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Simple structural mechanics model does not converge

Posted 03.09.2015, 10:49 GMT-4 Studies & Solvers, Structural Mechanics Version 5.1 3 Replies

Levin Dieterle
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Hi,

unfortunately I can't find the reason, why my simple mechanical model does not converge. Can someone help? Thank you.

Kind regards,
Levin

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3 Replies Last Post 04.09.2015, 06:57 GMT-4
Edgar J. Kaiser Certified Consultant
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Posted: 9 years ago 03.09.2015, 12:58 GMT-4
Hi Levin,

I increased the tolerance factor in the 'Fully Coupled' node from 1 to 10 and it solves. This issue may arise from the large aspect ratio of the long thin beam.

Cheers
Edgar

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Hi Levin, I increased the tolerance factor in the 'Fully Coupled' node from 1 to 10 and it solves. This issue may arise from the large aspect ratio of the long thin beam. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Henrik Sönnerlind COMSOL Employee

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Posted: 9 years ago 04.09.2015, 03:04 GMT-4
Hi,

The model is ill-conditioned because it is undamped and the frequency response sweep passes close to a natural frequency. The solution exactly at a eigenfrequency is infinite, meaning that the dynamic stiffness matrix is singular there.

Edgar's solution makes it possible to solve somewhat closer to the singular point because the ill-conditioning check is modified somewhat, but it does not address the underlying problem.

Regards,
Henrik
Hi, The model is ill-conditioned because it is undamped and the frequency response sweep passes close to a natural frequency. The solution exactly at a eigenfrequency is infinite, meaning that the dynamic stiffness matrix is singular there. Edgar's solution makes it possible to solve somewhat closer to the singular point because the ill-conditioning check is modified somewhat, but it does not address the underlying problem. Regards, Henrik
Edgar J. Kaiser Certified Consultant
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Posted: 9 years ago 04.09.2015, 06:57 GMT-4
... yes the damping, I miss it at times, something to be looked at first ...

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
... yes the damping, I miss it at times, something to be looked at first ... -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com

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