Armor Steel Research Articles

Reliability Assessment by Factor of Safety on the Tensile Failure Behaviour on Military Grade Armour Steel Weldment

Reliability Assessment by Factor of Safety on the Tensile Failure Behaviour on Military Grade Armour Steel Weldment

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.

Design Against Failure of Battlefield Equipment Armor Steel

Design Against Failure of Battlefield Equipment Armor Steel

Effect of failure modes on ballistic performance of Gas Metal Arc welded dissimilar armour steel joints

In this study, Ultra-high Hard Armor (UHA) steel is welded with Rolled Homogenous Armor (RHA) steels using Gas Metal Arc Welding (GMAW) process with Austenitic Stainless Steel (ASS), Duplex Stainless Steel (DSS), and Low Hydrogen Ferritic (LHF) fillers. Ballistic resistance against Weld Metal (WM) is determined using 7.62 × 39 mm BALL projectile. Three new modes of failure were identified from the ballistic testing (i) Finer Wear Debris with Cleavage (FWDC) (ii) Coarser Wear Debris with Cleavage (CWDC) (iii) Cleavage failure (C), based on the fractured surface. All joints stopped the ball projectile at the weld metal region without perforation. However, the joint fabricated using ASS electrodes shows superior ballistic performance than other joints with Cleavage mode of failure (C) mainly due to the absence of wear debris. ASS weldment (5% Delta ferrite and 95% austenite) performs better in ballistic resistance because of the plastic deformation along with energy absorption properties of the austenite phase than DSS (69 Delta ferrite and 31% austenite) and LHF (100% ferrite). Migration of Chromium (Cr) from the weld metal to base metal results in an unmixed zone and martensitic band in the HAZ of ASS joint.

Study on the Penetration Power of ZrO2 Toughened Al2O3 Ceramic Composite Projectile into Ceramic Composite Armor.

This work aims to improve the penetration ability of a 14.5 mm standard armor-piercing projectile into ceramic/armor steel (Al2O3/RHA) composite armor. To this end, ZrO2 toughened Al2O3(ZTA) is prepared as the material for bullet tips, utilizing in situ solidification injection molding that is realized via ceramic dispersant hydrolytic degradation. The penetration power of ZTA ceramic composite projectile, compared with standard armor, against 15 mm armor steel (RHA) and 30 mm Al2O3/RHA composite armor, is studied by ballistics testing combined with numerical simulation. The Tate theory is optimized and then employed to calculate the penetration depth and bullet core’s residual mass when ZTA ceramic composite projectile penetrates into Al2O3/RHA composite armor. The results show that when penetrating RHA of 15 mm, the penetration area of ZTA ceramic composite projectile into RHA increases by 27.59% and the exit area by 42.93%. While the standard projectile fails to penetrate the 30 mm Al2O3/RHA composite armor, the ZTA ceramic composite armor-piercing projectile succeeds, with the mass loss reduced by 66.67% over the standard one. The ZTA ceramic composite bullet has a better performance than the standard bullet in penetrating RHA and Al2O3/RHA composite armors. The test results, simulation, and theoretical analysis are consistent. This study has practical values for engineering applications to design new ceramic composite bullets.

Prediction of welding residual stress and distortion in multi-layer butt-welded 22SiMn2TiB steel with LTT filling metal

The objective of this study is to investigate the influence of low transformation temperature (LTT) filling metal on residual stress and distortion in multi-layer butt-welded 22SiMn2TiB steel. A three-dimensional thermal elastic–plastic finite element model is developed for LTT filling metals, and metallurgical phase transformation is taken into account to predict the martensite fraction of the weld metal. A thermodynamic-based method is employed to calculate martensite start temperature (Ms) and the influence of dilution on Ms is also considered. Volume change due to austenite transformation during heating and martensite transformation during cooling are coupled with the numerical simulation of welding process. The evolution of welding residual stress and welding distortion are both predicted. The simulation results revealed that the distortion of welding plate using LTT filling metal is much smaller than that using austenitic metal. In the weld zone, transverse residual stress is lower using austenitic filling metal, but longitudinal stress is much smaller using LTT filling metal. Longitudinal stress distribution for both LTT and austenitic filling metals is very high in the heat-affected zone, which is close to the yield stress of base metal. The LTT filling metal can not only guarantee the strength of welded joint for armor steel, but also reduce the welding distortion obviously, and the residual stress is also very low at the same time. The predicted temperature profiles and welding distortion are generally in good agreement with the experimental ones.

Investigation of Power Consumption in the Machining of S960QL Steel by Finite Elements Method

Armor steels have good strength and corrosion resistance; however, due to their difficult machinability, high power consumption occurs. High power consumption increases the cost in machinability studies. Therefore, minimizing power consumption is important for sustainable and cleaner production. In order to minimize power consumption during machining, factors such as workpiece material, cutting tool material and geometry, machining conditions and cutting parameters must be compatible with each other. For this reason, power consumption modeling was carried out in the milling of S960QL structural steel material according to the finite elements method, depending on the cutting parameters. In this context, simulation processes were carried out at three levels for each factor: cutting speed, lateral depth, axial depth and feed rate. The most effective parameter in power consumption was the axial deep of cut. There was a 476% change between the highest and lowest power consumption. It is concluded that finite element modeling is feasible in order to determine the effect of processing parameters on power consumption.

