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Resonance in Materials

05/10/2016 11:31 AM

How much energy can be save using resonance concept in breaking a glass? In general, is this a viable idea to use in certain application? As an example, here's a video of the Tacoma Bridge

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#1

Re: Resonance in materials

05/10/2016 11:45 AM
  • can the correct resonance be created?
  • how much energy will it take to create the resonance to do the job?
  • can the resonance be controlled?
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#10
In reply to #1

Re: Resonance in materials

05/11/2016 2:25 AM

Yes, those are likely the specific questions, i wanted to ask phoenix, thank you.

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#11
In reply to #10

Re: Resonance in materials

05/11/2016 3:00 AM

Question, more like problems that have to be addressed

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#2

Re: Resonance in materials

05/10/2016 12:36 PM

Just use a rock, or your head.

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#6
In reply to #2

Re: Resonance in materials

05/10/2016 11:10 PM
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#7
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Re: Resonance in materials

05/10/2016 11:19 PM

Reciprocity is highly unlikely.

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#3

Re: Resonance in materials

05/10/2016 12:48 PM

'How much energy can be saved', depends heavily on how it was being done before.

In general though, I'm not sure there is any inherent energy savings. Resonance allows using numerous small inputs rather than one large input. While that can be useful, there will still be losses, so in terms of energy, a resonant approach is unlikely to save energy over a single input approach.

Considering the ability to shatter using energetic materials, brisiance (related to velocity of detonation) plays an important role beyond total energy input.

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#5
In reply to #3

Re: Resonance in materials

05/10/2016 3:53 PM

Agreed, the same amount of energy is required, whether applied at once or over a period of time with resonance build up. Any savings using resonance might be due to being able to generate a small amount of energy more efficiently than a large amount.

On the other hand, counting against you is the amount of energy leakage (loss). Something with a high Q like a wine glass has low enough loss that the vibration can build up to the breaking point. Other objects with a higher energy loss, I would think, would lose enough energy over the time for resonant vibration build up to make the resonance method much less efficient.

I'm betting a hammer beats an opera singer!

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#14
In reply to #3

Re: Resonance in materials

05/12/2016 2:24 PM

Like some sort of an advantage, mechanical advantage in simpler terms. Okay.

Would that idea apply in electromagnetic wave or something?

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#15
In reply to #14

Re: Resonance in materials

05/12/2016 3:18 PM

Could you rephrase your question?

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#4

Re: Resonance in materials

05/10/2016 12:50 PM

Why are you breaking out all those windows?

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#8

Re: Resonance in Materials

05/11/2016 12:04 AM

I think the answer is going to be empirical, and you will have to be sure that other critical items are not a;so affected by the resonance.

From what I recall. both the Tacoma Narrows and Bronx Whitestone bridges were of the same design

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#9
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Re: Resonance in Materials

05/11/2016 2:22 AM

And Tacoma Narrows was not intentional.

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#12

Re: Resonance in Materials

05/11/2016 7:20 AM

I guess most things that are big enough to flex will have a natural frequency that can be matched by a regular small input force that will cause it break (or bend at least). There is something intuitive about the energy for lots of small inputs being less in total than the energy for one big input. To which have to be added the energy used by the means to generating the input. I don't know. Is it bullet versus rocket problem.

I remember the first days at work (apprentice electrician) learning it was possible to bend a length of conduit by holding it balanced in the middle and waggling it up and down. You could 'feel' the natural frequency when flexing it that could be used to increase the oscillations until suddenly the tube bent of it's own accord - which got you into trouble.

The little bit of strength to waggle the tube was nothing like the strength needed to bend it in one go. But then like the bumblebee, I did not know anything about the science of the world I lived in.

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#13
In reply to #12

Re: Resonance in Materials

05/11/2016 9:25 AM

I guess most things that are big enough to flex will have a natural frequency ...

Everything has a natural frequency, even home sapiens.

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#16
In reply to #13

Re: Resonance in Materials

05/17/2016 3:04 PM

Home sapiens??? As opposed to non-local sapiens???? Foreign sapiens??.

While systems may have an identifiable resonance, they may not all propagate without interference. For example, if you start a length of tightly strung wire vibrating freely, it will resonate, and if you introduce an interference (such as your finger) at, say, the halfway point, the resonance will continue, but vibrating in halves (at twice the frequency). However, if you put your finger at a point at which the two vibrating sections are related by a common integer, the vibrations begin to cancel out.

I believe you will find that in designing large systems, such as bridges, designers build in cancelling resonances to prevent similar failures to the examples cited in the OP.

I think there is an urban legend about a little vibration device left on a building by Tesla to demonstrate this principle, and the authorities had to come and shut it down because of the potential damage.

If you could destroy any system with applied resonance, I am certain that current musical trends would have destroyed at least half our urban centers by now! At least based on the crop of Thumpa Thumba cars I hear at stop lights!

Just an observation.

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#17
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Re: Resonance in Materials

05/17/2016 3:14 PM

that is autocorrect....

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#18
In reply to #16

Re: Resonance in Materials

05/17/2016 3:42 PM

you have to find the natural frequency or a steady repeating frequency that will build up and created a bad day.

That's why soldiers on the march break stride while crossing a bridge.

http://www.livescience.com/34608-break-stride-frequency-of-vibration.html

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#19
In reply to #18

Re: Resonance in Materials

05/17/2016 4:56 PM

It is probably one of our earliest lessons in science, even before entering infants school, when we learn how to make a swing go high by sitting on it without being pushed by others.

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#20
In reply to #16

Re: Resonance in Materials

05/18/2016 12:55 AM

"...current musical trends would have destroyed at least half our urban centers by now!"

Nah - just the eardrums.

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