Assignment 1

Assignment 1

Objective

To carry out the geometry cleanup operation on three models.

Fig 1. Model 1 Fig 2. Model 2 Fig 3. Model 3

Challenges

1. The model should be free from free edges.
2. Convert the above models into refine geometry.
3. Clean the geometry.
4. Extract mid surface.
5. Clean mid surface geometry.
6. Ignore holes less than dia 5mm.
7. Create a 2D mesh with target length 5mm, min 3.5mm max 7mm.
8. And assign proper thickness, by creating a generic property.
9. Then Save in .hm format.

Reason for geometry cleanup in hypermesh

The very first step to start any CAE project is to import the CAD data. While the importation of CAD data, there occurs some geometric issues. Some geometric issues are,

• The gap present between adjacent surfaces.
• Two surfaces often contain gaps, misalignment, overlaps, etc.
• Appearance of free edges in the geometry.

To eliminate the geometric issues, the first step is to repair the CAD model by,

• Deleting the untrimmed surfaces
• Close missing surfaces
• Equivalence free edges
• Delete duplicate surfaces

Benefits of repairing

• Eliminating the errors in CAE model.
• Ensuring proper connctivity of mesh

Case set up and explanation

1. Fig 1. Model 1 opened in hypermesh window.

2.Check surface edges in the model. In hypermesh, surface edges are represented by four colour codes. Each code represent respective surface edges. Four types of surface edges: Free edges (red), Shared edges (green), Suppressed edges (blue), Non-manifold edges (yellow).

3.Remove the free edges that appear between two adjacent surfaces. Use surface edit option, to trim the surfaces.

4.Click Geometry -> quick edit (Press F11 key) and use toggle to change edge type within tolerance. Toggle edge, filler edge, replace point, surface edit options are used in repairing the geometry.

5. Generating mid surface

Geometry-> Midsurface-> Auto midsurface

6. 2D mesh criterion

7. After mesh, no free edges between the elements.

8. Element quality criteria

9. Assigned proper thickness, by creating a generic property.

10. The same procedure followed for model 2 and model 3.

Result and conclusion

1. The geometry cleanup process is performed on three models by correcting the free edges.
2. The mesh is been carried out on mid surface by keeping target size of 5mm.
3. With target size of 5mm, the element check criteria on minimum and maximum length is performed on three models.