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Ballistic performance of high-nitrogen steel (HNS) plates and RHA steel plates were evaluated against 7.62 mm ball and 12.7 mm armour piercing (AP) projectiles The impact velocities of 7.62 mm ball and 12.7 mm armour-piercing projectiles were 850 ± 10 m/s and 840 ± 10 m/s respectively. Critical thickness at which projectile is stopped was found from ballistic tests on different thickness targets and it was used for comparing the ballistic performance. HNS plates showed improved impact resistance (in terms of minimum areal density at which projectile is stopped) than that of RHA steel plates against both 7.62 ball and 12.7 mm armour piercing projectiles. Improved impact resistance of HNS plates could be correlated with its superior high strain rate flow stress values with respect to RHA steel. Microstructural evaluation revealed that adiabatic shear band induced plugging and ductile-hole growth are the major failure modes in both targets against 7.62 ball and 12.7 AP projectiles respectively.

The objective of the present study is to develop cost effective thermoplastic hybrid laminate using Dyneema® HB50 and Tensylon®HSBD 30A through structural hybridization method. Laminates having 20 mm thickness were fabricated and subjected to 7.62 × 39 mm mild steel core projectile with an impact velocity of 730 ± 10 ms−1. Parameters such as energy absorption, back face deformation and rate of back face deformation were measured as a function of hybridization ratio. It was observed that hybrid laminate with 50:50 ratio (w/w) of Tensylon® and Dyneema® with Tensylon® as front face showed 200% more energy absorption when compared to 100% Tensylon® laminate and showed equal energy absorption as that of expensive 100% Dyneema® laminate. Moreover, hybrid laminate with TD50:50 ratio showed 40% lower in terms of final back face deformation than Dyneema® laminate. Rate of back face deformation was also found to be slow for hybrid laminate as compared to Dyneema® laminate. Dynamic mechanical analysis showed that, Tensylon® laminate has got higher stiffness and lower damping factor than Dyneema® and hybrid laminates. The interface between Tensylon® and Dyneema® layers was found to be separating during the penetration process due to the poor interfacial bonding. Failure behaviour of laminates for different hybridization ratios were studied by sectioning the impacted laminates. It was observed that, the Tensylon® laminate has undergone shear cutting of fibers as major failure mode whereas the hybrid laminate showed shear cutting followed by tensile stretching, fiber pull out and delamination. These inputs are highly useful for body armour applications to design cost effective armour with enhanced performance.

This work presents the influence of ballistic testing variables on residual velocity of projectile and absorbed energy of aluminum 1100-H12 using design of experiments (DOE) and artificial neural n...

Hybrid composites are versatile materials for armour and aerospace applications as they can confer the advantages of both the fibres to the system. Carbon/UHMWPE hybrid composites were prepared by varying volume % of carbon and UHMWPE laminates using the hot press method. The hybrid composites were each subjected to ballistic impact from a 7.62 × 39 mm mild steel (MS) projectile at an impact velocity of 730 ± 10 m.s− 1. The effect of hybridization ratio on the energy absorption of hybrid composites was investigated. The specific energy density (SED) dissipated by the hybrid composites was determined and it is found to increase with increasing volume % of UHMWPE. The real time dynamic deformation of the hybrid composites under ballistic impact was recorded using a high speed video camera. The back face deformation and bulge growth rate of hybrid composites were determined and the results are presented. Post impact analysis of the composites was carried out to examine the various failure modes.

This paper presents the commercial production of a high strength low alloy steel with 8 different thicknesses through continuous casting route. All the plates exhibit tempered martensite structure ...

In this work, a new attempt has been made using machine learning algorithms for assessing failure mode of austempered ductile iron perforated plates. This aims at providing some insights into these...

Drilling trials were conducted on E glass woven composites and machine learning models were employed for correlating drilling variables namely point angle, feed rate and spindle speed with response...

