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In this paper, the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments. Attention is paid to elucidating the influences of rod cross-section dimensions, structure height, structure layer, and rod inclination angle on the deformation mode, ballistic performances, and ability to change the ballistic direction of fragments. The results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural parameters. In this respect, structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and, consequently, ballistic performances. [ABSTRACT FROM AUTHOR]

A terminal ballistic analysis of the effects of 7.62 mm X 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study. The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea® software yielded the conclusions. The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile's core. The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results. An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study. The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile's performance. [ABSTRACT FROM AUTHOR]

A methodology is developed based on the coupling of a finite element code with an optimisation module for the design of land vehicle armouring composed of lightweight aluminium alloy and high strength steel plate. Following an experiment/simulation correlation, a numerical model has been built and calibrated considering monolithic plates and then verified considering a bi-metal protection against tungsten carbide projectile mimicking the core of a 7.62x51 AP8 ammunition. In addition, a method is proposed to obtain the vres - vi curve for the full 7.62x51 AP8 bullet from the vres - vi curve obtained from the core only. [ABSTRACT FROM AUTHOR]

In contrast to cranial gunshot trauma, diagnosis and interpretation of gunshot trauma to long bones remains difficult and controversial. The aim of this study is to review the published literature on fracture patterns resulting from gunshot trauma in human long bones, and to use the described characteristics to provide practical guidance for the forensic anthropologist. In order to achieve this, medical and forensic publications on this topic were reviewed. Several types of fractures, such as linear, oblique, comminuted and butterfly fractures, have been observed in either the shaft or the ends of long bones. Indirect fractures that are not caused by bullets striking bone directly but by bullet-induced forces to the surrounding soft tissue have been found as well. Some of these fractures are related to a specific context or mechanism which might help in the forensic reconstruction of events. It is recommended that future research should focus on available medical data to provide more detailed descriptions on fracture patterns for forensic purposes. Experimentation with bone surrogates and computer modelling might also provide better and more realistic reconstructions of gunshot trauma in the future and provide valuable insights for its diagnosis and interpretation in forensic anthropology. [ABSTRACT FROM AUTHOR]

A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized shooting experiment platform with a high-speed camera is built to observe the evolution process of such a multiphase flow field. The simulated phase distribution diagram is agreed well with the shadow photo of the experiment, indicating that the numerical model is reasonable. Further examinations of the multiphase flow fields by using the submerged and sealed launch methods show that use of the sealed launch can significantly improve the interior ballistic performance of an underwater gun. In the cases by using these two types of underwater launch methods, the displacement of the projectile within the range of the muzzle flow field meets the exponential law over time. Moreover, a not fully developed bottle-shaped shock wave is formed when t = 0.4 ms, but this bottle-shaped shock wave expands more rapidly for the sealed launch. In addition, the amplitude of pressure oscillation for the sealed launch is larger than that of the submerged launch, but the pressure oscillation of the sealed launch lasts shorter. [ABSTRACT FROM AUTHOR]

Rarefaction wave gun can significantly reduce the recoil and the barrel heat without affecting projectile velocity during the launching process. This paper aims to improve the understanding of the muzzle flow characteristics during a rarefaction wave gun firing and clarify the different ballistic behaviors between the rarefaction wave gun and the traditional gun. First, the mathematical models and the numerical methods of the muzzle flow with the interior ballistic process were established. Then, the numerical simulation results were compared with the experimental data to validate the reliability and accuracy. Next, the rarefaction wave propagation behavior was described, and the interior ballistic process of the rarefaction wave gun was compared with that of the traditional gun. Then the development law of the muzzle flow field for the rarefaction wave gun coupled with the interior ballistics process was studied. Finally, the different detailed results of the muzzle flow between the traditional gun and the rarefaction wave gun were investigated. The development processes of the muzzle flow in both guns are generally similar, but the strength of the main flow parameters and the ballistic performances for the rarefaction wave gun are smaller than that for the traditional gun due to the rarefaction wave influence. This paper could provide a valuable reference for the research and design on the rarefaction wave gun. [ABSTRACT FROM AUTHOR]

