Finite element modeling method for surface rolling of thin-wall circular tube structure

Abstract

The invention discloses a thin-wall circular tube structure surface rolling finite element modeling method, which belongs to the technical field of structural physics field simulation, and comprises the following steps: model construction: constructing two groups of solid geometric models of a thin-wall circular tube and a rolling disc, the model of the thin-wall circular tube comprising a clamping section, a free section and an imaginary block 1; the model of the rolling disc comprises a disc body and an imaginary block 2; setting material parameters and contact parameters; aiming at the disc body and the free section, dividing grids by adopting a hexahedron; adaptive grid division is adopted for the hypothetical block 1, the hypothetical block 2 and the clamping section; for the contact pair, the grid size of the disc body contact surface is larger than that of the free section contact surface; setting three groups of load steps, wherein each group of load steps comprises at least one load substep; the first group of simulation rolling discs are fed, the second group of simulation thin-wall round pipes rotate and are rolled, and the third group of simulation rolling discs are withdrawn; and carrying out calculation solution based on the finite element model established in the steps to obtain the stress of the free section. Through the modeling method provided by the invention, the influence characteristics of the rolling process parameters on the stress state of the rolled thin-walled circular tube can be quantitatively analyzed in a parameterized manner, so as to support the research on the rolling process.

Description

A Finite Element Modeling Method for Surface Rolling of Thin-Walled Circular Tube Structures Technical Field

[0001] This invention relates to the field of structural physics field simulation technology, specifically to a finite element modeling method for surface rolling of thin-walled circular tube structures. Background Technology

[0002] In some engineering applications, to achieve specific functions, such as limiting protrusions on the inner surface of a tube, thin-walled circular tube structures require roll forming on the outer surface to create grooves. During the roll forming process, the thin-walled circular tube undergoes elastoplastic deformation, generating residual stress, which affects the stress and deformation of the thin-walled circular tube under load. To control this effect and avoid unacceptable impacts on the quality and reliability of the thin-walled circular tube product, the influence of processing parameters on the deformation and stress of the thin-walled circular tube should be understood during the roll forming stage. To ensure the structural processing quality and reliability, processing parameters must be rationally selected to control the stress and deformation state of the structure. This requires understanding the quantitative relationship between process parameters and structural stress and deformation.

[0003] The finite element method (FEM) is a commonly used tool for analyzing the mechanical response of engineering structures under stress conditions, and it is feasible in analyzing the rolling deformation of thin-walled circular tube structures. For thin-walled circular tube structures, several technical cases have already achieved finite element analysis of deformation and stress under conditions such as axial tension, axial compression, radial tension and bending, radial pure bending, and three-point bending. In the prior art, patent CN117875103A discloses a finite element simulation method for the rolling process of high-strength steel DP590 wheel rims, belonging to the field of material forming technology. Its technical solution is as follows: using ABAQUS finite element software, the rim is divided into three different parts: weld seam, heat-affected zone, and base material. A reverse design method is used to design molds for each process of rim processing, establishing models for each processing step, such as flaring, three-pass rolling forming, and expansion finishing. This prior art uses finite element simulation to study the distribution of deformation during the rolling forming process, the influence of various process parameters on the dynamic details of the process, and the final result during the processing from steel rim to the final rim product.

[0004] However, the aforementioned patent solution reflects a rolling process involving molding and sliding friction, and its modeling method cannot be directly applied to a roller extrusion process. Furthermore, the geometric model in this patent solution employs a reverse design approach and requires a guide wheel tooling solid model to control boundary conditions, resulting in a large number of elements and significant computational resource consumption. Summary of the Invention

[0005] This invention aims to overcome the problem that it is difficult to theoretically calculate the deformation and stress of thin-walled circular tube structures under surface rolling processing conditions. It proposes a finite element modeling method for surface rolling of thin-walled circular tube structures, which can support the finite element analysis of deformation and stress of thin-walled circular tube structures under surface rolling conditions.

