3D numerical simulations of sharp nosed projectile impact on ductile targets

Three-dimensional FE model is presented for perforation under normal and oblique impact of sharp nosed projectiles on single and layered ductile targets. Numerical simulations have been carried out to study the behavior of Weldox 460 E steel and 1100-H12 aluminum targets impacted by conical and ogive nosed steel projectiles respectively. Weldox 460 E steel targets of 12 mm thickness in single and double layered combination (2 × 6 mm) and 1100-H12 aluminum targets of 1 mm thickness in single and double layered combination (2 × 0.5 mm) impacted at 0°, 15° and 30° obliquity were considered for simulations. The results of monolithic and layered targets were compared for each angle of impact. Monolithic targets were found to have higher ballistic resistance than that of the layered in-contact targets of equivalent thickness. Failure of both the targets occurred through ductile hole enlargement. However, ogive nosed projectile failed 1 mm thick aluminum target through petal formation and conical nosed projectile failed 12 mm thick steel target through a circular or elliptical hole enclosed by a bulge at rear surface. The explicit algorithm of ABAQUS finite element code was used to carry out the numerical simulations. Various parameters which play critical role in numerical simulation such as element size and its aspect ratio have been studied.     

Impact response of sandwich plates with a pyramidal lattice core

The ballistic performance edge clamped 304 stainless-steel sandwich panels has been measured by impacting the plates at mid-span with a spherical steel projectile whose impact velocity ranged from 250 to 1300 m s⁻¹. The sandwich plates comprised two identical face sheets and a pyramidal truss core: the diameter of the impacting spherical projectile was approximately half the 25 mm truss core cell size. The ballistic behavior has been compared with monolithic 304 stainless-steel plates of approximately equal areal mass and with high-strength aluminum alloy (6061-T6) sandwich panels of identical geometry. The ballistic performance is quantified in terms of the entry and exit projectile velocities while high-speed photography is used to investigate the dynamic deformation and failure mechanisms. The stainless-steel sandwich panels were found to have a much higher ballistic resistance than the 6061-T6 aluminum alloy panels on a per volume basis but the ballistic energy absorption of the aluminum structures was slightly higher on a per unit mass basis. The ballistic performance of the monolithic and sandwich panels is almost identical though the failure mechanics of these two types of structures are rather different. At high impact velocities, the monolithic plates fail by ductile hole enlargement. By contrast, only the proximal face sheet of the sandwich plate undergoes this type of failure. The distal face sheet fails by a petalling mode over the entire velocity range investigated here. Given the substantially higher blast resistance of sandwich plates compared to monolithic plates of equal mass, we conclude that sandwich plates display a potential to outperform monolithic plates in multi-functional applications that combine blast resistance and ballistic performance.     

Plate perforation by deformable projectiles — A plastic wave theory

A one-dimensional wave propagation model of plate perforation is developed for cylindrical projectiles impacting plates at normal obliquity. This theory assumes that the projectile and plate materials are rigid-linearly strain-hardening and rigid-perfectly plastic respectively, with respect to engineering stress and strain. During penetration, the projectile deforms and a plug forms in the plate. The plug which is sheared from the plate is larger than the initial cross-section of the projectile. Residual velocity, plug mass and final plug thickness are determined for this model and compared with experiments on ductile metal plates impacted at velocities larger than the minimum perforation velocity.     

Effect of projectile nose shape,impact velocity and target thickness on the deformation behavior of layered plates

The present study is based on the experimental and numerical investigations of deformation behavior of layered aluminum plates of different thicknesses under the impact of flat, ogive and hemispherical nosed steel projectiles. Thin-layered plates arranged in various combinations were normally impacted at different velocities with the help of a pneumatic gun. Ballistic limit velocity and the residual velocity of the projectiles for each layered combination were obtained experimentally as well as from the finite element code, and these were compared with those of the single plates of equivalent thicknesses. For two layers, the residual velocity was comparable to that of the single plate, however, when the number of layers was increased the velocity drop was found to be higher in the case of the single plate. Ogive nosed projectile was found to be the most efficient penetrator of the layered target. Hemispherical nosed projectile required maximum energy for perforation. Deformation profiles of the target plates in the layered combinations were measured, and it was found that hemispherical nosed projectile caused highest plastic deformation of target plates. Numerical simulation of the problem was carried out using finite element code ABAQUS. Explicit solution technique of the code was used to analyze the perforation phenomenon. Results of the finite element analysis were compared with experiments and a good agreement between the two was found.     

Ballistic Limit of Single and Layered Aluminium Plates

Abstract: This paper presents an experimental and finite‐element investigation of ballistic limit of thin single and layered aluminium target plates. Blunt‐, ogive‐ and hemispherical‐nosed steel projectiles of 19 mm diameter were impacted on single and layered aluminium target plates of thicknesses 0.5, 0.71, 1.0, 1.5, 2.0, 2.5 and 3 mm with the help of a pressure gun to obtain the ballistic limit in each case. The ballistic limit of target plate was found to be considerably affected by the projectile nose shape. Thin monolithic target plates as well as layered in‐contact plates offered lowest ballistic resistance against the impact of ogive‐nosed projectiles. Thicker monolithic plates on the other hand, offered lowest resistance against the impact of blunt‐nosed projectiles. The ballistic resistance of the layered targets decreased with increase in the number of layers for constant overall target thickness. Axi‐symmetric numerical simulations were performed with ABAQUS/Explicit to compare the numerical predictions with experiments. 3D numerical simulations were also performed for single plate of 1.0 mm thickness and two layered plate of 0.5 mm thickness impacted by blunt‐, ogive‐ and hemispherical‐nosed projectiles. Good agreement was found between the numerical simulations and experiments. 3D numerical simulations accurately predicted the failure mode of target plates.     

Direct force measurement in normal and oblique impact of plates by projectiles

An experimental investigation of the forces produced by the penetration and perforation of thin aluminum and steel plates by cylindro-conical and hemispherically-tipped projectiles at 0, 15, 30 and 45° angles of incidence has been performed. Additionally, force histories were recorded for normal impact on Lexan, nylon and ceramic targets by conically-tipped strikers. Similar tests on Kevlar were not successful owing to the generation of voltages by rubbing of fibers that completely overwhelmed the transducer signal. A piezoelectric crystal bonded to the tail of the 12.7 mm diameter, 30 g projectiles followed by an inertial mass and a trailing wire provided the instrumentation. The strikers were propelled by means of a pneumatic gun at velocities ranging from 45 to 170 ms⁻¹. Displacement data obtained from high-speed photography for selected runs allowed curve fits to an analytical function which were compared to the directly recorded force histories.The effects of changes in initial velocity, angle of obliquity and striker tip on the peak force have been analyzed. A simple model has been developed for the perforation of plates by hemispherically-tipped projectiles at oblique incidence, and comparisons have been made with the measured force histories. A model was also devised to predict the peak forces obtained for oblique impact by cylindro-conical projectiles. The peak forces obtained experimentally were found to be relatively independent of the initial projectile velocity for shots where perforation occured. For the tests at speeds below the ballistic limit, the maximum forces were approximately proportional to the initial velocity.     

Effect of thin oblique moving plates on long rod projectiles: A reverse impact study

The geometry and motion of long rod projectiles after penetrating thin obliquely oriented and moving armour plates were studied. Plates moving in their normal directions towards as well as away from the projectile (scalar product of velocities negative and positive, respectively) were considered. The influences of plate velocity and obliquity (angle between the normal of the plate and the axis of the projectile) were investigated through small-scale reverse impact tests with tungsten projectiles of length 30 mm and diameter 2 mm, and with 2 mm-thick steel plates. The obliquity (30°, 60° and 70°) and the plate velocity (300 to −300 m/s) were varied systematically for a projectile velocity of 2000 m/s. The disturbing effect of the plate on the projectile was characterised in terms of changes in length, velocity, angular momentum, linear momentum and kinetic energy. Plates with obliquity 60–70° moving away from the projectiles with velocity 200–300 m/s were found to cause extensive fragmentation of the projectile and to have large disturbing effects in terms of all measures used.     

Perforation of sandwich plates with graded hollow sphere cores under impact loading

In this paper, sandwich plates made from 0.8 mm 2024 T3 aluminium alloy skin sheets and graded polymeric hollow sphere cores (having various density gradients) are studied. The experiments at 45 m/s were performed with an inversed perforation setup using SHPB system. Quasi-static tests using the same clamping system allow for the rate effect investigation. Numerical simulations are performed in order to get the indispensable local information (which is not experimentally available) to better understand the perforation process.     

Ballistic performance of multi-layered metallic plates impacted by a 7.62-mm APM2 projectile

This paper presents a numerical investigation of the ballistic performance of monolithic, double- and triple-layered metallic plates made of either steel or aluminium or a combination of these materials, impacted by a 7.62-mm APM2 projectile in the velocity range of 775–950 m/s. Numerical models were developed using the explicit finite element code LS-DYNA. It was found that monolithic plates have a better ballistic performance than that of multi-layered plates made of the same material. This effect diminishes with impact velocity. It was also found that double-layered plates with a thin front plate of aluminium and thick back steel plate exhibit greater resistance than multi-layered steel plates with similar areal density. These predictions indicate that multi-layered targets using different metallic materials should be investigated for improved ballistic performance and weight-savings.     

