3 Steps to Create Midsurface Geometry

The goal of this post is to bring you up to speed on how to create midsurface geometry for finite element analysis. While the process requires numerous actions, each action can be generalized into one of 3 categories. Video explanations complement each section.

1) Extract Midsurfaces

Thin structures will be composed of numerous thin walls. Individual midsurfaces may be extracted manually, but automatic and semi-automatic methods can extract midsurfaces for numerous thin sections. The advantages of each method are given below.

Automatic Midsurface Extraction

This method traditionally works well for designs that have uniform thicknesses or have been through a stamping manufacturing process.

 

Semi-automatic Midsurface Extraction

This method works well for designs that have multiple thickness changes, non-uniform thicknesses and the walls have a large variation of position to one another.

 

Individual Midsurface Extraction

There may be the situation when certain midsurfaces were excluded from the automatic or semi-automatic and must be created manually. In other cases, when the extracted midsurfaces are poor and severely distorted, it is best to delete the midsurfaces and recreate it individually.

2) Free Edges

A free edge is an edge that is not connected to another edge or face. If a continuous mesh is intended at an edge and it happens to be a free edge, it can produce a discontinuous mesh. The goal is to resolve the necessary free edges.

Individually Resolving Free Edges

If it is one edge, closing a gap is as simple as taking a free edge and dragging it to a nearby edge or face. The benefit of this dynamic behavior is that you do not have to created and delete construction geometry each time an edge operation is performed.

Stitching

Suppose the scenario when an edge is already resting on an edge or face. A stitching function can be used to connect the free edge to the edge or face.

Extending Free Edges

After you have extracted numerous midsurfaces, there will be numerous free edges to resolve. Individually moving and closing each free edge is too time consuming. An automatic method can be leveraged to extend the free edges up to nearby edges or faces, and in addition, a simultaneous option to stitch the edges can be used.

 

3) Final Clean Up with Mesh Quality

To confirm the midsurface geometry is suitable, the resulting mesh must have elements that are within satisfactory levels of quality. In other words, nothing in the midsurface geometry should cause poorly distorted elements. With the mesh superimposed on the midsurface geometry, the mesh quality may be viewed and edits can be continuously made without having to delete and recreate the mesh.

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