CN117217049A - Finite element analysis preprocessing method and system based on Ploughmesh - Google Patents
Finite element analysis preprocessing method and system based on Ploughmesh Download PDFInfo
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Abstract
The application relates to the technical field of finite element analysis, and provides a finite element analysis pretreatment method and system based on Ploughmesh. The method of the application comprises the following steps: the feature recognition is carried out on the imported CAD model, so that the part limit of the CAD model is obtained; performing grid division on the CAD model subjected to feature recognition, and creating a grid node set and a grid cell set; performing unit refinement on the grid units of the CAD model through order conversion, and setting working condition simulation attributes for the CAD model subjected to unit refinement according to the actual application working conditions of the CAD model; and performing quality inspection on the CAD model set by the working condition simulation attribute, and exporting the CAD model passing the quality inspection into a preprocessing file. The application can accurately identify the parts in the model, and adaptively generate the 2D or 3D grid around the high gradient region and the complex geometric body based on grid division calculation, so that the model has higher grid resolution, more accurate result is obtained, and the calculation cost is reduced.
Description
Technical Field
The application relates to the technical field of finite element analysis, in particular to a finite element analysis pretreatment method and a finite element analysis pretreatment system based on Ploughmesh.
Background
The CAE software can now perform geometric modeling in a variety of ways, including from CAD importation, direct modeling, parametric modeling, reverse engineering techniques, etc., which have become more powerful in handling industry standard model formats (e.g., STEP, IGES, parasolid, etc.). The technology can rapidly and accurately guide the geometry of the CAD design into the CAE software environment for subsequent simulation analysis, so that the model is more flexibly and efficiently created, and the technology is used for solving various practical engineering problems. Some important support techniques involved behind CAE simulation analysis include: finite element theory, discretization technology, finite element units, material mechanical property models, boundary conditions, solving methods, post-processing, result visualization and the like. Through these support techniques, finite element analysis is widely used in the engineering field to help optimize design, improve product performance and reliability, and reduce test costs.
However, as CAD models are more accurate and complex, such as curved surfaces, chamfers, holes in the model, these complex features increase the difficulty of mesh rendering, and CAE simulation software has difficulty using distorted meshes of uniform size. For complex geometries, grids of the same size may produce poor grid quality.
Therefore, how to obtain a more accurate grid, so that the model has a higher grid resolution, becomes a technical problem to be solved urgently.
Disclosure of Invention
In order to overcome the defects in the prior art, the application provides a finite element analysis pretreatment method and a finite element analysis pretreatment system based on Ploughmesh.
According to an aspect of the present application, the present application provides a finite element analysis preprocessing method based on PloughMesh, including:
the feature recognition is carried out on the imported CAD model, so that the part limit of the CAD model is obtained;
performing grid division on the CAD model subjected to feature recognition, and creating a grid node set and a grid cell set;
performing unit refinement on the grid units of the CAD model through order conversion, and setting working condition simulation attributes for the CAD model subjected to unit refinement according to the actual application working conditions of the CAD model;
and performing quality inspection on the CAD model set by the working condition simulation attribute, and exporting the CAD model passing the quality inspection into a preprocessing file.
Preferably, in the finite element analysis preprocessing method based on Ploughmesh, feature recognition is performed on an imported CAD model to obtain part boundaries of the CAD model, and the method comprises the following steps: and obtaining the part limit of the CAD model by identifying the geometric features, the assembly relation, the contact surface and the connection mode of the imported CAD model.
Preferably, in the finite element analysis preprocessing method based on Ploughmesh, the method performs grid division on the CAD model subjected to feature recognition to create a grid node set and a grid unit set, and comprises the following steps: 2D meshing is conducted on a two-dimensional CAD model, a 2D mesh node set and a 2D mesh unit set are created, the 2D mesh node set is composed of 2D nodes, each 2D node has unique two-dimensional plane coordinates, the 2D mesh unit set is composed of 2D units, and the 2D units are two-dimensional geometric units composed of 2D mesh nodes.
Preferably, in the finite element analysis preprocessing method based on Ploughmesh, the method performs grid division on the CAD model subjected to feature recognition to create a grid node set and a grid unit set, and comprises the following steps: 3D meshing is conducted on the three-dimensional CAD model, a 3D mesh node set and a 3D mesh unit set are created, the 3D mesh node set is composed of 3D nodes, each 3D node has unique three-dimensional space coordinates, the 3D mesh unit set is composed of 3D units, and the 3D units are three-dimensional geometric units composed of 3D mesh nodes.
Preferably, in the finite element analysis preprocessing method based on Ploughmesh, the method performs grid division on the CAD model subjected to feature recognition to create a grid node set and a grid unit set, and further comprises:
after 2D meshing is carried out on the two-dimensional CAD model, checking whether a singular shape 2D meshing unit exists or not, checking whether the 2D meshing unit is degenerated or not, and optimizing the 2D meshing by controlling the aspect ratio of the 2D meshing;
after 3D grid division is carried out on the three-dimensional CAD model, the aspect ratio, torsion degree and taper ratio indexes of the 3D grid are checked, and the divided 3D grid is optimized by adjusting corresponding index parameters.
Preferably, in the finite element analysis preprocessing method based on Ploughmesh, the method performs grid division on the CAD model subjected to feature recognition to create a grid node set and a grid unit set, and further comprises: when the two-dimensional CAD model is subjected to 2D grid division, the 2D grid distribution of the two-dimensional CAD model is dynamically adjusted through 2D grid refinement and 2D grid coarsening.
Preferably, in the finite element analysis preprocessing method based on Ploughmesh, the method for thinning the grid cells of the CAD model through order conversion comprises the following steps: the original lower order grid cells are converted to higher order grid cells by adding nodes of the grid cells.
Preferably, in the finite element analysis preprocessing method based on Ploughmesh, the setting of the working condition simulation attribute for the CAD model subjected to unit refinement according to the actual application working condition of the CAD model comprises the following steps:
setting corresponding stress-strain properties and corresponding material properties for the grid unit according to actual application conditions, and setting boundary constraint conditions for the CAD model;
establishing a corresponding connection relation for the grid cells according to the stress-strain attribute;
and setting boundary constraint conditions for the CAD model according to the stress-strain attribute, the material attribute and the CAD model of the grid unit, and setting load constraint conditions for the CAD model.
Preferably, in the finite element analysis preprocessing method based on Ploughmesh, the quality inspection is performed on the CAD model set by the working condition simulation attribute, and the CAD model passing the quality inspection is exported as a preprocessing file, which comprises the following steps: and checking stress-strain properties, material properties, boundary constraint conditions, load constraint conditions and grid defects of the CAD model set by the working condition simulation properties, adjusting and repairing the CAD model which does not pass the quality check, and exporting the CAD model which passes the quality check into a preprocessing file in a CAE software format.
According to a second aspect of the present application, there is provided a finite element analysis preprocessing system based on PloughMesh, including a preprocessing server for obtaining part boundaries of an imported CAD model by performing feature recognition on the CAD model; performing grid division on the CAD model subjected to feature recognition, and creating a grid node set and a grid cell set; performing unit refinement on the grid units of the CAD model through order conversion, and setting working condition simulation attributes for the CAD model subjected to unit refinement according to the actual application working conditions of the CAD model; performing quality inspection on the CAD model set by the working condition simulation attribute, and exporting the CAD model passing the quality inspection into a preprocessing file
According to a third aspect of the present application there is provided a computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method of the first aspect of the present application when executing the program.
In summary, the finite element analysis preprocessing method and system based on Ploughmesh can automatically and accurately identify parts in a model, adaptively generate 2D or 3D grids around a high gradient area and a complex geometric body based on grid division calculation, enable the model to have higher grid resolution so as to obtain a more accurate result, reduce the number of grid points, reduce calculation cost, support the setting of parameters such as boundary conditions, load setting, material properties and the like of the geometric model, and support a plurality of preprocessing file formats so as to exchange data with other software.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that need to be used in the embodiments of the present application will be briefly described below, and it is obvious that the following drawings are only some embodiments described in the present application, and other drawings can be obtained according to the drawings without inventive effort for those skilled in the art.
Fig. 1 is a schematic diagram of a system for a Ploughmesh-based finite element analysis preprocessing method suitable for use in an embodiment of the present application;
fig. 2 is a flowchart illustrating a step of a finite element analysis preprocessing method based on plouthmessh according to an embodiment of the present application;
FIG. 3 is an exemplary diagram of a feature-identified CAD model obtained by the Ploughmesh-based finite element analysis preprocessing method according to the present application;
FIG. 4 is an exemplary diagram of a 3D meshing of a CAD model according to the Ploughmesh-based finite element analysis preprocessing method of the present application;
FIG. 5 is an exemplary diagram of a state of the art meshing model in a simulated cutting simulation process;
fig. 6 is a diagram illustrating a state of a model for meshing according to the finite element analysis preprocessing method based on plouthmish according to the present application in a simulation cutting simulation process;
fig. 7 is a schematic structural diagram of the apparatus provided by the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to specific embodiments and corresponding drawings. It is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments, and the present application may be implemented or applied by different specific embodiments, and that various modifications or changes may be made in the details of the present description based on different points of view and applications without departing from the spirit of the present application.
Meanwhile, it should be understood that the scope of the present application is not limited to the following specific embodiments; it is also to be understood that the terminology used in the examples of the application is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the application.
Fig. 1 illustrates an exemplary system for a Ploughmesh-based finite element analysis preprocessing method suitable for use in embodiments of the present application. As shown in fig. 1, the system may include a preprocessing server 101, a communication network 102, and/or one or more preprocessing clients 103, an example of which is a plurality of preprocessing clients 103 in fig. 1.
The preprocessing server 101 may be any suitable server for storing information, data, programs, and/or any other suitable type of content. In some embodiments, the preprocessing server 101 may perform appropriate functions. For example, in some embodiments, the preprocessing server 101 may be used to perform finite element analysis preprocessing on a CAD model. As an alternative example, in some embodiments, the preprocessing server 101 may be used to perform finite element analysis preprocessing on CAD models through meshing. For example, the preprocessing server 101 may be configured to obtain a component boundary of the CAD model by performing feature recognition on the imported CAD model; performing grid division on the CAD model subjected to feature recognition, and creating a grid node set and a grid cell set; performing unit refinement on the grid units of the CAD model through order conversion, and setting working condition simulation attributes for the CAD model subjected to unit refinement according to the actual application working conditions of the CAD model; and performing quality inspection on the CAD model set by the working condition simulation attribute, and exporting the CAD model passing the quality inspection into a preprocessing file.
As another example, in some embodiments, the preprocessing server 101 may send the Ploughmesh-based finite element analysis preprocessing method to the preprocessing client 103 for use by the user, upon request from the preprocessing client 103.
As an optional example, in some embodiments, the preprocessing client 103 is configured to provide a visual preprocessing interface, where the visual preprocessing interface is configured to receive a selection input operation of performing finite element analysis preprocessing on the CAD model by a user, and, in response to the selection input operation, obtain, from the preprocessing server 101, a preprocessing interface corresponding to an option selected by the selection input operation and display the preprocessing interface, where at least information for performing finite element analysis preprocessing on the CAD model and an operation option for performing finite element analysis preprocessing on the CAD model are displayed in the preprocessing interface.
In some embodiments, communication network 102 may be any suitable combination of one or more wired and/or wireless networks. For example, the communication network 102 can include any one or more of the following: the internet, an intranet, a Wide Area Network (WAN), a Local Area Network (LAN), a wireless network, a Digital Subscriber Line (DSL) network, a frame relay network, an Asynchronous Transfer Mode (ATM) network, a Virtual Private Network (VPN), and/or any other suitable communication network. The preprocessing client 103 can be connected to the communication network 102 via one or more communication links (e.g., communication link 104), and the communication network 102 can be linked to the preprocessing server 101 via one or more communication links (e.g., communication link 105). The communication link may be any communication link suitable for transferring data between the preprocessing client 103 and the preprocessing server 101, such as a network link, dial-up link, wireless link, hardwired link, any other suitable communication link, or any suitable combination of such links.
Preprocessing client 103 may include any one or more clients that present interfaces related to finite element analysis preprocessing of CAD models in an appropriate form for use and operation by a user. In some embodiments, preprocessing client 103 may include any suitable type of device. For example, in some embodiments, the preprocessing client 103 may include a mobile device, a tablet computer, a laptop computer, a desktop computer, and/or any other suitable type of client device.
Although the preprocessing server 101 is illustrated as one device, in some embodiments any suitable number of devices may be used to perform the functions performed by the preprocessing server 101. For example, in some embodiments, multiple devices may be used to implement the functions performed by the preprocessing server 101. Alternatively, the functions of the preprocessing server 101 may be implemented using cloud services.
Based on the above system, the embodiment of the application provides a finite element analysis preprocessing method based on Ploughmesh, which is described in the following examples.
Ploughmesh is CAE preprocessing software that performs geometric processing, adaptive meshing, boundary conditions, and definition of material properties on CAD models. The Ploughmesh software can automatically and accurately identify the parts in the assembly. The preprocessing module of the software provides an automatic grid generation algorithm, and generates 2D or 3D grids in a self-adaptive manner around a high gradient area and a complex geometry, so that the model has higher grid resolution, a more accurate result is obtained, the number of grid points is reduced, the calculation cost is reduced, the setting of parameters such as boundary conditions, load setting, material properties and the like of the geometric model is supported, and meanwhile, a plurality of preprocessing file formats are supported so as to exchange data with other software.
Referring to fig. 2, a flowchart of steps of a finite element analysis preprocessing method based on plouthmessh according to an embodiment of the present application is shown.
The finite element analysis preprocessing method based on PloughMesh of the embodiment can be executed at a preprocessing server, and comprises the following steps:
step S201: and (3) obtaining the part limit of the CAD model by carrying out feature recognition on the imported CAD model.
As an example, when a CAD model in a format such as STEP or IGES is imported into the plouthmesmesh software, the method of the embodiment identifies features in the imported CAD model, such as geometric features, contact surfaces, connection modes, and the like, where the geometric features to be identified in the method of the embodiment include, but are not limited to, geometric features such as holes, edges, curved surfaces, and the like. When implementing the method of the embodiment, a person skilled in the art can identify geometric features to be identified according to an actual application scene, and the embodiment is not limited to this. And carrying out feature recognition on the imported CAD model, and providing a setting basis for subsequently setting boundary conditions, applying load conditions and constraint conditions. The limit of the parts is distinguished by identifying the single part in the CAD model, the geometric model is divided into proper parts according to the analysis requirement, and the CAD model is accurately analyzed.
As an example, in practical applications, to better distinguish between different parts or geometric entities in a CAD model, the method of the present embodiment may also assign different colors, i.e. "parts rendering" or "entity coloring", to the different parts or geometric entities, such that the different geometric portions appear in different colors when visualized, for easier recognition and distinction. By assigning different colors to different parts, a user can quickly and accurately identify and recognize different parts in the model, which can be assigned a desired color by coloring. Especially in complex assemblies or large models, the user can easily visualize the complex geometric model through part rendering or entity coloring, so that the structure and the constituent parts of the model are better understood, and the editing, boundary condition setting and subsequent analysis operation of the model are facilitated. Fig. 3 is an exemplary diagram of a feature-identified CAD model obtained by the plurghmesh-based finite element analysis preprocessing method according to the present application.
Step S202: and performing grid division on the CAD model subjected to feature recognition, and creating a grid node set and a grid cell set.
After acquiring a CAD model with boundaries by feature recognition, the method of the present embodiment requires dividing the connected CAD model into discrete finite elements by a grid method.
As an example, when the imported CAD model is two-dimensional, the method of the present embodiment performs 2D meshing on the two-dimensional CAD model, creating a set of 2D mesh nodes and a set of 2D mesh cells, where the set of 2D mesh nodes is composed of 2D nodes, each 2D node has unique two-dimensional plane coordinates, and the set of 2D mesh cells is composed of 2D cells, and the 2D cells are two-dimensional geometry cells composed of 2D mesh nodes.
The 2D grid division is a discretization method for processing a two-dimensional geometric model and is used for processing the problems such as surface deformation, plane stress, plane strain and the like in a flat plate, a thin-wall structure, a plate and a two-dimensional section scene. In the 2D meshing of the method of the present embodiment, the geometric model is considered a planar problem, ignoring the third dimension perpendicular to the plane. A 2D mesh is typically composed of triangular or quadrilateral elements to represent shapes on a two-dimensional plane.
In order to improve the accuracy and efficiency of model analysis, the method of the embodiment dynamically adjusts the 2D grid distribution of the two-dimensional CAD model through 2D grid refinement and 2D grid coarsening when the two-dimensional CAD model is subjected to 2D grid division.
As an example, when the method of the embodiment performs 2D grid division on the two-dimensional CAD model, an adaptive grid algorithm is adopted, and according to a preset standard and error estimation, the 2D grid is thinned and coarsened, so as to optimize the quality of the grid unit and reduce the error. For example, after performing 2D simulation calculation, error estimation is performed according to the simulation result, and a region where grid refinement or coarsening is required is determined, typically, grid refinement is performed where gradient change is large or the simulation result is less accurate, and grid coarsening is performed in a region of less importance. In the practical application process, grid refinement and coarsening are an iterative process, namely, a method for coarsening the grid is used in advance to solve the problem, and the size of the refined grid is selected according to result feedback until a certain convergence criterion is reached.
The self-adaptive grid algorithm can reduce the use of computing resources and improve the simulation efficiency on the premise that the grid nodes can compute accurate simulation results. The self-adaptive grid algorithm dynamically adjusts grid distribution according to physical phenomena and geometric characteristics in simulation, so that grids are denser in important areas and sparser in less important areas such as corners, welding seams, hole edges, small holes, cutting, holes and the like.
In the grid refinement and coarsening process, the method of the embodiment also needs to check and optimize the quality of the grid. The grid quality has an important influence on the accuracy and stability of the simulation result, so that attention is required to keep the quality of the 2D grid cells, check whether the 2D grid cells with singular shapes exist, check whether the 2D grid cells are degraded, optimize the divided 2D grids by controlling the aspect ratio of the 2D grids, avoid the occurrence of the cells with singular shapes, avoid the degradation of the grids, and the like. Optimizing the quality of the grid cells helps to ensure the accuracy and computational efficiency of the simulation results.
For example, the present embodiment method dynamically adjusts the 2D mesh according to the following manner.
Where the mesh needs to be refined, including a specific region, in order to more accurately capture the complexity and high gradient regions of the model, the computational efficiency is maintained while focusing on the specific region, including: 1) When the mold contains geometric details of small dimensions, such as small holes, cuts, holes, etc.; 2) When the model has a stress or displacement intensity concentration area, such as corners, welding seams, hole edges and the like; 3) Where areas of material property variation exist in the model, such as material interfaces, composite layers, welds, and the like.
In order to reduce the density of the grid, to improve the computing efficiency and reduce the computing cost, the 2D grid is coarsened, and the situation that coarsening is needed is as follows: 1) There are flat, relatively simple regions in the geometric model, and if there are no strong displacement gradients or stress concentrations, the mesh can be suitably coarsened to reduce the number of computational cells; 2) There may be areas in the model for which the mesh may be moderately coarsened, such as non-working surfaces of the structure, for which the analysis results are not of particular interest; 3) Pretreatment: in the pre-processing stage of the model, a coarser grid may be used for the preliminary analysis in order to quickly evaluate the rationality of the design.
After 2D meshing, a set of 2D mesh nodes and a set of 2D mesh cells are created. A set of 2D mesh nodes is a set of a series of 2D nodes. Each 2D node has a unique coordinate location on the two-dimensional plane for representing the boundary of the geometry and discrete points of the surface. Nodes are typically represented by (x, y) coordinates, and their locations may also be identified using local or global coordinates. The set of 2D nodes defines the geometry of the 2D mesh, and a series of line segments or curves are formed by the connection of the 2D nodes. The number and distribution of nodes in a 2D node set directly affects the resolution and accuracy of the 2D mesh. A set of 2D grid cells is a set of a series of 2D cells. Each 2D cell is a geometric cell made up of 2D nodes. The 2D mesh typically uses triangular or quadrilateral cells. The 2D unit set is used for representing the surface and the boundary of the geometric body, dividing the continuous curved surface or the boundary into a limited number of small units, defining the topological structure of the 2D grid, and forming the complete 2D grid through the connection relation among the units.
As another example, when the imported CAD model is three-dimensional, the method of the present embodiment performs 3D meshing on the three-dimensional CAD model, creating a 3D mesh node set and a 3D mesh cell set, where the 3D mesh node set is composed of 3D nodes, each 3D node has unique three-dimensional space coordinates, and the 3D mesh cell set is composed of 3D cells, and the 3D cells are three-dimensional geometry cells composed of 3D mesh nodes. The 3D grid division is a discretization method for processing a three-dimensional geometric model, and is suitable for processing the problems such as volume deformation, stress, strain and the like of a three-dimensional structure, a volume member and a three-dimensional solid scene. In the 3D meshing of the method of the present embodiment, the geometric model is considered as a volumetric problem with three dimensions, and therefore discretization in all three directions is required. A 3D mesh is typically composed of cells such as tetrahedrons, hexahedrons, or pentahedrons to represent shapes in three-dimensional space. Different types of 3D cells are used to handle different shaped volume structures.
After 3D meshing, a set of 3D mesh nodes and a set of 3D mesh cells are created. A 3D mesh node set is a set of a series of 3D nodes. Each 3D node has a unique coordinate position in three-dimensional space for representing the volume and internal structure of the geometry. Nodes are typically represented by (x, y, z) coordinates, and their locations may also be identified using local or global coordinates. The 3D node set defines the geometry of the 3D mesh, and a series of planes, surfaces and volumes are formed by the connection of the 3D nodes. A set of 3D grid cells is a set of a series of 3D cells. Each 3D cell is a three-dimensional geometry made up of 3D nodes, and 3D meshes typically use hexahedral or tetrahedral cells because of their superior numerical properties and computational efficiency. The 3D unit set is used for representing the volume and the internal structure of the geometric body, dividing the continuous volume into a limited number of units, and forming a complete 3D grid through the connection relation among the units.
In the process of 3D meshing, the method of this embodiment also needs to check and optimize the quality of the 3D mesh. The checking of the quality of the 3D mesh comprises: aspect ratio, warp, tortuosity, taper ratio, maximum side length, minimum side length, maximum triangle interior angle, minimum triangle interior angle, maximum quadrilateral interior angle, minimum quadrilateral interior angle, etc., e.g., aspect ratio refers to the ratio of 3D grid cell side lengths, smaller aspect ratio typically results in grid distortion; the torsion degree refers to the degree of asymmetry of the internal angles of the 3D grid cells, and the larger torsion degree can cause grid distortion to influence the accuracy of the model; the taper ratio is the ratio of the thicknesses of the grid cells, and a larger taper ratio may lead to degradation and numerical instability of the grid cells. In the 3D grid quality inspection, the method of this embodiment may set a threshold for quality index, and if the quality index of the 3D grid unit does not reach the set threshold, adjustment and optimization are required. Through reasonable grid quality inspection and optimization, the accuracy and reliability of analysis results can be ensured. Fig. 4 is an exemplary diagram of a 3D meshing of a CAD model according to the present application based on a finite element analysis pre-processing method of plouthmesmesh.
Each node in the set of nodes represents a discretized point of the original geometric model in the finite element mesh. The finite element method divides a continuous geometric model into discrete nodes, so that the actual problem is converted into a numerical calculation problem of the nodes. Defining boundary conditions: a portion of the nodes in the node set are used to define boundary conditions, such as bundle displacement or external loading. The boundary conditions directly affect the results of the finite element analysis, and different working conditions can be simulated by applying displacement or external force on the nodes. Describing displacement and deformation: in the finite element analysis process, solutions are obtained at nodes that represent the displacement and deformation states of the structure at different time steps. By interpolating the displacement on the nodes, the displacement and deformation information of the whole structure can be obtained.
Each cell in the set of cells represents a small region of the original geometric model. Finite element elements break down a structure into many small units whose behavior can be described by the connection relationships between nodes. Describing physical behavior: different types of finite element elements may be used to describe different physical behaviors of the structure, such as stress, strain, thermal conduction, and the like. By applying an appropriate physical field across the cell, the response and behavior of the structure can be modeled. And (3) performing numerical calculation: the finite element method solves the numerical calculation problem of the structure by constructing an algebraic equation set on the unit. The behavior and connection of the cells form the basis of a set of algebraic equations.
The generation of node sets and cell sets is a pre-processing stage in finite element analysis, which provides important underlying data for subsequent numerical computation and analysis. In the subsequent finite element solving process, an algebraic equation set is constructed according to the information in the node and the unit set, and the results of displacement, stress, strain and the like of the structure are obtained through numerical calculation. Thus, accurate generation of node sets and cell sets is critical to obtaining reliable finite element analysis results.
In practical applications, the 2D surface mesh represents the boundary of a two-dimensional geometry, is a single-layer mesh, has no volume or thickness, represents the surface shape of the geometry, and is relatively simple and lightweight to visualize. Because of the absence of volume information, the 2D surface mesh requires relatively less computational resources during simulation analysis and operates at a faster speed. A 3D volume mesh is typically used to represent the volume and internal structure of a three-dimensional geometry, consisting of a series of volume elements (e.g., hexahedrons, tetrahedrons, etc.) that divide the geometry into a finite series of volume elements. The 3D volumetric mesh is a multi-layered mesh having a volume and a thickness capable of representing the surface shape and internal structure of the geometric body, including the volume and physical properties within the volume. In visualization, the 3D volume mesh may display both the surface and volume of the geometry. The user can view the surface profile of the geometry in the visualization, as well as the internal structure of the geometry through the profile. For simple planar problems, 2D surface meshes are more suitable; whereas for complex three-dimensional structures and problems, 3D volume meshes provide more accurate analysis results.
Step S203: and carrying out unit refinement on the grid units of the CAD model through order conversion, and setting working condition simulation properties for the CAD model subjected to unit refinement according to the actual application working conditions of the CAD model.
The grid cells typically use linear cells (2D: linear triangle cells or linear quadrangle cells, 3D: linear tetrahedral cells or linear hexahedral cells) with a node order of 1. The method of the embodiment converts the original low-order grid cells into high-order grid cells by adding nodes of the grid cells. For example, intermediate nodes are added on the sides of each original cell, thereby forming higher order cells. The number of nodes of the high-order units is more than that of the low-order units, so that in a region needing higher precision, the corresponding low-order units can be selected to be thinned into the high-order units, and the accuracy of the solution is improved.
As an example, the method of the embodiment determines the connection relationship between the grid cells according to the requirement of the actual working condition, specifically, sets corresponding stress-strain attribute for the grid cells according to the actual application working condition, and simulates the connection relationship according to the stress-strain attribute of the grid cells. The rigid grid cells have no deformations, their length, angle and shape remain unchanged during finite element analysis, for simulating rigid connection relations. The flexible unit allows a certain deformation during analysis, but its deformation range is relatively small for simulating a connection relationship with a certain elasticity. The spring unit is used for simulating the connection relation of springs, dampers and the like. The different grid cells have a linear or non-linear stress-strain relationship that simulates the stiffness and damping characteristics of the connection.
As an example, the method of the embodiment sets corresponding material properties for the grid cells according to the actual application working conditions. The solid cells are finite element mesh cells used to model a three-dimensional volumetric structure, for simulating a three-dimensional object having a thickness, such as a cube, cylinder, etc. For the entity units, the main properties thereof include material properties, and the method of the embodiment relates the material properties of the entity units, such as elastic modulus, poisson ratio, density and the like, so as to describe the material characteristics of the entity. In the method of the embodiment, boundary constraint conditions are set for the CAD model according to actual application working conditions, the boundary constraint conditions are used for constraining the degree of freedom of the CAD model, the boundary constraint under the actual working conditions is simulated, and displacement constraint and steering constraint can be applied to the nodes or units.
According to the method, load constraint conditions are set for the CAD model according to stress-strain properties, material properties and boundary constraint conditions set for the CAD model of the grid unit. Load constraints include load forms such as concentrated force loads, moment loads, pressure loads, etc., the magnitude and direction of the load, and the location or manner of application of the load.