Measurement and analysis of sustainable indicators in machining of Armox 500T armor steel

Armox 500T is a special type of armor steel possessing superior mechanical properties suitable for use in vehicles and buildings need for first priority protection. Since these products are large-scale, a welding groove needs to be created before joining which can be done by milling operations. This study aims to address this point by questioning the impact of clean environments, namely, dry, minimum quantity lubrication (MQL), and LN2-based cryogenic cooling on the machining performance measures during milling. The novelty of this paper is the investigation of the effects of different cutting environments on the milling performance of Armox 500T armor steel. The results from this study showed that cryogenic medium has an impressive impact on controlling the temperatures at tool-chip interface which directly reduces flank wear development. In addition, cryogenic and MQL-assisted machining is much better than dry environment in achieving improved surface properties, chip shape, and energy consumptions. Cryogenic cooling seems as the best option for hard milling pursued by MQL and dry environments, respectively, from the sustainability and machinability point of view.

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

Microstructural and Impact Considerations of Heat Affected Zone in Gas Tungsten Arc Welding of Armor Steel

Abstract Gas tungsten arc welding is a preferred welding process due to its excellent heat control which provides high quality joinings of various metals. Welded armor steels are widely used in armored vehicles for the ease of production. Thus, characterization of gas tungsten arc welding of armor steels reveals important data on both present applications and potential uses of gas tungsten arc welding in future. In this study, microstructural and mechanical properties of welded armor steel were investigated. Optimal welding parameters depending on a previous research were used to eliminate welding defects. The results have shown that application of pre-heating and/or multi-pass welding on armor steel could provide fine and homogeneously dispersed carbides in heat affected zone.

Microstructure modification of additive manufactured Ti-6Al-4V plates for improved ballistic performance properties

• Additive manufacturing of Ti-6Al-4V armour plates for ballistic testing. • Ballistic limit dependent on build direction due to microstructure anisotropy. • Lamellar α + β from martensitic decomposition resulted in better ballistic limit. Titanium alloys such as Ti-6Al-4V offer a potential lightweight alternative to traditional armour steels for ballistic protection due to their reduced density of approximately 60 % that of steel and tensile properties better than rolled homogenous armour steel. The manufacture of metallic armour often requires substantial thermomechanical processing to meet necessary ballistic performance specifications and thus restricts the complexity of armour designs. Additive manufacturing of Ti-6Al-4V has matured significantly in recent years, achieving outstanding mechanical properties in the as-built condition. In this study, Ti-6Al-4V plates were additively manufactured using both laser powder bed fusion and direct laser metal deposition for ballistic testing. The plates were built in different orientations and subjected to pre-heating or post heat-treatment to investigate the microstructural effect on the ballistic velocity limit (V 50 ). The results show that plates with lamellar microstructure formed through martensite decomposition had higher V 50 compared to lamellar microstructure formed via slow cooling through the β-transus. The post heat-treatment increased the V 50 due to coarsening of the α-lath and stress relief. It is also apparent that anisotropy of the microstructure, specifically the columnar prior-β grains, affects the ballistic performance. A higher V 50 was achieved when the columnar grains were aligned perpendicular to the projectile impact direction.

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.

Adiabatic shear bands produced in a metallic armor, after dynamic compression with a Hopkinson pressure bar

A Brazilian high hardness armor (HHA) steel was, for the first time dynamically tested and microstructurally analyzed for the occurrence of shear bands. The HHA was initially quenched at 910 °C for 10 min and tempered at 310, 425 and 610 °C for 1 h to produce different microstructures as well as phases and precipitates. After characterizing the microstructures, a dynamic compression test on a Hopkinson bar was performed on special samples to simulate high deformation rate in a ballistic impact. Then, a search for adiabatic shear bands, using scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) was performed on the impacted samples. The transformed shear bands generated were characterized by X-ray diffraction (XRD) and electron backscattering diffraction (EBSD). The results showed that the microstructure generated in the tempering heat treatment at 310 °C is the most susceptible to the appearance of shear bands. In addition, it can be indicated that the formation of these band is related to a possible dynamic recrystallization mechanism.

Effect of Different Ultrasonic Power on the Properties of RHA Steel Welded Joints

Based on the changes of microhardness, tensile strength, and impact resistance caused by the difference of macroscopic morphology and microstructure of welded joints, this paper studied the effect of different ultrasonic power on the properties of welded joints during the welding of homogeneous armor steel. It is experimentally found that the macroscopic morphology of those joints is very different. Compared with conventional welding, ultrasonic welding can increase the weld depth and the width of the heat-affected zone (HAZ) on either side of the weld. However, only the ultrasonic wave at an appropriate power level can increase the weld width. In addition, appropriate ultrasonic power can significantly improve the grain state of the weld. With the increase of ultrasonic power, the grain size in HAZ will decrease. The microhardness of the weld will first increase and then decrease, while the microhardness of the HAZ will increase. This is basically consistent with the changing trend of impact resistance. An ultrasonic wave can also increase the tensile strength of a welded joint up to 802 MPa, 12.4% higher than that in conventional welding. However, a high-power ultrasonic wave will bring down the tensile strength. This study provides guidance for the selection of ultrasonic-assisted regulation power to achieve the different properties of homogeneous armor steel joints.

