General Mechanical

General Mechanical

How to change the excitation frequency and plot graph of the amplitude vs rpm?

    • TechVid
      Subscriber

      Hi,

      The system is a shaft supported by two bearings at both the ends. The shaft has two discs mounted over it. The aim of analysis is to find the behavior of shaft before and after developing crack. After crack is generated in the shaft the graph of amplitude is supposed to show a resonating peak, which varies by changing excitation frequency controlled by unbalanced mass. But there's no change in the graph even after changing the unbalance mass. Any clue why's this happening? It is evident from all other research papers that the graph of peak varies with unbalanced mass.

    • 1shan
      Ansys Employee
      Please share images of your mesh and model setup. Have you set rotodynamic controls, coriolis effect to yes? I hope you have used a fine enough mesh to resolve the crack details. It would also help if you perform a modal analysis first and check if the crack has any influence on natural frequencies. Also, check this useful tutorial
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      Regards Ishan.
  • TechVid
    Subscriber
    Hi Ishan thankyou for joining here Yes, there's rotodynamic control turned on, coriolis effect as well.
    Yes the mesh is good enough and fine enough near cracks. The natural frequencies from modal analysis matches with the one performed in MATLAB.
    I'll share the images soon. ( Those are unpublished classified images, so I wanna remove em latter)
    The first graph is correct, I'm trying to get the results when excitation is doubled by increasing
    At 2x of harmonic speed and 3x of harmonic speed.
    I tried to change the ratio ╬® = 2¤Çf / RATIO via command.
    Am I missing something here?

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