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In the field of ballistics, Johnson-Cook (JC) plasticity and fracture models have provided a good theoretical basis for the prediction of ballistic performance by capturing the essence of ductile metal fracture. Nevertheless, the JC model cannot accurately reproduce the fracture behaviour of some metals. Many Lode parameter-dependent fracture criteria have effectively improved this deficiency, indicating that the fracture loci of these metals are Lode-dependent, even though the flow stress behaviour is stress state dependent, which cannot be well characterized by the JC plasticity model. In this paper, a series of mechanical tests and parallel numerical simulations of ZK61m magnesium alloy were conducted. The results showed that the flow stress behaviour and fracture loci of the alloy were obviously Lode dependent. Therefore, it seems insufficient to evaluate only the necessity of incorporating Lode parameter into a fracture criterion in predicting ballistic performance of ZK61m magnesium alloy, and more investigations on the influence of Lode parameter on the plasticity behaviour of the material should be carried out. In the present work, ballistic tests were conducted on 5 mm thick ZK61m magnesium alloy plates using blunt and ogival nose shaped projectiles with a nominal diameter of 12.68 mm. The targets failed by shear plugging when impacted by blunt-nosed projectiles, but caused a unique failure pattern under the impact of ogival-nosed projectiles. Lode-dependent plasticity model and fracture criterion were adopted. Better prediction accuracy was observed when Lode parameter is considered in both the plasticity model and fracture criterion simultaneously.

An experimental study and hydrocode simulation was conducted to investigate the correlation between hardness of steel and the ballistic performance of steel-encapsulated SiC armour modules against long rod impact. The armour module design composed of a SiC tile in confinement within 10 mm backing and 5 mm cover plates, which were made of AISI 4340 steel with varying hardnesses between HRC 30 to 50. The armour modules were subjected to normal impact by conical tungsten alloy long rods of 8.3 mm diameter and 115 mm length, at a nominal striking velocity of 1.25 km/s. A witness block of AISI 4340 steel was placed behind the armour module to capture the residual projectile. Failure analysis of the armour modules and the measurement of residual penetration in the witness blocks were applied to characterize ballistic performance of the ceramic armour modules. The different modes of failure of the backing plate and its influence on ballistic performance of the module were verified through visual inspection of test modules and analysis of high speed videos. Hydrocode simulation of the experiments using LS-DYNA was carried out to model the penetration and failure processes that occurred in the armour modules. The Johnson Cook model was applied in simulation of the steel confinement, accounting for the influence of hardness on JC model parameters. Results showed that increasing hardness of the backing enhanced the performance of the module while cover plate hardness had no influence within the range of hardnesses tested. This study paves the way for future studies to further understand the influence of steel hardness on the ballistics performance of steel-encapsulated silicon carbide (SiC) armour modules.

A single optical fibre sensor is used to measure the dynamics of an impact. The method consists of sewing the optical fibre onto a woven Kevlar layer and placing it between the shoot pack and backing material. The measurement is accomplished by using the friction between the layer and the optical fibre to relate the optical fibre strain to impact deformation. Tests are done using a backing material of Roma Plastilina No.1 clay, and transparent ballistics gel with independent high-speed imaging. A final calculated BFD average error of 7.75% is presented as well as a timing error of 15.5% between the imaged dynamic BFD and the dynamic BFD determined by the FBG. This method is also tested at the U.S. Army Aberdeen Test Center in Maryland with a final calculated error of 7%.

