Frequency range of interesting in a modal testing

Experimenter
Experimenter

Hi everyone!

I have a problem that i don't understand. Could you help me?

When you do a modal testing for any struture, bridge structures, for example. So, You don't know which mode shapes the structures will vibrate according to. How many relatetive frequencies are.

"For example, you use a impact hammer, each tip will create a different frequency range. So, first of all, you must decide frequency range of interesting. And then, depend on how many frequency range of interesting are, you will choise a proper tip. I think so"

So, how can you choise frequency range of interesting? What does it depend on?

 

Thanks you so much!

2 REPLIES 2

Re: Frequency range of interesting in a modal testing

Creator
Creator

Hi Dung,

 

I think it the frequency range of interest depends on the engineering problem you are trying to solve by doing the modal analysis.

 

For example, if the object has high levels of vibration, and you do a measurement and the vibration levels are high from 0 to 2000 Hz, then the frequency range of interest would be upto 2000 Hz.

 

If you are working on improving the sound of the object, and it is making a squeal tone at 5000 Hz, then the frequency range of interested would be at least upto 5000 Hz (maybe take a little extra to 5500 Hz).

 

Once you know the problem frequency or issue you are solving, then you know what frequency range to perform the modal testing over.

 

Typically you might not care about resonant frequencies that are not excited during the operation of the product.

Re: Frequency range of interesting in a modal testing

Experimenter
Experimenter

First of all. thank you for you reply.

And, i agree with you about you reply.

But, So, what frequency range of engineer problem that you want to solve depend on?