29th International Symposium on Ballistics
The Ballistic Performance of the Bombard Mons Meg
The bombard Mons Meg was used in both military and ceremonial roles in Scotland until its barrel burst in 1680. This paper examines the history, and 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 provided initial conditions for the terminal ballistic impact scenarios. The performance of the cannonball against both period and modern targets are presented and discussed. The full paper will be published in Defence Technology Volume 12 Issue 2.
IAN LEWTAS, ADAM WALLIS, IAN CULLIS, CLIVE WOODLEY
Some Features and Applications of Ballistic Science and Technology in China
China continues a broad spectrum of research on Ballistics to provide insight and resolution of major technical challenges. The current situation and development of Ballistics of China in recent years are presented as follows: (1) Weapon launching theory and technology. In recent years, some important achievements have been made in the field of new launching technologies, such as electrothermal-chemical (ETC) gun and electromagnetic (EM) railgun in China. At present, it is viable for the ETC gun to be applied in the engineering field. And the prototype system for demonstrating the focused technology has been designed, manufactured and tested for EM railgun. Small and medium caliber spin tube guns have been produced, and the investigations on the weapon safety and launching dynamics have also been conducted. (2) Theory and technology of propulsion and extended range for projectiles and rockets. The compound extended range of the howitzer and tactical rocket weapons have been increased in a great extent. Some investigations have been made in the fields of high energy propellant, shell material of high intensity and light weight engines, aerodynamic drag reduction, etc. (3) Precision theory and technology of projectiles and rockets. In recent years, many kinds of guided and precision technologies have emerged out of laboratory research, such as, the terminal sensitive, trajectory correction, guided and terminal guided, and simplified-control, etc., which greatly enhanced the probability of hitting target. (4) Theory and technology of high efficient terminal lethality. The penetration performance of nano-grained composite material of penetrator has been improved significantly. The passive mass of the penetrator has been reduced by the means of magnesium matrix composites. The damage power of ammunition has been enhanced with the application of composite explosives. Some breakthroughs have been achieved in the formation and transition mechanism of multi-damage models, explosion control technologies. The penetrating law of multilayer advanced composite armor and stability of explosive reactive armor have been studied, the mechanism of high-velocity penetration and the evaluation method have also been proposed. Most significantly, China has elevated its emphasis from ballistic science and technology development to the fires application. In concert with the recent efforts on precision, longrange, high-efficient lethality of fires, it is anticipated that the pull of these applications will enable even greater advances in ballistics science and technology.
Initial Analysis on the Influence of Heating up of Subcalibre Projectiles Penetrator to Strength Properties
In this paper, results of the numerical analysis of the heating process of a penetrator are presented, as well as its influence on strength properties. Results of calculations show distributions of temperatures in particular elements and areas of the penetrator. Results of dynamic tests of the tungsten alloys specimens are presented (being the main structural material of the penetrator), which were carried out on the modified Hopkinson’s split bar at 300°C temperature of specimens.
Innovative Course Correction Devices: MANEGE Program
The field of flow control has witnessed an exponential growth in the last twenty past years mainly for aeronautical applications. However, few studies were dedicated to projectiles. Thanks to the support of the French MoD, the MANEGE applied research program has been launched in 2011. This paper presents a synthesis of works and results achieved through a close collaboration between ONERA, ISL and NEXTER Munitions. The primary objective was the acquisition of aeroballistics technological skills to support upcoming applications. For aero and spin-stabilized projectiles implementations, the investigations were focused on potential mechanical and fluidic actuators used in passive or active ways. Relevant actuators must present significant trajectory correction ability. Aeroballistics characterizations have been based on extensive numerical simulations supplemented with wind tunnel and flight tests. The MANEGE program will be concluded in 2016 by a real firing demonstration of a mechanical actuator acting on artillery shell deviation.
ERIC CARETTE, MICKAËL ZEIDLER, PASCAL DENIS, RÉMI THÉPOT, ERIC GARNIER, PIERRE WEY, BAS
Study on the Mechanism of Boundary Layer Induced Flow Control Based on Low Temperature Plasma
Dielectric barrier surface discharge plasma active drive control technology can significantly improve the aerodynamic performance, has become research hot topic at home and abroad. Lattice Boltzmann method (LBM) as a kind of mesoscopic calculation method, can more effectively reflect the mechanism of plasma near the boundary layer control air movement. A multi-components LBM for weakly ionized plasma is employed in our simulation. A term to describe the plasma ionization, recombination and charge attachment has been added in the equations. An induced flow by surface dielectric barrier discharge plasma actuator is simulated. The distributions of electrons, positive ions, and negative ions near the solid wall were obtained. It was found that the charge mainly distribute on the on the dielectric surface upper the embedded electrode. The flow field and velocity profile near the surface was obtained. The dynamic pressure distribution of the boundary layer movement driven by the surface discharge plasma under atmospheric pressure are measured, the velocity distribution are obtained. It was found the plasma actuators can significantly increase the velocity of an induced flow at the boundary layer.
Large-Eddy Simulation of a Turbulent Coanda Jet in an External Flow
This work follows up a previous paper presented at the 28th International Symposium of Ballistics about the fluidic control of a 155 mm spin-stabilized projectile using the Coanda effect. A continuous jet is used to blow tangentially over a convex surface at the projectile aft end. Due to the balance between centrifugal forces and the radial pressure gradient, the jet attaches to the circular wall and generates significant aerodynamic forces. A large-eddy simulation of a highly simplified configuration is performed in order to acquire a better understanding of the physical mechanisms induced by the use of the Coanda jet. First, comparisons are performed with a similar work on a circulation control wing in order to validate the simulation. Then, the main effort focuses on the identification of existing vortices over the convex surface. Their natural frequencies and characteristic lengths are investigated through a spectral analysis.
A Guidance Law Based on Correcting Velocity Direction Continuously in Finite Time
Taking the limited control authority and guidance information of a gun-launched guided projectile into account, a novel three-dimensional terminal guidance law based on the combination of the correction of the velocity direction via impact point prediction and continuous distribution of acceleration command is proposed. The deviations between the impact point of the projectile and the target are predicted based on the series solutions of the nonlinear ballistic equations. According to the deviations, a nonlinear method to calculate the direction angles corrections of the current speed is addressed. Design the remaining flight time as the correction time. The acceleration correction formulas are established through sharing the direction angles corrections of the current speed into the whole remaining guided flight to reduce the possibility of command saturation. By predicting the impact point and distributing acceleration corrections continuously to shape the trajectory in real time. The simulation results show that the proposed guidance law is feasible and effective, and provides the performances of higher precision and less requirements of control authority and greater damage effects on account of the larger impact angle, compared with the proportional navigation law, which provides a reference for the application of the guided projectile.
