FEM MeshNetgenFromShape/ru

Description

For a finite element analysis, the geometry needs to be discretized into a FEM Mesh. This command uses Netgen (which needs to be installed on the system) to generate the mesh. Netgen meshes are not supported by Elmer.

Depending on your operating system and installation package, Netgen might be bundled with FreeCAD or not. For further information see FEM Install.

introduced in 1.0: The refactored Netgen mesher is available. It can be activated in the preferences and is installed via Python bindings as explained on the aforementioned FEM Install page.

Usage

1. Select the shape you want to analyze. For a volume, this needs to be solid or compsolid. A compsolid is necessary if your part is made from multiple materials (a compsolid can be created with the Part BooleanFragments command).
2. There are several ways to invoke the command:
   • Press the Mesh From Shape by Netgen button.
   • Select the Mesh → Mesh From Shape by Netgen option from the menu.
3. Optionally, set the max/min element size (the default setting usually creates meshes that are too coarse) and element order (using the Second Order checkbox).
4. Optionally, change the Fineness to one of the predefined choices or choose UserDefined and manually edit the parameters.
5. Click the Apply button to generate the mesh. introduced in 1.0: Optionally, use the Cancel button to abort meshing if using the new Netgen implementation.
6. Click the OK button to generate the mesh and close the dialogue. You can also click the Cancel button to cancel the changes or creation of the mesh object.

Properties - Legacy Netgen

• ДанныеMax. Size: Maximum size of the element in mm.
• ДанныеMin. Size: introduced in 1.0: Minimum size of the element in mm.
• ДанныеSecond order: Second order elements contain more nodes per element. Usually, it is enough to use rougher mesh to obtain same solution precision as with the first order elements,
  • true (default); second order elements,
  • false; first order elements.
• ДанныеFineness: Offers predefined levels of mesh density.
• ДанныеGrowth Rate: Defines how much adjacent elements can differ in size.
• ДанныеNb. Segs per Edge: Defines the minimum number of mesh segments per edge.
• ДанныеNb. Segs per Radius: Defines the minimum number of mesh segments per radius.
• ДанныеOptimize:
  • true (default): applies optimization algorithm to improve mesh quality
  • false

Properties - Refactored Netgen

• ДанныеBad Element Limit: Limit for max element angle (150-180).
• ДанныеBase Element Np: If non-zero, baseelement must have BaseElementlNp points.
• ДанныеBlock Fill: If enabled, block filling is performed.
• ДанныеCheck Chart Boundary: If enabled, chart boundary is checked.
• ДанныеCheck Impossible
• ДанныеCheck Overlap: If enabled, overlapping surfaces are checked.
• ДанныеCheck Overlapping Boundary: If enabled, overlapping surface mesh is checked before volume meshing.
• ДанныеClose Edge Factor: Factor to restrict meshing based on close edges.
• ДанныеCurvature Safety: Safety factor for curvatures (elements per radius).
• ДанныеDelaunay: If enabled, Delaunay algorithm is used for 3D meshing.
• ДанныеDelaunay2d: If enabled, Delaunay algorithm is used for 2D meshing.
• ДанныеElement Order: High order element curvature.
• ДанныеElement Size Weight: Weight of element size with respect to element shape.
• ДанныеEnd Step: Last step:
  • AnalyzeGeometry
  • MeshEdges
  • MeshSurface
  • OptimizeSurface
  • MeshVolume
  • OptimizeVolume
• ДанныеFill Distance: Block filling up to distance.
• ДанныеFineness: Offers predefined levels of mesh density:
  • VeryCoarse
  • Coarse
  • Moderate
  • Fine
  • VeryFine
  • UserDefined
• ДанныеGive Up Tolerance: Give up quality class for 3D meshing.
• ДанныеGive Up Tolerance2d: Give up quality class for 2D meshing.
• ДанныеGive Up Tolerance Open Quads: Give up quality class for closing open quads, greater than 100 for free pyramids.
• ДанныеGlue: introduced in 1.1: Glue shapes to get a conformal mesh.
• ДанныеGrowth Rate: Grading for local h.
• ДанныеHeal Shape: If enabled, shape is healed before meshing.
• ДанныеInvert Tets
• ДанныеInvert Trigs
• ДанныеLocal H: If enabled, uses local h.
• ДанныеMax Outer Steps: Maximum outer steps.
• ДанныеMax Size: Maximum size of the element in mm.
• ДанныеMin Size: Minimum size of the element in mm.
• ДанныеOnly3d Domain Nr
• ДанныеOptimization Error Power: Power of error to approximate max error optimization.
• ДанныеOptimization Steps2d: Number of 2D optimization steps.
• ДанныеOptimization Steps3d: Number of 3D optimization steps.
• ДанныеOptimize2d: 2D optimization strategy.
• ДанныеOptimize3d: 3D optimization strategy.
• ДанныеParallel Meshing: If enabled, uses parallel meshing.
• ДанныеQuad Dominated: If enabled, uses quad dominated surface meshing.
• ДанныеRelinner Safety: Radius of active environment (times h).
• ДанныеSafety: Radius of local environment (times h).
• ДанныеSecond Order: If enabled, uses second order element meshing.
• ДанныеSecond Order Linear: If enabled, second order nodes are created by linear interpolation.
• ДанныеSegments Per Edge: Minimum number of segments per edge.
• ДанныеSloppy: Quality tolerances are handled less careful.
• ДанныеStar Shape Class: Class starting star-shape filling.
• ДанныеStart In Surface: If enabled, starts surface meshing from everywhere in surface.
• ДанныеStart Step: First step:
  • AnalyzeGeometry
  • MeshEdges
  • MeshSurface
  • OptimizeSurface
  • MeshVolume
  • OptimizeVolume
• ДанныеTry Hexes: If enabled, tries hexahedral elements.
• ДанныеUse Local H: If enabled, uses local H.
• ДанныеZRefine: introduced in 1.1: Z-refinement for extruded shapes, can create extruded hex meshes when combined with the Quad Dominated property. Will work only for first-order meshes (unless the generated elements are all hexahedrons):
  • No - Z-refinement is disabled
  • Regular - all elements have the same height
  • Custom - the height of each element must be specified
• ДанныеZRefine Direction: introduced in 1.1: Z-refinement direction (change if the shape is extruded in a direction other than the Z axis).
• ДанныеZRefine Size: introduced in 1.1: Z-refinement size (element height) given as a fraction of the shape size (total height). For a regular partition, only one value is needed.