Estimating the amplitude of the pressure on the obstacle of products of an under-compressed outgoing detonation wave of a structured charge

The study relies on the concepts of various mechanisms of explosives decomposition at supersonic propagation of the under-compressed detonation reaction zones, and examines the structured charges explosion effect on compressible obstacles. In such charges, artificially or naturally, there can appear rod-like formations highly capable of detonation, penetrating the charge and ensuring the propagation of the complete heat release zone at a speed greater than the normal, and the ideal detonation speed of a monodisperse charge is of the same density. We introduce a simple algebraic model of the explosive process of structured charges, the process proceeding in the form of under-compressed detonation. We obtained algebraic expressions that make it possible to compare the peak pressures at the obstacles depending on the direction of detonation propagation relative to the obstacle and on the mode of detonation, i.e. whether it is normal or “under-compressed”.

Interface Characterization of Ni/Al Bimetallic Explosively Welded Plate Manufactured with Application of Exceptionally High Detonation Speed

The investigation is dedicated to the detailed microstructure characterization of explosively welded clads, in which, exceptionally and for cognitive purposes, a very high detonation speed of about 2800 m/s was used to manufacture bimetallic aluminum-nickel plates. The study involves detailed microstructural characteristics of the bonded zone at micro and nano level, especially focused on the expanded melted regions consisted mostly of Al3Ni, Al3Ni2 and AlNi phases. In situ heating experiment in transmission electron microscope allowed observing microstructure transformation revealing that additionally present metastable Al9Ni2 phase was transformed to Al3Ni and Al3Ni2. Microhardness measurements across the welded zone showed the increase of the microhardness of nickel alloy plate from 153 up to 170 HV when approaching to the Ni201/A1050 interface, while the value for aluminum plate was of 45 HV. Within the melted zones the microhardness was found to be 135 HV and it enormously increased to 850 HV after annealing of the sample at 500 °C. This change was due to the transformation of the interface region from the waves with the melted zones into the continuous layers of two intermetallic phases: Al3Ni and Al3Ni2. The second phase grew at the expense of the Al3Ni.

The effect of compaction of a porous material confiner on detonation propagation

The fluid mechanics of the interaction between a porous material confiner and a steady propagating high explosive (HE) detonation in a two-dimensional slab geometry is investigated through analytical oblique wave polar analysis and multi-material numerical simulation. Two HE models are considered, broadly representing the properties of either a high- or low-detonation-speed HE, which permits studies of detonation propagating at speeds faster or slower than the confiner sound speed. The HE detonation is responsible for driving the compaction front in the confiner, while, in turn, the high material density generated in the confiner as a result of the compaction process can provide a strong confinement effect on the HE detonation structure. Polar solutions that describe the local flow interaction of the oblique HE detonation shock and equilibrium state behind an oblique compaction wave with rapid compaction relaxation rates are studied for varying initial solid volume fractions of the porous confiner. Multi-material numerical simulations are conducted to study the effect of detonation wave driven compaction in the porous confiner on both the detonation propagation speed and detonation driving zone structure. We perform a parametric study to establish how detonation confinement is influenced both by the initial solid volume fraction of the porous confiner and by the time scale of the dynamic compaction relaxation process relative to the detonation reaction time scale, for both the high- and low-detonation-speed HE models. The compaction relaxation time scale is found to have a significant influence on the confinement dynamics, with slower compaction relaxation time scales resulting in more strongly confined detonations and increased detonation speeds. The dynamics of detonation confinement by porous materials when the detonation is propagating either faster or slower than the confiner sound speed is found to be significantly different from that with solid material confiners.

Study on Ball Milling of TiH2 and Application in Energetic Materials

Particle distribution of titanium hydride (TiH2) during the ball mill process was studied by milling it with different time. Scanning electron microscope (SEM) pictures showed that particle size decreased quickly at the initial stage, and homogeneous, super fine TiH2 powder was obtained after 4 h mill. Application of TiH2 in energetic materials was investigated by preparation of TiH2/RDX composite explosive and measuring the detonation speed. Results showed that detonation speed of TiH2/RDX explosive was depended on the content and particle size of TiH2. TiH2 is a potential additive in high explosives (HE).

The Effect of Atmosphere and Vacuum on Character of Weld Joints Fabricated by Explosion

This paper presents an experiment conducted in Explosia, a.s., Pardubice. A bimetal prepared of AZ 31 Mg alloy - CrNi austenitic steel was tested in various conditions, and consequently its quality was assessed. Focus was particularly on the impact of atmosphere and vacuum on the interface character of the metals (bimetals) prepared by explosion. Parallel placement of the materials being welded was used for welding in both vacuum and air atmosphere. Welding sets were designed and manufactured. The welding parameters and conditions were set up utilising the available computational means, and then verified by simulation in ANSYS engineering-scientific program. Used was Semtex S 35, a loose explosive, as well as Startline 12, an initiation explosive. Bimetal was fabricated in the air atmosphere at the detonation speed 2613 m.s-1 and in vacuum at the detonation speed 2597 m.s-1. Quality of bimetals was assessed by optical microscopy, measuring deformations by a 3D scanner, measuring microhardness and also by EDX microanalysis.

Multi-Rate Digital Control for Pulse Detonation Engine Control Applications

Pulse detonation engine is a kind of new engine for spacecraft, it is difficult to control for there is no moving parts in engine combustion chamber and detonation speed is very fast. The engine model was given based on thermodynamics equations in the paper. A multi-rate digital controller for a pulse detonation engine based on the engine model was also given. The simulation results show that the control method is effective. The detonation engine model provides a basis for developing and validating controllers capable of controlling the engine.

The Experiment Study on the Shielded Charge Initiated by the High Speed Fragment

The experiments of the shielded charge initiated by the high speed half- prefabricated steel fragment has been studied in this paper. The damage way of half- prefabricated steel fragment to the shielded charge is hit, burning or detonation action. And the damage effect is structure damage or function damage. The result shows that toward Comp. B explosive with 1.62g/cm3 dense behind 6mm Q235 steel and of φ 200 mm×100mm size, the fragment’s critical detonation speed is about 2 400~2 600m/s.