Projectile Nose Shape Research Articles

Investigation on Dynamics Characteristic of Multilayer Steel Plate Impacted by Projectile

The paper describes a work focused on the process of perforation of multilayer advanced high strength steel (AHSS). A numerical investigation has been carried out to analyze in details the perforation process subjected to normal impact by different nose shapes of projectiles. The perforation process has been simulated by the application of 3D analysis using IMPACT dynamic FE program suite. The comparison on failure modes depending on the projectile nose shape have been studied and evaluated. An appropriate constitutive relation was applied to describe the material behaviour of the multilayer target plate. The study covered different failure modes of perforated advanced high strength steel (AHSS) sheet according to different level of impact velocity ranging from 22 m/s to 78 m/s. The blunt projectile impact towards multilayer target plate leads to generation of plug formation and fragmentation while hemispherical projectile impact shows almost similar petals formation between first, second and third layer.

Numerical and Experimental Investigation of Supercavitating Flow Development Over Different Nose Shape Projectiles

Recently, the interest for new technologies to speed up underwater vehicles has increased. In this work, one of these technologies is investigated by creating a gaseous cavity, in which the high-speed underwater vehicles flow, to reduce the drag forces acting on these vehicles. A supercavitating flow over different nose projectile shapes is studied numerically and experimentally to understand the effect of the projectile nose shape on the supercavitating flow behavior. The numerical simulations are accomplished by using a commercial code named ESI-CFD through an unstructured mesh. Also, supercavity flow characteristics are investigated experimentally over the projectile body by using a high-speed camera. The numerical results are validated with other experimental results, where the stages of growth of the cavity over the different shapes projectiles are distinguished briefly and the existence of wake vortex is observed. The cavitator shape controls the time of cavity appearance and the drag coefficient value. The hemispherical nose projectile has the lowest drag coefficient value among all the tested projectiles. So, the cavitating flow behavior is investigated for the hemispherical nose projectile at different cavitation numbers ranging from 0.065 to 1.0. A new correlation is deduced to investigate the drag coefficient for the hemispherical projectile. Good agreement is obtained from the result of this correlation and previous data. Also, a new cavitator shape (a modified conical cavitator projectile) is examined, which is a modification of previously used one. The supercavity has not been formed using the modified conical cavitator projectile but it moves faster than any other examined projectile because it takes longer time before the cavity begins to decay.

The Effect of Projectile Nose Shape on the Critical Velocity of High-Performance Yarn

In this study, ballistic experiments were performed to determine the critical velocity of a Twaron® 2040 high-performance yarn transversely impacted by round projectiles. Four different round projectiles possessing a radius of curvature of 2 µm, 20 µm, 200 µm and 2 mm were used in this study. Load cells were mounted to the grips to measure the load history of the yarn upon impact. A high-speed camera was incorporated into the ballistic experimental setup to capture the failure process of the yarn upon impact. A scanning electron microscope was utilized to perform post-mortem failure analysis on the recovered specimens. The results showed that as the radius of curvature of the projectile increased, the critical velocity also increased. The critical velocities for all cases were bounded between those predicted from the Euler–Bernoulli beam and Smith models. Upon impact above the upper limit of the critical velocity, the axial loads revealed a demonstrative reduction. The failure surfaces changed from shear to fibrillation as the radius of curvature increased. For those specimens that failed in shear, Hertzian contact model was used to predict the critical velocity.

Experimental study on water entry of cylindrical projectiles with different nose shapes

Water entry experiments of projectiles with different nose shapes were performed under different entry angles and velocities using high-speed photography technology. The cavity flow characteristics of the near water surface, including splash jet, splash crown, surface seal of cavity, pull away, deep seal of cavity and cavity collapses, were systematically investigated using a high-speed camera. The emphasis of the study is paid on the effect of nose shape, water entry angle and velocity on the evolution of the air entraining cavity. The experimental results demonstrate that the nose shape of projectile has a significant influence on the jet flow, the cavity diameter and trajectory stability in the case of certain other conditions. On the other hand, the splash scale, cavity diameter increase gradually with the increasing of the water entry velocity, as well as the cavitation closed in advance. Furthermore, the water entry angle of the projectile plays an important role in the cavity evolution and the close type.

