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Author: Subject: Unconventional Shaped Charges
nux vomica
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[*] posted on 12-9-2015 at 05:02


Quote: Originally posted by dangerous amateur  

Quote:

through 7 meters rg6 coax.


How do you do these tests, did you bury the setup?

7m is extremely short, must be pretty load. How about shrapnel protection?


No burying theres a sacrificial end on the rg6 which gets destroyed, I am behind a dirt pile and the caseings all plastic plus im already going deaf:D
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[*] posted on 12-9-2015 at 17:33


That is a very nice result, 3.6D in penetration!



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[*] posted on 12-9-2015 at 17:50


Quote: Originally posted by Hennig Brand  
That is a very nice result, 3.6D in penetration!


Thanks hennig .
Am I right in saying that I should be able to get 7+ cone diameters of penetration (120mm) if everything was perfect with my shaped charge ?
Nuxy




[Edited on 13-9-2015 by nux vomica]
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[*] posted on 12-9-2015 at 18:47


I found a graph in pdf on shaped charge calculation models that may be able to help answer your question. It graphs non-precision charge vs a precision made charge and then ideal jet performance at the top which would be very hard to explain.
For a non-precision charge it peaks at about 4.5 CD at about 2.5 CD so it seems your standoff was perfect.
Only question is what constitutes a precision made charge because most of the charges on SM are quite precision designed already so where is the line?
I don't know if you could make 7 CD penetration as that is quite high on the table but I couldn't answer until I found out what has to be done to go from a non-precision charge to a precision one according to the graph
So I've kind of given a question for a question:)

[Edited on 13-9-2015 by greenlight]

20150913_103549.jpg - 8MB

[Edited on 13-9-2015 by greenlight]




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[*] posted on 12-9-2015 at 19:06


That 7x cd penetration was a bit pie in the sky greenlight 4.5 sounds more reasonable to me now, I might bump the charge up to 15 grams and see what difference that makes.

Precision vs. non precision bit of a hard one that maybe there talking about improvised charges vs. military manufactured charges.

thanks Greenlight. nux
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[*] posted on 13-9-2015 at 01:00


Yes, I think they are talking about military manufactured charges when they say precision.
If enough time is put into putting the charge together and crafting the liner using special equipment, you could come up with something meeting the "precision" requirements at home surely.
Nux, your liners are perfectly symmetrical and spun on a lathe (proper equipment) if I am correct, they should be above the scale of a non-precision liner. Maybe more penetration is possible
I wonder if they are made in somewhat the same way in a factory that are designing liners for military use?

I agree with NP, I think you could enhance the penetration depth by using a more powerful explosive.
I attached a picture from a page comparing HMX and the new explosive CL-20 in shaped charges and co-crystallization of the two.




cl-20-high-power-military-explosive-2@2x.jpg - 48kB

CL-20 is on the left and HMX on the right.
It does not state how thick the steel plates are but that is quite a lot of penetration especially considering that the page says that both charges only had 30 grams of explosive in them!

This also shows that more powerful explosive does help with penetration in CSC's (9100m/s for HMX and 9660m/s for CL-20). The extra 550 m/s gives a increase of 40% penetration power assuming that the charges had the same confining geometry/liner dimensions.
Differences in heat of explosion, brisance, etc between the two explosives could also increase/decrease penetration I am guessing.


[Edited on 13-9-2015 by greenlight]



[Edited on 13-9-2015 by greenlight]




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[*] posted on 13-9-2015 at 09:59


Nice work Nux! But you sure are making me miss the days when I made shaped charges. Lol!

Based on the graph Greenlight posted... since your cones are very symmetrical, I think you could increase penetration if you increased your standoff. By increasing standoff you'll stretch the jet and reduce its diameter which should result in deeper penetration.
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[*] posted on 13-9-2015 at 11:07


Quote: Originally posted by nux vomica  
Precision vs. non precision bit of a hard one


The Precision Linear Shaped Charge (PLSC) design concept basically involves the independent fabrication and assembly of the liner/wedge, the tamper/confinement, and explosive. The liner is the most important part of a linear shaped charge (LSC) and should be fabricated by a more quality controlled, precise process than the tamper material. Also, this concept allows the liner material to be different from the tamper material. The explosive can be loaded between the liner and tamper as the last step in the assembly process rather than the first step as in conventional LSC designs. PLSC designs have been shown to produce increased jet penetrations in given targets, more reproducible jet penetration, and more efficient explosive cross-section geometries using a minimum amount of explosive.