This study presents a methodology to find the optimal sequence and thicknesses of individual material layers in a multilayer armour module. The methodology is demonstrated with application to three different metal alloys: Armox-500T, Ti-6Al-4V and Al-2024. Numerical simulations are performed first to study the ballistic impact behaviour of these three materials using AUTODYN-3D code. The results of numerical simulations are compared with experimental results for validating the numerical models. Thereafter, a three-layer armour module consisting of these three materials is optimized to defeat 7.62 armour piercing projectile with minimum weight. The optimization process involves carrying a set of numerical simulations based on the design of experiment approach to generate a response surface for the ballistic performance of a composite module. A new ballistic performance parameter is introduced to measure the ballistic response of the module by combining depth of penetration and residual velocity of the projectile to bring uniformity between two cases of partial and complete penetration. The proposed parameter provides more information on ballistic performance. The response surface for ballistic performance parameter is generated in terms of thicknesses for six possible combinations of three material layers. The adequacy of the proposed optimization scheme is confirmed with ballistic experiments. The sequence Armox-500T/Ti-6Al-4V/Al-2024 with thicknesses 5.5, 8.5 and 13 mm, respectively, is found to be the best against 7.62 mm armour piercing projectile. Furthermore, the performance of each individual material is compared with an optimized three-layer armour module. The composite module is found to be weight efficient over Armox-500T, Al-2024 and provides better thickness efficiency over Al-2024. The weight efficiency and thickness efficiency of Ti-6Al-4V are found to be comparable to the composite module. This study emphasizes the necessity of developing new procedures to provide reliable estimates of design parameters for a multilayer armour module.

The objective of this research is to investigate the dynamic flow behavior of Ti-5553 alloy at elevated temperatures using Crystal plasticity and Johnson-Cook (J-C) models. Compression tests were carried out at different temperatures of 25 °C, 200 °C, 400 °C and 600 °C at various strain rates of 0.01–2000/s. A physically-based Modified Crystal plasticity model was then adopted to describe the flow behavior in the Work hardening (WH)-Dynamic recovery (DRV) regime in conjunction with Arrhenius equation. The model well established the flow behavior of the titanium alloy, mainly the strain hardening and thermal softening effects. Microstructural study has also been undertaken. The mechanisms of dynamic recrystallization and adiabatic shear bands are discussed. Numerical simulations were carried out using the ABAQUS/Explicit code. The developed crystal plasticity model was implemented in ABAQUS using user sub-routine UMAT.

To investigate the dynamic mechanical behavior of Ti-10-2-3 alloy, the material was subjected to quasi static and dynamic compression testing. The results confirm that material exhibits strain rate sensitivity at low and high strain rates. The deformation mechanisms are elucidated by thermal activation theory. Voyiadjis-Abed (V-A) model is proposed to establish the thermo mechanical response of Ti-10-2-3 alloy. The developed model is compared with Johnson-Cook (J-C) model at different strain rates and temperatures. The V-A model well established the quasi-static and dynamic behavior of the Ti-10-2-3 alloy, mainly the effects of strain hardening and thermal softening. This model is embedded in ABAQUS/Explicit code in the form of a VUMAT user-subroutine to perform ballistic impact simulations. It is found that the predicted residual velocities are well matching with the experimental results. Adiabatic shear bands were observed in specimens deformed at higher strain rates. The tensile specimen is broken in a manner of ductile fracture presenting typical dimple structure, while the compressive specimen fails in a manner of localized shearing failure.

In the present paper, the high velocity impact of 9 mm soft lead projectile on 10 mm and 30 mm thick E-glass/epoxy composites was studied using a 450 kV Flash X-ray radiography (FXR) system. The basic parameters of FXR imaging, such as effect of ratio of target to film (TF) and source to target (ST) distances and X-ray penetration thickness of the composite material were optimized based on clarity and the actual dimensions of the objects. The optimized parameters were used in the FXR imaging of the ballistic event of 9 mm soft projectile on E-glass/epoxy composite. The real time deformation patterns of both the projectile and composite target during the ballistic impact were captured and studied at different time intervals. The notable failure modes of the 10 mm thick target with time include fibre breakage, bulging on the back side, delamination, recovery of the bulging, reverse bulging and its recovery. However, with increase in thickness of the target to 30 mm the only failure mechanism observed is the breaking of fibres. The ballistic impact event was also numerically simulated using commercially available LS-DYNA software. The numerically simulated deformation patterns of the projectile and target at different time intervals are closely matching with the corresponding radiographic images. Keywords: Flash X-ray radiography, E-Glass/epoxy composite, Ballistic impact, Numerical simulation

