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g-iges for solid export

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Alex Per
2011-10-08
2013-04-22
  • Alex Per
    Alex Per
    2011-10-08

    Hi

    I am thinking of using BRL-CAD as a solid modeler for assemblies to be analyzed in a finite elements code.

    But I am facing a problem, it seems that the IGES export of BRL-CAD is surface export only.

    Considering the assembly ktank.g for instance, when I run :

    g-iges -m -a 1 -r 0.01 -o targ ktank.g tank, i would hope to get directory targ filled with the iges representation of each solid region used in object tank, but in fact i only get iges with surface representations…   is there a way to get solid iges exports for each region which is included in the object…?

    Best regards

    Alex

     
  • Sean Morrison
    Sean Morrison
    2011-10-14

    Alex,

    Alas, there presently isn't a way to get solid exports from the iges exporter.  It tessellates the model into a mesh and exports that as an iges surface.  It would be trivial write a script that exports each region individually, so you only have one surface per solid region, but you'd still then need to convert each one to a solid during FEA import.

    More usefully, though, the facetall.sh script (only in a source distribution) will pre-tessellate all individual regions into a mesh.  You could use that script and then export to some other format (such as dxf, stl, x3d, off, etc) for each individual object.  That might do what you're looking for.

    We have developed a path to go directly from BRL-CAD geometry description to a FEM but it requires the Cubit package from Sandia National Labs and a compile of our exporter.  Their license fee used to be around $100 USD, but I haven't checked in on them lately.  That path will convert every region to a mesh suitable for FEA using tessellation methods much superior to our own.  Example at http://brlcad.org/gallery/s/renderings/cubit.png.html

    Cheers!
    Sean

    p.s. We are working on a STEP exporter that will preserve solidity but that effort will not be available for some time.

     
  • Alex Per
    Alex Per
    2011-10-17

    Hi Sean

    Thanks for your reply :)

    I will try to see what i can do using g-stl -> admesh -> tetgen -> calculix ( abaqus  format input )

    And Cubit costs 300$ USD, not 100…    furtermore, i am not a US Citizen…    does Cubit alow for a direct abaqus inp export…?

    BRGDS

    Alex

     
  • Sean Morrison
    Sean Morrison
    2011-10-18

    Ah, good to know.  I'm not very familiar with their licensing requirements or export formats, but do know that their finite element meshing library is one of the best anywhere.  They hook to the ACIS engine for export, so if ACIS supports abaqus inp, then they will.  I don't know what other formats they (or ACIS) provide, however.  Sorry I can't be of much more help.

    Cheers!
    Sean