For both ethical and practical reasons accurate tissue simulant materials are essential for ballistic testing applications. A wide variety of different materials have been previously adopted for such roles, ranging from gelatin to ballistics soap. However, while often well characterised quasi-statically, there is typically a paucity of information on the high strain-rate response of such materials in the literature. Here, building on previous studies by the authors on other tissue analogues, equation-of-state data for the elastomeric epithelial/muscular simulant material Perma-Gel ® is presented, along with results from a series of ballistic tests designed to illustrate its impact-related behaviour. Comparison of both hydrodynamic and ballistic behaviour to that of comparable epithelial tissues/analogues (Sylgard ® and porcine muscle tissue) has provided an insight into the applicability of both Perma-Gel ® and, more generally, monolithic simulants for ballistic testing purposes. Of particular note was an apparent link between the high strain-rate compressibility (evidenced in the Hugoniot relationship in the U s -u p plane) and subsequent ballistic response of these materials. Overall, work conducted in this study highlighted the importance of fully characterising tissue analogues – with particular emphasis on the requirement to understand the behaviour of such analogues under impact as part of a system as well as individually.

Soft-matrix ballistic laminates (such as those composed of fibres of Ultra High Molecular-Weight Polyethylene, e.g. Dyneema® HB26 and Spectra Shield) find extensive use as catching type armour syst ...

© 2015 Elsevier Ltd. All rights reserved. The impact response of an ultrahigh molecular weight polyethylene (UHMWPE) fiber reinforced polymer matrix composite laminate has been investigated. The laminate encapsulated an aluminum alloy sandwich panel whose corrugated core was filled with prismatic alumina inserts. The laminate encased hybrid core target could sustain ceramic prism base impacts by a spherical, 12.7 mm diameter steel projectile with velocities in excess of 2.7 km s-1. This was 150% higher than the ballistic limit of an equal areal density, similarly encapsulated aluminum plate target. By contrast, when the projectile impacted a hybrid core target at the apex of a ceramic prism insert, failure of the UHMWPE laminate on the rear face occurred at a lower impact velocity. High-speed imaging, three-dimensional digital image correlation and x-ray tomography measurements are used to show that upon impact the projectile and the ceramic insert fragment. These fragments then load the UHMWPE laminate on the rear face with a significantly reduced pressure compared to the impact pressure of the projectile on the front surface of the target. The loading area on the inner surface of the rear laminate was highest for a prism base impact and lowest for a prism apex impact. The inability to penetrate the rear laminate of the base impacted samples is consistent with the recent identification of an impact pressure controlled mechanism of progressive penetration in this class of laminate.

The mechanisms of progressive penetration for two ultrahigh molecular weight polyethylene (UHMWPE) reinforced laminates have been investigated. One used an UHMWPE fiber reinforcement while the other utilized molecularly aligned tape. Both materials had similar out of plane compressive strengths, but the fiber system had a 40% higher in plane tensile strength than the tape. Laminated, 6 mm thick plates with a [0°/90°] ply architecture were impacted by a 12.7 mm diameter sphere under conditions that either allowed out of plane plate deflection or eliminated this deflection by rear support of the target. The depth of penetration and the ballistic limit in the rear-supported tests were identical for the two materials, and proceeded by progressive ply failure. However, tests in the edge clamped condition resulted in a substantially higher penetration resistance, especially for the higher tensile strength fiber-reinforced material. Edge clamped testing of a bilayer target, where the front third was composed of the tape material and the remainder comprised fiber reinforced laminate, had the same ballistic limit as a target composed of only the higher ply tensile strength fiber reinforced material. Penetration in both test support conditions was discovered to occur by tensile ply rupture under the projectile, consistent with a recently proposed mechanism for converting out of plane compression to in plane ply tension. Lateral displacement of plies was also observed near the sides of impact craters in both materials, indicating the existence of a second mechanism impeding penetration of the spherical shaped projectile.