The feasibility of significant weight reduction in conjunction with the superior strength-ductility combination makes Fe-Mn-Al-C-based steels the candidate material for automotive and structural applications. The alloy chemistry and processing conditions influence the microstructure in low-density steels (LDS); however, their role in deformation behaviour is not fully understood. In the present study, three different austenitic LDS grades viz. Fe-28Mn-9Al-0.9C, Fe-28Mn-9Al-5Ni-0.9C and Fe-15Mn-9Al-5Ni-0.9C alloys in hot-rolled conditions were used for evaluating the role of secondary phases, especially B2 ordered Fe(Ni)Al phase on deformation characteristics. Ni-free LDS microstructure consisted of the γ-matrix with fine κ-carbides, whereas Ni containing low Mn alloy possessed coarser κ-carbides along with B2 in both bamboo-like stringer and polygonal particle morphology in the γ-matrix. The B2 containing alloy exhibited higher strength with reduced tensile ductility than the B2-free alloy. Hardness of the γ-matrix and B2 phase were similar with B2 grains exhibiting distinct pop-in events in the nanoindentation curves indicating incipient plasticity. The γ-matrix and B2 co-deform near yield, and a favourable orientation relationship (OR) between the γ-matrix and B2 facilitated easy slip transfer, while the non-favourable OR controlled ductility by strain accumulation and B2-cracking. The differences in the strain hardening behaviour of B2-free and B2 containing alloys were elucidated based on the changes in dislocation substructure evolution examined by an automated crystal orientation mapping in electron microscopy.

Hot-rolled high-nitrogen steel (HNS) plates were evaluated against AK-47 mild steel core (7.62 mm × 39 mm, deformable) and 14.5 mm armour piercing (AP) (14.5 mm × 114 mm, hard steel core) projectiles. The ballistic results of HNS plates were compared with conventionally used Rolled Homogeneous Armour (RHA) steel plates. The ballistic tests on HNS and RHA steel plates with different thicknesses were conducted against AK-47 mild steel core and 14.5 mm AP projectiles at velocities of 740 ± 10 m/s and 1000 ± 10 m/s respectively, in order to find out the minimum thickness required to stop the projectile without perforation. In comparison to RHA steel, HNS exhibited higher ballistic performance (in terms of minimum areal density required) against both AK-47 mild steel core and 14.5 mm armour piercing projectiles. The ballistic results against 14.5 mm AP was studied using an analytical model reported in literature. Detailed post ballistic (microstructural and hardness measurements) investigations were carried out to understand the ballistic performance of the two steels. Further, an attempt has been made to correlate the initial microstructure and mechanical properties with the failure mechanisms activated during ballistic impact and the resulting ballistic performance.

A comparative study on ballistic performance of hot pressed boron carbide (HPBC) and reaction bonded boron carbide (RBBC) tiles were performed using depth of penetration (DOP) configuration against...

In the present study varying thickness of (5-25mm) E-glass composite laminates have been prepared through hot compression moulding method using different matrix systems such as phenolic and epoxy with E-glass fiber as a common reinforcement. The laminates were initially evaluated for their mechanical and mode-I inter laminar fracture energy as per ASTM test methods. It is observed that the laminate having epoxy matrix has shown higher mechanical and fracture energy than the laminate made using phenolic matrix. This is due to the strong adhesion bond between the epoxy matrix and glass fiber reinforcement. Further, the laminates were subjected to ballistic impact tests against 7.62X 39 mild steel projectiles. It is observed that the laminate having lower fracture energy (E-glass/phenolic) has shown better energy absorption under ballistic impact. Failure analysis on post impacted laminates have been studied using C-scan analysis and observed that E-glass/epoxy composite laminate has shown limited damage area, whereas E-glass/phenolic composite laminate has shown more damage area. This study reveals that the laminate having lower fracture energy for delamination is more suitable for higher energy absorption due to dissipation of energy in lateral directions under ballistic impact conditions.

Fibre-reinforced composite materials have remarkable potential for use in automobile, aerospace and defence applications due to their high specific properties and stiffness. E-glass fiber reinforced composite laminates are found to be more promising for various defence applications due to their low cost, easy availability, flexibility in design and processing. In the present study, E-glass/epoxy composite laminates were subjected to low velocity impact using 16 mm hemispherical impactor with the impact energy range of 50-150 J. Effect of laminate thickness on impact parameters like peak force, maximum displacement and damage area was experimentally evaluated. It was found that peak force is increased with increase in impact energy up to complete perforation and then became constant. Peak force is found to be increased linearly with the increase in thickness at all impact energies. Maximum displacement has decreased 50% as the thickness of the laminate is doubled. Interaction time/contact duration also decreased due to increased resistance with thickness. Visual inspection of impacted laminates indicates two types of damage regions namely fibre breakage area and delamination area. However, the extent of damage regions and their ratio are found to be thickness dependent. Dominant failure mode gradually changes from fibre breakage to delamination as the thickness is increased.

