Hardened Steel Projectiles Research Articles

Ballistic impact resistance of ultra-high-performance concrete (UHPC): A comprehensive experimental investigation and parametric analysis

This study explores the ballistic impact resistance of Ultra-High Performance Concrete (UHPC) through an extensive and detailed experimental investigation. This study will address various gaps related to the impact performance of UHPC. This investigation focused on understanding the ballistic resistance performance of UHPC based on (a) the influence of projectile/bullet parameters (hardness, velocity/energy, diameter, and nose shape), (b) the effect of hybrid fibers, (c) comparative analysis of the use of steel mesh and reinforcement bars and (d) effect of sub-zero temperature. In this parametric investigation, different types and shapes (flat, conical, and ogive) of hardened steel projectiles (diameter 12 and 18 mm) with impact velocities ranging from 103 to 182 m/s or impact energy ranging from 674 to 2103 J and UHPC slabs with thickness ranging from 36 to 100 mm was considered. Steel mesh and reinforcement bars at different spacing (with and without fiber UHPC) were also assessed, along with the effect of sub-zero temperature of −30 °C. The impact energy of the projectile and thickness of UHPC targets were statistically significant parameters affecting penetration depth in UHPC compared to other parameters with a p-value much less than 0.001. The Artificial Neural Network (ANN) model developed in the study could predict the penetration depth with reasonable accuracy (MAPE and RMSE were observed to be 7.69 and 12.12, respectively). The experimental results of this study will provide insights into the development of guidelines for using UHPC as a protective material, which can help ensure the safety and resilience of infrastructures in the face of potential threats.

Numerical Prediction of Ballistic Performance of Thin Concrete Plate

This research explores the ability of 60[Formula: see text]mm thick reinforced concrete (RC) plates to resist impacts from ogive-nosed hard steel projectiles. The projectiles used in the present study have a diameter of 19[Formula: see text]mm, a length of 200[Formula: see text]mm, and a mass of 0.4[Formula: see text]kg impacted on the RC plates with incident velocities ranging from 92[Formula: see text]m/s to 161[Formula: see text]m/s. Numerical simulations were conducted using ABAQUS/Explicit finite element software to validate the experimental results. The Holmquist–Johnson–Cook (HJC) material model was employed to simulate the constitutive behavior of concrete, while the Johnson–Cook (JC) material model was used to simulate the material response of reinforcing steel bars. The residual velocities obtained from the simulations closely matched the actual experimental results, showing a polynomial correlation with the incidence velocities of the projectiles. Moreover, the experimentally and numerically determined ballistic limit for the 60[Formula: see text]mm thick RC plate was found to be 108[Formula: see text]m/s and 109.5[Formula: see text]m/s, respectively. In contrast, the ballistic limit calculated using empirical mathematical expressions was 107.4[Formula: see text]m/s. This alignment between predicted, calculated, and actual ballistic limits underscores the reliability and accuracy of both numerical and empirical approaches.

Experimental and numerical study on ballistic resistance of aluminum foam sandwich panel considering porosity and dimensional effect

Sandwich panels have been widely used in various industries due to their high strength and energy absorption capacity. In this study, the ballistic behavior of a sandwich panel comprised of two aluminum face-sheets and an aluminum foam as the sandwich core is studied. The panels are constructed and subjected to the blunt-nosed projectile. The experimental test consists of a sandwich panel with three different ranges of foam densities and two thicknesses for the panels beside hardened steel projectiles. Then, numerical simulations of the projectile perforation in the panels are conducted that are in good agreement with the experiments. The failure mechanism of the sandwich panels is investigated and the role of foam core is discussed. Failure mechanism and the amount of plug depends on foam density and projectile velocity, such that different failure mechanisms such as plugging, petaling, and dishing occurred for the face-sheets. After that, the ballistic limit velocity (VBL) of sandwich panels was calculated via experiments and finite element simulations. The experiments and simulations showed that increasing the density and thickness of the foam core generally leads to an increase in VBL. Finally, we study the panels with the constant mass and (or) constant height with different foam densities and the effect of foam density is investigated in these cases.

Computational analysis of aluminium alloy plates against conical-nose steel projectile

The usage of aluminium alloy in shielding structures is becoming prevalent choice due to its low density. Even then, articles and reports describing the experimental and computational analysis of such problems are still limited. This paper illustrated the computational analysis of AA5058 against impact of hardened steel projectiles with conical nose. The computational analysis was performed using finite element code-ANSYS. The target plate used was in shape of circular disc of 500 mm diameter and fixed at its curved face. However, wide range of thickness of target plate i.e., 15 mm, 20 mm, 25 mm and 30 mm were considered in the work reported. The projectile considered was of 20 mm diameter and 98 mm long. The conical shape was provided on projectile for 30 mm length on one of its sides. The target material was modeled in finite element code using Johnson-Cook constitutive model. The limiting ballistic velocity of target material was computationally investigated considering initial and residual velocities of projectile. The ballistic limiting velocity for target plate with 15 mm, 20 mm, 25 mm and 30 mm were reported as 214 m/s, 245 m/s, 250 m/s and 300 m/s respectively. Also, the residual velocity for the complete perforation in case of all the variation of thicknesses of target plate was observed and reported. The results obtained from computational analysis were found in good agreement with the analytical model presented elsewhere.

Microstructure evolution of an artificially aged Al-Zn-Mg-Cu alloy subjected to soft- and hard-steel core projectiles

An investigation was conducted to study the effect of soft (220 Hv) and hard (750 Hv) steel projectiles on an Al-Zn-Mg-Cu alloy processed by hot extrusion followed by heat treatment (solid solution treatment at 743 K/1.5 h + ageing treatment at 388 K/24 h). The results show that the hardness of the projectile material can influence on the shape and size of the perforation channel formed after the penetration. The hard steel projectile has longer depth of penetration and the crater front diameter is narrower comparing with the Al alloy after penetration by the soft steel projectile. Adiabatic shear bands (ASBs) are formed in the perforation channel after penetration with presence of recrystallized grains within these bands. The ASBs are wider after the hard steel projectile penetration with presence of cracks comparing with the ASBs formed after the soft steel projectile penetration. Precipitates are increased in size and overlapped in the perforation channel which are mainly of G.P. zone and η' precipitates. Hardness values of the Al alloy after penetration increase in the upper side of the perforation channel over the middle and end regions of the channel.

Microstructure characteristic of spray formed 7055 Al alloy subjected to ballistic impact by two different steel core projectiles impact

7055 aluminium (Al) alloy was synthesized by spray forming followed by hot extrusion, later subjected to (T6 & T74) aging treatments and its mechanical properties were examined. To investigate the ballistic behavior of the semi-infinite aluminum alloy target material, ballistic test with two different types of projectiles 7.62 mm soft steel core and 7.62 mm armor-piercing hard steel core projectiles were carried out. Excellent mechanical properties such as; higher strength UTS 708 MPa, fracture to elongation 12.8% and hardness 240 HV were achieved in the T6 condition owing to the MgZn2 phase and Al3Zr strengthening particles. Ballistic performance of the 7055-T6 target was superior to the T74 heat treated condition in terms of depth of penetration, crater diameter, strength, ductility and hardness. The target materials were deformed seriously against armor-piercing hard steel projectile impact as compared to soft steel core projectile. The microstructure was modified within the 1–1.5 mm area from the crater wall. The spray formed Al alloy have a good combination of strength and ballistic performance under the T6 heat treatment condition in comparison of T74 and other alloys produced by conventional forming methods.

