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Sine on Random Vibration Simulation

Creator
Creator

Hello,

 

I am able to do Random vibration and Sine vibration by using Sol103 response simulation, 

 

I would like to do sine on random (combined sine and random).

 

Example:

Random spec

20Hz, 0.01 g2/Hz

100Hz, 0.01 g2/Hz

2000Hz, 0.001g2/Hz

 

Sine spec,

at 20Hz 1.5G,

at 100Hz, 2G.

 

I am thinking that I need to add these sine spikes to random graph, that means giving spikes at a perticular frequency.

 

if at all it is correct, what will be the slop of the sine spike?

 

Pls suggest.

 

6 REPLIES

Re: Sine on Random Vibration Simulation

Legend
Legend

A practical approach to do sine on random is to come up with equivalent PSD for your sine tones, and then perform a random vibe analysis (SOL111) for the combined PSD.

 

Another approach is to convert everything to transient, do the combination there and solve for transient.

Re: Sine on Random Vibration Simulation

Phenom
Phenom

check for example: http://www.ata-e.com/uploads/2007_4.pdf

 

Production: NX9.0.3.4, NX10.0.2.6
Development: VB.NET (amateur level !)

Re: Sine on Random Vibration Simulation

Legend
Legend

This is one method, yes.  We actually prefer not to go the transient route for several resaons (including the non-uniqueness of the PSD to transient conversion).  We prefer staying in the frequency domain, and convert the sine to PSD bands...  Then comes the question of how to calculate the band, there are also several methods for that...

Re: Sine on Random Vibration Simulation

Phenom
Phenom

Quite right. Was just an (google-ed!) pointer. What is your prefered way of calculating "the band" then?

Production: NX9.0.3.4, NX10.0.2.6
Development: VB.NET (amateur level !)

Re: Sine on Random Vibration Simulation

Legend
Legend

We use half-power band to do our calcs...

Re: Sine on Random Vibration Simulation

Creator
Creator
Thanks for your reply, but my problem is not resolved, 
 
Please help out me in the below given problem.
I would like to convert the narrow band sine tones to PSD curves and super impose them on the broadband signal.
 
Example:
 
Broadband (random vibration)
10 Hz      0.002 g^2/Hz
100 Hz     0.02 g^2/Hz
300 Hz     0.02 g^2/Hz
500 Hz     0.002 g^2/Hz

Narrow Band (sine tones)
4.86 Hz    0.12 g
19.44 Hz   1.94 g
38.88 Hz   2.5 g
58.32 Hz   2.5 g
 
Inline image 1
How to convert sine tones ie., 2.5 g at 58.32 Hz to the broadband, what will be the dwell frequency and slope of the tone.
 
Regards,
Rajendra.