how to remove rigid body motion of an air vehicle

[alinalin]

I have built a structural model for an air vehicle. As it contains tension-only element, nonlinear analysis need to be applied. I don't know how to constrain six degrees of freedom in order to remove rigid body motion.

There are some symmetric conditions existing, but I still can not constrain six degrees of freedom. Someone suggested the "inertial relif" function of Nastran. Even in Nastran, it sounds life that it is not working for nonlinear model. (I am not familar with Nastran). Is there any way that I can implement this concept in ANSYS?

Any input is welcome! Thanks a lot!

 

[Stringmaker]

What types of loading are applied? It's common to remove rigid body motion either with the use of friction if contact is involved. It's also acceptable many times to constrain only one node in a certain DOF. A picture or description would be helpful here. You may also want to reference similar previous work which has been done.

 

[alinalin]

Thanks for the reply.

Basically, I try to model a new type of aircraft flying in the sky. The loads are aerodynamic loads (control surface loads, distributed pressure) and aerostatic loads (weight). There is no contact involved in this model.

I don't have experience of aircraft modeling. Not sure how they pursue in the general procedure.

 

[gurmeet2003]

You could apply the 3-2-1 rule. Pick 3 nodes that are in the same plane, but are not co-linear. Constrain first node in x,y and z direction. Second in y and z. Third in z. This should constrain the rigid body in all 6 degrees, three rotations and three translations.

Gurmeet

 

[Drej]

Check the irlf command to activate inertia relief. If it's a free body then you most definitely will need this to simulate the conditions you're describing.


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[alinalin]

Gurmeet, thank you for the reply.
Where did you get this 3-2-1 rule? Is it a conventional method in constrain specification?

Drej, thank you for the reply.
Just check in ANSYS. There is an inertia relief command. I didn't know before.