General Mechanical

General Mechanical

Natural Frequency of a fixed-fixed Beam

    • Zabeeullah

      How do we calculate the natural frequency at different modes for a fixed-fixed beam with the given data.

      Lenght = 2 m

      Cross section = 70*30*4 mm

      Moment of Inertia Ixx =420565 mm^4

      Distance between neutral surface to top-most surface (y) = 35mm

      Modulus of Elasticity= 210 GPa

      Density= 7405 kg/m^3

      Mass per meter= 5.45 kg/m

      Apart from this, A point load of 1000N acts on the beam at the centre. Does this load affects the natural frequencies and the modes of the system? Do i need to consider this load while calulating the natural frequency and mode shapes of the beam?

      Your help would be appreciated.



    • Chandra Sekaran
      Ansys Employee
      Please take a look at ANSYS Innovation courses that introduce modal analysis at for how to run a modal analysis.
      A load like you describe generally does not have significant effect on the natural frequencies/mode shapes. However lesson 2 in the above course talks about pre-stressed modal analysis where loads could make a significant impact on the natural frequencies (like a tensioned guitar string or a turbine blade rotating at high speed).
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