Trajectory Prediction and Correction Methods Without Meteorological Information
Drag-ring correction schedule for one dimension trajectory correction projectile, with the characteristics of simple control actuator, reliable action, low cost, and greatly improving the ground vertical intensity etc., has been applied on the shells and achieved good application effect in recent years. Two aspects are extremely important in the implement of this projectile: First, the corresponding firing elements (i.e., the elevation angle) should ensure that the flight distance of uncontrolled projectile is greater than or equal to the desired distance. Second, real time identification of the characteristic parameters of the projectile should be performed based on the measurements of a segment of flight data. However, high altitude meteorological conditions cannot be obtained in practice, which makes it extremely difficult to ensure that the average impact point center of uncontrolled projectiles is consistent with the generalized target, and brings a great impact for the accuracy of trajectory prediction and the trajectory correction effect. For those problems, in this paper the corresponding equivalent wind parameters are obtained based on a few rounds of the impact point data of the uncontrolled shells test-fired in advance, to ensure the validity of the setting firing elements and trajectory prediction. Furthermore, the number of test-fired and the different methods and their effects of getting the equivalent wind parameters are analyzed. The research content reported in this paper is able to provide useful guide for the application of the trajectory correction technique for the one dimensional trajectory correction projectile.
Study on Ballistic Optimization for Extended Range Guided Projectile
Long-range guided Projectile are characteristic of large flying area, further round and ordinate high point. In favor of the cope of high-low height aerodynamic parameter, each inter-channel remain nonlinear coupling in the course of movement. The design method of classical control theory is no longer true of long-range guidance shell control system. For the purpose of exert long-range guidance shell optimum performance, the text is base of exterior ballistics theory, on basis of the analysis trajectory characteristic of long-range guidance projectile, adopt advanced design means of control system, to design and emulation count the ballistic optimize problem parting from the without control segment and control segment two versus, the versus is proven that it has come to the best efficiency to control shell flying position to long distance precision attack.
Improved Theory of Generalized Meteo-ballistic Weighting Factor Functions and Their Use
It follows from the analysis of artillery fire errors that approximately two-thirds of the inaccuracy of indirect artillery fire is caused by inaccuracies in the determination of the meteo parameters included in fire error budget model. Trajectories calculated under non-standard conditions are considered to be perturbed. The tools utilized for the analysis of perturbed trajectories are weighting factor functions (WFFs) which are a special kind of sensitivity functions. WFFs are used for calculation of meteo ballistic elements μB (ballistic wind wB, density ÏB, virtual temperature τB, pressure pB) as well. We have found that the existing theory of WFFs calculation has several significant shortcomings. The aim of the article is to present a new, improved theory of generalized WFFs that eliminates the deficiencies found. Using this theory will improve methods for designing firing tables, fire control systems algorithms, and meteo message generation algorithms.
The Evaluation Model of the Moving Target Firing Effectiveness of the Laser Terminal Guided Projectile
The laser terminal guidance projectile is a kind of precision guided weapon for artillery. From the point of view of the terminal guidance projectile to the target firing, the characteristics of the movement target is set out. The firing conditions of the target fired by the terminal guidance projectile are studied. On this basis, considering the firing error of the launching terminal guidance projectile, the error of the elements, distribution error and guidance error are analyzed. And the mathematical model of fire efficiency is established.
Technique to Eliminate Angle of Attack in Ballistic Testing
In the ballistic testing of penetrators, the angle of attack is the most critical parameter affecting survival and penetration. DE Technologies, Inc., required gun-launched testing of a projectile with minimum angle of attack. Mr. Lundgren of HA Consulting suggested a technique to remove the angle of attack before target impact. A stack of plywood placed ahead of the target will separate the sabot from the projectile and reduce any angle of attack. Computer simulations were done with fast-running empirical computer codes SAMPLL and PENCRV3D as well as an explicit finite element code, EPIC. Powder gun experiments at impact velocities from 300 to 800 m/s achieved projectile angles of attack less than 0.5°.
On Resonance of Dual-Spin-Stabilized Projectiles Equipped with Canards
To improve the strike precision of conventional spin-stabilized projectiles which are stockpiled in large amount at present over the world, a class of dual-spin-stabilized projectiles equipped with canards is investigated. This article presents a 7 Degree-of- Freedom (7-DOF) flight dynamic model and an accurate dynamic model of angle of attack (AOA). By simplifying and solving the model of AOA, the problem of resonance for this special spin-stabilized projectile is discussed. Simulation results indicate that the resonance may occur under the periodical action of canards, which is detrimental to flight stability. The effect of a variety of factors, such as canard deflection angles, canards placements, and the ratio of axial moment of inertia of the two bodies, on the amplitude of respond AOA is also studied through numerical simulation. All the work is useful for further research.
Study on Three-Dimensional Contour Measurement Technology for Projectile
In ballistics, through measuring the three-dimensional surface of the bullet after launching, the degree of ablation and other effects on the surface of the bullet can be measured. The 3D reconstruction device consists of: a device to measure the design and function of the fringe projectile, a synchronous illumination source, an imaging camera and a time sequence controller. These items collectively will analyze the effect of Fourier contour transformations on the projectile. To ensure the integrity of these findings, static and dynamic tests will be performed to ensure the accuracy of the system. The experiment results have shown that the system is able to complete the three- dimensional reconstruction of a flying body. In the examination of ballistics, this system has broad applications.
Aerodynamic Shape Optimization for a Hollow Projectile Based on Blind Kriging
The design for an anti-aircraft hollow projectile, provided with ample power and precision, to minimize the flight time of a given slant distance is of vital importance. With the purpose of obtaining the optimal aerodynamic shape with the shortest possible spent time of a given slant distance, combined with the application of UG, ICEM CFD and FLUENT etc softwares and script program, the corresponding drag coefficients of different aerodynamic shapes under the condition of Ma=2.5~4.0 and attack angle =0º have been obtained, and Blind Kriging surrogate model is established for the drag coefficient. By use of sequential quadratic programming method, based on point mass trajectory model, the aerodynamic shape has been optimized to minimize the flight time of some given slant distances, and the optimal aerodynamic shape has been obtained. The numerical optimal method which is proposed in this paper for optimizing the hollow projectile can provide important guidance for relative engineering application and investigations.
