[MBDyn-users] Static Analysis

David Cross (Civ, ARL/VTD) david.m.cross2 at us.army.mil
Fri Jul 9 15:43:25 CEST 2010

Thank you.  That should help me.

Another question...Im modeling flapping wing dynamics, and I am exciting 
motion at the natural frequency whose mode shape corresponds most 
closely to a flapping motion.  I was wondering if there is a way to 
prescribe proportional damping...say 1% of the structural stiffness??

Thanks again for all of your helpful advice.  Regards,


masarati at aero.polimi.it wrote:
>> David,
>> please always reply on the list.
>> The issue is strange, during static analysis the derivatives phase
>> should be' skipped (as far as I know).
> Derivatives are always performed.  However, it is correct that for static
> analysis they may pose some issues.  What you can do is either:
> - make sure the model is initially unloaded (at T = initial time), and
> load grows regularly to its final value; or
> - increase "derivatives tolerance" above the error that's computed during
> this phase.
> The latter approach is not that clean, resulting in some "fake" transient
> taking place from the first step on (since the model is static, so the
> transient would be purely numerical).  However, a well-behaving model
> should recover in just a few steps.
> Cheers, p.
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