A SIMULIA e-Learning Resource
Created using Abaqus 6.9 and 6.12

The Virtual Topology toolset allows you to ignore details, such as very small faces and edges, when you mesh a part or a part instance; it is a convenient method for creating a clean, well-formed mesh

In some cases parts contain details such as very small faces and edges. These features can be important for the detailed machining and packaging design of the component; however, they may be redundant in the numerical analysis if they have little impact on the mechanics of the problem being studied. Indeed, these small details may unduly constrain the generation of the mesh, resulting in a poor mesh or a finer mesh density. In some circumstances small faces and edges can be significant if they occur in a region of interest where you need a fine mesh. However, in most cases the details add nothing to the analysis, and you want Abaqus/CAE to ignore them during the mesh generation process and during the analysis. The automatic virtual topology tool allows you to do this quickly and easily.

The topology of a part is its composition from faces, edges, and vertices. The Virtual Topology toolset (Tools->Virtual Topology in the Mesh module) allows you to manipulate this topology and create a simplified form for the purpose of meshing. This simplified form is different from the real geometry and is called “virtual topology.” The faces and edges that result from the manipulation are said to be “virtual” and they are relevant for meshing purposes only.  If you do wish to modify the actual geometry use the Geometry Edit toolset (Tools->Geometry Edit in the Part module).

Narrated Video

The video below shows an example of using the automatic virtual topology tool to remove stair-like features.

This video was recorded using Abaqus 6.9 and is also included in the Introduction to Abaqus 6.9 web-based training site.

Now You try it!

Click the icon below to download the attached file, VirtualTopologyStairFeatures-Lens-StepbyStep-Abaqus612.pdf.  Follow the included step-by-step instructions to practice using virtual topology to smoothly mesh over stair-like geometry.     

This exercise was produced using Abaqus 6.12.

More about Virtual topology

The automatic virtual topology tool allows you to do more than smooth over stair-like features.  Using the same workflow demonstrated above, you can also abstract away:
- Short edges
- Small faces
- Narrow faces with a large aspect ratio
- Faces with small corner angles
- Redundant edges and vertices

Abaqus/CAE treats virtual topology in the same way that it treats standard geometry. For example, you can do the following:
- Partition geometry with virtual topology
- Use the Geometry Edit toolset on virtual topology
- Use Part module tools on geometry with virtual topology, such as extrude, sweep, and blend

However, adding you cannot mesh regions that contain virtual topology using the following techniques:
- Two-dimensional free meshing with quadrilateral or quadrilateral-dominated elements using the medial axis algorithm
- Three-dimensional swept meshing using the medial axis algorithm
- Two-dimensional structured meshing if the region to be meshed is not bounded by four corners
- Three-dimensional structured meshing if the region to be meshed is not bounded by six sides

References:

-- “The Virtual Topology toolset,” Chapter 75 of the Abaqus/CAE 6.12 User's Manual

-- SIMULIA training class:  Abaqus/CAE: Geometry Import and Meshing

-- More SIMULIA e-Learning Resources  --