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Nonlinear results as initial conditions for natural frequency analysis

Genius
Genius

I have a set of bushings which have highly nonlinear stiffness (but elastically so). I would like to use nonlinear analysis with a nonlinear force vs displacement curve to get the correct stiffness of these fasteners for use in a natural frequency analysis.

 

Aside from running a nonlinear solution and manually checking the displacement of each fastener end-point, and then entering the correct stiffness separately for each fastener, is it possible to use nonlinear results to define the stiffness matrix used in a natural frequency analysis in FEMAP?

2 REPLIES

Re: Nonlinear results as initial conditions for natural frequency analysis

Legend
Legend

Hello Kava,

 

I guess you need to run a pre stresseed modal analysis. There are some issues in internet. What I have it is not in english

Re: Nonlinear results as initial conditions for natural frequency analysis

Phenom
Phenom
You can run a pre-stiffened natural frequency analysis from a non-linear result by expanding your Non-Linear Static Analysis Set in the Analysis Manager (Model -> Analysis) and then expanding the Options, then expanding the Stiffened/Modal section, then press Edit and tick "Enable Stress Stiffening". Set up the usual natural frequency items (typically, number of modes) and that's it. It will run the NL analysis, and the natural frequency analysis.
You can probably do it as a restart (if you have ticked the analysis option to save data for re-start), but that is more complicated than the method above.