Mechanical Behavior of Armor Steel Gas Metal Arc Welding Joints Performed by Nickel-Chromium and Low-Alloy Steel Filler Metals

Mechanical Behavior of Armor Steel Gas Metal Arc Welding Joints Performed by Nickel-Chromium and Low-Alloy Steel Filler Metals

Penetration Failure Mechanism of Multi-Diameter Tungsten Fiber Reinforced Zr-Based Bulk Metallic Glasses Matrix Composite Rod

In order to increase the penetration ability of tungsten fiber-reinforced Zr-based bulk metallic glasses matrix composite rod, two multi-diameter tungsten fiber-reinforced Zr-based bulk metallic glasses matrix composites (MD-WF/Zr-MG) are designed. In MD-WF/Zr-MG-I, the diameters of tungsten fiber (WF) increase gradually from the inside to outside, which is the opposite in MD-WF/Zr-MG-II. Penetration experiment of two kinds of MD-WF/Zr-MG rods into rolled homogeneous armor (RHA) steel target from 1470 m/s to 1630 m/s is conducted. The average penetration depth of the MD-WF/Zr-MG-II rod is higher than that of the MD-WF/Zr-MG-I rod. Penetration failure modes of MD-WF/Zr-MG-I and MD-WF/Zr-MG-II rods are bending, backflow of WFs and shear failure respectively. The failure mode of MD-WF/Zr-MG is affected by the bend spaces and the ultimate bending diameters of WFs. If the bend spaces of all WFs are equal or larger than their ultimate bending diameters, the penetration failure mode is the bending and backflow of WFs, oppositely the penetration failure mode is the shear failure. The MD-WF/Zr-MG rod with shear failure exhibits high penetration ability because of low penetration resistance and little residual material in the crater. When designing MD-WF/Zr-MG, bend spaces of a part of WFs should be smaller than their ultimate bending diameter to cause shear failure.

Estimation of ballistic performance of armor steels based on the split Hopkinson shear bar data.

Estimation of ballistic performance of armor steels based on the split Hopkinson shear bar data.

Characterization of Armour Steel Welds Using Austenitic and Ferritic Filler Metals

Characterization of Armour Steel Welds Using Austenitic and Ferritic Filler Metals

WELDING OF HIGH-HARDNESS ARMOR STEEL

Armor steels are difficult to weld due to the high percentage of carbon. The coarse-grained area and the fusion line in the welded joint are sensitive areas due to the high hardness and the possible presence of hydrogen produced during the welding process. Furthermore, multi-purpose armored vehicles made of armored steel are exposed to dynamic loading due to traffic on rough terrain. High hardness in the coarse- grained area of the heat-affected zone and dynamic loading can cause cracks. In the weld metal zone, a crack created during the welding process or due to pores can quickly propagate toward the sensitive fusion line, after which its accelerated growth can occur. Based on the above, achieving a welded joint without porosity or cracks for armor steel is necessary. This paper investigated the welding process of high- hardness armor steel with two regimes. The test aims to achieve an optimal hardness level and a compromise between ballistic requirements and toughness. The test results showed that a high-quality welded joint and an optimal balance between hardness and toughness are achieved with increased heat input.

Effect of welding consumables on shielded metal arc welded ultra high hard armour steel joints

Abstract Materials with high hardness are usually preferred in armour applications and are difficult to weld due to high Carbon Equivalent (C.E). In this investigation, an attempt was made to weld Ultra-high Hard Armour (UHA) steel (having C.E of 0.91) by Shielded Metal Arc Welding (SMAW) process using three electrodes (i) austenitic stainless steel (ASS- E307-16), (ii) super duplex stainless steel (SDSS-E2594-16) (iii) low hydrogen ferritic (LHF-E12018M-low-alloy steel electrode). The mechanical properties (tensile, impact toughness, and microhardness) were evaluated and correlated with microstructural features along with Cr eq /Ni eq ratio of weld metal. The joints fabricated using LHF electrodes showed superior strength of 962 MPa and hardness of 341 HV. The joints made using ASS electrode showed superior impact toughness of 72 J and Notch Strength Ratio (NSR) of 1.32 due to the higher energy absorption capability of the austenitic phase. At the weld interface, joints fabricated using ASS and SDSS electrodes show the unmixed zone (UMZ) and martensitic band (MB) due to sudden change of crystal structure (Face Centred Cubic (FCC) / Body Centred Tetragonal (BCT)). It is also found that the strength property increases (651 MPa to 856 MPa) with an increase in Cr eq /Ni eq ratio (1.87 to 3.2) of weld metal and with a decrease in ductility.