The PELE ammunition is characterized by a low-density filling material surrounded by a high-density brittle jacket material. An analytical model describing the fragmentation of this ammunition behind a target plate is presented. This model assumes uniaxial strain in the filling and uses the Ranking–Hugoniot relations to calculate the material state. In addition, shock and rarefaction wave interactions at the target free surface and the filling/target interface are accounted for, as well as the radial rarefaction originating from the jacket outer surface. This allows the calculation of the pressure evolution in the filling and the radial acceleration of the jacket at any axial position along the projectile. This model aims at improving previously published analytical models where the acoustic wave approximation was used and the wave interactions were neglected. Experimental results (Paulus and Schirm, 2006) are used to validate the analytical model for different target materials (aluminum and steel), target thicknesses (3 mm and 8 mm), filling materials (polyethylene and aluminum) and impact velocities (900 m/s to 3000 m/s). A qualitative comparison based on X-ray photographs reveals similar features between the model and the experiments, such as smaller and lighter fragments with a greater radial velocity at the front of the projectile compared to the fragment characteristics at the back of the projectile. A quantitative comparison based on the maximum radial velocity of the fragments shows on average a 20% difference between the analytical and experimental results for all impact conditions considered. Despite this difference, the analytical trend follows more closely the experimental one compared to the acoustic approximation especially at high impact velocities. In addition, the acoustic approximation fails to reproduce the jacket fragmentation pattern since the fragmentation length of the jacket is significantly under-predicted. A numerical simulation is also presented using the ANSYS Autodyn 14.0 software. The results show that the numerical and analytical pressure evolution in the filling and the radial velocity of the jacket are in very good agreement, verifying the uniaxial strain assumption. This agreement (together with the experimental agreement) thus suggests that the Rankine–Hugoniot relations, the wave interactions and the radial rarefaction wave must all be included in the model to adequately describe the fragmentation of the PELE ammunition behind a thin target plate.

Composite laminates made of glass/epoxy with and without nano fillers were subjected to projectile impact. The laminates of different thicknesses were prepared by hand lay-up and compression molding processes. Laminates were made from glass woven roving mats of 610 gsm, epoxy resin and nano clay of 1-5 wt.% of matrix. A piston type gas gun setup was used to impact a spherical nose projectile of diameter 9.5 mm and mass of 7.6 g, on the nanocomposite laminates at impact velocities in the range of their ballistic limit and above. The energy absorbed during penetration and ballistic limit of the nanocomposite laminates were studied both experimentally and analytically. The analytical model also predicts the energy absorbed in various failure modes due to tensile failure of primary fibers, deformation of secondary fibers, delamination and matrix crack. Mechanical properties like tensile modulus, stress-strain function, shear modulus, and strain energy release rate were used as input to the analytical model. Laminates of three, five and eight layers have been considered for the analysis. The effect of clay dispersion in the matrix for different failure modes is discussed. Ballistic limit obtained from the model is validated with experimental results and good agreement is found. � 2014 Elsevier Ltd. All rights reserved.

The mechanisms of projectile penetration of extruded 6061T6 aluminum alloy sandwich panels with empty and alumina filled, triangular corrugated cores have been experimentally investigated using zero obliquity, 12.7 mm diameter hard steel projectiles whose diameter was about a half that of the core's unit cell width. We find that low momentum impacts are laterally deflected by interactions with the inclined webs of the empty core. Complete penetration occurred by shear-off within the impacted front face sheet, followed by stretching, bending and tensile fracture of the core webs and finally shear-off within the back face sheet. This combination of mechanisms was less effective at dissipating the projectiles kinetic energy than the shear-off (plugging) mechanism of penetration of the equivalent solid aluminum panel. Inserting ballistic grade alumina prisms in the triangular cross section spaces of the corrugated core significantly increased the panel's ballistic resistance compared to the empty panel. The presence of the hard ceramic led to severe plastic deformation and fragmentation of the projectile and comminution and macroscopic fracture of the ceramic. The Al/Al2O3 hybrid panel ballistic limit was reached when pairs of parallel cracks formed in the rear face sheet at core web-face sheet nodes. The separation distance between these cracks was dependent upon the location of the impact with respect to that of the web-face sheet nodes. Nodal impacts resulted in pairs of fractures that were separated by one cell width and a critical velocity below that of the equivalent solid plate. Impacts mid-way between pairs of nodes resulted in back face sheet crack pairs separated by twice the cell width, and a critical velocity higher than the equivalent solid plate. Using X-ray tomography we show this resulted from the formation of oval (not circular) cross section fracture conoids in the ceramics. The conoid angle was about 60° in the extrusion direction but only 30° in the transverse direction. This observation may have interesting consequences for a panel's resistance to a second, close proximity impact.

This article examines whether the yield surface of silicon carbide depends on the third invariant of the stress tensor, and how such dependence would affect its performance as an armor material. The JHB ceramic model is augmented by a factor introduced for geomaterials that depends on the third invariant of stress and the tri-axial yield ratio (a material parameter defined as yield in tri-axial extension to yield in tri-axial compression.) The factor scales yield on the compressive meridian for other states of stress. Tests of high-velocity impacts of silicon carbide are selected from the literature, and computations are performed with the augmented model using several values of the tri-axial yield ratio. The sensitivity of the computations to the variation of the tri-axial yield ratio is determined for each test. Compressive plate impacts and ballistic impacts of thin targets show the most sensitivity, and comparison of the computed compressive plate impacts to test results suggests a significant dependence on the third invariant.

This paper discusses the technique of Digital Speckle Radiography (DSR) and its application to the measurement of the internal flow fields in penetration of sand by long-rod projectiles at velocities up to 200 m/s. Three different rod nose shapes were studied: flat-ended, ogive-2, and hemispherical. Impacts performed on gelatine and concrete gave significantly different displacement fields to sand. Sand, therefore, cannot either be modelled as a fluid or as a conventional solid. Simulations performed using a code written by two of the authors (Bobaru and Promratana) showed that the velocity distribution has a very different appearance to the force distribution. This suggests that processes such as reorganisation, sliding and void filling take place, allowing the grains to move in directions other than the applied force. The resulting velocity distribution bears a strong resemblance to the experimentally measured displacement fields.

Three-dimensional FE model is presented for perforation under normal and oblique impact of sharp nosed projectiles on single and layered ductile targets. Numerical simulations have been carried out to study the behavior of Weldox 460 E steel and 1100-H12 aluminum targets impacted by conical and ogive nosed steel projectiles respectively. Weldox 460 E steel targets of 12 mm thickness in single and double layered combination (2 × 6 mm) and 1100-H12 aluminum targets of 1 mm thickness in single and double layered combination (2 × 0.5 mm) impacted at 0°, 15° and 30° obliquity were considered for simulations. The results of monolithic and layered targets were compared for each angle of impact. Monolithic targets were found to have higher ballistic resistance than that of the layered in-contact targets of equivalent thickness. Failure of both the targets occurred through ductile hole enlargement. However, ogive nosed projectile failed 1 mm thick aluminum target through petal formation and conical nosed projectile failed 12 mm thick steel target through a circular or elliptical hole enclosed by a bulge at rear surface. The explicit algorithm of ABAQUS finite element code was used to carry out the numerical simulations. Various parameters which play critical role in numerical simulation such as element size and its aspect ratio have been studied.

A new technique using nickel–chromium wire, called the NiCr (Nichrome®) wire technique, has been presented in a first paper describing the technique [1]. This second paper focuses on the results obtained when this new technique is applied to ballistic fabrics. Strain distributions on the layer impacted, as well as in different layers, are presented. An energy balance based on the strains is shown to provide reasonable values for the elastic energy stored by the yarns. Failure times of the first layer as a function of impact velocity are discussed and a simple momentum balance is shown to predict well the deflection history of the fabric. Ultra-high-speed photography and high-speed videos allowed recording of fabric deflection vs. time. The combination of the four diagnostic techniques, including X-rays, delivers a very complete picture of the impact mechanics in fabrics, both for early-time and late-time phenomena.