Characteristics of the Fuzes Make Them Less Sensitive on the External Fators Action
The article discusses the issues associated with decreased sensitivity of the fuzes to the effects of random external factors that could cause their explosion. It presents an analysis of the characteristics of the fuzes fire chain in the currently used artillery fuzes, as well as the directions of work aiming at developing the structure of new, safer to use and high performance fuzes, and their potential application in insensitive ammunition. The article also shows selected examples of new designs that increase the resilience of the fuzes to the effects of dangerous external factors.
JACEK BORKOWSKI, BOGDAN KRYSINSKI, RADOSLAW WARCHOL
BALCO is a six- and seven-degree-of-freedom trajectory simulation program based on the mathematical model defined by the NATO Standardization Recommendation 4618. The primary goal of BALCO is to compute high-fidelity trajectories for both conventional and precision-guided projectiles. The 6-DoF model is used to describe the motion of single rigid bodies. The 7-DoF model allows the description of a projectile which consists of two coaxial rigid bodies that can spin independently. Actuators such as isolated control surfaces, thrusters or internal roll control devices can optionally be attached to the rigid body. Controlling the state of these actuators offers a control authority on the trajectory. The verification of the BALCO results by comparison with reference codes is in progress. After the verification process, BALCO will be released as NATO Technical Shareable Software.
DANIEL CORRIVEAU, THOMAS A. SAITZ, WIM DE RUIJTER, PETER STROMBACK
Selected Aspects of Small Calibre Pistol Ammunition Ballistics Statistical Analysis for Determining the Range Performance of
Requirements of modern battlefield forces usage of new, better, types of pistol ammunition. It is mainly caused by insufficient penetration capabilities and firing range of traditional 9 mm Parabellum ammunition. Also in close combat there is need for quick aiming, which is strongly connected to low recoil and controllability of a weapon. Because of those problems NATO countries started to develop new types of pistol ammunition to supersede 9 mm Parabellum ammunition in military use. Such works was also taken in early 70’s to exchange 9 mm Makarov ammunition in Soviet Union. Sole purpose of this article is to compare some internal and external ballistic parameters for different projectile types of 4,6x30 mm and 5,7x28 mm ammunition and additionally, for informative purposes, Soviet 5,45x18 mm ammunition.
155 mm MKE MOD274 HEER/Base Bleed ammunition having 39 km range at sea level can be used with NATO 52 caliber Weapon Systems. During the preparation of firing control input / tabular firing table of the projectile for T-155 Panter and T-155 Fırtına, intensive data collection activities had been carried out. As well as the data that providing information about the flight characteristics of the ammunition was obtained and used to form the firing tables, those data can be used in different ways by utilizing the statistical data mining techniques. Structure of the study; Interrelated groups have been determined by using statistical methods in which muzzle velocities and range performances of two different propellant weight (5th and 6th modules/zones), two different elevation of the gun and two different weapon has been taken into consideration for the projectiles having similar weight, center of gravity and moment of inertia. Hypothesis testing and multiple linear regulation models were used to evaluate the data and find the optimum model by using 155 mm MKE MOD274 HEER/Base Bleed ammunition test data. For determination of the "range" it is apparent that there is an important role of the "muzzle velocity" and "base bleed unit" variables. However, a model describing the structure of the relationship between these variables is not very common. This study has established a new model for the 155 mm MKE MOD274 HEER/Base Bleed ammunition by linear regression analysis.
Investigations on the Flow Characteristics of Micro Vanes of a Supersonic Spinning Projectile
Studies have shown that micro-wedge vortex generators (MVG) can effectively control the flow separation of supersonic boundary layer. In order to improve the flight stability of spinning projectile, the original standard 155mm projectile was taken as the example, and micro vanes were mounted at the projectile shoulder to investigate the separation control on the aerodynamic characteristics of the projectile. Numerical simulations were performed with the use of DES method for the flow fields of the projectile with and without micro vanes, the characteristics of the boundary layer structures and aerodynamic data for above two cases have been compared and discussed. Numerical results show that the micro vanes can inhibit fluid separation on the projectile surface, improve its flight stability and firing dispersion. Our results can provide important guidance for the improvement of supersonic projectiles.
ZHI-HUA CHEN, ZHEN-GUI HUANG, JIAN-GUO GAO, QIANG ZHAO
Fragments Safety Distances from Different Sources
Fragments produced in a high explosive event are a danger to personnel and materials. In many cases, the use of a classical physics formula for flight trajectory and range is not sufficient for safety distance evaluation. The uncertainty in fragment velocity, energy, projection angle, spray density and other engineering parameters, leads to a variety of possible results. In this work, a new cumulative-empirical approach is applied. Different sources based on standard and tailor-made munitions were compared. A conservative approach based on fragments cut-off velocity was formulized. A mathematical model for minimal safety distance evaluation is presented. The model takes into account the fragment's main characteristics, such as initial fragment velocity and case thickness. The model presented allows its application in a wide range of cases, especially when warhead parameters are uncertain.
Projectile Orientation Measurement During Flight and Just Before Impact
The angle between the line-of-fire and the rotation axis of a projectile is called the yaw angle. For fin and spin stabilized projectiles the yaw angle changes continuously during flight. Normally the yaw of a projectile is measured by orthogonal flash imaging of the projectile. However, this method provides only the yaw at a certain position, often at a certain distance from the target. To better establish the yaw just before impact, two methods will be presented and discussed: a continuous yaw measuring technique and a technique using a small V-shaped mirror close to the target impact position. A projectile can be illuminated during its flight using a laser beam directed from the target into the barrel using mirrors. By polishing the tip of the projectile the tip will reflect the laser light back towards the target. A light screen at the target position is used to project this reflection from the projectile tip. Using a high speed camera the position of this spot on the screen is recorded. Together with the known position of the projectile versus time, this enables the total yaw of the projectile to be measured continuously during its flight. Another method uses a high speed camera in combination with a V-shaped mirror placed just in front of the target. The total yaw can be calculated from the two (orthogonal) yaw-components. Examples of both yaw measuring techniques will be presented and discussed.
