Investigation On Cook-off & Shock Initiation Characteristics Of DNAN/HMX Aluminized Melt-Cast Explosives

2,4-Dinitroanisole（DNAN）is a kind of insensitive carrier for melt-cast explosives.It has some advantages such as low sensitivity,good compatibility with AP,no oil leakage,low viscosity,low shrinkage and so on compared with Trinitrotoluene（TNT）,thus it has a broad application prospect.In this paper,some investigations regard as cook-off and shock initiation characteristics of a kind of DNAN/HMX/Al（30/40/30）melt-cast explosive are launched by using the method of theoretical analysis,numerical simulation and experimental verification,providing technical support for the safety evaluation of DNAN/HMX aluminized melt-cast explosives under the action of heat or shock wave.The main research contents and conclusions are as follows:（1）Numerical simulation and experimental research on cook-off:The thermodynamic parameters of the explosive are obtained through thermal analysis experiments and theoretical arithmetic;the one-dimensional unsteady heat conduction differential equation is established and discretized;the one-dimensional unsteady numerical model of cook-off is written using MATLAB,and by comparing with the calculated results under the same working conditions in the literature and simulated cook-off experiments of shelled charge exposed at a constant heating rate of 1.0K·min^-1,the correctness of the numerical model is verified.The influence of the charge shell and ambient temperature on the ignition time and ignition position are studied by means of the numerical model,and the results show that,（a）When the heating rate is 1.0K·min^-1,there is just a little disparity between the cook-off results of charge with 0mm and 3mm shell.The influence of the shell on the cook-off results can be ignored;（b）Under the condition that the heating rate rises,the ignition time decreases from infinity until tending to zero,while the ignition position remains at the axial center of charge initially,and then gradually moves to the surface of the charge;（c）Under the condition that the ambient temperature remains unchanged,the critical ambient temperature at which thermal ignition can occur is about 246℃（correct just for the numerical model in this paper）,and when the constant ambient temperature rises from the critical value,the change trends of the ignition time and ignition position are consistent with the conclusion put in（b）.（2）Numerical simulation and experimental study on the thickness of large gap:The parameters in JWL equation of state about detonation products of the DNAN/HMX aluminized melt-cast explosive are calculated by BKW program;the pressure curves during the shock initiation process are measured through Lagrange analysis experiment;the values of the parameters in Shock equation of state and in the ignition-growth equation of reaction rate are manually calibrated with AUTODYN,based on the pressure curves measured by Lagrange analysis experiment;the two dimensional numerical model of large gap test is established using AUTODYN,and the calculated critical thickness of the gap is about34.5mm;and the critical gap thickness measured in the gap experiment identical with the numerical model in terms of condition is 31.2mm.The calculated result is consistent with the experimental result,thus he correctness of the values of the parameters used in the numerical simulation is verified effectively.