Hi Onur,

Thanks for your encouragement!

The bad element orientation occurs when an element has a wrong order of vertices leading to negative volume. However this is not your case.

The real problem is that sfepy has no shell elements (yet) - it has 2D elements like triangles, but those are meant to be used in 2D problems, not in 3D like you try. That also answers why there is no thickness...

On the other hand, you might be lucky, as I have recently implemented a Mooney-Rivlin membrane element (membrane = no bending stiffness), which I want to put soon into the master repository. In the meantime, you can try using thin volume elements for your test, if it is possible.

In a longer run, I would like to have the shell elements in sfepy as well, but I know almost nothing about the underlying theory, so any help in this field would be very appreciated :)


----- Reply message -----
From: "onur alpay" <alp...@gmail.com>
To: <sfep...@googlegroups.com>
Subject: Hollow Cylinder Analysis
Date: Sun, Apr 17, 2011 15:10

Hi All,

We are working on the sfepy for about a month. First of all I would like to thank all the developers.

For an example application we have handled a hollow thin cylinder which is subjected to inner pressure.

We have created below files for mesh and run.

But we have some simple questions :).

Our first question is the thickness of the 2_3 Triangular shell elements. We could not find a place the enter the thickness of the tria elements. Sfepy is working quite well with out a thickness input :). But it would be great if we can type it some how...

The second question is about the element orientation. For the same study we are creating a mesh on some other mesher programs and convert the mesh to *.mesh file. But sfepy is throwing Bad Element Orientation! error for this nice mesh :). The only work around could done but using different element size for the same geometry. With enough elements sfepy could re-orient the elements successfully. But we are helpless on using a 3 dimensional geometry. sfepy simply does not re orient the mesh even for different size of elements... :)

Any help would be greatly appreciated.
rc, keep up the good work! Thanks,

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