Explosive Forming Research Articles

Penetration Evaluation of Explosively Formed Projectiles Through Air and Water Using Insensitive Munition: Simulative and Experimental Studies

The process of formation, flying, penetration of explosively-formed projectiles (EFP) and the effect of water on performance of the charge for underwater applications is simulated by Ansysis Autodyn 2D-Hydro code. The main objective of an explosively formed projectile designed for underwater applications is to disintegrate the target at longer standoff distances. In this paper we have simulated the explosively formed projectile from OFHC-Copper liner for 1200 conical angle. The Affect of water on the penetration of EFP is determined by simulations from Ansysis Autodyn 2-D Hydrocode and by varying depth of water from 1CD-5CD. The depth of penetration against steel target is measured experimentally. Flash X-Ray Radiography (FXR) is used to capture EFP jet formation and its penetration against target is measured by depth of penetration experiments. Simulation results are compared with experimental results. The difference in simulated and experimental results for depth of penetration is about 7 mm, which lies within favorable range of error. The jet formation captured from FXR is quite clear and jet velocity determined from Flash X-ray radiography is the same as the ones obtained by using other high explosives. Therefore, it is indicated that Insensitive Munition (8701) can be utilized instead of Polymer Bonded Explosives (PBX) for air and underwater environments with great reliability and without any hazard.

Design and Sensing Properties of a Self‐Assembled Supramolecular Oligomer

AbstractSupramolecular polymers are a class of macromolecules stabilized by weak non‐covalent interactions. These self‐assembled aggregates typically undergo stimuli‐induced reversible assembly and disassembly. They thus hold great promise as so‐called functional materials. In this work, we present the design, synthesis, and responsive behavior of a short supramolecular oligomeric system based on two hetero‐complementary subunits. These “monomers” consist of a tetrathiafulvalene‐functionalized calix[4]pyrrole (TTF‐C[4]P) and a glycol diester‐linked bis‐2,5,7‐trinitrodicyanomethylenefluorene‐4‐carboxylate (TNDCF), respectively. We show that when mixed in organic solvents, such as CHCl3, CH2ClCH2Cl, and methylcyclohexane, supramolecular aggregation takes place to produce short oligomers stabilized by hydrogen bonding and donor–acceptor charge‐transfer (CT) interactions. The self‐associated materials were characterized by 1H NMR and UV/Vis/NIR absorption spectroscopy, as well as by concentration‐ and temperature‐dependent absorption spectroscopy and dynamic light scattering (DLS) analyses of both the monomeric and oligomerized species. The self‐associated system produced from TTF‐C[4]P and TNDCF exhibits a concentration‐dependent aggregation behavior typical of supramolecular polymers. Further support for the proposed self‐assembly came from theoretical calculations. The fluorescence emitting properties of TNDCF are quenched under conditions that promote the formation of supramolecular aggregates containing TTF‐C[4]P and TNDCF. This quenching effect has been utilized as a probe for the detection of substrates in the form of anions (i.e., chloride) and nitroaromatic explosives (i.e., 1,3,5‐trinitrobenzene). Specifically, the addition of these substrates to mixtures of TTF‐C[4]P and TNDCF produced a fluorescence “turn‐on” response.

EBSD analysis of plastic deformation of copper foils by flexible pad laser shock forming

Flexible pad laser shock forming (FPLSF) is a new mold-free microforming process that induces high-strain-rate plastic deformation in thin metallic foils using laser-induced shock pressure and a hyperelastic flexible pad. This paper studies the plastic deformation behavior of copper foils formed through FPLSF by investigating surface hardness and microstructure. The microstructure of the foil surface before and after FPLSF is analyzed by electron backscatter diffraction technique using grain size distribution and grain boundary misorientation angle as analysis parameters. The surface hardness of the craters experienced a significant improvement after FPLSF; the top crater surface being harder than the bottom surface. The microstructure of the copper foil surface after FPLSF was found to be dominated by grain elongation, along with minor occurrences of subgrain formation, grain refinement, and high dislocation density regions. The results indicate that the prominent plastic deformation mechanism in FPLSF is strain hardening behavior rather than the typical adiabatic softening effect known to be occurring at high-strain-rates for processes such as electromagnetic forming, explosive forming, and laser shock forming. This significant difference in FPLSF is attributed to the concurrent reduction in plastic strain, strain rate, and the inertia effects, resulting from the FPLSF process configuration. Correspondingly, different deformation behaviors are experienced at top and bottom surfaces of the deformation craters, inducing the change in surface hardness and microstructure profiles.

Solve thermal explosion model by central difference and Newton iteration method

In this paper, the general equation form of a thermal explosion in a vessel with boundary values is firstly presented, later the central difference method and Newton iteration method are used to solve the relevant partial differential equations in one-dimensional and two-dimensional forms, finally the order of convergence of the numerical scheme is verified by numerical experiments and the experiment results are provided.

Solve thermal explosion model by central difference and Newton iteration method

In this paper, the general equation form of a thermal explosion in a vessel with boundary values is firstly presented, later the central difference method and Newton iteration method are used to solve the relevant partial differential equations in one-dimensional and two-dimensional forms, finally the order of convergence of the numerical scheme is verified by numerical experiments and the experiment results are provided.

The soft and hard X-rays thermal emission from star cluster winds with a supernova explosion

Massive young star clusters contain dozens or hundreds of massive stars that inject mechanical energy in the form of winds and supernova explosions, producing an outflow which expands into their surrounding medium, shocking it and forming structures called superbubbles. The regions of shocked material can have temperatures in excess of 10$^6$ K, and emit mainly in thermal X-rays (soft and hard). This X-ray emission is strongly affected by the action of thermal conduction, as well as by the metallicity of the material injected by the massive stars. We present three-dimensional numerical simulations exploring these two effects, metallicity of the stellar winds and supernova explosions, as well as thermal conduction.

Topological bifurcations of minimal invariant sets for set-valued dynamical systems

We discuss the dependence of set-valued dynamical systems on parameters. Under mild assumptions which are often satisfied for random dynamical systems with bounded noise and control systems, we establish the fact that topological bifurcations of minimal invariant sets are discontinuous with respect to the Hausdorff metric, taking the form of lower semi-continuous explosions and instantaneous appearances. We also characterise these transitions by properties of Morse-like decompositions.

Influence of Liner Material on Formation of Multiple Explosively Formed Projectiles Warhead Parameters

The law of influenced material of liner is researched by numerical simulation.Multiple explosively formed projectiles (MEFP) forming process is numerically simulated with different liner material,such as copper, aluminum, iron and so on.The law that the formation parameters of MEFP such as velocity, length-diameter ratio and radial dispersion angle,influenced by the density and ductility of liner material is educed.It reaches the conclusion that the velocity and radial dispersion angle of projectiles decreases 58% and 56% with the increasing density of the liner material; the length-diameter ratio of central projectile increases276%with the increasing ductility of the liner material, so in order to acquire good formation of MEFP parameters, the appropriate density and higher ductility should be chosen.

Dynamic Behaviors of Multi-Layered Steel Targets with Air Gaps Subjected to the Impact of EFP Simulants

Experiments and fine three-dimensional FE analyses were carried out to study the behaviors of multi-layered steel targets with air gaps subjected to normal and oblique impact of EFP (Explosively Formed Projectile) simulants. The experiments were performed using the EFP simulants with hemispherical nose that impact the targets vertically at a striking velocity of 1290m/s, while the armor shields consisted of multi 6mm-thick layers made of Q235 steel materials. The damage pattern and damage area of the targets as well as the residual velocities of EFP simulants in the experiments are presented in this paper. Systematic FE analyses on the perforation process of the experiments were conducted using the explicit finite element code LS-DYNA accompanied by the Johnson-Cook elasto-viscoplastic model. A good agreement is generally obtained between the numerical and experimental results. To further and better understand the whole process of fracture development and perforation of the layered steel targets induced by the impact of EFP simulants, the influence on obliquity angles during the impact and perforation process of EFP simulants were also investigated. The referred impact obliquity angle is varied from 5° to 40°. The result indicates that the residual velocities of EFP simulants decreased significantly with the increase of obliquity angle, and to some extent, a larger impact obliquity angle may result in the ricochet of EFP simulants.

Simulation on deforming progress and stress evolution during laser shock forming with finite element method

Laser shock forming (LSF) employs laser shock wave to form metal sheet, which is similar to explosive forming. Finite element method (FEM) is an effective method to better understand mechanism of LSF and select appropriate parameters to shape metal sheet accurately with LSF. In this paper, FEM analysis model is developed to simulate LSF, which includes how to determine the pressure loading, material constitutive model, and solution time. The commercial code LS-DYNA is applied to simulation. A sequence of dynamic deformation behaviors of metal sheet at the end of different periods are presented and discussed in detail, and the peculiar phenomena in dynamic deformation processing are discovered, which do not appear in the traditional forming processing. The final static deformation and residual stress are also predicted. The predicted results are accordance with the experimental data.

Topology Optimization of an Asymmetric Elliptical Cone Subjected to Blast Loading

This paper describes a numerical procedure for the blank shape design of thin aluminum components achieved by explosive forming. The objective is to specify the initial blank shape considering the geometry of the final product. The numerical procedure consists of three steps: At first, the forming process of an asymmetric blank in an elliptical cone die cavity and without blank holder is simulated. To rectify the wrinkles without optimization the square of the primary blank will be increased. In the next step, topology optimization is employed to obtain the optimum geometry of the blank whose diameter has been increased finally, the modified blank achieved previous step is used in the new simulation to check whether or not the wrinkles mentioned in first step has been rectified. Results show the proposed numerical procedure can provide the optimal blank shape in a few iterations.

Stellar feedback in molecular clouds and galactic discs

Feedback from massive stars in the form of stellar winds, ionizing radiation, and Supernova explosions shapes the structure and dynamics of the multi-phase interstellar medium. Here, I will briefly summarise some of our recent studies and findings on these subjects. I will discuss the effects of ionizing radiation and stellar winds in individual molecular clouds. Furthermore, I will shortly introduce the SILCC project, in which we model the evolution of the Supernova- and wind-driven, multi-phase ISM in stratified galactic discs.

High-performance thermal capacitors made by explosion forming

This paper addresses the thermal testing of UniPore–paraffin composites for use as thermal capacitors. UniPore is a relatively new porous material with unidirectional pores formed by the explosive fusion of multiple thin copper pipes filled with paraffin. The current study investigates the suitability of this composite for transient thermal energy storage. The application demands both high thermal diffusivity and a large specific energy storage capacity. These requirements are met by the highly conductive copper and the phase change material paraffin, respectively. Combined experimental and numerical analyses are conducted towards the determination of temperature stabilization performance. Furthermore, key geometric criteria for the design of optimum UniPore structures as thermal capacitors are identified.

Improving battery safety by early detection of internal shorting with a bifunctional separator.

Lithium-based rechargeable batteries have been widely used in portable electronics and show great promise for emerging applications in transportation and wind-solar-grid energy storage, although their safety remains a practical concern. Failures in the form of fire and explosion can be initiated by internal short circuits associated with lithium dendrite formation during cycling. Here we report a new strategy for improving safety by designing a smart battery that allows internal battery health to be monitored in situ. Specifically, we achieve early detection of lithium dendrites inside batteries through a bifunctional separator, which offers a third sensing terminal in addition to the cathode and anode. The sensing terminal provides unique signals in the form of a pronounced voltage change, indicating imminent penetration of dendrites through the separator. This detection mechanism is highly sensitive, accurate and activated well in advance of shorting and can be applied to many types of batteries for improved safety.

Mach Wave Control in Explosively Formed Projectile Warhead

AbstractA Mach wave emerges at the top of the liner when a wave shaper is embedded in charge, and thus seriously breaks the explosively formed projectile (EFP) nose. Thus, to avoid breakage at the EFP nose, the pressure behind the Mach wave should be controlled. An analytical model for calculating Mach wave parameters is presented based on three‐shock theory. The parameters of Mach waves, such as their growth angles and radii, their velocity along the plane of symmetry, and the pressure behind them, can be determined. Calculation results show that when the diameter of the wave shaper is reduced or the distance between the wave shaper and liner increases, the incident angle of the detonation wave at the top of the liner increases and thereby lowers the pressure behind the Mach wave. Avoiding the occurrence of Mach waves by reducing the incident angle fails to avoid breakage at the nose of the EFP, but lowering the pressure behind the Mach wave by increasing the incident angle avoids breakage at the nose of the EFP. Calculation and simulation results are validated through X‐ray imaging experimentation.

Monte-carlo simulation of the oscillatory dynamics of a catalytic reaction with lateral interactions

We consider a stochastic simulation model of the NO+CO reaction on the (100) face of a platinum single crystal. We investigate the mechanism that gives rise to self-exciting oscillations at the micro level. The system dynamics is calculated using the multilevel kinetic Monte-Carlo method in real time. A grid with several millions of points is used. We show that the reason for the appearance of oscillations is lateral interactions in the adsorbate layer, which speed up the reaction and slow down the desorption processes. The reaction occurs in the form of a periodic surface explosion; as a result, the adsorption layer either fills almost the entire surface or is almost completely stripped from the surface. We investigate the effect of the migration rate on the realization of kinetic oscillations in the microscopic model. Analysis of films from the surface of the lattice model has shown that in the course of the observed reaction "eddies" are constantly born and destroyed in different parts of the surface. With certain special initial conditions, the model leads to excitation of plane traveling and spiral waves.

The Study of LEFP Based on One Part of Semicircle Liner

In order to obtain the forming and the velocity of LEFP(Linear Explosively Formed Penetrators) based on one part of semicircle liner, the X-ray radiography and test velocity technology are used to obtain the forming and velocity of LEFP. In this paper, an analytical approach to describe the two-dimensional liner motion of LSCs is addressed firstly at a detonation-point. The relationship of LEFP flight distance can approximate a linear equation to estimate the distance of LEFP before contacting target. Experimental results showed that the shape of LEFP likes a scimitar according to gray image, and LEFP can close around linear explosive charge length axis direction.

Achieving convergence between a community-based measure of explosive anger and a clinical interview for intermittent explosive disorder in Timor-Leste

BackgroundThere is growing research interest in understanding and analyzing explosive forms of anger. General epidemiological studies have focused on the DSM-IV category of Intermittent Explosive Disorder (IED), while refugee and post-conflict research have used culturally-based indices of explosive anger. The aim of this study was to test the convergence of a culturally-sensitive community measure of explosive anger with a structured clinical interview diagnosis of IED in Timor-Leste, a country with a history of significant mass violence and displacement. MethodsA double-blind clinical concordance study was conducted amongst a stratified community sample in post-conflict Timor-Leste (n=85) to compare a community measure of anger against the Structured Clinical Interview (SCID) module for IED. ResultsClinical concordance between the two measures was high: the area under the curve (AUC) index was 0.90 (95% CI: 0.83–0.98); sensitivity and specificity were 93.3% and 87.5% respectively. LimitationsResponse rates were modest due to the participant's time commitments. ConclusionsIt is possible to achieve convergence between culturally-sensitive measures of explosive anger and the DSM-IV construct of IED, allowing comparison of findings across settings and populations.

A Method of Explosive Forming Process for Making a Palm and a Back of Human Hand

t is well known as an important merit of the explosive forming process that the delicate figure of the die surface is precisely transferred onto the specimen of a thin metal plate, because the plate is strongly pressed against the die by the very high pressure of underwater shock wave. However, we cannot find any examples of work pieces making the best use of the merit in literatures until now. We tried to form explosively a thin copper plate into shapes of a palm and a back of human hand, as a work piece making the best use of the merit. The palm has many small delicate lines such as fingerprints and the back has interesting figures such as loose skin at the joints of fingers and the borders of fingernails. The object of the present investigation is to make work pieces just like to a real hand. In this investigation, the following process is adopted in order to perform successfully explosive forming ; real hand plaster concave model convex model of Duplicone (material for dental impression) die of Ren Cast (a kind of epoxy resin) explosive forming. Annealed copper plates of 0.3 mm thick were used in the experiments. Since the extension limit of the plate is not so large, the plate is apt to be broken. If the plate is broken, the die is modified not to break the plate. Though the die made of epoxy resin is too hard to be modified, the plaster model can be easily modified with a cutter knife or a chisel. The modified die is obtained through model of Duplicone made by using the modified plaster model. After a few times of repeating modification, the breakage of plate was scarcely produced. On the work piece of palm, a lot of small lines including finger prints clearly appeared and the work piece of the back showed the shape just like to real human hand.

Study on the Effects of Shock Wave Propagation on Explosive Forming

Explosive forming is one of the unconventional techniques, in which, most commonly, the water is used as the pressure transmission medium. The explosive is set at the top of the pressure vessel filled with water, and is detonated by an electric detonator. The underwater shock wave propagates through the water medium and impinges on the metal plate, which in turn, deforms. There is another pressure pulse acting on the metal plate as the secondary by product of the expansion of the gas generated by detonation of explosive. The secondary pressure pulse duration is longer and the peak pressure is lower than the primary shock pressure. However, the intensity of these pressure pulse is based also on the conditions of a pressure vessel. In order to understand the effects of the configuration of the pressure vessel on the deformation of a metal plate, numerical simulation was performed. This paper reports those results.