Armor Steel Research Articles

Numerical investigation on dynamic damage behavior of a novel N-shaped perforated armor plate under ballistic impact

Armor steel is widely used for ballistic resistance in military infrastructures and vehicles. However, the high areal density of monolithic steel plates presents challenges in balancing protection and maneuverability. This study focuses on a novel armor design, invented by the authors: An N-shaped perforated armor plate (NPAP). The NPAP consists of a perforated plate, an inclined plate, and a back plate. A validated finite element (FE) model was used to analyze the dynamic damage behavior of the NPAP target and projectile under ballistic impact. Numerical simulation revealed that the NPAP target combined the edge and obliquity effects, resulting in asymmetric interaction and causing yaw and fracture of the projectile. The kinetic energy of the steel core after penetrating the NPAP target decreased by 84.7–88.0% compared to the initial kinetic energy. The NPAP target showed a 20.7–43.9% lower residual depth of penetration (RDOP) compared to the monolithic target. Furthermore, the effects of the dip angle of the inclined plate and plate thickness configurations on the ballistic performance of NPAP were examined. The results indicated that the NPAP target’s ballistic performance is more susceptible to the impact location on the perforated plate with a larger dip angle of the inclined plate. Additionally, the NPAP target with a thin perforated plate and a thick back plate configuration exhibited better ballistic performance, given the constant thickness of the inclined plate.

Carbon Dioxide Corrosion Mechanisms: Historical Development and Key Parameters of CO2-H2O Systems

The recent failures in flexible pipes have motivated the exhaustive research of corrosion mechanisms on high-strength carbon steel armor wires that are the main structural compounds of those structures that mostly operate in seawater environments in the presence of carbon dioxide (CO2) and confined spaces. Recently, the literature reported discoveries about electrolyte properties (as Fe+2(aq)/HCO3-(aq.) ratio) and supersaturation, near neutral pH inside the confined space, multiphase reactions of contaminants present in CO2 gas, the formation and dissolution mechanism of FeCO3 film, and interaction of CO2 gas impurities with the corrosion scale. Therefore, this review is aimed at presenting an up-to-date narrative of the CO2 corrosion phenomenon in carbon steel, connecting background fundamentals with current data studies.

An innovative pulsed current arc welding technology for armor steel: Processes, microstructure, and mechanical properties

This study presents a novel pulsed current arc welding technology, specifically pulsed current gas tungsten arc welding (PC-GTAW), single and double pulse gas metal arc welding (SP/DP-GMAW), and dual process welding (D-process). This study aims to investigate the effectiveness of these welding techniques for armor steel weldments. This research focused on investigating the welding processes, resulting microstructures, and mechanical properties of welded joints. Based on the macrography analysis, it was determined that the weldments exhibit no signs of porosity, inclusions, or inadequate penetration. This finding substantiates the optimum settings for the weldment production process. The weldment optical microstructure, fusion, and heat-affected zone were examined in the weld interface. The microstructural properties of the FZ include δ-ferrite, austenite, bainite, and acicular martensite. The HAZ has a bainite-untempered martensite microstructure. The chemical composition and variations across the weldment (base, weld and HAZ) were identified. The grain borders contained greater quantities of Cr, Ni, Mn, Si, and Mo than those of the grain cores. EBSD revealed average weld zone grain sizes of 17.7 µm, 32.6 µm, 30.8 µm, and 24.6 µm for PC-GTAW, SP-GMAW, DP-GMAW, and D-Process, respectively.Furthermore, the hardness measurements showed a progressive transition across different regions. Additionally, the D-Process-fabricated material exhibited a maximum ultimate tensile strength of 872 MPa and an elongation of 4%. The mechanical properties exhibited by this new process variant exceed those of other weldments, indicating its potential for fabricating armor steel. The impact toughness demonstrated superior performance in all the weldments. Within this context, the new use of pulsed current advanced welding methods has shown the ability to generate welded parts of exceptional quality.

Arc-welded armour steel: A tailored and comparative study of its microstructure and mechanical properties

The present research aims to investigate and analyse the metallurgical features, including macrostructure, microstructure, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and electron backscatter diffraction. In addition, the mechanical properties of the arc welding specimens, encompassing hardness, tensile properties, and impact toughness at room temperature, were determined. The specimens were joined utilising various welding techniques, including gas tungsten arc welding, gas metal arc welding, shielded metal arc welding, and flux-cored arc welding. According to macrography, the weldments have no porosity, inclusions, or penetration. This confirms the optimal weldment fabrication process parameters. An optical microstructure analysis was conducted on various zones of the weldments. The weld fusion zone's microstructure reveals delta (δ) ferrite within the austenite matrix. A two-phase microstructure of bainite and untempered martensite is observed in the heat-affected zone. Scanning electron microscopy images at higher magnification reveal austenite and partially δ-ferrite phases. Energy-dispersive X-ray spectroscopy analysis showed higher chromium, nickel, manganese, silicon, and molybdenum concentrations on the grain boundary than in the matrix. According to electron backscatter diffraction, the average weld zone grain sizes for gas tungsten arc welding, gas metal arc welding, shielded metal arc welding, and flux-cored arc welding are 21.4, 35.8, 25.8, and 34.3 µm, respectively. In the heat-affected zone, the grain size decreased significantly. The welding region has lower mechanical properties than the heat-affected zone. All specimens produced using different welding processes had no cracking in the weld metal, including the fusion zone and border.

Effect of welding parameters on cruciform weld joints made of armor steel

Abstract It is aimed to examine the effect of welding parameters on cruciform welded joints. Armor steels are used in military applications such as tracked and wheeled armored vehicles. These steels are quenched and tempered steels and have high yield stress and hardness. Although the increase in carbon equivalent increases the ballistic level together with the hardness value, weldability decreases. Therefore, the welding parameters of these steels must be determined carefully. Before the welding, chemical analysis, macro examination, hardness test, tensile tests and ultrasonic examination were carried out to verify the material properties. After the verification tests, plates were welded with three different welding parameters to observe the changing of the mechanical properties. After the welding process, welded pieces were subjected to non-destructive tests to inspect the weld imperfections. After the inspection, welded specimens were subjected to hardness test, macro examination and tensile tests. In addition to these tests, weld penetration (WP) measurements were performed with a new assessment method. In this measurement method, unit of area takes into consideration instead of the unit of length. As a result, it is determined that with the increasing welding parameters although WP increase, hardness values in heat affected zone decrease.

Modeling and optimization of WEDM machining of armour steel using modified crow search algorithm approach

Modeling and optimization of WEDM machining of armour steel using modified crow search algorithm approach

Application of synchronized tandem welding to high-hardness armor steel

Several studies have been conducted to improve combat vehicle capabilities, such as the bulletproof performance of armor and fuel efficiency through weight reduction. Titanium alloys and ceramic materials are expensive and difficult to process; therefore, they can be applied only in specific locations. In addition, arc welding, which is relatively inexpensive compared with other welding processes, is widely used in industrial fields; however, because welding is often performed in multiple passes to join one part, the productivity is reduced. Therefore, in this study, mechanical properties were investigated according to production time and heat input by applying tandem pulse gas metal arc welding (GMAW) to increase productivity. The experimental data were obtained by varying the wire feeding speed. In addition, the current–voltage waveforms were measured, and the volume shift was analyzed by comparison with images captured using a high-speed camera. To analyze the mechanical properties of the tandem weld for the welding of high-hardness armor plates, the appearance (top bead and back bead), cross-section, hardness, tensile test, impact test, and spatter generation of the welded part were analyzed. The results show that all Tank-automotive and Armaments Command (TACOM) standards for the base material were met when the tandem wire feeding speed was 11 + 11 m/min, and the single-pass process increased production speed by a factor of more than 10. Tandem pulse GMAW is shown to be a viable option for improving productivity and maintaining high-quality welds for high-hardness materials.

Possibility of obtaining rolled sheet from white iron with increased plasticity

Рroblem In the work, a study of the technology of manufacturing sheet metal up to 2 mm thick from white ledeburite cast iron alloyed with vanadium was carried out. Сast-iron purveyances forged preliminary. After forging purveyances were rolled with the different wringing out. At rolling a total degree of deformation was 70%. The additional annealing helped to bring down hardness of sheet and moulding of pipes became possible. White cast-iron has high plasticity because there are phase transformations in a vanadium eutecticum cementite. Goal. The goal of work is a study of sheet rolling of white cast-iron’s bars to use for the armour and weld-fabricated pipes. Methodology. Experimental cast iron contains 2.7 - 2.85% C and up to 2% V. 30 kg of castings were melted. The total degree of deformation was 70%. After forging, rolling was carried out on a two-roll laboratory mill on rolls with a smooth barrel. Results. The technological scheme for the production of white cast iron forgings is applied, which includes preliminary annealing, forging with a degree of deformation from 10 to 15%, intermediate annealing and final forging with a total ε=70%. Оriginality The use of carbide transformation in vanadium-doped cementite made it possible to carry out combined pressure treatment and obtain sheets up to 2 mm thick from iron castings Preliminary hot forging greatly stimulates and accelerates the process of cementite disintegration into austenite and vanadium carbides during high-temperature exposure. Rolling of forging blanks was carried out and the influence of thermal and deformation parameters on the structure of cast iron was investigated. Рractical value. Application of final heat treatment after deformation of cast iron provides a level of mechanical properties that corresponds to the properties of high-strength armor steels, and the hardness indicators even exceed them. Thinner sheets of such cast iron can be used to create compositions of multilayer armor with increased ballistic resistance from several materials with different properties.

Characterization of Fillet Welded Armor Steel Performed by Robotic Gas Metal Arc Welding: Effect of Heat Input on Microstructure and Microhardness

Characterization of Fillet Welded Armor Steel Performed by Robotic Gas Metal Arc Welding: Effect of Heat Input on Microstructure and Microhardness

The Influences of Nb Microalloying and Grain Refinement Thermal Cycling on Microstructure and Tribological Properties of Armox 500T

This study aims to investigate the combined effect of niobium (Nb) microalloying and austenite grain refinement, using a specific heat treatment cycle, on the microstructure and tribological properties of Armox 500T steel. In this work, Nb addition and thermal cycling were utilized for grain refinement and enhancement of the mechanical properties of Armox 500T alloy, to provide improved protection via lightweight armor steel components with a high strength-to-weight ratio. The kinetics of transformation of the developed Armox alloys were studied using JMATPro version 13.2. The samples were subjected to two austenitizing temperatures, 1000 °C and 1100 °C, followed by 4 min of holding time and three consecutive thermal and rapid-quenching processes from 900 °C to room temperature. Scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) was employed to analyze the microstructure, which primarily consists of four types of martensite: short and long lath martensite, blocky martensite, and equiaxed martensite. Additionally, a small percentage (not exceeding 3%) of carbide precipitates was observed. The wear characteristics of the investigated alloys were evaluated using a pin-on-disc tribometer. The results demonstrate that alloying with Nb and grain refinement using a thermal cycle significantly reduce the wear rate.

NUMERICAL ANALYSIS OF V-SHAPED PROTECTIVE PLATES AT VARIOUS ANGLES SUBJECTED TO BLAST LOADING – A COMPARATIVE ANALYSIS

The mechanical response of blast-resistant vehicles, such as Infantry Fighting Vehicles (IFVs), Mechanized Infantry Combat Vehicles (MICVs), Armored Personal Vehicles (APVs), and Mine-Resistant Ambush-Protected (MRAP) vehicles, is crucial for their effective design. When designing armored vehicles, it is important to achieve a balance between rigid designs that transmit blast forces to the troop's cabins and softer designs that prevent excessive structure deformation hazardous to the troops. This study investigates the performance of V-shaped plates at different angles under blast loading. The focus is on modeling blast effects using the Conventional Weapon (ConWep) method and the Johnson-Cook material model. The material used for V-shaped protective plates STRENX700 (S690QL) armor steel is commonly used for blast protection in Anti-Landmine (ALM) Vehicles. The blast-wave induces large deformation, erosion, high strain rates, non-linear material behavior and fragmentation. The numerical simulation results are presented in the form of vertical displacement of the central node on the protective plate, von Mises equivalent stress, and equivalent plastic strain.

Study on the protective performance of high-performance multi-scale (SiCh-p+B4Cp)/5083Al ceramic array armor with excellent ballistic properties

Ceramic array armor suffers from insufficient constrained capability of ceramic units in the embedded armor structure, leading to weak interfacial bonding at ceramic unit connections, significantly reducing the overall ballistic performance. In this study, centimeter-sized SiC hexagonal prisms and micrometer-sized B4C powders were used as reinforcing materials. A high-strength, high-toughness, and multiscale array (SiCh-p + B4Cp)/5083Al armor with strong interfacial bonding was prepared using pressure infiltration technique. The (SiCh-p + B4Cp)/5083Al armor was combined with ultra-high molecular weight polyethylene and 6252 armor steel to form an integrated armor system. To investigate the effect of constrained material on its ballistic performance, the array structures with epoxy and 5083Al as constrained material were prepared for comparison. Ballistic performance tests were conducted using 12.7 mm Armor-Piercing Incendiary (API). The damage mechanisms of the armor structure were studied through finite element simulation and a combination of macroscopic and microscopic analyses. The results demonstrate excellent overall ballistic performance of the (SiCh-p + B4Cp)/5083Al armor system. The high-strength and high-toughness 55 vol%B4Cp/5083Al composite material exhibits strong interfacial bonding with SiCh-p, providing robust support to the SiCh-p. The armor back deformation was reduced by 50 %, and the ceramic layer dissipated more than 70 % of projectile kinetic energy, The materials prepared in this study exhibit significant potential in ballistic performance.

Ballistic response of additively manufactured AA6061/AA7075 multistack plate for armor-piercing projectile

The current ballistics research study focuses heavily on substituting heavy metals with lightweight materials to make mobility more accessible and effective for all armor applications. To do so, the researchers found that aluminum alloys are the better alternative to substitute steel armor due to their high strength-to-weight ratio. Therefore, this research conducted ballistic studies on aluminum alloys using the Finite Element Analysis (FEM) methodologies and associated mathematical analysis. This Research primarily focuses on the damage factor, ballistic limit, and residual velocity of the bullet following penetration of target plates. In this investigation, the Johnson-Cook fracture and Recht-Ipson models were implemented on materials AA6061-T6 and AA7075-T6. The main objective of these models is to establish the damage factor and verify whether it is less than unity; if the factor is less than unity, it is eligible to study the residual velocity of the bullet after penetration into the target armor plate. The target plate was impacted with a 7.62 mm armor-piercing projectile with an impact velocity of 500 m/s. Monolithic plates of 18 mm thickness were evaluated initially. After that, the multilayered stack of each 3 mm thick plate was analyzed, and studied the effectiveness of using a multilayered stack armor plate.

High-velocity impact failure modeling of Armox 500T steel: Model validation and application to structural design

As an advanced fracture model, the Generalized Incremental Stress State dependent damage MOdel (GISSMO) provides non-linear damage accumulation formulation to better predict ductile fracture initiation associated with a wider range of material stress states. In this study, we simulate the high-velocity impact failure of Armox 500T steel through computational finite element modeling in the LS-DYNA/Explicit solver. Here, the GISSMO is used to describe the ballistic responses of the Armox 500T steel under dynamic impacts. Two sets of the most important parameters in the GISSMO (i.e., the fracture and instability surfaces) are determined for the Armox 500T steel. The GISSMO is calibrated in terms of the fade exponent and mesh regularization functions using the force–displacement curve of tensile tests extracted from the literature. The calibrated GISSMO is then scaled with the strain rate and validated by comparing quantitative measurements from ballistic experiments provided in the literature. Once validated, the model is then used to investigate the impact failure behaviors of Armox 500T steel by simulating bi-layer configurations consisting of an Armox 500T steel front plate and a rolled homogeneous armor (RHA) steel backing plate impact from a 20 mm fragment simulating projectile. The roles of the standoff distance and impact angle of obliquity on impact failure behaviors of bi-layered steel systems are explored. Altogether, results from this study provide new capabilities and insights into the design of armor structures with respect to lightweight and ballistic performance, and evaluation of impact failure behaviors of Armox 500T/RHA bi-layered systems.

A numerical ballistic performance investigation of Armox 500T steel through ductile damage models

In this work, the ballistic response of an armor steel, Armox 500T, is numerically investigated through finite element (FE) analysis by utilizing the Johnson–Cook (JC) and modified Mohr–Coulomb (MMC) damage models, with a focus on emphasizing the consequences of different modeling approaches. Although Lode-dependent failure models are considered to increase the accuracy of numerical predictions for ductile failure, there remains a complete lack of clarity as to whether all conditions and materials necessitate the adoption of such models for ballistic impact simulations. In this context, MMC and JC model parameters are calibrated through tensile test data available in the literature enabling direct comparison between them. Damage models are then validated using ballistic impact tests of Armox 500T performed with 7.62 API projectiles. The results indicate that the MMC model outperforms the JC model at predicting the failure modes while both models demonstrate strong performance in anticipating the residual velocity. The influence of projectile nose shape, target plate thickness, and impact angle are further investigated, and the effect of incorporating the Lode parameter is discussed in detail. Impact simulations with the blunt projectile nose shape is found to be highly sensitive to the effect of Lode angle on failure, with differences of up to 20% between models, while 7.62 API shows the lowest sensitivity. The difference between the models’ predictions is observed to increase at lower impact velocities and higher impact angles demonstrating the necessity of a Lode-dependent failure model for such cases. The JC model consistently yields smaller residual velocities compared to the MMC model in all cases indicating that the MMC is more conservative in terms of predicting protective performance of Armox 500T.

A Numerical Study on the Ballistic Performance of Projectiles Formed by Shaped Charge

Abstract In this work, a numerical analysis of shaped charge impact process is conducted to investigate the jet formation process and its penetration performance on metal targets. Numerical results are compared with experimental data from published literature for liners made up of copper and iron. Conical and bowl-shaped liner geometries are simulated with various configurations to observe their effects on projectile shape and penetration capability using the finite element (FE) method. The exact shape of the explosively formed projectile at the onset of impact is modeled as a rigid 3D body to simulate the penetration process. #45 and Armox 500T steels are used as the target materials, and the material behavior and failure mechanisms are modeled using the Johnson–Cook (JC) plasticity and damage models. In addition to the FE method, smoothed particle hydrodynamics (SPH) is utilized as well to evaluate its capacity in predicting the failure behavior of the metal targets. It is concluded that the FE method outperforms the SPH method at predicting failure modes, while SPH can still be used to predict residual velocity and hole diameters. Armox 500T demonstrates a higher impact resistance compared to #45 steel. Liner geometry is found to significantly affect penetration performance. Sharper and thinner projectiles formed from liners with small cone angles are shown to be highly efficient in penetrating through armor steel targets.

