The Rigid Connector is a boundary condition for modeling rigid regions and kinematic constraints such as prescribed rigid rotations. The selected points will move as a single rigid object.

You can add the Rigid Connector node at the edge (2D: boundary) and point levels.

The Global coordinate system is selected by default. The Coordinate system list contains all applicable coordinate systems in the model. Prescribed displacements or rotations are specified along the axes of this coordinate system. It is also used for defining the axis directions of the moment of inertia tensor of the Mass and Moment of Inertia subnode.

Select a Center of rotation — Automatic, Centroid of selected entities, or User defined.

Select the Offset check box to add an optional offset vector to the definition of the center of rotation. Enter values for the offset vector Xoffset.

Specify the rotation at the center of rotation. Select from the By list: Free (the default), Constrained rotation, or Prescribed rotation.

For Constrained rotation select one or more of the available check boxes to enforce zero rotation about the corresponding axis in the selected coordinate system:

In some cases it can be useful to not constrain the displacement in a certain direction. To do so, select a local Coordinate system for specifying the directions in which the degree of freedom will be released. The Coordinate system list contains only applicable coordinate systems in the model.

The section Released Degrees of Freedom is only shown if the check box Use weak constraints for rigid-flexible connection in the section Constrain Settings is not enabled.

Select Evaluate reaction forces to compute the reaction force caused by a prescribed motion. The default is to not compute the reaction force. When selected, the prescribed motion is implemented as a weak constraint.

Select Apply reaction only on rigid body variables to use a unidirectional constraint for enforcing a prescribed motion. The default is that bidirectional constraints are used. This setting is useful in a situation where a bidirectional constraint would give an unwanted coupling in the equations. This would happen if the prescribed value of the motion is a variable solved for in other equations.

Select Use symmetric formulation for geometric nonlinearity to force all matrix contributions from the rigid connector and its subnodes to be symmetric.

On the boundaries where the rigid connector is coupled to a flexible material, all nodes on such a boundary are constrained to move as a rigid body. As a default these constraints are implemented as pointwise constraints. If you want to use a weak constraint formulation, select Use weak constraints for rigid-flexible connection.

This formulation cannot be combined with the Flexible formulation of the rigid connector, which in itself is a special form of weak constraint.

On the points where the rigid connector is coupled to a flexible material, all nodes are constrained to move as a rigid body. As a default, these constraints are implemented as pointwise constraints. If you want to use a weak constraint formulation, select Use weak constraints for rigid-flexible connection.

It is possible to couple rigid connectors to each other. In the Connect to list, you can select any rigid connector defined in the Solid Mechanics, Multibody Dynamics, or Shell interfaces as being rigidly connected to the current one.

Select Group dependent variables in solver — From physics interface (default), Yes, or No, to choose how to group in the solver sequence the dependent variables added by the Rigid Connector feature.

Physics tab with Beam or Pipe Mechanics selected: