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Axt
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| Quote: | Originally posted by MephistosMinion
Hypothetically, if someone was pissed off at the cost of plasma cutting, and somone wanted to cut 25mm mild steel plate, would a linear charge similar
to the one posted on page one be adequite for the job using pressed ETN? |
The one as shown, while capable of very clean cuts only managed ~8mm. the 90° aluminium liner didnt show great penetration using NM/70%HNO3. You may
get a bit further through with ETN but I think 25mm is a stretch. possibly replace the Al angle with Cu half-pipe.
| Quote: | | Have you tested the latex bonded cone Axt? Or are you going to try again and make a better one before testing how well it works?
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No I cut that one up to see how thick the liner was. I havn't fired the nickel one I made. I've been looking into the casting resin/metal powder with
this looking like the easiest way to form a mould:
Using two funnels with spouts that allow centreing of the funnels. Ideally one would place some resin/Cu in the funnel then push the other one into it
to extrude it out the top, then clean it up. I think lubricants for molds are sold with the resin? which allows the extraction of the set liner from
the funnels. Or just break it free, these glass funnels are only a dollar a piece.
<center> <img src="http://www.sciencemadness.org/scipics/axt/funnel-liners.jpg"> <img
src="http://www.sciencemadness.org/scipics/axt/funnel-mould2.jpg"> <img src="http://www.sciencemadness.org/scipics/axt/funnel-mould.jpg">
</center>
| Quote: | Originally posted by PHILOU Zrealone
Now that this is said, imagine you make detonators based on the hollow shape principe; I would call this the hollow chamber principle...
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Oh.. but they do!
Heres a test I did ~10min ago with a couple commercial detonators, one having a concave end, the other flat. Both are #8 strength containing PETN.
They were taped end-on onto 3mm steel and fired under sand.
<center> <img src="http://www.sciencemadness.org/scipics/axt/dimple-detonator.jpg"></center>
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MephistosMinion
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Well having met a new friend who has previously held abn explosives permit and is hopefully going to renew it I think i will use shaped charges for
the steel. Is copper half pipe availiable or do I have to cut some copper pipe lengthways?
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Axt
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| Quote: | Originally posted by MephistosMinion
Is copper half pipe availiable or do I have to cut some copper pipe lengthways? |
Dont think you can buy it as half-pipe. Perhaps just use it as is, it will provide standoff, that extra mm of copper to penetrate may be negligible.
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MephistosMinion
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Well there is a section of the metal that will not be used in the press (that is what I am using the steel for) so I suppose I shall just have to do
some testing (hurray soon I can contribute something to this thread that wil be worthwhile and have pics  )
Would I be correct in assuming that the HNO3/NM mix would react with the copper in a negative way? Also I may try a glass liner if I can find glass at
a 90 degree angle.
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PHILOU Zrealone
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Axt,
Displayed the 3mm steel a characteristic hole that proves a shaped charge effect? Is it following you the purpose of the incuved end?
No doubt it has more kicking effect  !
"Oh.. but they do!
Heres a test I did ~10min ago with a couple commercial detonators, one having a concave end, the other flat. Both are #8 strength containing PETN.
They were taped end-on onto 3mm steel and fired under sand."
It would be great to test subdetonic stufs and see if under shaped form they can undergo detonation...in theory any convergent shockwave must display
such additive effect...increasing pressure and intensity...but not the speed...
For detonating stufs it seems the VOD increases after a slight speed reduction...Right?
Maybe this effect is due to a phase transfer wave passing from solid to gaseous media....? I wonder if by a mere chance such an effect also exist for
Solid to liquid phase transfer...
So what would a shaped charge do if water was present instead of a gas...?
Would a vaccuum chamber increase slightly the effectiveness of a common shaped charge?
[Edited on 20-12-2005 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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MephistosMinion
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I have drawn (or attempted to) a diagram of what I think Axt means by using copper pipe. I appologise for the text in the diagram I am unsure how to
change it.
http://img.photobucket.com/albums/v466/mephistosminion/Shape...
I will be making a small test one of theese 5 centimeters long to test on the "offcut" section of the plate.
EDIT: If I can find a cheap amine source to sensitize NM I may use that.
[Edited on 21-12-2005 by MephistosMinion]
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PHILOU Zrealone
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I think he meant that but without the lower half pipe  ...thus simply a halfcylindrical shaped charge instead of a ^ shaped charge....
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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Axt
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| Quote: | Originally posted by PHILOU Zrealone
I think he meant that but without the lower half pipe ...thus simply a halfcylindrical shaped charge instead of a ^ shaped charge....
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I originally meant that, but then suggested that the extra mm of Cu on the full pipe would be insignificant if your aiming to penetrate 25mm of steel.
