FEM ConstraintRigidBody

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FEM ConstraintRigidBody

Menu location
Model → Mechanical boundary conditions and loads → Constraint rigid body
Workbenches
FEM
Default shortcut
None
Introduced in version
1.0
See also
FEM Constraint displacement

Description

Defines the CalculiX's rigid body constraint that constrains the motion of the nodes of a selected face 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 face. 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 face, a remote load (force acting on a lever) can be applied.

Usage

  1. There are several ways to invoke the command:
    • Press the Constraint rigid body button.
    • Select the Model → Mechanical boundary conditions and loads → Constraint rigid body option from the menu.
  2. In the 3D view select face(s) to which the constraint should be applied.
  3. Specify the coordinates of the reference node.
  4. Choose modes for the 3 translational and 3 rotational degrees of freedom (DOFs):
    1. Free - default, no boundary condition or load on that DOF
    2. Constraint - displacement/rotation boundary condition with a specified value (0 = fixed by default) - for rotation, one needs to set an axis (X, Y or Z) and specify the Angle
    3. Load - force/moment load with a specified value

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 faces for now, support for solids (to make whole volumes/parts rigid) should follow in the future.
  • The selected face 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.

Notes

  • No other constraints/boundary conditions should be applied to the nodes involved in a rigid body constraint.
  • This feature uses the *RIGID BODY card in CalculiX.