# Can I estimate the natural frequency of a tubular frame from static deflection?

Question asked by Lowie Van Zijl on Nov 26, 2019
Latest reply on Dec 3, 2019 by Bill McEachern

Hello everyone,

I have Solidworks Simulation standard but not the license that allows me to do modal vibration analysis.
Now I would like to estimate the natural frequency of a tubular frame with a big mass mounted on top.

So I thought If I apply a force at the location of the mass (700mm above the frame) by means of a "remote load" and I simulate the deflection of the interface at which the remote load is attached.

Then I estimate the deflection "dx" of the mass at 700mm above the interface by assuming a rigid connection between the mass and the interface.

Then I could determine some sort of stiffness "k" = F/dx

Then I calculate the frequency by considering my system as a single DOF spring-mass system with  f0= 1/2pi * (k/m)^0.5

I get a result of 23Hz which is in the order of what could be expected (customer demands 25Hz minimum) but I wonder how accurate this estimation would be?

Off course I applied the remote load in the direction which results in the biggest deflection of the frame.

Can anyone tell me whether my assumption would be correct or am I doing too much simplifications here?

Lo Wie 