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hex meshing multi-surface solids

hex meshing multi-surface solids

hex meshing multi-surface solids

(OP)
Hi:
I have been trying to hex mesh a solid in my model that started out with some slivers and multi-curve areas. Other similar solids in the same model, but without the slivers etc. were hex-meshed reasonably well using the methods shown in Blas Molero's Hex mesh II tutorial. (Thanks Blas). Using the solid cleanup commands and combining curves the slivers are gone. All the surfaces in the solid were quad meshed with plot only elements. However, when I try to hex mesh the solid itself, the following message appears:

"Hex Mesh from Elements
Hex Mesh Solid
1 Solid(s) Selected...
Skipping Solid 122. Only true solids can be meshed, not multi-surface or multi-curve solids."

Is there a way to overcome this problem, say converting it back to a true solid?

I am using Femap 11.1.0 and the native geometry came from Solidworks 2015 via a Parasolid translation.

Thanks for any help.

Tom

RE: hex meshing multi-surface solids

Hi,

Did you try the Geometry / Solid / Stitch?

Seif Eddine Naffoussi, Stress Engineer
www.Innovamech.com
33650 Martillac û France

RE: hex meshing multi-surface solids

(OP)
Yes I did do some stitching. A list of the surfaces in the solid shows a couple of boundary surfaces with the underlying surfaces that I stitched together. I also made some combined curves (compositecurves) in order to make good mesh sizing along the curves.

Tom

RE: hex meshing multi-surface solids

Dear Tom,
The error message means that you are trying to mesh a NON-SOLID body: it seems that is a solid, but look to the ICON in the MODEL INFO TREE under GEOMETRY, you will see the diferences here:
1.- SOLID Body: this is the pure solid body, the only geometry that you can mesh with solid elements (please note the ICON style)
2.- SHEET Body: this is a colection of surfaces that DO NOT CREATE A SOLID fully closed, you can stitch all surfaces forming a sheet body using command GEOMETRY > SOLID > STITCH. If the stitching surfaces form a closed body, then the result will be not a sheet body, but a fully 3-D solid body. But if you have a GAP, the result will be a Sheet body, OK?.
3.- NonManifold-Add body: when you have surfaces in T-shape then PARASOLID can not stitch them in ONE Sheet body, but FEMAP provide the entity General Body Add using command GEOMETRY > SURFACE> Non-Manifold Add. Please take note of the ICON, you see that is different to the Sheet-Body or Solid-Body icon, OK?.

Then you can say: "My surfaces forms a closed solid body but when I issue command GEOMETRY > SOLID > STITCH gives error!!". Then use command GEOMETRY > SOLID > EXPLODE to create independent surfaces from a solid, and next issue command GEOMETRY > SOLID > CLEANUP to make sure all surfaces are clean, and finally use again GEOMETRY > SOLID > STITCH and if it is true your surfaces form a closed solid body then you will arrive for sure to a 3-D SOLID Body.



Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog de FEMAP & NX Nastran: http://iberisa.wordpress.com/

RE: hex meshing multi-surface solids

(OP)
Thanks Blas and Compositecurves:

It turns out from the icon that I was working with a sheet body.

In the end I went back to the native Solidworks file and did a better job of planning the dividing of the solids for hex meshing. This left me with only four or so small slivers. Then I used the Solid/Cleanup command on those solids but did not do any stitching. This allowed for a good hex mesh. Thanks Blas for your tutorials on Approach on Surface. This helped a lot to achieve a good mesh. For the first time in ages there were zero warnings. Usually I get some warnings about skew etc. The model ran well.

I was modeling a generic hatch from an offshore race boat:


In an accident these hatches often fail.

For your information, there is an F1H2O race organized by the same group as the Offshore; at Porto, Portugal on August 1 and 2. Both the Offshore and the formula 1 boat builders badly need engineering help (FEA) regarding their cockpit designs. They do not have the resources of the F1 cars. The race would be fun to watch.

Thanks again both of you for your help.

Tom

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