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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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11 hours ago, Salvatore 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, 

TIC.PNG

 

11 hours ago, Salvatore said:
  • The tstep is calculated by solver? Is possible have a fixed timestep?
  •  

Did you try with DT on NLPARM?

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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.

 

 

 

 

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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.

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22 hours ago, Salvatore 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. 

 

 

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@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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