Armour Grade Research Articles

Assessment of dynamic response of armor grade steel plates and FMLs under air-blast loads

This numerical study represents an effort to characterize the dynamic behavior of distinct armor-grade steel plates and fiber metal laminates (FMLs) of the same masses under blast loads. The blast resistance of finite element models of square steel plates and FMLs is evaluated by applying conventional weapon effects program air-blast loading ranging from 1 to 3 kg of trinitrotoluene (TNT) at a fixed stand-off distance (SoD) of 0.1 m. A user-defined subroutine is used to implement a failure criterion to determine realistic failures in the composite. A variation of kinetic energy, radial deflection, and energy absorptions of the steel plates and FMLs are determined to discover their blast mitigation performance. The deformation modes and equivalent plastic strain of both the steel plate and FMLs are also compared. The obtained results show that the armor-grade AISI 4340 steel has up to 50.5% smaller peak deflection than the other armor-grade steels. The use of FML with multi-thin layers of composite laminate and steel sheets instead of equivalent AISI 4340 steel plate significantly reduces the peak deflection up to 23.9% under similar blast loading conditions. The findings of steel plates and FMLs also represent their applicability for making complex protective structures.

Failure assessment of armour grade tensile weld specimen: experimental, computational and analytical approach

Failure assessment of armour grade tensile weld specimen: experimental, computational and analytical approach

Relative influence of microsegregation and structural unit size on the strength-impact toughness properties of an armor grade steel

The present study highlights the comparative interplay between microsegregation of alloying elements and structural unit size on the strength and impact toughness properties of a medium carbon low alloy armor grade steel. Interestingly, despite possessing finer substructural unit (Bain width), the sample austenitized at a lower temperature (800 °C) exhibits inferior impact toughness. This emanates from centerline fissure cracking assisted by severe segregation-induced tensile residual stress at the mid-thickness region. On the other hand, coarse Bain width reduces toughness at the higher temperature (1200 °C). Therefore, austenitization at an intermediate temperature (1000 °C) imparts excellent impact toughness (∼ 45 J at – 40 °C) combined with a commendable yield strength (∼ 1090 MPa). This is attributed to the fine Bain width along with moderate segregation, indicating the significance of austenitization temperature to get an optimized microstructure for achieving a striking balance between strength and impact toughness in a chemically inhomogeneous armor steel structure.

A critical review on the effect of various sustainable reinforcements on armor grade aluminum alloys

To deflect projectiles with kinetic energy by blunting them upon impact, armor with an exceptionally hard surface is required.In order to absorb and disperse the projectile's kinetic energy, the next material needs to be exceedingly tough and have a high work of fracture; hence, it needs to be metallic. To maximize the strength to weight ratio, it must also be composed of a versatile material, such as ceramic. Thus, the application requires a range of qualities, ranging from ceramic to metallic. Aluminum alloys (AAs) are sought-after materials for a variety of engineering and defense uses owing to their excellent low-temperature characteristics, good specific strength, and acceptable corrosion resistance. The main issues with AAs are poor heat tolerance and wear resistance, which makes them unsuitable for military applications owing to their heavy weight, which can exacerbate the deterioration of mechanical components and impair vehicle maneuverability and speed. This paper offers the possibility of modifying the properties of monolithic aluminum materials by adding reinforcement and replacing conventional particulates with low-cost wastes derived from agriculture and industry, which are rich in oxides and other debris, such as fly ash (FA) and rice husk ash (RHA). The result is the development of hybrid aluminum metal matrix composites, or HAMMCs, which combine the best features of both metals with a variety of sustainable inorganic and organic reinforcements that can enhance the mechanical and tribological performances by 40–62 % in comparison to the basic matrix. So, they can be tailored to meet the needs that make their performance superior compared to unreinforced AAs. Through a review of existing literature, this paper will provide an outline of the effect of various kinds of reinforcements on armor-grade aluminum alloys.

Effect of martensite twins on local scale cleavage crack propagation in a medium carbon armor grade steel

This paper proposes the efficacy of martensite nano-twins in a medium carbon armor grade martensitic steel on the cleavage crack resistance at a local scale. Concurrent analyses through electron channeling contrast imaging and electron back scattered diffraction techniques reveal that fine twins of width less than 10 nm are ineffective in deflecting the crack, propagating in the {100} cleavage plane. Coarse twins, on the other hand, resist the crack propagation by deflecting the crack through stepwise crack path propagations, e.g., a combination of matrix-twin {100} cleavage cracking or a combination of matrix {100} and twin-matrix {112} interface cracking. The interfacial cracking along the {112} twin boundaries is attributed to the presence of carbon enriched clusters along the twin boundaries.

