the angle result, in a new calculation, the angle is applied as a load to the nut for angle loading calculations.

[0063] Key technical points of the present invention:

[0064] 1) Automatically identify thread specifications based on the blank diameter of the blank model. This eliminates the need to repeatedly input thread specifications during the production process, enabling automatic thread specification recognition.

[0065] 2) Use the MODMSH,DETACH command to disassociate the generated elements and nodes from the geometric model, thereby achieving independence between the finite element model and the geometric model, and thus realizing the modification of the node coordinates.

[0066] Beneficial effects of the present invention:

[0067] 1) Compared with other modeling methods, the modeling method established in the present invention can realize the parametric modeling of the fine CAE model of the thread using only the ANSYS software, which greatly saves the software purchase cost. The principle of this modeling method is not limited to ANSYS, but can also be extended to simulation software such as ABAQUS.

[0068] 2) Use the CDWRITE command to output the bolt finite element model in cdb format and import it into the workbench for calculation and solution, making full use of the advantages of APDL parametric modeling and the good interactivity of the workbench.

[0069] Example 1

[0070] The main interface of the program is as follows Figure 2 shown.

[0071] The first part is the main interface of the software written in Python. The main operating logic is:

[0072] (1) Set the path of MAPDL.exe and the location of the working directory required for modeling.

[0073] (2) Set the geometric features and mesh specifications of the thread model on the main interface. Click the parameter confirmation button to import the parameters into the Mac file.

[0074] (3) Click the execute modeling button, the software will start the ANSYS batch function and call the mac file for modeling.

[0075] (4) After the modeling is completed, click the Open Directory button to open the working directory and directly view the created model file.

[0076] The second part is the ANSYS batch processing function and calls the mac file for modeling. Its main operating logic is:

[0077] After setting the unit and material properties, a pitch ring geometry model is established and meshed. The meshing method is sweeping, and the unit uses SOILD185 unit, which is a hexahedral unit with 8 nodes. Each node has three translational degrees of freedom, such as Figure 3 shown.

[0078] This paper uses a method to modify node coordinates to generate thread geometry. However, the finite element model (elements and nodes) created in ANSYS is linked to the geometric model, making it impossible to modify either model independently. To address this issue, this paper uses the modmsh,detach command to decouple the generated finite element model from the geometric model, achieving mutual independence between the two. Once the finite element model and the geometric model are decoupled, the vdele,all,,,1 command can be used to delete the body and the geometric elements contained within it.

[0079] Any cross section perpendicular to the bolt axis at the bolt thread (except the undercut) has the following characteristics: Figure 4 The shapes shown, the bolt sections at different positions are considered Figure 4 The cross section rotates a certain angle around the bolt axis within a pitch range, i.e. 360°. The thread outer contour line has gone through a full pitch, and the relationship between the distance r from the bolt axis at different positions and the cylindrical coordinate angle θ of the cross section is as follows: Figure 5 shown.

[0080] Assuming that the figure shows the cross-sectional shape at z=0, the outer surface of the thread at z=0 can be expressed by a piecewise function:

[0081] (1)

[0082] in: 、 、 、 、 、

[0083] If this section is called the base surface, then another section at a distance z from the base surface has the same shape, but in the same cylindrical coordinates, the profile is rotated around the z axis by an angle. For right-hand threads, the additional rotation angle is for:

[0084] (2)

[0085] The outer surface of a complete single thread can be expressed as:

[0086] (3)

[0087] in: 、 、 、 、 、

[0088] And the outer surface equation should be periodic:

[0089] (4)

[0090] Similarly, the helicoidal surface of an internal thread can be expressed as:

[0091] (5)

[0092] in: 、 、 、 、 ;

[0093] For external threads, a do loop is used to judge each node of the single-pitch ring. Based on the axial and circumferential coordinates of the nodes, the radial coordinates of the outermost nodes to be modified are calculated using formula (3). The radial outermost nodes form the geometric characteristics of the thread. For non-radial outermost nodes, interpolation processing is required based on the radial coordinates of the nodes to obtain the radial coordinates of the corresponding nodes to be modified. Then, the nmodify command is used to modify the position coordinates of each node so that the unit shape conforms to the geometric characteristics of the thread, such as Figure 6 As shown. The finite element model of a thread pitch is as follows Figure 7 shown.

[0094] Except for the thread transition section, the entire thread has a periodic feature with the pitch as the spacing. The finite element model of one pitch is translated and copied to generate the finite element model of multiple pitches. Figure 8 The 1 / 2 pitch length on the left side of the figure is the thread transition section, which serves to connect the polished rod and the thread. The position coordinates of its node can be obtained by interpolation between the polished rod end face and the thread end face.

[0095] The same method can be used to establish the finite element model of the nut. Figure 9 shown.