Characterisation of damage mechanisms in oxide ceramics indented at dynamic and quasi-static strain rates

Ceramic materials are known to display rate dependent behaviour under impact. Tests to establish the strain-rate dependent variations in damage mechanisms have been carried out on debased alumina, an alumina-zirconia composite, and 3Y-TZP. Materials were indented dynamically and quasi-statically using identical sharp hardened steel projectiles while recording the load profile. Characteristics typical of both sharp and blunt indentation types were observed using scanning electron microscopy and piezospectroscopic mapping. At dynamic strain rates both the depth of the indentation and the residual stress in the material were lower than for quasi-static tests. This was attributed to temperature-induced softening of the projectile. Unusual behaviour was observed in the 3Y-TZP samples due to the reversible transformation from tetragonal to monoclinic crystal structures during mechanical loading. These effects and the observed superior mechanical strength against impact suggest that zirconia or zirconia-composite materials may have advantages over debased alumina for application as ceramic armour materials.

Prestressed concrete targets under high rate of loading

Prestressed concrete is highly being preferred as material for construction in the case of strategic and relevant structures such as, for instance, nuclear containments, armor deposits, shelters, bridges, and military bunkers. It is highly durable, fire and corrosion resistant, and non-porous. In order to study the influence of prestressing on the mechanics of deformation, energy absorption capacity, and failure modes of concrete targets, finite element simulations have been carried out using hard steel bullets and compared with the experiments carried out by the authors earlier. Prestressed concrete targets of plan size 450 mm × 450 mm and thickness of 80 mm were impacted by 0.5-kg hard steel projectiles. The concrete was designed to obtain an unconfined compressive strength of 48 MPa. An initial stress of 10% magnitude of compressive strength was induced by 4-mm-diameter high-tensile-strength (1700 MPa) steel wires in prestressed concrete targets. A grid of 8-mm-diameter steel bars was inserted in the reinforced and prestressed concrete targets to enable the straight comparison between these concretes. The prestressing in concrete has been found to be effective in reducing the volume of scabbed material as well as the ballistic resistance of prestressed concrete targets. The ballistic limit of prestressed concrete with 10% induced stress was found to be, respectively, 14% higher than that of the plain concrete target and 10.2% higher than the reinforced concrete. Failure modes predicted through finite element simulations were found in agreement with that of the actual results.

Ballistic performance evaluation of ceramic tiles with respect to projectile velocity against hard steel projectile using DOP test

The effect of backing material, projectile velocity and tile thickness on the ballistic efficiency of ceramic materials was studied against 7.62 mm AP projectile in depth of penetration (DOP) test configuration. An analysis on variation in differential efficiency factor (DEF) with respect to backing material was carried out. The factor responsible for variation in DEF was eliminated using a normalization method. A new definition (NDEF/ NBE) is proposed for calculation of ballistic efficiency. Using the new definition a comparison of ballistic efficiency of hot pressed boron carbide, alumina and zirconia toughened alumina were done for different projectile velocities and tile thickness. The DEF was found to increase with increase in projectile velocity, but NDEF and NBE were found to decrease with increase in projectile velocities. Even though the DEF, NDEF and NBE have produced different ballistic efficiencies they all have produced similar trends with respect to tile thickness.

Ballistic performance of plain, reinforced and pre-stressed concrete slabs under normal impact by an ogival-nosed projectile

