I am trying to get used to using a Data Physics analyzer at work in order to measure the natural frequency of components of a larger project I am involved in, my method described is intentionally crude as I was trying to do this as a quick play around before diving into the real thing..(adsbygoogle = window.adsbygoogle || []).push({});

To start off, I have found a aluminium circular plate component 170mm dia and 10mm thick. It has 7 small thru holes on a 160mm pcd and a 20mm circular boss at the centre of the plate, protruding 30mm on one side.

I have held the component by the central boss and hit it.

I am reading what I think is a natural frequency of 1800 Hz.

To compare, I tried to compare this to simple theory of a circular plate and found the following equation:

w_{n}=B √(Et^{3}/ρa^{4}(1-ν))

Where:

E = Youngs Mondulus

I = Area Moment of Interia

a = Diameter of the Plate

ν = Poisons Ratio

ρ = Mass Density

B = Constant based on the configuration (Clamped at edge = 11.84, Free at edge = 6.09, Clamped at center = 4.35 and Hinged at edge = 5.90)

I used some general values for the aluminium (ρ=2500kg/m^3, E = 75 GPa, ν=0.33)

I took B = 6.09

I ended up with 187.25 Hz which is way below what I was expecting.

Can anyone spot why I'm so far out or can you advise if my method is not correct?

Many Thanks

Steve

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# How to calculate natural frequency of a circular plate

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