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ZoSo357
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I was thinking, with shaped charges, is there an angle which the cone should be that has the highest possible penetration? Inline with the munroe
effect, the direction of the surface of the explosive, is the direction that the force will travel. Having said that, say something with too small of
an angle was used, would a lot of the energy near the "peak" of the cone be wasted on the inside of the charge itself?
I have included a diagram to help explain better. Basically what is happening here, is the red lines show the direction of the cone's movement. (yes,
MS paint diagram )I tried to show that if you were using a 90 degree angle cone, it
would work well, where as using, say a 45 degree, or something like a 150 degree angle cone, you may be losing a lot of the penetrating power since
the peak of the cone will be just "sandwiching" in on itself. In the case of using cones, would a 90 degree angle be most efficient for penetration?
[Edited on 17-1-2006 by ZoSo357]
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Quince
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Just run a FEM simulation and see for yourself. There are plenty of tools that make it easy for you, like Fastflo and stuff.
[Edited on 18-1-2006 by Quince]
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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Axt
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Its a trade off between jet velocity, mass, length and stretch.
Typically the smaller the angle the faster the jet with lower mass percentage of liner in the jet (the majority of the liner doesnt form a jet at all
rather a low velocity "carrot"). Also, for example in a 40° cone will weigh more and contact the explosive over a greater area then in a 90° cone.
Typically somewhere between 40-60° angle is used.
Its only the skinny spike at the front that penetrates, the black lump at the back is the "carrot".
<center><img src="http://www.sciencemadness.org/scipics/axt/liner angles.jpg"></center>
[Edited on 18-1-2006 by Axt]
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nitro-genes
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About angels... I just tried a 15 mm shaped charge with a 0,4 mm, 60 deg. copper liner. The liner was made from 2 layers of 0.2 mm coppersheet like
boomer did. (Hopefully you didn't patented it yet  )
And although the use of copper made the charge fully penetrate the 1" steel plate, the entrance hole is a mess... (Because coppersheet is realy
expensive I always used aluminium sheet) You can see small dimples in the steel surrounding the entrance everywhere.
My question thus is, if a decrease in the liner angle would make the demands in symmetry of the liner less than when you use a larger liner angle. In
other words, would the jet form more easily at, say 40 deg. then at 60 deg.? Coudn't find any evidence for this, it is just a feeling so to say. 
I used Petn/Pib plastique which is quite stiff, so I had to really mash it to get it in the smaller spaces of the charge. So that surely didn't
help...
Petn/NG is an option, but I have very little information about sensitivity, stability and "how it handles" I've heared about 50/50 compositions that
form a viscous liquid that can be poured if one wants to... But than again what about low-order detonation?
[Edited on 19-1-2006 by nitro-genes]
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Quince
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Is blasting gelatine suitable for shaped charges? I don't have any PETN.
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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Chris The Great
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I would imagine it would work decently for larger charges. Nitroglycerin isn't as easy to detonate like PETN so you will need a powerful cap and good
charge diameter. Probably be best to use a methyl nitrate gelatine, since methyl nitrate is a high brisance explosive and also very easy to detonate
like PETN. Or at least use EGDN... nitroglycerin isn't that brisant of an explosive and EGDN would be a good improvement. Methyl nitrate would be
best, but raises some challenges with handling.
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Axt
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| Quote: | Originally posted by nitro-genes
Petn/NG is an option, but I have very little information about sensitivity, stability and "how it handles" |
I've never had problems with PETN/NG which should be no more unstable then its parent compounds. I've never weighed the quantities, simply drip NG
into it until it forms a soft plastic consistancy.
| Quote: | Originally posted by Chris The Great
Probably be best to use a methyl nitrate gelatine. |
I'm not so sure methyl nitrate would do any better, since the susceptability to LVD is largely dependent on viscosity, increasing MN's viscosity with
NC to that of blasting gelatin would likely make it just as prone to LVD.
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Coolio
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I made twice times ANNMSA
At first the AN SA mixture geht really hard, after also poored the NM into it, it stayed hard....
then ein crushed this and mixed it very "brutaly"
but it was very liquid, and on the surface there were just liquid NMSA....
wtf do i wrong ??
*sorry for my bad english, I am from Austria  *
@ axt, have you got an icq nummber ?
it would be an honor for me to be able to write with you about your recent "breakthroughs"
[Edited on 19-1-2006 by Coolio]
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Chris The Great
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As far as I know, methyl nitrate does not LVD easily. A #1 blasting cap gives 520 in the lead block compared to 615 with a #8. As far as I know
those values are uncorrected for the cap size so that would move them even closer.
The idea with the gelatine is because methyl nitrate has a VERY low viscoisity, and it would leak out of the charge I gelled a some of it and it is very thick, and so it would stay put after you put
it in the shaped charge. 9% nitrocellulose seems to be a bit too much in my opinion, a bit less might make it easier to get into the charge evenly.
