Effects Of Material Properties Of Warhead Casing On Natural Fragmentation Performance Of High Explosive (He) Warhead (original) (raw)
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Journal of KONES. Powertrain and Transport, 2016
The article presents results of the numerical analyses of the fragmentation warhead, which is one of the key elements of the missile used to combat anti-tank missiles. The fragmentation warhead is composed of such elements as outer casing, inner casing, explosive material and fragmentation liner. The fragmentation liner is built from steel spheres or cylinders embedded in epoxy resin. As a result of the explosive material detonation the pressure wave is generated, which affects the liner, causes its fragmentation, and drives each splinter. In order to perform numerical analyses the model of the cylindrical fragmentation warhead with a diameter of 80 millimetres and a length of 100 mm was prepared. The fragmentation liner consists of steel spheres with a diameter of 5 mm. It was assumed in simulation that the detonating material is the plastic explosive C4. The influence of the position of the explosive charge detonation initiation point of the fragmentation warhead on its effectiveness was studied. Effectiveness was evaluated by measuring the maximum speed obtained by the fragments and their spatial distribution. A threedimensional model of the studied system has been prepared using the MSC Patran software and the numerical analyses were performed using the finite element method with explicit scheme of the time integration implemented in the LS-Dyna solver. To model gas domain Arbitrary Lagrangian-Eulerian (ALE) method was used and interaction between gas and solid body was modelled with FSI coupling.
Influencing Parameters on He Projectiles with Natural Fragmentation
Design of the HE warhead is process confronted with series of contradictory requirements. Influence of warhead design on lethal efficiency is very complex. Lethal efficiency of HE warhead depends on the form and dimension of the warhead, quantity and type of explosive, warhead case material, warhead case thickness, fuse type, explosive train etc. At warheads natural fragmentation, fragments geometry, their mass and spatial distribution are functions of designed shape of the warhead case (shell), mechanical properties of case material (tensile strength and yield strength) and performances of explosive (physical and energetic). It is essential to have a capability to make warhead performance predictions in the earliest phases of ammunition or warheads preliminary design.
Comparison of Lethal Zone Characteristics of Several Natural Fragmenting Warheads
Research of HE warheads lethal zone is very complex topic because of large number of controlled and independent, sometimes correlated, influencing factors. Capability for prediction of lethal zone is based on complexity of databases regarding natural fragmentation parameters, which should contain data about warhead body material characteristics, types of explosive charge, number, mass, initial velocity and spatial distribution of fragments, battlefield terrain, distribution of soldiers on battlefield, etc. Based on experimental research (fragmentation test in Arena facilities with two types of artillery projectiles and two types of rocket warheads), analytical and numerical methods used -projectiles lethal zones are predicted and analyzed. Influence of projectile design and explosive charges on warhead lethal zone is analyzed.
Brazilian Journal of Chemical Engineering
The wide usage of TNT as a main charge for fragmentation shells has been eliminated due to its lower performance and exudation on the fuze thread and relevant safety measures inconvenience. These disadvantages have not become accepted anymore due to the desired safety requirements and the limited efficiency of the TNT, especially when different new explosives are introduced into researches. This research studies the fragmentation calculations of the 120 mm high explosive shell when its is loaded with different explosives rather than TNT. Different explosives have been used in the current research include the melt cast compositions such as Octol and composition B, a cast cured composition based on RDX with HTPB polymer matrix and the plastic explosive composition HMX-silicone. The fingerprint of the fragmentation pattern of each shell loaded with different explosive has been obtained using Autodyn smooth particle hydrodynamic (SPH) algorithm, whose numerical model has been validated ...
Lethal Influence Factors of Natural and Preformed Fragmentation Projectiles
DAAAM International Scientific Book, 2015
Low intensity warfare had many impact on reducing logistic costs during field operations. It influenced the development of new large caliber HE projectiles. Concerning increasing lethal efficiency at target, the focus is at development of modern projectiles with natural, embossed and preformed fragmentation. Modern natural fragmentation projectiles characterize excellent aerodynamic properties, use of high strength steel with high fragmentation characteristics and denser high energy materials. Artillery projectiles with preformed fragments are usually equipped with large amount of preformed spherical or cubical fragments made of steel or tungsten. Modern unguided rocket warheads are based on embossed fragmentation or preformed warheads concept. There are limited data about real lethal effects of these projectiles. This paper presents available data and research results of embossed fragmentation warhead 122 mm and prefragmented warhead 128 mm, which are conducted in Bosnia and Herzegovina.