[0006] To achieve the above-mentioned objectives, the technical solution of this invention is as follows: A finite element modeling method for surface rolling of a thin-walled circular tube structure, comprising the following steps: Model construction: constructing geometric models of two sets of entities, a thin-walled circular tube and a rolling disc. The model of the thin-walled circular tube includes a clamping section, a free section, and an imaginary block 1; the model of the rolling disc includes a disc body and an imaginary block 2; the axis of the disc body is parallel to the axis of the thin-walled circular tube, and the distance between the edge of the disc body and the surface of the thin-walled circular tube is not less than 0; Parameter setting: setting material parameters for the free section, clamping section, and imaginary block 1 of the thin-walled circular tube, and the disc body and imaginary block 2 of the rolling disc. Number and contact parameters; Mesh generation: For the disk and free segment, a hexahedral mesh is used; For imaginary block 1, imaginary block 2 and clamping segment, an adaptive mesh is used; For contact pairs, the mesh size of the disk contact surface is larger than the mesh size of the free segment contact surface; Boundary condition settings: Set 3 sets of load steps, each load step has at least 1 load substep; The first set simulates the roller feed, the second set simulates the rotation of the thin-walled circular tube under rolling pressure, and the third set simulates the roller retraction; Model solution: Based on the finite element model established in the above steps, perform calculations to obtain the stress in the free segment.

[0007] Preferably, in the model building step, the model building process of the thin-walled circular tube is as follows: a plane 1 perpendicular to the axis of the thin-walled circular tube is specified, and a concentric circular outline is drawn in the plane 1 to represent the cross-section of the thin-walled circular tube. The inner diameter of the concentric circular outline is the inner diameter of the thin-walled circular tube, and the outer diameter is the outer diameter of the thin-walled circular tube. Subsequently, based on the concentric circular outline, additive manufacturing is performed by axial stretching, and the total length of the additive manufacturing is the axial length of the thin-walled circular tube.

[0008] Preferably, in the model construction step, the clamping segment and the free segment are determined as follows: a plane 2 perpendicular to the axis of the thin-walled circular tube is specified, so that the interface between the clamping segment and the free segment of the thin-walled circular tube is within the plane 2.

[0009] Preferably, in the model construction step, the construction method of the imaginary block 1 is as follows: specify a plane 3 parallel to plane 2, the distance between the plane 3 and plane 2 is 10%~40% of the axial length of the clamping segment, and it passes through the clamping segment but not through the free segment; draw a 90° sector profile 1 in plane 3, the radius is the inner radius of the thin-walled circular tube, and the vertex of the central corner is on the axis of the thin-walled circular tube; then, based on the sector profile 1, additive manufacturing is carried out by axial stretching, the total additive length is the length of the clamping segment minus the distance between plane 3 and plane 2, so as to form an imaginary block 1 solid tangent to the inner surface of the clamping segment, and the end face of the imaginary block 1 perpendicular to its own axis should be in the same plane as the end face of the clamping segment perpendicular to its own axis.

[0010] Preferably, in the model building step, the disk body is constructed as follows: a plane 4 is specified that is perpendicular to planes 2 and 3, and the plane formed by the axis of the roller and the axis of the thin-walled circular tube is also perpendicular to plane 4; a shape profile is drawn in plane 4 to represent the cross-sectional shape of the roller before core removal; then, based on the shape profile, additive material is added by rotating 360° around a fixed axis to form the solid disk before core removal; a plane 5 is specified that is perpendicular to the axis of the roller, and a circular profile is drawn in plane 5 with a diameter equal to the core removal diameter of the roller, and the axis of the roller passes through the center of the circular profile; then, based on the circular profile, subtractive material is added by axial stretching to core the roller before core removal to obtain the solid disk body.

[0011] Preferably, a plane 6 perpendicular to the axis of the roller is specified, and a 90° sector outline 2 is drawn in the plane 6 with a radius equal to the radius of the roller's center and the vertex of the central corner is located on the axis of the roller; then, based on the sector outline 2, additive manufacturing is performed by axial stretching, and the total length of the additive manufacturing should be greater than the thickness of the roller body to form a solid imaginary block 2. The two end faces of the imaginary block 2 perpendicular to its own axis extend axially beyond the two end faces of the roller body perpendicular to its own axis.

[0012] Preferably, in the parameter setting step, the material parameters set for the thin-walled circular tube include Young's modulus, Poisson's ratio, yield strength, and hardening modulus, and the material parameters set for the roller include Young's modulus and Poisson's ratio; and the Young's modulus of the roller material shall not be lower than the Young's modulus of the thin-walled circular tube material.

[0013] Preferably, in the parameter setting step, the contact parameters set include: the contact pair consists of the outer surface of the free segment and the side surface of the disk, the contact form is non-slip friction with a friction coefficient considered to be infinite, and the initial spacing of the contact pair in the geometric model is 0.

[0014] Preferably, in the boundary condition setting step, the first load step includes: applying a linear displacement in the feed direction to the axis edge of the imaginary block 2, while fixing the linear displacement in the other two orthogonal directions; fixing the total displacement to the axis edge of the imaginary block 1; fixing the rotation around the axis edge of the imaginary block 1 and its two orthogonal directions to the outer surface of the clamping section, while fixing the linear displacement in the direction of the axis edge of the imaginary block 1.