This is the first of two papers that describe a new technique to measure yarn strains in a fabric subjected to ballistic impact. The main objective of this research was to develop the Nickel–Chromium (NiCr) wire technique, although other diagnostic techniques were used simultaneously (X-rays, high-speed video, and ultra-high-speed photography), to support interpretation of results. The NiCr wire principle, calibration, assumptions and test set-up are thoroughly explained. The NiCr wire is then applied to impact on real targets and the results are analyzed. A few examples of strain measurements are shown. It is shown that the NiCr wire signals are very rich in information and can give, not only the strains, but also reveal if the fabric was perforated and how long it took to fail.

An experimental study was made of the pressures generated by a single hydrodynamic ram event. A generic box type fuel tank simulator was fabricated to study the phenomenon and was capable of containing 3785.4 l of liquid thereby isolating the phases of the event from tank wall reflections, and enable separation of the effects of each phase. Tungsten, steel, and aluminum spherical projectiles were fired into the tank and the result was measured using high-speed pressure transducers, which were located throughout the tank, and compared to the pressure waves and events recorded inside the tank simulator with a high-speed video. It was determined that a high-pressure initial wave is generated at impact and is followed by the more gradual drag pressure around the projectile. The angular distribution of the initial wave and the variation with distance were investigated along with the effect of projectile mass on the drag pressure. This region of pressure decreases in the projectile wake, forming a trailing cavity that remains at a low pressure until the cavity begins to collapse. This results in the largest recorded pressure inside the simulator.

This paper reports a result of hypervelocity impact experiments on cryogenically cooled aluminum alloys and a composite material. Experiments are carried out on a target palate at 122 K. Aluminum spheres at 1.95 km/s in 50 kPa air were impinged against the target plate at cryogenic temperature and the result was compared with room temperature target plates. Hypervelocity impact (HVI) processes were visualized with shadowgraph arrangement and recorded with high-speed video camera and to ensure the temperature dependence we compared HVI tests with metal target plates with AUTODYN 2D and SPH numerical simulations. We found that cryogenic impacts created slight differences of impact damage from room temperature ones, i.e., the shape and averaged diameters of HVI crater holes were less at cryogenic impacts.

This paper presents the results of scale size experiments using a tungsten-alloy long-rod projectile fired against 97.5% Al2O3 ceramic targets at 1.8 and 2.6 km/s. Two targets were used, one having lateral steel confinement; the other without. The projectile overmatched the target, and residual projectile length and velocity were recorded using ballistic-syncro photography. Flash radiography was used during penetration of the unconfined target to obtain the penetration velocity. Manganin pressure gauges were also used to obtain additional data on the response of the ceramic target during penetration. Results from the eight experiments indicate that the confinement reduced the residual energy of the projectile at both impact velocities. Expressed in terms of the projectile impact energy, 55–56% was lost in the unconfined target at 2.6 km/s compared with 60% for the confined design. The same trend was found at 1.8 km/s with 68% and 72–73% for the unconfined and confined, respectively. Predictions using the QinetiQ GRIM2D hydrocode and a simplified form of the Johnson–Holmquist ceramic material model agreed well with the experiments for three out of the four test configurations. The predicted projectile erosion and retardation against the confined target at 1.8 km/s was excessively high. Analytical predictions using the Tate modified Bernoulli equation also gave reasonably accurate predictions for three of the tests, but values for the Tate target ‘strength’ extracted from experiments using a different target configuration were not accurate for the target design used in this paper. r 2006 Elsevier Ltd. All rights reserved.

The paper reports experimental and numerical simulation of ballistic impact problems on thin composite laminated plates reinforced with Kevlar 29. Ballistic impact was imparted with simulated fragments designed in accordance with STANAG-2920 on plates of different thickness. Numerical modelling was developed and used to obtain an estimate for the limit perforation velocity (V50) and simulate failure modes and damage. Computations were carried out using a commercial code based on finite differences and values obtained are compared with the experimental data to evaluate the performance of the simulation. Good correlation between computational simulation and experimental results was achieved, both in terms of deformation and damage of the laminates. Future work is advanced to include the interposition of an outer ceramic layer as well as examining the influence of dry-wet and temperature cycles on the mechanical strength of the plates and their temporal evolution under accelerated ageing.

