FEM ConstraintContact: Difference between revisions

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# The contact constraint can only be applied to two faces.
* The contact constraint can only be applied to two faces.
# Development for multiple contact at once: https://forum.freecadweb.org/viewtopic.php?f=18&t=15699&start=130#p303275
* Development for multiple contact at once: https://forum.freecadweb.org/viewtopic.php?f=18&t=15699&start=130#p303275
# Due to the fact that multiple meshes are currently not supported, contact must be applied to faces that are separated by (at least) a small distance. If the faces were touching (no gap between them), the result of a boolean union or boolean fragments operation (necessary to avoid having multiple meshes which is not allowed at the moment) would be a continuous mesh and thus no need to use contact anymore. Forum discussion: https://forum.freecadweb.org/viewtopic.php?f=18&t=62307
* Due to the fact that multiple meshes are currently not supported, contact must be applied to faces that are separated by (at least) a small distance. If the faces were touching (no gap between them), the result of a boolean union or boolean fragments operation (necessary to avoid having multiple meshes which is not allowed at the moment) would be a continuous mesh and thus no need to use contact anymore. Forum discussion: https://forum.freecadweb.org/viewtopic.php?f=18&t=62307

==Notes==


==Notes== <!--T:5-->
=== Tips for modeling ===
=== Tips for modeling ===

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* from https://forum.freecadweb.org/viewtopic.php?f=18&p=340874#p340494
* from https://forum.freecadweb.org/viewtopic.php?f=18&p=340874#p340494
* Better use linear elements otherwise calculations are very time consuming
* Better use linear elements otherwise calculations are very time consuming
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** If the surfaces are of comparable size and stiffness, the surface with the coarser mesh should act as the master surface.
** If the surfaces are of comparable size and stiffness, the surface with the coarser mesh should act as the master surface.


=== CalculiX === <!--T:9-->
=== CalculiX ===

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* The contact stiffness should be 10 times the young's modulus of the material for hard contact. The higher the value for contact stiffness, the harder the contact between surfaces.
* The contact stiffness should be 10 times the young's modulus of the material for hard contact. The higher the value for contact stiffness, the harder the contact between surfaces.
* The slave face is the face which penetrates into the master face, and therefore experiences more deformation.
* The slave face is the face which penetrates into the master face, and therefore experiences more deformation.

Revision as of 12:24, 12 March 2022

FEM ConstraintContact

Menu location
Model → Mechanical Constraints → Constraint contact
Workbenches
FEM
Default shortcut
None
Introduced in version
-
See also
FEM Constraint fixed

Description

Creates a FEM constraint for contact between 2 surfaces.

Usage

  1. There are several ways to invoke the command:
    • Press the FEM ConstraintContact button.
    • Select the Model → Mechanical Constraints → Constraint contact option from the menu.
  2. Select the master face.
  3. Select the slave face.
  4. Enter a contact stiffness.
  5. Enter a friction coefficient.

Limitations

  • The contact constraint can only be applied to two faces.
  • Development for multiple contact at once: https://forum.freecadweb.org/viewtopic.php?f=18&t=15699&start=130#p303275
  • Due to the fact that multiple meshes are currently not supported, contact must be applied to faces that are separated by (at least) a small distance. If the faces were touching (no gap between them), the result of a boolean union or boolean fragments operation (necessary to avoid having multiple meshes which is not allowed at the moment) would be a continuous mesh and thus no need to use contact anymore. Forum discussion: https://forum.freecadweb.org/viewtopic.php?f=18&t=62307

Notes

Tips for modeling

  • from https://forum.freecadweb.org/viewtopic.php?f=18&p=340874#p340494
  • Better use linear elements otherwise calculations are very time consuming
  • master/slave assignment:
    • The larger of the two surfaces should act as the master surface.
    • If the surfaces are of comparable size, the surface on the stiffer body should act as the master surface.
    • If the surfaces are of comparable size and stiffness, the surface with the coarser mesh should act as the master surface.

CalculiX

  • A very detailed CalculiX contact example. (link)
  • A very cool example found in the FreeCAD German subforum. (link)