[0015] Preferably, in the boundary condition setting step, the second load step includes: for the axis edge of imaginary block 2, only the rotational degree of freedom around the axis is retained, the rotation in two orthogonal directions around the axis is fixed, and at the same time, the linear displacement of the axis and its two orthogonal directions is fixed, while maintaining the linear displacement in the feed direction generated by the first load step; for the axis edge of imaginary block 1, the full displacement is fixed; for the outer surface of the clamping section, the linear displacement in the direction of the axis edge of imaginary block 1 is fixed, and at the same time, the rotation angle around the axis edge of imaginary block 1 is applied in the sub-load sub-step, and the rotation in the two orthogonal directions around the axis edge of imaginary block 1 is fixed.

[0016] Preferably, in the boundary condition setting step, the third load step includes: applying a linear displacement in the exit direction to the axis of imaginary block 2, while fixing the linear displacement in the other two orthogonal directions; fixing the total displacement to the axis of imaginary block 1; fixing the rotation about the axis of imaginary block 1 and its two orthogonal directions to the outer surface of the clamping section, while maintaining the rotation angle about the axis of imaginary block 1 generated by the second load step, while fixing the linear displacement in the direction of the axis of imaginary block 1.

[0017] In summary, the present invention has the following advantages: 1. The present invention replaces the traditional irreversible test method and uses the finite element modeling method to provide the necessary support conditions for finite element analysis. It can obtain information with sufficient accuracy on the quantitative relationship between the deformation and stress of thin-walled circular tubes and the rolling process parameters while significantly reducing test costs.

[0018] 2. In the technical details of finite element modeling, this invention innovatively adopts the method of introducing imaginary block entities for geometric modeling, which eliminates the need to establish a limit tooling entity model, thereby saving computational resources. It can also conveniently apply boundary conditions to thin-walled circular tubes and rollers, and accurately simulate the loads and constraints they are subjected to under actual rolling processing conditions.

[0019] 3. The finite element model of thin-walled circular tube structure rolling established by the method of the present invention can be used to parameterize and quantitatively analyze the influence characteristics of rolling process parameters on the stress state of thin-walled circular tube structure after rolling, so as to support the research on rolling process. Attached Figure Description

[0020] Figure 1 is a schematic diagram of the thin-walled circular tube before segmentation; Figure 2 is a schematic diagram of the thin-walled circular tube after segmentation; Figure 3 is a schematic diagram of the position of imaginary block 1 inside the thin-walled circular tube; Figure 4 is a schematic diagram of the rolling disc before core removal; Figure 5 is a schematic diagram of the disc body; Figure 6 is a schematic diagram of the position of imaginary block 2 inside the disc body; Figure 7 is a schematic diagram of the complete geometric model; Figure 8 shows the mesh division effect of each entity in Embodiment 1 of the present invention; Figure 9 shows the stress values ​​of each terminal rolling section under two rolling process parameter conditions in Embodiment 1 of the present invention; Figure 10 shows the orthogonal table used in Embodiment 2 of the present invention; Figure 11 shows the mesh size requirements and the number of model elements divided for each entity in Embodiment 2 of the present invention; Figure 12 shows the stress values ​​of each terminal rolling section under various conditions of the orthogonal test in Embodiment 2 of the present invention.

[0021] Figure 13 is a flowchart of the implementation of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0025] In the description of this invention, it should be noted that the terms "upper," "vertical," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] Implementation Case 1: In this implementation case, a finite element model of the surface rolling of a terminal block in a thin-walled metal circular tube structure is considered. Finite element analysis of the rolling process is performed based on the model to obtain the stress of the terminal block after rolling. Referring to Figure 13 in the specification, the specific steps include: Step 1: Geometric Modeling. The terminal block consists of three parts: a clamping section, a free section, and an imaginary block 1, constituting the terminal block component.

[0028] Specify a three-dimensional Cartesian right-handed coordinate system in mm. The terminal block axis coincides with the x-axis. Designate the yz plane as plane 1, which is perpendicular to the terminal block axis. Draw a concentric circle outline 1 within plane 1, centered at the origin O of the coordinate system, with an inner diameter of 3.5 mm and an outer diameter of 4 mm.

[0029] Subsequently, based on contour 1, additive manufacturing is performed by stretching, stretching 4mm in the positive x-axis direction and 8mm in the negative x-axis direction to form the terminal body before splitting, with a total axial length of 12mm.