High-speed metal-on-metal sliding experiments have shown unique tribological phenomena. Dominant surface modification occurs in the form of teardrop-shaped craters (gouges). Gouges on rocket sled tracks and electromagnetic (EM) launcher rails are the best known cases of steel-on-steel and aluminum-on-copper sliding damages, respectively. We have shown here that severe gouging is produced during hypervelocity sliding between long rods and target material in reverse ballistics experiments. This is the first reported gouging in a non-planar geometry. Nevertheless, the gouges produced are strikingly similar to those found in planar experiments. In this paper, we also present our analysis of gouges caused in a tungsten-steel system due to hypervelocity sliding. The gouges so produced were examined to establish the underlying tribological and fractographic behavior. We found that gouging provides an efficient mode of material removal and a probable cause for fracture. A numerical simulation of plate target interaction with a long rod possessing a gouge indicates that the gouge can indeed lead to fracture and subsequent performance degradation of the penetrator.

In order to investigate the possibility of processing brittle materials by ball impact, the effects of back plate materials on cone crack formation in glass plate by impact with small spheres were evaluated experimentally. Crack morphologies developed in soda-lime glass with back plate materials of Polyurethane, PMMA and Aluminum were investigated as a function of impact velocity. Back plate materials were more effective in producing perfect cones than unbacked glass plates. In the case of PMMA, perfect cone was formed over a larger velocity range. The velocity range over which perfect cones were formed was influenced by both the thickness and the material of the back plates. By the proper selection of back plate materials, the application of this punching process to brittle materials in industrial technology is expected.

A simple theoretical method, which is based on ductile damage mechanics and which retains strain rate effects, is presented for predicting the failure of beams made from a perfectly plastic material and subjected to impact loads. For this class of materials, the strains can be estimated by defining a hinge length. The definition adopted here leads to reasonable predictions for the plastic strains and the strain rate, as shown by comparing the results with numerical calculations and experimental data. The equivalent strain and the strain rate can be used in the damage model to predict the failure of beams, as shown in a companion paper (Alves, Jones, Int J Impact Eng 2002;27(8):863–90).

The analytical model developed in Part I (Int J Impact Eng 2002;27(8):837–61) using continuum damage mechanics is used in this paper to predict the displacement to failure of beams subjected to static or dynamic loads producing large plastic strains. The beams, which were made of a ductile, strain rate sensitive material, were loaded at different positions on the span, by two tup geometries travelling with initial impact velocities up to 15 m/s. A reasonable correlation is obtained between the theoretical predictions and the experimental results for the displacements to failure.

For the experimental characterization of behind-armour debris so-called metallic witness packs can be used. A metallic witness pack consists of an array of metallic plates interspaced by polystyrene foam sheets. To quantify the fragment mass and velocity from the corresponding hole area and position in the individual witness plates, perforation threshold curves must be available to provide the ballistic limit velocity for each plate as a function of the fragment mass. Furthermore, the relation between the fragment impact velocity and hole size should be known. This paper presents the results of a collaborative study between Defence Research Establishment, Valcartier (DREV) and TNO Prins Maurits Laboratory, The Netherlands. The first phase of this project is an experimental study to develop perforation threshold and hole-growth curves for two metallic witness pack configurations. In addition, it is shown that a hydrocode can be successfully used to predict perforation threshold velocities.

Ballistic impact experiments were performed on ceramic laminate targets at three scale sizes, nominally 1 3 , 1 6 , and 1 12 , to quantify the effects of scale on various responses, in particular, the ballistic limit velocity. The experiments were carefully designed and controlled so that the different scale sizes were high fidelity replicas of each other. A variety of responses, such as residual projectile quantities, hole size, and the extent of bulging, were measured. Some of the measured quantities showed little or no dependence on scale size, whereas other quantities, particularly the ballistic limit velocity, were found to vary with scale size. The percentage difference was quantified, and the results extrapolated to estimate full-scale response from the subscale tests.

