Fixing Edges and Faces with the Edge2face and Comparison Options in HyperMesh

The geometry connected to a physical part is represented by a surface. A surface is a two-dimensional geometric object that can be utilised in automatic mesh generation. A surface always has one or more faces. Each face comprises a mathematical surface and edges. The edges help determine how much trimming would be needed for the surface. 

Often, any surface that has several faces is considered a single surface entity. Therefore any operation performed on the surface will affect all its faces. Edges define the perimeter of a surface. Edges can be different types like free, shared, suppressed and non-manifold

In this article, we are going to explore feature and comparison options that help improve the edges and faces of a geometrical model in Hypermesh. Instructions and step-by-step explanations are provided with examples for better understanding.

Editing Edges and Faces Using the Edge2face Option

This option will be used, when we want to edit any particular portion on the surface, after meshing the model. Basically, it will create a cut on the surface, based on the perimeter of the 2D mesh Elements. 

Steps to perform the Edge2face option:

1) Click Geom→ Lines→ Feature (ref Fig1).

 2) Now select the elements, by which its perimeter will turn into a feature line, then click on the create button.

 3. Disable the Mesh in the component and check the Feature lines as shown below:

4) Now we can trim the surface with the feature lines, by using the trim with lines option under the surface edit command (Shift + F9 or Geom→ surface edit).

• Select the trim with lines option from the surface editing list.
• Select the surface, which needs to be trimmed.
• Now select the free line (feature line)and ensure the normal to surface direction.

Click on the trim button to trim the surface with the selected feature line.

5) Feature lines can be deleted by using delete→ lines→ delete entity, after trimming the surface.

6) Now the trimmed surface (ref Fig2) can be edited as per our requirement.

Reason for ticking the checkboxes in the Feature panel (ref Fig1):

• Feature angle: This option allows to specify of the minimum angle, which can be created between the normals of two connected shell elements(ref Fig3). When the normal angle exceeds the specified feature angle value( ref Fig4), a detailed feature line is generated (ref Fig5).

If the X value(Normal angle) is greater than the Y value(Specified Feature angle), a detailed feature line will be created as shown below:

Note: The above shown Detailed feature lines are created with a Feature angle of 10 degrees. Hence the X value(Normal angle) will be greater than the Y value(Feature angle) 

• Ignore elements normal: This option will lead to ignoring the direction of the shell face normals and a detailed feature line is created between any two shell faces whose normals are more than the specified feature angle.
• Break angle: This option allows you to specify the minimum angle allowed between three points in a line. Line joints will be created whenever the line exceeds this specified break angle.