Frequency Response Analysis

misu_bhowmick

How to perform simulation (Nastran) on a system by applying a sinusoidal load of 0.1g which swept from 10-50 Hz which varies at rate of 1Hz/min ???

How to use the Time domain in solver deck?  In Modal Frequency Response i don't use varying rate (1 Hz/min) .

So please let me know how to apply the time here.....!!!

Rahul Rajan_21763

Hi,

 

You can convert data from Frquency domain to time domain using Hypergraph 2D.See attached pdf.

Since most of the card are similar in Nastran  & Optistruct.We recommend you to use Optistruct sover to carryout Transient & Frequency response Analysis.

Refer Optistruct Advanced linear dynamics analysis tutorials.See attached screenshot.

 

Regards

Rahul R

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misu_bhowmick

Hi Rahul thanks for reply....but the thing is like i am able to give excitation over a certain frequency range with a const. damping in Modal frequency response & plot  it... Additionally i need to apply the rate 1Hz/min.....

i guess some time step  or time domain card is needed which i am unable to input.....may be i need to refer Transient Dynamic analysis.......i have no issue with optistruct also...but Nastran will be better for me.

Altair Forum User

Hi,

 

From my understanding, you want to delay the load application, is that right?

 

Can you check DELAY in RLOAD1 card which delays (shifts) the load application by a particular time?

 

If you are commercial customer, please contact your local support.you can contact your local support @ http://www.altairhyp...ortProduct.aspx

misu_bhowmick

Altair Forum User said:

Hi,

 

From my understanding, you want to delay the load application, is that right?

 

Can you check DELAY in RLOAD1 card which delays (shifts) the load application by a particular time?

 

If you are commercial customer, please contact your local support.you can contact your local support @ http://www.altairhyp...ortProduct.aspx

 

I am trying to use DELAY CARD but i am unable to use that specific 1hz/min rate..... even if i create load collector , how to use proper card for constraints or some other functionary card is there for representing time???

Altair Forum User

Hi,

So you have a 0.1G load applied at a frequency of interest of 10-50Hz and this should be spread at 1HZ/min, ryt?

Can you check the FREQ4 card if the above is what you are expecting?

TIme units depends on your unit consistency. 

misu_bhowmick

 

Hi, Prakash,

Thanks for reply.

But FREQ4 card only takes care of frequency spread over the centre frequency of computation. I want to control the rate of sine sweep in the time domain, hence the rate 1Hz/min or 1Hz/sec is important for my analysis which I am not able to do in frequency response analysis. 

Need your suggestions...