Herein, we study the technique of improving the gun performance by installing a diaphragm in the pump tube of the gun. A CFD study is carried out for the 0.28 in. gun in the Hypervelocity Free Flight Radiation (HFF RAD) range at the NASA Ames Research Center. The normal, full-length pump tube is studied as well as two pump tubes of reduced length (approximately 75% and approximately 33% of the normal length). Significant improvements in performance are calculated to be gained for the reduced length pump tubes upon the addition of the diaphragm. These improvements are identified as reductions in maximum pressures in the pump tube and at the projectile base of approximately 20%, while maintaining the projectile muzzle velocity or as increases in muzzle velocity of approximately 0.5 km/sec while not increasing the maximum pressures in the gun. Also, it is found that both guns with reduced pump tube length (with diaphragms) could maintain the performance of gun with the full length pump tube without diaphragms, whereas the guns with reduced pump tube lengths without diaphragms could not. A five-shot experimental investigation of the pump tube diaphragm technique is carried out for the gun with a pump tube length of 75% normal. The CFD predictions of increased muzzle velocity are borne out by the experimental data. Modest, but useful muzzle velocity increases (2.5 - 6%) are obtained upon the installation of a diaphragm, compared to a benchmark shot without a diaphragm.

Summary Generalizations have been made to the two-dimensional penetration and perforation analysis of Ravid and Bodner (1983) for blunt nosed, rigid projectiles impacting viscoplastic targets in the ordinary ballistic range. The new developments consist of consideration of ogival, conical, and spherical projectile nose shapes, possible alterations of the plastic flow field due to deep penetrations, thermo-mechanical coupling leading to thermal softening, and the addition of a requirement on the inertial work rate of target material.

Summary High-speed metallic jets are squeezed out of the conical cavities in a metallic block when loaded with shock waves. The particulation studies on these jets, which elongate under a strain rate of the order of 10 4 –10 5 s −1 , have been carried out theoretically as well as experimentally. The synchro-streak technique (SST) has been used to measure the unparticulated jet distance (UPJD). The time of particulation calculated from the UPJD has been found to be equal to the total of the collapse time and the stretching time. It has been found that as the angle of conical cavity increases, the jet diameter and the particulation time increase, whereas the jet tip velocity and existing strain rate decrease. From the experimentally measured jet diameter the time of particulation has also been calculated by the Hirsch approximation. This time period is in close agreement with the particulation time calculated by the authors. From the measured jet diameter and jet length, the mass of the jet and the thickness of the block material squeezed into the jet have been estimated. A comparative study on aluminium and copper jets has also been conducted and it has been observed that for the given explosive metal system the jets produced by aluminium are solid and coherent as compared to those produced by copper.

Summary The effect of projectile nose shape on penetration is examined numerically using the nonlinear, large deformation wavecode CTH. In particular, the impact of a tungsten alloy, long rod projectile into a 4340 steel target is investigated for three different nose shapes: blunt, hemispherical, and conical. The pressures are sufficiently high that erosion of the projectile begins immediately upon impact. The decays of the shocks are examined, as are the resulting material flow fields. Later-time effects are also explored, such as how the nose shape affects penetration, and how long each case takes to arrive at a quasi-steady-state flow configuration in which the tungsten-steel interface is completely determined by eroding plastic flow.

The disintegration behavior of projectile rods when impacting plates at velocities above 10 km/s is largely unexplored. Possible material responses include vaporization, melting, solid state phase changes, plastic flow, shear localization, and ductile and brittle tensile fracture. Two primary difficulties have prevented experimental studies of projectile response in this velocity regime, namely the lack of a technique for accelerating a projectile to velocities above 10 km/s, and the lack of a procedure for recovering the projectile remains after impact for examination. These difficulties were overcome recently by using an exploding foil technique to drive an impactor plate and by using a reverse ballistics test arrangement to allow projectile recovery. This paper describes this experimental procedure for investigating the disintegration behavior of projectile rods under hypervelocity impact conditions, presents preliminary results for steel, aluminum and lead, and discusses requirements for computational material response models.