Carbide free nano bainitic steels have recently become a promising material for several applications such as rails, armour etc. because of their impressive combination of mechanical properties. Very high strengths up to 2500 MPa have been achieved because of the very fine nano-scale microstructure obtained through transformations at low austempering temperatures. However, the low ductility and impact toughness are the limiting factors which prevent their use in several applications. It is well known that alloying elements such as Nb and V are added in very small quantity in order to improve strength and ductility of low and medium carbon steels through Nb, V (C, N) precipitates. Influence of these microalloying elements on the mechanical properties of nano bainitic steel is not well understood. In the present study, mechanical properties of two high carbon nano bainitic steels with 0.037 wt% Nb and without Nb addition have been studied. Nb addition results in a substantial increase in ductility (total % elongation) from 16 % to 28 %. Effect of Nb addition on transformation kinetics, microstructure and mechanical properties is also discussed.

The objective of the study is to understand the dynamic flow behavior of Ti–22Al–25Nb alloy at high temperatures using a modified Zerilli–Armstrong (Z-A) model. To investigate the dynamic mechanical behavior of titanium alloy, the material was subjected to quasi static and dynamic compression testing. It is found out that the modified Z-A models possess better predictability in evaluating the flow behavior of the Ti–22Al–25Nb alloy at elevated strain rates and temperatures. The model well established the quasi-static and dynamic behavior of the titanium alloy, mainly the effects of strain hardening and thermal softening. The regimes of high strain rate deformation behavior represented by dynamic recrystallization (DRX), lamellar globularization and the instability flow have been discussed. Using transmission electron microscopy (TEM) studies, it is found that the dislocation density is directly associated with strain rate.

The purpose of this study is to describe the dynamic behavior of near alpha titanium alloy at elevated temperatures using Crystal plasticity and other models. Three constitutive models: Johnson-Cook (J-C), Zerilli–Armstrong (Z-A), Cowper-Symonds (C–S) and J-C fracture models are established. Experimental results observed that material displayed strain rate sensitivity at various strain rates. The generated model constants have been incorporated into finite element code. Finite Element simulations of tensile tests under different strain rates have been performed using Autodyn software. A crystal plasticity model is established and shows that it can predict the stress strain response under dynamic loading conditions. The developed crystal plasticity model was implemented in the ABAQUS code to simulate high strain rate compression and showed good agreement. Subsequently, a Charpy impact test on specimen has also been simulated. The fracture surfaces of specimens tested under quasi static state at various temperatures were studied under scanning electron microscopy (SEM).

Static indentation and uniaxial compression tests have been conducted on Armox500T steel and its weldments to predict the constraint factor (CF), i.e., ratio of Meyer’s hardness to uniaxial flow stress. Series of dynamic indentation experiments were carried out at impact velocities ranging from 5 to 300 m/s to estimate dynamic hardness as a function of average strain. Subsequently, dynamic indentation (DI) test data and CF determined under static indentation conditions have been used to study the high strain rate plastic flow behavior of Armox500T weldments in comparison with the base metal. It was observed that flow stress for Armox500T and its weldments under dynamic loading conditions (104 s−1) are significantly higher than flow stress measured under static loading conditions (10−3 s−1). The plastic flow behavior computed from DI is in good agreement with the data evaluated through conventional split Hopkinson pressure bar technique. Further, the study of the microstructure of base metal and weldments by optical microscopy and SEM revealed a considerable variation in the microstructure.

Study of tribological characteristics of multi-pass shielding metal arc-welded (SMAW) Armox 500T steel joints in comparison with its counterpart base metal was carried out. Series of dry sliding wear tests were carried out as a function of applied loads ranging from 30 to 120 N and sliding distances from 1000 to 6000 m at a constant sliding velocity using pin-on-disk tribometer. It was observed that specific wear rate and lost volume in SMAW joints significantly high compared to Armox 500T base metal in the range of loads and sliding distances considered in the present study. The scanning electron micrographs indicated that wear of Armox 500T base metal occurred due to micro-grooving and adhesion, on the other hand, micro-delamination was observed in SMAW joints. Microstructural investigations revealed that base metal exhibits superior tribological properties as compared to SMAW joints due to the formation of martensite lath in acicular form with coarse and fine precipitates.

