FEM RandbedingungStarrerKörper

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FEM RandbedingungStarrerKörper

Menüeintrag
Modell → Mechanische Randbedingungen und Belastungen → Randbedingung starrer Körper
Arbeitsbereich
FEM
Standardtastenkürzel
Keiner
Eingeführt in Version
1.0
Siehe auch
FEM RandbedingungVerschiebung

Beschreibung

Defines the CalculiX's rigid body constraint that constrains the motion of the nodes of a selected geometrical entity to the motion of a reference node whose location is defined by the user. In practice, this can be used to apply a boundary condition or load that will be propagated to the selected object. Since the reference node has rotational degrees of freedom, it's possible to apply a moment load or a rotational boundary condition to any face this way. The location of the reference node can be selected, if it's offset from a geometrical entity, a remote load (a force acting on a lever) can be applied.

Anwendung

  1. There are several ways to invoke the command:
    • Press the Rigid body constraint button.
    • Select the Model → Mechanical boundary conditions and loads → Rigid body constraint option from the menu.
  2. In the 3D view select the geometrical element(s) (vertices, edges or faces but not a mix of them) to which the constraint should be applied.
  3. Specify the coordinates of the reference node. After closing the task panel, a spherical symbol will show this location.
  4. Choose modes for the 3 translational and 3 rotational degrees of freedom (DOFs):
    • Free - default, no boundary condition or load on that DOF
    • Constraint - displacement/rotation boundary condition with a specified value (default: 0 = fixed) on that DOF - for rotation, one needs to set an axis (X, Y or Z) and specify the Angle
    • Load - force/moment load with a specified value on that DOF

Limitations


  • Currently, the moment units can be somewhat confusing. To apply 1 N*m, one needs to set 1 J in the input field (those units are equivalent).
  • The feature can be applied only to vertices, edges and faces for now, support for solids (to make whole volumes/parts rigid) should follow in the future.
  • The selected object is made rigid. To apply loads in a more flexible way, one would need to use CalculiX's distributing coupling constraints which are currently unsupported.

Hinweise

  • This constraint is the standard way of applying torque to arbitrary parts. The other options are the Local coordinate system (only for cylindrical faces) or a pair of forces but the rigid body constraint should be sufficient in pretty much all the cases.
  • No other constraints/boundary conditions should be applied to the nodes involved in a rigid body constraint.
  • When applying this constraint to a vertex or an edge, one should set a proper rotational DOF (in the case of an edge, the one that will prevent the rotation about it) to zero.
  • This feature uses the *RIGID BODY card in CalculiX.