dynamic nastran- sine

[luisad]

Hi all
I need to perform adynamic analysis
input is acceleration vs Frequecy
such as:
100-200 hz-------9 G
200_300 Hz-------20 G
.... until arrive to 2000Hz...

sinusoidal sweep vel. 1 oct/ min

It is a normal sol 111??
I would neeed a nastran imput of this. I dont know how introduce velocity. I use g= 9810 mm/s2, thanks in advance

 

[BlasMolero]

Dear Luisa,
This is a Modal Frequency Response Dynamic Analysis (SOL111) that you can perform perfectly with FEMAP & NX Nastran.

You are confused with the term "sinusoidal sweep velocity" because the excitation you describe defines a real physical test rather than an analytical simulation.

It is very common to apply speed sweep loads in a physical test as a way of determining the maximum response to a sinusoidal input of different frequencies. A speed sweep is a transient event, but if swept very slowly the response will reach steady state at each frequency and the response should be the same as a frequency response where you dwell the excitation at each frequency increment. It however takes a long time to run a dwell test and there is risk of damaging the article – so transient sweeps are typically done and a slow to moderate sweep rate is used. In that case, the response will not reach full steady-state.

"Simply" perform a MODAL frequency response solution (SOL111), this is my preferred option, better than DIRECT frequency response solution (SOL108). In that case you would just need to set up a single acceleration loading function that would be a function of frequency.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

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