Method for monitoring wrinkling of solid elements in a simulation of a forming process of a sheet metal rotary body part

Abstract

A kind of plate rotary body part simulation forming process entity unit wrinkle monitoring method, by constructing rotary body part forming simulation model and carrying out sheet metal deep drawing forming process simulation, extract the surface geometric information of rotary body part in simulation result, obtain the degree of surface fluctuation by converting coordinate system and comparison calculation, and then accumulate to obtain overall wrinkling evaluation.The present application does not need to establish the relationship between strain and material wrinkling instability, and obtains the micro-wrinkling on the surface of the part in the deformation simulation process by geometric method, directly judges the fluctuation of the surface of the finite element model part according to the wrinkling in the forming process of the part, and efficiently completes the fluctuation (wrinkling) comprehensive judgment of the simulation forming surface of the whole rotary body part.

Description

Technical Field

[0001] This invention relates to a technology in the field of sheet metal machining, specifically a method for monitoring wrinkling of solid units in the simulation forming process of sheet metal rotating parts. Background Technology

[0002] Sheet metal deep drawing is commonly used to manufacture cylindrical and other rotating parts. An initial circular blank is drawn into a die using a deep drawing punch, gradually deforming the blank from a sheet into the desired part. During deep drawing, internal stress is mainly distributed within the sheet metal surface, thus it can generally be assumed to be a plane stress problem, and wrinkling is usually determined using shell elements. Many commercial finite element software programs now offer wrinkling criteria based on the stress state of shell elements, offering high computational efficiency. However, some sheet metal forming processes involve active wall thinning or complex contact problems, requiring the use of solid elements for mesh discretization of the deformable body. Compared to shell elements, solid elements consume more computational resources, and since multiple solid elements are typically present in the thickness direction, wrinkling criteria similar to those used in shell elements cannot be directly applied to determine wrinkling. In such cases, manual post-processing analysis is often necessary to determine whether wrinkling has occurred from the perspective of the overall part geometry. For minor wrinkling, manual assessment is often insufficient. This method is not only very inaccurate and inefficient, but it also cannot be integrated into the automatic adjustment process of process parameters, and cannot achieve dynamic elimination of wrinkling by automatically optimizing process parameters. Summary of the Invention

[0003] This invention addresses the shortcomings of existing simulations, which struggle to effectively identify and determine whether parts are wrinkled. These simulations require obtaining the critical compressive stress at which wrinkling instability occurs during material spinning before establishing a predictive relationship, thus failing to predict wrinkling defects during the forming process. The invention proposes a solid element wrinkling monitoring method for simulated forming of sheet metal rotating parts. This method eliminates the need to establish an additional relationship between strain and material wrinkling instability. It uses geometric methods to obtain minute wrinkles appearing on the part surface during deformation simulation. Wrinkles appearing during part forming are directly assessed by judging the surface undulations of the finite element model, efficiently completing a comprehensive judgment of the undulations (wrinkles) on the entire simulated forming surface of the rotating part.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a solid unit wrinkling monitoring method for the simulated forming process of sheet metal rotary parts. The method involves constructing a forming simulation model of the rotary part and simulating the sheet metal deep drawing process. The surface geometric information of the rotary part is extracted from the simulation results. The degree of surface undulation is obtained by transforming the coordinate system and comparing calculations, and then the overall wrinkling evaluation is obtained.

[0006] The aforementioned simulation model for the forming of a rotating part is a finite element model created in general-purpose commercial finite element software. Based on the actual forming process parameters of the rotating part, a working mold is set and its motion is defined to simulate the forming process. The contact conditions between the slab and the mold are set according to actual lubrication conditions. When meshing the slab with solid elements, at least three elements should be present in the thickness direction. Based on the mesh information, the node numbers of the solid elements on the upper and lower surfaces of the slab are determined, forming surface node sets, defined as the upper surface set and the lower surface set, respectively. The coordinates of the nodes in the upper and lower surface sets are output as they change during the forming process. During the finite element calculation, it should be ensured that no mesh re-generating or node number rearrangement occurs.

