Terminal Ballistics Research Articles

Measurement of bullet impact conditions using automated in-flight photography system

Abstract Knowledge of impact conditions is critical to evaluating the terminal impact performance of a projectile. For a small caliber bullet, in-flight velocity has been precisely measured for decades using detection screens, but accurately quantifying the orientation of the bullet on a target has been more challenging. This report introduces the Automated Small-Arms Photogrammetry (ASAP) analysis method used to measure, model, and predict the orientation of a small caliber bullet before reaching an impact surface. ASAP uses advanced hardware developed by Sydor Technologies to record a series of infrared digital photographs. Individual images (four orthogonal pairs) are processed using computer vision algorithms to quantify the orientation of the projectile and re-project its precise position and orientation into a three-dimensional muzzle-fixed coordinate system. An epicyclic motion model is fit to the measured data, and the epicyclic motion is extrapolated to the target location. Analysis results are fairly immediate and may be reviewed during testing. Prove-out demonstrations have shown that the impact-angle prediction capability is less than six hundredths of a degree for the 5.56 mm ball round tested. Keywords: Yaw, Terminal ballistics, Exterior ballistics, Test & evaluation, Computer vision, Image processing, Angle of attack

Deep indentation and terminal ballistics of polycarbonate

The penetration of rigid projectiles in polycarbonate (PC) targets is explored through deep indentation tests with conical-nosed indenters and ballistic penetration results for armor piercing 7.62mm projectiles. We found that the resistance to penetration in both sets of experiments is practically the same, which means that the rate sensitivity of PC does not play a significant role in its resistance to penetration. We account for this observation by including the pressure dependence of the elastic constants and the strength of PC in its constitutive equation, which we implemented in numerical simulations. This pressure-dependent constitutive relation resulted in good agreements between simulation results and experimental data for both penetration depths and residual velocities of armor piercing projectiles impacting PC targets.

Evaluation of numerical modelling application for the crash test planning of the catastrophic Flight Data Recorder

ABSTRACTCatastrophic Flight Data Recorders (FDRs), the so-called black boxes, belong to the on-board equipment, the task of which is not only to operate properly while recording selected parameters under all flight conditions but also to protect the recorded data against the loss in the aircraft crash conditions. The requirements related to catastrophic resistance of FDRs are defined in the European standard EuroCAE ED-112 and the Polish standard NO-16-A200:2015. One of the requirements includes the catastrophic recorder’s resistance to the acceleration overload of 3400 g. The compliance with the standard is checked during crash tests. In this paper, a procedure of planning and carrying out the mentioned tests for S2-3a-K protected unit of S2-3a catastrophic FDR manufactured by the Air Force Institute of Technology was described. It is an iterative procedure involving consecutive experimental tests and both analytical and numerical calculations. The experimental tests were performed using a DPZ-250 pneumatic gun. The testing probe was shot at the target of sand deposits of modified geometry and mass characteristics. Effectiveness of the developed procedure was shown by comparing the experimental results, namely recordings of the probe deceleration captured with a fast camera, with results of numerical simulation of the probe terminal ballistic.

Response of CMT Welded Aluminum AA5086-H111 to AA6061-T6 Plate with AA4043 Filler for Ballistic

Cold Metal Transfer (CMT) is a proven type of welding method using Metal Inert Gas (MIG). It is a welding technique which can be employed for marine fabrications too. Plates of AA5086-H111 and AA6061-T6 with AA4043 filler is welded by CMT. Parameters like current, voltage, arc length, shield gas pressure etc. are varied to obtain a continuous weld without any crack. Welded thin plates are subjected to a tensile test as per American Welding Society (AWS B4.0:2007) and thereafter impact loads are applied. The plates subjected to impact loads in the range of sub-ordinance level velocities, the feasibility of ordinance and ultra-ordinance can be scaled and compared. Responses and terminal ballistics limit are determined for plate thickness of 1.2mm and 3mm. Present work consists of simulation using Abaqus Software and experiments using Laboratory prepared gun. It was observed that, there was petaling in very thin plates and in some plates it was perforated by plugging for lower ballistic loads and thinner plates. The work gives new insights into the application of CMT in joining plates of different materials with varied thickness values. The material property of plates joined by this welding method was found to be new resource information to the permanent literature of material technology.

