Inertial Relief and Symmetry.

Altair Forum User

Hi,

 

Im want to run a model with  Inertial relief and a symmetry plane.  I know this is possible in Nastran.  Is it possible in Radioss?  My research says that the only boundary conditions you can have on the model are the 6 Suport1 constraints and that the symmetry plane constraints would cause a solver error.  However, since it seems that Radioss is a Nastran variant, i believe that this analysis is possible.

 

Thanks,

 

John Suyes

Analytical Methods

john.suyes@ami.aero

Altair Forum User

Hello,

I have checked the MSC/Nastran 2012 manual and here we have the same restrictions....

INREL

INREL controls the calculation of inertia relief or enforced acceleration in linear static analysis and

buckling. INREL = -1 or -2 requests that inertia relief or enforced acceleration be performed.

-1 SUPORT or SUPORT1 entries are required on one or more grid points in the Bulk Data

Section which restrain rigid body motion. The total number of degrees-of-freedom specified

on SUPORT and SUPORT1 entries must be less than or equal to six.

How does it works in MSC/Nastran ???

Regards,

Mario

Altair Forum User

Mario,

 

Thanks for the reply.  Im not exactly sure how it works in MSC-Nastran as I have never run the software.  My statement 'I know its possible in Nastran' is based on the the linked PDF which I found on the MSC website.  I tried this method in my model and was unable to get it to work.  I assumed it didnt work because the capabilities were not included in Radioss.  I suppose it could be because of an error elsewhere in the model.

 

http://web.mscsoftware.com/support/library/conf/wuc88/p03088.pdf

 

 

John.

Altair Forum User

Hi John,

 

but it seems, that they have used small RODs an very small masses on it. Then the contraints are located at 1/3 an 2/3 at the model (end of page 6).

So Inertia Relief is only supported at 6 dofs. And this is allowed and also possible at Radioss bulk.

 

Regards,

Mario