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normal mode analysis in patran

normal mode analysis in patran

normal mode analysis in patran

(OP)
I am doing normal mode analysis in MSC-PATRAN using MSC- NASTRAN.my 1st elastic frequency(7th mode in free body analysis) and 1st elastic frequency(1st mode with constrained model) is not equal.
7th mode freq with free body analysis =1847hz.
1st mode freq with constrained model analysis =647 hz.
what is the error/problem.
hw to correct it.
Thanks in advance.

RE: normal mode analysis in patran

is your constrained model over constrained ? do the constraints react only the 6 rigid body motions ? have you fixed a bunch of points, or though carefully about the constraints >

Quando Omni Flunkus Moritati

RE: normal mode analysis in patran

(OP)
ok i'll check it out by removing constraints and reapplying them.thanks

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