Still, you could easily take that bottom off by using a grinding disk on an angle grinder. Run it up and down until it breaks through.
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Deceitful_Frank
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Sorry guys to deviate from the current discussion but concerning the start of this thread and the cylindrical lined shaped charge using the 16mm
aluminium tube...
I can source 16.5mm COPPER tubing and am looking to make a shaped charge of similar design using this tubing and 5cm diameter PVC piping.
One question, Do you think that because of the density of copper and the mass of the tubing being three times that of one of aluminium, this would be
to the detriment of performance and I would need a wider diameter PVC pipe to compensate and provide more crushing power on detonation to form the
molten jet and give good results?
[Edited on 21-12-2005 by Deceitful_Frank]
[Edited on 21-12-2005 by Deceitful_Frank]
[Edited on 21-12-2005 by Deceitful_Frank]
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chemistr1
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Cu/ epoxy cone formation
The moulding of Cu/ epoxxy is not required as it can be painted on and then built up in layers and then sanded for final finish.
75% Cu 25% resin works well but requires sanding to finish off.
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Axt
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| Quote: | Originally posted by Deceitful_Frank
One question, Do you think that because of the density of copper ....
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I dont "know" (the word "know" is very powerful!) but if you want me to guess, I'll say no, you won't need a wider diametre charge to compensate. Any
bigger and you'll end up punching through it without the help of any cavity, its quite inefficient as is. As I've said previously I dont even know the
true nature of the penetration and would be of most interest to make two identical charges and lay one flat on the target and hold one at a couple
inches of standoff. That way you can distinguish blast effects from the metal jet effects. This Polish reference may hold the answer, but I dont have
nor know how to aquire it.
E. Włodarczyk. "Effectiveness of the cylindrical hollow charge" Journal of Technical Physcs. vol. 42, no. 2 (2001)
Heres an extract thats of interest regarding the discussion of metal powder liners being compressed into cohearent solids:
<u>Explosive Compaction of powders, principle and prospects</u>
Materialwissenschaft und Werkstofftechnik
Volume 20, Issue 12, Date: Dezember 1989, Pages: 410-415
R. Prümmer
<i>"The explosive compaction method consisting of a cylindrical container surrounded by a proper type and amount of explosive is an inexpensive
method to achieve high densities close to theoretical density. The explosive's parameters have to be adjusted to the type of the powder to be
compacted. The required explosive's pressure is linearly related to the Vickers hardness of the metal powder particles. If higher pressures are
applied, an explosive liquid phase sinter - process can be achieved, allowing the welding of individual particles."</i>
And one regarding open poled hemispherical liners, I dont know is this can be related to the open poled conical liners that would result from casting
using funnels:
<u>The Behavior of Shaped Charges with open-poled hemispherical liners</u>
Propellants, Explosives, Pyrotechnics
Volume 16, Issue 3, Date: June 1991, Pages: 140-144
Richard L. Summers, William P. Walters, Richard D. Dick
<i>"An experimental study was performed in which various diameter holes were made in otherwise similar shaped-charge liners. Flash radiographs
were taken to observe changes in the liner collapse and the jet characteristics. The collapse process and jet characteristics of a hemispherical liner
are significantly altered for a hole diameter which is 10% or more of the outer liner diameter. The jet tip velocity is increased by 26% for a hole
diameter-to-liner diameter ratio of 0.25."</i>
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kABOOM!
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A small Wine bottle shape charges seem to work well when filled with PLX/Al powder. I tryed this one already! Very hot detonation!
play safe, play hard...get your lumps...pick yourself up and try again. It will only make you stronger.
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Axt
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| Quote: | Originally posted by kABOOM!
filled with PLX/Al powder. |
Aluminium powder can only act to lower detonation pressure in an explosive firing at high velocity, low velocity dets shouldn't be a problem with PLX
thus aluminium powder shouldnt be used with shaped charges. <a href="http://scipic2.ft100.net/banners/aluminized explosives.pdf">(ref)</a>
<center><img src="http://www.sciencemadness.org/scipics/axt/sc-comps.jpg"></center>
<center><a href="http://scipic2.ft100.net/banners/explosives with lined cavities.pdf">Birkhoff, G. <i>et. al.</i> "Explosives
with Lined Cavities"., J. Appl. Phys., vol. 19, p. 563-582, (1948).</a></center>
[Edited on 4-1-2006 by Axt]
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nitro-genes
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Great review! Very comprehesible... although the mathematics require some more time to think about
Like the statement that the depth of penetration is independant of the jet velocity, as long as the jet velocity is high enough to produce pressures
far above the yield strength of the target materials. 
Jet velocity is correlated directly with detonation pressure, so there should be no increase in penetration depth above a certain detonation
pressure... Which can't be true. Why should there be any need for superfast explosives with high detonation pressures then?
