Microcapillary drawing forming calculation method and system based on finite element analysis

Abstract

The invention discloses a microcapillary drawing forming calculation method and system based on finite element analysis, and relates to the technical field of metal processing. Comprising the following steps: acquiring microcapillary parameters and drawing die parameters, and establishing a geometric model based on the microcapillary parameters and a drawing die; selecting a constitutive model suitable for material deformation to determine material attributes, and dividing finite element grids in combination with a geometric model; setting constraint conditions for the grids, determining grid data, and determining fatigue points based on the grid data; determining upper and lower limits of a fatigue point load based on the fatigue point and the grid data corresponding to the fatigue point; and determining the drawing force based on the fatigue point load upper and lower limits. According to the method, high-precision prediction of the fatigue point in the microcapillary drawing process is achieved, the cost can be reduced, it is guaranteed that the forming quality is controllable, and the rate of finished products is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing, and in particular to a micro-tube drawing forming calculation method and system based on finite element analysis. Background Art

[0002] Microtubes are widely used in various industries. When the wall thickness is reduced to less than 100μm, drawing and forming becomes extremely difficult, and the forming quality is difficult to guarantee. In recent years, due to the demand, some difficult-to-deform materials have been applied to thin-walled microtubes, making processing and manufacturing more difficult and prone to fracture and failure. For example, the friction force accounts for a large proportion in the microtube drawing process, resulting in large drawing forces, easy fracture of the tube during the drawing process, limited deformation per pass, and a large number of drawing passes, with many annealing times between passes. Multiple heat treatments are required in the middle, which is inefficient and costly. In addition, the wall thickness uniformity and surface quality are difficult to control, and in some cases, manufacturing is even impossible.

[0003] Therefore, it is an urgent problem for those skilled in the art to provide a micro-tube drawing forming calculation method and system based on finite element analysis to solve the difficulties existing in the prior art. Summary of the Invention

[0004] In view of this, the present invention provides a microtube drawing forming calculation method and system based on finite element analysis, which realizes high-precision prediction of fatigue points in the microtube drawing process, can reduce costs, ensure controllable forming quality, and improve the yield rate.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A microtube drawing forming calculation method based on finite element analysis includes the following steps:

[0007] Obtaining microtube parameters and drawing die parameters, and establishing a geometric model based on the microtube parameters and the drawing die;

[0008] Select a constitutive model suitable for material deformation to determine material properties, and divide the finite element mesh based on the geometric model;

[0009] Set constraints on the grid, determine the grid data, and determine the fatigue point based on the grid data;

[0010] Determine the upper and lower limits of fatigue point load based on the fatigue point and the mesh data corresponding to the fatigue point;

[0011] Determine the pull-out force based on the upper and lower fatigue point load limits.

[0012] Optionally, finite element meshing includes:

[0013] Determine the location of high stress areas in the geometric model and perform initial meshing on the geometric model;

[0014] The initial mesh is optimized based on multiple reference values ​​obtained based on the location of the high stress area to obtain the finite element mesh.

[0015] Optionally, determining the grid data includes:

[0016] Determine the loading point for microtube pulling experiments;

[0017] Determine the loading load corresponding to the working condition of the loading point, set the theoretical upper and lower limits of the load based on the inequality constraints that control the section error, and obtain the theoretical load of the loading point;

[0018] The finite element mesh data is determined based on the loading point location and the theoretical load of the loading point.

[0019] Optionally, it also includes automatic error correction of the finite element mesh and detection of the completeness and coordination of key information in the finite element mesh.

[0020] Optionally, determining fatigue points includes:

[0021] Obtaining finite element meshes and finite element mesh data, and determining fatigue results for each mesh based on the finite element mesh data;

[0022] Select a grid as a free grid and compare the fatigue results of the free grid with those of the adjacent free grids. If the fatigue results of all adjacent free grids are greater than the fatigue result of the current free grid, the current free grid is recorded as S. If the fatigue results of all adjacent free grids are less than the fatigue result of the current free grid, the current free grid is recorded as B. If the fatigue results of the adjacent free grids are both less than and greater than the fatigue results of the current free grid, the current free grid is recorded as I. If the fatigue results of the adjacent free grids are equal to the fatigue results of the current free grid, replace the free grid and recalculate.

