Flat-nosed Projectile Research Articles

Finite element analysis of the ballistic performance of monolithic and double-layered plates subjected to deformable projectiles

Impact problems have always been a field of interest for researchers because of their wide application in industries, especially in producing protective structures in defence. In the present study, finite element analysis is used to analyze the ballistic performance of monolithic and double-layered plates against cylindrical projectile with different nose shapes, viz. trapezoidal and flat-nosed, using a dynamic temperature displacement explicit analysis in the commercial finite element software ABAQUS. Further, the study compares the ballistic resistance (BR) of plates with different thicknesses (6, 10, and 12 mm) against the same configuration of projectiles. The Johnson–Cook (JC) constitutive strength and damage model characterizes the target and projectile material behavior. Mie–Grüneisen equation of state describes the material behavior of projectile and target under high pressure. The impact response of the target is compared in terms of plate deformation, ballistic limit velocity, and failure pattern of targets during impact. The monolithic plate has 2.42% higher impact resistance than the double-layered plate for the trapezoidal-nosed projectile, while for a flat-nosed projectile, double-layered plates have 9.42% higher BR than the monolithic plates. Moreover, the BR of plates (6, 10, and 12 mm) for flat-nosed projectiles is found to be 7.94, 5.56, and 4.59% higher than trapezoidal-nosed projectiles.

A plastic wave model for the perforation of a finite metal plate struck by a flat-ended projectile

A theoretical study is presented herein on the perforation of a finite metal plate struck by a flat-nosed projectile at normal incidence. Projectile deformations and plug formation are analyzed using plastic wave theory. Three modes of perforation (namely, perforation by a rigid projectile, perforation by a deformable projectile and perforation by an erosive projectile) are studied theoretically. Furthermore, a two-stage adiabatic shear model is introduced to describe the instability of adiabatic shear during the perforation process. Various equations are established and the critical conditions for the transition among the three modes are determined. It transpires that the present model predictions are in good agreement with the available experimental data for Weldox 460E steel plates struck transversely by flat-ended projectiles in terms of ballistic limit, residual velocity, transition temperature, projectile residual diameter, projectile residual length and plug thickness.

Strain rate effect analysis of hybrid composites under the high-velocity impact

In this paper, the damage behavior of fiber metal laminate (FML) is studied under high-velocity impact (HVI) at different strain rates (1 s−1, 100 s−1, and 1000 s−1) for flat, hemisphere, and sharp nosed projectiles. A finite element model has been used to examine the damage modes and failure processes of carbon fiber reinforced aluminium laminates (CRALLs) under HVI. This study is based on continuum damage mechanics. The damage criteria for aluminium (Al) and carbon fiber composite layers are identified by Johnson-Cook (J-C) and Hashin damage models, respectively. To analyse the inter-laminar de-lamination caused by the HVI, a cohesive surface regulated by bi-linear traction-separation is applied. The CRALL ballistic limit is analysed for different projectiles, which strike at initial velocity ranges from 60 m/s to 150 m/s to the CRALL. The obtained numerical results are in good agreement with the literature experimental results, which indicates the model is permissible for further analysis. The obtained results show that if strain rate varies from 1 s−1 to 1000 s−1 then CRALL ballistic limit velocity increases for all projectiles. The CRALL ballistic limit is the highest for flat nosed projectiles, followed by hemisphere and sharp nosed projectiles.

Experimental and numerical investigations into the ballistic performance of ultra-high molecular weight polyethylene fiber-reinforced laminates

The ballistic performance of ultra-high molecular weight polyethylene (UHMWPE) fiber-reinforced laminates is investigated experimentally and numerically. Several failure modes have been identified by examining the post-test targets, involving delamination, fiber fracture and bulging deformation. With the increase of impact velocity, the fiber recoil of the upper laminate becomes more evident, but the bulging deformation of the lower laminate is alleviated. A three-dimensional numerical model was developed to analyze the evolution of the whole ballistic response and the effects of projectile nose shape, spacing size and pitch angle on the ballistic behavior. Numerical results indicate that targets exhibit superior ballistic resistance under the impact of flat-nosed projectile. The ballistic performance of targets would be degraded with the increase of spacing size between two laminates. There exists a deactivation value for the spacing size to affect the ballistic behavior. Increasing the pitch angle between the sub-laminates could slightly improve the ballistic performance of targets by enhancing the delamination behavior and the development of bulging deformation.

Experimental Study on the Ballistic Resistance of S-shaped CFRP Foldcore Sandwich Structure against Flat-Nosed Projectile Impacts

Experimental Study on the Ballistic Resistance of S-shaped CFRP Foldcore Sandwich Structure against Flat-Nosed Projectile Impacts

Experimental study on pressure load of tank bulkhead under penetration of projectile

<p indent=0mm>Hydrodynamic ram is an important threat to the liquid containing structures such as the ship’s protective liquid tank and the aircraft’s fuel tank. Through the experiments of different projectiles penetrating liquid tank, the pressure curves of the front and rear plates are obtained, the pressure distribution characteristics of the plates are analyzed, and the effects of different positions, shapes and velocities on the peak value and impulse of the shock wave are compared. The results show that: (1) the peak value and impulse of the shock wave on the rear plate are obviously larger than that on the front plate, and there is an obvious secondary loading phenomenon, among which the corner’s is the most obvious; (2) the peak value and impulse of the shock wave on the front and rear plates of the liquid tank increase linearly with the increase of the incident velocity of the projectile; (3) the peak value and impulse of the shock wave formed by the flat-nosed projectile are the largest, while the spherical-nosed projectile is the second, and the ogive-nosed projectile is the smallest. In addition, ballistic deflection of the ogive-nosed projectile is more likely to occur.

A metal/UHMWPE/SiC multi-layered composite armor against ballistic impact of flat-nosed projectile

A novel multi-layered composite armor system is proposed for ballistic protection in the present study. The composite armor is composed of a ductile metal front, followed by a ceramic/UHMWPE laminate composite as the intermediate layer, and a ductile metal back layer. The ballistic performance of the composite armor against flat-nosed projectile was investigated experimentally and numerically. Experimental results show that the proposed composite armor exhibited several failure modes, including ductile hole enlargement of metallic face sheets, fragmentations and cracks of the ceramic layer, delamination, fiber fracture and bulge deformation of UHMWPE laminates. Three-dimensional numerical model was established to analyze the evolution of the whole ballistic response, and to discuss the effect of the ceramic layer placement and the mass allocation between the ceramic layer and UHMWPE laminate layer on the ballistic performance. Simulation results reveal the evident reduction in residual velocity that results from the optimal placement of the ceramic layer. Good balance among the contributions of the target components can be achieved to maximize the total energy absorption of composite armor by optimizing the ceramic placement strategy. The projectile residual velocity and the total energy absorption are insensitive to the mass ratio of ceramic layer to UHMWPE laminate layer within a certain range. Under the condition of a higher mass ratio, the specific energy absorption of UHMWPE layer can be significantly improved due to the full development of its bulging deformation. Consequently, it would benefit the energy absorption capability of the composite armor.

Failure analysis of semi-infinite concrete targets subjected to tubular projectiles impact

Improving the penetration efficiency of missiles into concrete is a practical research topic. In this paper, a tubular projectile was designed to enhance penetration diameter on concrete targets. To validate numerical simulation methods, an experiment of an ogive-nosed projectile penetrating a semi-infinite concrete target was reproduced by numerical simulation. Based on the validated numerical model, the penetration progress of a tubular projectile into a semi-infinite concrete target was analyzed. By assessing the penetration tunnel diameter and depth, the effects of key parameters, i.e., the wall thickness (15.0, 30.0, 60.0, 90.0, 120.0 mm) and velocity (400.0, 600.0, 800.0, 1000.0, 1200.0, 1400.0 m/s) of tubular projectile on penetrating concrete targets have been investigated in detail. Furthermore, the penetration performances of flat-nosed projectiles and tubular projectiles on concrete targets with the same mass were compared. The results indicate that with the increase in the wall thickness and velocity of the tubular projectiles, the penetration depth of the projectiles into the concrete target increases gradually, and the increase in the diameter of the tunnel is not obvious. In the case of the wall thickness of the tubular projectile which is greater than or equal to 30.0 mm, the concrete core, near the head of the tubular projectile, is completely fractured and separated from the concrete target. When the flat-nosed projectiles have the same mass and length with tubular projectiles, the diameter of the tunnel caused by the tubular projectile on the concrete targets is always much larger than that caused by the flat-nosed projectiles. The difference of them can be 60.5%. In the condition that the flat-nosed projectiles have the same mass and diameter with tubular projectiles, the depth of the tunnels caused by tubular projectiles in the concrete targets is always much larger than that caused by flat-nosed projectiles. The difference of them can be 95.6%.