[0030] Define a plane 2, represented as x+4=0 in the coordinate system, which is the interface between the terminal clamping section and the free section. Based on plane 2, divide the terminal into two parts: a clamping section and a free section, with axial lengths of 4mm and 8mm respectively.

[0031] Specify a plane 3, represented as x+5=0 in the coordinate system, with a distance of 1mm from plane 2. Draw a 90° sector outline 2 in plane 3 with a radius of 1.75mm. The coordinates of the central angle vertex and the two intersection points of the arc and the straight line side in the coordinate system are (-5, 0, 0), (-5, 1.75, 0), and (-5, 0, -1.75), respectively.

[0032] Subsequently, based on contour 2, additive manufacturing is performed by stretching the material 3mm in the negative x-axis direction to form the imaginary block 1 solid.

[0033] The roller consists of two parts: the disc body and the imaginary block 2, which together form the roller assembly.

[0034] Define a plane 4, represented as z-11.15=0 in the coordinate system, with the roller axis lying within plane 4. Define four points within plane 4 with coordinates (0, 0, 11.5), (1.9, 0, 11.5), (1.9, 6.75, 11.5), and (0, 9.15, 11.5). Connect these four points with straight lines to form a right trapezoid. For the vertex at coordinates (0, 9.15, 11.5), apply a fillet with a radius of 0.15mm. This forms the cross-sectional shape profile 3 of the centered roller.

[0035] Subsequently, based on contour 3, additive manufacturing is performed by rotating 360° around a fixed axis, with the intersection of plane 4 and the xz plane as the axis, to form a coreless front roller solid, which is a frustum-shaped rotating body.

[0036] Designate the yz plane as plane 5, which is perpendicular to the roller axis. Draw a circular outline 4 within plane 5, with the center coordinates (0, 0, 11.15) and a diameter of 3.9 mm. The roller axis passes through this center.

[0037] Subsequently, based on contour 4, the coreless disc body is reduced by axial stretching to obtain the coreless disc body.

[0038] Designate the yz plane as plane 6, which is perpendicular to the axis of the roller. Draw a 90° sector profile 5 in plane 6 with a radius of 1.95 mm. The coordinates of the central corner vertex and the two intersection points of the arc and the straight line side in the coordinate system are (0, 0, 11.15), (0, 0, 9.2) and (0, 1.95, 11.15), respectively.

[0039] Subsequently, based on contour 5, additive manufacturing was performed by stretching, stretching 2.4mm in the positive x-axis direction and 0.5mm in the negative x-axis direction to form the imaginary block 2 solid with a thickness of 2.9mm.

[0040] Step 2: Material and Contact Parameter Settings. The terminal material is T2 copper, and imaginary block 1 is made of the same material. The disc body and imaginary block 2 are made of Stell steel. Material parameter settings: T2, Young's modulus is 107.9 GPa, Poisson's ratio is 0.35, yield strength is 76 MPa, hardening modulus is 398 MPa; Stell, Young's modulus is 200 GPa, Poisson's ratio is 0.3.

[0041] The contact pair consists of the outer surface of the free section of the terminal block and the surface of the side of the panel formed by rounded corners. Its contact friction coefficient is infinitely large and there is no relative slippage.

[0042] Step 3: Meshing. For the disk and free segment, a hexahedral mesh is used. For imaginary block 1, imaginary block 2, and the clamping segment, an adaptive tetrahedral mesh is used. For contact pairs, the mesh size on the disk contact surface is larger than that on the free segment contact surface. Starting from the contact point between the free segment and the disk, the mesh of the free segment gradually thins along the axial direction. The hexahedral mesh size is controlled as follows: 48 elements are defined circumferentially, 6 elements axially, and 3 elements radially for the disk; 36 elements are defined axially for the free segment, gradually increasing in density and then decreasing again, with 40 elements defined circumferentially and 4 elements radially. The resulting mesh contains 8634 elements, as shown in Figure 8, where each entity is broken down for clarity.

[0043] Step 4: Set Boundary Conditions. Set 3 load steps: Group 1: 1 load sub-step, simulating roller feed; Group 2: 20 load sub-steps, simulating the free section of the terminal block being rolled and rotated; Group 3: 1 load sub-step, simulating roller retraction.

[0044] The three-dimensional Cartesian right-handed coordinate system specified in step one is used as the reference coordinate system during motion.

[0045] In the first load step: control the linear displacement of the axis of imaginary block 2, feed direction z-axis, displacement -0.1mm, orthogonal x-axis and y-axis linear displacement are fixed at 0mm; control the linear displacement of the axis of imaginary block 1, x-axis, y-axis and z-axis are fixed at 0mm; control the linear displacement of the outer surface of the clamping section, x-axis is fixed at 0mm, and at the same time control the rotation, the rotation angle around x-axis, y-axis and z-axis are fixed at 0°.