In this investigation, comparative study of tensile and impact properties of multi-pass SMAW Armox 500T steel joints fabricated by austenitic stainless steel (ASS) and low hydrogen ferritic steel (LHF) consumables vis-a-vis base metal was carried out. The tensile tests were conducted on computer controlled Walter + Bai Ag UTM at a nominal strain rate of 10−3 s−1. Subsequently, charpy impact tests were carried out on an instrumented Zwick-Roell test setup to obtain load vs. displacement and maximum energy absorbed vs. displacement of the specimen. It was observed that, the joint efficiency of weldment processed by LHF consumable was 41.7% and weldment processed by ASS was 30.6% of its base metal indicating the influence of electrode consumable on tensile properties of the joints. On the contrary, impact toughness of weldment processed by ASS was 20% more and weldment processed by LHF was 12% less than that of base metal. Microstructural studies also revealed that, ASS can be considered as a candidate welding consumable for good strain hardening and toughness of the welding joint in impact applications. However, LHF steel consumable is recommended for welding joints that requires higher joint efficiency under tensile loading conditions. Keywords: Armox500T, Multi-pass SMA welding, ASS and LHF welding consumables, Mechanical properties, Microstructural characterization

The effect of backing material, projectile velocity and tile thickness on the ballistic efficiency of ceramic materials was studied against 7.62 mm AP projectile in depth of penetration (DOP) test configuration. An analysis on variation in differential efficiency factor (DEF) with respect to backing material was carried out. The factor responsible for variation in DEF was eliminated using a normalization method. A new definition (NDEF/ NBE) is proposed for calculation of ballistic efficiency. Using the new definition a comparison of ballistic efficiency of hot pressed boron carbide, alumina and zirconia toughened alumina were done for different projectile velocities and tile thickness. The DEF was found to increase with increase in projectile velocity, but NDEF and NBE were found to decrease with increase in projectile velocities. Even though the DEF, NDEF and NBE have produced different ballistic efficiencies they all have produced similar trends with respect to tile thickness.

The ballistic performance of monolithic and multi-layered in contact and spaced mild steel target plates has been studied at normal and oblique impact against 7.62 AP projectiles with an objective to ascertain the effect of angle of obliquity. Numerical simulations have been performed on ABAQUS/Explicit finite element code and typical results obtained have been validated by earlier experimental results, Gupta and Madhu [1] , [2] . The Johnson–Cook elasto-viscoplastic material model calibrated by the authors for mild steel was employed in the numerical simulations. Close correlation of typical experimental and numerical results validated the numerical procedure and the calibrated model. Ballistic limits of monolithic mild steel targets of thicknesses 4.7, 6, 10, 12 and 16 mm each impacted at 0, 30 and 45ᵒ obliquity were numerically computed. The ballistic limits of in contact layered and spaced targets of equivalent thickness 10 mm (3.33 + 3.33 + 3.33 mm) were also computed at 0, 30 and 45° obliquity. For 60° angle of obliquity, the monolithic target experienced project ricochet, in contact layered target, projectile embedment, and the spaced target, projectile perforation. At low angles of obliquity, the difference between the ballistic performance of monolithic, layered in contact and spaced targets was not significant. As the angle of obliquity increased, each studied configuration was found to have distinct ballistic performance. Simulations were also done for three layered target of 4.7 and 6 mm thick plate and spacing was varied to study its effect on their ballistic resistance. The variation of spacing at normal impact was found to have influence as long as the spacing was smaller than the projectile length.

A comprehensive study has been performed for understanding the constitutive behavior of titanium alloy IMI 834 under different strain rates, stress triaxialities and temperatures. Results confirmed an improvement in its strength with increase in strain rate and stress triaxiality. Experimental results obtained from the specimens of materials were employed to calibrate the material parameters of Johnson–Cook (J-C) strength and fracture model. The microstructure study has been undertaken to discuss the shear band and grain growth mechanisms. Three constitutive models: Johnson-Cook (J-C), Zerilli–Armstrong (Z-A) and Cowper-Symonds (C-S) models are established to determine the flow stress using dynamic compression data. The ballistic tests were performed in which 8 mm thick target plates were impacted by 7.62 AP projectiles with a velocity of 830 m/s. The ballistic test results were replicated through numerical simulations carried out using ABAQUS finite element code. It is observed that the residual velocities generated by simulations were in good agreement with the experimental results.