Underwater Friction Stir Welded Armour Grade AA5083 Aluminum Alloys: Experimental Ballistic Performance and Corrosion Investigation

Underwater Friction Stir Welded Armour Grade AA5083 Aluminum Alloys: Experimental Ballistic Performance and Corrosion Investigation

Effect of Rotatory Arc Welding Technology on Metallurgical and Mechanical Performance of Armour Grade Steel Joints

Effect of Rotatory Arc Welding Technology on Metallurgical and Mechanical Performance of Armour Grade Steel Joints

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.

Influence of pin profile on microstructure and mechanical properties of armour grade AA5083 friction stir welding butt joints

Influence of pin profile on microstructure and mechanical properties of armour grade AA5083 friction stir welding butt joints

Study on the weldability of AA2519 armor grade aluminium alloy

This paper describes series of studies concerned with welding of Sc-modified AA2519 at the Military University of Technology. The modification of AA2519 alloy contains a higher concentration of scandium and zirconium and it has been developed in The Institute of Non Ferrous Metals, Light Metals Division in Skawina. The examination involves friction stir welding (FSW) and laser beam welding (LBW) of 5 mm thick AA2519-T62 extrusion. FSW process parameters were: 600 rpm tool rotation speed, 100 mm/min welding velocity, 4.8 mm depth plunge, and MX Triflute tool type. The used LBW parameters were as follows: 3.2 kW laser power, 1.1 m/min welding velocity, 0.2 mm laser beam width, 10° laser beam inclination angle, 10 L/min shielding gas (argon) flow with the laser beam focused on the workpiece surface (f=0). In this work selected results have been presented containing some problems and features typical for investigated joints. Butt joints produced by FSW and LBW have been compared in terms of microstructure (grains), microhardness distribution, joint efficiency, localization of failure, etc. The basic features of weld zones have been discussed together with the distributions of microhardness on the joint’s cross-sections. Both welding techniques cause a reduction of microhardness in the weld zone, but the drop from the base material’s value (135-140 HV0.1) is far higher in the case of LBW (85-90 HV0.1) than FSW (120 HV0.1). The established values of joint efficiency were 80% (376 MPa) and 66% (314 MPa) for FSW and LBW, respectively. The FSW joints tend to fail in the thermo-mechanically affected zone and LBW in the fusion zone.

A Critical Assessment on Rotary Friction Welded High Strength Armor Grade Aluminum Alloy Joints

A Critical Assessment on Rotary Friction Welded High Strength Armor Grade Aluminum Alloy Joints

Influence of Welding Consumables on Ballistic Performance of Gas Metal Arc Welded Ultra-high Hard Armor Steel Joints

Steels with high strength and high hardness are considered to be the essential criteria for weight reduction in armored fighting vehicles (AFVs). Ultrahigh hard armor (UHA) steels are higher hardness (>500 HV) and higher strength (>1,500 MPa) than the currently used rolled homogenous armor (RHA) steels. The occurrence of both a tempered region in the grain-refined heat-affected zone (HAZ) and hydrogen-induced cracking (HIC) has become the limiting factor in the life extension of weld in high-strength and high-hardness armor grade steels. Hence, an attempt was made to weld UHA steel by gas metal arc welding (GMAW) process using different three filler metals (1) austenitic stainless steel (ASS), (2) duplex stainless steel (DSS), and (3) low-hydrogen ferritic. The ballistic performance of the joints was evaluated based on the area density and depth of penetration. The mechanical properties (transverse tensile, hardness, and impact toughness) and microstructural features of welded joints are correlated with the ballistic performance. All the joints stopped the 7.62 × 51 ball projectile at the weld metal region. However, through-hole (perforation) was observed when tested against the 7.62 × 54 armor piercing projectile. The joints fabricated using ASS filler wire showed superior ballistic resistance, a lesser degree of HAZ softening, and better impact toughness properties due to the higher energy absorption capability of the austenitic phase.

Optimizing the underwater friction stir welding parameters to enhance the joint strength of armour grade aluminium alloy AA5083 butt joints

Solid states prove to justify the existence of joints. The Friction Stir Welding process (FSW) is auspicious in the realm of aluminium composites. The challenge exists in the usage of an FSW for joining aluminium alloys. In this area, a lot of progress is made in the recent years. The underwater FSW procedure (UWFSW) is considered to be one of the most important professional methodologies. It is a totally innovative and futuristic mechanization. Here, the non-expendable electrodes work on the substrate underwater without exhalations. It also requires minimal power, which contributes to enhanced mechanical characteristics. There are many principal advantages such as minimal contortion, non-existence of thaws connected to the imperfections, and the enhanced joining ability. The implement designs and the substance contribute to the enhancement of significant characteristics, including the welding and rotational speeds and equidistant forces. In this research, armour grade aluminum alloy AA5083 with dimensions of 150×100×6.35 mm were friction stir welded under water, in order to improve the joint strength. The results indicated that the tensile strength improved up to 191.3 MPa. The superior granule arrangements, elevated dislocation thickness, and firm elucidation intensification significantly improved the hardness in the minimum hardness location (MHL). This resulted in further improvement of the UWFSW’s tensile strength. The high dislocation density and the elongation were found to probably decrease between NZ and TMAZ.

Tensile properties of shielded metal arc welded ultrahigh hard armour steel joints

The present generation Armoured Tracked Vehicles (ATVs) are constructed using Rolled homogenized armour (RHA) grade steels closely confirming with AISI 4340 specifications. However, in future Armoured Tracked Vehicles (ATVs), the overall weight of ATVs has to be reduced enormously and hence, the designers have prescribed to employ Ultra High Hard Armour (UHA) steels for the construction. Welding is considered to be one of the important fabrication methods in ATVs construction. However, welding of UHA steels is highly challenging due to higher hardness and higher carbon content. Shielded Metal Arc Welding (SMAW) is among the most widely employed welding process in the construction of ATVs since it is more versatile and cost-effective. Armour grade steels are welded conventionally using Austenitic Stainless Steel (ASS) consumables to eliminate the serious problems of hydrogen induced cracking. Hence, in this investigation, an attempt has been made to study the influence of ASS welding consumables on tensile properties and hardness of UHA steel joints made by SMAW process. UHA steel plates having 15 mm thickness were welded by SMAW process using five different ASS consumables (having different Creq/Nieq ratio). Tensile properties (unnotched and notched) of the welded joints were evaluated. From this investigation, it was observed that the joint welded using ASS consumable (having higher Creq/Nieq ratio) exhibited superior tensile properties as result of the evolution of ferrite phase with vermicular and globular morphology in the austenite matrix at weld metal region.

Comparative study of tungsten inert gas and friction stir welding of aluminium alloy aa5083 (armour grade) aluminium alloy joints

Aluminium-magnesium Alloy AA5083 is used widely as a building and tooling material in aerospace, automobile, and marine industries. This Work shows the comparison of AA5083 (armor grade) – 6mm thickness plate weldments mechanical properties on TIG Welding and FSW processes. Welding of metals is based upon the input parameters as it has an important role of finalizing the weldment and the tool used for welding is H13 Tool Steel as the tool has less deformation due to high chromium content. Generally, the welding processes are aimed at achieving a welding joint with superior mechanical properties with minimum deformation. The tensile strength of the weldments is found by testing in the Ultimate Tensile Strength (UTM) machine. The hardness test is performed by Vickers Hardness tester to characterize the welded area. Macro Vickers Hardness is performed in the welded area of the workpiece to finalize mechanical properties in different heat-affected zones of FSW welded workpiece to analyze and find the efficient input parameter of FSW. The efficient input parameter for TIG welding is identified and a comparative study is made and the result proves that FSW welding is a better welding technique.

Prediction of Optimum Welding parameters for Friction stir welding of Aluminium Alloy AA5083 Using Response Surface Method

Friction Stir Welding (FSW) is carried out on armour grade aluminium alloy AA 5083 with dimensions of 100X50X6.35 mm. The process parameters like tool profile play a significant role to enhance the welding. Many processing conditions influence the microstructure progression and mechanical behaviour of the produced joints. The main parameters involved in the welding process is discussed under this work. Various parameters such as welding speed, tilt angle, spindle speed and various tool profile are used. Analysing the mechanical behaviours of joints welded like tensile strength and hardness is investigated. In this work tool profiles are designed according to the specific dimensions and the tool material chosen is H13. The tool profiles which are chosen are Cylindrical, Tapered and Hexagonal. So, for this profile, the welds are made accordingly. The Study involves the process which is going to take place are Tensile strength, Impact strength, Hardness, and Microstructure. After the finished AA5083 welded aluminium alloy, it is cut in using the EDM machine according to the ASTM standard. The experiment is designed to determine the major factors affecting the hardness and tensile strength of the joints. For the speed of the tool, tool profile and forward movement of the tool tensile strength and hardness are studied. The contribution of each factor is determined from RSM; For the nine samples, the different factors which are used in this process are compared and investigated. These sample values are compared and analysed by using ANOVA. Based on the values obtained from the test the graph is plotted and based upon the speed of the tool from 1000 to 1500 rpm and forward motion of the tool from 18 to 24 mm/min values is investigated.

