Abaqus/CAE attempts to simplify the model by merging neighboring edges and faces when the selected parameters are exceeded. The redundant entities parameter can only be toggled on or off—there are no other settings for this parameter. Redundant entities do not add to the geometry of the model. Redundant entities include:
For example, Figure 1 contains four redundant edges and one redundant vertex. Virtual topology will merge the edges with the surrounding faces and merge the vertex with the surrounding edges, leaving only the underlying box. Figure 1. Redundant edges and vertices.
Keep in mind that redundant entities may define areas used by other tools within Abaqus/CAE. For example, the circular edge in Figure 1 may define a face for the application of a pressure load. The controls in the Create Virtual Topology dialog box are based entirely on geometric parameters; you should carefully review the changes made using virtual topology to make certain that none of the changed entities are required for other parts of the Abaqus/CAE model definition. By default, all the virtual topology parameters in the dialog box are active, as shown in Figure 2. The default values for the edge length, face size, stair feature, and blend radius are calculated based on the size of the selected part or part instance; the other criteria are dimensionless and suitable default values are provided. You can toggle off the controls for entities that you want to be ignored by virtual topology. For example, if you have small faces that are a critical component of the model, toggle off Faces smaller than. Figure 2. The Create Virtual Topology dialog box.
To help you review potential changes, each parameter in the dialog box contains tools that you can use to measure and highlight entities in the viewport that satisfy the corresponding geometric criteria. Items that are highlighted may not be changed if they conflict with other criteria or model requirements. To use the tools, click on the icons located to the right of each parameter in the Create Virtual Topology dialog box. The measure entities tools allow you to measure entities in the viewport. Abaqus/CAE displays the measured values in the message area; you can use the measurements to revise the parameter limits for your model. The highlight tools, such as Highlight Short Edges , indicate entities that satisfy the current parameter settings. For the Candidate Entities to Merge area of the Create Virtual Topology dialog box, the highlight tools indicate entities that may be merged with the surrounding geometry. The highlight tools do not account for the combination of parameters or any other factors in the model that may prevent the highlighted features from being merged with surrounding geometry. For example, small stair features must satisfy two parameters for replacement using automatic virtual topology:
Figure 3 shows the angles and the face dimension that make up a stair feature. If you use the highlight tool to view potential faces, Abaqus/CAE does not consider the angle measurements when selecting the faces to highlight. Figure 3. The face thickness (stair height), x, and the angles and create a stair feature.
The Curvature Controls for Combined Entities area of the Create Virtual Topology dialog box is used for combining corner angle and blend entities. The curvature control parameters and highlight tools indicate edges, vertices, or blends that will be retained—not replaced by virtual topology—using the current settings. The following examples explain how the curvature control parameters for corner angles and blends are interpreted by Abaqus/CAE.
For detailed instructions on how to use the Create Virtual Topology dialog box, see Creating virtual topology automatically. |