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#38119 - 09/29/10 06:10 AM Non-convergence of analysis
rajeev_nagpal Offline
Member

Registered: 04/03/10
Posts: 49
Loc: india
Hi all,
what should i do when my analysis is not converging?
should i ignore friction or is there any other suitable approach?

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#38120 - 09/29/10 06:13 AM Re: Non-convergence of analysis [Re: rajeev_nagpal]
MoverZ Offline
Member

Registered: 11/22/06
Posts: 1195
Loc: Hants, UK
Try searching this site for Convergance. Lots of threads have covered this.

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#38339 - 10/11/10 11:02 PM Re: Non-convergence of analysis [Re: MoverZ]
Parag Offline
Member

Registered: 12/26/05
Posts: 7
Loc: Baroda
Dear All,
I am not sure it is correct or not but I follow the following sequence to get rid of this problem.

1. Reduce Friction stiffness.

2. Remove the friction factor from REST supports which are lifting.

3. Remove friction factor from Guide and Axial stops.

Please give your comments/suggestions

Regards,

Parag Dharkar
_________________________
Regards,
Parag Dharkar

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#38348 - 10/12/10 05:39 AM Re: Non-convergence of analysis [Re: Parag]
Richard Ay Offline
Member

Registered: 12/13/99
Posts: 6226
Loc: Houston, Texas, USA
Usually you can achieve convergence by reducing the "friction stiffness" and increasing the other "friction tolerances".
_________________________
Regards,
Richard Ay - Consultant

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#38352 - 10/12/10 06:43 AM Re: Non-convergence of analysis [Re: Parag]
Dave Diehl Offline
Member

Registered: 12/14/99
Posts: 2382
Loc: Houston, TX, USA
As you reduce friction stiffness and increase tolerance you might converge but at the expense of a less accurate solution.
Someone else posted this point earlier - only consider friction on restraints that carry weight as they have a normal load (and friction) from the start. Other restraints (e.g. guides) do not restrict motion (due to friction) until the system closes the gap and creates a horizontal load. Those horizontal friction effects are less certain than the deadweight supports. This is especially true for occasional (and horizontal) loads such as wind.
_________________________
Dave Diehl

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#38355 - 10/12/10 07:03 AM Re: Non-convergence of analysis [Re: Dave Diehl]
danb Offline
Member

Registered: 04/22/05
Posts: 1453
Loc: ...
Dave, I agree that altering friction stiffness it may lead to a less accurate solution.
I recently checked a such a system. I changed back the friction stiffness to default. Curious thing, a spring hanger that previously had 4000 N ope load, changed the ope load to nearly 8000 N.

I prefer other means.

Best regard,


_________________________
Dan

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