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# Re: [femm] Force calculation on an axisymmetric model

- To: femm@egroups.com
- Subject: Re: [femm] Force calculation on an axisymmetric model
- From: Dave Squires <djsquires@plix.com>
- Date: Mon, 09 Oct 2000 08:22:40 -0700
- References: <3.0.5.32.20000929182911.00881400@sun.isec.pt> <3.0.5.32.20001006164352.008e5220@sun.isec.pt> <39DE046F.E1F4051D@foster-miller.com> <200010061834.QAA19402@if.ufrj.br> <39E1CDE2.2B958851@foster-miller.com> <200010091408.MAA12224@if.ufrj.br>

    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.
    > >
    > >
    > > -------------------------- eGroups Sponsor
    > >
    > >
    > >
    >

- References:
  - Force calculation on an axisymmetric model
    - From: Paulo José Gameiro Pereirinha <ppereiri@sun.isec.pt>
  - Re: [femm] Re: Force calculation on an axisymmetric model
    - From: Paulo José Gameiro Pereirinha <ppereiri@sun.isec.pt>
  - Re: [femm] Re: Force calculation on an axisymmetric model
    - From: David Meeker <dmeeker@foster-miller.com>
  - Re: [femm] Re: Force calculation on an axisymmetric model
    - From: Agnaldo Souza Pereira <agnaldo@if.ufrj.br>
  - Re: [femm] Force calculation on an axisymmetric model
    - From: David Meeker <dmeeker@foster-miller.com>
  - Re: [femm] Force calculation on an axisymmetric model
    - From: Agnaldo Souza Pereira <agnaldo@if.ufrj.br>

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