Stewart Platform as a Tool to Study the Stabilization of Aiming Line of Cannon and Line of Sight of Tracking Head
This paper relates to the integration of main elements included in the new Polish 35 mm naval weapon system with a fire control system and presents a method to design and execute a subsystem used to stabilize the aiming line of 35 mm cannon and the line of sight of an optoelectronic tracking head. For this purpose, dynamic tests of a weapon system have been carried on a special test stand – so called Stewart platform (the term “six-axisâ€ platform is also used). Devices placed on the top plate (i.e. main elements of naval weapon system) can be moved in the six degrees of freedom in which it is possible for a freelysuspended body to move. These are the three linear movements x, y, z (lateral, longitudinal, and vertical), and the three rotations pitch, roll, and yaw. The platform allows for examination of objects weighing up to 12 000 kg. The study and analysis of experimental results have contributed to a full integration of all components with the fire control system. The obtained results allowed for fast and effective implementation of the complete process of design, verification, and optimization of automated artillery system in industrial conditions. The obtained results will be verified in the course of maritime research.
Investigation Into the Impact of Integral Suppressor Configurations on the Pressure Levels within the Suppressor
This paper reports on an experimental investigation supported by basic modeling in to the performance of an integral suppressor on a low power firearm. A model was developed to determine the pressure within a suppressor chamber using iterative empirical calculations of the gas properties and flow within the system. The design of a reconfigurable suppressor chamber has been undertaken allowing suppressor chamber volume to be varied through the use of baffles. Pressure transducers were used to determine the pressure within the suppressor chamber for a series of firings. The results of the firings with different configurations within the suppressor are presented allowing trends to be established. The modeling and experimental results show an increase in suppressor chamber volume results in a reduction of recorded pressure within the suppressor chamber.
A Perfect Alignment Method of SINS/GPS in High-Dynamic Condition
Aiming at the problem that the navigation system of guided projectile will work after launch and the initial parameters of system will be determined on the condition of high speed and high dynamic, a new alignment method is proposed. The process of alignment is divided into two parts. In coarse alignment stage, proposes an estimator for the initial alignment of a strapdown inertial attitude reference system using IMU measurements with GPS aiding for moving-base alignment. The formulas of the coarse alignment method were derived which could solve the attitude of the flight by specific force equation using the velocity measured by GPS and specific force measured IMU. And then, in fine alignment stage, using small angle error model and Kalman Fliter based on UT transform to estimate and correct the navigation error. The performance is compared by a simulation system, which the precision is verified through computer simulation. Results show that this method has a good performance in accuracy.
Flight Trajectory Simulation of Ballistic Projectile
In view of exterior ballistics and flight principle, a full six degree-of-freedom rigid-projectile model is employed. The computational flight analysis takes into consideration the Earth’s rotation, Magnus and the wind effect. Moreover, the standard atmospheric model that simulates the air density and sound speed is presented. During the trajectory computation, the aerodynamics variations are calculated by means of variable aerodynamic coefficients. The RUNGE-KUTTA method is obtained for the numerical integration. The simulation results show some differences in the projectile flight trajectory after taking into consideration both of the wind and Earth’s rotation effect. The wind mainly affects the cross range and the Earth’s rotation mainly on the deflection angle, making the flight trajectory simulation more accurate. In addition, an investigation on the range extension capability using the rocket assist is presented.
Research on Influence Factors of Trajectory Correction Interval for Cross Canard Configuration
Correcting law is an important component for two-dimensional trajectory correction technology of spin-stabilized projectile, and it is a key issue to acquire the ideal circular error probability (CEP) of impact points by reasonable correction interval. This paper focuses on the influence factors to determine the correction interval, correction interval determining method based on transient duration of ballistic dynamic process is proposed. The optimum correction interval can be obtained by comprehensive consideration of initial launch parameters, dynamic transient duration and on-board electronics response time. Monte Carlo experiments are performed on square-crossing fixed-cant canard configuration of 155mm spin-stabilized projectile to verify the proposed approach.
XUDONG LIU, RUPENG LI, YONGHUI SHI, PENGFEI HUO, YUMEI ZHOU
Effect on Ballistic Characteristics of Finned Rocket Due to Surface Wind and Its Correction
In this paper, the effect on ballistic characteristics of a finned rocket due to surface wind is studied in the complex plane. The angle of attack equation is established including the cross motion and roll equation. The ballistic characteristics of the parameters such as θ , ψ , 1 r δ, 2 r δ , α ϕ, 2 Ï•,Î³ï€¨, X and Z are simulated and analyzed. The simulation results show that the surface wind would arouse sizeable scatter at the initial trajectory because of the low flight velocity and surface wind field. A correction method is advanced to decrease the dispersion of the finned rocket by using the energy and aerodynamic control method, and the correction formulas are given to increase the firing accuracy.
Modelling & Trials to Characterize a Shaped Charge Jet Slug Trajectory & Range
This paper describes a study of possible methods of predicting shaped charge range. An initial modelling study suggested the jet slug would have the longest range. Experimental trials were then performed, the aim being to produce data that would provide confident estimates of the likely maximum slug range. The trials were split into two parts. The first ‘short range trial’ characterized the slug. The ‘long range trial’ used tracking radar to measure the trajectory of the slug and hence determine its external ballistic properties. This information was used to calculate a drag law, which in turn was used to predict trajectories of the slug for different elevations and wind conditions. These trials utilized a number of innovative techniques that had not previously been used on small caliber shaped charges. The investigation has demonstrated the value of an integrated approach between simulation and experimentation.
Supersonic Wake Flow Analysis of Finned Projectile Afterbodies at Various Spin Rates
The wake flow of finned cylindrical afterbodies aligned with a Mach number 2.0 air stream is studied in the wind tunnel and also by numerical simulations. Pressure measurements for spinning straight-finned afterbodies show a base pressure dependency on the spin rate. While for low spin rates the base pressure increases, it decreases again for higher spin rates. Particle image velocimetry shows a fundamental change in the flow field for non-spinning surrogate models introducing a swirling motion by canted fins. A counter-rotating circumferential vortex pair is formed due to the streamwise swirling motion. The direction of the flow directly at the base and on the axis of symmetry changes and the base pressure decreases up to an order of magnitude. Higher swirling rates lead to an annular separation line on the base indicating another change in the wake flow structure. In the far wake a region of low upstream directed velocities is formed.
ROBERT HRUSCHKA, CHRISTIAN REY, FRIEDRICH LEOPOLD, FRIEDRICH SEILER
The Research on the Inflation and Trajectory Characteristics of Tandem Compound Parachute System
A tandem compound parachute system composed of a rotating parachute and a round parachute is designed. Using fluid-structure interaction method, the inflation process of the parachute system is simulated. The canopy shape change, the time-historical curves of spinning rate and opening load are obtained. The tower test is conducted to verify the simulation results, and the effects of structure parameters on the system performance are analyzed. The trajectory characteristics of the tandem compound parachute-submunition system are simulated by RecurDyn. The results show that the tandem compound parachute system can inflate successfully with the condition of low flow velocity and come to rotate. The tandem compound parachute system can offer steady spinning rate and falling velocity for smart submunition. Decreasing the canopy area of the rotating parachute can increase the decelerating and spinning efficiency of the parachute system, but the canopy with too small area will make the parachute cords twisted.
Identification of the Aerodynamic Coefficients of a Spin-Stabilized Projectile from Free Flight Data
A general identification method of the aerodynamic coefficients of a spin-stabilized projectile which is based on the Modified Point Mass Trajectory Model (MPMTM) is proposed. The aim of this study is to avoid embedded sensors, which are complex and costly to implement. We consider a unique instrumentation device which is a Doppler RADAR. The method is developed directly taking into account the Doppler RADAR measurement data (radial velocity and angles) in order to override numerical differentiation and smoothing approximations. Finally an identification test using real Doppler RADAR data is given, showing the efficiency of the developed method.
FRANCK DELVARE, CHRISTOPHE GRIGNON, SETTIE HEDDADJ
A Direct-Fire Trajectory Model for Supersonic Through Subsonic Projectile Flight
A simple but accurate method of determining the direct-fire trajectory of projectiles that traverse a flight regime that includes supersonic, transonic and subsonic flight is presented. Closed-form analytical solutions for the important trajectory parameters such as the time-offlight, velocity, gravity drop and wind drift are presented. The method makes use of individual power-law descriptions of the drag variation with Mach number within the supersonic, transonic and subsonic regimes. The method demonstrates that the free-flight trajectory can be characterized with as few as six parameters; the muzzle velocity, muzzle retardation, a power-law exponent that describes the drag variation in supersonic flight, the transition Mach numbers between supersonic and transonic flight, the transition Mach number between transonic and subsonic flight and the retardation at the subsonic transition Mach number. The accuracy and simplicity of the method makes it very useful for preliminary design or performance assessment studies where rapid prediction of projectile trajectories is desired. Sample results are presented for a 9mm pistol bullet that traverses supersonic, transonic and subsonic flight to demonstrate the viability of the method.
Analysis of Super Large Caliber Cannon’s Attacking Efficiency Adopting Cross-section Interception Technology
Projectile shape coefficient, initial velocity and angle of fire determine the only trajectory of projectile for aeroballistics, so trajectory control can be realized exactly by changing these parameters. Cross-section interception technology has been proposed to carry out the saturation attack on group targets at long range. Applying the method of ballistics stimulation, the large caliber cannon weapon system’s efficiency of saturation attack is analyzed. The efficiency is determined by two main factors, the total mass of projectors and the attacking efficiency of single projectile. Thus trajectory control can realize that projectiles fire in turn, arrive in the predicted cross-section at the same time to destroy the target completely. Compared with missiles and rocket weapon, high-muzzle-velocity super large caliber recoilless weapon system with simple guidance device and high energy explosive has longer range, tactical surprise. It can destroy group targets completely on the ground or surfaces ships.
An Instrumented 81-mm Mortar Target Platform for Dynamic Engagements of High Energy Laser Weapons
The Irradiance Collection and Reporting System (ICRS) contains an instrumentation package attached to an 81-mm mortar airframe to create a dynamic target platform to evaluate the effectiveness of high-energy laser (HEL) directed energy weaponry. At the airframe’s midbody is a self-powered Multifunctional Instrumentation and Data Acquisition System module that contains onboard inertial sensors and a telemetry system. An interconnected, separate, front cylindrical irradiance sensor module contains an array of hundreds of miniature fiber-optic detectors along its surface that connect to custom imager electronics inside to detect and measure HEL irradiance spot profile data. Analysis of the materials and coatings against HEL exposure were verified to ensure survivability of the telemetry system components and ICRS hardware. Extensive modeling and simulation were validated by several laboratory experiments conducted at U.S. Army facilities. Captive experiments with a 50-kW laser were also performed to assess the survivability and performance.
Research on Exterior Ballistics Characteristics of Rocket Projectile Based on Intelligent Morphing Technology
In order to study the exterior ballistics characteristics of a rocket projectile with deflection nose based on intelligent morphing technology, methods of numerical simulation and experiment are adopted in the research process. Firstly, aerodynamic parameters for the rocket projectile with a deflection nose were obtained by numerical simulation for the flow field. Typical wind tunnel tests were also conducted to verify the accuracy of the simulation data. Secondly, a 6-degree of freedom dynamic model is presented for calculation of the exterior ballistics of the rocket projectile with a different nose deflection angle. Thirdly, flight tests conducted by the authors’ research group are introduced and test results are given. These show that simulation results agree well with the experimental data. Lastly, some meaningful conclusions are made based on the previous research. All the work is useful for further research and engineering application on adaptive intelligent missile based on intelligent morphing technology.
ZHIJUN WANG, GUODONG WU, JIANPING YIN, JIANYA YI, JINGWEI LI
The Effect of Bullet Diameter and Free Stream Mach Number on Flight Noise
The US Army Research Laboratory has a newly developed experimental setup consisting of a sensor array that allows for expedient and accurate measurement of projectile flight noise. This study examines the effects of projectile flight diameter on the peak sound pressure level (SPL) of the bullet in flight. Additionally an empirical model has been derived from the results of the experiments to aid in the prediction of flight noise given the diameter and Mach number of a projectile. The in-flight signature of projectiles is of particular importance when considering the impact of a weapons signature on the surrounding environment. Included in this research are 4 diameters of small caliber bullets of the same approximate non-dimensional shape. The projectile flight noise was characterized across multiple free stream Mach numbers between Mach 0.5 and Mach 3.0.
