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Explosive Applications for Industry and Defense

Speaker: Arran GordonCompany: Havoc Industries Pty Ltd

Date: 19-Oct-06

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Types of Explosives

• “Low” Explosives – Burn or deflagrate rather than detonate. Velocity of Detonation (VOD) of less than 1,000 m/s.

• “High” Explosives – Detonate as a shock wave passes through the material. VOD in the range of 4,500 to 8,000 m/s

• Blasting Agents – Bulk high explosives that are not detonator sensitive.

• Initiating Explosives – Highly sensitive.

TYPES OF EXPLOSIVES"LOW" EXPLOSIVESBurn or Deflagrate rather than DetonateProduce large volumes of gas which "explode" if confinedVOD less than 1,000 m/sExamples: Black Powder – Pyrotechnics, Smokeless Powder - Propellant for Bullets / Shells"HIGH" EXPLOSIVESDetonate as Detonation Shock Wave passes throughVOD greater than 1,000 m/s - typically 5,000 to 8,000 m/sProduce very high pressures, even when unconfinedExamples: TNT, Dynamite, Mining Explosives - Watergels, Emulsions and Slurries, ANFOBLASTING AGENTSAre High ExplosivesAre less sensitive and more difficult to initiateAre not detonator or "cap" sensitiveExamples: ANFO, Some Emulsions and SlurriesINITIATING EXPLOSIVESHigh explosives that are very sensitive to heat and shockUsed in small quantities in detonatorsExamples: Mercury Fulminate, Lead Azide, Lead StyphnateHISTORY OF EXPLOSIVESBLACK POWDER OR VARIANTS"Greek Fire" used in battle 668 AD - petroleum distillate thickened with resinsChinese references to gunpowder in 1040 AD ("Wu Ching Tsing Yao")English Friar Roger Bacon publishes gunpowder formula 1242Gunpowder used in mining operations 1650 to 1800William Bickford invents safety fuse 1831HIGH EXPLOSIVESAlchemist Blasius Valentius produces "Fulminating Gold" 15th centuryAscanio Sobrero discovers Nitroglycerine 1846-7Wilbrand invents TNT 1863Alfred Nobel develops first detonating blasting cap 1864Alfred Nobel develops Dynamite1867 / gelatin dynamite 1875ANFO rediscovered after ship explosion in Texas City 1950

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Elements of the Explosive “Train”

• Low Energy Initiating Device – in the “old days” – matches, these days – electric or shot shell primer.

• “Distance” element – “old days” – safety fuse, these days – electric cable, signal tube, radio frequency.

• Detonator – converts the “low” energy into an explosive shock wave. Can incorporate delays.

• Booster / Primer – detonator sensitive explosive to “amplify” the detonation shock wave.

• Main Charge – the bulk of the explosive device.

An “Explosive Train” is the various elements required to go from a “low” powered initiation device (typically safe to be hand held), escalating in power at each stage to provide the desired explosive result.

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Various Explosive Items

Selection of Orica Products

Photos of Orica Explosive products and accessories.

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Elements of a Shaped Charge

• All shaped charges incorporate a symmetric hollow in the base.

SHAPED CHARGE EFFECTSFirst discovered by von Förster 1883 coin and leaf impressionsCharles E. Munroe rediscovered the effect from 1888Munroe developed first lined shaped charge 1894 - tin can with dynamite tied around itWASAG / E and M Neumann in Germany 1911Shaped charge development accelerated between 1935 and 1950Franz Rudolph THOMANEK for Germany - First use-able lined SCsHenry Hans MOHAUPT for United States / United KingdomSCs used in bazooka, panzerfaust and other devices

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Effect of Liners and Stand-off

It was determined that a column of explosives that incorporates a hollow in the base did more damage than the same mass of explosives in any other configuration when placed directly against a target.The amount of damage could be further increased by lining the hollow with a high density material such as metal.If the hollow is symmetrical, the charge will produce far greater penetration if supported at a distance from the target – referred to as the stand off distance. This is because the liner is compressed into a molten “jet” of material.

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Unlined Focused Charge / 20 mm Plate

SETUP ENTRY HOLE EXIT HOLE

An unlined focused charge is placed directly against 20 mm thick plate. The imprint of the base of the charge can be seen around the entry hole, the plate has been bent and “spalled” on the underside. This illustrates the damage expected due to a hollow, unlined charge.

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How Lined Focused Charges Work

• The detonation pressure collapses the surfaces of the liner together.

• The liner material behaves as a liquid and is projected from the front of the charge at high velocity.

• A slower moving “slug” is also projected from the charge.

