military@att.att.com (Bill Thacker) (01/09/90)
From: military@att.att.com (Bill Thacker) Everything I've read about HEAT munitions says or implies that the copper liner, which is compressed by the shaped charge into a small-diameter penetrator, is melted in the process. On the other hand, in a conversation with someone who really should know, I was once told that this is not the case; the copper remains solid, at least until it contacts the armor. Given the time frame of the jet formation, I could believe that there'd be insufficient heat transfer to melt the copper from the heat of the explosion. More likely, I think, the tremendous deformation of the liner might melt it; and it seems likely that, if not alread molten, the copper would be liquified during penetration. Can anyone confirm or deny the molten status of the penetrator before contact with the armor ? - -- -- -- -- -- -- -- -- Bill Thacker Moderator, sci.military military-request@att.att.com (614) 860-5294 Send submissions to military@att.att.com
wilkinson@PICA.ARMY.MIL (CCL-C) (01/11/90)
From: Peter Wilkinson (CCL-C) <wilkinson@PICA.ARMY.MIL>
Ref: "The Infantryman vs The MBT", Donald R. Kennedy,
National Defense Mag., March 1985
In the referenced article, Mr. Kennedy does an excellent
job of explaining the HEAT process. Simply stated, the HEAT
armor defeat process is not a thermal one. The "molten metal"
does not "burn through" the target as so many explanations of
the phenomenon would have us believe. In fact, when a HEAT
weapon is initiated its detonation wave expands along a
sherical front at a very high velocity (typically 7-8 km/s).
Swept by the detonation wave the conical liner (typically CU)
collapses so that its inner surface hydrodynamically forms
into a hypervelocity , continually stretching, metal jet. The
jet represents only 8-12 percent of the original liner mass,
the rest forms into relatively large, low velocity fragments.
The jet does not normally take the form of a gas or molten
metal, but rather is in a highly plastic and ductile
condition, being continuously stretched as in a wire-drawing
process. Metals, such as this, worked at a high rate generate
internal heat from the rapid displacement of the molecular
structure. The velocity of the jet is highest at its tip and
typically reaches 8-9 km/s. The actual penetration process is
caused by the high energy-density of the jet (typically
millions of pounds of force per square inch of jet cross
sectional area). This creates such enormous localized over-
pressure at the target contact point that the jet can
literally push its way through virtually any known material.
The tip is continuously used up and converted into high
temperature liquid and some vapor. New jet material
continuously comes into contact at the rapidly moving working
face as the jet progresses through the target. Interestingly,
very little of the target material is lost to the penetration
process. In fact, the density of the target material
immediately surrounding the hole is increased. The
penetration process continues until one of three things
occurs: all the jet particles are consumed; the energy
remaining in the jet particles is insufficient to overcome
the target's strength; or the particles misalign and impact
the side of the hole.
Assuming complete penetration, and depending on the
remaining energy and quantity of material in the jet, a
varying amount of armor and jet material will discharge from
the interior surface of the target. The armor forms a rapidly
expanding bubble that bursts, sending high velocity (1.5-2.5
km/s) spall fragments into the crew compartment. The behind-
armor effect is akin to detonating a small grenade at the
armor's interior surface.
Thanks for the opportunity to contribute. I hope this info
is helpful.
Peter Wilkinson
U.S. Army Armament, Research,
Developement, & Engineering Center
Picatinny Arsenal, NJferguson@maitai.src.honeywell.com (Dennis Ferguson) (01/14/90)
From: ferguson@maitai.src.honeywell.com (Dennis Ferguson) In article <12930@cbnews.ATT.COM> military@att.att.com (Bill Thacker) writes: > >Everything I've read about HEAT munitions says or implies that >the copper liner, which is compressed by the shaped charge into >a small-diameter penetrator, is melted in the process. > [stuff deleted] > >Can anyone confirm or deny the molten status of the penetrator before >contact with the armor ? > The penetratror is mechanically deformed by the shaped charge and while it is obviously very hot, it is not molten. The penetrator is shaped like a shuttlecock to keep it aerodynamically stable (even for a short 'flight'). Once the penetrator hits the armor, it becomes molten. I believe there is a chemical reaction between the penetrator and the armor. I have seen the results of penetrator tests on steel blocks of various thicknesses and the hole cut by the penetrator has the look of a chemical etch process as opposed to mechanically ejecting armor material. Dennis
kelly@uts.amdahl.com (Kelly Goen) (01/17/90)
From: kelly@uts.amdahl.com (Kelly Goen) In article <13133@cbnews.ATT.COM> ferguson@maitai.src.honeywell.com (Dennis Ferguson) writes: > >In article <12930@cbnews.ATT.COM> military@att.att.com (Bill Thacker) writes: >> >>Everything I've read about HEAT munitions says or implies that >>the copper liner, which is compressed by the shaped charge into >>a small-diameter penetrator, is melted in the process. >> > [stuff deleted] >> >>Can anyone confirm or deny the molten status of the penetrator before >>contact with the armor ? >> > >The penetratror is mechanically deformed by the shaped charge and >while it is obviously very hot, it is not molten. The penetrator >is shaped like a shuttlecock to keep it aerodynamically stable (even >for a short 'flight'). Once the penetrator hits the armor, it becomes >molten. I believe there is a chemical reaction between the penetrator >and the armor. I have seen the results of penetrator tests on steel actually dennis it depends upon what material is used for the penetrator lining and what geometry is used for the so-called shaped charge.... in SCMP shaped charges the geometry and explosive used often result in a molten jet with the leading edge of the oncoming projectile being HIGH-speed metallic vapor...with the so-called COPPERHEAD geometry... the technique used is is explosive deformation of the liner materia;... in conical stand-off charges (used in structure demolition work) it is actually the HOT jet formed at the apex of the detonation wave.... Another large area of variabilty is the type and brissance of explosive propellant used...btw when project trinity was first experimenting with implosion plutonium geometries... the initial problems faces were fragmentation and fragmentation of the plutonium core without implosion taken place(read supercritical densities)...All of what I have related to you is in the public domain from NTIS sort of like LA-1... The results of explosive lense testing is unfortunately still highly classifed cheers kelly