Propagation of the Detonation Shockwave

The theory of detonation is a very complicated process containing many mathematical equations and far too complicated to be discussed here. The account given below is a very simplified qualitative version to give some basic understanding of the detonation process. 

This sound wave contains regions of rarefactions and compressions. The temperature of the material increases in the compression regions and then cools due to adiabatic expansion. In an explosive composition 

In order for the wave front to propagate forward (not laterally) and over a considerable distance, the explosive substance should either be confined inside a tube or have a cylindrical geometry. If the diameter of the explosive substance is too small, distortion of the wave front will occur, reducing its velocity and therefore causing the detonation wave to fade since the energy loss sideways is too great for detonation to be supported. Consequently, the diameter of the explosive substance must be greater that a certain critical value, characteristic of the explosive substance. 

Detonation along a cylindrical pellet of a secondary explosive can be regarded as a self-propagating process in which the axial compression of 

On suitable initiation of a homogeneous liquid explosive, such as liquid nitroglycerine, the pressure, temperature, and density will all increase to form a detonation wave front. This will take place within a time interval of the order of magnitude of 10 12 s. Exothermic chemical reactions for the decomposition of liquid nitroglycerine will take place in the shockwave front. The shockwave will have an approximate thickness of 0.2 mm. Towards the end of the shockwave front the pressure will be about 220 kbar, the temperature will be above 3000 °C and the density of liquid nitroglycerine will be 30% higher than its original value. 

This sound wave contains regions of rarefactions and compressions. The temperature of the material increases in the compression regions and then cools due to adiabatic expansion. In an explosive composition the compression part of the wave is sufficiently high to cause the temperature to rise above the decomposition temperature of the explosive crystals. As the explosive crystals decompose just behind the wave front, a large amount of heat and gas is generated. This in turn raises the internal pressure which contributes to the high pressures at the front of the wave. These high pressures at the wave front must be maintained for the wave front to move forward. 

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