FEM Mesh/ro

Creează o rețea MEF
Există modalități diferite de a crea o plasă de discretizare MEF în FreeCAD:
 * Netgen FEM instrument Mesh FreeCAD MeshNetgenFromShape utilizând GUI sau Python
 * FreeCAD FEM instrument de plasă GMSH MeshGmshFromShape utilizând GUI sau Python
 * Python înseamnă a face direct FEM Mesh de mână
 * Importați o plasă FEM

There are different possibilities to set up a mesh in the FEM Workbench:
 * The Gmsh tool from the graphical user interface.
 * The Netgen tool from the graphical user interface.
 * Importing a mesh from another program. In particular, Gmsh and Netgen can be used by themselves outside of FreeCAD to mesh solid bodies like Step files.
 * Manually creating the mesh through Python scripting.

Obiectele create în PartDesign și Part sunt suportate, precum și copii simple ale acestor organisme. Două ochiuri sunt disponibile pentru utilizator: Netgen și GMSH. Netgen este inclus în FreeCAD. Pentru GMSH, trebuie instalat un binar extern. Consultați FEM Install





The Gmsh and Netgen tools are convenience tools to quickly mesh a body, and thus don't expose the full capabilities of these programs; they normally create triangular meshes, which may not be ideal for some types of analysis. If you'd like to have more control of the created mesh (use only quadrilaterals, precise element number and size, variable resolution of the mesh, etc.), you should use these programs externally, produce a mesh file in a supported format, and import this file into FreeCAD.

Previously, Netgen was included with FreeCAD and could be used immediately. Now, both Netgen and Gmsh should be installed before they can be used by the FEM Workbench. Refer to FEM Install for instructions.

Meshing software
Meshing software operates on solid bodies that can be in different formats, like Step and Brep. These programs can be used independently of FreeCAD, and typically have many options to control the meshing algorithms, element size, and boundary conditions.

The FEM Workbench has developed simple communication interfaces to use Gmsh and Netgen directly inside FreeCAD. Other programs don't have an interface, but this could change in the future if there is interest from the community, and if those applications are easy to integrate. The meshing software can be compiled and distributed together with FreeCAD only if its license is compatible with the LGPL2 license; otherwise, the program has to be used as an external binary, like Gmsh (GPL2) is used.

Interface implemented in FreeCAD

 * Gmsh: main website, code repository
 * Netgen: main website, code repository

No interface in FreeCAD

 * ENigMA, forum thread, code repository
 * libMesh, main website, code repository, forum thread; it's a very active project, and it's C++ only
 * PythonOCC, main website
 * SnappyHexMesh, main website
 * Tetgen, main website

Elemente de plasă MEF în FreeCAD
FreeCAD acceptă diferite tipuri de elemente. Există o legătură externă de blog care explică diferențele și momentul de utilizare a tipului de element: https://www.comsol.com/blogs/meshing-your-geometry-various-element-types/


 * "ni" înseamnă că tipul elementului nu este implementat în FreeCAD, dar formatul îl va suporta.
 * "-" înseamnă că specificația formatului nu suportă acest tip de element, deci FreeCAD nu o poate suporta.
 * "?" nu se știe dacă formatul acceptă acest tip de element.

General
Mai multe informații despre tipurile de elemente FEM și structura lor de date în cadrul FreeCAD pot fi găsite pe FEM Elements Types.

More information on the elements, and their data structure inside FreeCAD can be found in FEM Element Types.

Create a FEM mesh completely in Python
FreeCAD Scripting Basics.

The Python API allows the user to define a finite element mesh by directly adding individual nodes, and defining edges, faces, and volumes.

The mesh itself is of type, which needs to be attached to a proper document object of type.

Creating a mesh with one Tet-10 element
Create an empty FemMesh, populate it with nodes, create the volume, and finally call to create the document object with the corresponding mesh.

Dacă doriți să aveți o numerotare predefinită a elementelor și nodurilor:

To create an actual document object, instead of you can also use the document  method; then attach the created mesh to this object's  attribute.

Manipulare vizuală
Evidențiați unele noduri din vizualizare:

Once a FemMesh object has been created with, some of its visual properties can be changed by modifying the different attributes of its. This can be useful to postprocess the mesh after a finite element solution has been obtained.

Highlight some nodes in the mesh

Culori și deplasări postprocesare: Evidențiați unele noduri din vizualizare:

Set volume 1 to red

Set nodes 1, 2 and 3 to a certain color; the faces between the nodes acquire an interpolated color.

Displace the nodes 1 and 2 by the magnitude and direction defined by a vector.

Double the factor of the displacement shown. 

Shell, 3 node triangle, tria3 (linear)
Add a face with the element number.

Shell, 6 node triangle, tria6 (quadratic)
Add a face with the element number.

Shell, 4 node quadrangle, quad4 (linear)
Add a face with the element number.

Shell, 8 node quadrangle, quad8 (quadratic)
Add a face with the element number.

Volume, 4 node tetrahedron, tetra4 (linear)
Add a volume with the element number.

Volume, 10 node tetrahedron, tetra10 (quadratic)
Add a volume with the element number.

Volume, 8 node hexahedron, hexa8 (linear)
Add a volume with the element number.

Volume, 20 node hexahedron, hexa20 (quadratic)
Add a volume with the element number.

Volume, 6 node pentahedron, penta6 (linear)
Add a volume with the element number.

Volume, 15 node pentahedron, penta15 (quadratic)
Add a volume with the element number.

Volume, 5 node pyramid, pyra5 (linear)
Add a volume with the element number.

Volume, 13 node pyramid, pyra13 (quadratic)
Add a volume with the element number.

Scripting examples for groups
See for example https://forum.freecadweb.org/viewtopic.php?f=18&t=37304&start=20#p318823