[0046] In the second load step: control the linear displacement of the axis of imaginary block 2, feed direction z-axis, displacement maintained at -0.1mm, orthogonal x-axis and y-axis linear displacement fixed at 0mm, simultaneously control rotation, rotation angles around y-axis and z-axis fixed at 0°, 20 load substeps remain unchanged; control the linear displacement of the axis of imaginary block 1, x-axis, y-axis and z-axis all fixed at 0mm, 20 load substeps remain unchanged; control the linear displacement of the outer surface of the clamping section, x-axis fixed at 0mm, simultaneously control rotation, rotation angles around y-axis and z-axis fixed at 0°, 20 load substeps remain unchanged, rotation angle around x-axis increases with each load substep, increasing by 18° per substep, finally reaching 360°.

[0047] In the third load step: control the linear displacement of the axis of imaginary block 2, feed direction z-axis, displacement changed to 0.04mm, orthogonal x-axis and y-axis linear displacement are fixed at 0mm; control the linear displacement of the axis of imaginary block 1, x-axis, y-axis and z-axis are fixed at 0mm; control the linear displacement of the outer surface of the clamping section, x-axis fixed at 0mm, while controlling the rotation, rotation angle around y-axis and z-axis are fixed at 0°, rotation angle around x-axis is kept at 360°.

[0048] Based on the finite element model established through the above steps, calculations are performed to obtain the stress in the free segment of the terminal block, i.e., the rolled segment. Specifically, the maximum values ​​of the first principal stress, the second principal stress, the third principal stress, and the Von Mises equivalent stress in the rolled segment are read.

[0049] Based on the finite element model established in the above steps, the feed displacement of the imaginary block 2 along the z-axis in the first load step of step four was changed from -0.1mm to -0.06mm, representing a reduction in the surface rolling depth, to analyze the influence of rolling process parameters on the stress state of the terminal block after rolling. Specifically, the maximum values ​​of the first principal stress, second principal stress, third principal stress, and Von Mises equivalent stress in the rolling section were read.

[0050] Figure 9 shows the stress values ​​of each section of the terminal roll section under two rolling process parameters. It can be seen that reducing the rolling depth helps to reduce the stresses of the terminal after rolling. The terminal roll finite element model established based on the thin-walled circular tube surface rolling finite element modeling method proposed in this invention can be used to quantitatively analyze the influence characteristics of rolling process parameters on the stress state of the terminal after rolling, so as to support the research on rolling process.

[0051] Implementation Case 2: In this implementation case, a finite element model of the surface rolling of a terminal block in a thin-walled metal circular tube structure is considered. First, finite element modeling parameters are given through orthogonal experimental design. Then, based on the model, a finite element analysis of the rolling process is performed to obtain the stress of the terminal block after rolling under multiple sets of parameters, and to explore the significant influence of rolling process parameters on the stress state of the terminal block after rolling.

[0052] Using three process parameters—terminal thickness t, disc feed depth s, and disc cross-sectional shape contour fillet radius r—as the three variables in the orthogonal experiment, three levels were set, and L9(3) was adopted. 3 An orthogonal array is shown in Figure 10.

[0053] Step 1: Geometric Modeling. The terminal block consists of three parts: a clamping section, a free section, and imaginary block 1, which together form the terminal block component.

[0054] Specify a three-dimensional Cartesian right-handed coordinate system, with units in mm. The terminal block axis coincides with the x-axis. Specify the yz plane as plane 1, which is perpendicular to the terminal block axis. Draw a concentric circle outline 1 within plane 1, with its center at the origin O of the coordinate system. The inner and outer diameters are (4-2t) / (4-2t) / (4-2t). n ) and 4mm, where: n represents the orthogonal array number.

[0055] Subsequently, based on contour 1, additive manufacturing is performed by stretching, stretching 4mm in the positive x-axis direction and 8mm in the negative x-axis direction to form the terminal body before splitting, with a total axial length of 12mm.

[0056] Define a plane 2, represented as x+4=0 in the coordinate system, which is the interface between the terminal clamping section and the free section. Based on plane 2, divide the terminal into two parts: a clamping section and a free section, with axial lengths of 4mm and 8mm respectively.