Hypersonic Glide Vehicle Tracking Guidance Using L1 Adaptive Controller in the Presence of Input Saturation
This paper describes one of the reference trajectory tracking guidance algorithms using L1 adaptive controller for the hypersonic glide vehicle in the glide phase. The nonlinear dynamic model of glide flight containing uncertain parameters and time-varying disturbances is built. Then L1 adaptive control is used to get onboard reference trajectory fast tracking capability in the presence of large uncertainties, un-modeled dynamics and disturbances. Besides, the deflection command is constraint by amplitude saturation. Finally the numerical simulation results demonstrate the feasibility and advantage of the proposed tracking scheme.
ZHIBING SONG, FAN HU, ZHENYU JIANG, WEIHUA ZHANG
Influence of Yawing Force Frequency on the Angular Motion and Ballistic Characteristics of a Dual-spin Projectile
A roll-decoupled course correction fuze with canards can improve the accuracy of conventional unguided ammunitions cheaply and effectively. These types of fuzes increase accuracy by reducing the effect of angular and translational motion produced by the cyclical yawing force applied on the projectile. In order to investigate the influence of yawing forces on angular motion, a theoretical solution of the total yaw angle function with the cyclical yawing force will be deduced utilizing the 7 degrees of freedom (7-DOF) model designed for this calculation. Furthermore, a detailed simulation is carried out to determine the influence rules. The results will indicate that when the frequency of yawing force is close to the initial turning rate, the total yaw angle will increase, and the range will decrease sharply. Moreover, a yawing force at an appropriate frequency can correct the gun azimuth and elevation perturbations to varying degrees.
Identification of the Aerodynamic Coefficients of a 155mm Artillery Shell Based on Free Flight Data
The identification of aerodynamic coefficients, from free flight measurements, remains complex and challenging for vehicles like ammunition, space probes, Unmanned Aerial Vehicles. This paper presents a data-driven identification procedure of the aerodynamic coefficients of a 155mm artillery shell based on free flight data. The estimated coefficients are expressed in a table of value format (or tabular form) as a function of the Mach number. The free flight data correspond to three-axis magnetometer and trajectory radar measurements for different initial experimental conditions.
MARIE ALBISSER, CLAUDE BERNER, LOIC BERNARD, CHRISTOPHE GRIGNON
Numerical Virtual Flight Technology and Its Application in the Stage Separation Simulation
A novel framework of Numerical virtual flight (NVF) is proposed in this paper to fully couple the closed-loop controlled 6DOF flight simulation with unsteady numerical simulation of flow field. The NVF system is built based on the collaborative simulation of commercial software ANSYS Fluent and Simulink, and applied to simulate the controlled stage separation process of a two-stage rocket.
FAN HU, ZHIBING SONG, ZHENYU JIANG, WEIHUA ZHANG
Optimal Detonation Based on Ammunition Attitude Control in the Terminal Trajectory
Hitting accuracy and damage efficiency are eternal themes of the ammunition development. In recent years, new ammunition and advanced warhead are growing, and one of the common characteristics is that the damage element of warhead is concentrated on a particular direction. Therefore, the optimal detonation is affected by both the attitude of ammunition and the encounter trajectory. In this paper, an optimal detonation method based on the detonation time calculation and ammunition attitude adjustment is proposed. Firstly, detonation model is established in which both the encounter trajectory and the attitude are considered comprehensively. Secondly, the time window of attitude adjustment is proposed. Thirdly, the golden section control law based on the characteristic model is used to adjust the attitude to achieve optimal detonation. At last, Monte Carlo simulation results show that the method proposed in this paper can greatly improve the hitting accuracy of damage elements.
Optimizing Guidance Strategy for Gun Launched Underactuated Weapons
This paper presents a guidance strategy for the control of underactuated mortar. The performance will be evaluated as compared to the traditional guidance law Proportional Navigation (ProNav) and the Impact Point Prediction (IPP). Performance and optimizations of the guidance law based was evaluated using a six degree-of-freedom (6-DOF) simulation environment for a 120mm guided mortar. Effectiveness of each guidance law for a guide-to-hit mission was assessed using Engagement Footprint Ratio (EFR) and Monte Carlo analysis in the simulation environment. Relative performance of the guidance strategies is presented and this comparison is used to demonstrate the effectiveness of each of the strategies in achieving target intercept by a guided mortar with limited control authority.
Selected Aspects of the Design Process of a Calibration Projectile: The Vulcano Scout Case Study
The use of unguided sub-calibre ammunition has enabled the engaging of targets far beyond conventional artillery ranges. In this new scenario, the ammunition has longer flight times and reaches higher altitudes; thus, systematic errors and the unavailability of detailed meteorological information play more significant roles in affecting accuracy than they do in the case of shorter range firings. The Vulcano Scout Ammunition has been devised to overcome these issues: it is an unguided instrumented round (to be fired near or above the target) that transmits aiming correction information to the launch pad. This paper describes the design process of this ammunition and its future development.
Free Flight Tests of a Medium Caliber Ammunition Using an Impulse Thruster: Preliminary Phase
Experimental investigations for the guidance of a mid-caliber spin-stabilized projectile by using a single impulse thruster located at the center of mass will be presented. Free flight tests on a proving ground for modified Bofors projectiles equipped with a single 3N.s pyrotechnic impulse thruster have been performed. To assure the initiation of the impulser during the flight, a complete pyrotechnical chain has been designed including a high safety electro-pyrotechnic detonator and a safety arming device that is compliant with the current safety requirements. It shows very low response time dispersion that is essential for further synchronization of the impulse with the roll position in order to control the deflection direction. Results have shown that projectiles are clearly deflected from their ballistic trajectories when triggering the impulse thruster. Deflection amplitudes observed are reproducible and conform to the expected values.
Progressive Die Stamped Steel Aerostable Penetrator Design and Flight Test Results
The US Army has been investigating an aerostable penetrator formed from sheetmetal using progressive die stamping technology. One advantage of this approach is that the penetrator shaft is substantially rectangular in cross section, increasing packing density relative to more conventional designs. A second advantage is that the sheet metal technology allows greater control of the tailfin geometry. The tailfin span can be increased beyond the limits that would be imposed by forging or swaging technologies if the increase is needed for optimal flight stability. The disadvantage of the sheetmetal technology is that conventional cruciform tailfins cannot be produced. The AMRDEC has investigated three tailfin design concepts and has found a configuration that provides both aerodynamic stability and good packaging density. This paper will provide an overview of the penetrator airframe design and will discuss flight testing aerodynamic results.
