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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

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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.