Methodology for experimental verification of steel armour impact modelling

We present a novel methodology to experimentally verify constitutive models and numerical algorithms used in terminal ballistics of small arms ammunition. The methodology comprises of the following elements: identification of material models in a set of independent tests, terminal ballistics testing of conditions covering the most important cases of bullet–target interactions, while providing enough data to assess the scatter of parameters measured in the experiments and to create a measure characterising deviation of modelling results from the experiments. To meet the objectives of this study, 7.62mm armour-piercing ammunition was used to perforate steel armour plates at ordnance velocity. Several parameters that characterise bullet velocity and path, plate deformation and ductility were measured and used as reference data for the verification of models. Relatively complex and simple constitutive and failure models implemented in the Finite Elements (FE) code LS DYNA were used. Finally, solid Lagrange and hybrid solid/Sooth Particles Hydrodynamics (SPH) discretisation methods with detailed models of the bullet and target are presented and different findings are compared with ballistic test results. The methodology shows a significant efficiency in the assessment of the adequacy of models. In this study, stress triaxiality and strain rate based models were found to give results in good agreement with experimental results, and several physical mechanisms are well predicted.

Ballistics and anatomical modelling - A review.

Ballistics is the study of a projectiles motion and can be broken down into four stages: internal, intermediate, external and terminal ballistics. The study of the effects a projectile has on a living tissue is referred to as wound ballistics and falls within terminal ballistics. To understand the effects a projectile has on living tissues the mechanisms of wounding need to be understood. These include the permanent and temporary cavities, energy, yawing, tumbling and fragmenting. Much ballistics research has been conducted including using cadavers, animal models and simulants such as ballistics ordnance gelatine. Further research is being conducted into developing anatomical, 3D, experimental and computational models. However, these models need to accurately represent the human body and its heterogeneous nature which involves understanding the biomechanical properties of the different tissues and organs. Further research is needed to accurately represent the human tissues with simulants and is slowly being conducted.

The <italic>in-situ</italic> measurement of the penetration trajectory in reinforced concrete target by grid measurement method

In order to study the terminal ballistics of a high-speed penetrator striking in the steel reinforced concrete target, a grid measurement method was developed in the present paper, which was composed of the grid cables, LED lamps, power and high-speed photography, etc. The grid cables were pre-embedded as multilayer with given space and arranged like the chess-board distribution along the steel rebars. When the projectile penetrated into concrete target, it might cut off the grid cable, which would truncate the corresponding circuit and turn off the corresponding LED lamps. The winking of LED lamps in each layer were recorded simultaneously by the high-speed photography. Given the distribution of the grid cables, the ballistic trace, velocity and DOP could be determined according to the winking of LED lamps. Based on the method, the variation of the projectile velocity and DOP were studied by experiments, which was validated by the empirical formula and direct measurement. It confirmed the effectiveness of the grid method.

Performance of primary repair on colon injuries sustained from low-versus high-energy projectiles

Among various reasons, colon injuries may be caused by low- or high-energy firearm bullets, with the latter producing a temporary cavitation phenomenon. The available treatment options include primary repair and two-stage management, but recent studies have shown that primary repair can be widely used with a high success rate. This paper investigates the differences in performance of primary repair on these two types of colon injuries. Two groups of patients who sustained colon injuries due to single gunshot wounds, were retrospectively categorized based on the type of bullet. Primary colon repair was performed in all patients selected based on the inclusion and exclusion criteria (Stone and Fabian's criteria). An almost absolute homogeneity was attained among the groups in terms of age, latent time before surgery, and four trauma indexes. Only one patient from the low-energy firearm projectile group (4%) developed a postsurgical complication versus nine patients (25.8%) from the high-energy group, showing statistically significant difference (p = 0.03). These nine patients experienced the following postsurgical complications: pneumonia, abscess, fistula, suture leakage, and one multiorgan failure with sepsis. Previous studies concluded that one-stage primary repair is the best treatment option for colon injuries. However, terminal ballistics testing determined the projectile's path through the body and revealed that low-energy projectiles caused considerably lesser damage than their high-energy counterparts. Primary colon repair must be performed definitely for low-energy short firearm injuries but very carefully for high-energy injuries. Given these findings, we suggest that the treatment option should be determined based not only on the bullet type alone but also on other clinical findings.

