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Suppressed edges and export geometry

Hello all,

I think I have seen similar questions to this one, however I do not think there has been a clear answer. As most users do, I find very helpful to simplify my geometries within hypermesh by suppressing lines that are not needed or will create problems during the meshing process. Since our company uses more than one pre-processor (as most do), sometimes there is a need to export the geometry that has been processed (i.e. cleaned) in Hypermesh to a different preprocessor like PATRAN or ANSYS etc. in the form of an IGES or STEP file. The export is performed nicely but the suppressed lines or curves are still visible on our geometry when the file is imported in say PATRAN, thus destroying all the work done before in order to simplify the geometry. Is there an option to avoid this or it is unavoidable?

Second question (has been answered in the past): There is a popular demand to have the geometry included when exporting a bdf (NASTRAN) file from Hypermesh. Even better: If there are no legal issues, it would be extremely useful to be able to export our work directly as a db (PATRAN) file, although there will be compatibility issues between different versions. OK, having the geometry WITH the bdf export will be a killer. Do you know when this will be possible?

Thank you.

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tinh

But why do you have to use PATRAN or ANSYS to preprocess?

why do you have to export geom within nastran bdf, or export work to db file?

QuyNguyenDai

Nastran, as FE solver, is good. But Patran is bad, very bad comparing to Hyperworks. Patran is 'dying' software!

Hyperworks can do alot of geometrical works, but not AS POWERFUL AS CAD softwares.

If you buy Hyperworks just to do this job, your choice is not good.

mvass

Gentlemen,

thank you for your replies. Although I did not receive an answer about including the geometry into the bdf (possible?) and the appearance of suppressed geometrical edges in a exported model, I will comment your replies without starting a perpetual discussion about the 'pros' of one program over the other.

I fully agree that PATRAN is an obsolete and problematic software in terms of pre-processing and geometry manipulation. However, if you are using NASTRAN as your solver (as mentioned before), defining your loads and BCs in PATRAN is sometimes the only way to go since we are talking about packages from the same company, although I will agree that even this has its problems sometimes (i.e. not all NASTRAN cards are supported by PATRAN). Second, PATRAN has been used by many companies for years; tons of work has been done for customisation and thousands of problems have been solved by their engineers or subcontractors, so asking them to switch to a different software and translate their work into it is in most cases an insane request (in terms of time and costs). No matter how good this pre-processor is. And yes, I fully agree that Hypermesh is by far better.

We all know that there is no 'silver bullet' software that can satisfy the needs of every single engineer and eradicate competition. All have 'pros' and 'cons' and in most cases companies are trying to get the best from two (or three) worlds; for example geometry manipulation and meshing in hypermesh and export to PATRAN for the rest, or export directly to a solver like NASTRAN or other from hypermesh etc. Also, bare in mind that Hypermesh is more like a 'universal' pre-processor and it is not possible to account for all cards and solutions that a solver from a different company (MSC NASTRAN) can offer.

In the above sense, it would be nice to have some more aid from hypermesh since there is a growing number of professionals who appreciate its features for geometry manipulation and meshing. The rest is simply a personal or company choice.

Thank you.

tinh

Yes, we are here to help you to use hypermesh for pre-processing tasks

so please tell us namely what you will do with PATRAN/ANSYS

we'll know whether we can do it by hypermesh or not

Mario_21478

Hello,

bdf is a pure FE format, as i know it isn't possible to include any geometry informations. (exceptions are e.g. comments like HM use it for connectors).

HM doesn't eliminate supressed edges (you can always unsupress suressed lines), since they are needed for working geometry (background geometry).

It isn't possible to export geometry without supressed edged, since geometry formats don't know this type of geometry.

But there is almost always a way to work with clean geometry, it is a question of model types and good will.

Best regards,

Mario

mvass

bdf is a pure FE format, as i know it isn't possible to include any geometry informations. (exceptions are e.g. comments like HM use it for connectors).

Yes, my thoughts exactly. But (as usual) I thought about it after posting my question.

HM doesn't eliminate supressed edges (you can always unsupress suressed lines), since they are needed for working geometry (background geometry)

True. The suppressed edge is part of the geometry, so when you export it, it's still there. I was thinking if there was a way not to include it when exporting to .iges or .stp, but I guess there isn't.

As to PATRAN, probably importing the bdf, then the geometry and associating the elements/nodes to the imported geometry is the only way I can think of getting both the mesh and the geometry (although I cannot guarantee that this procedure won't have any drawbacks/defects).

Thank you all for your contribution.