Worldwide advances in computer techniques are not yet recognised in the practice of forensic medicine. A promising application is their use in making a three-dimensional reconstruction of the crime scene. This study analyses this technique in a homicide by firearm. Queries regarding the direction and number of shots, position of the victim inside the car when shot at and presence of the accused at the crime scene were answered by a scientific model. Similar reconstruction of the scene, nailing the accused in a heinous crime, has not previously been reported as a study or a case. The paper anticipates impetus to the growth of literature in criminology and forensic sciences. It will also expedite the delivery of justice based on scientific evidence in controversial causes of death. [ABSTRACT FROM AUTHOR]

The simulation of the artillery interior and intermediate ballistics problem is performed to investigate the influence of a gas dynamics device, muzzle brake, on the muzzle hazard phenomena, such as flash and blast waves. The correlation of the chemical reactions with the characteristics of the muzzle flow field is analyzed by the simulation for a further understanding of the secondary combustion phenomenon of the muzzle flow. The novel structure of muzzle flow caused by the muzzle brake is presented by the simultaneous solution of the interior ballistics model and multi-species Navier-Stokes equations in order to analyze the influence of the muzzle brake structure on the chemical reactions. The secondary combustion of the muzzle flow due to the oxygen-supplement chemical reactions is obtained by the chemical reaction kinetic model. The interaction of the blast waves released from the muzzle brake is illustrated in detail and the mechanism of the formation of muzzle flash is analyzed. This research provides a reference for the studies on the suppression of the muzzle flash. [ABSTRACT FROM AUTHOR]

Highlights • Ballistic impact tests on 4 mm thick Weldox 700 E steel plates struck by blunt rigid projectiles were conducted and a failure mode of shear plugging was identified in the tests. • The strength and fracture models of the steel were calibrated using a hybrid experimental-numerical method. • FE simulations were carried out by using either a modified version of the Johnson-Cook (MJC) fracture criterion or the Lode dependent Modified Mohr–Coulomb (MMC) fracture criterion. • FE simulations using the MJC and MMC fracture criteria predicted almost the same ballistic performance of the targets. • For targets of Lode dependent fracture, FE simulations showed that the Lode dependent fracture criterion would predict a much lower ballistic limit for less ductile targets. However, for targets with high ductility, introducing the Lode angle into the fracture criterion would not obviously alter the ballistic limit prediction. Abstract The necessity of incorporating the Lode angle into a fracture criterion in predicting ballistic resistance of ductile metal plates has not been well elucidated so far although the ductility of a metal may be Lode dependent. In this paper, 4.0 mm thick Weldox 700 E steel plates were fired by 5.95 mm diameter blunt rigid projectiles in a one-stage gas gun in the impact velocity range of 141.2 m/s∼275.7 m/s. A failure mode of shear plugging was observed in the test and the ballistic limit was obtained by fitting the initial-residual velocity data. An axisymmetric finite element (FE) model corresponding to the test was built in ABAQUS and then was utilized to predict the ballistic resistance and fracture behavior of the targets. In the FE model, a slightly modified Johnson-Cook constitutive relation was companied by either a Lode independent modified Johnson-Cook (MJC) or the Lode dependent modified Mohr–Coulomb (MMC) fracture criterion. The plasticity and fracture of the metal were fully calibrated by a series of mechanical tests under varying stress states, strain rates and temperatures. According to the tests and parallel FE simulations, it was found that the fracture of Weldox 700 E is obviously Lode dependent. However, ballistic simulations using the MMC and MJC fracture criterion predicted very close ballistic limit velocity and similar shear plugging failure mode when compared with the test results. The dominant stress state of the material failed in the process of shear plugging was revealed by detailed FE analysis and it was found that the ductility of the metal is quite different on the dominant stress state according to the two fracture criteria. To interpret the current simulation results, further FE simulations were carried out on fictitious metals and it was found that for less ductile metallic plates the MMC fracture criterion predicts a much lower ballistic limit velocity (as much as 22%) when compared with the simulation result from the MJC fracture criterion. In contrast, for metal plates with high ductility, the simulations from the two different fracture criteria would produce quite close ballistic limit velocity predictions. [ABSTRACT FROM AUTHOR]

