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Re : modal analysis
Posted Jul 31, 2010, 5:11 p.m. EDT 1 Reply
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Hi,
I was doing a modal analysis of structure.I gave a prescribed displacement at a node, got the first frequency.
When u give force instead of displacement , the frequency value differs.
I know that force doesnot play a role in eigen frequency analysis..
But how come prescribed displacements effect the eigen frequency evaluation???? Can anyone explain the theory or suggest a book ...
I was doing a modal analysis of structure.I gave a prescribed displacement at a node, got the first frequency.
When u give force instead of displacement , the frequency value differs.
I know that force doesnot play a role in eigen frequency analysis..
But how come prescribed displacements effect the eigen frequency evaluation???? Can anyone explain the theory or suggest a book ...
1 Reply Last Post Aug 1, 2010, 3:57 a.m. EDT
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Posted:
1 decade ago
Hi
I believe it is because if you give a prescripted displacement you "fix" your other end, so you go from a "fixed-fixed" situation (with prescribed displacement) to a "fixed -free" case (with a force instead of a fixed displacement that is ignored anyhow by default for an eigensearch). Such changes in BC's are for me sufficient to give (very) different modes and frequencies
--
Good luck
Ivar
I believe it is because if you give a prescripted displacement you "fix" your other end, so you go from a "fixed-fixed" situation (with prescribed displacement) to a "fixed -free" case (with a force instead of a fixed displacement that is ignored anyhow by default for an eigensearch). Such changes in BC's are for me sufficient to give (very) different modes and frequencies
--
Good luck
Ivar