Sciencemadness Discussion Board

Unconventional Shaped Charges

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gnitseretni - 23-10-2011 at 15:59

Quote: Originally posted by watson.fawkes  
On the other hand, it might be more, because a small block might act like a thinner block, more flexible and getting out of the way.


Yeah, that's why I think penetration will be less in a bigger block. I believe the steel "getting out the way" decreases resistance, resulting in increased penetration.

MrRedox602 - 7-1-2012 at 15:52

No cross-posting.

[Edited on 8-1-2012 by Ramiel]

gnitseretni - 4-3-2012 at 13:29

Did another shaped charge. But it was a failure. Wasn't nearly as loud as it shoulda been. I think I know what happened. The detonator was too short, too little stuck out underneath the 3/4" thick cap that I turned from MDF to center the detonator. I thought about turning a concave cavity on the inside of the cap, but no.. numbnuts (me) was too impatient!! :P
I'm quite pissed off at myself as I had high hopes for that beautiful shiny liner that I turned on my lathe to a uniform wall thickness of 0.95mm. And now it's gone :(

http://youtu.be/KXVbMwotE9g

Farnsworth - 11-5-2012 at 18:48

Something I found fascinating in the "Brief History of Shaped Charges" text:

"Watson stated that the lined cavity effect required only one-fifth to one-sixth as
much explosive as an unlined booster, and the lined cavity charge would function
over a considerable air gap. This fuze was, in effect, a detonator using the shaped-
charge principle."

I'm surprised this didn't cause more of a stir. A method of articulating a detonator in a way that conserves a considerable amount of explosive material (and its corresponding reagents).

Perhaps better suited to a different topic, but I think a discussion on the construction of low-volume caps utilizing this effect would have some merit.

Sorry for making a jump-in for my first post. I'm a long-time lurker and was once an active poster over on RS. Physics is more my specialty than chemistry, but damn if energetic materials don't tickle my pickle.

Hennig Brand - 6-6-2012 at 15:02

Well here are a few pictures from a shaped charge experiment. Performance was nothing to brag about, but I learned a few things.
The liner was a 1.5" ID, 60 degree angle copper cone with ~2% CD wall thickness. Standoff was 1.5 times CD. Charge head height was only about 1 CD. If I had more explosive prepared, 1.5 times CD or more for charge head height would have been better.

Charge was 114g of 16% inerts ETN platique, with a density of ~1.43g/cc. Initiation was accomplished with 1g PETN base charge, 0.3g lead azide and basic lead picrate flash igniter in aluminum tube & ignited by fuse.

That small hole in the last steel piece actually goes more than half way through. Total penetration was ~1.88 inches or ~1.25 times CD. It is obvious from inspection of the plates that the jet trifurcated, or split into three parts. Performance wasn't great, but several things were less than optimal. The aluminum form, used to electroform the cone, was turned on an older lathe and the resultant cone was not symmetrical by quite a bit (I am starting to realize just how important perfect symmetry is). The charge head height should have been larger for best results. The SC might have performed better if the liner thickness was 3% CD instead of 2%.

I am going to find someone with a precise lathe to clean up my aluminum form.

BTW, each steel piece is 3/4" thick.


SC 1.JPG - 343kB SC 2.JPG - 261kB SC 3.JPG - 218kB

SC 4.JPG - 224kB SC 5.JPG - 216kB SC 6.JPG - 393kB

[Edited on 7-6-2012 by Hennig Brand]

gnitseretni - 6-6-2012 at 16:10

Some improvements would be like you already said, thicker liner, more head height, perhaps increase standoff to 2 CD.
Also, that blue thingy.. It looks like it was made of plastic and I assume that was what held the liner in place? If so, no good. You want your liner to sit on a strong edge that ain't going nowhere. Next time, cut a thin slice of the same diameter pipe you use for confinement and cut a little piece out of the ring. Squeeze it together and place it inside the pipe and tack it in place. Make sure it's level otherwise your liner sits at an angle.. unless you're going to face it in the lathe then it won't matter.
Also, one reason I like to use liquid HE is because it has a perfect uniform density every single time. Making plastic HE at home, your density will vary with each batch.
Just my 2cents. ;)

Hennig Brand - 6-6-2012 at 18:31

Thanks for the feedback and I like your method of locking a cone into a steel pipe.

The black pipe in the picture is just black ABS 1.5 inch sewer pipe. That blue plastic cone holder was an ABS end cap that I drilled a centered hole in leaving a lip for the cone base to sit on. ABS cement was used to glue the end cap (cone holder) to the pipe. I could upgrade to a heavier ABS end cap for another dollar or so. The heavier end caps, in the plumbing section, looked to be about 3 times as thick as the one I used (about the same thickness as the pipe).

You would probably advise against using plastic then. I assume you thought the black pipe was steel.

I am unsure how suitable the ETN plastique I am using is for shaped charges. It appears to be very brisant though which is a good sign. Uniform density without effort is an area where the liquid high explosives have it over the plastiques, that is true. I may have to try a SC with a liquid nitric ester, just for comparison purposes. As far as handling properties and safety goes though, plastic explosives are so much better.

edit:
Yeah, I guess I forgot to explain that the pipe was ABS in the above description. I thought it would be obvious, but now that I am looking at the pictures I can see that it isn't.

[Edited on 7-6-2012 by Hennig Brand]

gnitseretni - 6-6-2012 at 19:35

Oops, yeah I thought it was steel. Was kinda wondering why you'd use a steel pipe and then hold the liner in place with something made of plastic :P

I don't advise against plastic. I'd say use whatever material is easiest for you to work with. Perhaps not the best advise from a safety standpoint. ;)

Farnsworth - 20-8-2012 at 18:18

I was doing some Googling concerning shaped charge patents earlier today and stumbled across a discussion on another site related to military applications.

It's an imageboard, so foul language warning. The TC gets a few minor points wrong, but he does go into some excellent detail and cites sources.

http://www.operatorchan.org/k/res/17785.html

Bonus points because two of them talk about this place.

Fulmen - 29-8-2012 at 04:47

Need some feedback on liner shape, I'm working on deep draw fabrication of conical liners. I've already made a die to draw 0.5mm copper disks down to a 15mm OD x 10mm cup, next is deciding on the final shape. I could go for a straight cone ending in a 2mm radii, but a funnel would probably be easier to get right. If I can draw it down enough I could end up with a 4mm OD stem, 10mm long and with a 2mm radius at the top, wouldn't this be a better design than a straight cone?

pyro10%school0% - 26-11-2012 at 22:28

could i use coke tin/aluminium can to make a shaped charge bottom of that have something like a plate...

CaliusOptimus - 2-12-2012 at 15:38

Check out this shaped charge I found on the tube:

http://www.youtube.com/watch?v=QlTFBvsSijU

franklyn - 20-12-2012 at 22:00

Quote: Originally posted by CaliusOptimus  
Check out this shaped charge I found on the tube:

http://www.youtube.com/watch?v=QlTFBvsSijU


That is a very good example of improvisation.

Observing closely the interior of the liner one can see a soldered seam.
It is apparent that the cone is a rolled up pie section of a circular piece
of sheet metal , likely around 120 degrees. This serves to show that
one need not be all that fancy to form copper for the liner.

_______________________________________________


Steel Cutting with High Explosive Charges
www.dtic.mil/dtic/tr/fulltext/u2/479244.pdf

Explosive Forming of Metals
www.dtic.mil/dtic/tr/fulltext/u2/605372.pdf

Method for Calculating the Initial Fragment Velocities from Hollow Warheads
www.dtic.mil/dtic/tr/fulltext/u2/441810.pdf

.

franklyn - 25-12-2012 at 20:53

This is just cool.
Consider that the jet of a shaped charge will be ten time faster
than the high velocity rounds seen here. The way the soft lead
splats against hard armor is the same way the shaped charge
jet does but because of the higher pressure it generates , it
pushes through the armor in the same way that the armor
piercing rounds do also seen here. The gelatin shots show the
effect of cavitation produced on elastic medium at high velocity.

1 million frames per second slow motion video of bullet impacts
www.youtube.com/watch?v=QfFoMyMoiX4


84mm Carl Gustav HEAT 751 shaped charge tamdem warhead
www.youtube.com/watch?v=q6j9wEF1sf8
the follow on charge passes through the hole made first by the
shaped charge. Except for size this is essentially a Durandal fired
sideways. => www.youtube.com/watch?v=_m-buvo3dj4
www.sciencemadness.org/talk/viewthread.php?tid=12885#pid1633...

