Creating Advanced Restraints

Advanced Restraints are generic restraints allowing you to fix any combination of available nodal degrees of freedom on arbitrary geometries. There are three translation degrees of freedom per node for continuum element meshes, and three translation and three rotation degrees of freedom per node for structural element meshes.

(this is an example)

means that there is no translation degree of freedom left in that direction.
means that there is no rotation degree of freedom left in the direction.

Make sure you fixed all the global degrees of freedom of your assembly, otherwise a global singularity will be detected at the time of the Static Computation (such a model is unsolvable). To allow you to easily correct the model (Static Analysis Cases only), the singular displacement of the assembly will be simulated and visualized after computation.

Advanced Restraint objects belong to Restraint objects sets.

Advanced Restraints 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
					virtual part

This task shows how to create an Advanced Restraint on a geometry.

You can use the sample20.CATAnalysis document from the samples directory for this task: a Finite Element Model containing a Static or Frequency Analysis Case.

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 Advanced Restraint icon

The Advanced Restraint dialog box is displayed.

2. You can change the identifier of the Advanced Restraint by editing the Name field, if needed.

3. Set the Axis System Type.

The Axis System Type combo list allows you to choose between Global, Implicit and User-defined Axis systems for defining the degrees of freedom directions:

Global: if you select the Global Axis system, the degree of freedom directions will be interpreted as relative to the fixed global rectangular coordinate system.

Implicit: if you select the Implicit Axis system, the degree of freedom directions will be interpreted as relative to a local variable coordinate system whose type depends on the support geometry.

User: if you select a User Axis system, the degree of freedom directions will be relative to the specified Axis system. Their interpretation will further depend on your Axis Type choice.

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

If you select the User-defined Axis system, the Local orientation combo box further allows you to choose between Cartesian, Cylindrical and Spherical Local Axis Orientations.

Cartesian: the degrees of freedom directions are relative to a fixed rectangular coordinate system aligned with the cartesian coordinate directions of the User-defined Axis.

Cylindrical: the degrees of freedom directions are relative to a local variable rectangular coordinate system aligned with the cylindrical coordinate directions of each point relative to the User-defined Axis.

Spherical: the degrees of freedom directions are relative to a local variable rectangular coordinate system aligned with the spherical coordinate directions of each point relative to the User-defined Axis.

4. Select the geometry support (a surface or an edge). Any selectable geometry is highlighted when you pass the cursor over it.

You can select several supports in sequence, to apply the Advanced Restraint to all supports simultaneously.
Symbols representing fixed degrees of freedom in all restrained directions for the selected geometry are visualized.

5. Activate the degrees of freedom which are to be fixed in the subsequent analysis.

You can fix up to six degrees of freedom per node:

Translation 1 = Translation in x
Translation 2 = Translation in y
Translation 3 = Translation in z
Rotation 1 = Rotation in x
Rotation 2 = Rotation in y
Rotation 3 = Rotation in z

6. Click OK to create the Advanced Restraint.
A Restraint object appears in the specification tree under the active Restraints objects set.

	You can either select the support and then set the Advanced Restraint specifications, or set the Advanced Restraint specifications and then select the support.
	If several Analysis Cases have been defined in the Finite Element Model, you must activate a Restraints objects set by clicking it in the features tree before creating an Advanced Restraint object.
	Restraints are required for Stress Analysis computations. They are optional for Modal Analysis computations (if not created, the program will compute vibration modes for the free, unrestrained part).
	Advanced Restraint objects can be edited by a double click on the corresponding object or icon in the features tree.

Make sure the computation is finished before starting any of the following operations.

Products Available in Analysis Workbench

The ELFINI Structural Analysis product offers the following additional features with a right mouse click (key 3):

on an Advanced Restraint object:

Restraint visualization on mesh: the translation of your Advanced Restraint object specifications into solver specifications can be visualized symbolically at the impacted mesh nodes, provided the mesh has been previously generated via a Compute action.

on a Restraints objects set:

	`Generate Image`: generates an image of the computed Restraint objects (along with translating all user-defined Restraints specs into explicit solver commands on mesh entities), by generating symbols for the nodal restraints imposed by the Restraints objects set. The image can be edited to include part or all of the options available.
	`Report`: the partial status and results of intermediate pre-processor computations are reported in HTML format. It represents a subset of the global Report capability and generates a partial report of the Restraints objects set Computation.

See Creating Clamps for more details.