Prescribed Displacement/Rotation

Prescribed Displacement/Rotation

The node adds an edge (3D), boundary (2D), or point (2D and 3D) condition where the displacements and rotations are prescribed in one or more directions.

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If a prescribed displacement or rotation is not activated in any direction, this is the same as a constraint.

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If zero displacements and rotations are prescribed, this is the same as a .

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If only zero displacements are prescribed, this is the same as a constraint.

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If only zero rotations are prescribed, this is the same as a constraint.

Coordinate System Selection

Specify the coordinate system to use for specifying the prescribed displacement/rotation. See the section for Edge Load.

Prescribed Displacement

Select one or all of the ,, and for 3D models, check boxes. Then enter a value or expression for u0, v0, and for 3D models, w0.

Prescribed Rotation


	For 2D models, to define a prescribed rotation select the Prescribed in out of plane direction check box and enter a value or expression for θ0z.

For 3D models, 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. Enter values or expressions for the prescribed rotation vector θ. When the study is geometrically linear, you directly prescribe the individual components of the rotation vector.Under , select one or several 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 geometric nonlinearity is activated under the study settings. This is because the constraints put on different rotation components are not independent of each other in the case of finite rotations. Here, θ should be interpreted as a rotation vector in the given coordinate system. The norm of the vector is the angle of rotation, and the orientation of the axis of rotation is given by the vector components.


	In a geometrically nonlinear analysis in 3D, you should prescribe all three components of the rotation vector. Prescribing only one or two components may not give unique results, since finite rotations are not commutative.

Constraint Settings

To display this section, click the button (

) and select . Location in User Interface

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

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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.

(Point)

Physics tab with selected: