Learning Forum

[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.

Thanks,

Zabee

[Chandra Sekaran]

Please take a look at ANSYS Innovation courses that introduce modal analysis at https://courses.ansys.com/index.php/courses/topics-in-modal-analysis-using-ansys-mechanical/ 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).