Deaths resulting from the use of firearms by police against motor vehicles: Study of cases in Porto, Portugal

The objective of this study was to investigate the terminal ballistics of police shootings in which the bullets went through any motor vehicle structure before fatally wounding the occupants. 6 cases that occurred in Porto district between 1998 and 2013 were studied. The firearms used were 7.65 mm (n = 1) or 9 mm (n = 3) calibre semi-automatic pistols and 9 mm calibre submachine guns (n = 2); the bullets were full metal jacket type. The metal jacket of the collected projectiles was totally or partially destroyed in 3 cases. It exhibited a deformed structure in all cases. The trajectories of the bullets in the vehicles were always more or less linear, even when initial impact was at an oblique angle. The entry holes in the victims' bodies were larger or much larger in size than the calibre of the bullets. They were located, with the exception of one of the cases, in the left half of the body. The trajectories in the victims' bodies were from front to back, in one case, and from back to front in all others. Exit wounds were only found in two cases. Death occurred immediately after the victim was shot only in one case, despite a vital structure has been hit in all cases. The cases studied support the idea that the use of firearms against vehicles with the sole intention of immobilisation entails uncontrollable danger to the lives of the occupants, and especially when done by police forces not specifically trained for that purpose. Therefore, such use of firearms should be avoided.

Improved Element Erosion Function for Concrete-Like Materials with the SPH Method

The subject of the paper is a description of a simple test from the field of terminal ballistics and the handling of issues arising during its simulation using the numerical techniques of the finite element method. With regard to the possible excessive reshaping of the finite element mesh there is a danger that problems will arise such as the locking of elements or the appearance of negative volumes. It is often necessary to introduce numerical extensions so that the simulations can be carried out at all. When examining local damage to structures, such as the penetration of the outer shell or its perforation, it is almost essential to introduce the numerical erosion of elements into the simulations. However, when using numerical erosion, the dissipation of matter and energy from the computational model occurs in the mathematical background to the calculation. It is a phenomenon which can reveal itself in the final result when a discrepancy appears between the simulations and the experiments. This issue can be solved by transforming the eroded elements into smoothed particle hydrodynamics particles. These newly created particles can then assume the characteristics of the original elements and preserve the matter and energy of the numerical model.

The ballistic performance of the bombard Mons Meg

Abstract The bombard Mons Meg, located in Edinburgh Castle, with a diameter of 19 inches (48 cm), was one of the largest calibre cannons ever built. Constructed in 1449 and presented to King James II of Scotland in 1454, Mons Meg was used in both military and ceremonial roles in Scotland until its barrel burst in 1680. This paper examines the history, internal, external and terminal ballistics of the cannon and its shot. The likely muzzle velocity was estimated by varying the propellant type and the cannon profile was investigated to identify weak spots in the design that may have led to its failure. Using the muzzle velocity calculated from the internal ballistics, simulations were performed with granite and sandstone shot for varying launch angle and ground temperature. The likely trajectory and range of the cannonballs are described. The internal and external ballistics informed the initial conditions of the terminal ballistic impact scenarios. The performance of the cannonball against both period and modern targets, in the form of a pseudo-castle wall and a monolithic concrete target, respectively, were simulated and are presented and discussed.

Consistent constitutive modeling of metallic target penetration using empirical, analytical, and numerical penetration models

