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"Sonic" drilling or cutting Answered

If we look up sonic drills today we usually get some fancy machines driving pipes in the ground, preferably softer ground.
But the term includes all types of machines that use sonic vibrations to advance through a media.

With the ancient and claimed to have never existed technologies in mind I did some digging...
In the food industry vibrating knifes are quite common, same for "air knifes" on softer food.
Even in the meat industry they find more and more uses now.
Ultrasonic cutting or welding is the same thing and included in "sonic".
Same for some experimental sub sonic drilling methods currently being tested.

The general idea might be as old as using vibrating equippment to compact stuff, like concrete, bricks and so on.
What you can compact by vibration you can also make "fluid" by vibration.
Industrial feeder systems utilise this to the extreme by even making light and fine particles like flour move like water without causing any dusting.
What all the techniques have in common that a suitable tool or tool head is used and that it is attempted to use the most suitable vibration frequency for the job.
Anyone operating an ultrasonic welder knows the pain of finetuning for a new electrode or just new part to be welded.
What does that tell us now that makes the understanding easier?

Take a bottle of ketchup, preferably one that is still quite full.
Turn it upside down and noothing comes out.
Shake it a bit and you are either lucky or drowned in red.
But hold it at an angle and start tapping it and the red sauce flows out easily.
What it true for most newtonian fluids is in some way also true for non-newtonian fluids.
Ever mixed corn starch and water to make these funny experiments with it?
Hit it hard and it reacts really hard and is not sticky at all.
Leave your hand resting on it and in sinks in and sticks to it.
Stirring it very slowly is easy, go faster and you get stuck.
You can do similar things with by using an external source for vibrations.
For example a vibration speaker mounted to a smal cup of the goo.
If you place sand on a sloped piece of plastic or sheet metal then at a low angle it will pile up easy and stay.
Start vibrating the plate and the sand will start to flow off.
Works fine with a vibration source mounted to a piece of steel bar or rod and a bucket of sand too.
Trying to press it into the sand requires a lot of force, especially once you are a bit deeper.
Let it vibrate properly and it slides rights down.

If we can do the simple stuff as well as really complicated stuff in the industry then what about other materials?
So far we use vibrations to make things move out of the way, compact things, transport them or to heat them up for welding plus some cutting applications.
Considering the variety one might wonder why no one tries it for "difficult" materials.
Machined surface can be found throughout ancient history.
Finding "machined things" were vibrations was clearly used is a bit harder.
The great walls are not a perfect example here as the views differ quite a bit on how they could have been created.
But if we leave things melting them or a secret concret like recipe for creating for example granite then vibrations start to make some sense.

You find some interesting videos on youtube where people use speakers, wires and rocks to confirm you can actually "machine" them by vibrations.
Especially granite has some quite musical properties, big boulders as well as smaller ones produce destinct sounds when you hit them hard.
Tests and measurements were made on granite and other hard rocks to check how fast sound travels in them , how it is refeclted and where the sound comes out or affects the surface the most.
Lets just say every sample gave different results.
Shape, density and dimensions affect not just the resonant frequency but also where and how the sound travels in the rock.
What if??

We can use a simple speaker, a plate and some rice to see how patterns form under various frequencies.
Works with sand or other granules as well.
The interesting patterns are the so called harmoncis.
Here we see clear and destinct patters, sometimes with extremely fine lines and areas of softly vibrating granules.
Some people say these harmonic frequencies have all special meanings and uses.
We mainly used them to avoid problems.
Imagine your new TV would not have a housing tested to be stable with all frequencies the speakers can produce.
All of a sudden your back of the TV might start to rattle ;)
Same for car engines.
Harmonic vibrations are eliminated wherever possible.
Otherwise they could multiply and affect other things in the engine or around it.
Simply put it means we have various options to detect and measure vibrations on a surface or in a system.
Back in the day every half decent backup generator had a mechanical indicator for the frequency of the supplied electricity.
A set of tiny forks with the desired on painted red and several on either side of it.
These forks were designed to get into harmonic and therfor quite intense vibrations at their set frequency.
If the one for 50Hz looked blurry then all was good ;)
The same principle god be applied on a big boulder of granite.
Place the "vibration meter" at the desired spot and start moving around the vibration source on the surface until you find a spot that causes maximum response on the meter.
Best thing here is that if you then place that surface area onto another peice of fixed in place granite both pieces will start to loose substance if vibrations are applied.
The fine sediment forming is then usable as an indicator where to move the vibration source to continue once the effect literally wears off.

