Why is the definition of TSTEP necessary for Nonlinear Direct Transient Analysis?

cfuser
cfuser Altair Community Member
edited October 2020 in Community Q&A

Dear Support-Team,

I am currently working on a Nonlinear Direct Transient Analysis to be solved with OptiStruct. I have read in a variety of sources that for this kind of problem  NLPARM and TSTEP load collectors must be defined. I have also read that some entries made in NLPARM will override entries written into TSTEP. If this is so, why do I have to define a TSTEP load collector in the first place? Further, is my assumption correct that NINC-, DT-settings in NLPARM (also in NLADAPT and NLOUT) refer to time incrementation when performing a Nonliniear Direct Transient Analysis??

 

I'd be very grateful for your Help!

 

Cheers!

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Answers

  • tinh
    tinh Altair Community Member
    edited August 2019

    They (software developers) don't merge those 2 cards because some features just need one of them.

    It is about data organization, i think so.

  • cfuser
    cfuser Altair Community Member
    edited August 2019

    First of all, thanks for your reply tinh!

     

    I understand what you are getting at. Still, I'm not quite clear about one thing. In TSTEP I am defining ' time step parameters for control and intervals at which a solution will be generated and output in transient analysis' (quote from OptiStruct Help-webpage on Bulk Data Entry TSTEP). I understand what the different parameters are meant to do (N, DT, NO and so forth). But when I define them and leave similar parameters in NLPARM blank intentionally to avoid overriding the solver won't stick to the defined parameters. For example, when I define N=1000 and DT=0.001 in TSTEP I would expect to have 1000 increments solved by OptiStruct. The Out-file shows, that a lot less increments are actually solved. Even when I put DIRECT=yes in NLADAPT to specify fixed increments.

     

    Thinking about it, I still have a lot of stuff I am not sure about regarding HyperMesh/OptiStruct.

     

    Maybe somebody can clear things up for me? :)/emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />

  • Rahul Rajan_21763
    Rahul Rajan_21763 New Altair Community Member
    edited October 2020

    Please refer the material shared in below post for Nonlinear Direct Transient Analysis.

    https://community.altair.com/community?id=community_question&sys_id=5266003a1b2bd0908017dc61ec4bcba1

     

  • cfuser
    cfuser Altair Community Member
    edited August 2019

    Hello Rahul,

    thank you for your reply.

     

    Cheers!

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