Abstract Historically, there has been little correlation between the material properties used in (1) empirical formulae, (2) analytical formulations, and (3) numerical models. The various regressions and models may each provide excellent agreement for the depth of penetration into semi-infinite targets. But the input parameters for the empirically based procedures may have little in common with either the analytical model or the numerical model. This paper builds on previous work by Riegel and Anderson (2014) to show how the Effective Flow Stress (EFS) strength model, based on empirical data, can be used as the average flow stress in the analytical Walker–Anderson Penetration model (WAPEN) (Anderson and Walker, 1991) and how the same value may be utilized as an effective von Mises yield strength in numerical hydrocode simulations to predict the depth of penetration for eroding projectiles at impact velocities in the mechanical response regime of the materials. The method has the benefit of allowing the three techniques (empirical, analytical, and numerical) to work in tandem. The empirical method can be used for many shot line calculations, but more advanced analytical or numerical models can be employed when necessary to address specific geometries such as edge effects or layering that are not treated by the simpler methods. Developing complete constitutive relationships for a material can be costly. If the only concern is depth of penetration, such a level of detail may not be required. The effective flow stress can be determined from a small set of depth of penetration experiments in many cases, especially for long penetrators such as the L/D = 10 ones considered here, making it a very practical approach. In the process of performing this effort, the authors considered numerical simulations by other researchers based on the same set of experimental data that the authors used for their empirical and analytical assessment. The goals were to establish a baseline with a full constitutive model and to determine if the EFS could be estimated from a standardized constitutive model. We were unable to accomplish this. Several papers detailing simulations using the Johnson–Cook (JC) constitutive model were located and used as a basis for comparison. The authors were somewhat surprised to find that the JC parameters employed in those studies were not actually developed for the target materials that were evaluated experimentally. More disconcerting was the fact that a number of different sets of JC parameters were published for presumably the same material. Although not intended to be a critique of the JC model, this research raises a serious concern regarding the manner in which the model has been applied to terminal ballistics problems. The details of the study are included in this paper because the authors believe it helps put the discussion of EFS into proper context.

Machine learning methods for predicting the outcome of hypervelocity impact events

The outcome of projectile impacts on spaced aluminium armour (i.e. Whipple shield) at hypervelocity is traditionally predicted by semi-analytical equations known as ballistic limit equations (BLEs). For spherical aluminium projectiles impacting aluminium Whipple shields, the state-of-the-art BLE has been found to correctly reproduce the perforation/non-perforation result of approximately 75% of tests contained within a database with over 1100 entries. For such high-dimensional, complex problems, machine learning methods may be a superior approach over such semi-analytical/empirical methods. Towards this end an artificial neural network (ANN) and support vector machine (SVM) have been developed to better classify the outcome of hypervelocity impact events on aluminium Whipple shields. The ANN was found to correctly reproduce the perforation/non-perforation result of over 93% of the training exemplars, generalizing at 92.2% when applied with an optimized architecture. The SVM was not able to reach comparable levels of generalization error as the ANN, peaking at 83% after the removal of a small number of test exemplars which induced conflict within the SVM pattern recognition. Although providing a significant improvement in predictive accuracy over the conventional BLE, the performance of both the ANN and SVM were highly sensitive to the population density of the parameter space described by the training data. Within highly populated regions the qualitative trends of the machines are demonstrated to accurately identify patterns associated with projectile fragmentation and melting, while in sparsely populated regions the accuracy significantly decreases and the qualitative trends can become nonsensical. Further improvements in accuracy are limited by the inhomogeneous sampling of the parameter space defined by the current impact test database—a problem expected to be typical of any terminal ballistics problem in which the cost of performing experiments limits their scope to, for example, materials and geometries of interest, impact conditions expected during operation, and a limited range about the perforation threshold (i.e. ballistic limit). A combined novelty-detecting neural net and hetero-associate neural net have been applied to iteratively improve the performance of the ANN without requiring an inordinate number of additional tests. This process, referred to as bootstrapping, has been successfully demonstrated through the design of ‘optimized’ Whipple shields for given impact conditions, hypervelocity impact testing of the designed shields, and re-training of the critic net to incorporate the results of the new impact tests.

Research of Multidisciplinary Optimization of ISFS Based on Collaborative Optimization

Individual-soldier firepower system includes several subsystems, and the relationships of competition and cou- pling exist in each subsystem. In order to obtain the optimal performance of the entire system, the multidisciplinary opti- mization is employed in this paper. The recoil force is taken as the objective function, and the performances of weapon dynamics, internal ballistics, external ballistics and terminal effects are taken as the subsystems. To establish the multidis- ciplinary optimization model of individual-soldier firepower system, the collaborative optimization method is adopted. And then, for optimizing the complicated system globally, the parallel, global and local optimization methods, response surface methodology, and subsystem models are used to carry out the optimization computation on the basis of consider- ing the coupling relationships of each sub-discipline. The computational results shown that, the multidisciplinary optimi- zation of individual-soldier firepower system can not only ensure the performances of internal ballistics, external ballistics and terminal ballistics, but also further optimize the recoil force.