The ballistic performance of plain, reinforced and prestressed concrete targets of unconfined compressive strength 48MPa was studied experimentally against long rod steel projectiles. The square targets (450mm×450mm) of thicknesses 60, 80 and 100mm were subjected to normal impact by 1kg ogive nosed hardened steel projectiles of diameter 19mm and length 450mm. The reinforcement in the reinforced and prestressed concrete targets was provided with respect to φ8mm @80mm c/c both ways. An initial prestress of approximately 4–5MPa (10% of unconfined compressive strength) was also induced in the prestressed concrete targets with the help of 4mm diameter steel wires of ultimate tensile strength 1646MPa. The experiments were carried out at varying incidence velocities, 65 - 220m/s, and the results thus obtained with respect to extent and vicinity of damage, volume of spalling and scabbing as well as ballistic resistance for three distinct concretes have been compared and discussed. The reinforcement in the concrete has been found to be effective in minimizing the scabbing and spalling of material. The initial prestressing in the concrete, stimulated the globalization effect in the deformation process and thus improved the ballistic performance. The ballistic limit of reinforced concrete target was 11, 16 and 26% higher than plain concrete target for 60, 80 and 100mm thicknesses respectively. On the other hand, the ballistic limit of prestressed concrete targets was found to be 19, 25 and 35% higher than reinforced concrete, and 32, 45 and 70% higher than plain concrete target for 60, 80 and 100mm thicknesses respectively.

Ballistic resistance of 2024 aluminium plates against hemispherical, sphere and blunt nose projectiles

Numerical investigation has been carried out on 2024 aluminium plate targets against 12.7mm diameter hardened steel projectiles. The ballistic resistance of 1.27mm thick target was studied against a spherical ball as well as the hemispherical and blunt nosed cylindrical projectiles. The simulations were performed on ABAQUS/Explicit finite element code by modelling the target as deformable and the projectiles as rigid three dimensional surface. The Johnson-Cook (JC) elasto-viscoplastic material model was employed to predict the flow and fracture behaviour of the target. The objective of the study was to investigate the efficiency of the JC model to numerically reproduce the maximum target deflection and peak impact force caused by three distinct shaped projectiles during target perforation. Three different sets of JC parameters calibrated by different authors [20,21] for 2024 aluminium alloy were considered to simulate the performance of the target against each projectile and the results thus obtained were compared and validated through available experiments [24]. The failure mode, deflection and impact force obtained have been noticed to have significant influence of the material models. The ballistic limit of 1.27mm thick target was numerically computed against each of the three projectiles and validated through the Recht-Ipson model. The effective span and target thickness were also varied to investigate the influence on the maximum deflection and peak impact force.

Ballistic performances of concrete targets subjected to long projectile impact

Concrete is a widely used material in the construction of strategic and important structures such as nuclear containments, bridges, storage structures and military bunkers. In the present study perforation experiments and simulations on finite element code ABAQUS/Explicit have been carried out to understand the behavior of concrete against projectile impact. Penetration tests were conducted on square (450mm×450mm) targets of plain and reinforced concrete of unconfined compressive strength 48MPa. To investigate the effect of reinforcement, 8mm diameter steel grid was incorporated at the center of thickness of the target. The targets were subjected to normal impact by 0.5 and 1kg ogival nosed hardened steel projectiles of caliber radius head (CRH) 3 and length to diameter (l/d) ratio 23.7 and 11.8 respectively. The velocity regime of the projectile was considered in the range 43–178m/s. The results thus obtained were presented and influence there on the ballistic performance due to the variation in l/d ratio of projectiles have been discussed. In comparison to plain concrete, the ballistic limit of the reinforced concrete target was found to have increased by 14%. A fair agreement was found between actual and predicted residual velocities obtained in the present study. The actual and simulated ballistic limit against 0.5kg projectile differed by 10.8% and 5.1% for plain and reinforced concrete target respectively. This deviation has been found to be 16.1% and 6.7% respectively against 1kg projectile.

Response of initially stressed concrete targets under high rate of loading

Prestressed concrete is a highly being used material in the construction of strategic and important structures such as nuclear containments, bridges, storage structures and military bunkers. It is highly durable, fire and corrosion resistant and nonporous. In order to study the influence of prestresing on the ballistic characteristics of concrete targets ballistic experiments have been carried out against ogival nosed (3 CRH) hard steel projectiles. The projectile of 0.5 kg mass were normally impacted on 80 mm thick presstressed concrete targets of plan size 450 mm x 450 mm. The unconfined compressive target strength of concrete was designed 48 MPa. An initial stress of 10% magnitude of compressive strength was induced by 4 mm diameter high tensile strength (1700 MPa) steel wires in prestressed concrete targets. A grid of 8 mm diameter steel bars were inserted in the reinforced and prestressed concrete targets to enable the straight comparison between these concretes. The prestressing in concrete has been found to be effective in reducing the volume of scabbed material as well as the ballistic resistance of prestressed concrete targets. The ballistic limit of prestressed concrete with 10% induced stress was found to be 10.2 % higher than that of the reinforced concrete and 14% higher than the plain concrete target, respectively.

