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17-Peridot

## Dynamic analysis in FEM

I have a dubt...for the dynamic analysis the output steps/master steps understand a "real time step" or, like the static analysis, we have the load fragmentation from a min to a max?

1 ACCEPTED SOLUTION

Accepted Solutions
17-Peridot
(To:gfraulini)

It is the real units time step according to time unit (seconds for example in mm-N-S).

But this is a limited dynamic analysis only for vibration and shock in the small strain, small deformation, linear case.

3 REPLIES 3
17-Peridot
(To:gfraulini)

It is the real units time step according to time unit (seconds for example in mm-N-S).

But this is a limited dynamic analysis only for vibration and shock in the small strain, small deformation, linear case.

18-Opal
(To:gfraulini)

old infos (in german) att.

17-Peridot
(To:skunks)

This CREO type of dynamic uses "Flex-bodies" similar/ related to craig-bampton nodal method, component mode synthesis, substructuring...  They are based on linear theory using eigenmodes.  The primary reason these methods are used is to simplify complex models into numerically smaller models as compared to full nonlinear explicit dynamic analysis like from LSDyna, Radioss.

Dynamic = progresses in time, Inertia has an effect, stress waves travel through materials and build or cancel.  This can also be in frequency domain.  (time is truly time units)

Static = time irrelevant, long time, no inertia effects, slowly applied loads (this is why the "time" for static analysis in CREO is not really time units)

Here is my humble translation of a key page.  Thanks Skunks.

 Periodic Systems Transient Systems Exact (Deterministic) System Dynamic Frequency Analysis: Load is stationary, periodic and harmonic , and input as a frequency dependent function; Results produced in the frequency domain. Dynamic Time Analysis:  Stress acts in time dependent manner on the structure. Results produced for the chosen time duration, in the time domain. Stochastic (Random) System Stochastic Response Analysis: Load supplied using statistical methods as power spectral density (PSD) Dynamic impact analysis:  Load acts as a short-term vibration (“earthquake”).  The input uses a response spectrum.