Since methyl nitrate has a fair 240% of TNT by the plate cutting test, I imagine it would have good performance in a shaped charge.
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nitro-genes
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| Quote: | Originally posted by Chris The Great
As far as I know, methyl nitrate does not LVD easily. A #1 blasting cap gives 520 in the lead block compared to 615 with a #8. As far as I know
those values are uncorrected for the cap size so that would move them even closer. |
Pure methylnitrate has a very low viscosity, much lower than NG. That is exactly why methylnitrate is less susceptable for LVD in the lead block
tests! The low viscosity allows for a better shockwave propagation and thus a
higher DV. Unfortunately, that doesn't change anything about the fact that increasing the viscosity of methylnitrate will make it more sensitive to
LVD...
[Edited on 20-1-2006 by nitro-genes]
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PHILOU Zrealone
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| Quote: | Originally posted by Coolio
I made twice times ANNMSA
At first the AN SA mixture geht really hard, after also poored the NM into it, it stayed hard....
then ein crushed this and mixed it very "brutaly"
but it was very liquid, and on the surface there were just liquid NMSA....
wtf do i wrong ??
[Edited on 19-1-2006 by Coolio] |
Mix SA with ANNM and not NM with ANSA!!!!
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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PHILOU Zrealone
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| Quote: | Originally posted by Chris The Great
As far as I know, methyl nitrate does not LVD easily. A #1 blasting cap gives 520 in the lead block compared to 615 with a #8. As far as I know
those values are uncorrected for the cap size so that would move them even closer.
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As far as I know lead block test is:
Volume of of deformation due to the detonation/explosion of 10g of explosive with a given detonator (V total) minus the volume produced by the
detonation of detonator itself (V detonator)
V total - V detonator = V lead block test
So there is a correction factor!
Maybe it is not linear!
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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Axt
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Umm. yep, Chris you read <i>"I'm not so sure methyl nitrate would do any better"</i> but not <i>"increasing MN's viscosity with NC
to that of blasting gelatin would likely make it just as prone to LVD"</i>. This is only speculation but I cant see the point choosing a low
viscosity liquid to prevent LVD if your only going to increase the viscosity by gelling it.
As to the ANNMSA, this was covered before in this thread, you have to add NM to ANSA or one ends up a solid covered by a thick layer of liquid.
Coolio, if your just pour the NM in and leave it, it will form a granite hard solid, it must be <b>stirred</b> in prefereably while
<b>hot</b> to create the precipitation of AN/AS in the crystalline form that best holds onto all the liquid. It sounds like you cooled it
down making the AN/AS precipitate prematurely.
[Edited on 20-1-2006 by Axt]
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Fulmen
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Getting back to the subject of sylindrical liners, I was wondering if the liner should be sealed at the top or not, and if so, what the shape should
be. If left open, wouldn't the gasses from the explosion fill the liner and possibly disturb the formation og the jet?
BTW, any suggestions on how the following charge should perform:
Container: 62mm diameter, 90mm high
Liner: Copper tube 22mm diameter, 60mm high, 1mm thick walls
Charge: appr. 250g NMANXY (kinepak)
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Deceitful_Frank
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By the sound of it you are using a composition very similar to the one that I use. An excellent explosive, albeit not a very dence one... check out my
thread on plate dent testing as I'm sure you'll find it of interest
As for this cylindrical lined charge, I think you could do with using a slightly taller casing and maybe 16mm copper tubing, though staying with what
you have, if I were you I'd give it more comparatibe head height by reducing the length of your copper tube to around 45mm.
I have calculated the filling space inside your vessel (obviously minus the cavity) to be 237ml using your tube and reducing the length to my
suggested 45mm.
I am still in the process of finding out if this 80:16:4 kinepak performs best at 1.0, 1.05 or 1.1g/cm3 but I think if you go with 1.05 and 249 grams
pressed evenly with the back of a spoon then you wont be dissappointed. I would either find or sandwich together 30mm of steel plate, use a standoff
of just the one diameter or about 60mm and initiate with a full gram of fresh HMTD or the equivalent
Dont forget to keep us posted as I'd be very intersted to learn of your results!
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Fulmen
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I thought the "1 diameter" was based on the liner diameter, so 60mm would be nearly 3x. Sounds a bit much for a homemade charge, don't you think?
Regarding the performance, 30mm??? That's nothing, I pierced 15mm with a 7.62Nato jacket and 3,5g RDX. Sure kinepak is a lot weaker, but come on!
Anything less than three inches is a failure in my book :-)
As for head height you might be right, the problem is that the liner is already glued to the container. Not sure if it's worth the trouble of removing
it without destroying everything. Maybe I can increase the height of the charge somewhat instead.
How much does initiation influence the performance? I was thinking of a regular blasting cap, but I might spend a gram of RDX or two if it makes any
real difference...
We're not banging rocks together here. We know how to put a man back together.
