General Mechanical

General Mechanical

convergence problem.

    • moeenkhurram
      Subscriber

      Hi, i am running simulation with model having 3.8 million node, static structural non linear analysis on 8 cores ,122 gb ram system, it seem not converging , any suggestion for convergence ?


      and should I keep simulation running ?






       


    • jj77
      Subscriber

      It seems that contacts are a bit on and off, so could be due to many reasons, causing problems with convergence.


      Also at one iteration the model moves a lot so to much movement could cause contacts to be on and off and they never catch properly.


      So that I think is the main issue here. TO address this:


       


      I would suggest to use sub steps say 20 initial/minimum and maximum 100 say, so to apply the load gradually.


      Also one can put an enforced displacement in first step to get the contacts to activate nicely (easier with imposed motion), and then in a second step start applying the load. 


       


      (if this does not help post again with images of your model so we can have a look). 



       

    • moeenkhurram
      Subscriber

      Thank you for the reply , i am  wondering if i can upload the model here ? and kindly have a look as it take too much time to solve and i want to be everything ok before next run 


      Thank you

    • jj77
      Subscriber

      I would not be able to solve this as I use a student version, but if you want upload and someone else might have a look.


      https://forum.ansys.com/forums/topic/saving-sharing-of-working-project-files-in-wbpz-format/


      As I said the above suggestions should help.

    • moeenkhurram
      Subscriber

       


      Also one can put an enforced displacement in first step to get the contacts to activate nicely (easier with imposed motion), and then in a second step start applying the load. 



       it doesnt have any loads its just press fit/ pre loading analysis of wind turbine bearing 


       



       


      i have 3 contact where is press fit applies 



       


      and after contact initial status one contact had too much penetration , so i made as formulation as Normal Lagrange  


    • jj77
      Subscriber

      Use many more substeps like I said. Contact stiffness,might be an issue also if it is to high (try standard contact (not Norm Lag.).


       


      That is it for me - weekend now and time to do something else than work -

    • moeenkhurram
      Subscriber

      thank you !

    • moeenkhurram
      Subscriber

      I ran the simulation again as you suggested , what do you  think , will it converge at some point? thank you in advance  


    • peteroznewman
      Subscriber

      A good approach to making sure the contact definitions are working well is to solve the model with a coarse mesh. When that is converging nicely, then refine the mesh in the areas you need finer spatial resolution. That way you don't spend a lot of time waiting on a model that will not converge to learn that sad fact.


      Have you requested 3 or more Newton-Raphson Residual plots under the Solution Information folder?  Those are very helpful for convergence diagnostic purposes.


       

    • moeenkhurram
      Subscriber

      @peter thank you for the good advises

    • moeenkhurram
      Subscriber

      Hi peter , i have many contacts and i don't know  which one is causing the  convergence problem , is there any why to know about that?


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