The viability of numerical simulations to design a solid propellant rocket motor, as opposed to static testing, is discussed in this paper. The results demonstrate that an objectively more detailed insight into the processes taking place within the motor in active combustion can be gained by employing computer simulations. The abundance of readily available computing power allows complex simulations to be run on personal desktop computers, thus, saving money by eliminating the need for static testing during the design phase of the motor. The computer simulation results are validated by a comparison with test data gathered during static tests on the motor. In this study, an RM-12K solid propellant rocket motor is designed and developed, which is currently used in real-world air defence training applications, and therefore, sufficient empirical data are available. The numerical method, based on computer simulations using personal computers, is sufficiently accurate to allow for motor design decisions and an adequate substitute for static testing. Even though a single simulation can take up to 715 h on an 8-core personal machine, it is still an effective solution. [ABSTRACT FROM AUTHOR]

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]

In the present paper, the high velocity impact of 9mm soft lead projectile on 10mm and 30mm thick Eglass/ epoxy composites was studied using a 450 kV Flash X-ray radiography (FXR) system. The basic parameters of FXR imaging, such as effect of ratio of target to film (TF) and source to target (ST) distances and X-ray penetration thickness of the composite material were optimized based on clarity and the actual dimensions of the objects. The optimized parameters were used in the FXR imaging of the ballistic event of 9mm soft projectile on E-glass/epoxy composite. The real time deformation patterns of both the projectile and composite target during the ballistic impact were captured and studied at different time intervals. The notable failure modes of the 10mm thick target with time include fibre breakage, bulging on the back side, delamination, recovery of the bulging, reverse bulging and its recovery. However, with increase in thickness of the target to 30mm the only failure mechanism observed is the breaking of fibres. The ballistic impact event was also numerically simulated using commercially available LS-DYNA software. The numerically simulated deformation patterns of the projectile and target at different time intervals are closely matching with the corresponding radiographic images. [ABSTRACT FROM AUTHOR]

A description of a pistol (rifle) cartridge often involves two ballistic coefficients that characterize its ballistic qualities with respect to various air resistance laws (ARLs). How close are the obtained ballistic trajectories with varied ARL specifications and what are the differences between them? How to evaluate ballistics if the ARLs are to be expressed in various mathematical forms? In this paper, the evaluation of external ballistics trajectories is given for two ARLs (the law brought in 1943 and the Siacci law). All the obtained results relate to the TT pistol with 7.62 × 25mm Tokarev cartridge.The paper also presents the answer to the question: how to calculate the ballistic trajectory if the ARL is expressed as a rational function, piecewise function or spline. For the 1943 ARL, a graphical interpretation of the function Cd (i, v) in the form of a surface is shown. This paper shows that, due to the selection of ballistic coefficients, it is possible to obtain sufficiently similar form of ballistic trajectories. A method of graphical comparison of external ballistic parameters is presented as well as the mathematical tools for quantitative analysis of a shape of ballistic curves.The difference between the two trajectories is proposed to be estimated using a relative error in regard to а selected ballistic parameter. Computer simulation considered for the 1943 and Siacci ARLs for the 7.62×25mm Tokarev cartridge indicates that the profiles of the function of instantaneous projectile velocity vs time of flight (TOF) had the greatest non-coincidence in relation to other ballistic parameters (e.g. horizontal range, height of the trajectory, etc.) The obtained maximum of the relative error was 0.8%. Its magnitude localizes at the point of impact. [ABSTRACT FROM AUTHOR]

A series of experiments and simulations were conducted to investigate the effects of hardness and toughness of ceramic on the ballistic performance of ceramic armour modules. The experiment was conducted using ceramics from 3M technical ceramic, using the tiles Grade T, T+, F and F+ with dimensions of 100 mm X 100 mm X 20 mm. These ceramic tiles were assessed using a simplified ceramic armour module consisting of the ceramic tile sandwiched between a cover plate and a backing plate. The test samples were made of either single tile module or multiple tile modules. They were tested against tungsten alloy long rod projectiles at a nominal velocity of 1250m/s. Experimental results showed that ballistic performance of the ceramic correlated with hardness but not fracture toughness, based on mass efficiency. Fracture toughness correlated instead with the damage radius in the ceramic. Simulation using LS-DYNA revealed that improved ballistic performance of the ceramic tiles was due to long dwell time. High fracture toughness of ceramics could suppress damage by tensile stress wave generated. [ABSTRACT FROM AUTHOR]

The paper presents mathematical modeling and computer simulation (MM&CS) in the area of numerical solving of the basic problem of external ballistics for tubed artillery. Five-stage MM&CS scheme for conducting a ballistic simulation is developed. It is shown that a formal mathematical procedure allowing to solve the basic problem of external ballistics is a numerical solution of the Cauchy problem for a system of ballistic differential equations. The trajectory of a projectile flight for the 57-mm ZIS-2 anti-tank cannon is estimated. A solving algorithm and the Mathcad program code are given.The numerical solution for a system of four first order ballistic differential equations is a five-dimensional space.The possibility of visual presentation for a numerical solution was proposed in the form of a square matrix. The boundaries of each subspace are determined. A procedure based on spline functions is developed for checking the correctness of the numerical solution. As a result of such verification, the effects of a light increase in the error at the edges of the integration interval are observed. A comparison of the numerical solution of the basic ballistics problem is conducted by means of “soft“ and “stiff“ solver-functions.The trajectory parameters estimated by “soft“ and “stiff“ methods are the same up to the fifth decimal place. [ABSTRACT FROM AUTHOR]

Although many aspects of the fracturing process of concrete are now well understood and successfully simulated with various models, it is still very difficult to properly simulate the different failure mechanisms observed in a concrete structure induced by ballistic impact. In this paper, an enhanced version of the effective-rate-dependent nonlocal damage model [Eng. Fracture Mechanics, 176 (2017)] is proposed to simulate the response of concrete in such events. Hydrostatic damage has been added to the formulation in order to take the damage of the material matrix observed while porosity reduces during compaction into account. Besides controlling the evolution of the nonlinear volumetric response of the material, this new damage variable contributes to the deterioration of the material stiffness upon confinement. It is demonstrated that the description of the nonlinear volumetric response of concrete by an equation of state (EOS) as a plasticity phenomenon, as it is commonly done in hydrodynamic constitutive modeling, is unrealistic for concrete. Such formulations fail to represent the effect of the loss of cohesion observed during compaction on the deviatoric response of the material. By taking this phenomenon into consideration, the proposed model systematically predicts the relevant failure modes (cratering, tunneling, radial cracking and spalling) observed during ballistic impact on a concrete plate as a function of the projectile velocity and plate thickness. [ABSTRACT FROM AUTHOR]

In this paper, the effect of soft-hard plate and rubber thickness as absorbent impact against on ballistic resistance with 5.56 x 45 mm caliber deformable projectile is investigated. The characteristic of ballistic impact for each configuration target is obtained and compared based on the investigation of the hardness effect of the front plate and the thickness of rubber. The experimental results approached by simulation with finite element method were used to know several characters due to the ballistic impact. The experiment and simulation results showed that the projectile is able to perforate front plate and the impact on the back plate form a bulge on every configuration. The configuration of hard plate as front plate reveals minimum ballistic impact due to the projectile rate. The simulation shows that the maximum stress concentration occurs only on the front plate, so the front plate fails. [ABSTRACT FROM AUTHOR]

Mechanisms of projectile defeat and ballistic resistance of thin targets impacted by tip-deformable conical projectiles have been discussed in the context of the influence of apex angle of the projectile. Transition in target local failure modes occurred as the projectile apex angle was altered. The effect on projectile deformation and ballistic properties has also been discussed. A brief discussion on projectile deformation mechanism and projectile defeat near ballistic limit velocities with supporting experimental evidence is included. Numerical simulation using ABAQUS/Explicit has been able to effectively predict the projectile deformation and associated target behavior. [ABSTRACT FROM AUTHOR]

The type of propellant, its mass and the pyrotechnic system are main factors for the propulsion of the grenade with the required velocity and for obtaining the pyrotechnic effect at a certain point. Therefore, an interior ballistics approach is necessary in order to determine the theoretical values for the ballistic parameters. This paper presents a customized mathematical model for calculating the ballistic parameters of propelling pyrotechnic systems, which stands on the simplifying hypothesis determined from the numerical simulation of the firing phenomena. [ABSTRACT FROM AUTHOR]

Knitted fabrics are constructed from interlocking loops of yarn. Curvature in the yarn provides stretchability, making them well suited for garments that will cover areas of the body that require large relative motion. Although most current soft armors are composed of woven textiles, knitted fabrics made of aramid fibers such as Kevlar may have application for use in soft armor to provide a larger range of motion in addition to protection. However, their ballistic performance has not been well characterized. The goal of this work is to develop a computational framework to simulate a single jersey knit under ballistic loading. The path and shape of the yarn in the knit fabric is defined with parametric equations calibrated to CT images of a sample fabric. Results of finite element simulations demonstrate the unique mechanical response of knit soft armor, and show qualitative agreement with ballistic experiments. [ABSTRACT FROM AUTHOR]

Ballistics is the study of a projectiles motion and can be broken down into four stages: internal, intermediate, external and terminal ballistics. The study of the effects a projectile has on a living tissue is referred to as wound ballistics and falls within terminal ballistics. To understand the effects a projectile has on living tissues the mechanisms of wounding need to be understood. These include the permanent and temporary cavities, energy, yawing, tumbling and fragmenting. Much ballistics research has been conducted including using cadavers, animal models and simulants such as ballistics ordnance gelatine. Further research is being conducted into developing anatomical, 3D, experimental and computational models. However, these models need to accurately represent the human body and its heterogeneous nature which involves understanding the biomechanical properties of the different tissues and organs. Further research is needed to accurately represent the human tissues with simulants and is slowly being conducted. [ABSTRACT FROM AUTHOR]

The paper deals with a possibility of the local repairing of damaged composite armours. The proposed repairs can be performed directly in the field, allowing thus to recover the full ballistic protection in a short time. Several solutions (temporary or permanent) were designed and tested both experimentally and using numerical simulations. Overlapping of the damaged area with patch from armour steel after filling the hole with ceramic balls showed to be optimal as a temporary repair. The calculation clearly showed that the depth of penetration of the projectile is reduced in all cases of designed permanent repairs in comparison to original armour configuration. The experiments confirmed supposed enhancing of ballistic resistance, but only some repair techniques met the requirements of multi-hit testing. However, the reason of failure after multi-hit could be clearly explained with the help of used numerical simulations. [ABSTRACT FROM AUTHOR]

The teleost fish scales, such as Grass Carp and Cyprinoid, characterize hierarchical structure which usually consists of a hard bony outer layer and a soft inner cross-ply of collagen fibrils. Each scale overlaps with other neighboring scales, thus fish skin can effectively disperse external loadings with superior flexibility. Inspired by the two-layer structure and overlapping pattern of fish scales, bio-inspired composite scale, and scale-like protection system are designed in this study. Silicon carbide (SiC) ceramic and aluminum are selected as the outer and inner layers of the bio-inspired composite scale, respectively. In this study, the optimal thickness ratio of SiC/Al is chosen as 3:2 through numerical simulation on penetration test and residual velocity analysis of bio-inspired composite scale with LS-DYNA. Compared with pure SiC scales, the area density of bio-inspired composite scale can be reduced by 12.5% with the same ballistic performance at the impact velocity of 878 m/s. Further, a comparative simulation analysis among different overlapping ratios of scale-like protection systems, which consists of overlapped bio-inspired composite scales, is conducted and an optimal overlapping ratio of 0.40 is found. The present numerical study on scale-like protection system enables pathways to design a lightweight and flexible protective system. [ABSTRACT FROM AUTHOR]

The 2014 Mount Ontake eruption started just before noon on September 27, 2014. It killed 58 people, and five are still missing (as of January 1, 2016). The casualties were mainly caused by the impact of ballistic blocks around the summit area. It is necessary to know the magnitude of the block velocity and energy to construct a hazard map of ballistic projectiles and design effective shelters and mountain huts. The ejection velocities of the ballistic projectiles were estimated by comparing the observed distribution of the ballistic impact craters on the ground with simulated distributions of landing positions under various sets of conditions. A three-dimensional numerical multiparticle ballistic model adapted to account for topographic effect was used to estimate the ejection angles. From these simulations, we have obtained an ejection angle of γ = 20° from vertical to horizontal and α = 20° from north to east. With these ejection angle conditions, the ejection speed was estimated to be between 145 and 185 m/s for a previously obtained range of drag coefficients of 0.62-1.01. The order of magnitude of the mean landing energy obtained using our numerical simulation was 10 J. [ABSTRACT FROM AUTHOR]

The subject of the paper is a description of a simple test from the field of terminal ballistics and the handling of issues arising during its simulation using the numerical techniques of the finite element method. With regard to the possible excessive reshaping of the finite element mesh there is a danger that problems will arise such as the locking of elements or the appearance of negative volumes. It is often necessary to introduce numerical extensions so that the simulations can be carried out at all. When examining local damage to structures, such as the penetration of the outer shell or its perforation, it is almost essential to introduce the numerical erosion of elements into the simulations. However, when using numerical erosion, the dissipation of matter and energy from the computational model occurs in the mathematical background to the calculation. It is a phenomenon which can reveal itself in the final result when a discrepancy appears between the simulations and the experiments. This issue can be solved by transforming the eroded elements into smoothed particle hydrodynamics particles. These newly created particles can then assume the characteristics of the original elements and preserve the matter and energy of the numerical model. [ABSTRACT FROM AUTHOR]

The ballistic impact response of thermoplastic-based composite armors made from Kevlar ® fabric and polypropylene (PP) matrix has been investigated against ballistic test standard NIJ-STD 0106.01 Type IIIA. Kevlar ® fabrics of different architectures, namely 2D plain woven, 3D orthogonal and 3D angle interlock fabrics, were produced and used as reinforcements to fabricate composite armor panels, using compression molding technology. Interfacial property between PP and Kevlar ® was improved by adding a coupling agent called maleic anhydride grafted PP. Reduced density was observed in Kevlar ® thermoplastic-based composites as compared to that of the thermoset-based laminates. Ballistic impact tests were imparted with 9 mm full metal jacket (FMJ) on armor panels having different fabric architecture. Ballistic test results revealed that 2D armor was 2.4–7% more susceptible to damage than 3D armors. Hydrocode simulations were carried out using ANSYS AUTODYN v. 14.0 to obtain an estimate for the ballistic limit velocity and simulate failure modes. Post-impact damage patterns obtained from the simulations were compared with the experimental results to assess the performance of the simulations. Good correlation between the hydrocode simulations and experiments was found, both in terms of failure modes and damage patterns. 3D composite armors were able to confront the 9 mm FMJ projectile; however, the 2D plain woven armors failed. The increase in the ballistic limit from 2D plain woven armor to 3D orthogonal and 3D angle interlock armors was 16.44% and 20%, respectively, indicating the effect of fabric architecture. [ABSTRACT FROM AUTHOR]

We present an efficient event-driven algorithm for sequential ballistic deposition of complex-shaped rigid particles. Each of the particles is constructed from hard spheres (typically 5 … 1000 ) of variable radii. The sizes and relative positions of the spheres may mutually overlap and can be chosen such that the surface of the resulting particle appears relatively smooth. In the sequential deposition process, by performing steps of rolling and linear motion, the particles move along the steepest descent in a landscape formed by the boundaries and previously deposited particles. The computer time for the simulation of a deposition process depends on the total number of spheres but only weakly on the sizes and shapes of the particles. The proposed algorithm generalizes the Visscher–Bolsterli algorithm [1] which is frequently used for packing of spheres, to non-spherical particles. The proposed event-driven algorithm allows simulations of multi-million particle systems using desktop computers. [ABSTRACT FROM AUTHOR]

This paper intends to develop a target trajectory estimation algorithm with application to the ballistic target estimation in the terminal phase. The proposed design is based on the application of a second-order extended state observer (ESO) technique using target information acquired from the seeker to estimate the trajectory of manoeuverable ballistic targets. Satisfactory results have been received while applying the design in estimation of either two-dimenional or threedimentional target evasive acceleration via computer simulation. [ABSTRACT FROM AUTHOR]

In this study, the penetration behaviour of a Mild Steel Cored (MSC) round, 7.62 mm in diameter and 39 mm in length, commonly known as the AK47 round, was studied since it still forms an important part of the threat spectrum for personnel body armour systems. Likewise, boron carbide strike face materials were selected since this armour material is often the material of choice for ultralightweight body armour systems for protection against this particular threat. The presence of two, relatively soft, intermediate materials (the copper jacket and filler material of the bullet, and a fibre-reinforced polymer cladding layer on the ceramic) between the mild steel core and the boron carbide target was examined using reverse ballistics techniques, flash x-radiography and round recovery measurements. This was supported by selective numerical simulations using the computer code ANSYS-AUTODYN. It was found that stripping of the jacket, from the AK47 MSC rounds, makes a difference to its penetrating ability: the mild steel core is significantly reduced in length, and mass, when the jacket is not present. The magnitude of this effect is much greater than previously reported for high-strength steel-cored rounds and for tungsten carbide-cored rounds. The penetration event appears to be a twostage process: mushrooming of the mild steel core on, or near, the surface of the ceramic, followed by a linear erosion process as the core penetrates the ceramic itself. The second step has not been reported previously for MSC rounds. [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]

The work is focused to study the mathematical modeling and numerical simulation of solid propellant combustion during internal ballistics cycle. Here, we have used a reduced single phase model from Baer–Nunziato two-phase flow model for gas and solid mixture of propellant. The model consists of balance equations of mass, momentum and energy with constitutive laws. First ORder CEntred (FORCE) scheme is employed to provide an insight of motion of pressure wave in gun chamber during burning of igniter and solid propellant. The study is performed with the constant emission rate of igniter gases. The burning rate of propellant is expressed as a non-linear function of pressure in terms of pressure exponent. Depending on the pressure exponent three cases are evolved: constant, linear and non-linear rate of burning of propellant. FORCE scheme captures the motion of pressure wave with time and space. The local phenomena of pressure, temperature, velocity, density and rate of burning are demonstrated from breech end to the base of the projectile at different time. The effect of discontinuous pressure on burning dimensions of grain are examined. The non-uniform burning of grain dimensions may result into grain fracture. This study helps in designing the system to avoid such situations. [ABSTRACT FROM AUTHOR]

Nanostructured (NS) metals with bimodal grain size distribution, composed of coarse grained (CG) and nanograined (NG)/ultrafine-grained (UFG) regions, not only have high strength and good ductility, but they can also provide excellent ballistic performance. In this work we use numerical simulations to study the influence of microstructural attributes such as the distribution and shape of the CG inclusions on the ballistic performance of bimodal NS Cu. Our formulation is based on the mechanism-based strain gradient plasticity theory and the Johnson–Cook failure model. We also consider the effects of constitutive and failure parameters of the NG phase as well as boundary constraint of the specimen. Our results on the effect of inclusion attributes indicate that microstructures can significantly affect the velocity history of the bullet as well as limit velocity and maximum displacement of the specimen. The analysis also suggests that, to improve the ballistic performance of the bimodal NS metal, the CG inclusions need to have regular distribution and, under the condition of same distribution, they also need to have a longer projection perpendicular to the direction of impact. The simulations show that when the abrasion effect is not considered, the ballistic performance of the microstructures depend heavily on their ductility rather than their strength. The results on the boundary constraint show that when this constraint is released, the ballistic performance is reduced tremendously. It is believed that these results could provide useful insights into the development of advanced NS materials for ballistic protection. [ABSTRACT FROM AUTHOR]

Impact loading is an important process in the transport industry as it causes wear and failure of critical components. Conveyor belts are of particular importance as they are used in practically every industry where large quantities of goods are moved over short (<10 m) or long distances (>1 km). To investigate stress levels inside the material during impact loading, a gas gun was utilized to shoot 9 mm spherical steel balls onto the surface of a rubber conveyor belt. A high speed video recording system was employed in order to determine penetration depth and dissipated energy of the steel ball. Maximal penetration depths of up to 3.9 mm and maximal dissipated energies of up to 86.8 % were measured. Additionally, a numerical simulation using smooth particle applied mechanics was conducted and compared to the experimental results obtained with the gas gun. The calculated von Mises stresses affected the conveyor belts up to a maximum depth of 8.8 mm with at least 20 MPa. Maximum von Mises stresses were calculated to reach 60 MPa. [ABSTRACT FROM AUTHOR]

