Modal frequency response analysis

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

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? 

 

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Answers

  • gopal_rathore
    gopal_rathore Altair Community Member
    edited January 2018

    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
    Altair Forum User
    Altair Employee
    edited January 2018

    Hi Mayur,

     

    Can you share the model files?

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited January 2018

    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
    Altair Forum User
    Altair Employee
    edited January 2018

    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

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