Prescribed Displacement/Rotation

The node adds an edge, boundary, domain, or point condition to a model where the displacements and rotations are prescribed in one or more directions.

With this condition it is possible to prescribe one or more displacement components, as well as one or more rotational components, leaving the shell free to deform or rotate in the remaining directions.

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Prescribing all displacements and rotations to zero is equivalent to using a .

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Prescribing all displacements to zero is equivalent to a condition.

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Prescribing all rotations to zero is equivalent to the condition.

Coordinate System Selection

Select the coordinate system to use for specifying the prescribed displacement/rotation. The coordinate system selection is based on the geometric entity level.

Domains (Plate Interface)

From the list select from:

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(the default)

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Any additional user-defined coordinate system

Boundaries (Shell and Plate Interfaces)

From the list select from:

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(the default)

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(a predefined normal-tangential coordinate system)

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Any additional user-defined coordinate system

Edges (Shell Interface)

From the list select from:

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(the standard global coordinate system).

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(the default).

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Any additional user-defined coordinate system.

Points (Shell and Plate Interfaces)

From the list select from:

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(the default)

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Any additional user-defined coordinate system


	For details about the definition of local edge systems, see Local Edge System.

Face Defining the Local Orientations

This setting is used in conjunction with a and . If displacement or rotations is prescribed for an edge or point which is shared between boundaries, the local system can be ambiguous. Select the boundary which should define the local system. The default is .


	This section is available only for edges and points in the Shell interface.

Prescribed Displacement

To prescribe a displacement in a certain spatial direction (x, y, or z), select one or all of the , , and check boxes. Then enter a value or expression for the prescribed displacements u0x, u0y, or u0z.

Prescribed Rotations

Select a prescribed rotation from the list — , , or . Select:

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(the default) to leave the rotations unconstrained.

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to activate a prescribed rotation in a certain direction. Enter a value or expression for the prescribed rotation, θ, about the tangential directions and of the shell local system. The rotation is always interpreted the with respect to the shell local system, and independent of the Coordinate System Selection.

For geometric linearity, select one or both of the and check boxes to remove the constraint for the corresponding rotation component. If unchecked, the rotations are constrained to either the input value or to the default zero rotation. The status of the check boxes has no effect when the geometric nonlinearity is activated under the study settings. This is because the constraints for different rotation components are not independent of each other in the case of finite rotations.


	In 2D axisymmetry, there is only one input, the Prescribed rotation around the out-of-plane direction, Θ.

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to describe the rotation by prescribing the shell normal vector in the deformed configuration. Enter the components of the N0.


	For details, see Initial Values and Prescribed Values.

Constraint Settings

To display this section, click the button (

) and select in the dialog box.

In the COMSOL Multiphysics Reference Manual:

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Constraint Reaction Terms

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Weak Constraints

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Constraint Settings


	When Individual dependent variables is selected in the Apply reaction terms on list, the constraint forces are applied directly on the degrees of freedom, which are the displacements along the global coordinate axes. If you use this setting together with a local coordinate system, the results will be inconsistent since the constraint forces will not match the constraint orientation.

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You can add a Harmonic Perturbation subnode for specifying a harmonic variation of the values of the prescribed displacements 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.

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

Location in User Interface

Context Menus

Ribbon

Physics tab with selected: