How to increase the number of iterations for non linear analysis

Sanjay Dinker_21074
Sanjay Dinker_21074 Altair Community Member
edited August 2022 in Community Q&A

Hello,

 

I am trying to solve a simple cantilever problem. 
The force input is specified using TLOAD1 card. I have 13 data points in the force curve from 0 to 650N. 

During the non linear simulation, the solution converges after 21 iterations. At this stage, the force of around 50N is applied. 

I am trying to increase the number of iterations using NINC parameters in NLPARAM card. However, it is not working out. 

Is there a way to increase the number of iterations?

I have attached the .out file as well. 

If you want more information, let me know.

Thanks, 

Sanjay

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Best Answer

  • Robinson Ferrari_20451
    Robinson Ferrari_20451
    Altair Employee
    edited August 2022 Answer ✓

    Hi Sanjay,

    Your model is converging after 20 increments and 84 iterations.

    NINC in NLPARM means the total force applied to your model will be split by NINC for the first increment. For instance, if you are using NINC=100 the first increment will be 0.01 (which means 6.5N in your case). You can also define DT directly as 0.01 instead.

    In NLPARM you can define MAXITER (but not for the purpose you want, this is for convergence). You can add NLADAPT card, and specify DTMAX = 0.01, for instance. So, your model will have at least 100 increments (can be more if any cutback happens).

    For using all the load applied be sure you are specifying the correct total value for 'time' and using TTERM accordingly in NLPARM as well. Since you are running in NLSTAT actually you can apply the load directly, without any TLOAD, and then NLADAPT will 'split' your curve.
    Please let me know if works for you.

    Thank you very much,

Answers

  • Robinson Ferrari_20451
    Robinson Ferrari_20451
    Altair Employee
    edited August 2022 Answer ✓

    Hi Sanjay,

    Your model is converging after 20 increments and 84 iterations.

    NINC in NLPARM means the total force applied to your model will be split by NINC for the first increment. For instance, if you are using NINC=100 the first increment will be 0.01 (which means 6.5N in your case). You can also define DT directly as 0.01 instead.

    In NLPARM you can define MAXITER (but not for the purpose you want, this is for convergence). You can add NLADAPT card, and specify DTMAX = 0.01, for instance. So, your model will have at least 100 increments (can be more if any cutback happens).

    For using all the load applied be sure you are specifying the correct total value for 'time' and using TTERM accordingly in NLPARM as well. Since you are running in NLSTAT actually you can apply the load directly, without any TLOAD, and then NLADAPT will 'split' your curve.
    Please let me know if works for you.

    Thank you very much,

  • Sanjay Dinker_21074
    Sanjay Dinker_21074 Altair Community Member
    edited August 2022

    Hello Robinson, 

     

    Thanks for the help. I did use NLADAPT and changed the 'time', now the solver is using all the force as intended. 

     

    Regards,

    Sanjay 

  • Robinson Ferrari_20451
    Robinson Ferrari_20451
    Altair Employee
    edited August 2022
    Sanjay Dinker_21074 said:

    Hello Robinson, 

     

    Thanks for the help. I did use NLADAPT and changed the 'time', now the solver is using all the force as intended. 

     

    Regards,

    Sanjay 

    Hi Sanjay, Thank you for your feedback. Please consider accepting the solution and mark it as correct to help others with similar issues (if it resolved your issue). Thank you very much,

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