.

gnitseretni - 28-12-2012 at 12:08

Another failed SC. Like the third one in a row or something. Pretty frustrating! :(

2.3mm thick walled, 1.5" diameter, 60 degree electroformed copper cone. Yeah, pretty thick liner.
Aluminum container, 2" ID, 2-1/4" OD.. so 1/8" thick walls. Height of container about 6".
Standoff was 6" (4CD). This charge had subcalibration. Walls off container were 1/4" from base of liner.
HE used was methyl nitrate/nitromethane (25/75 % by volume).
Target: 4 mild steel plates stacked together, bottom 3 plates were 2" thick and top plate was 1-1/2" thick, so total of 7-1/2".

Not sure why this SC failed. I wonder if I didn't get full detonation. It could be that I didn't mix the MN with the NM well because shaking it was a little nerve wrecking so maybe I shook it a little too careful :P Or maybe they separated in two layers (MN is heavier after all). Time between mixing and detonation was probably about 5 mins.
The explosion sounded a little different than usual as well. It wasn't a sharp crack, it was more like ANNM, a gutsy boom.

Looking at the top plate you can see the charge included subcalibration. There's a nice round pattern around the hole left by the jet, not the other much wider hole. And it's odd there are two holes. One was clearly produced by the jet because the copper slug is still in it and there's shiny pink copper all over, but the walls of the other hole, which is much wider and just as deep if not deeper, is not lined by shiny pink copper.. it's lined with a color that looks a hell of a lot like brass. I once melted some aluminum and mixed in a little bit of copper. When cooled it looked like brass, just like this. So I'm guessing it was mostly aluminum with a tiny bit of copper from the liner mixed in that made the wide hole.

I went through quite a bit of trouble trying to make sure everything was as symmetrical as possible because I've been trying to improve on the 6-1/4" penetration I got a while ago. I thought the thick liner would perform great with the added subcalibration.

I won't go through this trouble again. The SC that penetrated 6-1/4" was everything BUT symmetrical. The container was thin walled stainless steel off round tubing. The liner was electroformed on an off round fence cap. The container however was fairly tall (a lot of head height), I wonder if that was why it performed so well. Actually penetration was only like 3 and a 1/4 CD or something which really isn't that impressive, but considering how far from perfect everything else about the charge was, I'd say it did pretty well.

That was my last electroformed copper. These liners do work but they take so long to make. I'll give the rubber pad forming process a try in the future.

Video: http://youtu.be/DbTA-MNA-kc

Sl731710.jpg - 76kB Sl731712.jpg - 114kB Sl731713.jpg - 172kB Sl731714.jpg - 162kB Sl731715.jpg - 103kB

[Edited on 12-28-2012 by gnitseretni]

gnitseretni - 29-12-2012 at 21:12

Did a heck of a lot of reading up on shaped charges since yesterday. Went through lots of PDFs, one in which they confirmed what I suspected why that one charge that penetrated 6-1/4" did so well compared to the others.. lots of head height. Without the use of a waveshaper, in order to get a stable/flat wave before it reaches the cone is by increasing head height. I'm pretty sure this is why my previous SC's failed. I'm not sure if lack of head height was the only thing to blame for my last SC failure though. At least in my other SCs I used pure PGDN. In my last SC I used methyl nitrate mixed with nitromethane. Maybe the gap in VOD between these two screwed up the wave. But hell I don't know, and probably never will, unless I find a source that says otherwise. Best to use just one HE (no mixtures), and a liquid one at that, so density is always the same which leaves one less variable to worry about.

Another source mentioned the varies ways SC liners are manufactured commercially. I think I'll stick to electroforming liners as apparently electroformed liners have potential for being excellent performers. The key to a good liner, other than the obvious ones such as the right wall thickness, perfect symmetry, etc.. is small grain size. The smaller the grain size, the longer the jet can stretch without breaking up. This is why electroforming is a great way to make liners as you can get an extremely small grain size, as opposed to, for example, cones turned from a solid copper rod which have a large grain size. Cones produced by metal spinning are supposed to be heat treated to relieve stresses in the cone. IIRC, I think it said 30 mins at 500C. It didn't say what to do with it afterwords, quench it or let it cool slowly. Then again, they were talking about liners produced by the metal spinning process in general, no mention of types of metal or anything. Quenching copper in water does not work harden it, but that doesn't go for all metals. On the other hand I don't think it matters. Not for copper anyway, I found a PDF where they tested annealed copper liners vs non-annealed liners and there was no difference.

Ways to improve penetration that I have found so far is by using waveshapers and trumpet shaped liners over conical shaped liners. However, trumpet shaped liners are less forgiving to imperfections than cone shaped liners. With trumpet shaped liners, the top of the liner is cylindrical (or near cylindrical) as opposed to a sharp point with cone shaped liners. As Axt has already demonstrated, no standoff is required with cylindrical liners as the jet is already formed when it reaches the bottom of the charge. The trumpet shaped liner is like a hydrid between a conical and cylindrical liner. The cylindrical part of the trumpet shaped liner is to increase jet tip velocity to increase penetration. Increasing jet tip velocity also stretches the jet further than is possible with conical liners and this increased stretching of the jet is why trumpet shaped liners are less forgiving to imperfections in the liners. A trumpet shape btw is just a modified cone. You can get increased penetration using conical shaped liners by for example using two different slopes (steeper slope towards apex). Steeper slope means faster jet tip velocity.

Anyways, I guess I'm just kind of summarizing some of the things I've read over the last 1-2 days. Thought I'd post it to both help me remember for later and in case there are still others experimenting with shaped charges. Are there?

PHILOU Zrealone - 2-1-2013 at 09:32

Gnitseretni,
I didn't knew you question about mixing methyl nitrate and nitromethane was to make shaped charges.

I think that both are too slow detonating HE to make shaped charges.
http://en.wikipedia.org/wiki/Shaped_charge
Small apex angle is sometimes responsible of bifurcation.

The speed of sound in copper liner is arround 3,9 km/s.

Wikipedia states that MN is arround 8 km/s VOD but this is wrong ... in reality it is 6,3 km/s and NM is in the same range!
In the cavity this speed is slowered and is probably too close to the liner speed of sound (3,9 km/s)...

Usually to make shaped charges one need to get high VOD HE like RDX (over 8 km/s) or HMX (over 9 km/s).

I remember that usually one must be over 7 km/s HE to be able to cut steel with a shaped charge.

Also in your movie arround 8/9 seconds one can see that the upper blast is directed to the left and forms an angle of 30° with the vertical. This may come from the cutted tree on the side or from an inherent unstability/unsymetry.
Could it come from the detonator?
I suspect that if the detonator is not strictly vertical (parallel to the shaped charge axis) then detonation can behave like it did in your detonation.

What was the HE in your detonator? Where and how was it placed... Your photos don't show the detonator.

gnitseretni - 2-1-2013 at 16:13

Hmm... I thought MN was comparable to NG in power and VOD.

I turned the container on my lathe as well as the top that held the detonator perfectly centered and vertical. (Detonator was NHN with ETN base with nichrome wire embedded in NHN and fired remotely) I turned the copper cone down as well. When it was done plating, I chucked the cone form with the copper cone still on, in my 3 jaw chuck. I'll admit I didn't check for runout with my dial indicator. If there was any runout it would have resulted in non uniform wall thickness and I only checked the wall thickness on one side.
I got a little in a hurry in the end. I wanted to use MN only, but got impatient and added NM.
After all the research I did after this SC, I realized that the liner was probably way too thick, plus I didn't use enough head height. Add to that the poor choice of HE and it's no surprise the SC was a failure. I'll stick to PGDN from now on. It has proven to work just fine for SC's.

VladimirLem - 3-1-2013 at 02:36

the explosive would work at a glass-liner...
AND the liner is MUCH to thick walled...1.5mm walled would be maximum, even with HEs like PETN...0.8-1.0mm will work fine with etn or similar stuff

[Edited on 3-1-2013 by VladimirLem]

[Edited on 3-1-2013 by VladimirLem]

franklyn - 24-1-2013 at 00:14

Improvised Shaped Charges with Plastic Explosive Filler

www.dtic.mil/dtic/tr/fulltext/u2/283016.pdf

.

Wine bottle bottoms as liners.