On the penetration of semi-infinite concrete targets by ogival-nosed projectiles at different velocities

Concrete has been widely used to construct protective structures in both civil engineering and defense installations which may be subjected to impact by projectiles at different velocities. In this paper, a theoretical study is presented on the penetration of a semi-infinite concrete target by an ogival-nosed projectile at different velocities within a unified framework. Depending upon impact velocity V0, the projectile may behave as rigid or quasi-rigid (with mass loss due to abrasion), deformable and erosive. The projectile penetrates the concrete target either in a rigid or quasi-rigid mode when V0 is less than rigid body velocity (VR) or in an erosive mode when V0 higher than hydrodynamic velocity (VH) or in a deformable mode when VR ≤ V0 < VH. The rigid body velocity is determined to be the impact velocity at which dynamic strength of the penetrator times the cross-section area of the shank is equal to the current resultant target resistance force as the projectile nose shape changes from ogival to blunt; the hydrodynamic velocity is estimated to be the impact velocity at which a stable mushrooming head is formed on the basis of physical consideration. It transpires that the present model correlates well with available experimental data for concrete penetration.

Experimental and numerical investigation on the effect of projectile nose shape in low-velocity impact loading on fiber metal laminate panels

In this paper, low-velocity impact responses of 2/1 GLARE 3 (a commercial type of fiber metal laminate) specimens were studied experimentally and numerically. The effects of indenter's nose shape (flat, conical, and hemispherical) on energy absorption and failure mechanisms were thoroughly investigated. Drop weight testing machine with different impact energies was used for experimental tests and numerical simulation was also carried out. Failure mechanisms, such as delamination, debonding, aluminum sheet rupture, and composite laminate fracture, were discussed by sectioning the tested specimens. The results indicate that maximum and minimum contact force occurred with flat and conical indenters, respectively. Also, the target absorbs the utmost energy under the penetration of flat indenter and least energy during conical indenter perforation. It is depicted that the deflection at the peak load represents the main failure of the panel. Consequently, front aluminum sheet failure is determinant in fiber metal laminate panels impacted by flat and hemispherical indenters where back aluminum sheet is more significant for fiber metal laminate panels impacted by the conical indenter. Numerical simulation verified by experimental results is extended to lower impact weights and more velocities, which are discussed.

Modeling on mass loss and nose blunting of high-speed penetrator into concrete target

Mass loss and nose blunting of the projectile are often observed in high-speed penetration into concrete target. A new theoretical model is established to present the process of mass abrasion of projectile during penetration and to predict the mass loss and nose shape of the residual projectile after penetration. In order to better describe the effect of aggregate on the mass abrasion of penetrator, both the aggregate volume fraction and its shear strength are introduced into the present model. In the present model, the caliber-radius-head value of projectile nose is a key parameter and the mass loss and nose shape of projectile can be obtained easily only by solving a differential equation for the caliber-radius-head value and the penetrating velocity v, which is much more convenient than the incremental calculation and all other methods of mass receding of projectile outer surface. The calculation results show a good agreement with experimental results. According to the present model of mass abrasion, the depth of penetration of projectile and its acceleration curve during penetration are further calculated by considering the effects of mass loss and nose blunting of projectile.

Ballistic performance evaluation of polycarbonate plate based on quasi-static perforation

The present work deals with the experimental investigation involving Quasi-static perforation of thin circular polycarbonate plate for ballistic performance evaluation. Effective diameter and thickness of polycarbonate plate is 205 mm and 2.66 mm respectively. Quasi-static perforation is performed on Servo-mechanical universal testing machine of capacity 50 kN using Blunt and Truncated cone penetrators of diameter 12.8 mm made of EN31 alloy steel. The velocity of the penetrator (indenter) is set at 2 mm/min and the impact is carried out at the centre of the plate. The results obtained based on Quasi-static tests are used in conjunction with the impact test performed using pneumatic gun set-up [1] for the same set of target plate and projectile nose shape. The ratio of the dynamic and quasi-static perforation energy defined as dynamic enhancement factor has been calculated. The variation of dynamic enhancement factor (DEF) with the impact velocity exhibit a linearly increasing pattern similar to those in literature for metallic plates [2].

Experimental investigation on dynamic failure of water-filled vessel subjected to projectile impact

In this investigation, a series of experiments are performed to study the deformation and failure of fluid-filled vessel subjected to high speed impact loading. The water-filled vessel with aluminum alloy target panels were impacted by the projectiles at the initial velocities of 100–300 m/s. Three different kinds of projectiles were considered to investigate the influence of nose shape of projectile on the failure modes of the water-filled tank. The high-speed photography was used to record the process of the projectile moving and the formation of cavity in water. The strain histories of target panels were measured by using the strain gauges. The results indicate that the hydrodynamic ram effect in the water-filled tank increased the damage of the target panels. The deformation of panels increased with the projectile nose coefficient (caliber-radius-head, CRH) increasing. The deformation and failure of the rear panel were more serious than those of the front panel. Additionally, the typical failure modes of the panels could be subdivided into three modes. The relationship between the kinetic energy and CRH value of the projectiles and the deformation of the panels was established.

