Femap Tips and Tricks

Geometry and Mesh Associativity

With Femap you can import CAD and FEA models from a wide variety of sources.

To import a CAD model select the File / Import / Geometry… menu option and browse and select the CAD file you wish to import. Femap then provides the option to specify a geometry scale factor if desired, select OK.

To import an FEA model select the File / Import / Analysis Model… menu option, select the Analysis Format in the Import Form and click OK. Now browse to and select the corresponding FEA model for the CAD geometry imported earlier.

geometry-and-mesh-associativity-1 The CAD and FEA models should now be superimposed. However, the independent import paths will break any associativity there may have been between the model types previously. Lack of associativity limits some modeling capabilities, particularly if you wish to take advantage of geometry entities to create corresponding FEA entities such as loads or constraints. You can see this if you create a geometry constraint and try to expand it to the FEA entities.

In the menu select Model / Constraint / On Surface… and click OK. Select a surface to constrain in the Entity Selector dialog, and click OK, and OK again to create fixed constraints, then Cancel.

geometry-and-mesh-associativity-2

Select the menu option Model / Constraint / Expand… and click OK.

The command fails to execute successfully and a warning message is issued in the Messages pane.

However, in Femap you can re-associate corresponding CAD and FEA modeling data, for both solid and shell type models, and overcome these problems.

Select the menu option Modify / Associativity / Automatic…, Select All elements and click OK, then Select All solids and click OK, and OK again in the Automatic Geometry Associativity dialog.

The geometry and FEA models have now been re-associated. This can be verified by expanding the geometry constraint as before.

Select the menu option Model / Constraint / Expand… and click OK.

Now the constraints have been expanded to the associated FEA entities.

geometry-and-mesh-associativity-3

So from just about any source, corresponding CAD and FEA models can be imported into Femap and associativity between them restored.

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