is it possible to represent a flexible body by a multiple of rigide bodies (>10 bodies), this rigide bodies are attached between them by springs and dumpers so they can behave exacly like the flexible body once they are excited at the eigen frequencies of the flexible body. i know some will say try to mesh it, but i don't have a good FEA soft, so i'm trying to represente the meshed body in a non Finite element software.
thanks
Eigen frequencies and modes are dependent on the stiffness and mass interaction between nodes. As you know, for a given mesh and no. of eigenvalues requested during extraction, you've only certain no of eigenvalues accurate (this is due to eigensolving technique).
Mass distribution is easy, as many codes utilize lumped mass system.
Stiffness distribution will be tricky as depending upon type of elements, each node will have certain no of stiffness components. So theoretically it's possible to retain in rigid body system with springs, but practically it'll be quite difficult. Just look at stiffness matrix of a simple spring. Each node interacts with the other node (off diagonal terms in stiffness matrix). Similarly in a beam element, each dof will interact with other dof of the same node + the node at the other end. Simple springs generate uncoupled stiffness matrix. If you know a way to account of inter dof interaction, then yes you can do what you want, otherwise no :)
Hi
Multi Body Simulation (MBS) software uses Craig Bampton modes to represent flexible bodies., Take a look here
https://vibrationdata.wordpress.com/2013/04/30/craig-bampton-method/
If you are looking for a free MBS, take a look here
https://www.mbdyn.org/
Sincerely
Claes
Dear Tarif,
Your idea is basically same as FEA. That means your idea surely works. Though it is not new idea, it is quite creative that you solely came up with this idea.
There is an opposite example. A system consisting with huge number of bodies is represented by a elastic body as an approximation. You know what's? It is the bodies are atoms, and the eigen modes are known as "phonon".
thank you all for your precious informations, from the reponse of Abhimanyu Kumar, i think that this method will be a thesis for PHD if we can factorize and diagonilize mass and stiffness matrix and reduce the DOF of a FEM model, thank you Claes Richard Fredö as always you have some informations about FEA softwares that no one is aware of, and Yoshiki Fukada.
Dear Tarif,
the rigid segment method is widely used, as a method which is familiar with FEM.
For more information, see my papers on the following link:
http://journals.sagepub.com/doi/full/10.1177/1077546315575818
http://link.springer.com/article/10.1007/s00419-017-1243-z
Best regards,
Aleksandar Nikolic
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