General Mechanical

General Mechanical

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Modal analysis

    • Cri1994

      Hi everyone, 

      I'm doing modal analysis about a simple component. the component is a bar ( 40X16X500 mm).

      I have a question for you.

      The modal analysis launched with a bar in steel(2,512Kg) gives me these modes: 51,914 Hz, 128.95 Hz, 323Hz.

      The modal analysis launched with a bar in magnesium alloy ( m=0,576Kg) gives me these modes: 52.337 Hz, 130,08 Hz, 326,43 Hz.

      I think that it is non normal. What could be the problem? The materials settings?


      Thanks a lot for your time 



    • peteroznewman

      Modal frequency is proportional to sqrt(K/M).

      K is proportional to Young's Modulus.

      Ratio of Steel to Magnesium Young's Modulus is 2e11/4.5e10 = 4.44

      Ratio of Steel to Magnesium Density is 7850/1800 = 4.361

      Expected Ratio of Modal Frequency Steel to Magnesium = sqrt(4.44/4.361) = 1.01

      This tells me that the modal frequencies being almost the same is expected.



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