The high velocity jet will penetrate large thicknesses of material. The slower moving slug can then block the hole formed by the jet. This is a problem when shaped charges are used to “drill” a hole that is then filled with explosives for demolition work (underwater or thick, reinforced concrete).

A hemispherical shaped charge produces a slower moving jet but is unlikely to produce a “slug”.

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Point Focal Charge / 65 mm Plate

SETUP ENTRY HOLE EXIT HOLE

The white tube provides the required stand-off distance and the jet easily penetrates 65 mm (2.1/2 inches) of steel.

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Point Focal Charge / 150 mm Plate

ENTRY HOLE EXIT HOLESETUP

The same charge is then fired at a section of 65 mm plate on edge – a 150 mm thickness of steel.

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Two 20mm Plates – 450 mm Apart

SETUP ENTRY ENTRYTOP PLATE BOTTOM PLATE

The hole through the top plate is clean and circular. The bottom plate, while still penetrated, shows signs of the jet “droplet-izing” and beginning to loose coherence.

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Other Types of Focused Charges

• A hemispherical charge produces a slower jet but no slug.

• Linear charge produces a long “ribbon” of cutting jet.

OTHER SHAPED CHARGESHEMISPHERICAL SHAPED CHARGELiner "turns inside out" rather than being slapped togetherResults in a slower jet with a more uniform velocity profileLess likely to produce a "slug" and block the hole

APPLICATIONS OF POINT FOCAL CHARGESINDUSTRIALWell perforators for the Oil and Gas IndustryTapping steel furnacesSeismic / geological surveysMining - rock breaking chargesClearing bore holesMILITARYArmour penetrating missile warheads / artillery shellsDemolition charges for "hole drilling" into concrete or ground

LINEAR CUTTING CHARGEInitiated from one end and produces a "ribbon" jetMost sophisticated design shownTube provides a degree of confinement but fragsPlastic or wooden case with metal liner can be used - twice explosiveFlexible - Royal Ordinance (UK) "Blade" product

APPLICATIONS OF LINEAR CUTTING CHARGESINDUSTRIALMainly demolitionRocket separationLAW ENFORCEMENTRapid entry wall breaching Access for fire fighting - "Jet Axe" productMILITARYLarge "Hayrick" charges for demolitionExplosive ordinance disposal (EOD)Canopy cut-off for aircraft ejection seats

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Explosively Formed Projectiles

• Explosively Formed Projectiles (EFP), Ballistic Disks or Self Forging Fragments have a much thicker liner that forms a more massive, slower moving projectile. EFPs can travel hundreds of metres.

EXPLOSIVELY FORMED PROJECTILESAlso referred to as Self Forging Fragments, Ballistic Disks or Explosively Formed PenetratorsR.W. Woods of John Hopkins University first described in 1936Thicker liner produces a slower, more massive projectile (2,000 to 750 m/s)Much longer effective range than "jet" producing chargesVariations in liner design / explosive fill to produce different shapes:

APPLICATIONS OF EFPSINDUSTRIALUnderground hard rock mining – refer following illustrationMILITARYAnti armour (typically Main Battle Tanks)Explosives Ordinance Disposal (EOD)Special forces - attacking substations / oil storages

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Applications of EFPs

In underground hard rock mining - a “hang up” – the 2 large rocks blocking the draw point need to be dislodged to allow the remainder of the blasted rock to fall through. An explosively formed projectile (EFP) can be sand-bagged in position at a safe distance from the “hang up”. The EFP is aimed at the rock causing the blockage and then be fired remotely.

This reduces the need for personnel to enter a hazardous area to place explosives directly against the blockage.

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Explosive Forming

EXPLOSIVE FORMING - PICTUREUsed for very thick materials - nuclear containment vessels.Smaller, intricate parts for aerospace.Results in very low residual stresses in the work piece as pressure is applied uniformly.

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Explosive Cladding

EXPLOSIVE CLADDINGMust produce a jet at the interface to remove impurities.Must produce sufficient pressure for sufficient time to achieve stable inter-atomic bonds (page 113 Fundamentals ..)Requires a thinner amount of cladding material than roll applied methods.Good for small quantities of plate – no time for setting up a large rolling mill.

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Further Reading• Walters, W. P. and Zukas, J. A., Fundamentals

of Shaped Charges, 1989, Jon Wiley and Sons, U.S.A

• Walters, W. P. and Zukas, J. A., Explosive Effects and Applications, 1998, Springer-Verlag, U.S.A

• Meyer, R. and Köhler, J., Explosives Fourth Edition, 1993 VCH Verlagsgesellschaft mbHGermany

• www.havoc.com.au• www.isee.org – International Society of

Explosive Engineers