Conical penetrators have been shown to give enhanced penetration over flat-ended projectiles up to a certain transition velocity. This transition velocity was found to be associated with a separation of the conical nose from the penetrator body which caused the penetrator to revert to the behaviour of a flat-ended penetrator at higher velocities. An explanation of the marked deformation resistance of the conical noses of these penetrators is presented.

The Lawrence Livermore National Laboratory 100-kV electric gun has been used to launch flat-plate projectiles for use in studies of spall and hypervelocity impact penetration of thin plates. Impactors were 0.3-mm thick Kapton with dimensions and velocities ranging from 100 mm 2 at 4 km/s to 10 mm 2 at 18 km/s. A Fabry-Perot laser velocimeter, an electronic streak camera, and a flash x ray were used as diagnostics of the flyer-plate impact on the selected specimen. Experiments generally included the recovery of the remnant specimen and fragments for detailed examination, permitting a study of incipient spall, onset of melting, and fraction fragmented. Experiments to be described include spall measurements on simple and composite target walls at normal and oblique incidence and “reverse ballistics” impacts of the thin-plate impactor on a stationary penetrator (e.g., Kapton impactors at 15 km/s incident on rods of steel, aluminum, and lead) for calibration of hypervelocity impact codes.

An experimental program has been undertaken to study the phenomenon of both normal and oblique impact of cylindro-conical and cylindrical projectiles on metallic plates, a domain where almost no test data are available. Hard-steel strikers of 12.7 mm nominal diameter and either 60° conical or blunt tips and blunt soft aluminum cylinders of the same diameter were fired at 2024-0 aluminum targets with thickness from 1.78 to 25.4 mm and at both mild steel and medium carbon steel with thickness up to 19.05 mm. Inital velocities ranged from about 20 to 1025 m s−1, achieved with the aid of a pneumatic cannon at low speeds and a powder gun in the upper velocity range. Initial target obliquity was varied from normal to 50°. The primary results obtained involved the measurement of the velocity drop and change in projectile orientation as the result of passage through the target. The target damage, consisting of dishing, petals, plugs and bands separated from the crater, was examined and metallurgical determinations were executed for a selected set of runs. The information obtained should provide a good basis for understanding the mechanisms involved in this type of impact and perforation. It will also serve as a reliable source of data for comparison with the predictions from analytical models of the process which do not currently exist, but will most certainly be developed in the future.

A series of hybrid sandwich structures were fabricated by shrink-fitting precision-ground prisms of alumina (CoorsTek grade AD 995) with triangular, trapezoidal or rectangular cross-sections into the voids of extruded sandwich panels made from Al 6061-T6. The panels were subjected to impact tests using hard steel spheres over the velocity range 570–1800 m s −1 . A combination of X-ray tomography, high-speed video imaging and cross sectioning of impacted samples was used to investigate the penetration mechanisms. We find that the ballistic performance of these structures, characterized by the ballistic limit and the exit velocity of impact ejecta beyond this limit, is significantly improved when triangular prisms are replaced by trapezoidal prisms, provided the base width of the prism exceeds about three times the projectile diameter. Additional performance improvements are obtained when the trapezoidal prisms are replaced by rectangular prisms, albeit at the expense of an increase in the lateral extent of damage. The variations in impact response are found to arise from: (i) the effect of prism size and shape on the degree of confinement of the ceramic by the metallic webs, (ii) the core web structure, which influences the fracture conoid angle in the transverse plane, and (iii) the spacing of web-face nodes on the back face, which governs the deflection and fracture of the back-face sheet.