NeonPulse - 3-8-2013 at 01:40

i was wondering if anyone else has tried the bottoms of wine bottles as a liner? I thought that they may be too thick but after testing one to see for myself, the results were OK. so i used 225g ANNM but in fairly weak confinement- a high pressure plastic gas pipe. The liner was epoxied in place.the target was 4 6mm structural steel plates stacked up, and i gave it minimal standoff of 1.5 cone diameter and was very surprised at how well this liner performed. A nice round 25mm hole and 30mm deep. The first two plates had full penetration and the others dented fairly hard. There was also a rather large plug of highly compressed powdered glass that was slightly fused by pressure and heat i suspect. These plugs were very hard. A lot harder than the actual glass it was made from and almost like stone. Took a while to clear them out to see the damage.. All up i would say the cone did well and i will be testing another one or two very soon but this time using stronger confinement and greater standoff distance.

glass plugs shrunk pic}.JPG - 60kB

plates 6mm{shrink pic}.JPG - 65kB glass cones smallpic.JPG - 22kB

Melmoth - 22-8-2013 at 00:56

Quote:

Explosively loaded champagne bottles and other conical
based bottles for demolition and special applications is very
well known and commonly taught for military use. It is
believed that such practice dated to a period of improvised
munitions used early in World War II


Attachment: Glass as a shaped charge liner material1.part1.rar (1.4MB)
This file has been downloaded 607 times

Attachment: Glass as a shaped charge liner material1.part2.rar (760kB)
This file has been downloaded 567 times


SherlockHolmes - 19-10-2013 at 12:02

I also tried to do a shaped charge but did not work. Any idea why? http://www.youtube.com/watch?v=jU3TIpoMQN4

VladimirLem - 19-10-2013 at 13:00

Quote: Originally posted by SherlockHolmes  
I also tried to do a shaped charge but did not work. Any idea why? http://www.youtube.com/watch?v=jU3TIpoMQN4


hm...hard to say...at first, you took some test tube as the detonator cap....im not sure if this is the best choice...for ignition of ANFO or other normal explosive devices it will work good, but at a shaped charge it can/could be that the detonation wave does not move straight to the apex (hard to describe :/ ) there is simply to many surface where the detonation can start....a thick walled tube, with extreme thin bottom would be better, so that you can bet, that theres the point, the detonation in the main charge starts...

other possible factors could be the liner....datas? (wallthickness, diameter...) what about the head-hight (distance from INI to top of cone - seems to short)...

the explosive seems optimal (powerfull/fast enough) for this job...

---

edit:

another other reason could be, that your selfmade liner where soldered and the liner colapsed at this weak part without forming a jet....

[Edited on 19-10-2013 by VladimirLem]

Pard - 11-1-2014 at 04:49

Quote: Originally posted by NeonPulse  
i was wondering if anyone else has tried the bottoms of wine bottles as a liner? I thought that they may be too thick but after testing one to see for myself, the results were OK. so i used 225g ANNM but in fairly weak confinement- a high pressure plastic gas pipe. The liner was epoxied in place.the target was 4 6mm structural steel plates stacked up, and i gave it minimal standoff of 1.5 cone diameter and was very surprised at how well this liner performed. A nice round 25mm hole and 30mm deep. The first two plates had full penetration and the others dented fairly hard. There was also a rather large plug of highly compressed powdered glass that was slightly fused by pressure and heat i suspect. These plugs were very hard. A lot harder than the actual glass it was made from and almost like stone. Took a while to clear them out to see the damage.. All up i would say the cone did well and i will be testing another one or two very soon but this time using stronger confinement and greater standoff distance.


Why to use just the bottoms? I've seen before to use the whole bottle without the neck. Like wine bottles. Is it better using just conical bottom?

By the way, how do you guys design your copper cones? I thought about maybe going to metal work place to ask to do it. It is a strange request but I'm sure they would. It's not like they'd realise what it is for.

NeonPulse - 12-1-2014 at 15:27

Quote: Originally posted by Pard  
Quote: Originally posted by NeonPulse  
i was wondering if anyone else has tried the bottoms of wine bottles as a liner? I thought that they may be too thick but after testing one to see for myself, the results were OK. so i used 225g ANNM but in fairly weak confinement- a high pressure plastic gas pipe. The liner was epoxied in place.the target was 4 6mm structural steel plates stacked up, and i gave it minimal standoff of 1.5 cone diameter and was very surprised at how well this liner performed. A nice round 25mm hole and 30mm deep. The first two plates had full penetration and the others dented fairly hard. There was also a rather large plug of highly compressed powdered glass that was slightly fused by pressure and heat i suspect. These plugs were very hard. A lot harder than the actual glass it was made from and almost like stone. Took a while to clear them out to see the damage.. All up i would say the cone did well and i will be testing another one or two very soon but this time using stronger confinement and greater standoff distance.


Why to use just the bottoms? I've seen before to use the whole bottle without the neck. Like wine bottles. Is it better using just conical bottom?

By the way, how do you guys design your copper cones? I thought about maybe going to metal work place to ask to do it. It is a strange request but I'm sure they would. It's not like they'd realise what it is for.


I just used the bottom so I could get better confinement for the annm. I also made another one like this but with steel tube and it worked a lot better.check it out on my YouTube channel annm shaped charge by putitbak. Cones can be made in many ways. I've used copper sheet beaten into form,ans thin sheet bent int a cone too. The solid cones worked the best. I'm not too sure how you would go at getting one made as its not that simple a task. Browse this whole thread sa it is full of helpful hints and methods on making cones and the concept of ad's inggeneral. It really helped me out.

franklyn - 5-2-2014 at 21:59

Methodology for modeling of the jet formation process in linear sharped charges

www.chemikinternational.com/pdf/2011/01_2011/chemik_2011_65_1_32-35.pdf

.

markx - 10-2-2014 at 04:04

Anyone ever tried these as liners? :D :

http://www.ebay.com/itm/500-UK-77-Cone-Studs-Spike-Charged-G...

Works pretty sweet....


12mm aluplex tubing as the casing with the stud attached...the witness plate underneath is 8mm mild galvanised steel:

090220141112.jpg - 115kB


Loaded with 2,88g phlegmatized PETN (10% PIB+methyl riccinoleate):

090220141111.jpg - 137kB

Standoff attached...20mm :

090220141114.jpg - 141kB

Primed and ready to go:

090220141115.jpg - 184kB

From the top after firing under sand:

100220141120.jpg - 136kB

From the bottom after firing...clean through 8mm mild steel:

100220141121.jpg - 142kB

Judging from the entry point I would say that the standoff was a bit too small...an additional 5-10mm would have probably been beneficial.

[Edited on 11-2-2014 by markx]

VladimirLem - 10-2-2014 at 09:43

Quote: Originally posted by markx  

Works pretty sweet....


well done....thats a really sweet project ;)

and i thought my 1" cone was pretty little :D

Hennig Brand - 10-2-2014 at 11:32

Impressive that it works so well even though it's so small. Nice test.

markx - 11-2-2014 at 01:27

Quote: Originally posted by Hennig Brand  
Impressive that it works so well even though it's so small. Nice test.


Yes, I did not expect much of a result from this makeshift test...hence the sloppy design. But as it worked against all odds, I think that many improvements are in order.

NeonPulse - 14-2-2014 at 04:15

Quote: Originally posted by markx  
Anyone ever tried these as liners? :D :

http://www.ebay.com/itm/500-UK-77-Cone-Studs-Spike-Charged-G...

Works pretty sweet....


12mm aluplex tubing as the casing with the stud attached...the witness plate underneath is 8mm mild galvanised steel:




Loaded with 2,88g phlegmatized PETN (10% PIB+methyl riccinoleate):



Standoff attached...20mm :



Primed and ready to go:



From the top after firing under sand:



From the bottom after firing...clean through 8mm mild steel:



Judging from the entry point I would say that the standoff was a bit too small...an additional 5-10mm would have probably been beneficial.

[Edited on 11-2-2014 by markx]


Great test.It just goes to show that you dont need to go big for good results. i actually looked at similar items on ebay but never found any suitable looking ones. i guess i did not look hard enough! i only as looking at copper though and that is why my searches turned up nothing. right now im working on electroformed copper liners and they look really promising to test, consistent and very easy to produce.. much more consistent than say hammering a liner from copper or shaping thin sheet into cone forms. I do have some pics to post of a 25gMHN linear SC when i get around to it, it worked good but not great. ill do that soon .

markx - 14-2-2014 at 05:20

Electroforming is a versatile tool....I earned my bachelor degree on the subject of pulse plating thick layers of metal/alloy on geometrically complicated substrates (concave horrors with near zero electrical field in them). Initially electroforming moulds for production of plastic details out of copper and nickel. Then electroforming Ni/Mo/Cu alloy details for hi temp fuel cell construction. The idea was to plate an alloy with adjustable thermal expansion coefficient (ceramic electrodes of the fuel cell did not like the excessive expansion of the support frame ;) ). The main problem with plating thick layers (beyond decorative or corrosion resistant effect) is the formation of dendrites. To counter it, one can use basically three approaches:
a) very low current density
b) additives (mostly surface active detergent type compounds)
c) pulse plating

The most effective being pulse plating....it allows the cathion concentration near the electrode surface layer to replenish between current pulses, therefore minimizing the formation of dendrites. And one can reverse the polarity of applied voltage to turn the cathode into anode for a certain percentage of duty cycle. As dendrites are predominantely formed during the cathodic cycle, they also are predominantly dissolved during the anodic portion of cycle.

markx - 14-2-2014 at 13:21

Utter success!!

