Modal analysis of small stones

[PratsA]

I have been doing some work on a project involving the destruction of small(less than 1/4 inch diameter), irregular stones that are obstructing small tubes.

One avenue I wanted to explore was using acoustic energy to bash them. I was thinking that some analysis of these stones would be useful to figure out what frequency or frequencies would be most effective.

When I look around at companies that say they do modal analysis they seem to either be focused on FEA analysis, or experimental analysis of large structures like automobiles.

Can anyone point me in the right direction for a company or university that would be able to do experimental analysis on these stones? Or is there some fundamental reason why you can't perform this kind of analysis on these specimens (size, shape)?

Thanks!

 

[GregLocock]

I think your investigation could profit from some research into the destruction of kidney stones using ultrasonics.

You might find that FE modelling is a better approach than a physical test.

Failing that I'd drop stones onto a large steel target and examine the acosutic signature.

Cheers

Greg Locock


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[cloa]

Is the point to break the stones or merely dislodge them?

 

[Twoballcane]

You’ve sparked my interest on this idea. Since you want to break the stones, I would think you would want to start with finding out the ultimate strength of the stones and then work your way to what frequency and amplitude would give you that ultimate stress or greater. Also, I think it would be a good idea to start with a shape that is math friendly, maybe a smooth oblong stone (if round even better). Now, if a known shape is defined, you can calc out the first mode and then see if it matches up or combine with the ultimate stress calcs. As stated in your post, these are irregular shape stones which I suspect the modes shapes will be broad band. So, instead of looking for a frequency, I think you want to look for a spectrum bounded by lower and upper ranges.

Tobalcane
"If you avoid failure, you also avoid success."
“Luck is where preparation meets opportunity”

 

[PratsA]

The object is to break the stones into small enough pieces to allow them to flow out.

The kidney stone approach is a really great comparison, but I wasn't able to find any papers that describe the effectiveness of different frequencies. I did find the following paper that seemed to be along the lines of what I'm looking for:

http://murphylibrary.uwlax.edu/digital/journals/JASA/JASA2003/pdfs/vol_114/iss_5/2648_1.pdf

Any idea of groups in the US who'd be working along the same lines?

FEA seems to be really popular, but these stones have varying compositions and densities so it would be very challenging to enter all the material properties. Experimental analysis of a selection of various stones would get me a range of frequencies (as Tobalcane said) to work with.

I've been doing compression strength testing already, and I've got a few weeks more to go to cover the range of stones. I'm lucky enough to work in R&D, where we get time to figure stuff out...

 

[GregLocock]

"FEA seems to be really popular, but these stones have varying compositions and densities so it would be very challenging to enter all the material properties."

Not really. You'd use some sort of automatic geometry and material generator to create each deck and run it.

However since you're happy to test the real thing instead then that will be more informative.

Cheers

Greg Locock


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