Impact behavior of plain, reinforced and prestressed concrete targets

The ballistic enactment of plain, reinforced and prestressed concrete targets of unconfined compressive strength 48MPa counter to 0.5kg hard steel projectiles was studied through ballistic experiments and numerical investigation in finite element code ABAQUS. The square targets of dimensions 450mm×450mm and two thicknesses of 60, and 100mm were subjected to normal impact by 0.5kg ogive nosed hardened steel projectiles of shaft diameter 19mm and length 225mm. An initial stress of around 4–5MPa (10% of unconfined compressive strength) was also induced in the prestressed concrete targets. The ballistic experiments were carried out at varying striking velocities in the range of 100–255m/s, and the results thus acquired with respect to magnitude and vicinity of damage, volume of spalling and scabbing as well as ballistic resistance for three different concretes have been compared with their numerical reproductions. The induced prestressing in the concrete, stimulated globalization in deformation and thus enhanced the ballistic resistance of the target. The prestressing in the prestressed concrete has been found most prominent in minimizing the scabbing and spalling of target followed by reinforcement in the reinforced concrete.

Experimental and analytical investigation into large ductile transverse deformation of monolithic and multi-layered metallic square targets struck normally by rigid spherical projectile

This paper introduces an experimental and analytical investigation of the large ductile transverse deformations of monolithic and multi-layered metallic square targets made of either aluminum alloy or mild steel or a combination of these materials struck normally by rigid spherical projectile. The experiments have been carried out by a single stage gas gun impact test apparatus and 25.1g hard steel projectile with different velocities ranging from 42 to 158m/s. By assuming an exponential transverse deformation shape function, a new analytical model is derived based on energy method and upper bound solution. A modification to the applied kinetic energy is created by assuming a localized distribution for initial impact velocity which provides quantitatively and qualitatively better analytical results and have acceptable consistency with experimental ones. The analytical results show that 15 out of 62 data are located on solid line, where the experimental and analytical values of final displacement are equaled. Also, 98% of data are set in the reliable range.

Optimization of the Structure of a Ceramic-Aluminum Alloy Composite Subjected to the Impact of Hard Steel Projectiles

The optimization process for a composite panel with an Al2O3-AA2024 percolation phase subjected to a perpendicular impact of a 7.62 × 54R B32 Armor Piercing projectile is described. It is found that metal-matrix composite/ceramic-matrix composite structures have a lower ballistic resistance than structures in which a hard layer supported by a plastic one. Optimization revealed that the best composite panel with an Al2O3-AA2024 percolation phase could be obtained when the probability distribution of individual materials was described by a highly nonlinear function.

Experimental Study of Plain and Reinforced Concrete Targets Subjected to Impact Loading

In order to study the influence of the plain concrete and reinforced concrete on ballistic performances. Penetration tests were conducted on different thicknesses of plain concrete and reinforced concrete plates having 40Mpa unconfined compressive strength and reinforcement of 8mm diameter steel mesh in reinforced concrete plates is incorporated. The plates were 450mm of diameter and 60mm, 80mm, 100mm thicknesses are studied. The plates were subjected to an impact of hard steel projectile with ogive nose weighing 1kg with diameter 19mm and length of 450mm. The projectiles were accelerated by the laboratory pneumatic gun to velocities range between 28m/s to 102m/s. impact and residual velocities were measured by the high speed digital camera system. Ballistic resistance of plain concrete and reinforced concrete at different thicknesses had been find out in the experiments and compared with already proposed analytical formula. The results thus obtained are presented and influences there on due to the variation in the concrete plate thicknesses to the projectile impact are discussed. The ballistic limit was found to increase with an increase of target thickness.

