convergence criterion

Altair Forum User

Hello,

 

i have a problem with my non-linear simulation. In my Assambly are two sheets of shell elements, which are connected with skrews (realised with beam and rbe2-Elements).

Between these sheets i designed 'contact surfaces', according this discription:

 

http://training.altairuniversity.com/analysis/structural/nonlinear/contact-analysis-bolted-flange-nlstat/

 

 

My run summary told me:

 

A fatal error has occurred during computations:

  *** ERROR #  941 ***
  NON-CONVERGENT NONLINEAR ITERATIONS FOR SUBCASE         6

  Suggestions:



  ANALYSIS COMPLETED.

 

Results are available. I beleive, that the displacements are to big for the solver. Can this be serious?

 

My Questions:

Is it true, that the Solver put the Force step by step higher?

How can i read the intermediate data out?

How can i change the convergence criterion?

 

best regards

Altair Forum User

Hi BeMa86

 

Can you increase the NINC and MAXITER values in NLPARM card and check if your run converges or not?

Also, use PARAM,EXPERTNL,YES and CONTPRM,STIFF,SOFT

Rahul_P1

See - Linear and Non linear analysis, iteration, increment, step etc explanation topic in the optistruct forum. 

 

http://forum.altairhyperworks.com/index.php?/topic/13300-linear-and-non-linear-analysis-iteration-increment-step-etc-explanation/ 

 

Also see User's Considerations for Nonlinear Convergence in help - Altair OptiStruct > User's Guide > Structural Finite Element Analysis > Solution Sequences > Nonlinear Quasi-Static Analysis

Altair Forum User

Thanks a lot.

I change the distance of the two sheets and now it works perfectly. The distance now is bigger and the offsets of the elements are adepted.

I don´t understand the reason for convergence.