APM2 Bullets Research Articles

Ballistic performances of Ramor 500, Armox Advance and Hardox 450 steels under monolithic, double-layered, and perforated conditions

This study investigates the ballistic impact response of two armor steels (Armox Advance and Ramor 500) and a structural wear-resistant steel (Hardox 450) in monolithic, double-layered, and perforated plate configurations. As ammunitions, 7.62 mm NATO Ball, 7.62 × 51 AP (armor piercing), and 12.7 mm APM2 bullets were used in the ballistics tests. The tests were performed per EN 1522/1523 ballistic test standards and at FB6 and FB7 levels. The results showed different perforation behaviors for different plate configurations. All the monolithic plates were perforated with 7.62 mm AP bullets except for Armox Advance. Double-layered plate configurations, on the other hand, showed resistance to penetration. Among those, only the Ramor500 + Ramor 500 double-layered plate configuration was perforated by 7.62 mm AP bullets. All the pre-perforated plate configurations resulted in total protection regardless of ammunition type and plate materials.

Komparativna računarska analiza NATO 5,56 mm, APM2 7,62 mm i AK-47 7,82 mm metka koji se kreće brzinom od 2,0 maha u neposrednoj blizini zida

Comparative Computational Analysis of NATO 5.56 mm, APM2 7.62 mm and AK-47 7.82 mm Bullet Moving at Mach 2.0 in Close Vicinity to the Wall Various rifles require unique bullets. Each bullet has its capability, speed, and impact on the target. In metropolitan warfare, several bullets are shot close to the solid walls. These near walls affect the pressure distribution over the entire asymmetric bullet. The influence of a reflected shock depends on the angle at which it was reflected and the altitude from the ground to the body of the bullet. The current research emphasizes three bullets of varying diameters used in different types of guns. The first bullet is of NATO 5.56 mm, the second is APM2's 7.62 mm bullet, and the third is a 7.82 mm bullet from an AK-47 rifle. For 2-D steady computations, the supersonic speed of Mach 2 is considered to analyze the flowfield across all three bullets. The heights of the bullet are taken considering the height-to-diameter ratios (h/D ratio) from 0.5 to 3.0. The Mach contour drawn from the numerical simulations is used to analyze the flowfield, and aerodynamic coefficients like lift, drag, and moment are also plotted to analyze the ground effects on the projectile. The comparative analysis showed that the trend of shock wave reflections was similar in the bullets till h/D of 1.5. The APM2 bullet experienced maximum drag, followed by AK-47's 7.82 mm and NATO's 5.56 mm bullet. The 7.82 mm bullet experienced maximum lifting force at h/D = 1.0 due to its larger surface area than the other two ammo. The 7.82 mm bullet experienced a nose-up moment, whereas the other two faced a nose-down moment. As the altitude of the bullets from the ground increased, the ground effect appearing on the bullets reduced. The present comparative analysis research shows that it is suitable to fire an AK-47 bullet from h/D greater than 2.0 and the other two bullets from an altitude greater than or equal to h/D of 3.0.

Correction to: Perforation of Steel Plates with 7.62 mm APM2 Bullets

Correction to: Perforation of Steel Plates with 7.62 mm APM2 Bullets

On the ballistic perforation resistance of additive manufactured AlSi10Mg aluminium plates

Materials and structures made through additive manufacturing (AM) have received a lot of attention lately due to their flexibility and ability to customize structural components of complex geometry. One range of application not exploited so far is the use of additive manufactured metal plates for ballistic protection. In this study, plates of AlSi10Mg with dimensions 100 mm × 80 mm × 5 mm were manufactured in a powder-bed fusion machine. From the printed plates, material specimens were extracted and strained to fracture in uniaxial tension to reveal the mechanical response of the AM material. Metallurgical investigations were also conducted to study the microstructure of the as-built alloy both before and after testing. Next, the perforation resistance of the AM plates was disclosed in a ballistic range. During testing, the plates were impacted by 7.62 mm APM2 bullets at various velocities. In an additional test series, only the hard core of the same bullet inserted in a sabot was fired towards the plates. Based on high-speed camera images, the initial and residual velocities of the different bullets were measured, and the ballistic limit curves and velocities were determined. For comparison, the studies described above were repeated on a traditionally die-cast block of AlSi10Mg having the same chemical composition as the powder used in the 3D printing. Finally, based on the conducted material tests a standard constitutive relation and failure criterion, frequently used in ballistic impact simulations, were calibrated based on inverse modelling. Finite element models of the ballistic impact problems were established in ABAQUS/Explicit, and the numerical results were compared to the experimental data. Good agreement between predicted and experimental results was in general obtained, even though no special measures were undertaken concerning the fact that the target material was additively manufactured.