[0007] The aforementioned sheet metal deep drawing process simulation refers to the process of using a general commercial finite element software solver to calculate and solve the simulation model of the rotating part to obtain the deformation of the rotating part under the forming conditions set in the model.

[0008] The aforementioned surface geometry information of the rotating part refers to obtaining the length of the projected curve of the rotating part's surface after wrinkling occurs by transforming the coordinate system. Specifically, based on the forming process simulation results obtained from the rotating part forming simulation model, the Cartesian coordinate system is converted to a cylindrical coordinate system, and a one-to-one correspondence of points located within and outside the radius r of the rotating part's rotation axis is selected. Points precisely located at radius r are obtained by interpolating virtual points. The length of the projected line on the rotating part's surface is calculated by sequentially connecting the virtual points.

[0009] The aforementioned coordinate system transformation refers to converting the surface node coordinate information during sheet metal forming simulation from a Cartesian coordinate system to a cylindrical coordinate system. Specifically, after the simulation ends, the coordinate information of the predefined output set of upper and lower surface nodes is obtained, which must meet the requirement of one-to-one correspondence between nodes and coordinates. A ρθz coordinate system is established with the rotation axis as the z-axis direction. The extracted node coordinate information is transformed so that each node number corresponds to two coordinate values, namely Cartesian coordinates and cylindrical coordinates. Based on the selected scanning radius r, the surface node set is divided into two parts: nodes within the scanning radius r and nodes outside the scanning radius r. Using the node ρθz cylindrical coordinates, points located within a length Δ on both sides of the scanning radius are initially screened, i.e., r-Δ<ρ<r+Δ, where Δ should be greater than 1.5 times the average side length of the upper surface unit. The initially screened node sets are denoted as p1, the set of nodes to be judged within radius r, and p2, the set of nodes to be judged outside radius r. The θ coordinates are traversed in the set of nodes to be judged, and the nearest node pt is found in p1 and p2. 1，θ , and pt 2，θ The corresponding nodes are combined and stored. This is done using pt. 1，θ , with pt 2，θThe node combination is used to obtain the virtual node p that is exactly located at the scan radius r using interpolation. v1，θ Similar processing is performed on all node combinations to obtain a set of virtual nodes. This set of virtual nodes is entirely located at the scan radius r. After sorting these virtual nodes according to their θ coordinates and connecting them end-to-end, the surface curve φ at the scan radius r can be obtained. i The surface curve φ is formed by the combination of virtual nodes. i The total length S of the surface curve can be calculated.

[0010] The comparative calculation refers to: obtaining the undulation information of the surface of the rotating part at a position of radius r from the rotation axis, comparing it with the standard circumference of a circle without wrinkles, and calculating the degree of surface undulation. Specifically, it involves determining whether the length of the surface curve formed by the combination of virtual nodes is greater than the theoretical circumference.

[0011] The overall wrinkling evaluation refers to: based on the actual design of the rotating part, determining the area r1≤r≤r2 that needs to be judged for wrinkling; selecting a scanning radius step size Δr; and by traversing the area that needs to be judged for wrinkling, extracting the surface undulation at the scanning radius to obtain the corresponding wrinkling surface undulation judgment factor. The overall surface undulation of the part is obtained by integration. Where r is the radius from the axis of rotation.

[0012] This invention relates to a system for implementing the above-mentioned method, comprising: a simulation post-processing node coordinate extraction unit, a wrinkling judgment unit, a region scanning unit, and a wrinkling evaluation unit, wherein: the simulation post-processing node coordinate extraction unit extracts the surface node coordinate information of the rotating part after the forming simulation is completed using a finite element post-processing method based on the simulation results; the wrinkling judgment unit, based on the obtained surface node coordinate information, obtains the curve length of the set of points from the surface of the rotating part to the rotation axis with radius r through coordinate transformation and point filtering, and compares it with the ideal curve length to obtain the degree of wrinkling; the region scanning unit obtains wrinkling information within a certain area of ​​the part surface by continuously calling the wrinkling judgment unit; and the wrinkling evaluation unit obtains wrinkling evaluation indicators for the entire part forming process based on the wrinkling information within the part surface area obtained by the region scanning unit.

[0013] Technical effect

[0014] This invention extracts surface node information from the calculation results of a solid element-based simulation model of a rotating part to determine the occurrence of wrinkling during the forming simulation process from a geometric perspective, achieving flexible wrinkling judgment and evaluation. Compared with existing technologies, this invention solves the problem that solid elements cannot determine wrinkling based on stress state, and is applicable to the forming simulation of rotating parts using solid elements. Although this invention primarily focuses on wrinkling judgment using solid elements, it can also be transferred to wrinkling judgment using geometrically based plate and shell elements. The method of this invention requires no determination of other criteria, is simple to operate, calculates quickly, and has high flexibility for expansion. It can serve as a finite element simulation auxiliary tool for judging wrinkling and optimizing processes when solid elements must be used in the deep drawing simulation of rotating parts. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the wrinkle detection method;

[0016] Figure 2 This is a schematic diagram illustrating the principle of determining wrinkles in solid units based on geometric elements.

[0017] Figure 3 A schematic diagram showing the spatial positioning assembly of a liquid-filled deep drawing rigid body mold.

[0018] Figure 4 A schematic diagram illustrating the node search method for obtaining points near the projection radius r;

[0019] Figure 5 A schematic diagram illustrating a method for calculating virtual points by interpolation of nodes inside and outside the projection radius r;

[0020] Figure 6 This is a schematic diagram showing the results of wrinkle assessment for integral rotating parts. Detailed Implementation

[0021] like Figure 1 As shown in this embodiment, a method for judging wrinkling during the simulation of sheet metal liquid-filled deep drawing includes:

[0022] 1) Construct a simulation model for the forming of a rotating part, specifically including:

[0023] 1.a) Constructing a basic simulation model: such as Figure 3 As shown, using commercial finite element software, models of the punch, blank holder, blank, and die were constructed sequentially based on the liquid-filling deep drawing process and their spatial positions. The punch was set to descend at a uniform speed, the blank holder generated a fixed blank holder force of 300 kN, and the liquid pressure in the liquid chamber was set to 6 MPa throughout the stroke. To simplify the calculation, a quarter-scale model of the complete model was used for modeling and calculation.

[0024] In addition to spatial location, based on contact characteristics, the friction coefficient is set to 0.12, and the normal contact condition is set to hard contact. After completing the above model construction, the part blank is meshed to ensure that there are at least 3 mesh layers in the thickness direction.

[0025] Mesh remapping and node number rearrangement are not allowed during finite element calculations.

[0026] 1.b) Data Output Preparation: Based on the mesh information of the formed blank, establish the node sets of the upper and lower surfaces. In this embodiment, only the surface undulation of the upper surface is extracted as the information input for wrinkling judgment. Therefore, when setting the data output, only the coordinates of the node set of the upper surface can be output.

[0027] 2) Extract the surface geometric information of the rotating part from the simulation results, specifically including:

[0028] 2.a) Extract the surface node coordinates from the simulation results;

[0029] 2.b) Convert the aforementioned surface node coordinates from Cartesian coordinates to cylindrical coordinates, wherein the z-axis direction is collinear with the rotation axis of the rotating part, and the xOy plane in the Cartesian coordinate system can be used as the ρOθ plane, while the origin of the coordinate system remains unchanged from the z-axis.