The same type of setup as seen in my previous pictures. But this time the target was 15mm steel sheet.

With 3,5g 10% phlegmatized PETN charge at 20mm and 40mm standoffs:

140220141125.jpg - 175kB

The 40mm standoff did not penetrate the target...it was 2mm shy of the objective after measuring channel depth.

But the 20mm standoff:



140220141126.jpg - 189kB

140220141127.jpg - 138kB

140220141128.jpg - 160kB

Like a hot needle through butter :D

Btw. I really do need a decent camera and some practice in the field of photography...these blurry pictures are frankly embarrassing.

[Edited on 14-2-2014 by markx]

markx - 18-2-2014 at 00:38

A bit clearer pictures of the last test are in order....

Comparison of targets:

20140214_200208.jpg - 112kB


The construct for creating the jet:

20140214_202834.jpg - 173kB


Entry points on the 15mm target at 40mm and 20mm standoff:

20140214_204554.jpg - 192kB



20140214_204600.jpg - 193kB


Exit point of the 20mm standoff:

20140214_204325.jpg - 198kB


Entry and exit points on the 8mm target from the first test (20mm standoff)


20140209_175748.jpg - 195kB

20140209_175912.jpg - 120kB




NeonPulse - 23-2-2014 at 02:07

so finally i got around to testing an electroformed liner produced using a method found in this thread. i suspected that it would have performed quite well and i was not disapointed! the liner thickness measured 1mm evenly after cleaning it up some.i forgot to measure the angle but i guess around 60deg. the portion of the cone used was 20mm wide at the bottom to fit in the tube used and with the end cap gave excellent confinement for the charge, which was a mix of 75%MHN and 25%ETN and weighed 16g. initiation was electric, using 400mg lead azide (more than enough...)
Standoff was 2 cone diameters at 40mm. Penetration was pretty good: 38mm into a very hard steel sledgehammer head with a perfectly formed jet that went straight down. No carrot but a nice copper colour lining the hole. looking forward to testing some more perhaps with a liquid ester or cast ETN. i think with some tweaking the penetrating distance could be more. i have always wanted to try a lens.

done cone.jpg - 76kB jet2.JPG - 35kB sc1.jpg - 76kB

jet hole1.JPG - 60kB


NeonPulse - 23-2-2014 at 02:27

also a linear SC was tested on a 10mm thick bit of hardened steel. This charge was 24g MHN with a 400mg lead azide cap fired electronically also. Results were a poor 5mm penetration which i think was due to a poor design and next to zero standoff distance. The casing was a 70mm long Al channel that had 2.5mm thick walls with 2mm thick liner at 90 degree angle the ends were also Al and it was all held together with JB cold weld epoxy. that stuff is brilliant! the liner was mangled in the groove and most of it eventually was pried out in order to see the cut. results could certainly be improved here. seems a jet was formed but im guessing that lack of stronger confinement and no standoff played a big part in its reduced cutting ability.

linear jet2.jpg - 90kB IMAG0189.jpg - 45kB

linear jet.jpg - 60kB

VladimirLem - 23-2-2014 at 02:54

Quote: Originally posted by NeonPulse  
also a linear SC was tested on a 10mm thick bit of hardened steel. This charge was 24g MHN with a 400mg lead azide cap fired electronically also. Results were a poor 5mm penetration which i think was due to a poor design and next to zero standoff distance. The casing was a 70mm long Al channel that had 2.5mm thick walls with 2mm thick liner at 90 degree angle the ends were also Al and it was all held together with JB cold weld epoxy. that stuff is brilliant! the liner was mangled in the groove and most of it eventually was pried out in order to see the cut. results could certainly be improved here. seems a jet was formed but im guessing that lack of stronger confinement and no standoff played a big part in its reduced cutting ability.





nice projects :)

I think that the 2mm thick liner at the linear shaped charge should be replaced to a 0.5-1mm to get optimal results

how did you get the coppercone off the kathode?

I made some 1" diametre 42dagree cone and fucked it up...i couldnt get it off the kathode:(

NeonPulse - 23-2-2014 at 03:29

it was hard, going around it with a knife several times and tapping it with a hammer,the Al not the copper, and the viabrations caused it to just fall off, alot of it i did not need to use so i could bend and tear also. before placing it in the plating bath i sanded it to a glass like finish too, i think that helped it pop off easier.

markx - 23-2-2014 at 16:48

Quote: Originally posted by NeonPulse  
it was hard, going around it with a knife several times and tapping it with a hammer,the Al not the copper, and the viabrations caused it to just fall off, alot of it i did not need to use so i could bend and tear also. before placing it in the plating bath i sanded it to a glass like finish too, i think that helped it pop off easier.


Try conductive silver paint as the intermediate layer between cathode and the plating. It makes separation much easier and one can use a nonconducting object as the mould for the plating.....paint will act as cathode on the surface. The only downside is the cost of the paint, but a failure to separate the liner is probably even more frustrating.

You could also try a graphite coating as the intermediate layer, although I don't have any personal experience to claim or deny it's effectiveness.

VladimirLem - 24-2-2014 at 09:31

Quote: Originally posted by markx  

Try conductive silver paint as the intermediate layer between cathode and the plating. It makes separation much easier and one can use a nonconducting object as the mould for the plating.....paint will act as cathode on the surface. The only downside is the cost of the paint, but a failure to separate the liner is probably even more frustrating.

You could also try a graphite coating as the intermediate layer, although I don't have any personal experience to claim or deny it's effectiveness.


cool idea :)

i had the idea of plating a extreme thin layer of tin- or lead on the cathode and then plating the copper cone...after the cone is ready, then heating to the melting point of tin/lead....but im too lazy to try that, so i think im going to buy silver paint :D

NeonPulse - 8-3-2014 at 03:25

Another attempt was made using another electroformed liner. instead of plating for 24 hours it was left to plate for 32 hours. the thickness was increased to around 1mm.
the performance of this liner was also excellent. the filling this time was 11mls of good old NG and to increase the density, 8g ETN and 1g NC were added. fired with a 600mg MHN/200mg Lead azide. A nice even jet was formed and no carrot left in the hole.
the penetration was a rather nice 42mm which is just over 2 cone diameters.
I am pretty impressed with these little liners perfomance especially considering how hard this particular steel is.
My aim is to go all the way through it and with a little tweaking i think that it is realistic as there are only another 30mm to get through. As for the conductive paint i have ordered some- no shit it is expensive, but worth it since i dont have access to a lathe to make my own forms. A form is to be made at the optimal angle of 42 degrees and plated- well see how it goes if it works as well as the others then it will be formidable.



cone.jpg - 73kB

jet hole.jpg - 70kB

markx - 10-3-2014 at 00:31

Quote: Originally posted by NeonPulse  
Another attempt was made using another electroformed liner. instead of plating for 24 hours it was left to plate for 32 hours. the thickness was increased to around 1mm.
the performance of this liner was also excellent. the filling this time was 11mls of good old NG and to increase the density, 8g ETN and 1g NC were added. fired with a 600mg MHN/200mg Lead azide. A nice even jet was formed and no carrot left in the hole.
the penetration was a rather nice 42mm which is just over 2 cone diameters.
I am pretty impressed with these little liners perfomance especially considering how hard this particular steel is.
My aim is to go all the way through it and with a little tweaking i think that it is realistic as there are only another 30mm to get through. As for the conductive paint i have ordered some- no shit it is expensive, but worth it since i dont have access to a lathe to make my own forms. A form is to be made at the optimal angle of 42 degrees and plated- well see how it goes if it works as well as the others then it will be formidable.



Excellent work! What kind of plating bath are you using for the copper electroforming? The regular acidified sulfate? I see a familiar healthy dendrite formation on the cone. Have you tried any brighteners in the bath, they do supress some of the dendrite growth and make for a more uniform coating.

The price of the conductive paint is really demotivating, but a small amount will go a long way with this substance. I have found it is best applied via an airbrush...guaranteed uniform coatings and no blind spots that could ruin the plated detail. Since you have already ordered the paint, I would suggest the minor additional investment into a cheap airbrush. They can be had for about 20$ or less on ebay and make for a very decent tool in that application.

ecos - 25-5-2014 at 08:35


Did anybody try to do shaped charges with NG Gel ?

I mean to pour the NG Gel in the container and let it cool down and use it afterwords.

Dornier 335A - 25-5-2014 at 10:49

Correct me if I'm wrong, but isn't gel one of the worst things to put in a shaped charge? Air bubbles will easily form and get trapped inside it, and that will create hot spots that affect the shock wave. Just using a liquid explosive would be better.

magneet - 25-5-2014 at 13:24

At what point does a NG gel have to cool down?

why gelling it?

ecos - 25-5-2014 at 14:02

Quote: Originally posted by Dornier 335A  
Correct me if I'm wrong, but isn't gel one of the worst things to put in a shaped charge? Air bubbles will easily form and get trapped inside it, and that will create hot spots that affect the shock wave. Just using a liquid explosive would be better.


I am not sure about how fine are the air bubbles inside the Gel are. I also don't know if it would affect it that much or not. I think using EM powders also have bubbles. Nothing perfect

as a general speaking->yes you are right but I read that the mass of Gel will make the air bubbles get out. just a matter of time and it will be free of air bubbles but it would need a military detonator.

[Edited on 25-5-2014 by ecos]

NeonPulse - 27-5-2014 at 18:59

Quote: Originally posted by ecos  

Did anybody try to do shaped charges with NG Gel ?

I mean to pour the NG Gel in the container and let it cool down and use it afterwords.


are you gelling it with NC/Acetone? or using gelatin? i was wondering why you would need to heat it? just use more acetone. I myself wouldn't really want to heat any mixtures containing NG. i guess if you had enough diameter in in the charge it may work well, but personally i would go for a solid ester for ease of loading...

Use of conductive coatings for unconventional liners

NeonPulse - 4-6-2014 at 23:47

So i recently decided to try making another electroplated liner. For this process i filled a plastic funnel with car body filler and after it hardened i shaped a tip on the end as it was flat. The angle of the funnel is around 55-57 degrees. The resin form was sanded with some 800 grit sandpaper after this it was then coated with 3 nice even coats with a conductive silver paint. copper wire was threaded through 4 pre drilled holes on the base of the form and it was plated as usual. the coating of copper onto the form was nice and even all around and there was no thin or bare spots. In a previous experiment only one coat of the silver was applied but this produced poor results and a rather slow plating which was uneven in places. I also think the plating bath attacked the coating before a layer of copper was plated to protect it so 3 coats is needed for a faster plating and better coverage all round.The coating goes on very easily and any brush strokes with an artist's brush level out on drying leaving a nice even surface to plate onto. Using this process opens up an avenue to create liners of many sizes and shapes. fluted, trumpet and bi-angled or stepped liners are possible as long as you can form them out of the resin. i guess most materials that can be shaped conically or otherwise can be used (sealing porous surfaces first) and there also is no real limit to the size that can be formed like with cutting metal forms on a lathe. The cone was very easy to remove from the form and the paint stuck to the inside of the liner which is very easily removed with some acetone if it is a problem. The drawbacks are the general cost of a liner as a whole unit, the silver paint is pretty expensive at $10 for a mere 3mls vial but it really does go a long way if used sparingly. throw in the costs of the body filler, copper sulfate, Cu metal, acid and electricity to plate and you have a pretty expensive liner to produce. I haven't any access to a lathe so spinning liners is out for me else i would certainly attempt it. :)

plated cropped.jpg - 147kB

Manifest - 31-7-2014 at 14:46

Aluminium is easy enough to melt, there are many videos on youtube with people melting it using make-shift furnaces.
I'm thinking it would be easy enough to make a aluminium cone.
I am not sure how you could make the mold of it.

Oscilllator - 1-8-2014 at 02:28

Quote: Originally posted by Manifest  
Aluminium is easy enough to melt, there are many videos on youtube with people melting it using make-shift furnaces.
I'm thinking it would be easy enough to make a aluminium cone.
I am not sure how you could make the mold of it.

You can get countersink drills of diameter of about 40mm, and I imagine if you drill a hole into a suitable mold material (wood may even work considering the short timescales I have in mind) then you could pour a blob of molten aluminium into the conical depression, then push a cone into that depression, forcing the molten aluminium into a cone shape in a manner similar to a wax seal.

Having said that though, Aluminium is not a very good material to make a liner because of its low density.

Bert - 4-8-2014 at 06:53

Microwave kiln, scrap electrical wire for Copper and casting via Lost wax is possible with some skill.
http://microfoundry.storenvy.com/products/1270377-microfound...
There are several presentations on making one's own microwave kiln online.

But spinning Copper might be easier & quicker-

careysub - 4-8-2014 at 17:12

Quote: Originally posted by Oscilllator  

Having said that though, Aluminium is not a very good material to make a liner because of its low density.


That's not the only reason - aluminum has a tendency to react energetically with the explosive gases and burn up (that's why so many explosive compositions have "aluminized" versions).

Energetic Einstein - 26-8-2014 at 14:48

Quote: Originally posted by careysub  
Quote: Originally posted by Oscilllator  

Having said that though, Aluminium is not a very good material to make a liner because of its low density.


That's not the only reason - aluminum has a tendency to react energetically with the explosive gases and burn up (that's why so many explosive compositions have "aluminized" versions).


Are you assuming all of the aluminum liner is going to react upon detonation, or just that a thin layer of the aluminum will? Densities of metal liners can vary based on what material you are planning to penetrate.

careysub - 26-8-2014 at 15:27

Quote: Originally posted by Energetic Einstein  
Quote: Originally posted by careysub  
Quote: Originally posted by Oscilllator  

Having said that though, Aluminium is not a very good material to make a liner because of its low density.


That's not the only reason - aluminum has a tendency to react energetically with the explosive gases and burn up (that's why so many explosive compositions have "aluminized" versions).


Are you assuming all of the aluminum liner is going to react upon detonation, or just that a thin layer of the aluminum will?


Some portion of the liner seems to react with the combustion gases, and some portion may actually react with the target (if penetrating concrete, stone or soil).

Liners made of copper, and other typical dense materials produced deep narrow penetration holes, and are very well modeled by hydrodynamic numerical simulation.

Aluminum liners produce wider, shallower holes in concrete (they penetrate steel very poorly) and when compared to straight hydrodynamic simulations they show "non-ideal" behavior.

Instead of acting as a pure long-rod penetrator like traditional shaped charges they seem to create a local blast effect at the expense of penetration depth.

Quote:
Densities of metal liners can vary based on what material you are planning to penetrate.


This is indeed the case.

Aluminum reactivity may actually be desirable for low density targets like concrete (it might actually be reacting with the concrete also), depending on the effect you want to achieve.

There has been work done on creating even more reactive liners (lithium-aluminum alloys for example).

[Edited on 26-8-2014 by careysub]

Energetic Einstein - 26-8-2014 at 19:02

Interesting. So "Newtons Penetration Approximation" would be be useful when it comes to designing a liner?

I have never heard of a reactive liner before. What would be the be the use for it?

careysub - 26-8-2014 at 21:02

Quote: Originally posted by Energetic Einstein  
Interesting. So "Newtons Penetration Approximation" would be be useful when it comes to designing a liner?


Yes.

What you may read about shaped charges "burning holes", or that it sends in a jet of vaporized metal (even claims of it being a "plasma") are nonsense. The liner flows under the extreme pressure, but is solid. If it stretches too much (too much stand-off) it breaks up into particles and the penetration is much reduced.

Quote:
I have never heard of a reactive liner before. What would be the be the use for it?


They are a specialized thing, and I am not sure how much use they have actually seen.

Blowing bigger holes in concrete (as part of a dual warhead, perhaps) or in a rock face before setting a blasting charge.

There is overlap between shaped charges, explosively formed penetrators (the archetype is the Misznay-Schardin effect), and directed blast warheads; a charge can partake of more than one of these in its effect.

[Edited on 27-8-2014 by careysub]

Kumula

Laboratory of Liptakov - 4-9-2014 at 09:13

Needless to invent an aluminum insert. Needless to test copper plating. Needless to produce glass exploding shrapnel. Producing a steel mandrel with an angle of 84 degrees. A 0.55 mm Cu sheet strength. Or 1 mm. Hammer. Wooden chopping block. Steel rectangle. Propane-butane torch. The annealing. Production takes 10 minutes. No lathe. The pictorial compilation hopefully everyone will understand. Loaded: Cyklonan III. 25 grams. Density 1.2 g / cc. Bar diameter 26 mm. Distanc 39 mm. Steel 20 mm.
LL

kumula28 mm.jpg - 225kB

kumula komplet 28.jpg - 52kB

kumula to 20mm steel.jpg - 113kB

Laboratory of Liptakov - 6-9-2014 at 01:02

Yet he adds. A good combination would be: Base plate of 0.55 mm to produce the instructions here. And then called 'thinning Cu. On the strength of 1mm. The electrostatic field is applied a thicker layer on the top hat. This is needed. There is always the weakest plate. A risk of rupture. In this paper: posted on 23-2-2014 at 2:07 from Neon is the good work. But the hat is very rough. When an acidic solution of copper electroplating for copper is used a special additive. That will do it perfectly shiny hat. Like a mirror. Straight from the acid bath. His name is Novostar R1. It is added in an amount of about 0.1%. My secret composition, it can not produce. They must buy. But the results are absolutely perfect. Mirror smooth and clean surface.
LL

Energetic Einstein - 19-9-2014 at 14:47

How did you produce a mandrel that has an even 84 degrees? I assume you heated the copper plate with the propane torch then hammered the plate into a cone? What was the steel rectangle used for?

markx - 22-9-2014 at 02:32

I tried some of the nice Bachmann cyclonite as a shaped charge:




DSCF0708.JPG - 2MB DSCF0709.JPG - 1.8MB DSCF0710.JPG - 2MB DSCF0712.JPG - 2.1MB

Substrate is 30mm construction steel (we got greedy and added 2 plates under the charge). That was an obvious mistake, as the second plate effectively relaxed the impulse and stopped the jet. So instead of a nice penetration of 15mm steel we got a carrot stuck in the crater.

