Random Response Analysis (dB/octave to ((m/s^2)^2)/Hz)

Altair Forum User

Hi there,

 

As of my knowledge for doing a random response analysis we require a ASD Vs frequency curve.

 

But here I have the 'ASD slope' values (units= dB/Octave) and frequency range.

 

Can any one please tell me how to get 'ASD' values from 'ASD slope' values.

 

Is there any direct formula to convert them.?

 

I have referred the following site for that but I didn't understand.

http://femci.gsfc.na...mequations.html

 

And also Can any one tell me what is the Verification process for random vibration analysis theoretically. If not with a sample problem,,..

 

Thanks in advance

 

 

Altair Forum User

Hi,

 

First : conversion from dB/oct to g²/Hz :

 

for example, you've got a table as folowing:

From 20 to 200 Hz, level = 0.3 g²/Hz

From 200 to 300 Hz, level = -10 db/Octave

From 300 to 1000 Hz, level =0.078 g²/Hz

 

You have to calculate the folowing parameter : alpha=(-10 dB/Octacve)/(10*LOG10(2)) ; K=(0.3g²/Hz)/(200Hz^Alpha)

For F<200, level = 0.3 g²/Hz

For 200<F<300, level =K*F^Alpha

 

Second : Random Tutorial:

 

Use Altair Tutorial RD-2010 and RD-2050

Altair Forum User

Thank you