Determining the relationship between critical conditions of detonation propagation and the average decomposition rates of explosives in detonation waves

The study introduces a model of steady propagation of non-ideal detonation of open cylindrical charges with diameters close to critical ones. The model was obtained in the quasi-one-dimensional approximation with the use of analytical methods. We found a solution for the model’s closing equation, which directly relates the average decomposition rate in the detonation front, determined by the parameters of the formal kinetics equation and dependent on the detonation rate, the gas-dynamic parameters of the initial explosive and its reaction products (isentropic exponents), the duration of the chemical peak and ideal detonation velocity, and also the ratio of the charge diameter to the duration of the chemical peak of the ideal detonation. We obtained an equation which reflects the dependence of the non-ideal detonation velocity on the charge diameter. The critical diameter is determined as the range boundary of the charge diameter values at which this equation still has a solution. The study shows that the expression for the fundamental characteristics of the detonation process, i.e. the ratio of the spread time and the reaction time of the explosive, differs from the expression used in the Khariton principle when taking into account the divergence of the reacting flow in the curved detonation front. As for the critical value of this ratio, in general it is different from the unity and is a variable value depending on the characteristics of the kinetics of decomposition of a substance in shock waves. Based on the calculations, we draw a conclusion that changes in the microstructure of the explosive charge of the same composition, displayed by changes in the parameters of the formal kinetics equation, are accompanied by relative changes in the critical diameter, many times greater than the relative changes in the duration of the chemical peak of ideal detonation

Simulations on concrete penetration of shaped charges

In this paper, the effects of the use of various aluminium materials as liner material in shaped charges for the perforation of concrete slabs are examined with numerical simulations. Using AUTODYN-2D software, formation of the shaped charge jets for seven different aluminium materials are modelled first and then these jets are directed to 35 MPa compressive strength concrete slabs. Those analyses are performed for a constant liner thickness which corresponds to 8% of the shaped charge diameter. Furthermore, the effect of standoff on the penetration of concrete slabs is examined by using shaped charges with the same geometry and liner material (7075-T6). The cone angle of the shaped charge is taken as 100°.

The Porosity of Liner Effect on the Shaped Charge Jet Penetration

Shocking temperature rise of the shaped charge with porous liner before collapse was calculated based on the Herrman equation of state. Shaped charges with 36mm charge diameter were used to fire at the 603 armor steel target, the penetration-standoff curves(P-S) of the shaped charge liner with 88.6% and 90.3%T.D were measured and compared. It is shown that proper porosity is helpful to lengthen the jet break up time and penetration depth，which is of significance for the application of porous liner.

NON-IDEAL DETONATION PROPERTIES OF AMMONIUM NITRATE AND ACTIVATED CARBON MIXTURES

To obtain a better understanding of detonation properties of ammonium nitrate (AN) and activated carbon (AC) mixtures, steel tube tests with several diameters were carried out for various compositions of powdered AN and AC mixtures and the influence of the charge diameter on the detonation velocity was investigated. The results showed that the detonation velocity increased with the increase of the charge diameter. The experimentally observed values were far below the theoretically predicted values made by the thermodynamic CHEETAH code and they showed so-called non-ideal detonation. The extrapolated detonation velocity of stoichiometric composition to the infinite diameter showed a good agreement with the theoretical value.

Diameter Effect on Detonation Velocity of Ammonium Nitrate and Activated Carbon Mixtures

To obtain a better understanding of detonation properties of ammonium nitrate (AN) and activated carbon (AC) mixtures, steel tube test with several diameters was carried out for various compositions of powdered AN and AC mixtures and the influence of the charge diameter on the detonation velocity was investigated. The results of test indicated that the detonation velocity increased with the increase of the charge diameter. The experimentally observed values were far below the theoretically predicted values made by the thermohydrodynamic CHEETAH code and they showed so-called non-ideal detonation. The extrapolated detonation velocity of stoichiometric composition to the infinite diameter showed a good agreement with the theoretical value.