Jämförelse mellan svenska gjutkrav och MIL-STD

Authors:

  • Elisabeth Bemm
  • Svante Karlsson
  • Magnus Bergh

Publish date: 2009-08-13

Report number: FOI-R--2795--SE

Pages: 28

Written in: Swedish

Keywords:

  • TNT
  • air gap
  • cavities
  • casting defects

Abstract

During late sixties a nunber of accidents occured with grenades that were initiating at launching. A study was performed by "Spaltgruppen" to analyse how these types of accidents could be prevented. The final report presented by "Spaltgruppen" resulted in that the standard requirements for melt casting of TNT in Sweden is more stringent than for example MIL-STD. A comparison between these standards has been performed to being able to determine whether grenades produced according to MIL-STD conforms to the Swedish requirements and is reported on in this report. Structural Dynamics Simulations show that initiation through shock compression can be considered highly unlikely. Futhermore, experiments suggest that broad air gaps at the botton of a grenade are considered critical. However, initiation during launch is still considered highly unlikely for grenades with a round bottom and where a (close to)frictionless interface between charge and cover can be excluded. When it comes to cavities, experiments show that a radius of 3,5 mm and a constant acceleration of 20000 g can lead to initiation in TNT. At the acceleration considered within this project, simulation indicates that spherical cavities do not collapse due to material strengh. However, further experiments are required, preferably in combination with a more sophisticated material model. For spheroidal (oblate) avities compression is achieved, but an estimate of the heating due to adiabatic compression suggest that the temperature in the surrounding explosive is well below the critical temperature for initiation reported in experiments performed under similar conditions.

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