Shaped charge
Different types of shaped charges are used for various purposes such as cutting and forming metal, initiating nuclear weapons, penetrating armor, or perforating wells in the oil and gas industry.
[5] The first true hollow charge effect was achieved in 1883, by Max von Foerster (1845–1905),[6] chief of the nitrocellulose factory of Wolff & Co. in Walsrode, Germany.
[7][8] By 1886, Gustav Bloem of Düsseldorf, Germany, had filed U.S. patent 342,423 for hemispherical cavity metal detonators to concentrate the effect of the explosion in an axial direction.
When a hollow charge of dynamite nine pounds and a half in weight and untamped was detonated on it, a hole three inches in diameter was blown clear through the wall ...
In 1910, Egon Neumann of Germany discovered that a block of TNT, which would normally dent a steel plate, punched a hole through it if the explosive had a conical indentation.
In 1932 Franz Rudolf Thomanek, a student of physics at Vienna's Technische Hochschule, conceived an anti-tank round that was based on the hollow charge effect.
When the Austrian government showed no interest in pursuing the idea, Thomanek moved to Berlin's Technische Hochschule, where he continued his studies under the ballistics expert Carl Julius Cranz.
[24]) Meanwhile, Henry Hans Mohaupt, a chemical engineer in Switzerland, had independently developed a shaped-charge munition in 1935, which was demonstrated to the Swiss, French, British, and U.S.
HEAT warheads are frequently used in anti-tank guided missiles, unguided rockets, gun-fired projectiles (both spun (spin stabilized) and unspun), rifle grenades, land mines, bomblets, torpedoes, and various other weapons.
Since the charges were less effective at larger standoffs, side and turret skirts (known as Schürzen) fitted to some German tanks to protect against ordinary anti-tank rifles[32] were fortuitously found to give the jet room to disperse and hence also reduce HEAT penetration.
In such cases, the skirting effectively increases the distance between the armor and the target, and the warhead detonates closer to its optimum standoff.
In non-military applications shaped charges are used in explosive demolition of buildings and structures, in particular for cutting through metal piles, columns and beams[34][35][36] and for boring holes.
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 inviscid, compressible fluids (see, for example,[41]), with their material strengths ignored.
[44] In comparison, two-color radiometry measurements from the late 1970s indicate lower temperatures for various shaped-charge liner material, cone construction and type of explosive filler.
[45] A Comp-B loaded shaped charge with a copper liner and pointed cone apex had a jet tip temperature ranging from 668 K to 863 K over a five shot sampling.
Nearly every common metallic element has been tried, including aluminum, tungsten, tantalum, depleted uranium, lead, tin, cadmium, cobalt, magnesium, titanium, zinc, zirconium, molybdenum, beryllium, nickel, silver, and even gold and platinum.
[49] For the deepest penetrations, pure metals yield the best results, because they display the greatest ductility, which delays the breakup of the jet into particles as it stretches.
In the petroleum industry, therefore, liners are generally fabricated by powder metallurgy, often of pseudo-alloys which, if unsintered, yield jets that are composed mainly of dispersed fine metal particles.
Some explosives incorporate powdered aluminum to increase their blast and detonation temperature, but this addition generally results in decreased performance of the shaped charge.
In an ordinary charge, the explosive near the base of the cone is so thin that it is unable to accelerate the adjacent liner to sufficient velocity to form an effective jet.
"At detonation, the focusing of the explosive high pressure wave as it becomes incident to the side wall causes the metal liner of the LSC to collapse–creating the cutting force.
LSCs are commonly used in the cutting of rolled steel joists (RSJ) and other structural targets, such as in the controlled demolition of buildings.
More modern EFP warhead versions, through the use of advanced initiation modes, can also produce long-rods (stretched slugs), multi-slugs and finned rod/slug projectiles.
The long-rods are able to penetrate a much greater depth of armor, at some loss to BAE, multi-slugs are better at defeating light or area targets and the finned projectiles are much more accurate.
It is well suited for the attack of other less heavily protected armored fighting vehicles (AFV) and in the breaching of material targets (buildings, bunkers, bridge supports, etc.).
TOW-2A was the first to use tandem warheads in the mid-1980s, an aspect of the weapon which the US Army had to reveal under news media and Congressional pressure resulting from the concern that NATO antitank missiles were ineffective against Soviet tanks that were fitted with the new ERA boxes.
In 1964 a Soviet scientist proposed that a shaped charge originally developed for piercing thick steel armor be adapted to the task of accelerating shock waves.
When the shaped charge detonates, most of its energy is focused on the steel plate, driving it forward and pushing the test gas ahead of it.
[70][71] A further extension of this technology is the explosive diamond anvil cell,[72][73][74][75] utilizing multiple opposed shaped-charge jets projected at a single steel encapsulated fuel,[76] such as hydrogen.
The fuels used in these devices, along with the secondary combustion reactions and long blast impulse, produce similar conditions to those encountered in fuel-air and thermobaric explosives.