An experimental study on the projectile defeat mechanism of hard steel projectile against boron carbide tiles

Failure mechanism of 7.62 mm AP projectile impacting boron carbide tiles was studied by post ballistic examination of the failed projectiles. It is found that the projectile failure originates simultaneously from at least two locations in the projectile during ballistic impact, one originating from the target interaction front of the projectile and another from a location near the tail end of the projectile. The failure origination from the target interaction front of the projectile is due to severe deformation at the interaction front. The second failure origination from locations near tail end of the projectile is due to stress wave generated micro-cracks. At the target interaction front of the projectile a temperature rise of above 1160 °C has been estimated. No remarkable change in failure mechanism of the hard steel projectile with respect to tile thickness (5–9.2 mm) or projectile velocity (600–820 m/s) has been observed. The variation in remnant projectile weight with respect to tile thickness and projectile velocity can be attributed to the change in duration of dwell or total projectile interaction time with ceramic target.

Effect of confinement on thick polycarbonate plates impacted by long and AP projectiles

The penetration process in unconfined and confined thick polycarbonate (PC) plates was investigated experimentally and numerically. The confinement was applied by insertion of the PC plate into a conical steel ring. The response of such plates to the impact of long hard steel projectiles, having an ogive-head shape in the range of velocities of 151 < V < 271 [m/s], was investigated experimentally. The results indicate that confinement results in slightly shallower depths of penetrations. Failure parameters which were determined to fit these experimental results served in simulations of these results, and also to those of a 7.62 [mm] AP projectile impacting unconfined PC targets at velocities 600 < V < 900 [m/s]. A very good agreement regarding the trajectory of the projectile was obtained. The resisting force to the penetration depends on the failure strain, whose dependence on triaxiality, temperature and strain rate, should be further investigated. The triaxiality is defined as the ratio: tr = σm/σeq where σm = σii/3 and σeq is the Mises equivalent stress. The numerical results show that the confinement introduces a negative triaxiality within the confined plates prior to impact. The shallower penetration in confined targets is due to the higher negative triaxiality which reduces the ductile damage during penetration, while the hydrostatic pressure reduces the brittle fracture mechanism.

Deformation and fracture behavior of steel projectiles impacting AD95 ceramic targets-experimental investigation

The deformation and failure behaviors of soft and hard steel projectiles and ceramic targets during normal impact at different velocities were investigated experimentally. Impact tests were conducted with light gas guns over a range of velocities from 100 to1000 m/s. The projectile and target, including fragments, were recovered after each test. Experimental results show that, with the impact velocity increasing, for the soft projectiles, the deformation and fracture modes were mushrooming, shear cracking, petaling and fragmentation (with relatively large fragments and lower number), respectively, while for the hard projectiles there are three deformation and fracture modes: mushrooming, shearing cracking and fragmentation (with very small fragments and large number). Velocity ranges were identified for each failure mode. In all tests, projectiles were rebounded and did not fully penetrate the ceramic targets. However, as a function of the velocity, the failure mode of ceramic target changed. At low impact velocity, only radial cracks formed. As impact velocity increased, circumferential cracks could be seen. A conical region of was ejected from the rear of the ceramic target when the velocity reached 400 m/s or above. The portion of the target affected by the conical ejected region took on two separate forms: front surface intact at lower velocity and perforated at higher velocity. At the higher impact velocities, the fragment size in the ceramic cone is smaller and more of a uniform distribution. No obvious difference in the damage to the ceramic target is seen with projectiles having different hardness but impacting at the same velocity range.