The ballistic performance of thin aluminium targets and influence thereon of different circumferential fixity conditions were studied both experimentally and by finite element simulations. A pressure gun was employed to carry out the experiments while the numerical simulations were performed on ABAQUS/Explicit finite element code using Johnson–Cook elasto-viscoplastic material model. 1 mm thick 1100-H12 aluminium plates of free span diameter 255 mm were normally impacted by 19 mm diameter ogive and blunt nosed projectiles. The boundary conditions of the plate were varied by varying the region of fixity along its circumference as 100%, 75%, 50% and 25% in experiments and the numerical simulations. Further, simulations were carried out to compare the response of the plates with 50% and 75% continuous fixity with those with two and three symmetrical intermittent regions of 25% fixity respectively. The variation in the boundary condition has been found to have insignificant influence on the failure mode of the target however; it significantly affected the mechanics of target deformation and its energy absorption capacity. The ballistic limit increased with decrease in the region of fixity. It decreased for intermittent fixity in comparison with equivalent continuous fixity. And, it has been found to be higher for the impact with projectile having blunt nose in comparison with the one having ogive nose. [ABSTRACT FROM AUTHOR]

In this paper some experimental results of a bullet impact on composite armor are discussed together with numerical modeling approaches. The development of high-quality composite sandwiches for ballistic protection is the target of a grant project in terms of which the research is being conducted. Traditionally, a vehicle ballistic protection is mainly achieved using metal-based armor which is heavy and thus negatively affects other vehicle parameters, such as maneuverability. These days, composite or hybrid sandwiches are becoming more and more popular. Numerical simulations allow for a reduction of the number and variability of experiments needed to obtain appropriate design of ballistic protection, but they require verified modeling approaches and reliable material data. Therefore, different modelling approaches have been tested and possibilities to adjust these models to experimental data were investigated. [ABSTRACT FROM AUTHOR]

This study aims to investigate the penetration of a projectile into a surrogate human tissue numerically, using Finite Element (FE) simulation. 20% Balistic Gelatin material (BG) is simulated with an elasto-plastic hydrodynamic constitutive law, and then impacted by steel spheres at different velocities. The results from the FE simulations are compared with existing experimental data and other analytical equations from the literature. To our knowledge, this is the first study to investigate a projectile penetration by numerical simulation, and then compare the results with analytical and experimental data from previous studies. This developed model gives encouraging results for further investigations of penetrating impact of projectile in the human body. [ABSTRACT FROM AUTHOR]

Studies of ballistic penetration into metal plates and their numerical simulation currently play a vital role in the defence sector. However, no congruent results have been presented so far, especially when it comes to impact on welded plates. Furthermore, these issues are investigated for normal impacts and very few have made an attempt for oblique impacts. Thus the aim of the present work is to conduct numerical simulation using Abaqus/Explicit in order to evaluate the ballistic performance of similar and dissimilar welded plates subjected to various bullet velocities and impact angles. The effect of post weld residual stresses and associated plastic damage on the ballistic performance of similar (Al6061) and dissimilar (Al 6061- SS 304) welded plates is also determined. The energy absorbed by the welded plates for various configurations was determined and the results are critically evaluated. [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]

Hybrid rockets are considered a promising future propulsion alternative for specific applications to solid or liquid rockets. In order to raise their technology readiness level, it is important to perform predictive numerical simulations of their internal ballistics. The objective of this work is to describe and validate a numerical approach based on Reynolds-averaged Navier–Stokes simulations with sub-models for fluid–surface interaction, radiation, chemistry, and turbulence. Particular attention is given to scale effects by considering two different paraffin–oxygen hybrid rocket engines and a simplified grain evolution approach from the initial to the final port diameter. Moreover, a mild sensitivity of the computed regression rate to paraffin's melting temperature, surface radiation emissivity, and Schmidt numbers is observed. Results highlight the increasing importance of radiation effects at larger scales and pressures. A numerical rebuilding of regression rate and pressure is obtained with simulations at the time-space-averaged port diameter, producing a reasonable agreement with the available experimental data, but a noticeable improvement is obtained by considering the grain evolution in time. [ABSTRACT FROM AUTHOR]