Creating Rigid Spring Virtual Parts

A Rigid Spring Virtual Part is an elastic body connecting a specified point to a specified geometry, behaving as a six degree of freedom spring in series with a mass-less rigid body which will stiffly transmit actions (masses, restraints and loads) applied at the handle point, while stiffening the deformable body or bodies to which it is attached.

The Rigid Spring Virtual Part does not take into account the elastic deformability of the parts to which it is attached.

The program proceeds as follows:

	a node is created in coincidence with the specified handle point.
	a second node, offset from the first node, is created in a user-specified direction.
	the offset node is connected by a user-specified spring element to the handle node.
	all nodes of the specified geometry supports meshes are connected by rig-beam kinematical elements to the offset node.
	a set of rig-beam relations is generated between the offset node degree of freedom and the connected nodes degree of freedom.

The Rigid Virtual Part is built with Rigid Spider and Spring elements.

To know more about those elements, see Rigid Spider and Spring in the Finite Element Reference Guide.

Rigid Spring Virtual Parts can be applied to the following types of Supports:

Mechanical Feature	Geometrical Feature				Analysis Feature
Mechanical Feature	Point or Vertex	Curve or Edge	Surface or Face	Volume or Part	Analysis Feature

This task shows how to create a Rigid Spring Virtual Part between a point and a geometry support.

You can use the sample28.CATAnalysis document from the samples directory for this task: Finite Element Model containing a Static Analysis Case and computed corresponding Static Solution. A Part Design point was created on the associated CATPart document.

Before You Begin:
Go to View -> Render Style -> Customize View and make sure the Shading, Outlines and Materials options are active in the Custom View Modes dialog box.

1. Click the Rigid Spring Virtual Part icon

The Rigid Spring Virtual Part dialog box is displayed.

2. Select the cylindrical face of the hole as a geometry support.

3. Position the cursor on the Handler field in the Rigid Spring Virtual Part dialog box and select a point for the handler point (the handler point symbol appears as your cursor passes over it).

If you do not specifically select a point, the centroid will be used as the handler point.

When several virtual parts share a same handler point, only one finite element node is generated.

The Axis System Type combo box allows you to choose between Global and User-defined Axis systems, for entering components of the resultant moment vector.

	`Global`: if you select the Global Axis system, the components of the resultant moment vector will be interpreted as relative to the fixed global rectangular coordinate system.
	`User-defined`: if you select a User-defined Axis system, the components of the resultant moment vector will be interpreted as relative to the specified rectangular coordinate system.

To select a User-defined Axis system, you must activate an existing Axis by clicking it in the specification tree. Its name will then be automatically displayed in the Current Axis field.

4. Set the Axis system.

5. Enter values for the six degree of freedom spring constants.

6. Click OK to create the Spring Rigid Virtual Part.

The symbol appearing at the handler point represents the Rigid Spring Virtual Part.

A Rigid Spring Virtual Part Mesh.1 object appears in the specification tree under the active Nodes and Elements objects set.

You can select several geometry supports.
The Spring Rigid Virtual Part will connect all supports to the handle point and stiffly transmit all actions as a spring in series with a rigid body.