A Scaling Law for APM2 Bullets and Aluminum Armor Plates

In a previous paper, we presented a scaling law for the ballistic-limit velocity for the 7.62 mm APM2 bullet and five aluminum alloy plates. This scaling law predicts that the ballistic-limit velocity is proportional to the square root of the product of the plate thickness and a material strength term. In this note, we show that this same scaling law can be used to accurately predict ballistic-limit velocity for the larger 12.7 mm APM2 bullet.

Ballistically equivalent aluminium targets and the effect of hole slenderness ratio on ductile plate perforation

The concept of ballistically equivalent metals for ductile plate perforation has been defined and demonstrated for five aluminium alloys. Heuristic derivation of a semi-empirical relation between specific cavitation energy sc and hole slenderness ratio h/D (the ratio between plate thickness h and projectile nose base diameter D which is also known as the normalized plate thickness) has exposed a logarithmic dependence which is verified by experimental data. A closed-form logarithmic expression for sc which takes into account the h/D effect has led to a closed-form formula for the ballistic limit. The expression for sc is based on the spherical cavitation yield stress YcS which serves as a scaling yield stress for strain-hardening (softening) response. It is found that ballistically equivalent metals should have practically the same values of YcS and elastic modulus. The perforation of aluminium targets by 7.62 mm APM2 bullets is discussed and vast amount of experimental data is used to validate the particular ballistic limit formula. Application of the closed-form model is also demonstrated with connection to the more general concept of ballistically equivalent targets. The h/D effect on perforation of multilayered targets is examined and it is found that for ductile plate perforation the ballistic limit of a monolithic target is higher than the ballistic limit of any combination of its air-gapped parts. Under the constraint of n air-gapped protective layers with total thickness h the minimum ballistic limit is obtained for n identical layers.

Perforation of 6082-T651 Aluminum Plates with 7.62 mm APM2 Bullets at Normal and Oblique Impacts

We conducted an experimental study to understand the mechanisms and dominant parameters for 7.62 mm APM2 bullets that perforate 6082-T651 aluminum armor plates at oblique impacts. The 7.62-mm-diameter, 10.7 g, APM2 bullet consists of a brass jacket, lead filler, and a 5.25 g, ogive-nose, hard steel core. The brass and lead were stripped from the APM2 bullets by the targets, so we conducted ballistic experiments with both the APM2 bullets and only the hard steel cores. These projectiles were fired from a rifle to striking velocities between 400 and 1,000 m/s into 20-mm-thick plates at normal impact (β = 0o) and at oblique angles of β = 15o, 30o, and 45o. Measured residual and ballistic-limit velocities for the full bullet and the hard core were within a few percent for normal impact and all oblique angles. Thus, we showed that the perforation process was dominated by the hard steel core of the bullet. In addition, we conducted large strain, compression tests on the 6082-T651 plate material for input to perforation equations derived from a cavity-expansion model for the steel core projectiles. Model predictions were shown to be in good agreement with measured ballistic-limit and residual velocity measurements for β = 0o, 15o, and 30o. We also presented a scaling law for the bullet that showed the ballistic-limit velocities were proportional to the square root of the product of plate thickness and a material strength term.

Analysis on the Perforation of Ductile Metallic Plates by APM2 Bullets

By employing the theoretical model of a rigid sharp-nosed projectile perforating the ductile metallic target plate, the present paper reanalyzes the previously published experimental data of APM2 bullet and its hard steel core perforating aluminum armor plates and high-strength steel plates, respectively. Although the bullet deforms during the perforation, the tests confirmed that the perforation is dominated by the hard steel core whereas the brass jacket, lead cap and end cap have limited influence on the perforation. Therein the perforation model of a rigid sharp-nosed projectile may be conducted to analyze the perforation of APM2 bullet. With increasing the thickness of ductile metallic target plate, the inertia effect of target will arise and obviously affect the terminal ballistics. The inertia effect of target must be considered in the scenario of thick target plate. The experimental analysis further confirms that, the ballistic limit is proportional to the square root of target strength and target thickness.

