FEM ConstraintContact

    From FreeCAD Documentation

    FEM ConstraintContact.svg FEM ConstraintContact

    Menu location
    Model → Mechanical boundary conditions and loads → Contact constraint
    Default shortcut
    Introduced in version
    See also
    FEM Constraint fixed


    Creates a FEM constraint for contact between 2 surfaces.


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


    • 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.


    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.


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