Perforation of AA5083-H116 aluminium plates with conical-nose steel projectiles—experimental study

The interest regarding use of aluminium alloys in lightweight protective structures is today increasing. Even so, the number of experimental and computational investigations giving detailed information on such problems is still rather limited. In this paper, perforation experiments have been performed on AA5083-H116 aluminium plates with thicknesses varying between 15 and 30 mm impacted by 20 mm diameter, 98 mm long, HRC 53 conical-nose hardened steel projectiles. In all tests, initial and residual velocities of the projectile were measured and a digital high-speed camera system was used to photograph the penetration and perforation process. Based on these measurements, impact versus residual velocity curves of the target plates were constructed and the ballistic limit velocity of each target was obtained. An analytical perforation model from the open literature is then used to predict the ballistic limit velocity, and excellent agreement with the experimental data is found. The experimental results are finally compared to similar experiments on steel and concrete targets, and the capacity of the different materials is evaluated in relation to total weight.     

Effect of reinforcement type on high velocity impact response of GRP plates using a sharp tip projectile

High velocity impact performance of glass reinforced polyester (GRP) resin composite plates with different type of reinforcement was investigated. The projectile used was a sharp tipped (30°) conical head with total length of 30 mm and shank length of 15 mm with weight of 9.74 g. Five different types of E-glass fiber reinforcement were used, including chopped strand mat (CSM), plain weave, satin weave, unidirectional and cross-ply unidirectional fiber reinforcements. A smooth barrel gas gun was used to conduct high velocity impact tests in the velocity range of 80–160 m/s. Composite plates with size of 15 cm × 15 cm were prepared in 3 and 6 mm thickness. Results showed higher ballistic limit velocity (velocity at which samples fully penetrated the target plates with zero residual velocity) for 3 mm GRP plates with cross-ply unidirectional reinforcement followed by unidirectional reinforcement and plain weave, the plates with satin weave and CSM reinforcements were almost in same level. The thicker specimens (6 mm), plates with plain weave reinforcement showed better ballistic performance towards sharp tipped conical projectile impact, followed by cross-ply unidirectional, satin weave, unidirectional and CSM reinforced plates. Experimentally determined ballistic limit velocity for all specimens correlate well with estimated ballistic limit values obtained in full perforation tests. Damage assessment conducted on all specimens indicated fiber tension and shear failure for thin-walled and sever delamination for the thick-walled specimens as the dominant failure modes.     

Deformation and fracture of a long-rod projectile induced by an oblique moving plate: Experimental tests

The influence of projectile length to diameter ratio (15, 30 and 45), plate thickness (0.5, 1 and 2 projectile diameters), projectile velocity (1500, 2000 and 2500 m/s) and plate velocity (−300 to 300 m/s) on the interaction between long-rod tungsten projectiles and oblique steel plates (obliquity 60°) was studied experimentally in small-scale reverse impact tests. The residual projectiles and their motions were characterised in terms of changes in length, velocity, angular momentum, linear momentum and kinetic energy. The parameters found to have the largest influence on the disturbance of the projectile were the plate velocity, in particular its direction, and the thickness of the plate. In the ranges studied, the influence of length to diameter ratio and of projectile velocity were found to be less important.     

Response of simulated propellant and explosives to projectile impact—III. Experimental and numerical results of warhead penetration and fragmentation

This paper is the third of a series concerned with the effects of projectile impact on a simulated explosive or propellant, called Propergol. Experiments were conducted to study the fragmentation and perforation response of disks of this material when subjected to impact by blunt and cylindro-conical strikers. Similar tests were conducted on layered targets of Propergol and steel, and also for a simulated warhead that was struck by armor-piercing projectiles. Data were obtained by velocity measurement, high-speed photography and post-mortem target examination including collected fragments.

A fragmentation oriented penetration code, AUTODYN(frag) was developed from the interfacing of a two-dimensional commercial finite difference code, AUTODYN, with a fragmentation subroutine, BFRACT, developed by other investigators. This program was utilized to study the microfracture and fragmentation processes in both monolithic and composite Propergol plates during their penetration by projectiles. In addition, numerical evaluations of the effects of simulated warhead penetration by armor-piercing bullets were conducted using the publicly available finite-element code DYNA2D.

The numerical results were compared with corresponding experimental data and also with the predictions of an analytical representation of the phenomenon, described in the second paper of the series. Reasonable agreement was obtained in the domain where the hypotheses concerning the structure of the analysis and of the computations were applicable.     

