Bearing universal connection for rotor dynamics (SOL 414)

You can use the Bearing universal connection command to create, maintain, and simulate bearings in your Simcenter Nastran rotor dynamic analyses. Like other types of universal connections, the bearing universal connection allows you to create, edit, and realize (mesh) multiple bearings at once.

When you model a rotor using a 3D mesh, you can realize (mesh) the connection using CBEAR2 + RBE2 spider(s) elements. When you model a rotor using a 2D axisymmetric mesh with Fourier elements, you can realize (mesh) the connection using CBEAR2 + FOU3 + RBE3 spider(s) elements.

Note:

If you plan to model a rotor using a 2D axisymmetric mesh with Fourier elements and CBEAR2 + FOU3 + RBE3 spider(s) elements, you must set 2D Solid Option to ZX Plane, Z Axis or XY Plane, X Axis in the New FEM/Edit FEM dialog box.

2D Fourier multi-harmonic model with bearing universal connections	3D recombined model

Targets and target configurations

To create a bearing connection, you must first define the connection's targets. The targets are the points, nodes, or mesh points between which the software creates the elements that represent the bearing.

The target configuration you define controls how the software creates elements when you realize (mesh) the connection. Consider the following example in a 2D Fourier multi-harmonic model where you want to realize (mesh) the connection using CBEAR2 + FOU3 + RBE3 spider(s) elements:

To create	Do the following	Example
A CBEAR2+FOU3 element combination with no RBE3 element	Define Target 1 using Single Point to select an existing node on the 2D rotor axis.Define Target 2 using Single Point to select a node that is collinear with Target 1 such that Target 1 and Target 2 are perpendicular to the 2D rotor axis.When you realize (mesh) the bearing universal connection, select CBEAR2 + FOU3 + RBE3 spider(s).The software creates a projected node on the rotor axis using Target 2 and creates a FOU3 element between the projected node and Target 2. The software then creates a CBEAR2 element between the projected node and the existing node at Target 1 along the rotor axis.Because you created a connection without using a spider to define the targets, the software does not create a RBE3 element.
A CBEAR2+FOU3 element combination with a connecting RBE3 element	Define Target 1 using Single Point to select an existing node on the 2D rotor axis.Define Target 2 using Spider.For Center Selection, choose Manual and select a second existing node; this node must be coincident with the node used to define Target 1.If a coincident node, point, or mesh point does not exist, you can create a coincident point by clicking Create New Point .For Legs Selection, select several nodes of interest, such as nodes along the outer radius of the bearing connection.When you realize (mesh) the bearing universal connection, select CBEAR2 + FOU3 + RBE3 spider(s).The software creates a projected node on the rotor axis using the leg nodes of Target 2. The software also creates a CBEAR2 element between Target 1 and Target 2. The software then meshes the spider legs using a combination of FOU3+RBE3 elements, where the RBE3 elements connect the spider center to the projected nodes on the rotor axis and the FOU3 elements connect the projected nodes on the rotor axis to the coincident node at Target 1.Because you created a connection using a spider to define the connection's targets, the software creates RBE3 elements.

Axis

After defining the connection's targets, you must choose an axis about which the bearing's physical properties, such as stiffness and damping, are defined. When you realize (mesh) the connection, the coordinate system you use to define the axis is stored as mesh associated data for each mesh of CBEAR2 elements.

Bearing connection elements

After creating a universal connection, you must create the connection elements (that is, realize or mesh the connections) before solving the model.

The following table shows the valid combinations of elements when realizing (meshing) a bearing connection:

To model rotors	Select this element type	Realized (meshed) connection
Using a 2D axisymmetric mesh	**CBEAR2 + FOU3 + RBE3 spider(s)**Note: To realize (mesh) the connection using this combination of elements, you must set 2D Solid Option to ZX Plane, Z Axis or XY Plane, X Axis in the New FEM/Edit FEM dialog box.	(1) CBEAR2 element, along rotor axis(2) RBE3 element, coincident with CBEAR2, on rotor axis(3) FOU3 element, perpendicular to rotor axis
Using a 3D mesh	CBEAR2 + RBE2 spider(s)	(1) CBEAR2 element, on rotor axis.(2) RBE2 element

When you realize (mesh) the bearing connection manually using the Connection Elements command, you can create a new PBEAR2 physical property, or select or edit an existing one. The software then assigns the PBEAR2 physical property to the mesh collector that contains the CBEAR2 elements. Within the PBEAR2 physical property, you can define the type of bearing as well as stiffness, damping, and mass.

For more information, see the PBEAR2 bulk entry.

Note:

When you realize (mesh) the bearing connection automatically using the Automatic Connection Elements command, you cannot edit the physical property assigned to the mesh collector that contains the CBEAR2 elements at the same time you realize (mesh) the connection. You must edit or create the physical property after you realize (mesh) the connection as explained in Define rotor bearing or bushing properties.

For more information, see Creating connection elements on a rotor model (SOL 414).

Where do I find it?

Bearing Connection command

Application	Pre/Post
Prerequisite	A FEM or assembly FEM file as the work part and displayed partSimcenter Nastran as the specified solverRotor Dynamics as the specified analysis typeTo realize a bearing universal connection as CBEAR2 + FOU3 + RBE3 spider(s), 2D Solid Option is set to a plane and axis
Command Finder	Bearing Connection

Connection Elements command

Application	Pre/Post
Prerequisites	A FEM or assembly FEM file as the work part and displayed part
Command Finder	Connection Elements

Automatic Connection Elements command

Application	Pre/Post
Prerequisites	A FEM or assembly FEM file as the work part and displayed part
Command Finder	Automatic Connection Elements

How do I

Realize (mesh) universal connections

Create and edit universal connections

Learn more

Universal connections

Managing element-associated data for universal connections (Abaqus)

Local spider element targets in universal connections

Using bushing universal connections in rotor dynamics (SOL 414)

Clinch universal connections in the LS-DYNA environment

Look up more details

Universal connection elements

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

Simcenter 3D tutorials

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Bearing universal connection for rotor dynamics (SOL 414), Simcenter 3D 2021.1 Series

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