Semi-empirical analysis of the initial stage of the growth of the deception point beyond the shock wave front

The paper presents analysis results of the initial stage of decomposition of phlegmatized RDX behind the front of a shock wave with pressure at the front approximately equal to 2 GPa, presumably during the time preceding the merging of the initially isolated decomposition centers. In this case, the time dependences of the mass fraction of explosive decomposition products behind the shock wave front and their specific volume obtained by processing the results of experiments carried out by the method of quasi-thin layers (layers tenths of millimeters thick placed between blocks of an inert reference material) are used. Based on the dynamics of changes in the parameters of the state of the reacting charge revealed from the results of the experiment, the time dependences of the characteristics of the matrix explosive movement around the decomposition site were established within the framework of an elementary spherical charge cell model. It is taken in the form of a sphere containing a central pore filled initially with air. Time dependences (within tenths of a microsecond) of the radius of the decomposition site, represented as a spherical cavity filled with explosive combustion products and compressible initial pore gas, are obtained; tangential deformation and its velocity on control spherical surfaces located at different distances from the surface of the decomposition site; strains and strain rates on the spherical combustion surface are revealed. The influence on the estimates of these characteristics of the concentration of decomposition sites in the range of variation 1012....1013 m–3 and the residual air pressure in the pores remaining after the pressing of charges (0,1 MPa and 1 MPa). Deformations and strain rates on the surface of the decomposition site, considered as a combustion surface, can reach values equal to 25% and 106 1/s, respectively. The surface area of the decomposition site can be an order of magnitude greater than the combustion surface area, which would be if the specific volume of decomposition products was not significantly less than that of the explosive. The speed of displacement of the surface of the decomposition site can exceed the linear combustion rate by an order of magnitude.