Shock Absorber

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

Hi everyone,

i tried to implement shock absorber in a shock analysis in optistruct.

I use tutorial in order to set non linear tranisient analysis.

I implement with table1d and pbusht the curve ForceVSdisplacement and applying a force i have checked if the the curves is right.

Then i have to checked if my model with this non linear springs has a right answer to established input.

 

In this case the model is loaded with an initial displacement and a gravity. 

 

Finally i hate to load model with a curves VelocityVSTime.

Now i'm stopped at check problem.

 

 

My doubt are:

  • the initial dislacement is inserted with IC and TIC in model but in the result there isn't initial dipslacement. Why?
  • The tstep is calculated by solver? Is possible have a fixed timestep?
  • maybe more simple simulate this problem with a explicit solver as Radioss?

 

Thank you for the answeres


 

 

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited April 2018
    Altair Forum User said:

    • the initial dislacement is inserted with IC and TIC in model but in the result there isn't initial dipslacement. Why?
    •  

    Hi,

     

    In your model, I see you have applied Initial velocity and in the results it can be seen, 

    <?xml version="1.0" encoding="UTF-8"?>TIC.PNG

     

    Altair Forum User said:

    • The tstep is calculated by solver? Is possible have a fixed timestep?
    •  

    Did you try with DT on NLPARM?

  • Salvatore
    Salvatore Altair Community Member
    edited April 2018

    Hi Prakash,

    i agree with you, i have tested also with velocity as TIC, but i don't read this oscillation in my model both with velocity and displacements.

    have you modified something? 

     

    Regarding Tstep, i have modified Dt on NLPARM but with this parameter i modify only initial time incrmement. i would have costant time increment. is it possible??

     

    Furthermore i have modified also TTerm because my analysis has to last 0.5s.

     

     

    Thank you for fast answer.

     

     

     

     

  • Salvatore
    Salvatore Altair Community Member
    edited April 2018

    Hi prakash,

    i have changed type of analysis ans now i'm using a geom non linear analysis.

    In this way i have control on tstep thorug TSTEPNL.

     

    But i haven't resolved the problem of IC.

     

    Can you help me?

     

    thenk you.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited April 2018

    @Salvatore

     

    OK, can you share the updated file, please?

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited April 2018
    Altair Forum User said:

    i agree with you, i have tested also with velocity as TIC, but i don't read this oscillation in my model both with velocity and displacements.

    have you modified something? 

    yes, I deleted the existing and recreated another one.

     

    Regarding time increment, I will let you know. 

     

     

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited April 2018

    @Salvatore

     

    You can use NLADAPT with DIRECT= YES which Adopts fixed time increment. In case of divergence, the run will stop immediately.

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