The dynamic compression tests were performed at various strain rates (0.01, 1700, 2700 and 3500/s) and temperatures (25, 200, 400 and 600 °C) for a biomedical Ti–13Nb-13Zr alloy. Based on experimental data, constitutive models were established using the Modified Johnson-Cook (J-C) model, Modified Khan–Huang–Liang (KHL) model and Artificial neural network (ANN) model, respectively. The new modified J-C model considers the coupled effects of strain hardening, strain rate hardening and thermal softening. In this work, a radial basis function artificial neural network (RBF-ANN) model was also developed to predict the high strain rate flow curves of Ti–13Nb-13Zr alloy. The results demonstrate that the flow behavior of Ti–13Nb-13Zr alloy is considerably influenced by the strain rate and temperature. The modified KHL model and ANN significantly enhance the predictability. The deformation behavior represented by dynamic recrystalization (DRX) and the instability flow has been discussed with reference to microstructural evolution during high strain rate compression. The validation of the developed constitutive model is embedded in the finite element analysis (FEA) to perform numerical simulations with ABAQUS/Standard to obtain the charpy impact energy.

The objective of the study is to perform experiments on FeCoNiCr high entropy alloy under different strain rates ranging from 0.01 to 3500/s and also at temperatures of 25, 200, 400 and 600 °C. Considering the effects of work hardening and thermal softening at high strain rates, the flow behavior is characterized by employing the modified Johnson-Cook (J-C) and Zerilli–Armstrong (Z-A) models. The triaxiality data showed the decrease in effective plastic strain at failure as triaxiality increases for all strain rates. Fracture constants have been evaluated.

Polymer composite laminates has got crucial role to play in reduction of armour weight due to their high specific energy absorption capabilities. The role of resin in composite armour is paramount in impact energy absorption. In the present study, ballistic performances of E-glass/phenolic and E-glass/epoxy laminates were compared against small arms and large calibre ammunition. The laminates with varying thickness were fabricated through hot pressing method and were evaluated against small and large calibre projectiles. E-glass/phenolic laminate showed 30 % more energy absorption than Eglass/ epoxy laminate. Failure behaviour of laminates were studied and characterized based on delamination and fiber stretching.

Due to increasing requirement for light weight armour solutions the use of ceramic materials in armour applications has enormously increased. However, the multi hit performance of ceramic materials is still a problem due to their inherent brittleness. This problem is generally addressed by changing the design aspect like using ceramic segments instead of tiles. Even though ceramic segments are in use for armour applications for a long time the ballistic performance of these cylindrical segments have not been measured using simple ballistic testing technique like the Depth of Penetration (DOP) test similar to that of tiles. In this study the DOP test method is utilized for ballistic evaluation of cylindrical alumina segments. The post ballistic damage area was found to be lesser in case of cylindrical alumina segments than alumina tiles, but the ballistic performance of cylindrical segments was found to be inferior to that of tiles.

Various materials are being subjected to high strain rate loading conditions when in use such as penetrator or armour. Armco Fe, Pure Mg, Ultra high strength martensitic steels are some of the widely used material. However, limited study exists on understanding effect of crystal structure, strain rate and temperature dependent deformation behavior of these materials. In the current study, we explore the strain rate and crystal structure dependent change in deformation mechanism of these materials. Pure Mg and Fe were subjected to compression at a strain rate of 0.01- 4000/s. The effect of strain rate, initial microstructure and texture on twin induced grain re-orientation, slip and twin-slip interaction is studied. An approach to derive a physics based model to depict microstructure based phenomenon is discussed. The effect of strain rate on flow behaviour and fracture in Ultra High Strength martensitic steels along with adiabatic shear band formation is also explored.