PLSC are mainly used in rocket stage separation, parachute system release, flight termination, severance of thick metallic barriers and system flight abort or disablement. Most of the LSC components for these systems require precise and reproducible jet penetration using the minimum explosive and component weights.

Some of the disadvantages of conventional LSC designs are as follows: Non-symmetrical cross-section geometries, Nonuniform explosive density (neither within a plane at a given distance or along the length), Non-optimized explosive and sheath cross-section geometries, Non-reproducible jet penetrations in target materials, etc...

Quote: Originally posted by greenlight  
I agree with NP, I think you could enhance the penetration depth by using a more powerful explosive.


This is true to an extent but not the only variable... I would also suggest adding more tamping.... The explosive charge to liner mass ratio can be designed to optimize the transfer of energy from the detonation wave through the liner to the high-velocity jet and the explosive charge to tamper mass ratio can be designed to optimize the tamper material and thickness too.
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[*] posted on 13-9-2015 at 11:47


@Greenlight,
The plates must be 3cm because 30g shaped charge CL-20 is able to pierce through 21 cm iron steel armor (7*3 cm = 21 cm) ;)

[Edited on 13-9-2015 by PHILOU Zrealone]




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[*] posted on 13-9-2015 at 14:53


Quote: Originally posted by gnitseretni  
Nice work Nux! But you sure are making me miss the days when I made shaped charges. Lol!

Based on the graph Greenlight posted... since your cones are very symmetrical, I think you could increase penetration if you increased your standoff. By increasing standoff you'll stretch the jet and reduce its diameter which should result in deeper penetration.


Thanks gnitseretn, its a pity you cant still dabble in them :(
I am thinking of making the top cone radius larger as I can just get a 1.5 mm rod through the bottom of the hole and think that might enlarge the hole dia.
With a larger diameter jet and more standoff hopefully I can get some more penertration out of my setup.
Nuxy



[Edited on 13-9-2015 by nux vomica]
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[*] posted on 14-9-2015 at 00:38


Quote: Originally posted by greenlight  
I went through the document optimized conical shaped charges and photographed a couple of tables that may have answers to some of the problems that have been arising with the CSC's. The document studys cone angle/diameter, standoff, explosive height/width, liner material/thickness, and explosive type and tamper.

The first table is different cone angle's and standoff's and their effects.
The second is jet penetration effects from varying explosive height.
The third is a diagram of the final results from all test's incorporated into making a perfect conical shaped charge.

[Edited on 23-8-2015 by greenlight]



[Edited on 23-8-2015 by greenlight]



It seems I was wrong and Ecos was right and the optimum cone angle is 45 degrees with 60 degrees still being effective but any more angle and the penetration starts to drop off.

So the optimum CSC configuration seems to be:

Cone apex angle 45 Degrees
Liner thickness 0.01 CD (1% cone diameter)
Explosive height 1.5 -2 CD
Explosive width 1-1.4 D
Optimum standoff 2-6 CD

[Edited on 23-8-2015 by greenlight]

[Edited on 23-8-2015 by greenlight]


according to the tables and the graph of greenlight , the stand-off distance should be around 6 CD.
the angle should be also a good factor. I think the above experiments used 60 degree cones. if it was 45 degree you can reach 1 CD increase in penetration.

VoD of the EM is an important factor but CL-20 is not easy to be synthesized.
most of the successful setups on internet used (PETN+NG) or plastic ETN.
I found (PETN+NG) gave much better penetration.
Good luck

[Edited on 14-9-2015 by ecos]
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[*] posted on 14-9-2015 at 00:53


The graph says that the optimum standoff for a non precision charge peaks at about 2-3 CD.
For a precision charge, optimum standoff appears to be between 4 and 6 CD like ecos said, maybe even up to 8 CD

The only question is because Nux uses proper equipment to form his liners, where does his charge fit on the graph? Precision or non- prescision?