Perforation Characteristics of Metal Target plate subjected to PELE

Abstract The perforation tests of 45 # steel target plate and 2A12 aluminium alloy target plate by PELE (the Penetrator with Lateral Efficiency) were carried out in this paper to study the perforation failure characteristics of metal target plate. The macroscopic morphology of perforation on the target plate and the plug was observed, and the perforation wall was cut and polished to observe the distribution and trend of the cracks in the perforation wall by scanning electron microscopy (SEM) and metallographic microscopy. The magnitude and direction of the force produced by PELE on the target during penetration were calculated by numerical simulation. The experimental and numerical results show that, the perforation failure of metal target plate by PELE is different from the ductile perforation by conical-nosed projectile and the punching failure by flat-nosed projectile. The longitudinal cross section of the perforation is funnel-shaped and the shape of the plug is like a circular truncated cone. In the process of penetrating the target plate, the expansion of the filling causes the jacket to exert a force with a certain angle to the direction of projectile movement, which is the main reason for the funnel-shaped perforation and the circular truncated cone shaped plug.

A note on the impact resistance of concrete target against rigid projectile

Concrete is an inhomogeneous cementitious composite which mainly consists of the cement matrix and the random distributed coarse aggregates. As for the most widely used construction materials of the protective structures designed to withstand the intentional or accidental impact loadings caused by high-speed projectiles, the impact resistance of concrete target against the rigid projectile impact is mainly dependent on the mass, density, impact velocity, diameter, and nose shape of the projectile, as well as strength and density of the target, and hardness and size of the coarse aggregates. However, the above influential parameters are not sufficiently considered in the existing cavity expansion–based model and constant resistance model for predicting the depth of penetration of a projectile. In this article, the influences of the hardness and size of the coarse aggregates on the depth of penetration are examined through the existing experimental data, and an improved rigid projectile penetration model for concrete target is proposed and validated by 19 sets of ogive- and flat-nosed projectile penetration tests.

Effect of a viscoelastic target on the impact response of a flat-nosed projectile

Taylor impact is a widely used strategy in which a flat-nosed projectile is fired onto a rigid anvil directly to determine the dynamic strength of rod specimens. Nowadays, the rigid anvil is often replaced by an output target bar to ensure the accuracy of measurement via recording strain signals in the output bar. For testing the dynamic strength of low-density materials, a low-impedance target bar, which exhibits viscoelastic characteristics is often employed. In this paper, an extended Taylor model is proposed to improve the idealization of treating the target bar as perfectly rigid material in the classic Taylor model, and the viscoelastic effect of the target bar is incorporated. The viscoelastic target bar is depicted by two elastic springs and one dashpot. Based on the plastic shock wave theory in the flat-nosed projectile associated with the viscoelastic wave analysis in the target bar, the viscoelastic effect of the target bar on the impact response of the flat-nosed projectile is investigated. The finite element simulation is also carried out to verify the theoretical model, and good agreement is found. The present theoretical model is also called the Taylor-cylinder Hopkinson impact, which provides a more accurate way to identify the dynamic material parameters. The dynamic responses of the present model are further compared with previous elastic and rigid target bar models. It is found that the viscoelastic effect of the target bar should be taken into consideration in the Taylor-cylinder Hopkinson impact test for low-impedance materials.

Ballistic resistance and energy absorption of honeycomb structures filled with reactive powder concrete prisms

Two kinds of innovative re-entrant and hexagonal cell honeycomb sandwich structures filled with reactive powder concrete were proposed, and the ballistic resistance and energy absorption of the sandwich structures were investigated by numerical simulations. The deformation and failure modes of the different structures were analyzed and evaluated in detail. The honeycomb sandwich structures filled with reactive powder concrete prisms improved the capacity of ballistic resistance and energy absorption significantly, compared to the normal reactive powder concrete plates and sandwich structures without reactive powder concrete prisms. The analysis shows that the auxetic re-entrant cell honeycomb sandwich structures have a better ballistic performance than the hexagonal cell honeycomb sandwich structures. The sandwich structures were subjected to impact by three kinds of projectiles: flat, hemispherical and conical nosed. The ballistic limit of the flat nosed projectile is the highest, while the impact performance of the conical and hemispherical nosed projectiles is obviously different from the flat nosed projectile, especially in a relative high velocity range. The sharper nose leads to a higher value of exit velocity and mass loss. In addition, effects of different design parameters on ballistic resistance were also studied by changing the thickness of honeycomb cell and face plates. Results indicate that the thickness of honeycomb walls and face plates have significant effect on the ballistic resistance and energy absorption in a relative low velocity range, while there are no big differences when the initial impact velocity exceeds 400 m/s.

Ballistic impact behaviors of aluminum alloy sandwich panels with honeycomb cores: An experimental study

To study the protection property of aluminum alloy sandwich panels with honeycomb cores under the attack of bullets or debris, quasi-static perforation, and ballistic impact tests were conducted, in which the thicknesses of the face sheet and core were 0.5–2.0 and 12.7 mm, respectively, while projectiles with diameter 7.5 mm and impact velocity 50–220 m/s were employed. Based on the experiments, the influences of impact velocity, face sheet thickness, core density as well as the nose shape of the projectiles were investigated. The results showed that in the impact tests, the sandwich panels dissipated much more energy than those in quasi-static perforation tests, and the energy absorption and ballistic limit of the sandwich panels increased with the increase of impact velocity. The influence of face sheet thickness was more remarkable than the core density, which was due to the relative density of honeycomb is too small. Although the increase of core density could induce the increase of energy absorption, this effect is more effective for thinner face sheet. Moreover, under the same impact velocity about 200 m/s and face sheet thickness 1.0 mm, the ballistic limit for conical-nosed projectile is highest, while it is lowest for flat-nosed projectile.

Effect of strength and ductility on deformation and fracture of three kinds of aluminum alloys during Taylor tests

The mechanical property of projectile material, especially the strength and ductility, will greatly affect the deformation and damage of a kinetic energy projectile in the process of penetration. This paper presents a comparison methodology concerning the deformation and fracture behavior of kinetic energy projectiles with three kinds of strength and ductility manufactured from 1100, 6061 and 2A12 aluminum alloy bars. In the experiments, flat-nosed projectiles were fired using a two-stage light gas gun against hard steel plates within the velocity range of 150–600 m/s. Experimental results showed that there are different deformation and fracture modes for the three kinds of projectiles within different velocity ranges. With the increasing of impact velocity, deformation and fracture modes for each kind of projectile are listed as follows, respectively: mushrooming, tensile splitting and sunflower-like petalling for 1100 projectiles with high ductility; mushrooming, shear cracking, shear petalling and petals falling off for 6061 projectiles with medium ductility; mushrooming, shearing cracking and fragmentation for 2A12 projectiles with low ductility. In order to achieve a more comprehensive understanding of the influence of strength and ductility on material fracture mechanism, microscopic observations of typical fracture surfaces were conducted by a scanning electron microscope (SEM).

Experimental and numerical study of water-filled vessel impacted by flat projectiles

To understand the failure modes and impact resistance of double-layer plates separated by water, a flat-nosed projectile was accelerated by a two-stage light gas gun against a water-filled vessel which was placed in an air-filled tank. Targets consisted of a tank made of two flat 5A06 aluminum alloy plates held by a high strength steel frame. The penetration process was recorded by a digital high-speed camera. The same projectile-target system was also used to fire the targets placed directly in air for comparison. Parallel numerical tests were also carried out. The result indicated that experimental and numerical results were in good agreement. Numerical simulations were able to capture the main physical behavior. It was also found that the impact resistance of double layer plates separated by water was lager than that of the target plates in air. Tearing was the main failure models of the water-filled vessel targets which was different from that of the target plates in air where the shear plugging was in dominate.

Numerical study on the perforation of fiber reinforced plastic laminates struck by high velocity projectiles

A numerical study is performed herein on the perforation of fiber reinforced plastic laminates struck normally by flat-nosed projectiles at high velocities. First, some previous constitutive models for fiber reinforced plastic composites are briefly reviewed and then a constitutive model is proposed to predict the perforation of fiber reinforced plastic laminates. The present constitutive model is developed based on the concept of continuum damage mechanics and criteria for different failure modes which take the quadratic form of various stress parameters. The effects of strain rate on the strength as well as the modulus of fiber reinforced plastic laminated materials are also considered in the model. It transpires that the present numerical simulations are in good agreement with experimental observations for the perforation of carbon fiber reinforced plastic, glass fiber reinforced plastic and kevlar fiber reinforced plastic laminates impacted by flat-ended projectiles in terms of deformation profile, ballistic limit and residual velocity. It also transpires that the present constitutive model is advantageous over the existing models.

