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Ductile thermoplastics, for example Ultra High Molecular Weight Polyethylene (UHMWPE), are of interest for their impact energy absorbing capabilities. While the impact perforation mechanisms of metallic targets have been investigated in some detail, far less progress has been made towards understanding the impact resistance of ductile polymers. The aim of this investigation is to identify the relationship between the projectile tip geometry and impact energy absorption of semi-crystalline thermoplastics. The focus of the study is light-weight monolithic plates of extruded polymer impacted normally by rigid projectiles at velocities up to 100 ms −1 . Three polymers will be considered: Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE) and Ultra High Molecular Weight Polyethylene (UHMWPE). Polyethylene provides a convenient test material, as variations in microstructure provide a contrast in mechanical properties, without significant variations in density. Three distinct projectile nose shapes are considered: blunt, hemi-spherical and conical. For a conical tip, perforation occurs by ductile hole expansion. For this nose shape the high yield strength and strain rate sensitivity of HDPE offers an advantage over the other two polyethylenes. Perforation by blunt and hemi-spherical projectiles is more sensitive to deformation localisation. The high strain hardening of UHMWPE, which increases with strain rate, results in a significantly greater impact resistance than either HDPE or LDPE. The perforation mechanisms and energy absorption of these PE plates are contrasted with those of thin aluminium alloy targets that have the same total mass. UHMWPE outperforms these metallic targets for all three projectile nose shapes. Finally, the influence of target thickness on the impact perforation of LDPE is considered. All three nose shapes show a linear increase in perforation energy with target thickness. [ABSTRACT FROM AUTHOR]

The database for depth of penetration by projectiles into semi-infinite targets is quite extensive. The objective is to use the experimental semi-infinite penetration data to predict finite-thickness target effects. Similitude considerations are used to represent penetration response as a function of a normalized impact velocity, which is the ratio of the penetration pressure to the target strength. Then, a least-squares regression analysis methodology was applied to the normalized experimental data to provide an analytic expression for the normalized depth of penetration as a function of the normalized impact velocity over a very large velocity range, typically a few hundred meters per second to over 3500 m/s. We use the analytic expression, along with some simplifying assumptions, to estimate ballistic limit thickness T 50 and/or the ballistic limit velocity V 50 . If a target is overmatched, i.e., perforated by the projectile, an estimate is also made for the projectile residual velocity and residual length. The experimental data on which the regression fit is based consists of L / D 10 projectiles, so a procedure is also developed to account for different projectile aspect ratios. A series of examples are provided to demonstrate the utility and accuracy of the approach. [ABSTRACT FROM AUTHOR]

This paper proposes a simple formulation for the impact analysis of a deformable projectile on reinforced concrete targets. This approach assumes the presence of soft strikers and rigid targets. Based on an energy balance, it aims to predict a perforation limit for different targets under soft impacts. The procedure employed is validated by means of tests performed on a rigid target (pendulum test) and reinforced concrete slabs. The article discusses various estimations of the crushing force of projectiles, as derived from experimental results and numerical approaches. The efficiency of simplified approaches is highlighted from an engineering point of view. The limit between soft and hard impacts is also analyzed according to a recent criterion. Moreover, the paper proposes validating the approach using experimental tests with both perforating and non-perforating impact tests on nine slabs. [ABSTRACT FROM AUTHOR]

In this paper an experimental and numerical work is reported concerning the process of perforation of thin steel plates using different projectile nose shapes. The main goal is to analyze how the projectile shape may change the ballistic properties of materials. A wide range of impact velocities from 35 to 180 m/s has been covered during the tests. All the projectiles were 13 mm in diameter and the targets were 1 mm thick, as such the projectile can be regarded as rigid and the target sheets were of interstitial-free (IF) steel. The mass ratio (projectile mass/steel sheet mass) and the ratio between the span of the steel sheet and the diameter of the projectile were kept constant, equal to 0.38 and 3.85 respectively. To define the thermoviscoplastic behavior of the target material, the Rusinek-Klepaczko (RK) constitutive model [1] was used. The complete identification of the material constants was done based on a rigorous material characterization. Numerical simulations of some experimental tests were carried out using a non-linear finite element code ABAQUS/Explicit. It was found that the numerical models are able to describe the physical mechanisms in the perforation process with a good accuracy. [ABSTRACT FROM AUTHOR]

