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The direct meshing of CAD models with finite elements is now quite common in CAE.

If a certain CAD system, like SolidWorks, is used for constructing the geometry, then all geometric parts, like surfaces and bodies are well-connected, but for the stress or multiphysics analysis, the engineer generally faces two tasks:

  • Cleaning up the geometry, that is, the geometry bodies often have faces with very small areas compared to the model dimensions that are best removed.

  • Defeaturing the geometry, that is, certain geometric features may also best be removed for an analysis.

We presented on the use of ADINA for cleaning up a geometry earlier and focus now on the second task.

CAD models often contain details that are not needed for finite element analysis. Having unnecessary features in a model leads to increased complexity and a larger model in terms of the number of elements. Defeaturing is thus an important tool of a pre-processor that enables the removal of geometric features to achieve a more effective model for performing the analysis.

A feature on a solid model is commonly referred as either a "boss" (added material) or a "cut" (removed material). For example, a typical "cut" would be a hole and a typical "boss" would be an extruded profile off a face. Features vary from simple to complex, as can be seen in the examples below where the BODY DEFEATURE tool in the ADINA User Interface (AUI) is used to remove these features. Move your mouse over each figure to see it after the BODY DEFEATURE tool has been applied.

Figure 1  Removal of "cuts" (holes) on a piston model

Figure 2  Removal of "bosses" on a toner cartridge model

Figure 3  Removal of a feature (refueling tip) on a Mirage 2000 jet fighter model

The BODY DEFEATURE tool in the AUI, which acts on an ADINA-M Parasolid body, can be used automatically or manually. In automatic mode, a face area threshold is specified and all faces with areas below the threshold are removed. In manual mode, a list of body faces defining a feature (or features) to be removed is specified.

Note that this tool that acts directly on the geometry may not be well suited for removal of so-called "small features" (small edges and/or faces) of the geometry. The BODY CLEANUP tool which works on the topological representation of an ADINA-M body is more effective for that purpose.

These two capabilities, the Body Cleanup option and the Body Defeature option, in the ADINA system are very powerful tools to work on a given geometry to prepare the geometry for finite element meshing and an effective analysis. The ADINA meshing options then directly work on this geometry for any of the ADINA analysis capabilities, including those for multiphysics solutions.

CAD, CAE, meshing, geometry, solid body, topological representation, defeaturing, small features, multiphysics

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