Rigid Connector

The is a boundary condition for modeling rigid regions and kinematic constraints such as prescribed rigid rotations. The selected boundaries will move as a single rigid object, irrespective of whether they are geometrically adjacent or not.

If the study step is geometrically nonlinear, the rigid connector takes finite rotations into account. The feature is similar to the rigid connectors in the Beam and Shell interfaces. Rigid connectors from Beam, Shell, and Solid Mechanics interfaces can be attached to each other.

You can add functionality to the rigid connector through the following subnodes:

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Applied Force (Rigid Connector) to apply a force in given point.

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Applied Moment (Rigid Connector) to apply a moment.

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Mass and Moment of Inertia (Rigid Connector) to add extra mass and moment of inertia in a given point.

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Spring Foundation (Rigid Connector) to add a translational or rotational spring or damper in a given point.

The node is only available with some COMSOL products (see http://www.comsol.com/products/specifications/).


	In versions prior to 4.4, it was also possible to add a Rigid Domain subnode to the Rigid Connector. This node still appears and functions when you open an old model where it was used, but it is not possible add a new one. The functionality has been superseded by the more powerful concept of a Rigid Domain as a material model. For information about the old functionality, see the documentation for version 4.3b or earlier.

Coordinate System Selection

The is selected by default. The list contains any additional coordinate systems that the model includes. Prescribed displacements and 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 subnode.

Pair Selection

If this node is selected from the menu, choose the pair to use. An identity pair has to be created first. The rigid connector applies to the common part of the boundaries, and makes the parts behave as if there were an infinitely stiff layer between them.

Center of Rotation

The center of rotation serves two purposes.

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If you prescribe the displacement of the rigid connector, this is the place where it is fixed.

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Results are interpreted with respect to the center of rotation.

Select a —, , or .

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For the center of rotation is at the geometrical center of the selected geometrical objects.

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For select an — , , or . The available choices depend on physics interface and geometrical dimension. The center of rotation is located at the centroid of the selected entities, which do not need to be related to rigid connector itself. As a special case, you can select a single point, and thus use that point as center of rotation.


	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 , in the XC table enter coordinates based on space dimension.

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

To define a prescribed displacement at the center of rotation for each space direction, select one or several of the available check boxes then enter values or expressions for the prescribed displacements. The direction coordinate names can vary depending on the selected coordinate system.

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u0x

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u0y

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For 3D components: u0z

Prescribed Rotation at Center of Rotation

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


	For 2D components, the Constrained rotation and Prescribed rotation at center of rotation is always about the z-axis, so no component selection is necessary.

Constrained Rotation (3D Components)

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

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Prescribed Rotation at Center of Rotation

For enter an φ0. For 3D components also enter an Ω for the , , and coordinates.

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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 the rigid connector 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 and rotation to a load group. See Load Cases in the Structural Mechanics Modeling chapter.

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Rigid Connector Theory

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Harmonic Perturbation

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Load Cases


	Assembly with a Hinge: Application Library path Structural_Mechanics_Module/Connectors_and_Mechanisms/hinge_assembly

Location in User Interface

Context Menus

Ribbon

Physics tab with selected: