Complete Detonation Research Articles

Research on preparation and high temperature resistance of primary explosive chromium azide

The research on novel high-temperature resistant primary explosives is an inevitable trend to adapt to the development of weapons. In this paper, high temperature resistant primary explosive cadmium azide was prepared from sodium azide and cadmium nitrate tetrahydrate by hydrothermal reaction. Then, the high-temperature storage performance was tested by cook-off test, and the influence of high temperature was analyzed in combination with microscopic morphology, crystal structure, and thermal decomposition temperature. The reliable ignition voltage was tested by electric ignition sensitivity, and the initiation performance of cadmium azide was verified by using CL-20 as secondary explosive. The results show that cadmium azide is an excellent high temperature resistant initiating agent primary explosive with the thermal decomposition temperature of 384.21°C and a 50% electric ignition voltage of 4.82 V, which can reliably initiate the CL-20 into complete detonation.

Study on Characteristics of the Light-Initiated High Explosive-Based Pulse Laser Initiation

The silver acetylene silver nitrate loading technology of the light initiated high explosive, as one of important means to simulate the structural response of powerful pulsed X-ray, adopts the pulse laser initiation. It has advantages of improvement of practical control, heterogenous loading realization and simultaneous loading timeliness. In this paper, the physical and mathematical models of hot spot initiation and photochemical initiation of energetic materials under the action of laser are firstly established, and then the laser initiation mechanism of the light initiated high explosive is specifically analyzed, and the laser initiation experiment is conducted based on the optical adsorption property of the light initiated high explosive. From this study, the laser initiation thresholds of 193 nm, 266 nm, 532 nm, 1064 nm wavelengths are given, and they are 5.07 mJ/mm2, 6.77 mJ/mm2, 7.21 mJ/mm2 and 10.61 mJ/mm2, respectively, and the complete detonation process is verified by detonation velocity. This work technically supports the study of pulse laser initiation process, mechanism and explosion loading rule as well as the loading technology of the light initiated high explosive to simulate the structural response of X ray.

In-situ preparation of copper azide by direct ink writing

The aim of the present work is to design a copper azide precursor direct writing ink for primary explosive-on-a-chip. The mixture of water/vinyl alcohol and isopropanol/ethyl cellulose was used as binder. Cetyltrimethylammonium bromide (CTAB) used as foaming agent and dodecanol as foam stabilizer were added into the binder to produce plenty of bubbles. 40 wt% of nano-copper powder was added into the binder and the three-dimensional porous precursor ink was obtained. After 24 h of in-situ gas–solid azide reaction, the copper precursor ink was completely transformed into copper azide. An explosive device was designed to verify the detonation performance of the copper azide by direct writing, and the result showed that it can reliably initiate the CL-20 into complete detonation.

Influence of water droplets on propagating detonations

In order to mitigate flame acceleration and detonation in hydrogen-air mixtures, which can lead to the release of harmful radionuclides in severe nuclear plant accidents, water spray systems are being considered. A series of experiments were conducted in a detonation tube filled with hydrogen-air mixtures. It was found that for a water droplet curtain with 215 μm droplets the detonation speed deficit was increasing with increasing size and density of the water droplet cloud, decreasing the speed below the speed of the detonation products. Moreover, as the initial pressure and equivalence ratio decreased, the speed deficit increased and, for the conditions tested, reached up to 16%. For most cases, 215 μm droplets quenched the detonation temporarily but the flow rapidly accelerated back to the initial detonation speed. It was concluded that the quenching effect for 215 μm droplets was limited by relatively fast evaporation time. However, this limitation was found to be partially overcome by the usage of additional injectors to reduce to injection time for a given injected mass of water. In contrast, nozzles giving water droplet diameters of 500 μm enabled complete detonation quenching.

Experimental Study of Bilinear Initiating System Based on Hard Rock Pile Blasting

It is difficult to use industrial explosives to excavate hard rock and achieve suitable blasting effect due to the low energy utilization rate resulting in large rocks and short blasting footage. Thus, improving the utilization ratio of the explosive energy is important. In this study, a novel bilinear initiation system based on hard rock blasting was proposed to improve the blasting effects. Furthermore, on the basis of the detonation wave collision theory, frontal collision, oblique reflection, and Mach reflection during detonation wave propagation were studied. The results show that the maximum detonation pressure at the Mach reflection point where the incident angle is 46.9° is three times larger than the value of the explosive complete detonation. Then, in order to analyze the crack propagation in different initiation forms, a rock fracture test slot was designed, and the results show that bilinear initiating system can change the energy distribution of explosives. Finally, field experiment was implemented at the hard rock pile blasting engineering, and experimental results show that the present system possesses high explosive energy utilization ratio and low rock fragments size. The results of this study can be used to improve the efficiency in hard rock blasting.

Numerical modelling of underwater detonation of non-ideal condensed-phase explosives

The interest in underwater detonation tests originated from the military, since the expansion and subsequent collapse of the explosive bubble can cause considerable damage to surrounding structures or vessels. In military applications, the explosive is typically represented as a pre-burned material under high pressure, a reasonable assumption due to the short reaction zone lengths, and complete detonation of the unreacted explosive. Hence, numerical simulations of underwater detonation tests have been primarily concerned with the prediction of target loading and the damage incurred rather than the accurate modelling of the underwater detonation process. The mining industry in contrast has adopted the underwater detonation test as a means to experimentally characterise the energy output of their highly non-ideal explosives depending on explosive type and charge configuration. This characterisation requires a good understanding of how the charge shape, pond topography, charge depth, and additional charge confinement affect the energy release, some of which can be successfully quantified with the support of accurate numerical simulations. In this work, we propose a numerical framework which is able to capture the non-ideal explosive behaviour and in addition is capable of capturing both length scales: the reaction zone and the pond domain. The length scale problem is overcome with adaptive mesh refinement, which, along with the explosive model, is validated against experimental data of various TNT underwater detonations. The variety of detonation and bubble behaviour observed in non-ideal detonations is demonstrated in a parameter study over the reactivity of TNT. A representative underwater mining test containing an ammonium-nitrate fuel-oil ratestick charge is carried out to demonstrate that the presented method can be readily applied alongside experimental underwater detonation tests.

Gas gun for dynamic loading of explosives

There has long been a need to understand the impact response of explosive materials, and continual improvements result from the design of careful, well-instrumented experiments. This article summarizes details of the design and construction of a laboratory facility capable of launching projectiles at explosive targets at velocities up to 1500 m s−1. There are two types of experiment that are required. In the first, a gun launches a plate of great planarity at an equally flat target. This geometry is known as plate impact and a target loaded in this manner experiences a state of one-dimensional strain. This loading is accomplished by launching plane impactors onto targets aligned to micron tolerances, normal to the impact axis to less than 0.5 mrad of tilt. In the second, it is required to attain the ability to recover impacted explosive targets that have been loaded in one-dimensional strain for subsequent microstructural assessment. The development of this capability will be described in a subsequent publication. The system is capable of containing reactive targets, where design must allow for complete detonation of the target (up to 250 g of explosive). The facility has been completed, is operational, and has been approved for use by the appropriate authorities. An example of a particle velocity sensor in use within a plastic-bonded explosive is given as illustration.

A gas gun for plane and shear loading of inert and explosive targets

The design and construction of a 75 mm bore laboratory gas gun capable of velocities up to 500 m s−1 is described. The performance of the gun is compared with the analytical interior ballistics model of Pidduck and Kent [A. E. Seigel, Report No. AGARDograph 91 (1965)]. The gun is constructed for two idealized loading geometries. One is plate impact, in which the loading is in one-dimensional strain, accomplished by impacting plane impactors onto targets aligned to micron tolerances, precisely normal to the impact axis. Another is pressure-shear in which the target and impacting plate are angled, but still aligned to the same tolerances. The system requires flexibility for addressing the problem of reactive targets when design must allow complete detonation of the target (up to 250 g). This has been accomplished and the system approved for use by the appropriate authorities.

Chemical-kinetic descriptions of high-temperature ignition and detonation of acetylene-oxygen-diluent systems

High-temperature oxidation of acetylene, above about 1000 K, is addressed numerically and theoretically. A new detailed-chemistry description is employed that involves 114 elementary steps among 28 chemical species, revising questionable rate parameters for certain elementary steps, notably concerning OH and O 2 attack on C 2H 2. It proceeds most importantly through ketyl at the highest temperatures and vinyl at lower temperatures, and it is shown to yield reasonable agreement with shock-tube ignition results. A short mechanism of 21 steps, 4 of which are reversible, among 15 species, is derived from the detailed-chemistry description by sensitivity and reaction-path analyses, for use above a temperature that increases with pressure and that is about 1200 K at 1 bar. Through systematic application of steady-state and partial-equilibrium approximations, a seven-step reduced mechanism is derived from the short mechanism, involving four steps that are important during the induction process leading to ignition and three that are important during the slower further heat release that follows ignition. The four induction steps are an example of branched-chain thermal-explosion chemistry. They are simplified systematically to a one-step approximation from which an explicit formula is derived determining the ignition time, in good agreement with predictions of the short and reduced mechanism. By treating the three slow heat-release steps as a one-step recombination-controlled process, a two-step approximation is then obtained for the complete detonation. These various levels of description of acetylene ignition and detonation chemistry can be helpful in computational and theoretical studies of high-temperature ignition and detonation behavior of fuels that contain or produce appreciable amounts of acetylene.

Detonation Products as a Function of Initiation Strength, ambient gas and binder systems of explosives charges

AbstractThe way of initiating an insensitive high explosive can influence the start of a detonation reaction remarkably. In order to study the extent of this influence, different boosters and different booster structures for the initiation of explosive mixtures containing TNT and nitroguanidine (NQ) have been used. The experiments have been conducted in a 1.5 m3 containment from which the detonation products could be taken and analyzed. In those cases where we only used a 10 g RDX booster together with a detonation cap no. 8, we had not a complete detonation reaction by initiating cylindrical charges of TNT/NQ and TNT/AN. This means that unreacted TNT was analyzed in the solid residue, mainly consisting of carbon soot. On the other hand, we had a complete detonation using an additional booster of about 18 g detonation sheet, placed on the front side of the cylindrical explosive, having the same diameter as the explosive charge.Another part of the investigations deals with the determination of the influence of different argon pressures on the composition of the detonation gas and the solid residue. Between vacuum and one bar argon a strong change not only of the gas but also of the soot residue was measured. A stronger influence on the products was found using a confinement with glass tubes.The investigation of Al‐containing charges exhibited a very different behavior compared with charges without Al. No more influence of vaccum or of different ambient gas pressure could be observed. By investigation of two composite explosive charges (PBX) containing binder systems of different energies and different oxygen balances, a great influence on the reaction of Al was found. The PBX charges with the better O2‐balance containing the energetic GAP‐binder reacted nearly completely with the Al, opposite to the charge containing the polyisobutylene (PIB) binder system.

The initiation of condensed explosives by shock waves from metals

When a shock wave is transmitted from a metal to a solid explosive a pure shock wave is transmitted into the explosive. The shock generally builds up to a complete detonation wave but in some cases it fails to initiate the explosive. In the former case an effective delay time in the initiation of the explosive is observed. Initiation delays have been measured in 2 in. diam. sticks of 60/40 RDX/TNT as a function of incident shock strength in mild steel and aluminium .