Numerical analysis of the effect of weld-induced residual stress and plastic damage on the ballistic performance of welded steel plate

The current paper presents numerical analyses that elucidate the effects of post-weld residual stress and associated plastic damage on the ballistic performance of 316L austenitic steel plate. Impact simulations of an 18mm thick plate with a centreline three-pass slot weld by hemispherical-nosed and flat-nosed projectiles are performed, with initial velocities in the range of 300–800m/s. The numerical framework consists of three interdependent stages: (i) a weld model was developed in Abaqus/Standard and validated using two independent experimental data sets; (ii) a Johnson–Cook material model is calibrated and validated along with the shear failure fracture criterion available in Abaqus/Explicit for impact models; and (iii) the weld modelling results were transferred to an impact model built in Abaqus/Explicit, which employs the validated material and fracture models to predict the ballistic performance of welded plate. It is shown that the associated plastic strain damage accumulated during the welding process – and its distribution – has an adverse effect on the ballistic performance. It has also been determined that a fracture criterion that accounts for pre-existing damage in the weldment must be used for accurate impact analyses of welded structures.

Perforation of FRP laminates under impact by flat-nosed projectiles

A theoretical study is performed herein on the perforation of fibre-reinforced plastic laminates subjected to impact by flat-nosed projectiles in a wide range of velocities. Ballistic impact on FRP laminates is a very complex problem and it can be generally classified into two categories, i.e. global deformation with local rupture and wave-dominated local failure. Simple analytical models for both global deformation failure as well as wave-dominated local failure are first given, and a shear failure criterion is employed to predict the perforation of FRP laminates which fail in global deformation mode. By combining the wave-dominated local failure model and the concept of Von Karman’s critical impact velocity, a condition for the transition of the above mentioned two failure modes is obtained. It is shown that the model predictions are in good agreement with available experimental observations in terms of ballistic limits and critical conditions for the transition of failure modes.

Effect of projectile hardness on deformation and fracture behavior in the Taylor impact test

The ballistic perforation performance of a kinetic energy projectile would be much more influenced by the projectile’s deformation during the impact process. A projectile may suffer from large deformation and even fracture as more and more advanced materials are used as resistant components. A comparison investigation was presented in this study concerning the deformation and fracture behavior of kinetic energy projectiles manufactured from 38CrSi steel of two different hardness values. Flat-nosed projectiles were fired in a two-stage compressed gun test facility against hard steel plates within the velocity range of 200–600 m/s. The impact process was monitored by a high-speed camera. Experimental results showed that, for the soft projectiles there are three deformation and fracture modes, i.e., mushrooming, shear cracking and petalling, and that for the hard projectiles there are also three modes, mushrooming, shearing cracking and fragmentation.

Transition of Plugging Failure Modes for Ductile Metal Plates Under Impact by Flat-Nosed Projectiles#

This article deals with the perforation of ductile metal plates subjected to impact by flat-nosed projectiles at normal incidence. Generally speaking, ductile metal plates under impact by flat-ended missiles can fail either by global deformation combined with local shear rupture or by localized adiabatic shear plugging depending upon the geometrical and thermo-mechanical properties of both the targets and the projectiles. Modification is first made to the Bai–Johnson model for adiabatic shear plugging by taking account of strain rate effects using a thermo-viscoplastic constitutive equation instead of thermo-plastic material model and equations for the energy dissipated in the perforation process (perforation energy), the ballistic limit and the residual velocity are then obtained. Furthermore, a critical condition is obtained for differentiating localized adiabatic shear plugging from simple shear plugging failure with global deformations by comparing the modified Bai–Johnson model and the Wen–Jones model. It transpires that the present theoretical predictions are in good agreement with available experimental data in terms of the ballistic limits and the critical transition condition for the modes of plugging failure of ductile metal plates subjected to impact by flat-nosed missiles. It also transpires that the present model predicts well the residual velocities and the energies dissipated in the perforation process.