1.jpg - 142kB 2.jpg - 121kB 3.jpg - 148kB 4.jpg - 168kB 5.jpg - 157kB


work

Laboratory of Liptakov - 25-9-2014 at 05:41

Perfect work. Cyclonit is much stronger than Cyklonane. Course. Beautiful photos. Detonation seqence. Better of fireworks......:cool: I appreciate handmade. Good handwork? Good documentation? That is always a little. Many speech? Without documentation? That is always very much.
LL


[Edited on 25-9-2014 by Laboratory of Liptakov]

NeonPulse - 25-9-2014 at 16:33

Quote: Originally posted by Laboratory of Liptakov  
Perfect work. Cyclonit is much stronger than Cyklonane. Course. Beautiful photos. Detonation seqence. Better of fireworks......:cool: I appreciate handmade. Good handwork? Good documentation? That is always a little. Many speech? Without documentation? That is always very much.
LL


[Edited on 25-9-2014 by Laboratory of Liptakov]


I think you need a better translator. Some of your posts are pretty hard to understand.

Bert - 25-9-2014 at 20:18

One thing to consider when posting images of a charges effect on plates, etc.-

Put an object to show scale next to the crater. Ruler, meter stick, even a common coin.

As you observed, layered or discontinuous target plates can disrupt a jet... Just start out with a thicker piece of steel if you have access.

NeonPulse - 28-9-2014 at 18:20

How much jet disruption would occur if the plates were complety flush and smooth between them? I know the best representation is into a solid target but I would like to do an experiment on stacked plates to see the jet path through each individual plate and take a very close at them look with a microscope.
I'm not sure what I'd be looking for but it would be interesting, particularly where the jet tip stops. Perhaps examine the steel grain in comparison to un-stressed metal. That is if I can stack enough of them to stop full penetration. It would make a neat experiment and with more purpose than just punching holes through steel hammer heads.

markx - 29-9-2014 at 03:55

Only a test with stacked plates will show the real results, but from what I saw in my endeavour, the second plate stopped the jet dead still at the verge of the interface. The second plate was dented just like a blob of plastique had been detonated on top of it , but there was not the slightest of jet transition into it. The carrot was stuck in the crater also at the interface layer....one could basically see it from the other side of the plate, so thin was the metal left around the possible penetration area.

For comparison, here is a snapshot of 30mm uniform steel plate suffering from a 8,3g PETN shaped charge set off on top:


DSCF0125.JPG - 2.1MB

Unfortunately no scale reference again....oh well

The construction, placement and initiation of the charge were identical to the one portrayed in cyclonite test above. In this case there was no sign of the carrot anywhere to be found...I guess it disintegrated or was joined completely with the crater surface.

Sometimes there are very interesting and peculiar branching phenomenons of the jet that curve into the target off the main flow or move basically perpendicular to the main jet direction. Also in this shot one can see such effects on the top of the crater and also in the bottom part. Truly facinating subject...



[Edited on 29-9-2014 by markx]

EFP

Laboratory of Liptakov - 29-9-2014 at 08:47

It is the exact shape of the copper pads? If yes, does the hole inaccurate and causes material. It's like magic. Liquid copper drills (evaporate) steel. Again, a perfect piece of work. Markx: I see you have a lot of experience and you can make anything. Have you tried EFP? The basic proposal here. Diameter 68 mm = 2 mm copper..........:cool:
LL




efp_basic.jpg - 166kB

[Edited on 29-9-2014 by Laboratory of Liptakov]

markx - 29-9-2014 at 09:16

Quote: Originally posted by Laboratory of Liptakov  
It is the exact shape of the copper pads? If yes, does the hole inaccurate and causes material. It's like magic. Liquid copper drills (evaporate) steel. Again, a perfect piece of work. Markx: I see you have a lot of experience and you can make anything. Have you tried EFP? The basic proposal here. Diameter 68 mm = 2 mm copper..........:cool:
LL

[Edited on 29-9-2014 by Laboratory of Liptakov]


I must admit that I have been contemplating an efp design for a long time, but not yet gotten around to it. Seemed much more challenging to attempt a cumulative jet forming device at first. Guess I can try a shot at efp too...just maybe not to the scale that you propose. I'm afraid it poses a more serious challenge to silence the scream of that device than the actual construstion of it. A cumulative device I can shoot under the sand and silence it thus to an acceptable level. Burying an efp setup will take more commitment though.

EFP 2 inch

Laboratory of Liptakov - 30-9-2014 at 01:31


You have the same thoughts as me. A similar reasons. Therefore, even in LL EFP was not tested. It is technically very challenging project. The maximum diameter plates for tests I see is 50mm. This is the weight load from 60 to 100 grams. About 0.73 mm thick Cu. On your test track as possible. I know this is an expensive test. But: 50mm = penetration (up to) 25 mm steel. Large hole! It has all to see! .................:cool:

EFP 50.jpg - 95kB

ecos - 17-11-2014 at 10:20

Hi All,

This link has some nice resources if someone is interested : Link

copper cone

Laboratory of Liptakov - 20-11-2014 at 05:52

This is a good read. Technology of production of copper cone. (from the list)
Liners for Shaped Charges by Manfred Held (2001).pdf
LL

Sergeant James

Laboratory of Liptakov - 13-12-2014 at 07:27

I got a message from Sergeant James. It's a really tough guy...:cool:...LL

sergeant.jpg - 70kB

Explosively Formed Penetrator (EFP); Misznay–Schardin Effect

Hennig Brand - 25-12-2014 at 12:43

I started experimenting with explosively formed penetrators a little bit. Below are a few pictures of my first, and only, test so far. Thanks go to Markx for the idea of using coins to make the platters. In this test a Canadian dime was used. The coin was pressed into the curved shape (dish) using a ball peen hammer, a nut the appropriate size and a vise to apply force. The charge casing was made from a section of cardboard tube from a spent consumer fireworks aerial shell mortar tube, which happened to be the right size for the curved dime. The charge used was 8.5g of a putty explosive composed of, 81% ETN and 19% inerts, which was initiated with a 5mm id aluminum cap containing 0.5g of PETN and 0.15g LA. The target was 3/8" steel. The stand-off was arbitrarily set at 10cm.

Charge Casing:
D = ~1.8 cm id, ~2.4 cm od
L = ~3 cm

I think I was a little over enthusiastic when I chose to use 3/8" steel over 1/4" steel as the target. It didn't penetrate the 3/8" target, but it looked like it would have if the plate had been only 1/4". There was a large welt on the back of the plate. The width of the hole in the witness plate indicates low slug velocity and a short wide slug with low penetration. Higher velocities would cause the slug to elongate more and produce more penetration. According to Wiki, (referring to improvised devices I believe) "As a rule of thumb, an EFP can perforate a thickness of armour steel equal to half the diameter of its charge for a copper or iron liner, and armour steel equal to the diameter of its charge for a tantalum liner, whereas a typical shaped charge will go through six or more diameters."

The target was a bit more than half the thickness of the charge used and I am sure many things were not optimized. I will try it again possibly with a higher velocity explosive or with a 1/4" steel target.


Platter Dies.jpg - 178kB
Charge Front View.jpg - 329kB Charge Rear View.jpg - 344kB Cap Centering Bushing & Casing Plug (1).jpg - 489kB Cap Centering Plug & Casing Plug (2).jpg - 449kB Steel Target.jpg - 165kB
EFP in Line with Target (1).jpg - 187kB EFP in Line with Target (2).jpg - 196kB Witness Plate Front View Measurement.jpg - 251kB Witness Plate Rear View.jpg - 196kB


[Edited on 26-12-2014 by Hennig Brand]

VladimirLem - 26-12-2014 at 00:01

Pretty cool test you did, Hennig:)

I think the standoff is very important at EFPs too (like SCs)...
Maybe you give it a try with 50cm< standoff at the same CD?

perfect

Laboratory of Liptakov - 26-12-2014 at 01:26

Again a very good job Hennig. The best I've ever seen. Vladimir writes important thing. 10 cm distance is too small. I studied patents. Projektyl is not enough to shape. It must be at least 40 cm. Top 50cm. (for this diameter). I see significant deformation of steel 10 mm. This is the beginning of a very good result. In such a small scale are materials (steel) strength. A lower efficiency in explosives. It is due to finite size of an atom. I'll try to explain it differently: 1) For airplanes (1 km height) throw ant (5mm). He lands on the grass. Nothing will happen. 2) For airplanes (1km) throw a giant ant chitin (1500 mm). It certainly will be broken up into pieces. It is due to finite size of an atom. It is due to the number of atomic bonds at the object. I hope you understand me ...:)...LL

Fulmen - 26-12-2014 at 04:02

Nice work. I do second Vlads suggestion of increasing the standoff, also it would be interesting to place soft targets in between at intervals to see how the slug deforms during flight. Not sure if it's possible as the targets would need to withstand the blast without representing any noticeable resistance to the slug, but it would be fun to try it.

