| The deflagration to detonation transition（DDT）characteristic of energetic materials is an important index affecting its production,storage,use safety and function reliability.In this paper,based on the establishment of the experimental device of deflagration to detonation transition of small-size charge,the deflagration to detonation transition characteristics of various explosives under the condition of small-size charge are studied,the factors affecting deflagration to detonation transition and their influence laws are systematically studied,and 1:1numerical simulation and analysis are carried out.Based on the theoretical simulation and experimental results,the optimal conditions for realizing the transition from deflagration to detonation are determined,which provides a reference basis for the safety of explosive production and use and the design of non primary explosive DDT detonator.The main research contents and achievements of this paper are as follows:（1）The DDT performance tests of seven traditional and new synthetic explosives such as1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane（HMX）and 5,5’-tetrazole-1,1’-dihydroxyamine（TKX-50）were carried out in totally enclosed steel tubes with an outer diameter of 6 mm and a length of 50 mm.Two explosives that are easy to realize DDT,HMX and TKX-50,were selected,and the effects of charge density,particle size,binder,restraint strength and ignition conditions on DDT were studied.The results show that the charge density ranges of HMX and TKX-50 are 1.2～1.4 g·cm-3 and 1.0～1.3 g·cm-3 respectively,and the crystal size of explosive is100μm is easy to realize the DDT;The addition of binder is not conducive to the ignition and DDT;Mg/Ba O2 ignition powder can promote the occurrence of DDT.（2）According to the shell failure phenomenon of straight tube deflagration to detonation transition test,a spacer deflagration to detonation transition device is designed.The results show that adding spacer can significantly improve the reliability of the transition from deflagration to detonation of explosive.Under the conditions of donor charge density of 0.8g·cm-3 and acceptor charge density of 1.2 g·cm-3,insensitive explosives such as 2,2’,4,4’,6,6’-hexanitrodiphenylethylene（HNS）and 3,3’,5,5’-tetrachloro-2,2’,4,4’,6,6’-hexanitroazobenzene（BTCHNAB）can achieve stable detonation.Under the same charge conditions,the stronger the constraint strength of donor charge,the more conducive it is to drive the spacer.Similar to the results of deflagration to detonation transition test without spacer,there is an optimal range for the response of acceptor density to spacer initiation that the density ranges of HMX and HNS are 1.0～1.3 g·cm-3 and 1.1～1.4 g·cm-3 respectively.Three particle sizes（10,100,500μm）of the acceptor charge test results show that the larger the size of the explosives crystals,the more likely to be detonated.（3）The influence of spacer thickness on explosive DDT in the spacer deflagration to detonation transition device is simulated by Autodyn dynamics software.The calculation results show that when the thickness of the spacer is≥0.3 mm,the movement speed of the spacer driven by the donor charge increases with the decrease of the thickness.When the thickness of the spacer is less than 0.3 mm,due to the serious deformation,the movement speed decreases sharply with the decrease of thickness,which can not provide sufficient initiation energy for the acceptor charge.In a certain range,the greater the thickness of the spacer,the smaller the critical speed required for the initiation acceptor charge.Considering the influence of thickness on the characteristic velocity and critical velocity,the optimal spacer thickness is determined to be 0.3 mm. |
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