Creating Iso-Static Restraints

Iso-static Restraints are statically definite restraints allowing you to simply support a body.

(this is an example of a part iso-statically restrained)

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

Iso-static Restraint objects belong to Restraint objects sets.

The program automatically chooses three points and restrains some of their degrees of freedom according to the 3-2-1 rule. The resulting boundary condition prevents the body from rigid-body translations and rotations, without over-constraining it.

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.

This task shows how to create an Iso-Static Restraint on a body.

You can use the sample00.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 Isostatic Restraint icon

.
The Isostatic Restraint dialog box is displayed.

2. You can change the identifier of the Iso-static Restraint by editing the Name field.

3. Click OK in the Iso-static Restraint dialog box to create the Iso-static Restraint.
An Isostatic.1 object appears in the specification tree under the active Restraints objects set.

An Iso-static symbol appears on the geometry.

You can double-click the Iso-static symbol on the geometry or the Isostatic.1 object in the specification tree, to display the Iso-static Restraint dialog box and modify the Name, if needed.

	You can either select the support and then set the Iso-static Restraint specifications, or set the Iso-static 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 Iso-static 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).
	Iso-static 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 Iso-Static Restraint object:

Iso-static Restraint Visualization on Mesh: the translation of your Iso-static 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.