Strain Behavior of Concrete Panels Subjected to Different Nose Shapes of Projectile Impact.

This study evaluates the fracture properties and rear-face strain distribution of nonreinforced and hooked steel fiber-reinforced concrete panels penetrated by projectiles of three different nose shapes: sharp, hemispherical, and flat. The sharp projectile nose resulted in a deeper penetration because of the concentration of the impact force. Conversely, the flat projectile nose resulted in shallower penetrations. The penetration based on different projectile nose shapes is directly related to the impact force transmitted to the rear face. Scabbing can be more accurately predicted by the tensile strain on the rear face of concrete due to the projectile nose shape. The tensile strain on the rear face of the concrete was reduced by the hooked steel fiber reinforcement because the hooked steel fiber absorbed some of the impact stress transmitted to the rear face of the concrete. Consequently, the strain behavior on the rear face of concrete according to the projectile nose shape was confirmed.

Perforation mechanics of 2024 aluminium protective plates subjected to impact by different nose shapes of projectiles

This paper focuses on the mechanical behaviour of aluminium alloy 2024-T351 under impact loading. This study has been carried out combining experimental and numerical techniques. Firstly, experimental impact tests were conducted on plates of 4mm of thickness covering impact velocities from 50m/s to 200m/s and varying the stress state through the projectile nose shape: conical, hemispherical and blunt. The mechanisms behind the perforation process were studied depending on the projectile configuration used by analyzing the associated failure modes and post-mortem deflection. Secondly, a numerical study of the mechanical behaviour of aluminium alloy 2024-T351 under impact loading was conducted. To this end, a three-dimensional model was developed in the finite element solver ABAQUS/Explicit. This model combines Lagrangian elements with Smoothed Particle Hydrodynamics (SPH) elements. A good correlation was obtained between numerical and experimental results in terms of residual and ballistic limit velocities.

Studying Normal and Oblique Perforation of Steel Plates with SPH Simulations

Axisymmetric and three-dimensional smoothed particle hydrodynamics (SPH) models are developed to simulate normal and oblique perforation of 12 mm-thick Weldox 460 E steel plates. In the models, a particle-to-particle contact algorithm including friction effect is employed to model interactions between projectile and target plate. A constitutive model coupling viscoplasticity and ductile damage is implemented to describe material behaviors of target plate. Both axisymmetric and three-dimensional SPH models are validated by existing experimental results. By using axisymmetric models, effects of projectile structure on normal perforation are systematically studied. Two factors of projectile structure, nose shape and aspect ratio, are considered. Residual velocities, ballistic limits and failure modes are obtained for different projectile nose shapes and aspect ratios. Effects of nose shape and aspect ratio on ballistic limits predicted by SPH simulations are compared with those obtained by an analytical equation. By using three-dimensional models, oblique perforation is simulated. Effects of oblique angle on impact processes are analyzed. Intervals of critical oblique angle of ricochet are obtained for different impact velocities and caliber-radius-head values of ogival projectile. The results obtained in this work can provide reference for the design of protective structures with steels and similar materials. The SPH with contact algorithm including friction effect is proved to be a very effective method for ballistic impact simulation.

Reprint of: Projectile penetration into sand: Relative density of sand and projectile nose shape and mass

Compacted granular materials, like sand, have a tendency to dilate and expand under shear loading. Such tendency of dilation is beneficial to inhibit projectile penetration. Furthermore, the higher the striking velocity of a given projectile, the higher is the peak strength of the sand sample. Different nose shapes (spherical, flat, hemispherical, conical and ogival) and mass (7g, 15g and 20g) of projectiles were fired into sand samples of relative densities ranging from medium dense to very dense state (60%, 75% and 90%). Results showed that the pointed ogival head projectile had the lowest ballistic limit, whereas the blunt flat head projectile required the highest ballistic energy to defeat the sand block. Despite visible effect of nose shape, the mass of projectile has a larger influence on the amount of absorbed energy. On the other hand, initial compaction of the sand alters the depth of penetration marginally. This is attributed to the projectile impact which compacts the sand as the projectile penetrates through the sand sample. A strong linear correlation between projectile nose shape, mass and ballistic impact energy was established in this study, which allows protective engineers to easily design sand barriers to defeat a range of projectiles. Furthermore, it was found that the energy absorption of sand remains high even when subjected to striking velocities way beyond its ballistic limit. This opens up avenues for sand barriers to be used as sacrificial layer of a composite lightweight protective barrier.