Cu tube

Laboratory of Liptakov - 26-12-2014 at 05:55

Interesting idea, option. But: the shock wave has tremendous power. At a distance of 30 cm fractured (broken) 20 mm thick oak plank. When 10 g ETN. It is my experience. Produce suitable partitions will be challenging. At a distance of 10 cm from the epicenter almost impossible. I think in amateur conditions. In expensive (equipped) laboratory is easier to use a high speed camera. I recommend using a 1 mm thick copper plate. From the Cu tube. This material is very suitable for directional charges. Annealed copper. Much better than 0.55 mm Cu. Tested. Excellent results for diameter 20-30 mm ...:cool:...LL

efp.jpg - 142kB

Fulmen - 26-12-2014 at 06:16

I know it's a long shot, and a heavy blast shield with a hole barely large enough for the projectile would be required for sure. But it would provide useful data with little investment...

[Edited on 26-12-14 by Fulmen]

Hennig Brand - 26-12-2014 at 07:56

Thanks everyone. I found a few things this morning which are informative I think.

From, "Standoff sensor antennae for munitions having explosively formed penetrators
US 5070786 A" the following can be read. I have also attached the patent.

"Those skilled in the art recognize that certain anti armor munitions employing EFP warheads, such as a Miznay-Shardin type of warhead, generally require five to six charge diameters of standoff distance from armor surfaces at the time of detonation to properly form the penetrating, molten metal jet used to defeat the armored target."

Except for the fact that EFPs don't form a jet the way conical shaped charge penetrators do, from what I understand, this seems reasonable.

Attachment: US5070786 Standoff Sensor Antennae For Munitions Having EFPs.pdf (454kB)
This file has been downloaded 554 times



I also found a nice graph in, "Chemistry of High-Energy Materials" By Thomas M. Klapötke, which shows how, unlike conical shaped charges, EFPs can be used effectively at very long standoffs (even over 100m in many cases for practical devices).

EFP & SC Penetration vs. Standoff.jpg - 61kB



The following is a copy/paste from one of the Wiki pages on shaped charges,

"Misznay-Schardin effect

As opposed to the cylinder/cone of the Munroe effect, which produces a narrow jet, the critical aspects of this weapon are a relatively large sheet of explosive, with a sturdy metal backing plate. The basic principle is that the main force of the explosion is directed away from the backing plate. The explosive wave, in general, is broader than a Munroe effect, producing a more-or-less flat wave rather than a jet.

If objects of considerable mass, but still less dense that the backing plate, are in front of the "open" side of the explosive, they will be propelled forward by the expanding shock wave. This is the principle in the U.S. M18A1 Claymore mine, which is a book-sized device, with a mildly concave backing plate, a sheet of explosive over it, and metal fragments on the surface of the explosive. Detonating the charge sends a fan-shaped blast and fragmentation pattern in the direction of the target.

Since the wave is straight or diverging, there is no critical standoff requirement as with the converging Munroe effect."

Well, I definitely didn't have a "sturdy metal backing plate", hell that wooden disc/bushing I was using to plug the end of the charge and align the blasting cap wasn't even glued in place. Also notice that there is not nearly the same need for precise control of standoff distance with an EFP, at least once a bare minimum is obtained.


Here is something interesting regarding the effects of casing thickness of cylindrical EFP charges on performance, taken from, "Explosive Effects and Applications", edited by Jonas A. Zukas, William Walters, William P. Walters.

Effect of Casing Thickness on EFP Performance.jpg - 68kB


[Edited on 26-12-2014 by Hennig Brand]

counterweight

Laboratory of Liptakov - 26-12-2014 at 11:38

It occurred to me to use less plasticizer. Around 5-10% only. For ETN (PETN) can be pressed. In the solid pipe. Copper or steel pipe. I estimate the pressure of 300 kg (20 mm dia). With hardwood logs. Further: Other explosives could make a counterweight. (green in the pic.) It may be less efficient. Around 3-4000mps. It's just a suggestion.

efp.jpg - 12kB

Hennig Brand - 26-12-2014 at 12:13

Yeah, that was one of my next moves. I was going to try only 5% inerts, which should be fine since the explosive doesn't have to be a mouldable plastic explosive like Semtex. I noticed that Markx uses a very small amount of inerts for his shaped charge tests also. I may try casting some ETN:TNT tetrolite into one as well.

Examining the standoff issue a little more. The following jpg image is of a page from, "Explosive Effects and Applications", edited by Jonas A. Zukas, William Walters, William P. Walters. It looks as though full slug formation happens in about 100 microseconds. If we assume a slug velocity of 1500m/s that would mean that the slug is fully formed in 15cm (if I did that right). Yeah, a little more standoff than the 10cm I used probably wouldn't hurt.


EFP Slug Formation With Respect To Time.jpg - 82kB


[Edited on 26-12-2014 by Hennig Brand]

markx - 27-12-2014 at 05:54

Ah, yes....good to see the thread awaken again. And also delighted to see someone trying out the things I've been lacking time for lately :)
I see from the EFP test pictures of Hennig that the standoff is likely too small...seems that the coin hit the witness plate flat on without having time to form into a more ergonomic projectile. I guess there is ample room for experimentation with the standoff. I would be very surprised if the optimum lies in the the range of 10 CD with such small designs. It may hold true to bigger charges, but since the forces at play do not scale well I'm more inclined to thinking that the optimum may lie well beyond the 10 CD limit here....
Waiting with great anticipation :)

Hennig Brand - 27-12-2014 at 06:36

I think you and VladimirLem, LL, and Fulmen are most likely right. Your point about things not scaling well could be more true than I originally thought. I don't imagine that 50cm would be needed, but I might try doubling it and going with 20cm for the next test. Also, according to the "Explosive Effects and Applications" and others, slug formation would be faster and more complete, and slug velocity would be higher, with a strong dense casing. A steel back plate and casing is really the way to go, but I would prefer not to go that route for safety reasons. A test could be performed though, if steps were taken to ensure safety.

markx - 27-12-2014 at 06:50

Quote: Originally posted by Hennig Brand  
I think you and VladimirLem, LL, and Fulmen are most likely right. Your point about things not scaling well could be more true than I originally thought. I don't imagine that 50cm would be needed, but I might try doubling it and going with 20cm for the next test. Also, according to the "Explosive Effects and Applications" and others, slug formation would be faster and more complete, and slug velocity would be higher, with a strong dense casing. A steel back plate and casing is really the way to go, but I would prefer not to go that route for safety reasons. A test could be performed though, if steps were taken to ensure safety.


True that, I too would keep the upgrades on confinement as a last resort if all else has failed, but judging from how well small shaped charges of mine have worked with harmless plastic cases I foresee no immediate need to escalate into the ever so dangerous metallic confinement. Keeping a thick steel back plate propelled by HE from not inflicting terrible collateral is a serious task and if ever attempted, should deserve full attention and commitment on the side of safety precautions.

Hennig Brand - 27-12-2014 at 07:20

It seems from reading that a sturdy casing, in particular a sturdy dense back plate, is much more important in the case of EFPs. From the wiki quote above,

"As opposed to the cylinder/cone of the Munroe effect, which produces a narrow jet, the critical aspects of this weapon are a relatively large sheet of explosive, with a sturdy metal backing plate. The basic principle is that the main force of the explosion is directed away from the backing plate. The explosive wave, in general, is broader than a Munroe effect, producing a more-or-less flat wave rather than a jet."

This doesn't mean that reasonable results can't be obtained with more user friendly casing materials however.

Microtek - 27-12-2014 at 08:48

Always beware of taking Wikipedia quotes too literally, even at the best of times. Even people who should be knowledgeable about explosives and related matters so often perpetuate the erroneous myths around shaped charges ("jet is liquid", "jet melts the target", etc.).

Hennig Brand - 27-12-2014 at 10:32

Good advice, and patents the same way. Was there anything in particular that stood out as being in error in the particular section quoted? I think the patent I posted is definitely inaccurate on at least a couple of points. Both Wikipedia articles and patents generally have a lot of fairly accurate information, but there can be found a lot of errors in both from time to time.