Another thing is the "wobbling" of the liner, what causes it? Imperfections in the liner, charge density etc? I suspect it is something like a wave,
comperable when you move the garden hose while a continuous stream of water is coming out.
Must be great to be able to access all these articles. Not everything can be simply "googled" together unfortunately...
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Chris The Great
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I've read most of that review and it is extremely food, and helped give me an understanding of chaped charges I didn't have before.
It DOES make some errors however (it is from 1948), the statement that target hardness is irrelevent has been found to be false, so jet velocity will
have an effect on jet penetration in different materials.
Obviously det pressure comes into play somewhere. However, it seems Gurney energy will actually have the largest effect on the performance, as it
will determine the liner collapse velocity and hence the jet velocity.
Extremely detailed, explanatory, and very easy to understand. Thank you Axt!
I found the section on using an inverted cone detonation wave to strike the entire liner at once interesting. It should be able to produce 50km/s+
jets, if you take the time and effort to do a perfect job of shaping the detonation shock (much easier said than done). It would be an interesting
experiment...
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nitro-genes
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| Quote: | Originally posted by Chris The Great
I found the section on using an inverted cone detonation wave to strike the entire liner at once interesting. It should be able to produce 50km/s+
jets, if you take the time and effort to do a perfect job of shaping the detonation shock (much easier said than done). It would be an interesting
experiment... |
The easiest way to achieve such a thing would be to use a thing that is called a shaped charge lens. It is in fact little more than an improved "wave
shaper disc".
In the attachment is a patent dealing with the concept. It will however most likely only apply to hemispherical, and parabolical liners... There isn't
any information given about the increase in jet velocity or penetration ability except that it is "significant".
I didn't find any evidence that it is used in a lot of shaped charges nowadays, so it might as well be of not a to great importance for overal
performance...
[Edited on 6-1-2006 by nitro-genes]
Attachment: 5565644.pdf (304kB)
This file has been downloaded 1501 times
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fallout
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Not trying to get off subject but these tests of shaped charges are being down with rdx,AP,and i think i seen a post that talk about MEK.Right now i
do not have the means to rdx.....once agian i not sure of the matierials that are need to produce RDX i do know that piric,nitric,and sulfuric acids
and some sort of acid bath process??But anyways i was wondering about using triacetonetriperoxide,and if its possible about how much would be need for
a smaller smaller scale charge?
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nitro-genes
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I seriously want to discourage you from using AP for shaped charges. The maximum achievable detonation pressure of AP is nowhere near that of pressed
PETN or RDX, meaning that even with a very strong confinement you would get very little penetration. But pressing one of the more sensitive and
notorious explosives over a sharply pointed cone raises the hairs at the back of my neck, even at a less than 10 gram scale...
Better use the MEKP you were talking about, no need to press it, less friction and impact sensitive because its a liquid...
back on topic:
While searching the patent database I found this other concept of efficiency improvement for shaped charges which seems to be to good to be true
The increase in performance from what I can understand is almost 100% (Fig-14)
The range in which the angle can deviate from the optimal angle seems to be quite tight though, so that would require some experimentation...
If only I had the time to try everything out
[Edited on 6-1-2006 by nitro-genes]
Attachment: US4109576.pdf (703kB)
This file has been downloaded 1598 times
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Axt
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| Quote: | Originally posted by nitro-genes
Why should there be any need for superfast explosives with high detonation pressures then? |
Good point, since we know det pressure correlates to shaped charge performance, in fact the "aluminized explosives" article above made use of shaped
charges to determine det pressure.
| Quote: | | Another thing is the "wobbling" of the liner, what causes it? |
Yes, I think the water hose analogy is a good one. I'm quite sure they are just refering to inconsistancies within the charge resulting in the jet
firing off at different angle along its length, this can be seen in charges that have been purpously made with irregularities. The following was fired
with an off-centre detonator.
<center><img src="http://www.sciencemadness.org/scipics/axt/offset-initiation.jpg"></a></center>
| Quote: | | However, it seems Gurney energy will actually have the largest effect on the performance, as it will determine the liner collapse velocity and hence
the jet velocity. |
There is this, combining gurney with PER theory. PER is available in FOSC but its all nuthin' but letters'n numbers to me.
