Free-Free Prestressed Modal Analysis

Ilhan Ozan Tuncoz
Ilhan Ozan Tuncoz Altair Community Member
edited October 2022 in Community Q&A

Hello,

I would like to conduct free-free prestressed modal analysis. In other words, the structure has no constraint, but is loaded. Then, this condition is analyzed in modal analysis. First I use linear statics, followed by Normal Modes by STATSUB(PRELOAD). I also tried nonlinear static solution with follower forces too.

Apparently, analyses go flawlessly until I get the results. I see that three rigid modes are missing! I've searched in internet and found out that this is a common problem, even NX Nastran mentioned about this fact in Basic Dynamics User Guide.

I was wondering, if anyone here, attacked such a problem and had a workaround?

Thank you,

Ozan

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