Missing modes phenomena

[alain10025]

Hello,

I am trying hard to find some information about the "missing modes" phenomena resulting from the use of specific preconditionning on stiffness matrices (FEM method).

Basically, I am simplifying my stiffness matrix and this leads to missing modes in the new spectrum.

Would you know any reference linked with this subject ?

Thank you.

Alain

 

[electricpete]

you might try the Mechanical Acoustics/Vibration engineering forum

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[GBor]

Or the FEA forum727