Perforation of sheets by pyramidal weapons such as arrowheads

Perforation experiments were performed through metal sheets employing pyramidal indenters having both regular polygonal bases and also non-regular lozenge-shaped bases. The tools also have a range of ‘point angles’. The evolution of petal radii as perforation proceeded was recorded. In the case of lozenge-based pyramids, fracture occurred only at the sharper edges located at the ends of the longer diagonal, with uncracked stretch zones at the ends of the shorter diagonal. Regular pyramids with a small number of edges produced cracking at every corner but perforations with six-sided indenters resulted in only a limited number of petals and cracks, fewer cracks being produced the ‘flatter’ the point. Experiments with cones also resulted in only limited number of petals and cracks. The results for forces, energy and petal radii of curvature were interpreted using modifications of the Wierzbicki and Thomas [Closed form solution for wedge cutting force through thin sheets. Int J Mech Sci 1993;35:209–29] analysis for the cutting of thin plates by wedges, together with independent determinations of yield strength and fracture toughness of the metal sheets. Experimental results make overall sense in relation to the theory but there is a consistent mismatch that is probably attributable to initial dishing of the sheets before initial perforation is complete. The relevance of the analysis to the performance of arrowheads perforating armour is discussed. What constitutes the best design of weapon against particular armour is investigated.     

Numerical simulations of impact behaviour of thin steel plates subjected to cylindrical,conical and hemispherical non-deformable projectiles

In this paper, a numerical study of normal perforation of thin steel plates impacted by different projectile shapes is reported. The numerical simulations of this problem have been performed using a finite element code, ABAQUS-Explicit with a fixed and an adaptive mesh for the plate. To define the thermoviscoplastic behaviour of the material constituting the plate, the Johnson–Cook model has been used. This homogeneous behaviour has been coupled with the Johnson–Cook fracture criterion to predict completely the perforation process. Three kinds of projectile shape (blunt, conical and hemispherical) have been simulated with a large range of impact velocities from 190 to 600 m/s. The analysis considers the influence of adiabatic shear bands, plastic work and the gradient of temperature generated in the plate. The numerical results predict correctly the behaviour projectile-plate in agreement with experimental data published by other authors.     

Normal impact of truncated oval-nosed projectiles on stiffened plates

The objective of this paper is to investigate the perforation capability of projectiles against stiffened plates and to determine how many stiffened plates can be perforated by projectiles. Some important experimental results on the perforation of stiffened plates, of a variety of configurations, by truncated oval-nosed projectiles at normal impact are introduced. A four-stage analytical model is formulated for the dynamic perforation of stiffened plates by rigid projectiles. By adopting an energy method, the model can be used to predict accurately the residual velocity of the projectiles. Numerical simulations have been performed for projectiles against single and layered plates adopted in the experiments. The perforation process is explored and deformation and failure modes are obtained. Good agreement is obtained between the numerical simulations, theoretical predictions and experimental results.     

Normal impact and perforation of thin plates by hemispherically-tipped projectiles — II. Experimental results

The present investigation is concerned with the measurement of the forces, permanent deflections, strains and plugs produced by rigid projectiles during contact and perforation of thin aluminium and mild steel plates. Tests were generally executed just below and just above the ballistic limit; a few experiments were conducted at much higher velocity. The direct force measurements were performed by means of a special technique using a projectile containing a piezoelectric quartz crystal. Observations were carried out on more than two hundred 2024-0 aluminium plates, 0.51, 1.27 and 3.175 mm thick and 1.22 mm thick mild steel plates. The tests involved the use of hard-steel projectiles of 12.7 and 6.35 mm diameter with three different nose shapes. The residual strains, of the order of 40%, were measured by using a grid method while the strain history in the vicinity of the impact point was determined by a specially designed gage capable of measuring strains up to 100%.     

分层对TC4钛合金板抗平头弹撞击失效特性的影响

使用Abaqus/Explicit有限元分析软件,开展平头弹撞击不同厚度双层TC4钛合金板数值模拟,研究双层TC4钛合金板撞击失效特性与失效模式随厚度变化规律及机理。通过对比撞击试验与仿真结果,验证数值模型和参数的有效性。在此基础上与等厚度单层TC4钛合金板的抗侵彻性能进行对比,结果表明,对于12.68 mm直径的平头弹,在靶板厚度2~16 mm内,双层结构的弹道极限与总厚度近似呈线性关系。由于单层靶板在4~10 mm内随着厚度增加,弹道极限无明显变化,所以等厚接触式双层结构在该厚度范围相比单层靶有明显的优势。在总厚度为8 mm时,双层靶优势最为明显,弹道极限相比单层靶提高了43%左右。