Prescribed Displacement/Rotation

The subnode can be used to selectively constrain or prescribe degrees the of freedom of a Rigid Domain:

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One or several displacement components can be constrained or prescribed at an arbitrary point.

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One or several rotation components can be constrained.

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The rotation around a given axis can be prescribed.

The prescribed values that you specify are interpreted in the selected coordinate system.


	The Fixed Constraint and Prescribed Displacement/Rotation subnodes cannot be combined for a Rigid Domain.

Center of Rotation

The selection of the center of rotation only affects the prescribed displacements, not the rotations.

Select an option from the list: , , or.

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For , the center of rotation is taken as the one defined in the parent node.

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For select an — , , or .The available choices depend on physics interface and geometrical dimension. The constraints act at the centroid of the selected entities, which do not need to be related to rigid domain itself. As a special case, you can select a single point, and thus constrain that point


	Once chosen, a default Center of Rotation: Boundary, Center of Rotation: Edge, or Center of Rotation: Point subnode is automatically added.

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For , enter the ,Xc, in the table.

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

The center of rotation used is the sum of the vector obtained from any of the input methods and the offset vector.

Prescribed Displacement at Center of Rotation

Select one or several of the ,, and (3D components only) check boxes. Then enter a value or expression for u0x, u0y, and u0z (3D components).

Prescribed Rotation

Select an option from the list: , , or .


	For 2D components, and if Prescribed rotation is selected, enter a value or expression for the Angle of rotation φ0.

For 3D components:

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For select one or several of the , , and check boxes.

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For enter values or expressions in the table for the Ω . Then enter a value or expression for the φ0.

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You can add a Harmonic Perturbation subnode for specifying a harmonic variation of the values of the prescribed displacements and rotations in a frequency domain analysis of perturbation type.

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You can activate and deactivate this boundary condition by assigning it to a constraint group. See Load Cases in the Structural Mechanics Modeling chapter. Note that constraint groups only can be used when the constraints are pointwise, but not for weak constraints. This means that if is selected, any constraint group settings are ignored.

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You can assign the value of the prescribed displacement and rotation to a load group. See Load Cases in the Structural Mechanics Modeling chapter.

Reaction Force Settings

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

Select to use a unidirectional constraint for enforcing the 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.

Location in User Interface

Context Menus

Ribbon

Physics tab with node selected in the model tree:

When this node has been added once, it is no longer available for selection in the context menu or ribbon.