Jump to content

Geometric nonlinear - implicit

Recommended Posts

Looking at the .out file it is not obvious what the issue is. It is difficult, if not impossible to debug without the model. Perhaps you can share it with Altair support team through secure dropbox or Altair Connect.


Theses topics had the same issue:

My best guess is first try to run without friction.  Then activate the nonlinear expert system to aid in the convergence of small displacement nonlinear problems with analysis>control cards>param>expernl>yes or CNTSTB. Description from Optistruct Help:




Activates a nonlinear "expert system" that aids in the convergence of small displacement nonlinear problems (NLSTAT). This version is designed to facilitate obtaining converged, high accuracy solutions without much concern for computational time. The system monitors the convergence of nonlinear processes and, if needed, implements measures designed to improve convergence for poorly converging cases. These measures include: performing additional iterations, under-relaxation, automatic adjustment of the load increment, as well as backing off to the last convergent solution and retrying. This may lead to a large number of nonlinear iterations for poorly converging problems.



Additionally introduces temporary stabilization on contact interfaces (CONTACT or GAP(G) elements) that may improve nonlinear convergence, especially in cases where individual parts lack full support and are supported only by contact. The stabilization is applied only during incremental loading and is not present in the final solution for the respective nonlinear subcase. (Refer to the CNTSTB Bulk Data Entry for default and priority information).


Share this post

Link to post
Share on other sites

FYI, Post HM 2017.2.4 relevant nlgeom loadstep panel have been removed.Change the analysis type to Nonlinear Quasi-Static(NLSTAT) from NLGEOM and add the below card



NLOAD is not valid in NLSTAT, you can directly apply enforced displacement through SPC/D card

Simon Križnik likes this

Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

You are posting as a guest. If you have an account, please sign in.
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...