Re: [femm] Force calculation on an axisymmetric model

[Dave Squires <djsquires@xxxxxxxx>]

Just to confirm what Dave said, I did some tests where
Quickfield said there should be some force on an all
permanent magnet arrangement, but building it showed zero.
When the mesh is reduced to about 0.01 units around the area
of measurement the error went away and showed zero.
Please note that "zero" could be around 9-10N/m. So
expect an error margin of about 10N/m in any fine mesh
calculation. It could be plus or minus. So the conclusion
is that a fine mesh calculations gives more accurate results
with a tolerance of 10N/m or so.

Regards,
Dave Squires

Agnaldo Souza Pereira wrote:

> The greater forces arised from femm calculations, with
> a greater number of nodes.
>
> > Again, I'd guess that the difference arises solely
> from coarser the mesh
> > density in the quickfield solution.
> >
> > At any rate a good way to get an idea of how many
> digits you can believe in
> > either a femm or quickfield force computation is to
> integrate the stress on
> > different contours around the part that you are
> interested in. In an exact
> > solution, the results should be identical. However,
> the results from a
> > finite element solution, which is only approximate,
> will be slightly
> > different. The differences between contours give you
> an idea of the order
> > of the error in the calculations.
> >
> > Dave.
> >
> >
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