Week 3

The objective of this project is to perform meshing for a given hood model using ANSA. The model is cleaned and checked for errors, then using the given element size, is meshed accordingly.

For any meshing process, the following steps are necessary.

1. Geometry checks
2. Surface cleaning (if any)
3. Boundary flagging
4. Meshing

Model

Geometry checks

The geometry check is done using the checks dropbox and selecting the geoemtry option. There are many errors in the geometry, so surface cleaning is needed.

Surface cleaning

The first step is to patch all the holes in the geometry and extra surfaces, represented by single cones open in red lines all across the surface.

When there are open edges, we can patch them using some tools such as:

1. Coons - Surface patch
2. Fill hole - Cons
3. New - Faces

The Coons tool is used to patch holes that are separate entities in the same surface. The rectangular boxes with it's whole surface missing, can be patched using this tool. Select all the edges in the geometry patch and click the middle mouse button to preview a surface creation patch.

All the other extrusions across the surface of the model are deleted. Then open edges and single cons inside the geometry are corrected using the topo option.

A geometry check is performed again and the remaining extra surfaces are errors can be automatically fixed by ANSA itself, by right clicking and selecting fix option.

After this, the geometry is checked for symmetry using the Rm.Dbl option. If any surface is not symmetrical even within 80% parameter check, that surface is corrected and the other surfaces would be left out for the symmetry option meshing.

Here we need to note that, we are taking the mid surface option of the inner panel with a thickness that is half of the inner panel itself, 0.75 mm. We can create this mid surface using the offset option or the mid surface option itself. For now we can use the offset option.

The negative sign is provided to reverse the direction of the offset. The top portion of the inner panel is alone selected using the feature angle option. After that, any entity in the mid surface plane is selected and using the neighbours all option we can extract the complete mid surface plane of the inner panel. It is this plane on which we are going to perform the meshing operation. The boundary setting is performed afterwards when needed.

Meshing

The required element size for the whole goemetry is 5 mm.

All elements are mixed mesh.

Now, the meshing process can be started by clicking the mesh icon in the right top corner to switch to mesh module.

Appropriate lengths are given using the length option. Now, we are going to just work on one side of the geometry and leave the rest unsymmetrical parts alone so that we can use the best mesh option. After that we can replicate the mesh on one side to the other using the symmetry option in the transform tab.

If there are parts that are not connected to the surface after the symmetry option is performed, just use the paste bounds option to paste those elements alone.

After the meshing is done, it is separated from the geometry it is attached to, using the release option. With that, the mesh is separated from the whole geometry and is a separate entity.

Now, we need to setup the hemming process, step by step.

Hemming process

1. The outer panel and inner panel is excluded from the geometry by their PIDs

2. The outer panel is skinned for a mid surface plane using the mid surface option

3. Separate material IDs are created to the inner panel PID

4. The inner and outer panels' mid surface planes are taken and the outline of the outer panel is projected onto the inner panel surface.

5. The outlines are used as reference and the outer panel areas outside the boundaries are deleted until the fillet of the outer panel. The inner panel extra surfaces are also deleted outside the created boundary margin.

6. The projected boundary of the inner panel is pasted to the projected boundary of the outer panel

7. After errors have been cleaned, if any, the complete hemming boundary is selected

8. A separate PID for this hemming region is given with a thickness of 2.25 mm, as the formula for hemming thickness is (2*outer thickness+inner thickness). The same material ID (mild steel) is given to this hemming region PID too.

With that, we can see three PIDs for the outer and inner panel setup, which confirms that the hemming process is done.

Thus, we have successfully created a structural analysis mesh for the inner panel and separated it from the part and then finished the hemming process of the hood.