In this research effort, ballistic performance of a quenched and tempered steel was investigated. Low alloy steel was selected where austenization, quenching and finally tempering at 600°C were applied to it. Thereafter, the heat-treated steel was shot with armour piercing 7.62 mm calibre and the occurrence of failure, after the interaction between the projectile and the steel, was investigated. The shot was performed at zero degree (0°) obliquity with a projectile velocity of 830m/s. After the shot, microstructural and fractographical examinations were carried out on the sample taken from the perforated region using scanning electron microscopes to determine the matrix phase and secondary phases. It was observed that the steels had tempered martensitic-bainitic matrices after heat treatments; a crater was formed on the front side of the steel; deformed and transformed adiabatic shear bands had an effect on the crack formation and propagation in the matrix; and perforation mode of the steels was typical petalling. [ABSTRACT FROM AUTHOR]

Abstract: The evaluation of ballistic resistance of steel targets is important due to its direct application to the safety of defense protective structures such as bunkers for military personnel, shelters for arms and explosives as well as safety of nuclear containment against missile impact. Experiments on penetration of 23mm hard projectiles into mild steel plates were performed for 500mm square plates with 30, 50, 60, and 150mm total thicknesses. Results for ballistic limits obtained from existing empirical and analytical relations are compared with those from experiments. In addition, numerical simulations to predict the experimental results were made. Erosion (cell removal) criteria were established in order to realize simulation. Effect of the erosion strain value for which cells are removed on the prediction of penetration into steel plates was investigated. The numerical results show that erosion strain value has a significant effect on the prediction of perforation into steel plates. [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]

Abstract: An analytical model has been developed in this paper for perforation of ceramic/multi-layer woven fabric targets by blunt projectiles. In previous Chocron–Galvez analytical model the semi-angle of ceramic conoid is constant and the strain rate effects are also neglected in the stress–strain behavior of the yarns and only strain energy absorbed by the yarns is considered. In this paper which is an improvement to the Chocron–Galvez analytical model for modeling the fragmented ceramic conoid, the Zaera–Sanchez-Galvez analytical model has been used and the semi-angle of ceramic conoid has been modified. For modeling the back-up woven-fabric material and deformation of yarns during perforation, the kinetic and strain energy of yarns has been determined. In the stress–strain relation of yarns, the effect of the strain rate is considered. Furthermore, a failure model based on the energy absorbed until failure by woven fabric is also used. Residual velocity, velocity–time history of projectile, residual mass of fragmented ceramic conoid, penetration depth until failure of yarns and energy absorbed by woven fabric are all estimated by new analytical model. Velocity–time history of the projectile shows a good agreement with the Chocron–Galvez numerical model. Also, near the ballistic limit velocity, prediction of residual velocity of new model is better than Chocron–Galvez analytical model. [Copyright &y& Elsevier]

Abstract: A series of experiments are carried out to explore the impact characteristics of stiffened plates struck by the sub-ordnance velocity projectiles. Considering the relative position of impact point to the nearest stiffeners on target, six kinds of representative target plates with different stiffened styles are specially designed. Altogether sixteen target plates, respectively without, single- and cross-stiffened are tested and compared. Two kinds of projectiles, one with spherical nose and the other with truncated oval nose, are fired using a 25 mm refitted cannon. The initial velocities of projectiles range from 244 to 430 m/s. Experimental results show that the penetration process is greatly dependent on the nose shapes of projectiles. The tumbling of truncated oval-nosed projectiles is very prominent, which results in the great uncertainty of deformation and failure mode of target plates. While the spherical-nosed projectiles keep much more stable, plugging and ductile hole enlargement are the most distinct failure modes. In the end, some empirical formulas aimed at blunt-nosed projectiles are proposed, which could be helpful for the design of the protection structures. [Copyright &y& Elsevier]

Abstract: This paper examines the penetration and perforation of fibre-reinforced plastic (FRP) laminates struck by rigid projectiles with different nose shapes within a wide range of impact conditions using ABAQUS/Explicit code. It is assumed that the FRP laminate target response can be represented by a velocity dependent forcing function which eliminates discretizing the target as well as the need for a complex contact algorithm. The forcing function is then applied to the surface of the projectiles as boundary conditions in the numerical model. With this combined analytical and computational technique we can obtain the depth of penetration, residual velocity, ballistic limit, transient response in terms of time-histories of displacement/penetration, velocity and deceleration of the projectile. It is shown that the model predictions are in good correlation with available experimental data. [Copyright &y& Elsevier]

This paper presents an analytical model for studying the material failure in shear hinges formed during the dynamic plastic response of a circular plate under projectile impact. Analytic solutions for the ballistic perforation performance of a fully clamped circular plate struck by a blunt projectile are obtained. It takes into account both the global response (plate bending) and the localized shear. Based on the estimations of the shear strain and the size of shear hinge, condition for the initiation of an adiabatic shear band is formulated. The effectiveness of the present model is demonstrated by reasonable agreement between the theoretical predictions and the available experimental data for the perforation of Weldox 460E steel plates. [Copyright &y& Elsevier]