[0096] Since the external thread is a hollow ring structure, it is necessary to fill its hollow part and establish the finite element model of the bolt head and the connected parts. This part is relatively basic and will not be described in detail in this article. Finally, the finite element model of the complete bolt connection structure is obtained as follows Figure 10 shown.

[0097] Use the CDWRITE command to export the bolt finite element model in cdb format. Import it into Workbench software for analysis. First, apply torque to the bolt head and perform the torque loading method. After obtaining the angle of rotation, apply the angle of rotation as a load to the nut in a new calculation using the angle loading method.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fine thread CAE parametric modeling and preload simulation method, characterized by: The following steps are involved: S1. Set the path of MAPDL.exe and the location of the working directory required for modeling; S2. Set the geometric features and mesh specifications of the thread model in the main interface. Click Confirm to import the parameters into the Mac file. S3. Click the execute modeling button, the software will start the ANSYS batch processing function and call the mac file for modeling; S4. After setting the unit and material properties, a pitch ring geometry model is established and meshed; S5. Use the MODMSH,DETACH command to disassociate the generated elements and nodes from the geometric model, thereby achieving the independence of the finite element model and the geometric model; S6. Modify the position coordinates of each node according to the spatial geometric characteristics of the thread so that the unit shape conforms to the geometric characteristics of the thread; S7, copying a finite element model of a pitch to generate finite element models of threads with multiple pitches; S8, and complete the finite element model of the rest of the bolt to form a complete bolt connection structure; S9. Use the CDWRITE command to output the bolt finite element model in cdb format and import it into the workbench for calculation and solution; S10. Apply torque to the bolt head and perform torque loading method simulation calculation; after obtaining the angle result, in a new simulation calculation, apply the angle as a load to the nut to perform angle loading method simulation calculation.

2. The fine thread CAE parametric modeling and preload simulation method according to claim 1 is characterized by: The meshing method in step S4 is sweeping, and the unit adopts SOILD185 unit, which is a hexahedral unit with 8 nodes, and each node has translational degrees of freedom in three directions.

3. The fine thread CAE parametric modeling and preload simulation method according to claim 1 is characterized by: In step S6, the spatial geometric features of the thread include the piecewise function of the distance from the bolt axis at z=0 under the cross-sectional shape condition at z=0, the rotation angle, the piecewise function of the distance from the bolt axis at z=0 under the condition of a complete single thread outer surface, the periodic equation of the thread outer surface, and the piecewise function of the distance from the bolt axis at z=0 under the condition of the helical surface of the internal thread; wherein, formula (1) is used to express the piecewise function of the distance from the bolt axis at z=0 under the cross-sectional shape condition at z=0, formula (2) is used to express the rotation angle, and formula (3) is used to express the distance from the bolt axis at z=0 under the condition of a complete single thread outer surface. The periodic equation of the outer surface of the thread is expressed by equation (4). The periodic equation of the outer surface of the thread is expressed by equation (5). The periodic function of the distance from the bolt axis at z = 0 under the condition of the helical surface of the internal thread is expressed by equation (5). For the external thread, the do loop is used to judge each node of the single pitch ring. According to the axial and circumferential coordinates of the node, the radial coordinates of the outermost node to be modified are calculated using equation (3). The radial outermost nodes form the geometric features of the thread. For the non-radial outermost nodes, interpolation processing is required according to the radial coordinates of the nodes to obtain the radial coordinates of the corresponding nodes to be modified. Then, the nmodify command is used to modify the position coordinates of each node so that the unit shape conforms to the geometric features of the thread.

4. The fine thread CAE parametric modeling and preload simulation method according to claim 3 is characterized by: The expressions of formula (1) and formula (2) are: (1) (2) in: 、 、 、 、 、 , r represents the distance from the bolt axis at different positions, θ represents the cylindrical coordinate angle of the cross section, is the rotation angle.

5. The fine thread CAE parametric modeling and preload simulation method according to claim 3 is characterized by: The expression of formula (3) is: (3) in: 、 、 、 、 、 .

6. The fine thread CAE parametric modeling and preload simulation method according to claim 3 is characterized by: The expression of formula (4) is: (4) Where r represents the distance from the bolt axis at different positions, and θ represents the cylindrical coordinate angle of the cross section.

7. The fine thread CAE parametric modeling and preload simulation method according to claim 3 is characterized by: The expression of formula (5) is: (5) in: 、 、 、 、 ,r' represents the distance from the bolt axis at different positions, and θ represents the cylindrical coordinate angle of the cross section.

8. An electronic device comprising a processor and a memory in communication with the processor and configured to store instructions executable by the processor, wherein: The processor is used to execute a fine thread CAE parametric modeling and pre-tightening simulation method as described in any one of claims 1-7 above.

9. A server, characterized in that: It includes at least one processor and a memory communicatively connected to the processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the processor so that the at least one processor executes a fine thread CAE parametric modeling and preload simulation method as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for fine thread CAE parametric modeling and pre-tightening simulation as described in any one of claims 1 to 7 is implemented.

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