Fatigue-life prediction methods of a dynamic power cable for a floating testing platform – a numerical approach

Floating testing platforms and marine energy devices use Dynamic Power Cables (DPC) to connect to the testing centres or the national grids. These power cables are, therefore, an inherent component in the reliable operation of the floating structure, and their integrity throughout the design life of the device should be ensured from the early stages of the project. Fatigue failure is one of the most common factors affecting the cable's performance due to the cyclic loads caused by waves and currents. However, accurately estimating the fatigue life of DPC has proved challenging due to their material and geometric nonlinearities. In addition to fatigue failure, the cable design life is also characterised by its ability to withstand extreme conditions on-site.
 This paper addresses the design, analysis and specification of a dynamic power cable that will be deployed at the Biscay Marine Energy Platform (BiMEP) for the connection of the HarshLab 2.0, a floating testing platform for materials, subsystems and components developed and operated by Tecnalia. BiMEP is exposed to severe waves that induce large motions on the HarshLab buoy, and different numerical models for the analysis of the hydrodynamic response are reviewed and calibrated against model tests.
 To address a comprehensive study of the power cable at the design stage, this paper focuses on reviewing different fatigue-life prediction methods employed for a DPC, considering the damage in the steel armour and the conductor cores. It also covers the cable's response when the system operates under extreme sea conditions and the potential implications of sensitive variables such as loss of buoyancy and marine growth. To perform the fatigue-life study, long-term cyclic loading in each cable component was compared with its resistance to fatigue damage. In this case, the damage for each variable was derived from stress- and strain-based curves for the high-strength steel (armour) and the copper (core conductor) depending on the selected approach.
 The design iterative process using the studies performed in this paper led to the definition of a Lazy Wave design with a high-level optimisation of some components, e.g. the ballast and buoyancy modules and the bend stiffener. In general, the behaviour across the cable length is similar between the different fatigue-life approaches, with the most significant expected fatigue damage found in localised hot spots near the bend stiffener and the belly (sag-bend region) of the cable, before the buoyancy modules. It is found that, despite a significant difference across the magnitude of fatigue life estimated in sensitive areas, the final design complies with all design criteria and reaches a satisfactory fatigue life.

Investigation of additive manufactured micro-lattice structures for defence applications

Abstract This study investigates the blast mitigation capabilities of A286 steel micro-lattice structures produced through additive manufacturing. The research explores the effects of different manufacturing conditions, such as stress relief and heat treatment, on the mechanical properties and blast resistance of honeycomb and gyroid lattice structures in correlation with armour steel structures. Comprehensive evaluations, including surface morphology, corrosion resistance, and compressive residual stress analysis, reveal notable findings for micro-lattice structures. Micro-lattice structures demonstrated 57.23% higher corrosion resistance compared to conventional materials, presently available in the form of rolled homogeneous armour, medium hardness armour, and high-nitrogen steel. Additionally, honeycomb lattice structures exhibit compressive residual stresses of up to 581.90 MPa, providing significant advantages in blast mitigation potential. These results underscore the significance of lattice geometry, material microstructure, and residual stress in enhancing blast resistance. The research offers valuable insights into optimizing additive manufactured structures as an alternative modular solution for defence applications.

Pengaruh Metode Quenching dan Tempering Terhadap Kekerasan Material Hot rolled Plate (HRP) Steel

Hot rolled plate steel as a material to be used for steel armor needs to have the characteristics of a high hardness value. Medium carbon steel as the basic material is quenched at a temperature of 900 oC and tempering is carried out at a temperature of 125 oC and 175 oC with a holding time of 30 minutes. The Ms value is a benchmark for changes in martensite which is influenced by the constituent elements of the material. The use of water as a quench medium changes the structure of austenite to martensite. The martensite structure that occurs increases the optimum hardness value in HRP Steel material. The tempering process carried out above the Ms value causes a decrease in the hardness value. The highest hardness value was obtained in the quenching process with 542 HV which was influenced by the distribution of martensite. The decrease in hardness value occurs due to the tempering process, the average hardness value at temper 125 oC is 524.4 HV and 175 oC is 524 HV.

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.