Optimization of FSW Parameters to Improve the Mechanical and Metallurgical Properties of Aluminium Alloy AA 5083 Joints

Friction Stir Welding (FSW) is carried out on armour grade AA5083 aluminium alloy having the dimensions of 100X75X6.35 mm. The FSW process and tool parameters play a major role in deciding the joint strength. Many processing conditions and material properties affect the microstructure evolution and mechanical behaviours of the produced joints. Various parameters such as welding speed, tilt angle, spindle speed and various tool profile are used. Analyzing the mechanical behaviours of joints welded like tensile strength and hardness were investigated. The tool rotation and welding direction same side are similar is called Advancing side (AS) and opposite on the other known as retreating side (RS). The input process parameters which influence the strength of the joints. Main consideration is to select the best parameter to produce the defect free joints. Experiment is designed to determine the major factors affecting the hardness and tensile strength of the joints. Effect of rotational speed, welding speed and tilt angle on tensile strength and hardness are studied. The contribution of each factor is determined from ANOVA analysis “Tensile strength and hardness increased with increasing the rotational speed 1000 rpm to 1400 rpm, traverse speed from 30 mm/min to 40mm/min”. This investigation mainly deals with Taguchi and ANOVA were performed to improve the effective characteristics of welding inputs.

Influence of SD effect on Johnson–Cook hardening constitutive material model: Numerical and experimental investigation for armor steel

The influence of strength–differential (SD) effect has been investigated on Johnson–Cook (JC) material model parameters for armor grade RHA steel. Two set of JC model parameters has been developed with the help of compressive and tensile flow curve. Further, a finite element analysis (FEA) of static (at 10−3 s−1) and dynamic indentation (at 104 s−1) has been performed to validate the effect of tensile and compressive JC material model parameters. In addition, static and dynamic indentation FEA results has been compared with the expanding cavity model (ECM) and experimental Split–Hopkinson pressure bar results, respectively. FEA simulation with compressive data has been shown good agreement with experimental results and analytical models. %SD effect is increased with an increase in plastic strain in armor grade RHA steel.

Experimental and Numerical Investigation of Quasi-Static (10−3 s−1) Fracture Behavior of Armor Steel

In this investigation, a numerical approach has been used for predicting the quasi-static strain rate (10−3 s−1) hardening and damage behavior for armor grade steel Armox 500T at ambient temperature. The power-law has been used to provide the hardening yield to ultimate tensile strength. Further, to predict the damage behavior, ductile damage model parameters, which include fracture strain and stress triaxiality, have been established. The damage has been created in the form of cup and cone that follows the necking behavior. The FEA model from the current study is capable of predicting the flow stress versus plastic strain curve for the strain rate ranging from 10−4 to 10−1 s−1. Results from FE simulation have been validated by experimental results at the strain rate of 10−3 s−1. The results revealed that the simulation values have good agreement with the experimental data. At the end, fractographic analysis of the tensile samples is also presented for better understanding of the damage behavior of armor steel.

Ballistic impact behaviour of newly developed armour grade steel: An experimental and numerical study

High strength steel plates are majorly utilized for civil and military vehicles for ballistic protection against various threat levels. In this work, an experimental and numerical study has been conducted on a newly developed armour steel grade. Four different ductile fracture criteria have been used in the numerical simulations, namely Modified Johnson-Cook (MJC), Cockcroft-Latham (CL), Constant failure strain (CFS) and Maximum Shear (MS) stress failure criteria. Suitable experiments were conducted for material model parameter estimation and a simulation study was conducted in LS-DYNA to evaluate its performance in a plate impact simulation. The results were correlated with an actual Impact test done with a plate of dimension 1000 × 1000 × 6 mm with 7.62 × 51 mm NATO ball ammunition for NIJ (National Institute of Justice) Level 3 protection. Modified Johnson-Cook, Cockcroft-Latham and Constant strain failure criteria are in good agreement with experimental results. Maximum Shear stress failure criteria failed to predict the experimental results.