How to set up a quasi-static problem in Radioss?

Altair Forum User

Hi all,

From the manual, for static or slow dynamic computations where the duration of the study is long, implicit method should be used. So how to set up a quasi-static problem in Radioss? 

 

Any detailed example?

 

Thank you

Roy

gopal_rathore

Hi,

Both explicit and implicit solver can be used to perform a quasistatic run. Ideal is to use implicit solver considering the nature of problem which is almost tending towards static. 

You can have a look over the radioss examples in help for solving such cases eg. like dummy positioning etc. are given in detail in help

Altair Forum User

Hi Roy,

As Gopal mentioned , please go through Example 16 - Dummy Positioning in Help Menu where the model is solved using explicit and implicit computations. 

As a general note implicit Solution is RADIOSS is more to complement the Explicit Solution.  So we suggest to use it only for specific cases like Spring Back.  For other generic Implicit Non-linear cases, it is recommended to use OptiStruct.

pohan

Hi.

I managed to set up a quasi-static problem in Radioss with the engine file like that

/VERS/2017
/RUN/stfac 2/0/
3000.00000000000    
/ANIM/VECT/VEL
/ANIM/SHELL/TENS/STRESS/MEMB
/ANIM/SHELL/TENS/STRESS/BEND
/ANIM/SHELL/TENS/STRESS/UPPER
/ANIM/SHELL/TENS/STRESS/LOWER
/ANIM/SHELL/TENS/STRESS/ALL
/ANIM/ELEM/EPSP
/ANIM/ELEM/VONM
/ANIM/DT
0.000000000000000    25.0000000000000    
/PRINT/-500      
/TFILE/0         
25.0000000000000    
/STOP
0.000000000000000    0.000000000000000    0.000000000000000    1          1         
/MON/ON
/ANIM/SHELL/EPSP/UPPER
/ANIM/SHELL/EPSP/LOWER
/ANIM/NODA/DMAS
/DT/NODA/CST/0
0.900000000000000    0.000000000000000   
/IMPL/DT/1
0          0.000000000000000    0          0.000000000000000   
/IMPL/DT/STOP
0.000000000000000    0.000000000000000   
/IMPL/QSTAT
/IMPL/SOLVER/7         
2          0          0          0.000000000000000  

 

But there are only 2 cycles. How could I deal with this?

Altair Forum User

Hi Pohan,

Can you try running the same in OptiStruct?.

Altair Forum User

Altair Forum User said:

Hi Roy,

As Gopal mentioned , please go through Example 16 - Dummy Positioning in Help Menu where the model is solved using explicit and implicit computations. 

As a general note implicit Solution is RADIOSS is more to complement the Explicit Solution.  So we suggest to use it only for specific cases like Spring Back.  For other generic Implicit Non-linear cases, it is recommended to use OptiStruct.

Hi George,

I want to simulate the quasi-static compression testing problem. The compression speed was about 2mm/min and the whole process took about 10 minutes. I think the problem should be solved with Radioss implicit solver. Do you think so? And do you have some advice?

 

Thank you 

Roy

Altair Forum User

Hi Roy,

I would suggest you to try a non-linear transient analysis in OptiStruct. 

pohan

Altair Forum User said:

Hi Pohan,

Can you try running the same in OptiStruct?.

Hi George.

I tried but it was not better.

pohan

Hi George, do you have any solution?

Altair Forum User

Hi Pohan,

This seems like the solution might have converged in two cycles. You can try varying the implicit options.

I'm attaching a sample engine file. Please replace the implicit keywords with the attached ones and try running.

Unable to find an attachment - read this blog

pohan

Thank George.

Do you have any sample engine file for a quasi static implicit problem

Altair Forum User

Hi Pohan,

Please find a sample engine file for an implicit run.

Unable to find an attachment - read this blog