RADIOSS IMPLICIT STOPPED DUE TO TIMESTEP LIMIT ** ISTOP=-2

Karthic_22061

Hi,

I am trying a nonlinear geometric analysis in Radioss implicit to study the buckling.

I am getting error stating

RADIOSS IMPLICIT STOPPED DUE TO TIMESTEP LIMIT **

ISTOP=-2

How can i over come this issue... Please guide me

I have tried reducing DT_min to 1e-40 in ( /IMPL/DT/STOP)

Set the IMPL/NONLIN ITol values to default ..... but these thing doesn't solve the error.

When i tried /IMPL/NONL/SMDISP to see if the issue came from geometric nonlinear. Its solved the issue but my displacement results are too low in SMDISP.

How can i solve the issue with IMPL/NONLIN..

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Altair Forum User

Hi Karthic,

When the time step is smaller than the input minimum one (see /IMPL/DT/STOP), RADIOSS will stop the run with this message.

The reason is generally due to the convergence issue (DT_min), if DT_min was already small enough or not.

There is no general workaround for convergence issue, as outlined below:

>>Check the model, constraint conditions, materials, contact interface defines and so on.

>>If the fail was due to instability, try /IMPL/DT/3 (Riks method) or /IMPL/QSTAT for general instability case.

>>Switching other convergence criteria (see Itol in /IMPL/NONLIN)

Karthic_22061

Hi George,

Thank you for the reply..

Riks method can only be used for static analysis.. If so how can i include the geometric nonlinear and at the same time solve for the buckling

Altair Forum User

Hi Karthic,

The Riks type arc-length method is suitable for nonlinear static analysis of unstable problems like buckling, snap-through.

I recommend you to go through /IMPL/DT/3 in Help Menu where this is described.

Karthic_22061

Hi George,

Thank you, i will try solving by /IMPL/DT/3 /emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />

Karthic_22061

Hi George,

I tried using /IMPL/DT/3 (Riks type arc-length method) , but my run doesn't start converging.

Please do have a look at the model attached. Help me to solve the convergence issue due to geometric nonlinear.

Unable to find an attachment - read this blog

Altair Forum User

Hi Karthic,

I doubt with the loading type used. Can you try with /IMPDISP instead of /CLOAD.

Can you try with explicit formulation, as implicit solution is RADIOSS is more to complement the explicit Solution. So we suggest to use it only for specific cases like Spring Back.