Reduction in Line Deviation by Re-design of Propulsion System of a Multi Nozzle Rocket System: A Case Study
This paper presents the study undertaken to determine the effect of ballistic parameters on line deviation of an unguided rocket. A detailed external ballistic study of a multiple canted nozzle rocket system was carried out and a code developed using a six degree of freedom (6 DOF) trajectory model. Aerodynamic coefficients determined from CFD studies were used for estimation of line deviation. Results of actual trials were used to validate the code. A study of effect of various parameters such as thrust misalignment, wind, variation in inertial properties, mass imbalance, initial velocity and spin on the rocket performance were carried out from simulation studies. Based on the analysis and study, various methods were employed to successfully eliminate the line deviation. Subsequently, design modifications were incorporated and dynamic trial with modified design were carried out successfully with reduction in line deviation.
M. K. SHARMA, P. T. ROJATKAR, K. J. DANIEL, K. M. RAJAN
Ambient Gas Pressure Effects on the Ignition of Pyrotechnic Countermeasure Decoy Flares
Rapid and effective ignition of pyrotechnic countermeasure decoy flares is vitally important to the safety of expensive military platforms such as aircraft. QinetiQ is conducting experimental and theoretical research into pyrotechnic countermeasure decoy flares. A key part of this work is the development and application of improved ignition models to improve the understanding of the ignition processes occurring for these flares. Typically, these flares are wrapped in a material such as foil. Until this material bursts or ruptures, the flare can be considered to be effectively a closed system. Therefore it is possible to use gun internal ballistics models to investigate the ignition and combustion processes in these flares. Previous work validated the computer models for conditions of atmospheric pressure and 21ºC. This paper describes computer modelling and experiments conducted to validate predictions at pressures equivalent to those at 20000 and 40000 feet.
ROBERT CLARIDGE, LES GIBBONS, ALISDAIR BATCHEM, ROBIN HUGHES
Mechanism of Plasma Ignition in Electrothermal-chemical Launcher
Plasma injector is a core component in an electrothermal-chemical (ETC) launcher. Its work state directly influences the whole system's launch efficiency. The interaction between plasma and propellants is a very important mechanism in ETC technology development. Based on the transient radiation model and open air plasma jet experiment, the mechanism of plasma ignition process is analyzed. Results show that the surface of local solid propellant grain can quickly achieve the ignition point by early transient plasma radiation. But it needs enough time to maintain the high energy flow to make self-sustained combustion of solid propellant grains. Because of the limited space characteristics of transient radiation, the near-field propellant grains can gain enough energy by the strong transient radiation to be ignited and achieve self-sustained combustion. The far-field propellant grains mainly gain the energy by the activated particles in plasma jet to be ignited and self-sustained combustion. Experiments show that plasma jet always has a high flow velocity in the area of the cartridge. Compared with conventional ignition, the solid propellant grains can obtain more quick and uniform ignition and self-sustained combustion by this kind of ablation controlled arc (ACA) plasma via energy skin effect of propellant grains, pre-heat temperature mechanism and high efficient jet diffusion.
Application of Transient Burning Rate Model of Solid Propellant in Electrothermal-chemical Launch Simulation
A 30mm electrothermal-chemical (ETC) gun experimental system is employed to research the burning rate characteristics of 4/7 high-nitrogen solid propellant. A modified 0D internal ballistic model is established to simulate the ETC launch. According to the measured pressure and electrical parameters, a transient burning rate law including the influence of enhanced gas generation rates (EGGR) coefficient by electric power and pressure gradient (dp/dt) is added into the model. The EGGR coefficient of 4/7 high-nitrogen solid propellant is equal to 0.005MW-1. Both simulated breech pressure and projectile muzzle velocity accord with the experimental results well. Compared with Woodley’s modified burning rate law, the breech pressure curves acquired by the transient burning rate law are more consistent with test results. Based on the parameters calculated in the model, the relationship among propellant burning rate, pressure gradient (dp/dt) and electric power are analyzed. Depending on the transient burning rate law and experimental data, the burning of solid propellant under the condition of plasma is described more accurately.
YONG JIN, GANG WAN, CHUN-XIA YANG, HAI-YUAN LI, BAO-MING LI
Research on Proximity Effect of Electromagnetic Railgun
The rails of electromagnetic railgun can be ablated by the temperature rise due to current concentration. The current distributions on the rails and armature are not only affected by the skin effect, but also influenced by the proximity effect which is rarely mentioned. This paper illustrated the difference between skin effect and proximity effect. And the influencing factors of proximity effect were investigated. Results show that the current is concentrated on the surface around rails due to the skin effect, and the proximity effect exacerbates the current density on the inner surfaces of rails. Decrease in distance from rails to enhance the proximity effect, but has nothing to do with the skin effect, which also augments the rail resistance, resulting in temperature rise. It can explain the reason why the ablation is often detected in the small caliber railgun. Research results in this paper can provide support for design and optimization of electromagnetic railgun.
Design and Test of a Hypervelocity Electromagnetic Launcher
A hypervelocity electromagnetic (EM) launch system is designed and employed to observe the special phenomenon when the projectile velocity is more than 3km/s. The whole launch system consisted of a 9MJ capacitive pulse power supply (PPS) and railgun device. The capacitive PPS is composed of 180 pulse forming units (PFU). Each PFU has a compact capacitor (1mF/10kV), a pulse shaping inductor (20μH), a crowbar diode and thyristor switch. The whole length of railgun is 5.5m, and with a travel length of 5.3m.Test results show that the PPS can afford a pulse current, which the peak current and full width at half maximum (FWHM) is more than 500kA and 4ms, respectively. The EML device can accelerate a 181.0g projectile to 3550.0m/s muzzle velocity when the input energy is 3.5MJ.And the whole system launch efficiency is nearly 32.0%.
Numerical Simulation of Interior Ballistic Process of Railgun Based on the Multi-field Coupled Model
Railgun launcher design relies on appropriate models. A multi-field coupled model of railgun launcher was presented in this paper. The 3D transient multi-field was composed of electromagnetic field, thermal field and structural field. The magnetic diffusion equations were solved by a finite-element boundary-element coupling method. The thermal diffusion equations and structural equations were solved by a finite element method. A coupled calculation was achieved by the transfer data from the electromagnetic field to the thermal and structural field. Some characteristics of railgun shot, such as velocity skin effect, meltwave erosion and magnetic sawing, which are generated under the condition of largecurrent and high-speed sliding electrical contact, were demonstrated by numerical simulation.
