Modal frequency response analysis

Altair Forum User

Hi sir,

I have done modal and modal frequency response analysis of a motor. I am getting natural frequencies as mentioned:

1)  1509.74 Hz

2)  2391.88 Hz

3)  3138. 35 Hz and so on

In the modal frequency response analysis, I am getting peak values of acceleration at 500Hz, 1500Hz, 2500Hz. 

Last 2 peaks I can understand as it is near the 1st and 2nd natural frequencies. But how did I get a peak at 500Hz?

And what does it signify? 

 

gopal_rathore

Hi,

Is the modal analysis done was a free-free run or a constraint boundary condition was also used. It is recommended to first do a free-free run to check the integrity of the component or the system.

Also have same boundary condition for modal analysis as being used for the frequency response analysis.

Altair Forum User

Hi Mayur,

 

Can you share the model files?

Altair Forum User

Also, check if there are any local modes. I would suggest you to run a free free analysis if there are rigid modes.

 

Is the frequency of loading is in par with frequency?

Altair Forum User

Sir I will send you the model files as soon as possible. 

I want to know is the frequency response amplitude (peak)  depend  upon magnitude of forces along with the vibration modes? 

Because after seeing the distribution of forces, I came to know that forces at 500Hz are higher than at any other frequency , but we did not get any natural frequency there. So maybe I thought that frequency response output may also depend on forces. 

 

Please clarify, 

Thank you