Influence of projectile nose shape and incidence angle on the ballistic perforation of laminated glass fiber composite plate

In this study, experimental and finite element analyses of perforation behaviour of unidirectional glass fiber reinforced cross ply laminate have been presented, considering different projectile nose shapes, incidence velocities, incidence angle and laminate thickness. A pneumatic gun was used to propel 52 g steel projectile of diameter 19 mm at incidence velocity up to 300 m/s, where the projectiles are having different nose shapes such as ogival, conical, spherical and blunt. The target plate of size 140 mm × 140 mm and thickness 3.3 and 6.6 mm were made by unidirectional (UD) glass fiber with orientation (0°/90°/90°/0°) and (0°/90°/90°/0°)2 respectively. A three dimensional finite element model is developed using Lagrangian, eight nodded brick element in ANSYS/AUTODYN, v14.5. The elastic properties of GFRP laminate is obtained from tensile tests in Universal Testing Machine in the civil engineering laboratory of IIT Roorkee, India. The velocity and acceleration-time histories of projectile along with ballistic limit, energy absorption and damage pattern in target plate are presented. The results obtained from numerical simulation are having good correlation with the corresponding experimental values and many new interesting results are also generated especially for oblique impact.

Projectile penetration into sand: Relative density of sand and projectile nose shape and mass

Compacted granular materials, like sand, have a tendency to dilate and expand under shear loading. Such tendency of dilation is beneficial to inhibit projectile penetration. Furthermore, the higher the striking velocity of a given projectile, the higher is the peak strength of the sand sample. Different nose shapes (spherical, flat, hemispherical, conical and ogival) and mass (7g, 15g and 20g) of projectiles were fired into sand samples of relative densities ranging from medium dense to very dense state (60%, 75% and 90%). Results showed that the pointed ogival head projectile had the lowest ballistic limit, whereas the blunt flat head projectile required the highest ballistic energy to defeat the sand block. Despite visible effect of nose shape, the mass of projectile has a larger influence on the amount of absorbed energy. On the other hand, initial compaction of the sand alters the depth of penetration marginally. This is attributed to the projectile impact which compacts the sand as the projectile penetrates through the sand sample. A strong linear correlation between projectile nose shape, mass and ballistic impact energy was established in this study, which allows protective engineers to easily design sand barriers to defeat a range of projectiles. Furthermore, it was found that the energy absorption of sand remains high even when subjected to striking velocities way beyond its ballistic limit. This opens up avenues for sand barriers to be used as sacrificial layer of a composite lightweight protective barrier.

Influence of Target Span and Boundary Conditions on Ballistic Limit of Thin Aluminum Plate

A collective study was performed to probe the influence of projectile nose shape, target span and target boundary condition on ballistic limit of thin aluminium plates. 1 mm thick 1100-H12 aluminium target plates were normally impacted by ogive and blunt nosed projectiles of 19 mm diameter and 50.8 mm length. The target span was varied as 95, 190, 285, 380, 475, 570, 665 and 760 mm whereas the target boundary condition was studied by varying the fixity at the target circumference region as 100%, 75%, 50% and 25%. ABAQUS/Explicit finite element code using Johnson-Cook elasto-viscoplastic material model were employed to carry out the numerical simulation. To validity of numerical results are revealed by experiments performed on pressure gun in the sub-ordnance velocity regime.The numerical as well as experimental study revealed that the ballistic limit of thin target plate was significantly affected by target span as well as target circumference fixity. The ballistic limit increases with increase in target span diameter while opposite trend was observed with increase in the region of fixity.