[0030] 2.c) Based on the actual mesh size L, for each node (ρ) in the upper surface set i θ i , z i Set the filtering bandwidth range Δ = 1.5L, i.e., r - 1.5L = r - Δ ≤ ρ ≤ r + Δ = r + 1.5L, and filter the set of nodes within this bandwidth range. Based on the relationship between ρ and r, divide the set of nodes within the bandwidth range into a set PT of nodes whose radial coordinate ρ is less than r. r The set of nodes PT with radial coordinate ρ greater than r R Traverse PT r and PT R The θ coordinates of the middle node are recorded in the corresponding θ i A set of points (ρ) that are closer together in the coordinate system to the two sets. p1 θ p1 , z p1 )∈PT r and (ρ) p2 θ p2 , z p2 )∈PT R .

[0031] 2.d) Based on the characteristic that the radial coordinates ρ of the two points are greater than r and less than r respectively, the virtual point (r, θ) can be obtained by interpolation. pt0 , z pt0After sorting the virtual points according to their θ coordinates, connect the first and last points to obtain the surface curve φ at the radius r of the simulated rotating part. i .

[0032] 2.e) Calculate the surface curve φ i The perimeter of the atom is denoted as C. i By comparing the curve's perimeter with its projection onto the xOy coordinate plane... The relative length difference between the perimeters yields the wrinkling surface undulation factor.

[0033] In this embodiment, the threshold for the occurrence of slight wrinkling is set to 0.1%, that is, when WF≥0.1%, slight wrinkling occurs on the surface.

[0034] 3) Overall part wrinkling scanning and evaluation, specifically including:

[0035] 3.a) Considering the area on the entire part surface that needs to be identified as wrinkled, determine the scanning interval Δr according to actual needs, and let... The wrinkled surface undulation factor WF [r1, r2] was obtained by continuous scanning. The scanning radius range was determined to be 400mm-500mm, and the scanning gap Δr was 3mm.

[0036] 3.b) Using the interval scanning method, the relationship between the scanning radius r and the WF wrinkling surface undulation factor is obtained. The wrinkling severity within the entire wrinkling judgment area of ​​the rotating part is obtained by integration, and the final overall part undulation factor WF is calculated. total =0.56. The overall part undulation factor quantifies the degree of wrinkling within a certain area of ​​the part surface. The larger the overall part undulation factor, the more severe the wrinkling within the area. By quantifying the degree of wrinkling through the overall part undulation factor, the overall part undulation factor can be used as an optimization target to optimize and adjust the process parameters of the rotating part. Finally, through simulation, a combination of industrial production process parameters with no or minimal wrinkling can be achieved.

[0037] Compared with existing technologies, this method realizes wrinkling judgment in the forming process of solid element rotating parts based on geometric information, solving the problem that solid elements cannot judge wrinkling through stress state. By quantifying the degree of wrinkling through fluctuation factors, it provides a tool for process optimization methods that combine simulation and optimization techniques.

[0038] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for monitoring wrinkling of solid units in the simulated forming process of sheet metal rotating parts, characterized in that, By constructing a simulation model of the forming of a rotating part and simulating the deep drawing process of sheet metal, the surface geometric information of the rotating part in the simulation results is extracted. The degree of surface undulation is obtained by transforming the coordinate system and comparing calculations, and then the overall wrinkling evaluation is obtained. The comparative calculation refers to: obtaining the undulation information of the surface of the rotating part at a position of radius r from the rotation axis, comparing it with the standard circumference of a circle without wrinkles, and calculating the degree of surface undulation. Specifically, it is to determine whether the length of the surface curve formed by the combination of virtual nodes is greater than the theoretical circumference. The aforementioned coordinate system transformation refers to converting the surface node coordinate information during sheet metal forming simulation from a Cartesian coordinate system to a cylindrical coordinate system. Specifically, after the simulation ends, the coordinate information of the predefined output set of upper and lower surface nodes is obtained, which must meet the requirement of a one-to-one correspondence between nodes and coordinates; a coordinate system is established with the rotation axis direction as the z-axis direction. The coordinate system is used to transform the extracted node coordinate information so that each node number corresponds to two coordinate values: Cartesian coordinates and cylindrical coordinates. Based on the selected scan radius r, the surface node set is divided into two parts: nodes within the scan radius r and nodes outside the scan radius r. Using the nodes... Cylindrical coordinates, initially filtering those located on both sides of the scan radius. Points within the length, i.e. ,in It should be at least 1.5 times the average side length of the upper surface unit; the set of nodes initially selected is denoted as the set of nodes to be judged within radius r. The set of nodes to be judged outside the radius r Traverse the set of nodes to be judged. Coordinates, in Find the nearest node and Store the corresponding nodes in combination; utilize and The node combination is used to obtain the virtual node located exactly at the scan radius r using interpolation. Perform similar processing on all node combinations to obtain a set of virtual nodes, and then arrange the virtual nodes according to... After sorting the coordinates and connecting the first and last coordinates, the surface curve at the scanning radius r can be obtained. The surface curve formed by the combination of virtual nodes Calculate the total length S of the surface curve.