Effects of heat treatment on the ballistic properties of AA6070 aluminium alloy

The ballistic properties of the aluminium alloy AA6070 in different tempers are studied, using target plates of 20 mm thickness in tempers O (annealed), T4 (naturally aged), T6 (peak strength) and T7 (overaged). The stress–strain behaviour of the different tempers was characterised by quasi-static tension tests and was found to vary considerably with temper in regards to strength, strain hardening and ductility. Ballistic impact tests using 7.62 mm APM2 bullets were then carried out, and the ballistic limit velocities were obtained for all tempers. In the material tests it was shown that the O-temper was most ductile and almost no fragmentation took place during the ballistic impact tests. The T6-temper proved to be least ductile, and fragmentation was commonly seen. The experiments show that despite fragmentation, strength is a more important feature than ductility in ballistic impact for this alloy, at least for the given projectile and within the velocity range investigated. A thermoelastic–thermoviscoplastic constitutive relation and a ductile fracture criterion were determined for each temper, and finite element analyses were performed using the IMPETUS Afea Solver with fully integrated 3rd-order 64-node hexahedrons. The numerical simulations predicted the same variation in ballistic limit velocity with respect to temper condition as found in the experiments, but the results were consistently to the conservative side. In addition, analytical calculations using the cylindrical cavity expansion theory (CCET) were carried out. The ballistic limit velocities resulting from these calculations were found to be in good agreement with the experimental data.

Analysis on Perforation of Ductile Metallic Plates by APM2 Bullets

By employing the theoretical model of a rigid sharp-nosed projectile perforating the ductile metallic target plate, the present paper re-analyzes the previously published experimental data of APM2 bullet and its hard steel core perforating aluminum armor plates and high-strength steel plates, respectively. Although the bullet deforms during the perforation, the test confirms that the hard steel core dominates in the perforation but the brass jacket, lead cap and end cap only have limited influence on the ballistics. Therein the perforation model of a rigid sharp-nosed projectile may be conducted to analyze the perforation of APM2 bullet. With increasing the thickness of ductile metallic target plate, the inertia effect of target will arise and obviously affect the terminal ballistics. The inertia effect of target must be considered in the scenario of thick target plate.

Normal and oblique impact of small arms bullets on AA6082-T4 aluminium protective plates

Normal and oblique impact on 20 mm thick AA6082-T4 aluminium plates are studied both experimentally and numerically. Two types of small arms bullets were used in the ballistic tests, namely the 7.62 × 63 mm NATO Ball (with a soft lead core) and the 7.62 × 63 mm APM2 (with a hard steel core), fired from a long smooth-bore Mauser rifle. The targets were struck at 0°, 15°, 30°, 45° and 60° obliquity, and the impact velocity was about 830 m/s in all tests. During testing, the initial and residual bullet velocities were measured by various laser-based optical devices, and high-speed video cameras were used to photograph the penetration process. Of special interest is the critical oblique angle at which the penetration process changes from perforation to embedment or ricochet. The results show that the critical oblique angle was less than 60° for both bullet types. A material test programme was also conducted for the AA6082-T4 plate to calibrate a modified Johnson–Cook constitutive relation and the Cockcroft–Latham failure criterion, while material data for the bullets mainly were taken from the literature. 3D non-linear FE simulations with detailed models of the bullets were finally run. Good agreement between the FE simulations and the experimental results for the APM2 bullets was in general obtained, while it was more difficult to get reliable FE results for the soft core Ball bullets.

Perforation of 7075-T651 Aluminum Armor Plates with 7.62 mm APM2 Bullets

We conducted an experimental and analytical study to better understand the mechanisms and dominant parameters for 7.62 mm APM2 bullets that perforate 7075-T651 aluminum armor plates. The 7.62-mm-diameter, 10.7 g, APM2 bullet consists of a brass jacket, lead filler, and a 5.25 g, ogive-nose, hard steel core. The brass and lead were stripped from the APM2 bullets by the targets, so we conducted ballistic experiments with both the APM2 bullets and only the hard steel cores. These projectiles were fired from a rifle to striking velocities between 600 and 1,100 m/s. Targets were 20 and 40-mm-thick, where the 40-mm-thick targets were made up of layered 20-mm-thick plates in contact with each other. The measured ballistic-limit velocities for the APM2 bullets were 1% and 8% smaller than that for the hard steel cores for the 20 and 40-mm-thick targets, respectively. Thus, the brass jacket and lead filler had a relatively small effect on the perforation process. Predictions from a cylindrical cavity-expansion model for the hard steel core projectiles are shown to be in good agreement with measured ballistic-limit and residual velocity data. The results of this study complement our previous paper with 5083-H116 aluminum target plates in that the ultimate tensile strength of 7075-T651 is about 1.8 times greater than that of 5083-H116. We also present a scaling law that shows a square root relationship between ballistic-limit velocity and plate thickness and material strength.

Perforation of 5083-H116 Aluminum Armor Plates with Ogive-Nose Rods and 7.62 mm APM2 Bullets

We conducted an experimental and analytical study to understand the mechanisms and dominant parameters for ogive-nose rods and 7.62 mm APM2 bullets that perforate 5083-H116 aluminum armor plates. The 20-mm-diameter, 95-mm-long, ogive-nose, 197 g, hard steel rods were launched with a gas gun to striking velocities between 230–370 m/s. The 7.62-mm-diameter, 10.7 g, APM2 bullet consists of a brass jacket, lead filler, and a 5.25 g, ogive-nose, hard steel core. The brass and lead were stripped from the APM2 bullets by the targets, so we conducted ballistic experiments with both the APM2 bullets and only the hard steel cores. These projectiles were fired from a rifle to striking velocities between 480–950 m/s. Targets were 20, 40, and 60-mm-thick, where the 40 and 60-mm-thick targets were made up of layered 20-mm-thick plates in contact with each other. The measured ballistic-limit velocities for the APM2 bullets were 4, 6, and 12% smaller than that for the hard steel cores for the 20, 40, and 60-mm-thick targets, respectively. Thus, the brass jacket and lead filler had a relatively small effect on the perforation process. In addition, we conducted large strain, compression tests on the 5083-H116 aluminum plate material for input to perforation equations derived from a cavity-expansion model for the ogive-nose rods and steel core projectiles. Predictions for the rod and hard steel core projectiles are shown to be in good agreement with measured ballistic-limit and residual velocity data. These experimental results and perforation equations display the dominant problem parameters.

Surface strengthening using a self-protective diffusion paste and its application for ballistic protection of steel plates

This paper deals with surface strengthening of steel plates using a self-protective diffusion paste. During the surface strengthening process, a paste containing carbon, boron or similar is applied on the steel surface. In addition to serving as a source for the various diffusion ingredients, the paste protects the steel against contact with the environment, so no packing or gas protection is necessary. Thus, the handling is in general very simple, and the surface strengthening process can be performed in a conventional air furnace. The method provides the same type of surface strengthening that is obtained by more conventional methods. In this work, the main focus will be surface strengthening by carburizing, but also boronizing and boronizing followed by carburizing have been tested out. The methods have been applied to increase the ballistic resistance of the low-strength carbon steel NVE36 (with nominal yield stress of 355 MPa) against impacts from small-arms bullets. An empirical model combining diffusion depth, heat-treatment temperature and soaking time was established on the basis of a series of experimental data. By means of this equation, the various heat-treatment parameters can be predicted when others are chosen. Ballistic perforation tests using 7.62 mm APM2 bullets showed that the low-strength carbon steel after surface strengthening obtained a ballistic limit higher than that of Hardox 400, which is a wear steel with a yield stress of about 1200 MPa.

Time-Resolved Penetration of B$_{4}$C Tiles by the APM2 Bullet

Time-Resolved Penetration of B$_{4}$C Tiles by the APM2 Bullet