Mesh error:'Two segments intersect'

[shoaibayjaz]

Hi
I am trying to mesh a volume imported from ACIS format. The geometry is of a thin fibre with varying cross-section along its length.
The error that shows up is '1 Wrong Volume' ; 'Two segements intersect'. I am unable to figure out which two segments intersect and how this affects the meshing. I was using tetrahedra element.

I have also attatched the file containing the geometry.

Thank you!

[escolano]

The messages like 'two segments' or 'two faces' intersects when meshing means that in order to generate the volume (tetrahedra) mesh it is necessary to generate the surfaces mesh (triangles) and before the surfaces its boundary curves (line elements), and because of the shape and your mesh size these segments or faces are intersected between them and is not possible to fill its interior.

The main problems is that do you have a very thin volume (a cylinder of radius=0.2 and length=600) and you are trying to generate a too coarse mesh with the default mesh size of 31 units in this case.
You must use mesh sizes according with the shape and curvature, for example a size similar to the radius =0.2 could be appropriated for this case.

There are some secondary problems, the surface 199 has problems to be meshed (and rendered).
If you use "Utilities->Repair model" it is enhanced.

Then mesh with general size=0.2 and a volume mesh could be created.

but in this case the surface mesh 'RFast' is not very good (visually) in some surfaces, it is better in this model to use 'Rsurf'
Utilities->Preferences... Meshing-Unstructured-surface: RSurf