Explosive Applications for Industry and Defense Speaker: Arran Gordon Company: Havoc Industries Pty Ltd Date: 19-Oct-06 1 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" EXPLOSIVES Burn or Deflagrate rather than Detonate Produce large volumes of gas which "explode" if confined VOD less than 1,000 m/s Examples: Black Powder – Pyrotechnics, Smokeless Powder - Propellant for Bullets / Shells "HIGH" EXPLOSIVES Detonate as Detonation Shock Wave passes through VOD greater than 1,000 m/s - typically 5,000 to 8,000 m/s Produce very high pressures, even when unconfined Examples: TNT, Dynamite, Mining Explosives - Watergels, Emulsions and Slurries, ANFO BLASTING AGENTS Are High Explosives Are less sensitive and more difficult to initiate Are not detonator or "cap" sensitive Examples: ANFO, Some Emulsions and Slurries INITIATING EXPLOSIVES High explosives that are very sensitive to heat and shock Used in small quantities in detonators Examples: Mercury Fulminate, Lead Azide, Lead Styphnate HISTORY OF EXPLOSIVES BLACK POWDER OR VARIANTS "Greek Fire" used in battle 668 AD - petroleum distillate thickened with resins Chinese references to gunpowder in 1040 AD ("Wu Ching Tsing Yao") English Friar Roger Bacon publishes gunpowder formula 1242 Gunpowder used in mining operations 1650 to 1800 William Bickford invents safety fuse 1831 HIGH EXPLOSIVES Alchemist Blasius Valentius produces "Fulminating Gold" 15th century Ascanio Sobrero discovers Nitroglycerine 1846-7 Wilbrand invents TNT 1863 Alfred Nobel develops first detonating blasting cap 1864 Alfred Nobel develops Dynamite1867 / gelatin dynamite 1875 ANFO rediscovered after ship explosion in Texas City 1950 2 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. 3 Various Explosive Items Selection of Orica Products Photos of Orica Explosive products and accessories. 4 Elements of a Shaped Charge • All shaped charges incorporate a symmetric hollow in the base. SHAPED CHARGE EFFECTS First discovered by von Förster 1883 coin and leaf impressions Charles E. Munroe rediscovered the effect from 1888 Munroe developed first lined shaped charge 1894 - tin can with dynamite tied around it WASAG / E and M Neumann in Germany 1911 Shaped charge development accelerated between 1935 and 1950 Franz Rudolph THOMANEK for Germany - First use-able lined SCs Henry Hans MOHAUPT for United States / United Kingdom SCs used in bazooka, panzerfaust and other devices 5 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. 6 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. 7 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”. 8 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. 9 Point Focal Charge / 150 mm Plate ENTRY HOLE EXIT HOLE SETUP The same charge is then fired at a section of 65 mm plate on edge – a 150 mm thickness of steel. 10 Two 20mm Plates – 450 mm Apart SETUP ENTRY ENTRY TOP 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. 11 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 CHARGES HEMISPHERICAL SHAPED CHARGE Liner "turns inside out" rather than being slapped together Results in a slower jet with a more uniform velocity profile Less likely to produce a "slug" and block the hole APPLICATIONS OF POINT FOCAL CHARGES INDUSTRIAL Well perforators for the Oil and Gas Industry Tapping steel furnaces Seismic / geological surveys Mining - rock breaking charges Clearing bore holes MILITARY Armour penetrating missile warheads / artillery shells Demolition charges for "hole drilling" into concrete or ground LINEAR CUTTING CHARGE Initiated from one end and produces a "ribbon" jet Most sophisticated design shown Tube provides a degree of confinement but frags Plastic or wooden case with metal liner can be used - twice explosive Flexible - Royal Ordinance (UK) "Blade" product APPLICATIONS OF LINEAR CUTTING CHARGES INDUSTRIAL Mainly demolition Rocket separation LAW ENFORCEMENT Rapid entry wall breaching Access for fire fighting - "Jet Axe" product MILITARY Large "Hayrick" charges for demolition Explosive ordinance disposal (EOD) Canopy cut-off for aircraft ejection seats 12 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 PROJECTILES Also referred to as Self Forging Fragments, Ballistic Disks or Explosively Formed Penetrators R.W. Woods of John Hopkins University first described in 1936 Thicker liner produces a slower, more massive projectile (2,000 to 750 m/s) Much longer effective range than "jet" producing charges Variations in liner design / explosive fill to produce different shapes: APPLICATIONS OF EFPS INDUSTRIAL Underground hard rock mining – refer following illustration MILITARY Anti armour (typically Main Battle Tanks) Explosives Ordinance Disposal (EOD) Special forces - attacking substations / oil storages 13 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. 14 Explosive Forming EXPLOSIVE FORMING - PICTURE Used 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. 15 Explosive Cladding EXPLOSIVE CLADDING Must 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. 16 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 mbH Germany • www.havoc.com.au • www.isee.org – International Society of Explosive Engineers 17.