Shape Charge Penetration (Taking into account properties other than density)

[MKSheppard]

Okay, we all know the traditional shape charge penetration formulae; given as:

 

 

where:

 

t = Penetration of Shaped Charge

L = Length of Jet

Pj = Density of Jet Material

Pt = Density of target material.

 

It's simple; and works in a narrow range, but when you use it against non-traditional materials it really doesn't work.

 

Good example from GS.org's site:

 

Demolition Shaped Charge

 

The Charge, Demolition, Shaped, 150mm is designed to make holes of considerable depth and breadth in a variety of materials. It consists of a 150mm diameter conical steel liner with three removable legs which provide a standoff of 145mm.

 

178mm Penetration (RHA)

250mm Penetration (Mild Steel)

380mm Penetration (Granite)

760mm Penetration (Reinforced Concrete)

910mm Penetration (Sandstone)

 

But when we do it using the classical equation; using the RHA penetration to calibrate everything; to get a jet length of 178mm, and then do it using the conventional densities of the following materials:

 

178mm Penetration (RHA)

178mm Penetration (Mild Steel)

300.9mm Penetration (Granite)

322.13mm Penetration (Reinforced Concrete)

329mm Penetration (Sandstone)

 

Also, when we use it against traditional anti-HEAT stuff, like the various ceramics, we get absurd ratings:

 

263mm Penetration Alumina AD-90

235mm Penetration Titanium Diboride

 

Which means that effectively, you're probably better off using conventional steels.

 

I've been banging around trying to discover a formula which would work and take into account the differences between a lot of stuff; I tried looking into melting point, specific heats, etc; and then I finally hit upon it.

 

Compressive Yield Strength...and I began to look around.

 

I then looked around and began hammering away before I tried something a bit out of the ordinary

 

"What if I Just modified the traditional equation?"

 

 

Yj = Compressive Yield of Jet Material

Yt = Compressive Yield of Target Material

 

I then tried it out:

 

178mm Penetration (RHA 1,100 MPa)

274.3mm Penetration (Mild Steel 463 MPa)

343.5mm Penetration (Granite 844 MPa)

755.45mm Penetration (Reinforced Concrete 200 MPa)

1091.35mm Penetration (Sandstone 100 MPa)

 

It *appears* to work.

 

And when we toss it against Ceramics; it shows them resisting quite well

 

171.08mm Penetration Alumina AD-90 (2600 MPa)

183.9mm Penetration Titanium Diboride (1800 MPa)

 

Comments? Sharp Sticks? Howling mobs ready to tear me from limb to limb for violating science and math?

[MKSheppard]

Some interesting information on DU penetrator material:

 

European Patent Application

Application Number 92304960.5

Date of Filing 5/29/1992

 

Seems the average for DU penetrator yield strength in the 80s was around 100+ KSI; and their new method managed to raise it to 200 ksi.

[MKSheppard]

Found this in a book on Tactical Missile Warheads:

 

The DART warhead technology was evaluated in several series of comparison Firings against up-armored T26-E5 tank targets at the Aberdeen Proving Ground. DART was demonstrated to be superior in terms of the behind-armor side effects (i.e.. exit hole diameter, quantity and spread of spall, high overpressure and thermal effects, blinding light, etc.) of a fuel-air explosion from combustion of the aluminum jet. However, the penetration, although amply meeting requirements, was 2/3 that obtained with an equal-diameter copper-lined shaped charge that produced a small-diameter but much deeper penetration hole but only modest behind-armor effects as compared to the aluminum lined charge. The result was the Army's rejection of DART's advanced techniques in favor of the more conventional point-initiated, copper conical lined, shaped charge, typical of all subsequent U.S. Army-developed ATGM and rocket warheads, including the SHILLELAGH, DRAGON, and TOW ATGMs, as well as the shoulder-fired successors to the 2.36-in. and 3.5-in. M-28 bazookas, the rocket-propelled grenades (RPGs) M72 LAW (early 1950s) and VIPER (mid 1970s).

[Przezdzieblo]

Some excerpts about "Dart", taken from report of some HEAT trials:

 

- The American evaluation of the "Dart" varhead showed the weapon to be very effective against a T26E4 tank. Blast pressures of 50 lb./sq, in. in the turret, and 30 lb./sq. in. in the driver's compartment were recorded. 'Wooden dummies (boxes of 3/4" pine) were thrown against the turret m.lls by the blast, but also showed fragment penetration. These dummies were therefore placed within the fragment cone, where men are likely to be killed or seriously injured.

 

- In terms of crew damage there is for "Dart" a roughly conical lethal zone (w ith a cone angle of about 30 degrees) centred around the jet path; the depth of the cone is determined by the material encountered, but in general it extends well into the crew compartnent. The lethality is due both to fragment concentrations and to thermal effects. Outside this zone, only slight crew damage (caused by isolated fragments or Ist degree burning) may be expected; no crew damage should result from the accelerations, flash is unlikely to impair crew vision and blast (although sufficient to force off the closed turret hatches) is not considered to

 

- Blast pressures, Thermal effects (burns), Light intensities (blinding effects) caused largely by vaporific afterburnng of the aluminium cone inside the crew compartments.

 

- ...the overmatch obtained from a copper liner is a far more serious hazard to the tank than any vaporific effects likely to be obtained from using aluminium

 

- It seems clear that, with "Dart" thermal effects are of importance only in the region already rendered lethal or hazardous by fragments.

 

- The accelerations to dumy crew in the gunner's and driver's positions (...) are likely to cause minor injury only to a human crew (...) the actual degree of incapacitation remains an open question.

 

- The measured blast pressures are unlikely to cause serious injury to crew members of a heavy tank who are outside the lethal zone of the jet.

 

- The intensity of the internal flash - would cause no injury by day and only loss of dark adaptation at night.

 

Edited February 1, 2008 by Przezdzieblo

[Przezdzieblo]

The only time value I found (tests of Dart vs Conqueror) is 0,001-0,002 s, overpressure not more than 22 lb./sq.in., with adnotation, that probably for severe lungs dammage would be needed at least 70 lb./sq.in. Although blast was enough to rupture eardrums of "animal crew" (small, white, sweet rabbits ).