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I want to break a blade as it attempts to cut into a piece of metal.

If the metal in question was vibrating rapidly or with a significant amount of force, would the blade break in attempt to cut through the metal?

Going on, would the same concept work on bolt-cutters, effectively breaking the blade on them?

If metal will not break in this instance, but may bend, would this be an applicable concept if such a vibrating force were used on a bicycle U-Lock in order to combat bolt cutters? In essence, would it be an effective deterrent as far as bending the metal in the bolt cutter blades, rendering it useless against the U-Lock?

I'm tying to think about potential concepts that could be applied to bike locks in order to mitigate potential theft.

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    $\begingroup$ As written, this hints of an XY problem. You really need to do X but you're asking how to do Y. Please edit your question and explain the problem you're trying to solve. Then put some backing details - what type(s) of metal, thicknesses involved, degree of vibration, ... $\endgroup$ – user16 Aug 28 '15 at 15:18
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    $\begingroup$ From the way you describe the problem (e.g., vibrating "with a significant amount of force"), it doesn't sound like you have the background required to tackle this problem deductively, and we don't support open-ended brainstorming on this platform. I think you'd benefit a lot from approaching this as a hands-on learning experience; get some locks you don't mind damaging (or that are already broken), rig them up to vibrate, and see what happens. Meanwhile, this is fundamentally too broad for us to answer in a way that we can expect to be useful. $\endgroup$ – Air Aug 28 '15 at 16:52
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Unless the blade is made of a ceramic material, there is very little chance of this working.

The idea you have in mind, I think, is something like the shattering of a wine glass by exciting one of it's resonance frequencies. This works because the $Q$ of the resonance (the ratio of amplitude of the motion to excitation amplitude) is very high so that a relatively small driving force creates vibrations which are large enough to drive the glass beyond its elastic limit at which point it shatters.

This will not work with a metal for two reasons. First, metal is a relatively lossy material so that the $Q$ of its resonances are significantly lower than that of ceramics like glass (wine glass: $Q\sim10^6$, metal: $Q\sim10^3$). The second, likely more important issue, is that metals don't usually break without being pushed significantly beyond their elastic limits, they just deform.

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  • $\begingroup$ Thank you for the response! You mentioned that metal will not break in this instance, but it may bend. Would this be an applicable concept if such a vibrating force were used on a bicycle U-Lock in order to combat bolt cutters? In essence, would it be an effective deterrent as far as bending the metal in the bolt cutter blades, rendering it useless against the U-Lock? Sorry if my question is a little vague, I'm just thinking about potential concepts that could be applied to bike locks in order to mitigate potential theft. $\endgroup$ – Roberto Aug 28 '15 at 16:31
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    $\begingroup$ @Roberto No, I don't think this technique will be a useful for preventing bolt cutters from cutting through a bicycle U-lock. $\endgroup$ – Chris Mueller Aug 28 '15 at 17:15

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