Experiments and modeling of ballistic penetration using an energy failure criterion

One of the most intricate problems in terminal ballistics is the physics underlying penetration and perforation. Several penetration modes are well identified, such as petalling, plugging, spall failure and fragmentation (Sedgwick, 1968). In most cases, the final target failure will combine those modes. Some of the failure modes can be due to brittle material behavior, but penetration of ductile targets by blunt projectiles, involving plugging in particular, is caused by excessive localized plasticity, with emphasis on adiabatic shear banding (ASB).Among the theories regarding the onset of ASB, new evidence was recently brought by Rittel et al. (2006), according to whom shear bands initiate as a result of dynamic recrystallization (DRX), a local softening mechanism driven by the stored energy of cold work. As such, ASB formation results from microstructural transformations, rather than from thermal softening. In our previous work (Dolinski et al., 2010), a failure criterion based on plastic strain energy density was presented and applied to model four different classical examples of dynamic failure involving ASB formation. According to this criterion, a material point starts to fail when the total plastic strain energy density reaches a critical value. Thereafter, the strength of the element decreases gradually to zero to mimic the actual material mechanical behavior.The goal of this paper is to present a new combined experimental–numerical study of ballistic penetration and perforation, using the above-mentioned failure criterion. Careful experiments are carried out using a single combination of AISI 4340 FSP projectiles and 25[mm] thick RHA steel plates, while the impact velocity, and hence the imparted damage, are systematically varied. We show that our failure model, which includes only one adjustable parameter in this present work, can faithfully reproduce each of the experiments without any further adjustment.Moreover, it is shown that the most common failure criterion based on a critical strain is simply inadequate to reproduce the results, due to the linear nature of the damage evolution. The advantages of the energy-based failure criterion are discussed in detail.

The Use of a Railgun Facility for Dynamic Fracture of Brittle Materials

Linear electromagnetic acceleration has a wide range of applications. Among them are applications in the field of materials science, where relatively small, inexpensive systems can be of high value. For instance, it was shown recently at the French-German Institute of Saint Louis, France, that the symmetric Taylor test-a method to investigate the deformation behavior of specimens at high deformation rates-can be realized with higher precision than attainable with other acceleration methods using a railgun with velocity control. In this paper, we present another example for an application of a railgun in the field of materials science, namely, the study of impact phenomena and terminal ballistics. One of the major advantages of railgun technology is that the acceleration profile can be well defined at velocity ranges from very low speeds (<;10 m/s) up to more than 2000 m/s-for one and the same launcher. Moreover, the geometry of a railgun projectile can be round, rectangular or, as in the case discussed here, hexagonal. Finally, electromagnetic acceleration does not require the use of propellants, which in the case of impact experiments could lead to complications-at least for the experimental application presented. The quest is to study the ejecta field of fractured brittle materials at moderate impact velocities (<;500 m/s). It transpires that a railgun can be a valuable tool for such investigations. Using high-speed cameras and novel data processing methods ejecta distribution-velocity relations are explored. Our contribution describes the experimental setup used and will introduce some of the major results obtained so far.

Experiments and modeling of ballistic penetration using an energy failure criterion

One of the most intricate problems in terminal ballistics is the physics underlying penetration and perforation. Several penetration modes are well identified, such as petalling, plugging, spall failure and fragmentation (Sedgwick, 1968). In most cases, the final target failure will combine those modes. Some of the failure modes can be due to brittle material behavior, but penetration of ductile targets by blunt projectiles, involving plugging in particular, is caused by excessive localized plasticity, with emphasis on adiabatic shear banding (ASB). Among the theories regarding the onset of ASB, new evidence was recently brought by Rittel et al. (2006), according to whom shear bands initiate as a result of dynamic recrystallization (DRX), a local softening mechanism driven by the stored energy of cold work. As such, ASB formation results from microstructural transformations, rather than from thermal softening. In our previous work (Dolinski et al., 2010), a failure criterion based on plastic strain energy density was presented and applied to model four different classical examples of dynamic failure involving ASB formation. According to this criterion, a material point starts to fail when the total plastic strain energy density reaches a critical value. Thereafter, the strength of the element decreases gradually to zero to mimic the actual material mechanical behavior. The goal of this paper is to present a new combined experimental-numerical study of ballistic penetration and perforation, using the above-mentioned failure criterion. Careful experiments are carried out using a single combination of AISI 4340 FSP projectiles and 25[mm] thick RHA steel plates, while the impact velocity, and hence the imparted damage, are systematically varied. We show that our failure model, which includes only one adjustable parameter in this present work, can faithfully reproduce each of the experiments without any further adjustment. Moreover, it is shown that the most common failure criterion based on a critical strain is simply inadequate to reproduce the results, due to the linear nature of the damage evolution. The advantages of the energy-based failure criterion are discussed in detail.

High-Velocity Impact of Encased Al/PTFE Projectiles on Structural Aluminum Armor

In support of the U.S. Army's science and advanced technology objective in hypervelocity penetration mechanics, the Army Research Laboratory has been studying the terminal ballistics of conventional and non-conventional high-velocity kinetic energy projectiles against urban, light-armor and heavy-armor targets. The purpose is to identify and analyze both mechanisms and concepts to effectively defeat a range of targets with inert payloads using the elevated impact velocities available from future delivery systems. To this end, a series of experiments has been performed launching low-aspect-ratio aluminum and steel cylindrical projectiles, aluminum conical projectiles, and encased reactive material projectiles, with nominal masses between 200 and 240-gm, striking finite aluminum armor at nominal velocities of 2100 m/s to observe crater and spall formation and to determine the damage capacity of the debris.

Experimental Analysis of Visco-Plastic Properties of the Aluminium and Tungsten Alloys by Means of Hopkinson Bars Technique

The main aim of studies on dynamic behaviour of construction materials at high strain rates is to determine the variation of mechanical properties (strength, plasticity) as a function of the strain rate and temperature. On the basis of results of dynamic tests on the properties of constructional materials the constitutive models are formulated to create numerical codes applied to solve constructional problems with computer simulation methods. In the case of military applications connected with the phenomena of gunshot and terminal ballistics it's particularly important to develop a model of strength and armour penetration with KE projectile founded on reliable results of dynamic experiments and constituting the base for further analyses and optimization of projectile designs in order to achieve required penetration depth. Static and dynamic results of strength investigations of the EN AW-7012 aluminium alloy (sabot) and tungsten alloy (penetrator) are discussed in this paper. Static testing was carried out with the INSTRON testing machine. Dynamic tests have been conducted using the split Hopkinson pressure bars technique at strain rates up to 1,2·104 s-1 (for aluminium alloy) and 6·103 s-1 (for tungsten alloy).

English

The rail track rocket sled (RTRS) national test facility at Terminal Ballistics Research Laboratory (TBRL) has been established to provide simulated flight environment for carrying out aero dynamic studies, terminal studies and kinematic studies of variety of test articles. The sled velocity is a critical parameter in evaluation trials. This velocity is also used to ensure that the maximum speed and allowable g loading does not exceed the value which the test article will experience under free flight in air1. Overseas, the facilities have been set up to attain velocities ranging from sub-sonic to hypersonic2. The rocket sled at TBRL can be presently accelerated to travel along the rail track at velocities up to 500 m/s and capability is being built to increase velocity beyond 500 m/s. Signals acquired from existing magneto-inductive arrangement have been analysed in the present work. The experiments indicate that with increase in velocity the rate of change of flux increases, the amplitude of induced emf also increases but terminal voltage decreases and shape of the acquired pulse gets distorted. The parameters of magneto-inductive pick up have been modified in such a way that there is improvement in amplitude and shape of the received pulse with increase in velocity. The improved signals have been analysed and simulation results validated with feasible experiments. This paper also discusses issues, challenges and proposes recommendations in improving the sensor for measurement of velocity beyond Mach 1.5. It has been found that it is prudent to reduce the inductance by reducing the number of turns and changing the core from soft iron core to air core which will improve the response of inductive pick up coil at high velocity. Defence Science Journal, 2014, 64(2), pp. 143-151. DOI: http://dx.doi.org/10.14429/dsj.64.5034