Why does ansys repeat natural frequencies?

Hey was hunting for a solution for this. I have a fixed hanging bar 1m long and 500sqmm cross sec area. When I do a modal analysis I’m getting 1st and 2nd frequency as 18 and 3rd and 4th Frequency as 116.


any idea how I can remove the repeats?


thanks

Answers

  • visridhavisridha Posts: 76Ansys Employee

    Hi,

    Both effective mass and participation factor are parameters that help the user to get an answer for questions like:

    1. How many modes to extract?
    2. Which modes are contributing to the problem?
    3. Why do natural frequencies repeat in modal analysis?

    I will recommend you to watch the course on Modal analysis available at Modal Analysis | Ansys Innovation Courses.

    This course has all the important background information for Modal analysis.

    Vigneswaran

  • hollow4444hollow4444 Posts: 4Member

    Hey Vigneshwar,

    Would you be able to assist with a quick fix?

    Im doing this assessemnt due tomorrow evening and was wondering if i could fix it relatively quickly.


    I have taken 1) 4 Nodes and recieved the same repeats.

    2) i took 6 Nodes and still received the same repeats.


    I need to compare the First 4 Natural frequencies with Ansys and analytical method.


    Using analytical method(Roarks Formula) i get the first 4 Frequencies as :


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