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ERROR in Rigid Body Unstable

Altair Forum User

Hi All,

Any of you did face this issue before?

Initialize the model got no error, then while running , it stop in ERROR TERMINATION with the below message.

MESSAGE ID : 110
** ERROR : RIGID BODY ID=121767 UNSTABLE
ERROR TERMINATION

Normally what kind of situation will cause this error? my RB created when I use bolt connection. so i suppose it should not be the RB problem but should be other problem.

Thanks.

Kin Poh

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Altair Forum User

Hi Kin Poh,

The rigid body turns more than one radian per cycle. This situation is due to divergence in the computation.

Please select this rigid body from RBODY MANAGER in HyperMesh and make Ispher to 1.

Let us know whether it helps.

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Altair Forum User

Hi George,

Thanks.

It works now.

but it appear other error that i need to troubleshoot on it.

Besides, do you have any documentation about ERRORs occurred and solving methods for RADIOSS?

Thanks.

Regards,

Kin Poh

Altair Forum User

Hi Kin Poh,

If you can send the out files we can help you in sorting the errors. Always run the model checker (Tools>>ModelChecker>>RADIOSSblock) so that HyperMesh will list out the possible modelling errors.

You can check the Frequently Asked Questions in our Help Menu where we have some common errors in RADIOSS.

Else you can download our RADIOSS ebook where we have documented common errors (including FAQ's from Help) topic wise.

You can download the ebook from Introduction to Explicit Analysis using RADIOSS

Altair Forum User

Thanks a lot George!

you are very helpful.

Appreciated.

Regards,

Kin Poh

Altair Forum User

Hi George,

I got another ERROR here.

MESSAGE ID : 259

** WARNING ZERO OR NEGATIVE VOLUME : 3D-ELEMENT ID : 144050

ELEMENT IS SWITCHED TO SMALL STRAIN OPTION

**ERROR : NEGATIVE STIFFNESS NODE 245882
**ERROR : NEGATIVE STIFFNESS NODE 12274

from the ebook, it did not really mention how to solve it, it only saying ERROR causing by:

'' In case the Interface Type 2 with Spotflag =0, this can cause an error in RADIOSS Engine at
the first cycle, due to a negative mass or inertia of a master node of the segment. This can also
cause an error in RADIOSS Engine during the run due to a negative stiffness on a master node
of the segment''

Any idea on how to solve it?

Thanks.

Regards,

Kin Poh

Altair Forum User

Hi Kin Poh,

The negative volume issue happens when the solid elements are very deformed and their characteristic length goes to 0. For large strain formulation the time step of an element goes to 0 when the element is compressed. Those elements will be automatically switched to small strain.

Regarding negative stiffness node this error could be of different reasons.

Is these nodes involved in a TYPE2 interface?. If so, please remove these nodes from the slave side of your TYPE2 interface. Else, you can try with Spotflag =1 also for the interface.

A_20330

Hello, I'm having the same issue, about the unstable rigid body, is there is another way to fix this problem ?

MESSAGE ID : 110
** ERROR : RIGID BODY ID=31 UNSTABLE
ERROR TERMINATION

Guilherme_

Hello, I'm having the same issue, about the unstable rigid body, is there is another way to fix this problem ?

MESSAGE ID : 110
** ERROR : RIGID BODY ID=31 UNSTABLE
ERROR TERMINATION

Hello,

I would suggest you run the model checker and see if there are any warnings related to RBODY. Usually, this warning is related to the Rigid Body inertia definition.

For small rigid bodies (4 to 8 secondary nodes), the inertia is often very small in one direction and very large in one specific direction. This may lead to instability; therefore, through the use of spherical inertia (Ispher=1), inertia will be identical for any direction.

Please check if you have such kind of Rigid Bodies and their Ispher flag.

Regards,

Guilherme Brandão.

A_20330

Hello,

I would suggest you run the model checker and see if there are any warnings related to RBODY. Usually, this warning is related to the Rigid Body inertia definition.

For small rigid bodies (4 to 8 secondary nodes), the inertia is often very small in one direction and very large in one specific direction. This may lead to instability; therefore, through the use of spherical inertia (Ispher=1), inertia will be identical for any direction.

Please check if you have such kind of Rigid Bodies and their Ispher flag.

Regards,

Guilherme Brandão.

Hello,

Thank you for your reply, i have tried that for all the RB that are having the problem, but it's not working, at the same time each run the files stop and the same error happens, is there any other way?

Guilherme_

Hello,

Thank you for your reply, i have tried that for all the RB that are having the problem, but it's not working, at the same time each run the files stop and the same error happens, is there any other way?

Hi,

Are you able to share your input deck? If you can, I can review it on my end and provide you with better information.