FEM ConstraintContact: Difference between revisions

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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 can be estimated as 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 that penetrates into the master face and therefore experiences more deformation.
* The *CONTACT PAIR card is used for modeling contact in CalculiX. The constraint uses Face-to-Face penalty contact and the contact formulation is explained in detail at http://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node112.html
* The *CONTACT PAIR card is used for modeling contact in CalculiX. The constraint uses Face-to-Face penalty contact and the contact formulation is explained in detail at http://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node112.html
* Overview for different contact types: https://forum.freecadweb.org/viewtopic.php?f=18&t=15699&start=90#p188736
* Overview of different contact types: https://forum.freecadweb.org/viewtopic.php?f=18&t=15699&start=90#p188736
* Further interesting informations:
* Further interesting information:
** https://forum.freecadweb.org/viewtopic.php?f=18&t=23102#p180709 and following posts !!!
** https://forum.freecadweb.org/viewtopic.php?f=18&t=23102#p180709 and following posts !!!
** https://forum.freecadweb.org/viewtopic.php?f=18&t=20276
** https://forum.freecadweb.org/viewtopic.php?f=18&t=20276
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* A very cool example found in the FreeCAD German subforum. ([https://forum.freecadweb.org/viewtopic.php?f=13&t=39663&start=10#p337254 link])
* An interesting example found in the FreeCAD German subforum. ([https://forum.freecadweb.org/viewtopic.php?f=13&t=39663&start=10#p337254 link])





Revision as of 10:36, 26 September 2023

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
  • Because 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. See Forum discussion.

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)
  • An interesting example found in the FreeCAD German subforum. (link)