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I have two parts, which need to be meshed. One part is located inside another. To simplify the problem, imagine two cubes: one inside another. enter image description here

Geometries are stored in STL files. From CAD point of view, one file contains an internal cube, another contains cube with a hole for an internal cube. All dimensions fits (there are no intersections). My task is to create a conformal tetrahedral mesh suitable for mechanical FEM analysis - without duplicated nodes on shared faces. Each element should contain information to which part it belongs. File format does not matter but Abaqus is preferred.

I decided to use gmsh, but I cannot mesh both parts together. I tried the following commands:

  1. File -> Open Internal cube
  2. Add volume to internal cube
  3. File -> Merge External cube
  4. Add volume to external cube

This produces mesh but elements in internal cube are duplicated. It looks like gmsh does not treat hole (in external cube) as a void. I also tried to use Coherence in gmsh but it failed with error:

Error : Self intersecting surface mesh, computing intersections (this could take a while)

Error : Surface mesh is wrong, cannot do the 3D mesh

I assume, that my geometries are fine:

How to create such a mesh which satisfy my requirements?

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closed as off-topic by Wolfgang Bangerth, nicoguaro, Christian Clason, Paul Jan 7 '16 at 15:20

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  • $\begingroup$ Can you have the shapes as SAT or IGS files? Did you check the normals for the inner hole? $\endgroup$ – nicoguaro Jan 6 '16 at 19:14
  • $\begingroup$ This is a question best asked on the gmsh forums or mailing lists. $\endgroup$ – Wolfgang Bangerth Jan 6 '16 at 20:12
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    $\begingroup$ You can use a cutting plane to change the geometry from toroidal to simply connected. Meshing becomes easier then. $\endgroup$ – Biswajit Banerjee Jan 7 '16 at 1:53
  • $\begingroup$ @nicoguaro: STL files are being made using our own software. And meshing should be perform automatic. Yes I can convert it to SAT but I would like to avoid it. $\endgroup$ – Krzysztof Bzowski Jan 7 '16 at 7:12
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    $\begingroup$ This is a discussion on GMSH mailing list that contains info on how to create CompSolids in CAD tools that will be meshed conformally in GMSH. onelab.info/pipermail/gmsh/2016/010238.html $\endgroup$ – Anton Menshov Jun 17 '18 at 23:28

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