[0023] The free mesh marked as B is regarded as the fatigue point.

[0024] Optionally, determining upper and lower limits of fatigue point loads includes:

[0025] Obtain the grid data and grid position of the free grid denoted as B, the grid data including the theoretical loading load of grid B;

[0026] The fatigue point theoretical load is determined based on the theoretical loading load of the entire grid B.

[0027] A micro-tube drawing forming calculation system based on finite element analysis, which executes any of the above-mentioned micro-tube drawing forming calculation methods based on finite element analysis, comprising a model building module, a meshing module, a fatigue point determination module, a load determination module and a solution module connected in sequence;

[0028] Model building module: obtains microtube parameters and drawing die parameters, and builds a geometric model based on the microtube parameters and drawing die;

[0029] Meshing module: Select the constitutive model suitable for material deformation to determine the material properties, and divide the finite element mesh based on the geometric model;

[0030] Fatigue point determination module: sets constraints on the grid, determines grid data, and determines fatigue points based on the grid data;

[0031] Load determination module: determines the upper and lower limits of fatigue point load based on the fatigue point and the mesh data corresponding to the fatigue point;

[0032] Solution module: Determine the pull-out force based on the upper and lower limits of the fatigue point load.

[0033] It can be seen from the above technical solution that compared with the existing technology, the present invention provides a micro-tube drawing forming calculation method and system based on finite element analysis, which has the following beneficial effects: 1) The present invention can avoid the situation of excessive local strain during the drawing process of the component and ensure safety; 2) The present invention realizes high-precision prediction of fatigue points during the micro-tube drawing process, which can reduce costs, ensure controllable forming quality, and improve the yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0035] Figure 1 This is a flow chart of a microtube drawing calculation method based on finite element analysis disclosed in the present invention;

[0036] Figure 2 This is a block diagram of a microtube drawing and forming calculation system based on finite element analysis disclosed in the present invention. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] Reference Figure 1 As shown, the present invention discloses a micro-tube drawing forming calculation method based on finite element analysis, comprising the following steps:

[0039] Obtaining microtube parameters and drawing die parameters, and establishing a geometric model based on the microtube parameters and the drawing die;

[0040] Select a constitutive model suitable for material deformation to determine material properties, and divide the finite element mesh based on the geometric model;

[0041] Set constraints on the grid, determine the grid data, and determine the fatigue point based on the grid data;

[0042] Determine the upper and lower limits of fatigue point load based on the fatigue point and the mesh data corresponding to the fatigue point;

[0043] Determine the pull-out force based on the upper and lower fatigue point load limits.

[0044] Furthermore, establishing the geometric model includes determining the microtube parameters and drawing die parameters. The microtube parameters include the initial outer diameter, wall thickness, material density, elastic modulus and Poisson's ratio. The drawing die parameters include the reduction angle, sizing band length, outlet diameter and surface friction coefficient. The axisymmetric geometric model is constructed using NURBS curves.

[0045] Furthermore, the finite element meshing includes:

[0046] Determine the location of high stress areas in the geometric model and perform initial meshing on the geometric model;

[0047] The initial mesh is optimized based on multiple reference values ​​obtained based on the location of the high stress area to obtain the finite element mesh.

[0048] Furthermore, determining the grid data includes:

[0049] Determine the loading point for microtube pulling experiments;

[0050] Determine the loading load corresponding to the working condition of the loading point, set the theoretical upper and lower limits of the load based on the inequality constraints that control the section error, and obtain the theoretical load of the loading point;

[0051] The finite element mesh data is determined based on the loading point location and the theoretical load of the loading point.

