Fusionfire
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Advice on getting consistent shock loads
Hello all,
I'm interested in getting a range of small but highly consistent shocks on a disc-shaped specimen at the bottom of a tank of water. The shocks would
be imparted to the specimen from the bottom up, so there would be a cavity under the disc within which the shock is initiated.
Basically I am not so interested in strength as I am in consistency + the ability to vary the shock strength. As a general rule I'm looking for a
range of shocks under 1g of a primary confined in a blasting cap.
I've come up with the following methods. Could you please comment as you see fit?
Exploding wire
- Would I find more repeatable results with small factory built tungsten filament lightbulbs (glass removed) as the exploding wire such as Christmas
tree lights, or am I better off measuring and cutting my own fine wire?
- Is the easiest way to vary the strength of the shock on the specimen to vary the distance of the exploding wire from it, or to change other
parameters (e.g. wire thickness, voltage, energy stored, etc.?) Obviously I want to say that "The impulse provided to the specimen was halved or
doubled..."
- I don't like mixing HV with water, but as I understand it others have tread this path before. I'll just have to keep one hand in my pocket 
HMTD or silver acetylide detonators
- I can probably precisely control the explosive loading, but I can't precisely control the degree of confinement. And bearing in mind there would be
dozens of tests, I am not really fond of loading lots of blasting caps.
- Also I do not know as you get to much smaller quantities whether the impulse imparted by the explosive would linearly scale down.
Burst plastic diaphragm
- Easy to make
- Pressurised from gas cylinder with a regulator valve
- Burst pressure easily varied
- Diaphragm burst initiated by a hot wire
I've read the "Exploding_Wires.pdf" in the SM Library and it was very helpful, thanks.
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watson.fawkes
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Quote: Originally posted by Fusionfire  |
- Is the easiest way to vary the strength of the shock on the specimen to vary the distance of the exploding wire from it, or to change other
parameters (e.g. wire thickness, voltage, energy stored, etc.?)
[...]
I've read the "Exploding_Wires.pdf" in the SM Library and it was very helpful, thanks. |
Energy stored is the
easiest thing to vary, and you can do that by varying the voltage that the HV supply operates at. The Cockcroft–Walton generator runs on AC, so the easiest way to change its power input is to use a variac. You won't get the best component
efficiency running at 60 Hz, but it does work, and you don't need to build a higher-frequency drive source. There are plenty of internet sources about
these.
That "Exploding Wires" pamphlet has the detail that you can explode a "wire" made only of water. It's essentially an arc discharge through liquid. It
would take higher potential to start the arc, but otherwise seems reasonable. The author doesn't mentioning adding an electrolyte the water to lower
resistivity; seems like it would have been an obvious-enough thing to include for beginners.
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Fusionfire
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Alright thanks. I'm bidding for a research grant on it and if I get it I'll post results.
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Rosco Bodine
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Lead azide is extremely precise and adjustable in its incremental output, so precise that it has been used as microcharges for a surgical instrument
for endoscopic or catheter lithotripsy to perform controlled surgically precise disruptive blasting operations on kidney stones lodged inside living
human beings. This is alternative to the electrohydraulic shock wave generation which can use a high voltage spark between two closely spaced
electrodes. The spark sourced shock wave tends to be spherical output and probably causes greater risk of damage to healthy tissue in the vicinity.
The shock wave from a miniature shaped charge can be more focused directionally so the energy transfer is more efficient to the targeted stone.
Here's a link that may be of interest regarding the physics of the electrohydraulic shock wave generation
http://www.eng.bu.edu/~robinc/pubs/ClevelandMcAteerSTEU06.pd...
[Edited on 7-2-2012 by Rosco Bodine]
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