2. The method for monitoring wrinkling of solid units in the simulation forming process of sheet metal rotating parts according to claim 1, characterized in that, The aforementioned simulation model for forming a rotating part is a finite element model that simulates the forming process by setting up a working mold and defining its motion in a general commercial finite element software based on the actual forming process parameters of the rotating part. The contact conditions between the blank and the mold are set according to the actual lubrication conditions. When dividing the blank into solid element meshes, the number of elements in the thickness direction should be no less than 3. Based on the mesh information, the node numbers of the solid elements on the upper and lower surfaces of the blank are determined to form surface node sets, which are defined as the upper surface set and the lower surface set, respectively. The model is set to output the changes in the coordinates of the nodes in the upper and lower surface sets as the forming process progresses. During finite element analysis, it should be ensured that mesh re-division and node number rearrangement do not occur.

3. The method for monitoring wrinkling of solid units in the simulation forming process of sheet metal rotating parts according to claim 1, characterized in that, The aforementioned sheet metal deep drawing process simulation refers to the process of using a general-purpose commercial finite element software solver to calculate and solve the simulation model of the rotating part, thereby obtaining the deformation of the rotating part under the forming conditions set in the model.

4. The method for monitoring wrinkling of solid units in the simulation forming process of sheet metal rotating parts according to claim 1, characterized in that, The aforementioned surface geometric information of the rotating part refers to obtaining the length of the projection curve of the rotating part surface after wrinkling occurs by transforming the coordinate system. Specifically, based on the forming process simulation results obtained from the forming simulation model of the rotating part, the Cartesian coordinate system is converted into a cylindrical coordinate system, and a one-to-one corresponding point group located within and outside the radius r of the rotating axis of the rotating part is selected. The point precisely located at the radius r is obtained by interpolating virtual points, and the length of the projection line of the rotating part surface is calculated by sequentially connecting the virtual points.

5. A solid unit wrinkling monitoring system for simulating the forming process of sheet metal rotating parts according to any one of claims 1-4, characterized in that, include: The system comprises a simulation post-processing node coordinate extraction unit, a wrinkling judgment unit, a region scanning unit, and a wrinkling evaluation unit. Specifically: the simulation post-processing node coordinate extraction unit extracts the surface node coordinate information of the rotating part after the forming simulation is completed using the finite element post-processing method, based on the simulation results; the wrinkling judgment unit, based on the obtained surface node coordinate information, obtains the curve length of the set of points from the rotating part surface to the rotation axis with radius r through coordinate transformation and point filtering, and compares it with the ideal curve length to obtain the degree of wrinkling; the region scanning unit continuously calls the wrinkling judgment unit to obtain wrinkling information within a certain area of ​​the part surface; and the wrinkling evaluation unit obtains the wrinkling evaluation index for the entire part forming process based on the wrinkling information within the part surface area obtained by the region scanning unit.

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