[0052] Specifically, based on the structural form of the microtube and the theoretical load distribution under typical working conditions, the loading nodes of the component fatigue test are determined, and each loading node is equivalent to multiple loading points. Each loading point includes multiple loading nodes. The position of the fatigue test loading point is determined, and the distribution ratio of each loading node in each loading point is obtained. The loading load between each loading node and the corresponding loading point can be converted by equivalence.

[0053] Furthermore, it also includes automatic error correction of the finite element mesh and detection of the completeness and coordination of key information in the finite element mesh.

[0054] Specifically, automatic error correction also includes: when it is found that key information of the finite element mesh is missing, the missing key information is adaptively filled based on the adjacent mesh data;

[0055] Detect the geometric information of the unit grid and determine whether the geometric point coding is repeated or confused. If so, re-encode it;

[0056] Check whether the unit grid has corresponding working condition information and determine whether the working condition information corresponds correctly. If not, re-compare and confirm.

[0057] Furthermore, the fatigue result of each free surface can be the fatigue result of the center point of the free surface, or the fatigue result of the node of the free surface. For the fatigue of the center point of the free surface, a measurement coordinate system with the center point of the surface as the coordinate origin and the normal direction of the surface center as the z-axis can be calculated based on the free surface mesh data. The finite element results are then converted to this coordinate system, and then an appropriate fatigue algorithm is selected to calculate and search for the worst fatigue result or safety factor and direction on the XY plane. The direction is expressed as the angle with the X-axis of the measurement coordinate system.

[0058] Furthermore, if fatigue points are searched based on fatigue result damage values, the point with the largest damage value is the fatigue point; if fatigue points are searched based on fatigue result safety factor values, the point with the smallest safety factor value is the fatigue point.

[0059] Furthermore, determining fatigue points includes:

[0060] Obtaining finite element meshes and finite element mesh data, and determining fatigue results for each mesh based on the finite element mesh data;

[0061] Select a grid as a free grid and compare the fatigue results of the free grid with those of the adjacent free grids. If the fatigue results of all adjacent free grids are greater than the fatigue result of the current free grid, the current free grid is recorded as S. If the fatigue results of all adjacent free grids are less than the fatigue result of the current free grid, the current free grid is recorded as B. If the fatigue results of the adjacent free grids are both less than and greater than the fatigue results of the current free grid, the current free grid is recorded as I. If the fatigue results of the adjacent free grids are equal to the fatigue results of the current free grid, replace the free grid and recalculate.

[0062] The free mesh marked as B is regarded as the fatigue point.

[0063] Furthermore, the upper and lower limits of fatigue point loads are determined as follows:

[0064] Obtain the grid data and grid position of the free grid denoted as B, the grid data including the theoretical loading load of grid B;

[0065] The fatigue point theoretical load is determined based on the theoretical loading load of the entire grid B.

[0066] Specifically, the loading load of each loading point in each working condition is used as a variable, and the theoretical total load and total moment are used for inequality constraints, and the control section error is used for inequality constraints, including inequality constraints on the control section bending moment, shear force, and torque errors, as well as upper and lower limits of the loading load of each loading point. The target response error of the component fatigue test and the theoretical state finite element model is used as the target variable to obtain the loading load of each loading point, and then the loading load of each free grid is obtained. The genetic algorithm is used for calculation, and for each generation of loading load population, the finite element model load card is iterated. The finite element analysis of the component fatigue test finite element model is performed using MSC.Nastran software, and the assessment target data is extracted from the result file. A new generation of loading load population is generated through the selection, crossover and mutation of the loading load population, and the component fatigue test finite element model is continuously iteratively analyzed and the assessment target data is extracted, so that the loading load of each free grid gradually converges to the optimal solution.