Behaviour of GFRP composite plate under ballistic impact: experimental and FE analyses

In this paper, experimental as well as numerical analysis of Glass Fiber Reinforced Polymer (GFRP) laminated composite has been presented under ballistic impact with varying projectile nose shapes (conical, ogival and spherical) and incidence velocities. The experimental impact tests on GFRP composite plate reinforced with woven glass fiber (<TEX>$0^{\circ}/90^{\circ}$</TEX>)s are performed by using pneumatic gun. A three dimensional finite element model is developed in AUTODYN hydro code to validate the experimental results and to study the ballistic perforation characteristic of the target with different parametric variations. The influence of projectile nose shapes, plate thickness and incidence velocity on the variation of residual velocity, ballistic limit, contact force-time histories, energy absorption, damage pattern and damage area in the composite target have been studied. The material characterization of GFRP composite is carried out as required for the progressive damage analysis of composite. The numerical results from the present FE model in terms of residual velocity, absorbed energy, damage pattern and damage area are having close agreement with the results from the experimental impact tests.

Ballistic analysis of fiber metal laminates impacted by flat and conical impactors

In the present study, the ballistic limit of GLARE is investigated experimentally and numerically. Ballistic tests were conducted using one stage gas gun. In the experimental part, the ballistic limit of GLARE was determined. The effect of aluminum lamina thickness and the nose shape of projectile on the ballistic limit were also investigated. The experimental results show that the ballistic limit of GLARE impacted by a flat projectile is higher than in the case of a conical nose projectile, and that by decreasing the aluminum laminate thickness from 0.5mm to 0.3mm, the Specific Perforation Energy (SPE) is increased. In the numerical section, the penetration process was simulated using LS–DYNA software. The validation of the finite element model was done by experimental results. The effects of various involved parameters such as laminate thickness, mass and radii of impactor were also investigated. The numerical results prove the efficiency of GLARE over bare aluminum laminate with equal thickness, due to the lower deflection and higher SPE. Furthermore, the less the mass of the impactor or the greater the diameter of the flat projectile, the greater the ballistic limit of GLARE. Reasonable agreement is concluded between the numerical and experimental results.

반구형과 평탄형 선단 비상체의 충돌을 받는 콘크리트의 파괴특성

본 연구에서는 반구형과 평탄형의 비상체를 이용하여 일반콘크리트와 섬유보강콘크리트에 충격시험을 진행한 후 파괴깊이와 형태, 파괴직경, 배면의 인장변형을 평가하였다. 선단면적이 작을수록 충격력의 집중에 의해 파괴깊이는 크고 표면파괴 직경은 작게 되는 것으로 확인되었다. 반면에 선단면적이 클수록 파괴깊이는 작지만 표면파괴직경은 크게 되었다. 일반콘크리트와 섬유보강 콘크리트에서 유사한 표면파괴와 배면변형이 발생하였으나 인장변형의 크기는 일반콘크리트에 비해 섬유보강 콘크리트가 작은 것으로 나타났다. 또한, 비상체의 선단형상에 따른 표면관입의 형태와 배면의 인장변형 사이에 직접적인 연관이 있는 것으로 사료된다. 따라서 콘크리트의 배면박리한계두께 예측 시에는 표면관입깊이뿐만 아니라 배면의 변형거동 또한 고려할 필요성이 있을 것으로 사료된다. In this study, projectiles with 2 kinds of nose shape: spherical and flat were impacted into normal concrete and fiber reinforced concrete panels. The fracture depth and form, crater diameter, tensile strain at rear face were evaluated. It was confirmed that smaller projectile nose areas resulted in deeper penetrations associated with concentrated impact forces and small front-face crater diameters in impact test. Conversely, larger projectile nose areas resulted in shallower penetrations and larger front-face fracture diameters. Similar front-face failure and strain distribution relationships based on the projectile nose shape were observed for normal and fiber-reinforced concrete although the rear-face tensile strain and scabbing were significantly reduced by the fiber reinforcement. In addition, a direct relationship was confirmed between the penetration depth based on the projectile nose shape and the tensile strain on the rear face. Thus the impact strain behavior is required to predict the scabbing behavior with penetration depth.

Rigid and eroding projectile penetration into concrete targets based on an extended dynamic cavity expansion model

A hyperbolic yield criterion and Murnaghan equation of state were introduced to describe the plastic behavior of concrete material under projectile penetration, and an extended dynamic cavity expansion model was proposed. Then, a unified one-dimensional resistance of concrete target to projectile penetration was formulated, in which the projectile nose shape influences were taken into account by three non-dimensional coefficients. Furthermore, combined with the Newton's second law and Alekseevskii-Tate equations, both rigid and eroding projectile penetration models into concrete targets were established. By comparing with the existing tests data as well as prediction results of previous model based on the linear yield criterion and equation of state, the proposed models were verified. Besides, a series of practical parameters of hyperbolic yield criterion and Murnaghan EOS for the extended dynamic cavity expansion model were given and verified.