Is it feasable?
Well, if we trust mainstream science then the answer is no.
A huge amount of vibration energy would be required for such a hard material, despite ancient proof that says otherwise.
Semi industrial test also seemed to confirm the theory as only with very high amplitudes (loudness) and while automatically adjusting for the resonant frequency changes a measurable amount of material was removed.
I struggle a bit with that as for the testing tool heads made from hardened steel or carbide were used.
And that with little or no regards on how the head and tool itself affects the output.
I mean in terms of having the max possible movement happening right t the tool contact surface!
There is a huge difference between applying a vibration to a tool and using a system, tool and tool head DESIGNED to work at the desired frequency!
Otherwise we wouldn't need a computer to design and test a horn for welding purposes or shade a knife spefically so that the vibration go along the right axis and in the right direction.

You not break a hard thing with a very soft thing unless it travels fast enough to become harder as the target!
This complicated explanation basically just confirms that if you hit water at a too high speed then it will just break you into pieces instead of offering a soft splash
Please do not jump of bridges or such to confirm this yourself!!
If that is really true and science says it is, then how about the other way around?
Works fine too, or we wouldn't have pressure washers or water cutters.
Now for the part where I hope some really smart people leave helpful comments:

If we can cut steel with just a stream of water, then I ask:
Isn't for example copper much harder than water?
Steel is much harder than copper but water cuts through it.
The answer here it simple or complicated, depending on how you want to expain how it works.
Comes down to speed and pressure plus the right nozzle shape to prevent a beam expansion.
But then water is indeed "harder than steel".
Lets say we would use a copper pipe that in lenght, thickness, hardness and diameter is optimised to transmit a frequency so the pipe end sees the max vibration like a feed horn for ultrasonic welding.
Not to hard to calculate these days :)
Now imagine said "main frequency" would be optimised for the pipe but also be a harmonic frequency of the rock to be worked on.
The pipe end would deform quickly, abrasion does the rest and it fails before even making a decent sratch that is not copper metal on granite.
No matter how hard we press nothing good enough will ever happen.
BUT: If we would add more hormainc frequencies to feed our pipe we can multiply the amplitude quite easy!
Just try with a sound generator from your app store, needs 2 or more channels to be usable.
Pick for example 400hZ on one and 800Hz on another, then finetune around these number to hear how the tone changes ;)
My theory goes like this:
If all "working frequencies" would just harmonics of the resonant frequency of the granite, then they can be tuned so the effect on the pipe end is minimised.
The overlaying frequencies however should result in the same effect a water cutter has: The pipe becomes ultra hard.
The better the match and the more you have to get it right the harder the pipe will be.
Adding now a "drilling frequency" or multiple could be used to drive these harmonics slightly out of phase.
Like with the sound generator on your phone we end up with a pulsating sound, or vibration.
While the pipe still vibrates at the same "hardening" mix the drilling frequency creates a peak like a jackhammer.
Try it by using the heaphone output on a small speaker and placing some light and tiny things into the cone.
The will violently jump around during these pulsing tones.
For a drilling system the output can be mechanically maximised by utilising a pitchfork design.
A head holds the vibration speakers and the tynes are tuned good enough to the frequency of the speakers.
Always two would have to operate in sync though as otherwise the pitchfork movement that transfers the sound down the center bar won't work.
This head could then be desgined to act as a holder for a quick change of work out pipes that are no longer long enough for tuning.
I guesstimate that a well tuned design would result in a copper pipe being able to drill at least 10 to 15cm into solid granite before it wears off too much.
And we are talking here about just a few mm to get the thing out of tune!
But would dare to desing such a thing just to confirm a theory that no one ever really dared to test? ;)
And if friction welding works as good as ultrasonic welding, then what would happen if we try this with the right frequencies and vibrations instead of wasting tons of energy?