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The insufficient recognition of injuries by the BB-gun (regarded as toys for children) has led to its increasing misuse without permission, which has caused many public safety issues. Aiming to enhance the understanding of the injuries by the BB-gun, the experimental and numerical study of BB-Gun pellet penetrating "cowhide + gelatine" composite target was comprehensively carried out. It was confirmed from the experiment that BB-Gun is capable of inflicting severe or fatal wounds to important organs, and perforating the skin or not could be employed to evaluate the safety of BB-guns. Moreover, three forms of ballistic limit (including: velocity, kinetic energy and specific kinetic energy) of typical BB were calculated and analyzed by reasonably validated numerical simulation method. Additionally, a formulation was acquired by dimensional analysis based on the simulation results and was verified to accurately predict the ballistic limit velocity of BB with different mechanical properties. The method may help to improve the understanding on the minimal velocity needed to perforate skin and may be advised as the determination of the safety of BB-gun. [ABSTRACT FROM AUTHOR]

Hypervelocity impact dynamics is the theoretical support of spacecraft shielding against space debris. The numerical simulation has become an important approach for obtaining the ballistic limits of the spacecraft shields. Currently, the most widely used algorithm for hypervelocity impact is the smoothed particle hydrodynamics (SPH). Although the finite element method (FEM) is widely used in fracture mechanics and low-velocity impacts, the standard FEM can hardly simulate the debris cloud generated by hypervelocity impact. This paper presents a successful application of the node-separation technique for hypervelocity impact debris cloud simulation. The node-separation technique assigns individual/coincident nodes for the adjacent elements, and it applies constraints to the coincident node sets in the modeling step. In the explicit iteration, the cracks are generated by releasing the constrained node sets that meet the fracture criterion. Additionally, the distorted elements are identified from two aspects – self-piercing and phase change – and are deleted so that the constitutive computation can continue. FEM with the node-separation technique is used for thin-wall hypervelocity impact simulations. The internal structures of the debris cloud in the simulation output are compared with that in the test X-ray graphs under different material fracture criteria. It shows that the pressure criterion is more appropriate for hypervelocity impact. The internal structures of the debris cloud are also simulated and compared under different thickness-to-diameter ratios ( t / D ). The simulation outputs show the same spall pattern with the tests. Finally, the triple-plate impact case is simulated with node-separation FEM. [ABSTRACT FROM AUTHOR]

Abstract: Experimental, analytical and numerical simulations were performed to study the ballistic resistance of 6061-T6 aluminium plates subjected to a normal impact of small calibre armour piercing bullets. Two types of bullets were used, steel and tungsten carbide core bullets. Three plate thicknesses, 101.6 mm, 76.2 mm and 25 mm, were considered. Bullets were impacted at ordnance velocity thus results range from deep penetration to complete perforation with residual velocity. Ballistic results, deformations of the plates and of the bullets are discussed and reproduced through numerical simulations using both LS-DYNA and ABAQUS solvers; analytical models by means of a cavity expansion approach are also used. Exploiting analytical and numerical models the ballistic behaviour of the two bullets on the three plates is discussed with emphasis on the capability of the models to reproduce the physical features of the phenomena. X-ray diffraction measurements for the residual stress patterns of the plate's surface were also performed on all of the plates both before and after the tests and the experimental measurements are compared with the numerical model results. A specific discussion about tungsten carbide core bullet behaviour is reported highlighting the importance of the sabot in the impact phenomena. Although the work focuses on monolithic plates, the results and discussion can be of interest for the design of optimised multilayer armour shields. [Copyright &y& Elsevier]

Abstract: Whipple shield is widely used on manned spacecraft, numerical simulation is an important way for obtaining the ballistic limit. The large population of particles and the large space span of Whipple shield simulation model restrict the computational efficiency. A fast numerical approach is presented for Whipple shield ballistic limit analysis. First, the critical penetration analysis of the rear walls is converted into specific impulse analysis delivered by the secondary debris cloud, because the maximum of specific impulse is the main determinant of the penetration. The dual plate simulation model is then converted into single plate model and the population of particles is reduced. Second, based on the isotropic expansion theory of secondary debris cloud, the specific impulse analysis is further converted into particle position and velocity analysis when the stable secondary debris formed. The space span of the simulation model is reduced. An example of Whipple shield ballistic limit analysis is provided for the verification of the fast numerical approach, it shows that this approach can significantly increase the computation efficiency with acceptable accuracy. [Copyright &y& Elsevier]

