RE: FSI using LS Pre Post time step problem
James M. Kennedy
Dear Hisyam,
See if these notes are of some help (this is an LS-DYNA question):
https://www.dynasupport.com/howtos/implicit/implicit-general-remarks
Sincerely,
James M. Kennedy
KBS2 Inc.
February 20, 2021
From: ls-pr...@googlegroups.com [mailto:ls-pr...@googlegroups.com] On Behalf Of shis...@gmail.com
Sent: Thursday, February 18, 2021 10:23 PM
To: LS-PrePost <ls-pr...@googlegroups.com>
Subject: FSI using LS Pre Post time step problem
Hello everyone,
I have one question, I encountered an error termination as below;
* Error 60004 (IMP+4)
*******************
* *
* - FATAL ERROR - *
* *
* Nonlinear solver failed to find equilibrium. *
* *
*******************
Writing out last converged state for implicit.
the only I change is the time step from 0.1 to 0.01. For 0.1 time step, it was ok with result. but when I change to 0.01 become an error.
Thank you in advance.
Hisyam
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James M. Kennedy
Dear Hisyam,
A comment I found that may be of some interest.
LS-DYNA's *static* implicit nonlinear solver has trouble converging for very tiny time steps
(or for steps where applied loads/displacements are held constant) because of our convergence
criterion. We require that the initial displacement and energy norms at the beginning of each
step be reduced by several orders of magnitude before the equilibrium iterations can "converge".
This approach fails in the case where the step begins (almost) in equilibrium. Then these norms
are already (nearly) zero, so reducing them further is difficult, and is sensitive to numerical
truncation error. Results will vary from computer to computer, and from single to double
precision versions.
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James M. Kennedy
Dear Manuel,
See if this is of some help:
Johansen, T., et al., "Overview, How to Set Up Implicit Analysis and Improve
Convergence", 2016 Nordic LS-DYNA Users Forum, Gothenburg, Sweden,
October, 2016.
Sincerely,
James M. Kennedy
KBS2 Inc.
March 5, 2021
From: Shahrul Hisyam Marwan [mailto:shis...@gmail.com]
Sent: Monday, March 01, 2021 1:47 AM
To: James M. Kennedy <j...@kbs2.com>
Cc: LS-PrePost <ls-pr...@googlegroups.com>; LS-DYNA2 <ls-d...@googlegroups.com>
Subject: Re: [LS-DYNA2] RE: FSI using LS Pre Post time step problem
Dear Mr. Kennedy,
Thank you for your kind words and a lot of information. I really appreciate it.
Best regards,
Shahrul Hisyam Marwan
James M. Kennedy
Dear Hisyam,
See if this is of some help:
Johansen, T., et al., "Overview, How to Set Up Implicit Analysis and Improve
Convergence", 2016 Nordic LS-DYNA Users Forum, Gothenburg, Sweden,
October, 2016.
Implicit analyses in LS-DYNA - ResearchGate
www.researchgate.net › post › attachment › download
Sincerely,
James M. Kennedy
KBS2 Inc.
March 5, 2021
From: Shahrul Hisyam Marwan [mailto:shis...@gmail.com]
Sent: Monday, March 01, 2021 1:47 AM
To: James M. Kennedy <j...@kbs2.com>
Cc: LS-PrePost <ls-pr...@googlegroups.com>; LS-DYNA2 <ls-d...@googlegroups.com>
Subject: Re: [LS-DYNA2] RE: FSI using LS Pre Post time step problem
Dear Mr. Kennedy,
Thank you for your kind words and a lot of information. I really appreciate it.
Best regards,
Shahrul Hisyam Marwan
On Sun, Feb 21, 2021 at 2:42 AM James M. Kennedy <j...@kbs2.com> wrote: