h. soury

Porous explosives such as octogen (HMX) are classified as high-sensitivity secondary explosives, which are in powder form and are usually charged by the pressing method. Investigating the behavior of these materials under shock waves has always been a challenge for researchers. In this research, the hydrodynamic behavior of these materials in the shock tube was investigated in a two-phase manner. In the modeling of two-phase systems with the presence of shock waves, the differential equations are hyperbolic; Therefore, to capture the pressure pulse in the shock tube, a Riemann solver is needed. In this research, Ecogen software was used for simulation. This software is equipped with Kapila's multiphase model and uses a Riemann solver with the ability to capture shock waves to solve differential equations. Simulation of the shock tube in two modes of pressure pulse with low amplitude and pressure pulse with high amplitude was carried out using two-phase Kapila model and data from previous researches were used for validation. Comparing the results of the simulation with the data of previous researchers showed a difference of less than 5%.

One of the most important issues when working with energetic materials is their initiation. Of the various methods of energetic materials initiation in the military and civilian industries, shock initiation is of particular importance. Numerical and simulation study of the shock initiation of condensed phase explosives is related to models called burning rate models, which describe the conversion rate of unreacted materials to detonation products. Among the burning rate models that have been proposed for explosives so far, the Ignition and Growth (I&G) model is one of the most popular and widely used models. In this paper, the genetic optimization algorithm is coupled with an upgraded Fortran SIN simulator hydrocode. The calibration was based on minimizing the difference between the calculated pressure data and the experimental data obtained from manganin pressure gages in the shock initiation tests. The results of optimizing the I&G parameters for Comp-B demonstrates good accuracy of the algorithm; So that after calibration, the difference between the pressure history obtained from the calculations of this paper and the experimental data was about 15% and in this respect is about 6% more accurate than the results reported in previous reseorches.

In this paper, the sympathetic detonation is studied. In this type of detonation, the shock wave of an explosive by passing through a neutral environment (gap) induces the detonation in the second explosive. The study of this phenomenon is important to the safety of the ammunition depot and their transportation. In the present study, the sympathetic detonation in Comp-B has been studied. In this regard, the effect of the thickness of the gap and the type and composition of the materials used as the barrier in preventing the occurrence of sympathetic detonation has been investigated. The results showed that a thick layer of fine sand, held by thin layers of polymeric material, is more efficient than other materials and can prevent sympathetic detonation well. The results indicate that a 20 mm single iron barrier and also 20 mm barriers consisting of sand + Plexiglas, sand + epoxy and sand + rubber prevent from the sympathetic detonation of the Comp-B acceptor.

Detonation initiation by shock is an important issue in the explosive safety assessment , design of the explosive train and explosive devices. Experimental studies in this area are very difficult, expensive, and require advanced equipment. Therefore, simulation is a useful and suitable way for studying this phenomenon. The purpose of this article is to develop a one-dimensional computer code for simulation of the direct initiation of energetic materials. The Fortran SIN hydrocode, was used for this purpose and the I&G burn model was added to this code. The developed code was used to simulate the direct initiation of the Comp-B by sustained shock pulses. A good agreement was observed between the present simulation results and the results of other references. For example, in the simulation of the initiation of Comp-B by 3.78 GPa shock, the run distance to detonation was 14.8mm, which the difference between this value and the reported experimental data is 5.7%.

In this study, the reactive Euler equations are solved in the reaction zone between the leading shock and sonic locus for curved detonations propagating in high explosives. The explosive material is described by general equation of states and reaction rate law. The investigation is carried out by the "Detonation Shock Dynamics" (DSD) method. The effects of the front curvature on the detonation velocity and its properties are determined for divergent and convergent detonations. Governing equations are written in shock attached frame and simplified assuming small detonation front curvature (relative to half-reaction length) and slow-varying shape (relative to particle pass time through reaction zone). It is observed that increasing the front curvature leads to decreasing of the diverging detonation velocity relative to the corresponding ZND detonation. Besides, for curvature higher than a critical limit the detonation fails. Decreasing the converging detonation curvature radius causes a dramatic increase in the detonation velocity and pressure. In the reaction zone of the high explosive materials, the reactant and products exist simultaneously. Computation of the mixture properties needs some assumptions known as the mixture rule. In the present work, the effects of the mixture rule on the planar and curved detonation is studied. It is demonstrated that the kind of the mixture rule does not have considerable effects on the planar detonation. However, its effect on the curved diverging detonation is significant and leads to a substantial change of the detonation properties such as the velocity and pressure.