[0057] Specify a plane 3, represented as x+5=0 in the coordinate system, with a distance of 1mm from plane 2. Draw a 90° sector outline 2 within plane 3, with a radius of (2-t). n The coordinates of the vertex of the central angle and the two intersection points of the arc and the straight line side in the coordinate system are (-5, 0, 0) and (-5, 2-t), respectively. n (, 0) and (-5, 0,t) n -2).

[0058] Subsequently, based on contour 2, additive manufacturing is performed by stretching the material 3mm in the negative x-axis direction to form the imaginary block 1 solid.

[0059] The roller consists of two parts: the disc body and the imaginary block 2, which together form the roller assembly.

[0060] Define a plane 4, represented as z-11.15=0 in the coordinate system, with the roller axis lying within plane 4. Define four points within plane 4 with coordinates (0, 0, 11.5), (1.9, 0, 11.5), (1.9, 6.75, 11.5), and (0, 9.15, 11.5). Connect these four points with straight lines to form a right trapezoid. For the vertex at (0, 9.15, 11.5), perform a calculation with radius r. n The rounded corners form the cross-sectional shape profile 3 of the centering front roller.

[0061] Subsequently, based on contour 3, additive manufacturing is performed by rotating 360° around a fixed axis, with the intersection of plane 4 and the xz plane as the axis, to form a coreless front roller solid, which is a frustum-shaped rotating body.

[0062] Designate the yz plane as plane 5, which is perpendicular to the roller axis. Draw a circular outline 4 within plane 5, with the center coordinates (0, 0, 11.15) and a diameter of 3.9 mm. The roller axis passes through this center.

[0063] Subsequently, based on contour 4, the coreless disc body is reduced by axial stretching to obtain the coreless disc body.

[0064] Designate the yz plane as plane 6, which is perpendicular to the axis of the roller. Draw a 90° sector profile 5 in plane 6 with a radius of 1.95 mm. The coordinates of the central corner vertex and the two intersection points of the arc and the straight line side in the coordinate system are (0, 0, 11.15), (0, 0, 9.2) and (0, 1.95, 11.15), respectively.

[0065] Subsequently, based on contour 5, additive manufacturing was performed by stretching, stretching 2.4mm in the positive x-axis direction and 0.5mm in the negative x-axis direction to form the imaginary block 2 solid with a thickness of 2.9mm.

[0066] Step 2: Material and Contact Parameter Settings. The terminal material is T2 copper, and imaginary block 1 is made of the same material. The disc body and imaginary block 2 are made of Stell steel. Material parameter settings: T2, Young's modulus is 107.9 GPa, Poisson's ratio is 0.35, yield strength is 76 MPa, hardening modulus is 398 MPa; Stell, Young's modulus is 200 GPa, Poisson's ratio is 0.3.

[0067] The contact pair consists of the outer surface of the free section of the terminal block and the surface of the side of the panel formed by rounded corners. Its contact friction coefficient is infinitely large and there is no relative slippage.

[0068] Step 3: Meshing. For the disk and free segment, hexahedral meshing is used. For imaginary block 1, imaginary block 2, and the clamping segment, adaptive tetrahedral meshing is used. For contact pairs, the mesh size of the disk contact surface is larger than the mesh size of the free segment contact surface. Starting from the contact point between the free segment and the disk, the mesh of the free segment gradually thins along the axial direction. The control requirements for the hexahedral mesh size and the number of model elements are shown in Figure 11. The axial direction of the free segment changes from sparse to dense and then back to sparse.

[0069] Step 4: Set Boundary Conditions. Set 3 load steps: Group 1: 1 load sub-step, simulating roller feed; Group 2: 20 load sub-steps, simulating the free section of the terminal block being rolled and rotated; Group 3: 1 load sub-step, simulating roller retraction.

[0070] The three-dimensional Cartesian right-handed coordinate system specified in step one is used as the reference coordinate system during motion.

[0071] In the first load step: control the linear displacement of the imaginary block 2 along its axis, feed direction z-axis, displacement -s n The linear displacements of the orthogonal x-axis and y-axis are fixed at 0 mm; the linear displacement of the axis of imaginary block 1 is controlled, with the x-axis, y-axis and z-axis all fixed at 0 mm; the linear displacement of the outer surface of the clamping section is controlled, with the x-axis fixed at 0 mm, while the rotation is controlled, with the rotation angles around the x-axis, y-axis and z-axis all fixed at 0°.