Step S204: and performing quality inspection on the CAD model set by the working condition simulation attribute, and exporting the CAD model passing the quality inspection into a preprocessing file.
After the setting of the working condition simulation attribute of the CAD model is completed, the embodiment also needs to carry out quality inspection on the CAD model, so that the CAD model is well prepared and has no error.
As an example, the method of the present embodiment performs inspection on the CAD model for stress-strain properties, material properties, boundary constraints, load constraints, and grid defects of the CAD model that are set by the operating mode simulation properties. For example, checking whether fixed boundary constraints, applied loads, displacement boundary conditions, etc. are correctly set in the appropriate positions of the model, ensuring that these boundary constraints reflect the boundary conditions of the actual problem; confirming whether the material properties of each grid part are correctly distributed, such as checking whether the material properties of elastic modulus, poisson ratio, density and the like are consistent with the properties of the actual materials; checking whether the geometric structure of the model is complete, checking whether the geometric gap, the overlapping surface, the small-size geometric features and the like exist, and ensuring the continuity and the correctness of the model geometry; and checking whether the grid has the problems of grid discontinuity caused by excessive grid deformation, twisting units and hanging nodes. The method of the embodiment adjusts and repairs the CAD model which does not pass the quality inspection, and exports the CAD model which passes the quality inspection into a preprocessing file in a CAE software format. The format of the preprocessing file exported by the method of the embodiment is suitable for CAE software. Including but not limited to the following formats:
1) Nastran Input File (. Bdf): is a generic finite element analysis input file format for describing finite element models and boundary conditions. It is the standard input format for MSC Nastran et al software.
2) Abaqus Input File (. Inp): abaqus is a widely used finite element analysis software whose input file format is a text file describing models and loads.
3) Ansys Input File (. Dat,. Cdb): ansys is a powerful finite element analysis software whose input files contain information on model geometry, material properties, loading, etc.
4) ABAQUS ODB File (.odb): the ODB file of ABAQUS is a file for storing simulation results, and can be used in post-processing.
5) Patran Neutral File (·nas): patran is a commonly used pre-post processing software in which a neutral file format can be used to import models into other software.
The method of the embodiment supports the export of a plurality of preprocessing file formats so as to exchange data with various CAE software or perform operations such as multi-physical field coupling and the like.
In practical application, the method of the embodiment performs geometric feature extraction on the imported CAD model, automatically identifies and extracts geometric features of the model, such as boundary, surface, volume, boundary, curved surface, hole and other information, and decomposes the imported CAD model into independent parts or components. In complex CAD models, which may include multiple components or assemblies, component identification of the CAD model may facilitate subsequent individual simulation analysis and individual meshing of the individual components. The method of the embodiment can automatically identify the possible contact surface according to the geometric characteristics and the relative positions of the components and set the contact properties such as friction coefficient, bonding and the like. By contact definition, force transfer and contact behavior between components can be modeled. The method can automatically perform assembly positioning according to the geometric characteristics and constraint conditions of the assembly body, and ensures that the geometric constraint of the model is correct. After the preprocessing step is completed, the finite element model suitable for simulation analysis can be generated by the method of the embodiment, which comprises geometric information, material properties, boundary conditions and contact definition, and subsequent numerical simulation calculation can be performed. FIG. 5 is an exemplary diagram of a state of the art meshing model in a simulated cutting simulation process. Fig. 6 is a diagram illustrating a state of a meshing model in a simulated cutting simulation process according to the finite element analysis preprocessing method based on plouthmesmesh of the present application. As shown in fig. 5 and 6, the model obtained by the method according to the embodiment has higher grid precision, and a more real simulation effect is obtained.
As shown in FIG. 7, the present application also provides an apparatus comprising a processor 310, a communication interface 320, a memory 330 for storing a processor executable computer program, and a communication bus 340. Wherein the processor 310, the communication interface 320 and the memory 330 perform communication with each other through the communication bus 340. The processor 310 implements the above-described PLoughMesh-based finite element analysis preprocessing method by running an executable computer program.
The computer program in the memory 330 may be implemented in the form of software functional units and may be stored in a computer-readable storage medium when sold or used as a separate product. Based on this understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method of the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
The system embodiments described above are merely illustrative, in which elements illustrated as separate elements may or may not be physically separate, and elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected based on actual needs to achieve the purpose of the embodiment. Those of ordinary skill in the art will understand and implement the present application without undue burden.
From the above description of the embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus necessary general hardware platforms, or of course may be implemented by means of hardware. Based on such understanding, the foregoing technical solutions may be embodied essentially or in part in the form of a software product, which may be stored in a computer-readable storage medium, such as a ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to perform the various embodiments or methods of some parts of the embodiments.
The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present application should be included in the present application. Therefore, the protection scope of the application is subject to the protection scope of the claims.
