Explosive charge

The predetonation distance (the distance the decomposition flame travels before it becomes a detonation) depends primarily on the pressure and pipe diameter when acetylene in a long pipe is ignited by a thermal, nonshock source. Figure 2 shows reported experimental data for quiescent, room temperature acetylene in closed, horizontal pipes substantially longer than the predetonation distance (44,46,52,56,58,64,66,67). The predetonation distance may be much less if the gas is in turbulent flow or if the ignition source is a high explosive charge. 

Pyrotechnics have been used for military purposes for many centuries as propellants, explosive charges, time fuses, and for illumination. There are still many uses of pyrotechnic devices in military appHcations, where they provide portability, storage stability, simplicity of operation, safety, and the reUability required for military scenarios. The devices must be capable of surviving rough handling, weather extremes, and extended storage, yet reUably perform when called on to function. 

Pitch. Pitch used to be stored in solid form at the tar distillery in open bays, from which it was removed by small explosive charges. Loading of the lump pitch by mechanical shovel created a dust ha2ard both at the tar installation and at the customer s, where the lumps had to be ground before use. In the 1990s, pitch is stored in tanks heated by superheated steam or circulating hot-oil coils and transported in fiquid form in insulated rad, road tankers, or ships. When transport as a hot fiquid is not feasible, not acceptable by the customer, or for small amounts, the pitch is converted into a dust-free particulate form, ie, short rods termed pencils, pastilles, or flakes. 

Shock Synthesis. When graphite is strongly compressed and heated by the shock produced by an explosive charge, some (up to 10%) diamond may form (26,27). These crystaUite diamonds are small (on the order of 1 llm) and appear as a black powder. The peak pressures and temperatures, which are maintained for a few microseconds, are estimated to be about 30 GPa (300 kbar) and 1000 K. It is beheved that the diamonds found in certain meteorites were produced by similar shock compression processes that occurred upon impact (5). 

Another process involves explosive bonding. The corrosion-resistant metal is bonded to a steel backing metal by the force generated by properly positioned explosive charges. Relatively thick sections of metal can be bonded by this technique into plates. 

The complexity of the stress waves generated by explosive charges or projectile impact, and the appearance of relief waves that emanate from free sur-... 

The client insisted on a test. The smoke detectors worked, and the explosive charge operated, but the cutter did not cut the rupture disc. The explosive charge could not develop enough pressure because the volume between it and the rupture disc was too great. The volume had been increased as the result of a change in design installation of a device for discharging the halon manually. 

The upper half of Figure 3.9 represents how a spherical explosive charge of diameter d produces a blast wave of side-on peak overpressure P and positive-phase duration r" " at a distance R from the charge center. Experimental observations show that an explosive charge of diameter Kd produces a blast wave of identical side-on peak overpressure p and positive-phase duration Kt at a distance KR from the charge center. (This situation is represented in the lower half of Figure 3.9.) Consequently,... 

For these and other purposes, blast-modeling methods are needed in order to quantify the potential explosive power of the fuel present in a particular setting. The potential explosive power of a vapor cloud can be expressed as an equivalent explosive charge whose blast characteristics, that is, the distribution of the blast-wave properties in the environment of the charge, are known. 

The above procedure produces blast parameters applicable to a completely symmetrical blast wave, such as would result from the explosion of a hemispherical vessel placed directly on the ground. In practice, vessels are either spherical or cylindrical, and placed at some height above the ground. This influences blast parameters. To adjust for these geometry effects, and 7 are multiplied by some adjustment factors derived from experiments with high-explosive charges of various shapes. 

The Universal Hopkinson-Cranz and Sachs Laws of Blast Scaling have both been verified by experiment. These laws state that self-similar blast (shock) waves are produced at idendcal scaled distances when two explosive charges of similar geometry and the same explosive composition, but of different size, are detonated in the same atmosphere [49]. 

Compare two different explosive charge weights of the same material. For an observed overpressure of 40 psi from a specific charge using the scaling equation above, the scaled distance is Z = 5 ft/lb /. WTiat is the distance for an overpressure of 40 psi with a charge of 500 lb ... 

Spriggs J. Krc, Industrial Engineering Study on the Determination of Additives to Eliminate Cracking of Cast Explosive Charges , ARF Rept 5 (Final), Project C 114 (Sept 1958), AD 203745 32) W.R. Tomlinson O.E. Sheffield, PATR 1740 (Rev 1) (1958), 337 33) T. Urbanski et... 

HNS/Teflon Explosive Charges For The Apollo 17 Seismic Experiment, LSPE , NOLTR 73-44... 

Evaluation of Elliptical Experimental Explosive Charges (Z-Test) , Rept No USAMERDC-2116(1974)... 

A hydrogen bomb, which uses nuclear fusion for its destructive power, is three bombs in one. A conventional explosive charge triggers a fission bomb, which in turn triggers a fusion reaction. Such bombs can be considerably more powerful than fission bombs because they can incorporate larger masses of nuclear fuel. In a fission bomb, no component of fissionable material can exceed the critical mass. In fusion, there is no critical mass because fusion begins at a threshold temperature and is independent of the amount of nuclear fuel present. Thus, there is no theoretical limit on how much nuclear fiiel can be squeezed into a fusion bomb. 

There are many miscellaneous applications of explosives which may be mentioned but which do not merit individual description. Such uses are those in agriculture, in the preparation of ditches, the diversion of streams, removal of tree stumps, and the breaking up of subsoil. Demolition of old buildings and chimneys is readily carried out. Underwater wrecks may also be broken up for disposal by special application of explosive charges. 

In recent years much attention has been paid to the use of explosives for the shaping and working of metals. Figure 14.12 illustrates a simple application of the process for forming a dished end of a vessel. A flat metal blank is placed over a suitable mould and the space between them evacuated. Above the blank is water and in this a suitable explosive charge is fired. The metal takes the form of the mould with little or no spring-back and usually does not require further treatment. The process is particularly... 

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