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Deceitful_Frank
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Hee hee! you are right about the standoff! It has been a long day and I'd forgotten whilst typing, that this isnt a conical liner. I feel that your
cylindrical liner is a little too wide for the diameter of the charge else I would have suggested an inch.. maybe one or two centimeters would work
better?
If you had NO standoff would it be at the detriment of performance due to the air in the cavity having nowhere to go?
Cylindrical lined charges are very inefficient though simple to make. If you are serious about less than three inches meaning failure then I really
wouldnt waste your time! ... I trust you WERE joking
I havent experienced obvious LVD with this composition though I do think diameter and confinement helps. It seems to either go full power or not. I
dont have access to commercial blasting caps but have a good supply of penlids that hold a gram of HMTD nicely. If you have atleast #6 caps the I
wouldnt bother with RDX as well.
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Deceitful_Frank
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Hee hee! you are right about the standoff! It has been a long day and I'd forgotten whilst typing, that this isnt a conical liner. I feel that your
cylindrical liner is a little too wide for the diameter of the charge else I would have suggested an inch.. maybe one or two centimeters would work
better?
If you had NO standoff would it be at the detriment of performance due to the air in the cavity having nowhere to go?
Cylindrical lined charges are very inefficient though simple to make. If you are serious about less than three inches meaning failure then I really
wouldnt waste your time! ... I trust you WERE joking
I havent experienced obvious LVD with this composition though I do think diameter and confinement helps. It seems to either go full power or not. I
dont have access to commercial blasting caps but have a good supply of penlids that hold a gram of HMTD nicely. If you have atleast #6 caps the I
wouldnt bother with RDX as well.
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Fulmen
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| Quote: | Originally posted by Deceitful_Frank
If you had NO standoff would it be at the detriment of performance due to the air in the cavity having nowhere to go?
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Not really sure, since the tube collapses at supersonic speeds the air will create a high-pressure front no matter what. Could be that it plays a role
as the collapse reaches the end of the tube...
| Quote: |
Cylindrical lined charges are very inefficient though simple to make. If you are serious about less than three inches meaning failure then I really
wouldnt waste your time! ... I trust you WERE joking
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Not really. If you look at the first posting by Axt you'll se that a similar charge with an aluminium liner punched a clean hole through a 1" plate.
Now, copper is said to be almost twice as efficient as aluminium, and it doesn't look like Axt's charge had any plans of giving up anytime soon. My
guess is that he could easily have penetrated another 1/2-1", so 3" doesn't sound THAT far-fetched. Or am I missing something here?
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Deceitful_Frank
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Yes, I see your point, the wider lined charge would have deffinately gone another half an inch though I doubt one inch further. 3 inches is not THAT
far fetched I suppose though ANNMSA on paper is going to be denser and more homogemous than the kinepack.
If you can give your charge 5cm more height then maybe 2 inches penetration but not three... I'd love to see you prove me wrong though
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Axt
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| Quote: | Originally posted by Fulmen
Or am I missing something here? |
I dont think its a metal jet that created those holes, in fact I suspect if there were no liner the same thing would have happened. Thats why I
suggested back a few pages to hold the charge off a couple inches, just to remove the blast effects from the target. See what the metal jet and only
the metal jet is capable of.
If it was a "hole punch" that created those holes, which I suspect it was, then it may do very little to 3" plate as its either going to go straight
through or not far at all. Alternatively it may push a small diametre hole through it, that was masked by the "hole punch" effect on the 1" plate.
Firing a charge with standoff should tell us what effect is doing what.
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Coolio
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I want to shoot throug a 6cm thick steel plate....
Do you think this is possible with annmsa an the cylindrical linder shaped method ?
which amounts of HE, length of the liner...?
[Edited on 21-1-2006 by Coolio]
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Fulmen
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Guess I'll just have to see for myself. But heck, thats half the fun anyway :-) I have placed an order for a piece of steel at least 60mm in diameter
and 4" long, this should be more than enough. The idea is to split it in half afterwards to get a little more information on just how the metal
behaves. Or should i reduce the length to 2-3" and see if I can get full penetration with spalling?
I've attached a drawing of the charge, do you think the metal cap will disturb the jet formation?
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Fulmen
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Another idea would be to use an empty CO2-cartridge as the liner. It's made from steel, but that is supposed to be a bit better than aluminium and the
hemispherical end should guarantee the formation of a jet. Also, the length of the liner gives a standoff of appr. 3 diameters so the charge should
work without any additional standoff. So even if the sylindrical part fail to produce any additional jet it should neverttheless work as a unlined
charge.
What'ya think?
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Coolio
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I think co2 cartridges are a little bit to hard,... but maybe it works with petn/rdx/hmx..
But why use co2 cartridges ? It`s not very difficult to get copper pipes...
I have an idea...i think it would be possible to use glas test tubes. They also have the same form like co2 cartriges.
It should work with HNO3/NM
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