Ballistic performance of an armour steel against a scaled-down tungsten heavy alloy projectile having an L/D ratio of 14 was investigated. The depth of penetration in the steel target plate was measured for different impact velocities (900–1400 m/s) using scaled-down experimental tests. Penetration velocities were calculated from the measured depth of penetration data using a steady-state relationship, and it is found to have a linear relationship with impact velocity. Using the linear relationship, penetration velocity at a higher impact velocity (1600 m/s) was calculated and was found to be in agreement with the full-scale experimental results for the projectiles with L/D = 16. The relative strength of the target and penetrator (Rt–Yp) was calculated and found to increase initially and then decrease to zero as the impact velocity approaches the hydrodynamic range. Maximum Rt–Yp was observed at a velocity of around 1000 m/s which is close to the critical velocity for commencement of eroding steady-state penetration. Microstructural observations on impacted target and projectiles have shown that both the target as well as penetrator materials undergo erosion during the penetration.

Hot compression tests of Ti-10-2-3 alloy were carried out in the temperature range of 900–1050 °C, at strain rates of 0.001–1 s−1 on a Gleeble thermo mechanical-simulator. The experimental results demonstrate that the flow stress of the titanium alloy is significantly influenced by temperature, strain and strain rate. A physically-based constitutive model was established, based on the dislocation density theory and dynamic recrystallization kinetics. The comparison between the experimental and predicted flow stresses shows that the established model has high accuracy. The statistical study confirmed the predicting capability of the model. The presented constitutive model, as well as the dynamic recrystallization (DRX) kinetics, was incorporated into ABAQUS to provide an effective means to study hot deformation. Results confirm that the constitutive model considering dynamic recovery (DRV) and DRX provides high accuracy. DRX results of the Finite Element Method (FEM) are in good agreement with the experimental results.

Sandwich panels with cellular cores are being widely used as blast mitigation materials, due to their light weight and good energy absorption properties. In the present study, the behaviour of sandwich panels against different shock loadings is evaluated using piston driven shock tube. The sandwich panels are fabricated using aluminium(Al) foam core and E-glass/epoxy composite face sheets of different thicknesses. Different shock loads were generated by varying the driven gas pressures. The foams and sandwich panels were subjected to peak shock reflected pressures ranging from 50 bars to 150 bars and the corresponding transmitted pressure pulses were recorded. The behaviour of the foams and sandwich panels under shock wave loading was evaluated by post test visual damage assessment. The effect of face sheet thickness on failure mechanisms of sandwich panel is also studied. The failure mechanisms of foams at higher shock pressures were observed to be core crushing and core fracture, whereas sandwich panels exhibited face sheet deflection, core crushing, fibre breakage at back face sheet and back face delamination.

The present study describes the experimental results pertinent to the penetration of AA-2024, AA-6061 and AA-7017 plates with two different non-deformable steel projectiles. The diameters of the projectiles used for ballistic impact testing are 7.62 and 12.7 mm. The projectiles are impacted on the aluminium targets of 70 mm thickness with velocities in the range of 840±10 m/s. The results presented include variation in damage pattern in experimental alloys with respect to different projectiles. The microstructures and micro-hardness values along the projectile penetration path have been investigated to understand the material deformation behaviour. Some observations relating to the adiabatic shear band formation have also been presented. From the ballistic testing experiments, it is observed that AA-7017 plates display higher ballistic resistance among the tested aluminium alloys. The ballistic performance of the aluminium alloy plates have been correlated with their respective mechanical properties.

Energy absorption of two different types of composite laminates i.e. glass composite (E-glass/epoxy) and ultra high molecular weight polyethylene (UHMWPE) (Dyneema®) laminates were studied under low and high velocity impact. Instrumented drop weight impact tester was used for low velocities and sub machine carbine (SMC) gun was used for high velocity impact. Failure behaviour of both E-glass/epoxy and dyneema laminates during impact was studied and results of the energy absorption of the tested composite laminates have been presented. Dyneema laminates showed 2 times higher energy absorption than E-glass/epoxy laminate under high velocity impact. However, both the laminates have showed higher energy absorption at high velocity impact as compared to low velocity impact. Failure analysis on impacted laminates reveals that the E-glass/epoxy laminate undergoes elastic deformation, delamination and brittle failure of fibres, whereas dyneema laminates undergo plastic deformation and associated tensile stretching of fibres. The results obtained from this study bear significance in the development of light weight add-on and structural composite armours for the real time applications.