Abstract: Sphere structures for ballistic protection have rarely been studied. In this paper a novel unit cell, called Square Based Pyramid Unit Cell (SBPUC), is created as a fundamental building block of sphere structures for the purpose of ballistic protection. Although it has been proved by the other authors that the arrangement of spheres in a tapered chain is an efficient way for impact energy absorption (Sokolow A, Pfannes JM, Doney RL, Nakagawa M, Agui JH. Absorption of short duration pulses by small, scalable, tapered granular chains. Appl Phys Lett 2005;87:1–3), it is very difficult to convert this 1D concept to 3D application in reality with arbitrary tapering angle. The adoption of SBPUCs may provide a good solution. In this research, the core of a sandwiched sphere structure is build with such SBPUCs and is characterized with increasing sphere diameter, decreasing sphere thickness, and increasing sphere cap thickness. From the numerical simulation results with ABAQUS/Explicit, the sandwiched sphere structure can absorb at least 11.6% more impact energy compared with the monolithic plate with the same area density. This study might provide a potential armor design platform which makes further performance improvement possible by optimizing the large parameter space associated with material selection and structure design. [Copyright &y& Elsevier]

Abstract: The paper describes a numerical study on the perforation of sheet steel by a projectile under high impact velocity to predict the ballistic behaviour and, in particular the ballistic limit. The parametric study is performed for several of the important variables in the numerical model using Abaqus/Explicit finite element code and their effects are reported in the paper. The variables considered include the target configuration (thickness), constitutive material model of the target, mass of the projectile, friction between the projectile and the target and shape of the projectile. The effect of the material behaviour was also studied through the use of two constitutive relations and to conclude the ballistic curves were calculated for several different target materials using data from literature. The numerical results were compared with existing data sourced from the literature and an analytical model was used to compare the trend obtained using numerical simulations in terms of ballistic limit. [Copyright &y& Elsevier]

Cased telescoped ammunition (CTA) is a kind of charge structure with projectile embedded in the cartridge case. The advantages of CTA, compared with concepts using conventional ammunition, are: (1) reduced charge/ammunition volume, (2) improved performance, and (3) enhanced power and survivabillity of armament. The projectile is placed in the control tube of the cartridge before shooting. After the primer is struck, propellant product gases, generated by the igniter charge burning in the central igniter tube, drive the projectile to move forward along the control tube, and then causing the main propellants around the igniter tube and control tube to burn. Therefore, in the process of interior ballistics, there is a motion of the projectile in the control tube before the projectile engraves the rifles, in contrast with the traditional ammunition. The consistency of this motion has an important influence on the stability of CTA interior ballistic performance. The experiments on the ignition and combustion of propellants and motion of projectile in the control tube are carried out using a high-speed video recording system in this study. The projectile velocity at the entrance of the rifle is obtained from the recorded images. A two-phase flow model of CTA is also established and simulated by using the two-phase flow method and computational fluid dynamics technology. The calculated projectile velocity is in good agreement with the experimental data. The numerical results show that the developed mathematical model gives the correct trend and can provide useful calculated parameters for the structural design of CTA components. [ABSTRACT FROM AUTHOR]

Plastilina is often used as a ballistic witness material (BWM) behind the armour to evaluate the backface signature (BFS). Indeed, it is cheap, reusable and it keeps its deformation after being impacted. Moreover, while it aims at evaluating the performance of ballistic protections when no perforation occurs, it can be subjected to a very wide range of strain/shear rates during a ballistic impact. Therefore, there is a need to improve the knowledge about the mechanical/rheological response of such a material. This paper proposes both experimental and modelling approaches to determine the response of the specific ballistic plastilina red Weible® over a wide range of shear/strain rate. A capillary rheometry analysis with control of temperature was performed up to 8.104 s-1. The corrections of Rabinowitsch and Bagley were applied and an attempt of the analysis of Mooney was considered. From the rheology of plasticine, a two-parameters based power-law constitutive equation was deduced. An experimental drop test was carried out using a specific standard setup. A high-speed camera was used for measuring the penetration depth of a steel ball into the plastilina. A numerical simulation of the drop test was performed by taking into account the mechanical properties of the plastilina. A good correlation was observed between the experimental and numerical results in terms of indentation depth evolution. [ABSTRACT FROM AUTHOR]