Armour Steel Plates Research Articles

Dynamic mechanical properties and energy release characteristics of Mg-Na-Al alloy under impact load

To investigate the ignition behavior of Mg-Na-Al alloy under impact load and its mechanical properties under different strain rates, the universal testing machine and Separated Hopkinson Pressure Bar (SHPB) experimental system were used to conduct static and dynamic mechanical performance tests of Mg-Na-Al alloy, and the mechanical properties of Mg-Na-Al alloy under different strain rates were discussed. The light gas gun experimental setup was used to launch Mg-Na-Al alloy projectiles and impact rigid target plates to study the energy release behavior of Mg-Na-Al alloy under impact loads. Finally, based on the 12.7 mm ballistic gun experimental platform, the penetration of 12.7 mm armor-piercing projectiles equipped with Mg-Na-Al alloy wind caps into the homogeneous armor steel plates with a thickness of 15 mm, and the ignition test of the oil box behind the steel plates were conducted. The results indicate that the yield strength of Mg-Na-Al alloy under static compression is 265 MPa, while under high strain rates (from 2490 s−1 to 5640 s−1), the yield strength of Mg-Na-Al alloy is 406–423 MPa, which is 53∼60% higher than that under quasi-static compression. When reaching a certain impact velocity, the Mg-Na-Al alloy projectile breaks and induces ignition behavior, releasing energy. The 12.7 mm armor-piercing projectile equipped with an Mg-Na-Al alloy wind cap penetrated the homogeneous armor steel plate with a thickness of 15 mm and ignited. The released energy and the kinetic energy of the fragments ignited the oil box behind the steel plate.

Strain rate and temperature rate behavior of ultra-high-strength 1770 steel: Base for transverse impact analysis

The investigation was motivated by the widespread use of ultra-high-strength steels in cable-stayed bridges and armor steel plates. These structures are exposed to elevated risks from extreme loads, including vehicle impacts and blast loadings. The study aimed to investigate the mechanical properties of 1770 steel for applications in extreme conditions. The strain rates and temperatures ranged from 0.00095 s−1 to 1303 s−1 and 20 °C–900 °C, respectively. Tensile tests were conducted at various strain rates using a Split Hopkinson Tension Bar for dynamic testing and a universal testing machine for quasi-static testing at room temperature (20 °C). Quasi-static tension at elevated temperatures was carried out using an electromechanical testing machine coupled with a heating device. A uniform temperature distribution inside the specimens was ensured by a 30-min holding time. The results of the tensile test indicate that the 1770 steel displays notable thermal softening effects and strain rate hardening that differ from mild steel. The standard Johnson-Cook (J-C) model was found to be inadequate in accurately predicting the strain rate effects of this specimen. To address this issue, the strain rate parameter C in the standard model was adjusted to create the modified J-C model, which demonstrated good agreement with the experimental results. To further demonstrate the modified model and the identified parameters, drop hammer impact tests and corresponding numerical simulations were conducted. The impact test and numerical simulation results showed good agreement in terms of deformation and contact force. The mechanical properties and the constitutive models can serve as a design reference for the ultra-high-strength 1770 steel in extreme envirnments, as well as a theoretical basis for fitting material models of similar ultra-high-strength steels.

Experimental and numerical investigation on optimization of welding parameters and prediction of temperature distribution during shielded metal arc welding of ultra high hard armor steel joints

In this investigation, Ultra-high Hard Armor (UHA) steel plate by Shielded Metal Arc Welding (SMAW) process using the Austenitic Stainless Steel (ASS) electrode. In the first part of this investigation, using the finite element method (FEM), thermal analysis parameters were optimized using bead on plate welds in software code, known as SYSWELD. In the second part, using optimized parameters, a coupled thermo-mechanical analysis on multipass welded fabrication was carried out. Weld thermal cycles were analyzed by simulation and compared with experimentally measured temperature profiles. A double ellipsoidal heat source model was used to simulate the SMAW process. The heating rate and cooling rate were calculated along with residual stresses. This range of heating and cooling rate resulted in untempered martensite in the heat-affected zone (HAZ), confirmed by microstructure analysis and hardness mapping. Good validation was found between the measured and simulated 2D model with a 4–10% variation. This study suggests that numerical simulation is the capable technique in understanding the thermal and mechanical properties that influence the welding of ultra-high hard armor steels joints.

Experimental and Numerical Investigation of Bodywork Effect on High Hardness Armour Steel Against a 7.62 x 51 mm NATO Ball M80 Projectile

Small arms ammunition like the 5.56×45 mm NATO Ball and 7.62×51 mm NATO Ball projectiles constitute a significant threat to light armoured vehicles. These vehicles are mostly comprised of single-layered metallic high-hardness steel armour, but as an essential vehicle design feature, mild steel bodywork is externally mounted in certain areas for fenders, toolkit boxes, storage boxes, etc. over the main armour, i.e., high-hardness steel armour. These are necessary design features of vehicles, so they can’t be neglected regarding ballistic protection against threats. Also, to provide better ballistic protection in up-armoured vehicles, armour consisting of high-hardness steel armour is integrated or mounted just behind the existing bodywork of the car. Thus, this paper experimentally and numerically investigated the “bodywork effect,” which is also called the “K-effect,” and found that the configuration where the bodywork of mild steel is placed in front of high-hardness steel armour plate failed to provide better ballistic protection against the 7.62×51 NATO Ball M80 projectile fired at 0° angle of impact with a velocity of 833±20m/s from 10 m distance. However, the single high-hardness armour steel plate provided better ballistic protection than the configuration consisting of bodywork. For the validation of the experimental investigations, the arrangements were numerically simulated. The main aim of this work was to check the bodywork effect against this particular projectile and investigate factors contributing to the phenomenon.

Using an Internal State Variable Model Framework to Investigate the Influence of Microstructure and Mechanical Properties on Ballistic Performance of Steel Alloys

An internal state variable (ISV)-based constitutive model has been used within a Lagrangian finite element analysis (FEA) framework to simulate ballistic impact of monolithic rolled homogenous armor (RHA) steel plates by RHA steel spheres and cylinders. The ISV model predictions demonstrate good agreement with experimental impact data for spherical projectiles. A simulation-based parametric sensitivity study was performed to determine the influence of a variety of microstructural and mechanical properties on ballistic performance. The sensitivity analysis shows that the lattice hydrogen concentration, material hardness, and initial void volume fraction are dominant factors influencing ballistic performance. Finite element simulations show that variation of microstructure properties could explain the reduced ballistic performance of high hardness materials previously documented in the literature. The FEA framework presented in this work can be used to determine material properties conducive to ballistic-impact resistance.

On the effect of pitch and yaw angles in oblique impacts of small-caliber projectiles

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

Комбінований протиударний та протимінний захист на основі деталей з алюмінієвих сплавів

This paper considers the use of aluminum alloy parts for combined mine protection of armored combat vehicles. The study was concerned with anti-mine shields mounted on an armored combat vehicle body model. The model was made of 16 mm armor steel. The total mass of the model (without an anti-mine shield) was 31.1 kg. An anti-mine shield was gripped between two frames and secured with bolts. To eliminate the effect of the soil on the test results, the explosive charges were installed on a 70 mm metal plate. The charges were initiated with an ED-8Zh electrodetonator. TG-50/50 explosive was used. A DYTRAN 3200B acceleration sensor was mounted at the center of the model, and the sensor signal was measured using an experimental system. To assess the model acceleration without any energy loss by elastic or plastic deformations, the acceleration of the model with a rigid anti-mine shield (a rigid armor steel plate of thickness 10 mm and mass 10.7 kg) was assessed. A finite-element simulation of the model was conducted. The effect of explosion load parameters on the model acceleration was studied. The simulated and the actual deflections were compared using an EinScan Pro 2X Plus 3D scanner. The speed and the acceleration of the model with a rigid and a plastic anti-mine shield were simulated and measured. The results showed that annealed parts made of Al-Mg alloys, in particular AMg6 alloy, absorb the explosion energy better. Any of the anti-mine shields made of AMg6 alloy reduces the acceleration at the center of the plate and thus the load on the armored vehicle body by a factor of 20…25 in comparison with the anti-mine shields made of armor steel. It was shown that annealing best provides the required physical and mechanical characteristics of the load-bearing parts of anti-mine shields, it is advisable to shape and structurize their porous energy-absorbing elements by pressing up to 33 MPa, it is most advisable to paste the porous energy-absorbing elements to the load-bearing parts, and after separate tests of load-bearing part and porous energy-absorbing element material specimens it is advisable to try out combined constructions of anti-mine shields for armored combat vehicles of different purposes.

Failure analysis of composite plate under ballistic impact

Numerical models were used to evaluate the ballistic impact of common armour steel plates of medium thickness by give-nosed bullets travelling at explosive velocity. To understand the behaviour and breakdown of the material under impact situations, Johnson-Cook material and failure models have been employed. The model constants were derived using data from the authors' prior experimental work done. ANSYS 2019 R3 was used to simulate the situation. The penetration phases have been anticipated. The simulation findings were used to establish residual velocities, ballistic limit velocity, and perforation timings, which matched experimental data.

Effect of Explosive Shapes (in Sand Buried Condition) on the Failure of a Circular Clamped Plate of Protective Vehicle

Protective vehicles like armoured personnel carriers (APCs) require assessment of failure of structural elements subjected to impulsive load resulting from explosive blast under sand buried conditions. The explosive shape and location of detonation affect the failure in near field region. In the present study, a circular clamped Rolled Homogenous Armour (RHA) steel plate has been modelled using JC strength & damage model and explosive using JWL equation. Initially, the reflected pressure and specific impulse for a fixed quantity of explosive (3.75 kg) of various shapes i.e. sphere, hemisphere, cylinders with Length to Diameter (L/D) ratio varying from 0.1 to 1 were studied for sand buried at a standoff distance of 118.1 mm. Further, studies were extended for cylindrical charges of φ 213.77 mm with conical 120°-150° and hemispherical cavities with radius of R1.2-R1.8. It was observed that, reflected pressure and specific impulse is much higher for hemispherical cavity of R1.2. The permanent deformation obtained using non-dimensional impulse is valid for explosives without cavities. However, the cavity charges produce failure of plate in the central region of the charge. The critical impulse emerges as an important parameter for assessing failure due to cavity charges. In addition, the scale down experiment is conducted to validate the effectiveness of cavity charges. It can be concluded that cavity charge with hemispherical radius of R1.2 can provide highest damage to RHA plates in close standoff distance.

Prediction of Abrasive Waterjet Machining Parameters of Military-Grade Armor Steel by Semi-Empirical and Regression Models.

Rolled homogeneous armor steel (RHA) with a high tensile strength, toughness, and hardness is often used in military combat vehicles. RHA is a high-strength low alloy steel suitable for all battlefield usage in military vehicles. The present work examines the prediction output responses in the material removal rate (MRR), surface roughness (Ra), and kerf angle (Ka) for the AWJM of armor steel using regression and semi-empirical models. The AWJM trials were performed using an L27 factorial design with each process variable set to three levels, namely, the standoff distance (SOD), jet traversing speed (JT), and jet water pressure (P). A regression model was constructed using the response surface method (RSM) and data from the trials. Through dimensional analysis and with Buckingham’s π-theorem, a semi-empirical model was built using both the experimental data and material property data. Predictions made by the models were proportionate with the results of the experiments under the same conditions. Microscopic investigations on MRR and Ra were performed using a scanning electron microscope (SEM). The optimal values of the output responses of the machined armor steel plate were obtained with higher MRR = 298.92 mm3/min, lower Ka = 0.651°, and lower Ra = 2.23 µm. The present work established that semi-empirical models accurately predict the output responses in the AWJM of armor steel.

A numerical model for analysis of layer thicknesses on ballistic resistance of a multilayer armor

The interest in composite materials, which are lighter and have better mechanical properties (strength, fatigue resistance, corrosion resistance, etc.) than traditional engineering materials, is increasing day by day. In particular, their responses to low or high-velocity impact loads have been among the important research topics of recent years. In this study, unlike the traditional ceramic-based composite armor structures used in the defense industry, the effect of total carbon fibers specifically parallel oriented into impact direction on penetration resistance has been investigated, and penetration resistance of a multilayer hybrid composite armor which is composed of carbon fiber composite blocks sandwiched by two armor steel plates exposed to high-velocity impact has been analyzed numerically. Carbon fibers are normally very brittle to the transverse loading direction, contrarily, to their axial tension or compression direction. This is the reason why it is claimed that this high compression strength property of carbon fibers could be used as a layer in order to replace ceramics in add-on multilayer composite armor. The numerical model created in the ANSYS LS-DYNA program was verified by using the experimental data obtained in an earlier study. The verified numerical model was used to analyze high-velocity impact simulations of multilayer hybrid composite armor for different thicknesses of armor steel to reduce the areal density. By these simulations, minimum areal density compared to Rolled Homogeneous Armor steel for equivalent protection was finally achieved, and thus the hypothesis saying that carbon fibers parallel oriented to impact direction can give high penetration resistance was proved by showing that developed multilayer carbon fiber reinforced epoxy composite–armor steel hybrid panels have indicated a better protection level than STANAG 4569 Level-4 with a lower areal density.

A Comparative Study on Metallographic and Mechanical Properties of Armox 500T Armor Steel Plates Joined Using Different Arc Welding Methods

A Comparative Study on Metallographic and Mechanical Properties of Armox 500T Armor Steel Plates Joined Using Different Arc Welding Methods

The effect of weld-groove surface modification on the joint performance of military grade armour steel: A sustainability approach

The welding of armour grade steel plays a vital role in combat vehicle structures. A work is conducted to investigate the effect of Water Jet (WJ) and Flame Cutting (FC) on the metallurgical and mechanical properties of the welded armour steel plates. The sustainable WJ machining shall produce the weld groove by a single pass without heat formation in the cut surface, which is unavoidable in the flame cutting process. The results demonstrate that the WJ weld plate is more desirable, as the martensite structure is obtained in different Heat-Affected Zones (HAZ). It is achieved by one-time heat involvement compared to ferrite – pearlite structure in HAZ of the flame cut weld plate. A higher hardness of 335 HV is observed in the fusion zone of the WJ weld plate compared to 212 HV in the flame cut weld plate. The tensile failure occurs in the fusion zone of both water jet and flame cut weld plates and the fusion zone has a higher impact strength of 108 J (8 times higher than base plate). Thus, implementing sustainable WJ machining in preparing the weld groove enhanced the welding properties in military-grade armour steel.

High-Velocity Impacts of Pyrophoric Alloy Fragments on Thin Armour Steel Plates.

The terminal ballistics effects of Intermetallic Reactive Materials (IRM) fragments have been the object of intense research in recent years. IRM fragments flying at velocities up to 2000 m/s represent a realistic threat in modern warfare scenarios as these materials are substituting conventional solutions in defense applications. The IRM add Impact Induced Energy Release (IIER) to the mechanical interaction with a target. Therefore, the necessity of investigations on IIER to quantify potential threats to existing protection systems. In this study, Mixed Rare Earths (MRE) fragments were used due to the mechanical and pyrophoric affinity with IRM, the commercial availability and cost-effectiveness. High-Velocity Impacts (HVI) of MRE were performed at velocities ranging from 800 to 1600 m/s and recorded using a high-speed camera. 70 MREs cylindrical fragments and 24 steel fragments were shot on armour steel plates with thicknesses ranging from 2 mm to 3 mm. The influence of the impact pitch angle (α) on HVI outcomes was assessed, defining a threshold value at α of 20°. The influence of the failure modes of MRE and steel fragments on the critical impact velocities (CIV) and critical kinetic energy () was evaluated. An energy-based model was developed and fitted with sufficient accuracy the Normalised () determined from the experiments. IIER was observed in all the experiments involving MRE. From the analyses, it was observed that the IIER spreads behind the targets with velocities comparable to the residual velocities of plugs and shattered fragment.

Scaling the response of armor steel subjected to blast loading

The influence of the strain-rate effect of steel and the mechanical effect of explosive shock load are both key problems to achieving the similarity scaling of a steel plate structure under blast loading. In this research, the scaling of the dynamic response of strain-rate sensitive armor steel subjected to air blast loading was studied further. First, the specific impulse was defined, and the influence of the strain-rate and the geometric scaling ratio on the specific impulse correction factor was analyzed with dimensional analysis. Then, a real air explosion test was carried out to study the response of a full-size armor steel plate during a blast, and the Johnson-Cook constitutive parameters of the armor steel material were obtained using split Hopkinson pressure bar experimental technology, with which the accurate scaling base mode was established. Furthermore, by employing the correction factors of the specific impulse and the total impulse calculated by empirical equations, two correction methods were proven: I-correcting the stand-off distance and II-correcting the charge mass. Then, the relationships between the specific impulse, the total impulse, the stand-off distance and the charge mass are discussed, based on which the explosion load boundary corresponding to the geometric scaling coefficient was determined. The results showed that the prediction of the corrected scaled model was in good agreement with the experimental results, and both methods could achieve the scaling of the response of the armor steel plate subjected to blast loading.

Ballistic performances of Ramor 500 and Ramor 550 armor steels at mono and bilayered plate configurations

The ballistic performances of Ramor 500 and Ramor 550 armor steel plates were experimentally and numerically investigated at various conditions against 7.62 mm bullets. The experimental part of the study consists of the monolithic plate, double-layered plate, and oblique plate. For the monolithic plates, 6.7 mm thick Ramor 500 and 6.2 mm thickRamor550 were used. Plates were perforated and the failure mechanism ofpetallingwas observed. For the double-layered plates, 6.7 mm thick Ramor 500 and 6.2 mm thickRamor550 were layered at two different ordering structures. It was found that Ramor 550 as facing plate and Ramor 500 as backing plate exhibit better ballistic resistance than the configuration of the opposite layering order and the main failure modes of the targets were plugging and bulging. For the oblique plates, 4.5 mm thickRamor500 plates were impacted at 0°, 30°, and 60° impact angles. The result showed that the ballistic resistance of plates increased as the impact angle was increased.

Selected Issues of Increasing the Fire Effectiveness of Combat Vehicles

Abstract The research paper reviews selected issues associated with the current state of the armoured (tanks) and infantry fighting vehicle technology, with particular emphasis on the operating effectiveness of elongated sub-calibre projectiles fired from tank guns, which enable full perforation of ca. 500 mm thick armour steel plates. Their efficiency is comparable with the impact of shaped heads with armour steel penetration capabilities, and amounts from 6 to 8 calibres – warhead diameters. Furthermore, the paper discusses a numerical analysis, which shows the velocities of elongated projectiles (of tungsten matrix sinters) required to achieve a determined armour steel penetration depth. In addition, it also presents the performance characteristics of two 100 mm calibre shaped warheads, with copper inserts and apex angles of 51º and 60º.

Effect of tempering conditions on adiabatic shear banding during dynamic compression and ballistic impact tests of ultra-high-strength armor steel

In this study, roles of strain-hardening rate on susceptibility of adiabatic shear band (ASB) formation and subsequent cracking were investigated in two ultra-high-strength armor steel plates heat-treated differently. The quenched and tempered steel contained ~2% of retained austenite in the tempered martensitic matrix, while the quenched and austempered steel contained ~4% retained austenite in the bainitic matrix partly with the tempered martensite. The actual ballistic impact test results revealed the lower sensitivity of ASB formation in the austempered steel than in the tempered steel, which corresponded well to the higher critical strain for ASB formation in the dynamic compressive test using a laboratory-scale split Hopkinson pressure bar (SHPB). The austempered steel caused the higher internal stress among various constituents, and all the retained austenite transformed into martensite during the deformation, thereby leading to transformation-induced plasticity (TRIP) effect. The higher strain-hardening rate induced by these higher internal stress and TRIP effect increased resistance to ASB formation, which was confirmed by a calculation of ASB susceptibility. Thus, the austempered steel was much less susceptible to the ASB formation during the ultra-high-speed deformation. Consequently, the increased resistance to ASB formation retarded the initiation and propagation of ASBs and cracks.

Ballistic performance of unidirectionally oriented carbon fiber reinforced composite armor with high-velocity impact

For the last few decades, composite materials have been more popular than other conventional metal materials in the aircraft industry. Having better mechanical properties (strength, fatigue life, impact strength, corrosion resistance, etc.) and being lighter than conventional engineering materials, composites have become very important in defense industry as well. In spite of the fact that some of the composite materials such as aramid-based composites have been effectively used in body protection, they have not been so successful in heavy armored vehicles which are generally equipped with different types of add-on armor blocks for protecting against threats. These add-on armors are mostly composed of armor steels and ceramics. This study specifically aims to investigate high-velocity impact behavior of unidirectionally oriented carbon fiber reinforced/epoxy layer sandwiched with armor steel plates that are exposed to kinetic energy projectile. Carbon fibers are normally very brittle to transverse loading direction, contrarily, to its axial tension or compression direction. This is the reason why it is claimed that this high compression strength property of carbon fibers could be used for manufacturing a layer in order to replace ceramics in add-on multilayer composite armor. In order to prove this hypothesis, an experimental analysis has been carried out by performing impact tests on these manufactured add-on armor test samples. Testing was carried out in accordance with the STANAG 4569 level-4 standard. The results indicated that the multilayer carbon fiber reinforced epoxy composite–armor steel hybrid panels can provide level-4 protection with a lower areal density compared to Rolled Homogenous Armor.

Microstructure, mechanical, ballistic property evaluation of RHA steel produced by continuous-casting route

This paper presents the commercial production of rolled homogeneous armour steel with 5 different thicknesses i.e. 20,30,40,50 and 80 mm through continuous casting route. All the plates display tempered martensitic structure. Tensile and charpy impact properties are obtained for all the different thickness plates. It is observed that the produced steel shows a good combination of strength and impact toughness. For ballistic evaluation 30 mm thick plates are impacted with 30 mm medium caliber armour piercing steel projectiles at a velocity of 460±20 m/s at zero degree angle of impact. Depth of penetration method is used to measure the ballistic performance of the plates. From the post ballistic microstructural observations, an adiabatic shear band induced material removal is detected in the front face of the impacted rolled homogeneous armour steel plates. The microstructure, mechanical and ballistic properties of the continuous cast steel is compared with the steel produced by conventional ingot cast route.