Characterization of distribution parameters of fragment mass and number for conventional projectiles
Assessment of parameters of high explosive (HE) projectile fragmentation process (mass distribution and number of fragments) in most of the scientific papers is generally best de-scribed using Mott (depending on dimensionality and different scaling models) and Held equations. These methods can describe mass distribution of fragments excellent, but pre-cise data about individual parameters from these equations are not available in public lit-erature. During the previous eksperimental research of natural fragmentation for several types of HE projectiles, authors are studied the effects of several types of projectile body materials, two types of high explosive and projectile design and determined range of pa-rameters using in Held laws. Obtained data can help designers with smaller experimental experience to make faster prediction of new projectile fragmentation parameters.
Fem Simulation Of He Blast-Fragmentation Warhead And The Calculation Of Lethal Range
2012
This paper presents the simulation of fragmentation warhead using a hydrocode, Autodyn. The goal of this research is to determine the lethal range of such a warhead. This study investigates the lethal range of warheads with and without steel balls as preformed fragments. The results from the FE simulation, i.e. initial velocities and ejected spray angles of fragments, are further processed using an analytical approach so as to determine a fragment hit density and probability of kill of a modelled warhead. In order to simulate a plenty of preformed fragments inside a warhead, the model requires expensive computation resources. Therefore, this study attempts to model the problem in an alternative approach by considering an equivalent mass of preformed fragments to the mass of warhead casing. This approach yields approximately 7% and 20% difference of fragment velocities from the analytical results for one and two layers of preformed fragments, respectively. The lethal ranges of the si...
Simulation of natural fragmentation of rings cut from warheads
Defence Technology, 2015
Natural fragmentation of warheads that detonates causes the casing of the warhead to split into various sized fragments through shear or radial fractures depending on the toughness, density, and grain size of the material. The best known formula for the prediction of the size distribution is the Mott formulae, which is further examined by Grady and Kipp by investigating more carefully the statistical most random way of portioning a given area into a number of entities. We examine the fragmentation behavior of radially expanding steel rings cut from a 25 mm warhead by using an in house smooth particle hydrodynamic (SPH) simulation code called REGULUS. Experimental results were compared with numerical results applying varying particle size and stochastic fracture strain. The numerically obtained number of fragments was consistent with experimental results. Increasing expansion velocity of the rings increases the number of fragments. Statistical variation of the material parameters influences the fragment characteristics, especially for low expansion velocities. A least square regression fit to the cumulative number of fragments by applying a generalized Mott distribution shows that the shape parameter is around 4 for the rings, which is in contrast to the Mott distribution with a shape parameter of ½. For initially polar distributed particles, we see signs of a bimodal cumulative fragment distribution. Adding statistical variation in material parameters of the fracture model causes the velocity numerical solutions to become less sensitive to changes in resolution for Cartesian distributed particles.
Journal of KONES. Powertrain and Transport, 2014
Military vehicles active protection systems against cumulative missiles are designed to destroy the attacking missile before it hits the vehicle armour. The article presents the results of numerical studies of one of the elements of active protection system, which is the fragmentation destructor. A typical directed fragmentation warhead consists of a few parts: metallic or composite case, explosive material and fragmentation elements in the form of spheres, cylinders. The authors of this study evaluated the influence of the destructor case type-in particular material-on the effectiveness of the destructor. The effectiveness was evaluated on the basis of the maximum speed of balls. Evaluation was performed for the selected balls from each layer. Numerical calculations were performed for two materials of the case: steel and aluminum. It was assumed in simulation that the detonating material is the plastic explosive C4. The numerical analyses were based on the finite element method with the explicit time integration method implemented in the Ls-Dyna program. The interaction of solid and gaseous medium has been modelled using ALE coupling. Mechanical properties of the case were described using a simplified Johnson-Cook type material. The detonation process was described using programmed burn model approximations, and the behaviour of detonation products was described with the JWL (John, Wilkins, Lee) equation.
Real-time simulation of a fragmenting explosion for cylindrical warheads
journal of defense modeling and simulation, 2021
Explosion models based on finite element analysis (FEA) can be used to simulate how a warhead fragments. However, their execution times are extensive. Active protection systems need to make very fast predictions, before a fast attacking weapon hits the target. Fast execution times are also needed in real-time simulations where the impact of many different computer models is being assessed. Hence, FEA explosion models are not appropriate for these real-time systems. As a trade-off between accuracy and execution time, this paper creates a simulation of fragments from a warhead's explosion, using simple analytical equations. The results are verified against explosion experimental data and FEA results. The developed model then can be made available for real-time simulation and fast computation.