Most of the jet formed moves at hypersonic speed. The tip moves at 7 to 14 km/s, the jet tail at a lower velocity (1 to 3 km/s), and the slug at a still lower velocity (less than 1 km/s). The exact velocities are dependent on the charge’s configuration and confinement, explosive type, materials used, and the explosive-initiation mode. At typical velocities, the penetration process generates such enormous pressures that it may be considered hydrodynamic; to a good approximation, the jet and armor may be treated as incompressible fluids, with their material strengths ignored.
Wikipedia, Shaped charge
Emphasis added.
Found while Wikiwandering from a link at Roberta’s.
[“… may be treated as incompressible fluids, with their material strengths ignored”! That statement makes me light-headed and weak at the knees. The “7 to 14 km/s” doesn’t hurt either.
7 km/s is about 23,000 feet per second. Your .220 Swift is considered a very zippy cartridge but it only gives you about 4,100 feet per second at the muzzle. Hence a shaped charge gives you velocities 5 to 10 times that of a .220 Swift at the muzzle. This is considered high-hypersonic to re-entry speeds.
I have books on computer simulation of shaped charges. I really need to write the software then do some field testing. Supposedly it is pretty easy to punch through three feet of reinforced concrete. I have some large rocks out in the middle of some fields I’d like to experiment with.—Joe]
Shaped charges are cool, and simple ones are easy to make.
If you want to simulate explosions, LS-DYNA is your tool (http://en.wikipedia.org/wiki/LS-DYNA).
As always… Call me when you do. (Note I didn’t say if, I know better.)
MadRocketScientist,
How do I obtain LS-DYNA? I poked around some but didn’t see either sales information or free download.
Looks like there is a demo license – http://ls-dynademo.com/
http://www.lstc.com/limited.htm
examples
http://www.dynaexamples.com/
Copper makes really good EFP’s. Steel not so much, there seems to be of some sort ideal malleability and density that makes copper a good EFP.
Any angle up to 45 degrees will work as well for the shaped charge. For anti tank missiles we use a very shallow angle, probably 20 degrees (didn’t check last time I had access to a mockup warhead).
The variations in cone angles are to do with whether/how much the warhead is rotating at time of detonation. Non-rotating, fin-stabilized, projectiles are used in preference by designers because rotation disrupts the forming of the slug. The shallower cones are used in rotating projectiles.
Here a shaped charge animation that I found on the web: