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One of the primary design considerations of earth-orbiting spacecraft is the mitigation of the damage that might occur from an on-orbit MMOD impact. Traditional damage-resistant design consists of a ‘bumper’ that is placed a small distance away from a spacecraft component or from the wall of the element in which it is housed. The performance of such a multi-wall structural element is typically characterized by its ballistic limit equation (BLE), which defines the threshold particle size that results in a failure of the spacecraft element. BLEs are also key components of any micro-meteoroid/orbital debris (MMOD) risk assessment calculations. However, these assessments often call for BLEs to predict impact response for projectiles made of materials not used in the development of those BLEs. The question naturally arises regarding how close are the predictions of such BLEs when used in impact scenarios involving projectiles made of materials not necessarily considered in their development. In an effort to address this issue, a study was performed with the objective of assessing the validity of the NNO BLE for non-aluminum particles. Particle materials considered included steel, copper, and Al 2 O 3 (i.e. particles that are made of materials that are more dense than aluminum). Comparisons are made between actual test results involving these non-aluminum projectiles and the predictions of the NNO BLE. In nearly all cases, the NNO BLE was found not to work very well in the predicting failure / no failure response of these non-aluminum projectiles. A new NNO-type BLE is then developed that can be used to more reliably predict the response of dual-wall systems under the hypervelocity impact of such “heavier” non-aluminum projectiles. [ABSTRACT FROM AUTHOR]

Effect of heat treatment on mechanical properties and ballistic resistance of AA-7017 aluminium alloy plates has been investigated. The stress-strain behaviour of AA-7017 plates subjected to different heat treatment schedules namely under-aging, peak aging and over-aging, is evaluated from quasi-static tension tests. The heat-treated plates display large differences in static mechanical properties in terms of strength and ductility. The peak-aged plate shows the highest strength and hardness followed by the under-aged and over-aged materials. The ballistic resistance of these plates are evaluated by impacting deformable projectiles at a velocity of 830±10 m/s at a normal angle of attack. The peak-aged plate exhibits the best ballistic penetration resistance. The changes in the mechanical properties with different heat treatments have been correlated with ballistic performance of the AA-7017 alloy. Both the post ballistic micro-structural observations and micro-hardness measurements adjacent to the impacted crater walls have been carried out to understand the change in material deformation behaviour with heat treatment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Conical aluminium projectiles of apex angle 34 degrees were made to impact thin aluminium targets inclined at an angle of 60 degrees at low subordnance velocities where material strength effects are still valid. Thin targets of thickness 1.5 mm and 2 mm underwent failure by reverse petalling as the projectiles penetrated the targets. Projectiles underwent ricochet while impacting 2.5 mm targets causing severe dents and visible contact marks on the target. While the projectile nose tips were separated in the 1.5 mm and 2 mm cases, the projectiles impacting 2.5 mm targets underwent substantial nose deformation. Numerical simulation performed using ABAQUS/Explicit was able to capture the projectile deformation and target deformation quite well phenomenologically. [ABSTRACT FROM AUTHOR]

The fundamental material response of a viscoelastic material when impacted by a ballistic projectile has important implication for the defense, law enforcement, and medical communities particularly for the evaluation of protective systems. In this paper, we systematically vary the modulus and toughness of a synthetic polymer gel to determine their respective influence on the velocity-dependent penetration of a spherical projectile. The polymer gels were characterized using tensile, compression, and rheological testing taking special care to address the unique challenges associated with obtaining high fidelity mechanical data on highly conformal materials. The depth of penetration data was accurately described using the elastic Froude number for viscoelastic gels ranging in Young’s modulus from ~60 to 630 kPa. The minimum velocity of penetration was determined to scale with the gel toughness divided by the gel modulus, a qualitative estimate for the zone of deformation size scale upon impact. We anticipate that this work will provide insight into the critical material factors that control ballistic penetration behavior in soft materials and aid in the design and development of new ballistic testing media. [ABSTRACT FROM AUTHOR]

The asymmetric radial crack patterns that occur in brittle targets when impacted by high velocity projectiles are explained using a Phenomenological Mechanochemistry of Damage (PMD) engineering model. The developed model, which constitutes a simplification of the generalized PMD framework, reveals an energy instability during failure of brittle materials configured in a purely symmetric geometry and impact configuration. The underlying cause of the instability is due to the competition between stored elastic energy and the energy associated with new surface creation through broken chemical bonds. The instability manifests itself in the form of asymmetric radial cracking in the brittle target. The model is built upon the general PMD framework and assumes the target material is sufficiently brittle that strains are small and linear elasticity is applicable. Furthermore, the impact geometry is assumed to be purely symmetric, which leads to a reduction of the geometry to a one-dimensional radial configuration. The model is not restricted to any ballistic impact speed regime, provided the target material remains in the solid phase. [ABSTRACT FROM AUTHOR]

At present, the use of refined numerical simulation is gaining more and more importance, especially in extreme load cases where large experimental test programmes are not feasible. A validated numerical methodology can be exploited to investigate critical behaviour as a “virtual test”. According to this premise, a numerical investigation is presented in this work to study the ballistic resistance of Kevlar29-Epoxy fabric plates subjected to impacts of small calibre projectiles, armour piercing (AP), ball type, and a blunt shaped projectile (BSP), all with a 7.62 mm diameter. The numerical models were developed using the explicit finite element code LS - DYNA. The composite plate is 5 mm thick, made up of 12 layers. The fabric is impregnated in Epoxy matrix, to guarantee both structural and ballistic resistance, and is a 2D plain-weave. The mechanical properties of the projectiles’ deformable materials were modelled by means of the Johnson-Cook plasticity model, which also includes the failure criterion. The composite plate is modelled using a mixed Macro-homogenous / Meso-heterogeneous approach. In particular, the area around the impact adopts the Meso-heterogeneous modelling, in which the woven yarns and the matrix are separate parts able to interact, to increase the efficiency of the numerical methodology, allowing the modelling of the friction between the yarns, the delamination and the fibre-matrix debonding. This method needs to assign separately the mechanical properties to the fabric and the matrix as well as the damage criteria for the yarns, the matrix and the delamination. In the Macro-homogenous approach, which models the remainder of the composite plate, the yarns and the matrix are considered as a unique homogenous mean, to which equivalent orthotropic mechanical properties of the impregnated fabric are assigned. The numerical investigation mainly focuses on the residual velocity of the impacting projectiles, identifying the ballistic limit of each couple projectile-target. [ABSTRACT FROM AUTHOR]

This paper describes a cost effective automated methodology to analyze launch video of artillery projectiles. Image processing and computer vision techniques are used to segment and classify the projectile shape in each video frame. Within minutes of being fired, the initial position, velocity, and orientation history of the projectile in three-dimensional space is determined at the gun site. An overview of several standard methods used by the Army to characterize pitching and yawing motion of projectiles is included, as well as a discussion of the limitations of these methods. Results from real artillery testing using the automated video analysis method are validated through comparisons to results measured using conventional techniques. [ABSTRACT FROM AUTHOR]

High-speed video has been used by ballistics engineers as a cost-effective technique to measure the spin-rates of both spin-stabilized and fin-stabilized artillery projectiles. Often at test ranges, state-of-the-art video systems are used to verify critical launch events following muzzle exit. From manual analysis of these videos, important performance metrics such as velocity, pitch angle, and spin-rate can be estimated. To do this, operators step through the video frames and record the time at which certain fiducial markings or numbered stripes are observed on the projectile as it rotates. The different methods evaluated in this paper are automated processes for calculating the muzzle-exit spin-rate from launch videos of spin-stabilized artillery projectiles painted with stripes. Image processing and computer vision techniques are employed to segment the shape of the projectile and extract the stripe pattern in each video frame. The most accurate algorithm estimates are validated to within 0.02 % for both laboratory and computer-simulated flight video and within 0.13 % for manual analysis of real flight video. The sensitivities of the methods to image resolution, video frame-rate, and the length of flight captured are evaluated. Areas of continued research and recommendations for increasing the accuracy of measurements in future tests are also identified. [ABSTRACT FROM AUTHOR]

A statistics based ballistic test method is presented for use when comparing multiple groups of test articles of unknown relative ballistic perforation resistance. The method is intended to be more efficient than many traditional methods for research and development testing. To establish the validity of the method, it is employed in this study to compare test groups of known relative ballistic performance. Multiple groups of test articles were perforated using consistent projectiles and impact conditions. Test groups were made of rolled homogeneous armor (RHA) plates and differed in thickness. After perforation, each residual projectile was captured behind the target and its mass was measured. The residual masses measured for each test group were analyzed to provide ballistic performance rankings with associated confidence levels. When compared to traditional V50 methods, the residual mass (RM) method was found to require fewer test events and be more tolerant of variations in impact conditions. [ABSTRACT FROM AUTHOR]

Abstract: Ballistic gelatin is frequently used as a model for soft biological tissues that experience projectile impact. In this paper we investigate the response of a number of gelatin materials to the penetration of spherical steel projectiles (7 to 11mm diameter) with a range of lower impacting velocities (<120m/s). The results of sphere penetration depth versus projectile velocity are found to be linear for all systems above a certain threshold velocity required for initiating penetration. The data for a specific material impacted with different diameter spheres were able to be condensed to a single curve when the penetration depth was normalised by the projectile diameter. When the results are compared with a number of predictive relationships available in the literature, it is found that over the range of projectiles and compositions used, the results fit a simple relationship that takes into account the projectile diameter, the threshold velocity for penetration into the gelatin and a value of the shear modulus of the gelatin estimated from the threshold velocity for penetration. The normalised depth is found to fit the elastic Froude number when this is modified to allow for a threshold impact velocity. The normalised penetration data are found to best fit this modified elastic Froude number with a slope of 1/2 instead of 1/3 as suggested by Akers and Belmonte (2006). Possible explanations for this difference are discussed. [Copyright &y& Elsevier]

Ballistic impact response of ceramic- composite armor, consisting of zirconia toughened alumina (ZTA) ceramic front and aramid laminated composite as backing, against 7.62 mm armor piercing (AP) projectiles has been studied. Two types of backing composite laminates i.e. Twaron-epoxy and Twaron-polypropylene (PP) of 10 mm and 15 mm thickness were used with a ceramic face of 4mm thick ZTA. The ceramic- faced and the stand alone composite laminates were subjected to ballistic impact of steel core 7.62 mm AP projectiles with varying impact velocities and their V50 ballistic limit (BLl) was determined. A sharp rise in BL was observed due to addition of ceramic front layer as compared to stand alone ones. The impact energy was absorbed during penetration primarily by fracture of ceramic, deformation and fracture of projectile and elastic-plastic deformation of flexible backing composite layer. The breaking of ceramic tiles were only limited to impact area and did not spread to whole surface and projectile shattering above BLl and blunting on impact below BLl was observed. The ceramic-faced composites showed higher BL with Twaron-PP as backing than Twaron-epoxy laminate of same thickness. This combination of ceramic-composite laminates exhibited better multi-hit resistance capability; ideal for light weight armor. [ABSTRACT FROM AUTHOR]

Abstract: Development and testing of a novel armor system that defeats high-velocity projectiles and penetrators is described, from a phenomenological perspective. The process is covered where fundamental principles of shock mechanics and high fidelity computational physics (HFCP) simulations are used to create the armor system, from concept to proof testing. This armor development effort started with a “clean sheet,” which allowed for the basic ideas of penetration mechanics and advanced simulation to be brought to bear. Particular attention was paid to the nature of the two threats the armor was intended to stop: (1) three .50 caliber armor piercing (AP) projectiles at 850 meters per second, fired one at a time and grouped within a 5 centimeter diameter circle, and (2) an 18.6 gram mild steel projectile at 2,500 meters per second. The impact response of each threat is fundamentally different, and thus requires different mechanisms to defeat. Primary constraints on the armor system were minimal cost, no ceramic components, and minimal weight. There was freedom to make the system relatively thick, which allowed for the use of spaced components to progressively defeat each threat. Simulation was applied to determine geometries and materials that break up and yaw the AP threat, while maintaining multi-hit robustness. Simulation was also used to adapt the design to produce shattering shock pressures in the higher velocity mild steel, and then arrest of the resulting debris cloud. Simulations were performed using an in-house developed Lagrangian hydrocode having smooth particle hydrodynamic (SPH) capabilities. Outlined items include the material and failure models used, benefits of Lagrange-to-SPH conversion, and advantages of massive parallel processing capabilities which enabled the HFCP simulations. Also outlined is a design process that relies on the simulation capability to achieve minimal prototyping and testing. Results from proof tests are shown. Comparisons are made to show that simulations match well with the test data. [Copyright &y& Elsevier]

A great potential direction of development is the structures design for ballistic protection. Significant progress achieved by scientists, designers and manufacturers of advanced materials, used for individual ballistic protection, allowed, at this level, the competition revival, between projectile and armor. The paper presents the way of achieving and testing 6 variants of ballistic packages made of Kevlar laminate fabric, Kevlar XP and metallic fabric, within the Testing Laboratory for Ballistic and Pyrotechnic Protection of the Scientific Research Center for CBRN Defense and Ecology. [ABSTRACT FROM AUTHOR]

This paper put forward a method of reducing the armor-piercing projectile hit probability by investigating the characteristics of modern tank fire control system and armor-piercing projectile. A hit probability model based on traditional firing theory was established and analyzed. The results show that this method is effective. The further study points out that the most effective way to decrease the hit probability is reducing the response time of the target. [ABSTRACT FROM AUTHOR]

The performance of 7.62×54r BS32 armour-piercing incendiary (API) projectiles against ceramic-faced armour is investigated in trials for yawed impacts. Controlled yaw of the projectile was induced by chamfering the rear of the projectile, producing strong asymmetric lift forces on the tail of the round during the intermediate ballistics phase. High-speed video recorded yaw in two orthogonal planes immediately before impact. Projectile yaw varied in a sinusoidal manner at approximately 3.5m wavelength with a maximum of 8-14° at approximately 10m from the muzzle. Logistic regression was used to determine the penetration probability curve and V50 ballistic limit velocity which was found to be 735 ms-1 for the un-yawed projectiles but only 685 ms-1 for the yawed projectiles. [ABSTRACT FROM AUTHOR]

Copyright of Annals of 'Constantin Brancusi' University of Targu-Jiu. Engineering Series / Analele Universităţii Constantin Brâncuşi din Târgu-Jiu. Seria Inginerie is the property of Universitatea Constantin Brancusi din Targu-Jiu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

with all less-than-lethal weapons, the user is frequently left to estimate the optimum effective range of their weapon. Factory literature often exaggerates effective ranges and other features, which can be misleading and potentially dangerous in the deployment of the weapon. Using a modular combat shotgun and its three barrels, this study examined the accuracy of 12 gauge bean bag rounds in relation to barrel length. Accuracy was measured by point of impact and projectile spread in relation to the deviation from the point of aim. Our observations for the selected shotgun and bean bag rounds show that, at distances under 12 m (40 ft), the projectile was both accurate and reliable. At greater distances, both accuracy and reliability decreased. The 25 cm (10 in), 36 cm (14 in), and 46 cm (18 in) barrels can be used in close proximity from 3 m (10 ft)--15 m (50 ft) without a considerable loss of accuracy. This is of major significance as the use of shotguns during tactical room clearing is often limited by the length of barrel. These findings suggest that even the shortest length barrel tested would perform well if the targets are not engaged beyond 15 m (50 ft). Beyond this distance, the 46 cm (18 in) barrel is the most accurate performer and will reliably engage targets out to the maximum tested range of 24 m (80 ft). [ABSTRACT FROM AUTHOR]

The swerve response of fin- and spin-stabilized projectiles to control mechanism inputs is sometimes not intuitive. This paper seeks to explain the basic parameters that govern the swerve of projectiles excited by control inputs. By modeling the overall effect of a generalized control mechanism as a nonrolling reference frame force applied to a point on the projectile, general expressions for swerve are obtained in terms of basic vehicle parameters. These compact expressions are used to show that maximum swerve response for a fin-stabilized projectile is achieved when the force is applied near the nose of the projectile, whereas maximum swerve response for a spin-stabilized projectile is achieved when the force is applied near the base of the projectile. [ABSTRACT FROM AUTHOR]

An analysis of results of calculations and data of full-scale tests was conducted in the work, that confirmed a possibility of substantial increase of the ammunitions power owing to simple structural and technological modification of a bullet and cartridges as a whole, oriented to its application in regular arms. [ABSTRACT FROM AUTHOR]