Wikipedia is not the most high quality reference, but it is often a good starting point. The Wiki articles often have good references in them as well.

More tests to follow, just drying some ETN at the moment.


[Edited on 27-12-2014 by Hennig Brand]

plate

Laboratory of Liptakov - 27-12-2014 at 10:53

This is it, what I wrote. When the diameter 1.8 cm, will cause strong nuclear forces and constraints. The test must be done in a polystyrene box. Buried in the sand. Especially, if will be use supporting plate. Maybe 2cm thick the lead plate?...:)..LL

Hennig Brand - 27-12-2014 at 14:06

Interesting idea you have there, LL.

Found another picture which would indicate that more standoff is definitely needed for proper slug formation. This one comes from the "USAF Research Laboratory". It may be hard to get a definitive answer it seems.

So for 400 microseconds and an assumed 1500m/s:

Distance required for proper slug formation = 0.0004s * 1500m/s * 100cm/m = 60cm

Well hell, I might as well try 50cm or more standoff; except for a little more difficulty in aiming the device this is still very close range for this type of shaped charge.

EFP Formation.jpg - 11kB

pit

Laboratory of Liptakov - 27-12-2014 at 15:00

My opinion, I prefer a bit more. Maybe 80 cm. Still, it must be in the sand. Or in the snow. Snow is nonsense. It must be a pit 90x30cm. Depth 40-50 cm....LL

efp.jpg - 32kB

Hennig Brand - 28-12-2014 at 06:26

Found something very interesting in, "Fundamentals of Shaped Charges", by Walters and Zukas.

"In general, the hole volume remains approximately constant for various shaped charges of the same diameter and at a given standoff. For example, for shaped charges of various liner materials and various wall thicknesses, the penetration depth varies, but the hole diameter also varies such that the hole volume is practically unchanged (Klamer 1964). This is because the hole volume varies directly with specific explosive energy. Thus, for a fixed explosive energy, the hole volume is fixed, and the hole depth times the hole area remains approximately constant.

Further, Held (1976) observed that the hole volume remains approximately constant for a variety of explosive devices. In figure 10, several conventional high explosive charges are compared with respect to standoffs, penetration depths, and crater diameters, all expressed in calibers."

It is a trade-off between hole depth and hole width, since hole volume remains fairly constant, so it really just depends on what one is trying to achieve.

Attached below is the associated table taken from the text. The 0.19D^3 value for volume, in the table, is particular to those sets of experiments and is not a universal constant.


Comparison of Conventional High Explosive Charges.jpg - 132kB


[Edited on 28-12-2014 by Hennig Brand]

greenlight - 28-12-2014 at 08:55

I had my first attempt at an EFP charge today using Hennig brands coin method of forming a liner from a coin in a vice with a ball hammer. I used an Australian 20 cent piece which are 2.85cm in diameter and 2.5mm thick and are 75% Copper which is a good liner material the remaining 25% being Nickel.
The charge casing was a 4 cm long tough cardboard tube with 2.85cm internal diameter and 3.2mm outside diameter.
The actual charge was 25 grams of hand pressed PETN and the target was a 1/4 inch steel girder/plate offcut from a building site.
The standoff used was 50cm which I realize now is probably much too short.
The plate was only badly dented/dimpled where it was hit. The dimple is 3.5mm deep and 2 cm in diameter which leads me to believe that the standoff wasn't far enough as it seems the coin has inverted but only partially formed a slug as the dent diameter is only .85cm smaller than the original coin size (second picture).
I think I will double the standoff distance next time and use the same plate to see how much of a difference I get and whether it will penetrate the whole plate thickness.
Would Pentolite be better suited for a charge like this or should I stick with the straight PETN?


[Edited on 28-12-2014 by greenlight]

IMG_20141228_182522.jpg - 1.2MB

[Edited on 28-12-2014 by greenlight]

[Edited on 28-12-2014 by greenlight]

IMG_20141228_192140.jpg - 863kB

[Edited on 28-12-2014 by greenlight]

EFP

Laboratory of Liptakov - 28-12-2014 at 10:00

Liner 2.5 fat? 28mm diameter? This is wrong. Thickness should be 28,5x 0.0146 = 0.41 mm thick Cu liner. Maybe one millimeter. Maximum. The slug will not shape. 2.5 mm is too much. It is a waste of PETN. That there could be a steel matrix. Or stone. This is not EFP. In one book is described liner for diameter 68 mm. Copper is 1.8 to 2.2 mm thick. Here is a modified scheme...:cool:...LL For dia. 28,5x0,57 is target thick 16mm. 75%= 12mm steel through. For dia. 18mm x 75% = 8mm tuti durch in durch.

dent plate2.jpg - 104kB

[Edited on 28-12-2014 by Laboratory of Liptakov]

Hennig Brand - 28-12-2014 at 10:22

Straight PETN, of the same density, would accelerate the metal more for a given charge weight, but it is much more difficult to work with because it must be pressed which can be difficult to do properly, especially for the amateur, requiring more equipment and skill. The Gurney velocity of cast 50/50 pentolite is reasonably close to midway between that of TNT (1.63g/cc) and PETN (1.76g/cc). The Gurney velocity value quantifies how effective a particular explosive is at accelerating metal (thanks go to Dany for explaining this to me). Pentolite is an extremely convenient material for shaped charge filling, however, allowing maximum densities and great uniformity to be achieved with relative ease.

If your charge was only hand pressed, the density would be quite low producing much lower performance than if it was well pressed using some sort of mechanical advantage or machine.

The thickness of your liner seems high too, but I need to do a little research to know for sure. Soft steel is, by the way, a fairly good liner material; not quite up to copper, but still quite good.

edit:
Here is a patent which specifies liner thicknesses of 5-10% of the charge diameter. Perhaps your liner isn't too thick after all.

Attachment: Explosive Charge Construction (EFP) US3217647.pdf (443kB)
This file has been downloaded 621 times


[Edited on 28-12-2014 by Hennig Brand]

US 3 217 647

Laboratory of Liptakov - 28-12-2014 at 14:30

Patent from Thomanek US 3 217 647
It is very interesting. He says something else. Liner thick 5% from diameter. The bow depth 10 to 30% from diameter. Therefore 20%. For diameter 28 mm is depth = 5.6 mm. And thick liner = 1.4 mm. I enclose a picture of a patent.

US3217647-0.jpg - 161kB

Hennig Brand - 28-12-2014 at 16:40

The patent specified 5-10% of the diameter for the thickness, so Greenlight was a little below the upper limit, but really at the scale he was working at it probably is too thick. The optimal platter thickness really has a lot to do with how thick and how powerful the layer of explosive is as well. The hand pressed (low density) PETN is the biggest problem I would say.

Good point LL, I just measured one of my bent dimes with the depth gauge on a Vernier Caliper and the bow depth was about 11% of the diameter, so it is at the lower end of the 10-30% range. I guess I could give them a little more curve then.

greenlight - 28-12-2014 at 17:27

Thanks for the info guys, should I keep the coin the same thickness and put a larger thicker charge behind it using better a explosive composition or should I try to mill the coin thickness down to something like LL stated (1.4mm).

Would I get better results using a thicker more powerful charge of pentolite or is it not worth it?




[Edited on 29-12-2014 by greenlight]

lens liner

Laboratory of Liptakov - 29-12-2014 at 04:40

It should be observed tolerance. For further experiments I recommend 20 mm diameter and 1 mm thick sheet. Copper or soft steel. Steel suggest anneal red glow. Then processed into the shape of the lens depth 4 mm. And then again anneal when steel will be used. Best to use a cast ETN. Height cylinder EM= 12 - 20mm. For PETN: Press on the highest possible density. With 5% plastificator. Cylinder height maximum 20mm.
LL

pressing

Laboratory of Liptakov - 29-12-2014 at 11:41


To be a good result, it is necessary to use a steel tools production liner and the same steel tools for stamping. The pipe may be thick plastic. Pressing connect liner, pipe and EM. For D = 20 mm estimate the pressing pressure of 3 tons. D x 0,6 for cilinder is minimal. I thing...:cool:...LL





efp lis.jpg - 41kB

[Edited on 29-12-2014 by Laboratory of Liptakov]

liner EFP

Laboratory of Liptakov - 30-12-2014 at 11:25

This post is designed especially for today's youth. Only by using hand drills can produce tools for making the liner. Without a lathe. The image is a 1000 words. The diameter is 22 mm liner from 1 mm Cu. Or 1 mm mild steel. It's all work for one afternoon. Any questions?...:cool:...LL

EFP1.jpg - 191kB

EFP2.jpg - 265kB

EFP3.jpg - 87kB

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