Versione di lingua italiana
Deutsch Sprachenversion
English language version
Choose language:

Economy-point.org



» Personal Loan No Credit Check, Online Economics » Pyrotechnics » Topics begins with D » Detonation


Page modified: Wednesday, July 13, 2011 14:41:47

A detonation is a form of an explosion, with which the chemical reaction of the explosive is coupled with a shock wave and with a energy-supplying chemical conversion of the propagation medium and will maintain from this. An explosive, which is appropriate for a Explosionsreaktion in form of a detonation, is called explosive. A detonation is to a large extent independent of the outside pressure and the temperature. A insulation of the explosive is not necessary.

Reaction

With a detonation goes through a very narrow, nearly surface-like reaction zone the explosive with a speed, which is larger than the speed of sound of the undecomposed explosive, on the basis of the place of initiation. Within this only few micrometers spread detonation front prevail a very high pressure of up to 500 Kilo bar and a very high temperature of up to 6000"°C; the subject is highly compressed, ionized (becomes electrically leading) and emits light, recognizably as detonation lightning. The explosive reacts within the reaction zone under Energiefreisetzung to usually gaseous final products. This reaction energy compensates the dissipativen loss of energy, which weakens finally a shock wave in a not reactive material (for example steel, water or air) with the time and lets dead-run.

Speed

The speed, with which the detonation front moves by the explosive, is called detonation speed. After a certain starting distance, which depends on the kind of initiation, a stable detonation speed adjusts itself, which depends only on the characteristics of the explosive and the curvature of the detonation front. The values for the detonation speeds, indicated for the explosive data, apply to an even detonation front and lie between 2000 to 10000 m/s. The detonation speed depends on the power density of the explosive, whereby only within 0,1 reaction energy set free after arrival of the detonation front contributes to the detonation speed.

Geometry of the charge

With an explosive column with constant circular cross section the detonation speed is the smaller, the smaller the diameter of the column is. Mainly by the explosive characteristics and slightly by the firmness of the inclusion if dependent critical diameter is certainly, fallen below, then the detonation can reproduce itself along the column reliably and does not tear also after very strong initiation off.

Pressure

Crucially for the strength of an explosive is above all the detonation pressure, which is approximately proportional to the square of the detonation speed and to the density of the explosive.

If a detonation front meets an adjacent body, then this works like an extremely strong impact, which causes very strong accelerations. The forces arising with it amount to a multiple of the between-atomic binding forces. There is no material, which can withstand the detonation impact of an explosive explosive directly. In a more or less broad zone by a detonation impact the chemical structure of the goal material is torn up.

Reaction environment

A detonation can occur except in firm and liquid explosives also in explosive gas mixtures and even in nuclear fuel material (e.g. with supernew facts of the type a Ia). Against common different phrased statements arises with atomic explosions usually however no detonation in the nuclear component; with Kernspaltungsbomben for example there is at all no reaction front.

The impact front arising in the explosive spreads after consumption of the explosive also into the surrounding medium and forms a typical detonation wave. However also a Deflagration can release a shock wave in the surrounding medium, if in this the speed of sound is substantially lower than in the deflagrierenden fuel.

Unwanted spark advance in combustion engines, the called knocking, can lead to a detonation and cause substantial damage to the engine.

Ideal detonation

If the chemical conversion is practically complete within the detonation front, then it concerns ideals a detonation, which is described by the Chapman Jouguet theory with sufficient accuracy. One tries to simulate Nichtideale detonations with retarded reactions and a broader, three-dimensional reaction zone with complex computer simulations. An important example of an not-ideally detonating explosive is Triaminotrinitrobenzol.

Demarcation

Contrary to the detonation propellants in form of a Deflagration are to explode, burn down thus very fast and controlled under gassing and carry mechanical work out, to drive about a projectile from a Gewehrlauf. The Deflagration is pressure and temperature-dependent. A Deflagration can accelerate itself under inclusion by mass inertia or insulation and change in some materials into a detonation. A detonation in a rifle would cause its destruction.

Term

Generally linguistic usage is used the term detonation for explosions, with which a sharp bang or an intensive pressure wave arises, even if the expiration is not physically seen a detonation, e.g. with nuclear explosions or when pyrotechnic bang corroding. Frequently with it, following English linguistic usage, also the ignition of an explosive charge and not the actual explosion procedure are meant.

Literature

  • D.L.Chapman: Phil. Likes. (Lond. Edinb. Dubl.) 47, 90 (1899)
  • E.Jouguet: J. Math. Pure Appl. 60, 347 (1905); 61,1 (1906)
  • J.Taylor: "Detonation in Condensed explosive", Clarendon press, Oxford 1952
  • J.Neumann, R.D.Richtmeyer: J. Appl. Physical 21, 232 (1950)
  • C.E.Anderson, J.S.Wilbeck, J.C.Hokanson, J.R.Asay, D.E.Grady, R.A.Graham, M.E.Kipp, in Y.M. Gupta: "Shock Waves in Condensed of matte - 1985", plenum press, New York 1986
  • J.M.Walsh, R.H.Christian: Physical Rev. 97, 1544-56 (1955)

See also

  • Detonator

Articles in category "Detonation"

We found here 4 articles.

D

» Danger of explosion
» Deflagration
» Department
» Detonation

Page cached: Wednesday, October 22, 2014 13:12:35
Valid XHTML 1.0!  Valid CSS!

Page copy protected against web site content infringement by Copyscape