Its probably down to guess work but we will know what category his are in by the penetration of his next CSC test.


[Edited on 14-9-2015 by greenlight]




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[*] posted on 14-9-2015 at 03:30


Quote: Originally posted by greenlight  
The graph says that the optimum standoff for a non precision charge peaks at about 2-3 CD.
For a precision charge, optimum standoff appears to be between 4 and 6 CD like ecos said, maybe even up to 8 CD

The only question is because Nux uses proper equipment to form his liners, where does his charge fit on the graph? Precision or non- prescision?

Its probably down to guess work but we will know what category his are in by the penetration of his next CSC test.



Dont put any pressure on me will you greenlight. Hahaha ;)



[Edited on 14-9-2015 by nux vomica]
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[*] posted on 14-9-2015 at 04:24


Quote: Originally posted by nux vomica  
Quote: Originally posted by gnitseretni  
Nice work Nux! But you sure are making me miss the days when I made shaped charges. Lol!

Based on the graph Greenlight posted... since your cones are very symmetrical, I think you could increase penetration if you increased your standoff. By increasing standoff you'll stretch the jet and reduce its diameter which should result in deeper penetration.


Thanks gnitseretn, its a pity you cant still dabble in them :(
I am thinking of making the top cone radius larger as I can just get a 1.5 mm rod through the bottom of the hole and think that might enlarge the hole dia.
With a larger diameter jet and more standoff hopefully I can get some more penertration out of my setup.
Nuxy



[Edited on 13-9-2015 by nux vomica]


The only way to increase the diameter of the hole while keeping penetration the same is by increasing the whole charge. Liner, amount of explosive, everything. You don't wanna do that. You can get a slightly bigger hole by decreasing liner angle but you'll sacrifice penetration, which you also don't wanna do.

The size of the hole is fine. Focus on penetration not the size of the hole.
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[*] posted on 14-9-2015 at 04:57


No pressure Nux :)

Like knitseretni said, keep charge specs the same and see how much penetration can be obtained from it.




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[*] posted on 16-9-2015 at 04:35


Had a break from trying to catch the EFP slug and decided to try a small scale EFP for a change.

This time diameter of charge was only 18 mm and explosive height was 1.5x liner diameter.
Liner was 1.79g in weight, 0.9mm thick and had a depth of curvature of 3mm.
Charge weight was 9 grams 79/5/16 PETN/RDX/plasticizer/binder.
Target was 6mm steel and standoff was 35 cm.

Result is a nice through and through with a hole diameter of 11mm. I think that it could go through 10 mm which I will eventually attempt as well.



[Edited on 16-9-2015 by greenlight]

20150826_155422.jpg - 4MB 20150916_171414.jpg - 4.4MB 20150916_172634.jpg - 5.4MB




20150916_172641.jpg - 5.1MB

[Edited on 16-9-2015 by greenlight]




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[*] posted on 16-9-2015 at 05:11


More pictures with scale.

[Edited on 16-9-2015 by greenlight]

20150916_210056.jpg - 2.9MB20150916_205958.jpg - 4.7MB




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[*] posted on 16-9-2015 at 05:46


This began as an experiment on improvised reinforced blasting cap design.

Capsule is made of a 6mm bullet jacket on primary end, pressed inside of a 7mm jacket on output end. Epoxy is applied to exterior of 6mm tube, and a miniature tubeing cutter is used to swage a locking groove on overlapped area after assembly-

Primary is 350mg of 80:20 Mercury fulminate:Potassium chlorate. A commercial electric match embedded in epoxy putty is used to fire the device.

Base charge is 500mg well pressed & plasticized PETN under 500mg of hand pressed pure PETN.

