Error - "Non-linear solver failed to find equilibrium"
convergence issue while attempting to compress a specimen with large deformations using IMPLICIT Solver of Ls-Dyna
Hi @mohammad_basri,
To start, Implicit is much more sensitive than explicit so the debugging process can be a long, drawn out process. If you are doing a simple simulation that is in the range of seconds, consider an explicit simulation. If it's longer than that, then yeah, you will have to use Implicit.
Is the issue happening immediately or a little while into the simulation?
The link below has a lot of great tips for both debugging errors and improving implicit simulation performance. I would start with the control settings on slide 14 and go from there.
Let me know if you have any specific questions regarding this.
The reason for using Implicit code is to simulate a quasi-static compression problem.
This error comes after a while and not in the beginning. For a few iterations, it achieves equilibrium and it is after some iterations, it is unable to achieve equilibrium. After which it shows Error termination.
And, Yes, I have already studied these guidelines for Implicit and used the suggested control settings.
However, the result is more or less the same. I still get Error termination.
I am trying to compress a specimen and the process is similar to Crashbox crushing. During the analysis, it shows the following error:
"divergence (increasing translational residual norm) detected"
If you are getting an error in the middle of your simulation, it could be an issue with the material model or the contacts. Are there any contacts in this simulation? If so, that could definitely be the cause. This link may be helpful
https://www.dynasupport.com/howtos/implicit/implicit-contact-treatment
From my experience, implicit simulations require more than just baseline contact settings so you are probably going to need to activate the options ABC in the contact in LS-Prepost (below) and set IGAP to 1. IGAP has a huge effect on implicit contact stability.
I have already given and tried the IGAP =1 in Contact Card.
I am currently using Mortar Contacts.
I will try changing the contacts once.
also, do you have some idea about the control card CONTROL_IMPLICIT_SOLUTION? Since the solving process os governed by this itself, I believe there is something missing in that itself.
Could you share the pdf file to which the link you have shared? I don't have access to the site. And I really have an issue with non convergence of my implicit analysis
@ssdng Hmm, it seems the webpage that I originally linked is either down or no longer exists. Let me see if I can track it down for you.
Can you have a look at my Message file and suggest changes in the CONTROL_IMPLICIT_SOLUTION?
Did you send the message file to my email? I’m sorry, this slipped by me.
I had actually uploaded the file. But somehow it didn't. Can you share your email id?
Just change the extension of the file from .msg to .txt and upload it.
Hi!
Tell me pls, was the problem solved? Suppose I have something like it.
I am solving some simple along/across fiber tensile problems for composite.
Almost all of them (34 of 35) were solved ok, except 1 (so the problem i suppose in material card or contact - 1 tied to node to surf contact)
This material (mat_054) fails before stress riches XT (xt=518Mpa, fail on 350-400Mpa).
According to logs timestep falls below DTMIN (control_implicit auto) . But no idea why.
I suppose the problem is with convergence, but no idea how to fix this.
And I also got this error "Non-linear solver failed to find equilibrium"