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Active Contributor
Simau
Posts: 32
Registered: ‎10-12-2011
Accepted Solution

Eigenvalues

6454 Views, 2 Replies
10-22-2011 10:25 AM

Hello,

 

In a dynamic calculation, what could be the main cause of this kind of message (see attached picture)

 

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Active Contributor
Simau
Posts: 32
Registered: ‎10-12-2011

Re: Eigenvalues

10-23-2011 06:26 AM in reply to: Simau

Hi,

 

I know that my question was badly formulated.

So what is the difference between response " Yes" or "Cancel"  and "No"

 

Somtimes,  if i choose "Cancel",  robot will run for a very long or endless time.

 

If i choose "No", will resutlts be correct and what is the difference between both choise

 

Regards

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Product Support
pp2008
Posts: 529
Registered: ‎06-23-2008

Re: Eigenvalues

10-23-2011 11:51 PM in reply to: Simau

Such message can be displayed when there are multiple similar eigenvalues (vibration frequencies in case of dynamic modal analysis) corresponding usually to local vibrations of some part of the structure. In such case  it may happen that during  iterations the order of such eigenvalues is changing and eigenvalues which were originally in the range of calculated ones will no longer be in this range. Such situation is detected by Sturm sequence check and reported as shown on the screen capture attached by you.

 

NO (Non) - corresponds to finishing modal analysis and passing to next load case without searching for "lost" eigenvalues

 

YES (Oui)- corresponds to internal increase of the range of searched eigenvalues and attempting to find the lost ones. After this increase and attempt another Sturm sequence check is done and if nothing is lost analysis is continued without any message. If some "lost" eigenvelues are still detected then this message is displayed again and further increase of the range of searched eigenvalues is possible

 

ESCAPE (Annuler) - corresponds to repetitive selection of YES - i.e. increasing the range of searched eigenvalues until none is "lost". In case of models containing a lot of slender bracings or other elements with local vibrations it may result in very long iterations because the number of such modes will be very high. Usually in such case these local vibrations can be ignored and there is no need to use this functionality.

 

If this post answer your question please click "Accept as Solution".
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Pawel Pulak
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