<u>The Simplified Model for Predicting Shaped Charge Jet Parameters</u>
Propellants, Explosives, Pyrotechnics
Volume 20, Issue 5, Date: October 1995, Pages: 279-282
Liu Gui-Xi
Abstract
<i>The model is based on the more recent work of Hirsch and the original analytical work of Pugh, Eichelberger and Rostoker. Namely, the
simplified Gurney formula for imploding cylinders derived by Hirsch is combined with the PER theory forming one-dimensional computer code, and then it
is used for predicting the 80-mm diameter shaped charge jet parameters. Good agreement has been found with the experimental results.</i>
Fallout, <b>stop posting and start reading</b>. No person here has got the time to explain such things to someone, that knows nothing more
then how to mix acetone, peroxide and acid together and thinks RDX is made by the nitration of picric acid. Or is that a result of you very poor
grammer? Anyway arn't there better forums for you? <font size="1">(ahem... totse.com)</font>
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Lotek_
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totse is down so they are all here ^_-
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Fulmen
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| Quote: | Originally posted by nitro-genes
While searching the patent database I found this other concept of efficiency improvement for shaped charges which seems to be to good to be true
The increase in performance from what I can understand is almost 100% (Fig-14)
[Edited on 6-1-2006 by nitro-genes] |
Great Scott, this is brilliant!
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Boomer
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Just a few thoughts:
- Any reference for the 50 km/s jets Chris? I very much doubt that, *having read somewhere* 2 times VoD is max?
- I also doubt the 100% increase, remember it is a patent. But I'll read it at home before further commenting. On a side note, for improvised liners
this will help little, since jet breakup is caused by non-perfect symmetry more than by turbulent gas flow around it.
- I agree det pressure is more important than gurney. We *squeeze out* material by pressure, we dont accelerate it like a fragment. Maybe the slug is
faster (useless)?
I knew about radioactive fallout, intellectual fallout was new to me...
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Chris The Great
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The 2x det velocity is for a cylinderical cavity with a standard detonation shock wave passing over the liner over a period of time.
The theoretical 50+ km/s one has the detonation shock wave coverge on the liner and impact all points on the liner simultaneously. In this case, the
jet velocity can (in theory) increase to inifinity as the liner becomes closer to a cylinder, while the momentum decreases to zero at the same time,
and (theoretically) depends solely on the angle of the liner. So, for example, a 85 degree cone being impacted by a detonation shockwave shaped
exactly the same, would produce a jet with the velocity of about 70km/s (and very little mass).
EDIT: US Patent 6,167,811 looks interesting... I haven't had time to read it since lunch is almost over. From the abstract:
| Quote: | | In operation, a conically capped hemispherical liner is collapsed in reverse sequence. Detonation of the base of the hemisphere, done earlier in
sequence, produces a thick massive jet for initial penetration as a deep crater, in the armor. The conical liner is collapsed afterward, producing a
thin jet which reaches the armor deep into the crater earlier produced, at an increased distance than would be usual without a crater.
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[Edited on 6-1-2006 by Chris The Great]
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Joeychemist
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| Quote: | Originally posted by Boomer
Just a few thoughts:
- Any reference for the 50 km/s jets Chris? I very much doubt that, *having read somewhere* 2 times VoD is max?
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According to Melvin Cook in his book "The Science of High Explosives", the velocity of the liner NEVER reaches a full 2x the velocity of the explosive
employed in the charge.
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nitro-genes
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| Quote: | Originally posted by Boomer
I also doubt the 100% increase, remember it is a patent. But I'll read it at home before further commenting. On a side note, for improvised liners
this will help little, since jet breakup is caused by non-perfect symmetry more than by turbulent gas flow around it.
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Yes, patents are usualy fairly vague concerning precise data. But this patent seems to give some real experimentational data. The penetration was
measured in grannite however, and 4 times cone diameter in grannite seems poor performance to me...
You are right about the fact that the jet breakup is caused mainly by imperfect cone symmetry and charge density, however the improved gasflow seems
to allow the jet to form over a smaller distance, increasing the effective length of the jet by decreasing optimal standoff... (1-1,5 cone diameters
instead of 2,5) I see no reason why this should not apply for an improvised liner. Even if the breakup lenght of the jet will be the same, the
standoff can be reduced to 1 cone diameter, thus increasing the effective jet length with 1 cone diameter!
For the 50 km/s jets, even if they would exist I wonder if they would be very effective.... A very thin, low mass jet traveling at the tip at 50 km/s
would create such an enormous velocity gradient from tip to slug that very quickly the jet would disintegrate into tiny particles (jet density is very
important in correlation with penetration). So the breakup time of the jet will be very short. (Maximum strain rate that copper can handle before
diintagration is constant I think) Of course because of it's large velocity it will cover more distance in this short time. Maybe they cancel
eachother out... Question thus is if a 50 km/s jet would have a longer effective length (Edit: I think this is what they mean by saying that penetration is independant jet of velocity!)
If I understand well there should be a correlation between the detonation pressure or Gurney energy and jet lenght?!
Edit: left the fucking insert on while typing, explains the all the edits
[Edited on 7-1-2006 by nitro-genes]
[Edited on 7-1-2006 by nitro-genes]
[Edited on 7-1-2006 by nitro-genes]
[Edited on 7-1-2006 by nitro-genes]
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