After a couple of contact tests on steel plates, a couple more shots were tried with 3 and 5 X OD stand offs. The holes in 10mm steel target are at least 5mm deep- There is still some of the "carrot" down in the hole I could not remove, will section plate and measure full depth later. The output end seems to behave more as an EFP than a SC- Wide angle of the cavity liner was a fortuitous accident, not my original design intent! Output end profile of 7mm Copper capsule is spun into it with a 120 degree center punch chucked into a drill press, inspired by Copper smithing disclosed here by Laboratory of Liptakov-

image.jpg - 913kB image.jpg - 1.9MB image.jpg - 1.8MB image.jpg - 777kB image.jpg - 1.1MB

image.jpg - 2.9MB image.jpg - 2.1MB image.jpg - 2.1MB

[Edited on 16-9-2015 by Bert]




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[*] posted on 16-9-2015 at 13:43


Nice result greenlight looks good.

Bert are you drawing the jackets or are they commercial, nice result as well though .

[Edited on 16-9-2015 by nux vomica]
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[*] posted on 16-9-2015 at 18:22


I was wondering if anybody knows why the inside of the holes made by a CSC appear to be lined gold? Is there some kind of alloying of copper with the steel targets? You note this effect on many of the penetration pics here and I'm curious to know if anybody knows



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[*] posted on 16-9-2015 at 19:20


I think it is something to do with when you get new copper pipe it has a nice colour which fades from oxidization in air.
Also, when you cut copper the new cut face is always much brighter in colour.
I think the colour is from the new surface of copper that has been coated on the hole during penetration which oxidizes back to the dull colour after exposure to air. I think the high temperature and stress energy applied to the copper may contribute to the more golden appearance.

I have noticed the nice gold colour fades to dull brown/orange after a couple of days which supports this.




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[*] posted on 16-9-2015 at 20:35


Right, copper is attacked by O2 and CO2 and atmospheric moisture.

2 Cu (s) + O2+ H2O (g) + CO2 = Cu(OH)2 + CuCO3 (s)

This is not a one step process. The copper first oxidizes forming cupric oxide (copper I oxide) . The water and carbon dioxide form carbonic acid (H2CO3), then the copper I oxide and carbonic acid react forming copper hydroxide and copper carbonate.

The jet from a shaped charge moves at different speeds and that’s why it will stretch. As it stretches it will break up into particles. Also, at the apex of the cone, which forms the very front of the jet, does not have time to be fully accelerated before it forms its part of the jet. This results in its small part of jet being projected at a lower velocity than jet formed later behind it. As a result, the initial parts of the jet coalesce to form a pronounced wider tip portion. As the jet forces through a target, the high pressure and fluid-like behavior of the jet along with the stretching and break-up of the jet causes the copper to “coat” the inside of target and expose the clean copper that I too really wish was gold. ;)




[Edited on 17-9-2015 by Joeychemist]
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[*] posted on 17-9-2015 at 05:57


Quote: Originally posted by nux vomica  

Bert are you drawing the jackets or are they commercial


The 6mm jackets are as provided by Corbin. Only modification is to drill bottom 7/64" and de burr hole for Ematch wire exit point.

The 7mm jackets started out life as .308 x 1.25" long "versatile bench rest" jackets. They have been run through a swage down die intended to make .284 bullet jackets , are now about 1.4" long. A friend who makes his own jacketed bullets via swaging did this step for me, I'll ask for pictures of the equipment involved.

I will post additional pictures of the conversion process when I have time-




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[*] posted on 17-9-2015 at 15:03


Thanks bert I am working on swageing aluminum det capsules at the moment and was wondering if you were starting from flat stock or preformed cups.
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[*] posted on 17-9-2015 at 23:59
20 mm shaped charge second try.


Well I had a success and a fail with the second 20mm csc I have a cool looking carrot sticking out of plate no 2, and my tack welds failed so the plate stack broke apart before I got full penetration.

The charge was exactly the same as charge no 1 but I used 3x standoff and had 100mm of tacked plates on top of the 32mm plate, i still got 79mm penetration but as I said it looks like the stresses were to much for my tacks so the jet broke the stack apart and it stop penetrating after the 79mm mark. :mad:

Looks like I will need to weld the plates better for the next test nuxy.

[Edited on 18-9-2015 by nux vomica]

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