[0067] A micro-tube drawing forming calculation system based on finite element analysis, which executes any of the above-mentioned micro-tube drawing forming calculation methods based on finite element analysis, referring to Figure 2 As shown, it includes a model building module, a meshing module, a fatigue point determination module, a load determination module and a solution module connected in sequence;

[0068] Model building module: obtains microtube parameters and drawing die parameters, and builds a geometric model based on the microtube parameters and drawing die;

[0069] Meshing module: Select the constitutive model suitable for material deformation to determine the material properties, and divide the finite element mesh based on the geometric model;

[0070] Fatigue point determination module: sets constraints on the grid, determines grid data, and determines fatigue points based on the grid data;

[0071] Load determination module: determines the upper and lower limits of fatigue point load based on the fatigue point and the mesh data corresponding to the fatigue point;

[0072] Solution module: Determine the pull-out force based on the upper and lower limits of the fatigue point load.

[0073] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A microtube drawing calculation method based on finite element analysis, characterized in that: The following steps are involved: Obtaining microtube parameters and drawing die parameters, and establishing a geometric model based on the microtube parameters and the drawing die; Select a constitutive model suitable for material deformation to determine material properties, and divide the finite element mesh based on the geometric model; Set constraints on the grid, determine the grid data, and determine the fatigue point based on the grid data; Determine the upper and lower limits of fatigue point load based on the fatigue point and the mesh data corresponding to the fatigue point; Determine the pull-out force based on the upper and lower fatigue point load limits.

2. The microtube drawing calculation method based on finite element analysis according to claim 1 is characterized in that: Finite element meshing includes: Determine the location of high stress areas in the geometric model and perform initial meshing on the geometric model; The initial mesh is optimized based on multiple reference values ​​obtained based on the location of the high stress area to obtain the finite element mesh.

3. The microtube drawing calculation method based on finite element analysis according to claim 1, characterized in that: Determine the grid data including: Determine the loading point for microtube pulling experiments; Determine the loading load corresponding to the working condition of the loading point, set the theoretical upper and lower limits of the load based on the inequality constraints that control the section error, and obtain the theoretical load of the loading point; The finite element mesh data is determined based on the loading point location and the theoretical load of the loading point.

4. The microtube drawing calculation method based on finite element analysis according to claim 3 is characterized in that It also includes automatic error correction of finite element meshes and detection of the completeness and coordination of key information in finite element meshes.

5. The microtube drawing calculation method based on finite element analysis according to claim 1, characterized in that: Identifying fatigue points includes: Obtaining finite element meshes and finite element mesh data, and determining fatigue results for each mesh based on the finite element mesh data; Select a grid as a free grid and compare the fatigue results of the free grid with those of the adjacent free grids. If the fatigue results of all adjacent free grids are greater than the fatigue result of the current free grid, the current free grid is recorded as S. If the fatigue results of all adjacent free grids are less than the fatigue result of the current free grid, the current free grid is recorded as B. If the fatigue results of the adjacent free grids are both less than and greater than the fatigue results of the current free grid, the current free grid is recorded as I. If the fatigue results of the adjacent free grids are equal to the fatigue results of the current free grid, replace the free grid and recalculate. The free mesh marked as B is regarded as the fatigue point.

6. The microtube drawing calculation method based on finite element analysis according to claim 5, characterized in that: Determining the upper and lower limits of fatigue point loads includes: Obtain the grid data and grid position of the free grid denoted as B, the grid data including the theoretical loading load of grid B; The fatigue point theoretical load is determined based on the theoretical loading load of the entire grid B.

7. A microtube drawing calculation system based on finite element analysis, for implementing the microtube drawing calculation method based on finite element analysis as described in any one of claims 1 to 6, comprising a model building module, a meshing module, a fatigue point determination module, a load determination module, and a solution module connected in sequence; Model building module: obtains microtube parameters and drawing die parameters, and builds a geometric model based on the microtube parameters and drawing die; Meshing module: Select the constitutive model suitable for material deformation to determine the material properties, and divide the finite element mesh based on the geometric model; Fatigue point determination module: sets constraints on the grid, determines grid data, and determines fatigue points based on the grid data; Load determination module: determines the upper and lower limits of fatigue point load based on the fatigue point and the mesh data corresponding to the fatigue point; Solution module: Determine the pull-out force based on the upper and lower limits of the fatigue point load.

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