Reply To: Cross-coupled stiffness elements in LS-DYNA

[Reno Genest]

Hello Simon,

I found the following in our knowledge database:

"

Superelements are not appropriate for bodies undergoing finite rotations.  
For that case, one could employ flexible rigid bodies (*part_modes)"

One developer told me: "We are working on extending it to large rotations, underway."

And here is more information from our knowledge database:

"A "flexible rigid body" saves cpu time by approximating response using mode superposition.
The basic procedure is to first compute normal modes (*control_implicit_eigenvalue) and/or
constraint or attachment modes (*control_implicit_modes) of a deformable body.
Then in a subsequent explicit analysis, you approximate that deformable body as a
"flexible rigid body" via the command *part_modes.

Here are links to papers describing the procedure and examples:
http://ftp.lstc.com/anonymous/outgoing/jday/Session_12-1.pdf
http://ftp.lstc.com/anonymous/outgoing/jday/flexrb.pdf
http://ftp.lstc.com/anonymous/outgoing/jday/Bitzenbauer.pdf
The first two are essentially the same paper.

Example input (rather old, I'm afraid) is in http://ftp.lstc.com/anonymous/outgoing/jday/flexrb_example.tar"

You will find a regular super element example here:

http://ftp.lstc.com/anonymous/outgoing/support/EXAMPLES/superel_inertia_matrix.tar


Let me know if this helps or not.


Reno.