Home Forums NextFEM Designer support forum Importing a mesh generated by gmesh

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    Luciano Jacinto

    Dear NextFEM admin:

    I tried to import a slab model meshed with gmesh into NextFEM using the API method importAbaqusCalculix().
    Because gmesh is a very reputed mesh generator, I thought that it would be very nice to integrate that software into NextFEM using the capability of Gmesh to export to Abaqus/Calculix and the capability of NextFEM to import from them.

    To test this possibility, I used a very simple slab model: a square simple supported slab, with spans of 5.0 meters and a load p = 12 kN/m2. Considering a modulus of elasticity E = 30 GPa, and a Poisson ratio of 0.15, the expected displacement at mid span is 0.0015 m, and the maximum moment is 12.7 kNm (estimated from Richard Bares Tables).

    Everything run well, including numerical results, but the color map of moments given by NextFEM (using OOFEM solver) has a bad aspect. (See ‘results.docx’ file.) Although the maximum moment is as expected, it seems that the interpolation between adjacent elements was not made properly.

    I attach the INP Calculix File and other relevant files.

    Any help would be greatly appreciated.

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    NextFEM Admin

    Dear Luciano,
    you obtain “bad” diagram because you don’t have aligned shell local axes. Every force/moment for shells is plotted against local axes for NextFEM Designer.
    We currently read the mesh given by Gmsh (not via API, but from GUI only).

    To solve the problem, align the local axes with Assign / Local axes command.
    we have free internal tria mesher. For regular slab as yours, a structured mesh (made by division) is more suitable. By using a mesh like the one you have, you’re implicitly introducing approximations in results, because finite elements involved (quad) are made to be more accurate when regular (e.g. square).

    Luciano Jacinto

    Thank you so much! That solved the problem!

    I used this very simple example to test the possibility of importing a mesh generated by Gmsh into NexFEM. In other more complicated cases, this possibility is very useful. Once more, thank you so much for your help and very quick support!

    PS: It would be great to have an API method like setShellLocalAxes() to align local axes in a Python script.

    NextFEM Admin

    Thanks, Luciano. In the next patch you’ll find alignShellXaxis API function.

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