The present study is aimed at developing Carbon and E- glass based hybrid composite lamiantes for armour applications in order to get advantages of both the types of fibers. Three hybrid composite laminates based on carbon and E-glass in the weight ratio of 75:25, 50:50 and 25:75 with epoxy resin matrix were fabricated. For comparison purpose all carbon (C 100) and all E-glass (E 100) composites were also fabricated. High velocity impact tests were performed on laminates keeping carbon as strike face against 7.62 mm mild steel projectile. Present study revealed that the composite laminates comprising carbon and E-glass in the ratio of 50:50 (CE 50-50) has shown maximum performance in terms of energy absorption. It showed 17% & 30% higher energy absorption than C 100 and E 100 composites respectively. Damage areas at front and rear sides as well as damage volume are determined and found that its increase with increase in thickness.

The ballistic performance of bilayer silicon carbide/aluminium (SiC/Al) armour is assessed and compared with the alumina/aluminium (Al 2 O 3 /Al) armour using numerical analysis. For the numerical simulation of impact phenomena, ANSYS/AUTODYN software and phenomenological material models are used. The phenomenological models are JH-1 and JH-2 for brittle materials such as silicon carbide and alumina respectively and Johnson Cook (JC) model for ductile materials such as steel and aluminium. This study results shows that the ballistic performance of SiC/Al armour is higher than the Al 2 O 3 /Al armour and also SiC/Al target made severe damage to the projectile. The failure modes of these armours against blunt and ogive nose projectile are also evaluated.

The high hardness combined with its lower density makes boron carbide an attractive candidate for armour material. The ballistic performance of hot pressed boron carbide tiles were evaluated using standard Depth of Penetration (DOP) test method against hard steel armour piercing (AP) projectile of 12.7 mm caliber. Aluminium alloy 2024-T351 was used as backing material. The effect of tile thickness on ballistic efficiency was studied for tile thickness from 7.1 mm to 14.6 mm. Also projectile velocity effect was studied for velocities between 700 to 825 m/s. The ballistic efficiency with respect to tile thickness was initially found to increase and then decreases. Results on ballistic efficiency along with results of post ballistic analysis have been presented.

Steel containing 0.65 wt % nitrogen has been investigated for armour applications by subjecting it to different percentages of hot rolling. The effect of percentage reduction during hot rolling on microstructures, mechanical properties and ballistic performance has been studied. The ballistic performance of 6.5 mm, 7.5 mm thick plates against 7.62 ball and 16 mm, 17 mm thickness against 7.62AP projectiles were assessed. The nature of damage has been studied by varying percentage reduction during hot rolling of these plates for providing full protection.

To understand the flow and fracture behavior of near-α titanium alloy, the influence of stress triaxiality and strain rate on the failure behavior of this alloy was considered. The combined effect of strain rate, temperature and stress triaxiality on the behavior was studied by testing both smooth and notched specimens. Johnson-Cook (J-C) constitutive and fracture models were established based on high strain rate tensile data obtained from Split hopkinson tension bar (SHTB) and quasi-static tests. The Johnson Cook constitutive and fracture models have been calibrated. A modified Johnson–Cook model was established and proved to have high accuracy. The calibrated model has been validated by simulating the tension tests at various triaxialities using ANSYS autodyn software. Finite element simulations were used to predict the effective plastic strain versus triaxiality history within the deforming specimens. The fracture surfaces of specimens tested under various strain rates and temperatures were studied under scanning electron microscopy (SEM).

The dynamic recrystallization (DRX) behavior of a biomedical titanium Ti-13Nb-13Zr alloy has been investigated using the high temperature compression tests under wide range of strain rates (0.001-1/s) and temperatures 900-1050°C. A constitutive equation represented as a function of temperature, strain rate and true strain is developed and the hot deformation apparent activation energy is calculated about 534kJ/mol. By considering the exponential relationship between work-hardening rate (θ) and stress, a new mathematical model was proposed for predicting flow stress up to the critical strain during hot deformation. The mathematical model for predicting flow stress up to the critical strain exhibits better consistency and accuracy. The DRX kinetic equation of Ti-13Nb-13Zr alloy is described as XDRX=1-exp[-0.32(Ɛ-ƐcƐ(*))(2.3)] . The DRX kinetic model was validated by microstructure observation. It was also found that the process of DRX was promoted by decreasing strain rate and increasing deformation temperature. Eventually, the continuous dynamic recrystallization (CDRX) was identified to be the DRX mechanism using transmission electron microscope (TEM).