Claims (10)
1. A finite element analysis preprocessing method based on plouthmesh, characterized in that the method comprises:
the feature recognition is carried out on the imported CAD model, so that the part limit of the CAD model is obtained;
performing grid division on the CAD model subjected to feature recognition, and creating a grid node set and a grid cell set;
performing unit refinement on the grid units of the CAD model through order conversion, and setting working condition simulation attributes for the CAD model subjected to unit refinement according to the actual application working conditions of the CAD model;
and performing quality inspection on the CAD model set by the working condition simulation attribute, and exporting the CAD model passing the quality inspection into a preprocessing file.
2. The plurahty mesh-based finite element analysis preprocessing method according to claim 1, wherein obtaining the part limits of the CAD model by performing feature recognition on the imported CAD model comprises: and obtaining the part limit of the CAD model by identifying the geometric features, the assembly relation, the contact surface and the connection mode of the imported CAD model.
3. The plurahty mesh-based finite element analysis preprocessing method of claim 1, wherein meshing the feature-identified CAD model to create a set of mesh nodes and a set of mesh cells, comprising: 2D meshing is conducted on a two-dimensional CAD model, a 2D mesh node set and a 2D mesh unit set are created, the 2D mesh node set is composed of 2D nodes, each 2D node has unique two-dimensional plane coordinates, the 2D mesh unit set is composed of 2D units, and the 2D units are two-dimensional geometric units composed of 2D mesh nodes.
4. The plurahty mesh-based finite element analysis preprocessing method of claim 1, wherein meshing the feature-identified CAD model to create a set of mesh nodes and a set of mesh cells, comprising: 3D meshing is conducted on the three-dimensional CAD model, a 3D mesh node set and a 3D mesh unit set are created, the 3D mesh node set is composed of 3D nodes, each 3D node has unique three-dimensional space coordinates, the 3D mesh unit set is composed of 3D units, and the 3D units are three-dimensional geometric units composed of 3D mesh nodes.
5. The plurahty mesh-based finite element analysis preprocessing method of claim 1, wherein the feature-identified CAD model is gridded to create a set of grid nodes and a set of grid cells, further comprising:
after 2D meshing is carried out on the two-dimensional CAD model, checking whether a singular shape 2D meshing unit exists or not, checking whether the 2D meshing unit is degenerated or not, and optimizing the 2D meshing by controlling the aspect ratio of the 2D meshing;
after 3D grid division is carried out on the three-dimensional CAD model, the aspect ratio, torsion degree and taper ratio indexes of the 3D grid are checked, and the divided 3D grid is optimized by adjusting corresponding index parameters.
6. The plurahty mesh-based finite element analysis preprocessing method of claim 1, wherein the feature-identified CAD model is gridded to create a set of grid nodes and a set of grid cells, further comprising: when the two-dimensional CAD model is subjected to 2D grid division, the 2D grid distribution of the two-dimensional CAD model is dynamically adjusted through 2D grid refinement and 2D grid coarsening.
7. The plurahty mesh-based finite element analysis preprocessing method according to claim 1, wherein cell refinement of the mesh cells of the CAD model by order conversion comprises: the original lower order grid cells are converted to higher order grid cells by adding nodes of the grid cells.
8. The finite element analysis preprocessing method based on Ploughmesh according to claim 1, wherein setting the working condition simulation attribute for the CAD model subjected to unit refinement according to the actual application working condition of the CAD model comprises the following steps:
setting corresponding stress-strain properties and corresponding material properties for the grid unit according to actual application conditions, and setting boundary constraint conditions for the CAD model;
establishing a corresponding connection relation for the grid cells according to the stress-strain attribute;
and setting boundary constraint conditions for the CAD model according to the stress-strain attribute, the material attribute and the CAD model of the grid unit, and setting load constraint conditions for the CAD model.
9. The finite element analysis preprocessing method based on plouthmesh according to claim 1, wherein the quality inspection is performed on the CAD model subjected to the condition simulation attribute setting, and the CAD model subjected to the quality inspection is exported as a preprocessing file, comprising: and checking stress-strain properties, material properties, boundary constraint conditions, load constraint conditions and grid defects of the CAD model set by the working condition simulation properties, adjusting and repairing the CAD model which does not pass the quality check, and exporting the CAD model which passes the quality check into a preprocessing file in a CAE software format.
10. The finite element analysis preprocessing system based on Ploughmesh comprises a preprocessing server side, wherein the preprocessing server side is used for obtaining part boundaries of a CAD model by carrying out feature recognition on the imported CAD model; performing grid division on the CAD model subjected to feature recognition, and creating a grid node set and a grid cell set; performing unit refinement on the grid units of the CAD model through order conversion, and setting working condition simulation attributes for the CAD model subjected to unit refinement according to the actual application working conditions of the CAD model; and performing quality inspection on the CAD model set by the working condition simulation attribute, and exporting the CAD model passing the quality inspection into a preprocessing file.
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