[0072] In the second load step: control the linear displacement of the imaginary block 2 along its axis, feed in the z-axis direction, and maintain the displacement at -s. n The linear displacement of the orthogonal x-axis and y-axis is fixed at 0 mm, while the rotation is controlled, with the rotation angles around the y-axis and z-axis both fixed at 0°, and the 20 load substeps remain unchanged; the linear displacement of the axis of imaginary block 1 is controlled, with the x-axis, y-axis, and z-axis all fixed at 0 mm, and the 20 load substeps remain unchanged; the linear displacement of the outer surface of the clamping section is controlled, with the x-axis fixed at 0 mm, while the rotation is controlled, with the rotation angles around the y-axis and z-axis both fixed at 0°, and the 20 load substeps remain unchanged, while the rotation angle around the x-axis increases with each load substep, increasing by 18° per substep, finally reaching 360°.

[0073] In the third load step: control the linear displacement of the axis of imaginary block 2, feed direction z-axis, displacement changed to 0.04mm, orthogonal x-axis and y-axis linear displacement are fixed at 0mm; control the linear displacement of the axis of imaginary block 1, x-axis, y-axis and z-axis are fixed at 0mm; control the linear displacement of the outer surface of the clamping section, x-axis fixed at 0mm, while controlling the rotation, rotation angle around y-axis and z-axis are fixed at 0°, rotation angle around x-axis is kept at 360°.

[0074] Based on the finite element model established through the above steps, calculations are performed to obtain the stress in the free segment of the terminal block, i.e., the rolled segment. Specifically, the first principal stress σ1, the second principal stress σ2, the third principal stress σ3, and the Von Mises equivalent stress σ are read from the rolled segment. v The maximum value.

[0075] Figure 12 shows the stress values ​​of the rolling section of the terminal block under various working conditions in the orthogonal experiment. In this figure, I, II, and III represent the sum of the corresponding stress values ​​at the 1st, 2nd, and 3rd levels for each variable, respectively. The subscripts refer to parameters σ1, σ2, σ3, or σ... v For example, for variable t, I v =580MPa represents σ v The sum of stress values ​​in groups 1, 2, and 3 (142 + 200 + 238) corresponds to the first level of t. R is the range of I, II, and III, with subscripts referring to parameters σ1, σ2, σ3, or σ v For example, for variable t, Rv =100MPa.

[0076] Based on the orthogonal experimental results, the significant influencing factors affecting the stress after rolling of the terminal block are analyzed: the feed depth s of the disc is stronger than the terminal block thickness t and the fillet radius r of the disc cross-sectional shape, while the difference between the latter two is relatively small. The finite element model for terminal block rolling established based on the finite element modeling method for surface rolling of thin-walled circular tube structures proposed in this invention can be used to parametrically and quantitatively analyze the influence characteristics of rolling process parameters on the stress state of the terminal block after rolling, for example, by employing orthogonal experimental methods to support the research on the rolling process.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A finite element modeling method for surface rolling of thin-walled circular tube structures, characterized in that, The process includes the following steps: Model construction: Constructing geometric models of two solid entities, a thin-walled circular tube and a roller. The model of the thin-walled circular tube includes a clamping section, a free section, and imaginary block 1; the model of the roller includes a disc body and imaginary block 2. The axis of the disc body is parallel to the axis of the thin-walled circular tube, and the distance between the edge of the disc body and the surface of the thin-walled circular tube is not less than 0. Parameter setting: Setting material parameters and contact parameters for the free section, clamping section, and imaginary block 1 of the thin-walled circular tube, as well as the disc body and imaginary block 2 of the roller. Meshing: Hexahedral meshing is used for the disk body and free section; adaptive meshing is used for imaginary block 1, imaginary block 2, and clamping section; for contact pairs, the mesh size of the disk contact surface is larger than that of the free section contact surface; Boundary condition settings: Three load steps are set, each load step has at least one load substep; the first set simulates the roller feed, the second set simulates the rotation of the thin-walled circular tube under rolling pressure, and the third set simulates the roller retraction; Model solution: The finite element model established in the above steps is used for calculation and solution to obtain the stress in the free section.

2. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 1, characterized in that, In the model building step, the model building process of the thin-walled circular tube is as follows: Specify a plane 1 perpendicular to the axis of the thin-walled circular tube, and draw a concentric circle outline in plane 1 to represent the cross-section of the thin-walled circular tube. The inner circle diameter of the concentric circle outline is the inner diameter of the thin-walled circular tube, and the outer circle diameter is the outer diameter of the thin-walled circular tube. Subsequently, based on the concentric circle outline, additive manufacturing is performed by axial stretching, and the total length of the additive manufacturing is the axial length of the thin-walled circular tube.

3. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 1, characterized in that, In the model construction step, the clamping section and the free section are determined as follows: a plane 2 perpendicular to the axis of the thin-walled circular tube is specified, and the interface between the clamping section and the free section of the thin-walled circular tube is within this plane 2.

4. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 3, characterized in that, In the model construction step, the construction method of imaginary block 1 is as follows: Specify a plane 3 parallel to plane 2, with a distance from plane 2 of 10% to 40% of the axial length of the clamping segment, and pass through the clamping segment but not through the free segment; draw a 90° sector profile 1 in plane 3, with a radius equal to the inner radius of the thin-walled circular tube, and the vertex of the central corner located on the axis of the thin-walled circular tube; then, based on the sector profile 1, additive manufacturing is performed by axial stretching, with the total additive length being the length of the clamping segment minus the distance between plane 3 and plane 2, to form an imaginary block 1 solid tangent to the inner surface of the clamping segment. The end face of imaginary block 1 perpendicular to its own axis should be in the same plane as the end face of the clamping segment perpendicular to its own axis.

5. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 4, characterized in that, In the model building steps, the disk body is constructed as follows: A plane 4 is specified, perpendicular to planes 2 and 3. Simultaneously, the plane formed by the roller axis and the thin-walled circular tube axis is also perpendicular to plane 4. A shape profile is drawn within plane 4, representing the cross-sectional shape of the roller before core removal. Subsequently, based on this shape profile, additive material is added by rotating 360° around a fixed axis to form the solid roller before core removal. A plane 5 is specified, perpendicular to the roller axis. A circular profile is drawn within plane 5, with a diameter equal to the core removal diameter of the roller, and the roller axis passes through the center of the circular profile. Subsequently, based on the circular profile, subtractive material is added by axial stretching to core the roller before core removal, obtaining the solid disk body.

6. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 5, characterized in that, Specify a plane 6 perpendicular to the axis of the roller, and draw a 90° sector outline 2 in plane 6 with a radius equal to the radius of the roller's center and the vertex of the central corner on the axis of the roller; then, based on the sector outline 2, add material by axial stretching, with the total length of the additive material being greater than the thickness of the roller body, to form a solid imaginary block 2. The two end faces of the imaginary block 2 perpendicular to its own axis extend axially beyond the two end faces of the roller body perpendicular to its own axis.

7. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 1, characterized in that, In the parameter setting step, the material parameters set for the thin-walled circular tube include Young's modulus, Poisson's ratio, yield strength, and hardening modulus, while the material parameters set for the roller include Young's modulus and Poisson's ratio; and the Young's modulus of the roller material must not be lower than the Young's modulus of the thin-walled circular tube material.

8. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 1, characterized in that, In the parameter setting step, the contact parameters set include: the contact pair consists of the outer surface of the free segment and the side surface of the disk, the contact form is non-slip friction with a friction coefficient considered to be infinite, and the initial spacing of the contact pair in the geometric model is 0.

9. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 1, characterized in that, In the boundary condition setting step, the first load step includes: applying a linear displacement in the feed direction to the axis edge of imaginary block 2, while fixing the linear displacement in the other two orthogonal directions; fixing the total displacement to the axis edge of imaginary block 1; fixing the rotation around the axis edge of imaginary block 1 and its two orthogonal directions to the outer surface of the clamping section, while fixing the linear displacement in the direction of the axis edge of imaginary block 1.

10. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 1, characterized in that, In the boundary condition setting step, the second load step includes: for the axis edge of imaginary block 2, only the rotational degree of freedom around the axis is retained, the rotation in two orthogonal directions around the axis is fixed, and at the same time, the linear displacement of the axis and its two orthogonal directions is fixed, while maintaining the linear displacement in the feed direction generated by the first load step; for the axis edge of imaginary block 1, the total displacement is fixed; for the outer surface of the clamping section, the linear displacement in the direction of the axis edge of imaginary block 1 is fixed, and at the same time, the rotation angle around the axis edge of imaginary block 1 is applied in the sub-load sub-step, and the rotation in the two orthogonal directions around the axis edge of imaginary block 1 is fixed.

11. The finite element modeling method for surface rolling of a thin-walled circular tube structure as described in claim 1, characterized in that, In the boundary condition setting step, the third load step includes: applying a linear displacement in the exit direction to the axis edge of imaginary block 2, while fixing the linear displacement in the other two orthogonal directions; fixing the total displacement to the axis edge of imaginary block 1; fixing the rotation about the axis edge of imaginary block 1 and its two orthogonal directions to the outer surface of the clamping section, while maintaining the rotation angle about the axis edge of imaginary block 1 generated by the second load step, while fixing the linear displacement in the direction of the axis edge of imaginary block 1.

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