Dynamic Response of a Railgun Barrel by Armature Transient Impact
Unlike the effect of conventional artillery projectile on the barrel, the rails are mainly stressed components when a railgun is launching. The rails were stressed with both uniform distribution force and concentrated force associated with the armature moving. And the barrel's stress and strain were calculated with structural mechanics by LS-DYNA. A three-dimensional railgun barrel model for transient armature impact was built to analyze the barrel’s response. The changing law of the armature’s stress during the launching process was obtained. Then the rail’s displacement was employed to describe the barrel's response. The results show that the armature has adaptive adjustment as armature vibrated in the barrel. The rail’s maximum displacement position is lag behind the armature, and has no effect on the contact condition of the rail and armature.
Study of Propellant Characteristic Effects on Pressure Waves for Low-Zone of a Bi-Modular Charge
In this paper, the influence of the propellant characteristic on pressure waves for the lowzone of a Bi-modular charge was investigated by experiments and simulation using a interior ballistics two-phase flow model. The modular charge usually embodies two kinds of module types. One kind of module is the low-zone component that is fired either singly (zone-1) or in pairs (zone-2) to achieve minimum and intermediate ranges. When zone 2 with two separate low-zone modules is fired, the pressure wave usually will be serious in the chamber of gun. The web size and burning rates of the propellant are very important for influence on the pressure wave. A set of experiments has been done to study the pressure wave with different propellant characteristics. Also a two-phase, one-dimensional model of the interior ballistics and the relevant computer code have been developed to study the pressure wave when zone 2 in a Bi-modular charge was loaded in the chamber of gun with several different propellants. The simulation of the pressure wave for zone 2 in the modular charge shows good agreement between model and experimental measurements. The study results can serve as a guideline for optimizing the charge of zone 2 in a Bi-modular charge.
YING-HUA GUO, JIANGUO WEI, JIAN LI, YAN-CHENG DONG
3D Transient Simulation of Melt Wave and Transition Mechanisms in a Moving Armature
The A, -A finite element method (FEM) is employed to calculate the 3D transient eddy current field and temperature field in a railgun with a moving armature based on a Lagrange coordinate system. It is assumed that the element's material properties are changed from metal to air when it is melted. Simulation results show that this model can greatly simulate the influence of current distribution by velocity skin effects. It predicts a current density concentration on the tail and side edge of the armature where the temperature is higher. Also the melt wave diffusion process can be described from the tip of the tail to the center. At the same time, the frictional heat is cumulative on the surface and leads the surface melting more quickly and the melt wave moving faster than the solid state. When the armature surface has completely melted into a gaseous phase a transition occurs. This melting transition mechanism is simulated and discussed meticulously.
JINGUO WU, YINGTAO XU, HAIYUAN LI, BAOMING LI
3D Numerical Simulation and Analysis of Railgun Gouging Mechanism
A gouging phenomenon with a hypervelocity sliding electrical contact in railgun not only shortens the rail lifetime, it but also affects the interior ballistic performance. In this paper, a 3-D numerical model was introduced to simulate and analyze the generation mechanism and evolution of the railgun gouging phenomenon. Johnson-Cook failure material model and Mie-Grüneisen equation of state were adopted for the simulations. The results show that a rail surface bulge is an important factor to induce gouging. High density and high pressure material flow on the contact surface obliquely extruding into the rail when accelerating the armature to a high velocity can produce gouging. The formation of gouging is suppressed by controlling the bulge size to a certain range and selecting suitable materials for rail surface coating. The numerical simulation result is in a good agreement with the experimental result, which shows that the proposed computing model and methodology are reliable.
BO TANG, QIANGHUA LIN, HAIYUAN LI, BAOMING LI
Numerical Modelling of Solid Rocket Motors for Mechanical Integrity Assessment
To develop capability in estimating the mechanical integrity of solid rocket motors, a computational model has been developed in this paper. Using parameters and mechanical properties obtained from literature and industry, finite element numerical modelling was performed in COMSOL. Mechanical analysis has been performed keeping in mind, the rocket motor during firing. The stress experienced by the rocket motor during the firing process under pressure loading has then been assessed from the computational study.
PHILIP P. GILL, AMER HAMEED, MIKE C. GIBSON
The Research on Dynamic Calibration of the Shockwave Pressure Test System of the Cannon
By the dynamic calibration of the shock-wave pressure test system of the cannon, the dynamic features are achieved. The influence of test results from the dynamic features is analyzed. The conclusion is that the peak value of the shockwave pressure from the cannon is correct, the impulse we test of the shockwave is lower.
Microcellular Foaming of Cellulose Acetate Binder-based Combustible Objects by Supercritical CO2
Microcellular combustible objects are based on crystalline explosives bonded in polymer binders for good heat resistance performance. The porous structures can be generated using supercritical CO2 as foaming agent. Due to their porous structures, they are distinguished by high burning rate and can be adjusted to manifold applications. In this paper, microcellular combustible objects, based on cellulose acetate (CA) bonded 1,3,5-Trinitrohexahydro-1,3,5-triazine (RDX), were performed by solvent method and then foamed by two-step foaming process. Scanning Electron Microscopy (SEM) was used to investigate the influencing factors on the inner porous structure in foaming process, and the results revealed that micropores generated from microcracks between RDX particles and CA matrix, and then developed into viable bubbles. Higher foaming temperature, higher saturation pressure and lower saturation temperature is conducive to growth of micropores. Closed vessel test was used to test the combustion behaviour of samples with 60%, 65% and 70% RDX. The results of closed vessel test indicated that the foamed structure reduced the burning time and the burning behaviours can be adjusted by varying RDX content and foaming conditions.
Simulation of Closed Vessel Combustion Using the 2D ICT-Cellular-Combustion-Algorithm
A model using the ICT-Cellular-Combustion-Algorithm (ICCA) is presented which makes it possible to simulate closed vessel combustion of propellants with arbitrary cross sectional geometry. ICCA enables the user to explore new possible propellant geometries for which it is not possible to calculate analytical form functions. The model uses the 2D version of ICCA that uses 2D bitmaps as input data and simulates the 2D form function which is then linked to the variables that are needed to simulate 3D propellant combustion. It is shown that the simulation results for standard propellant geometries match the results from the new standard interior ballistics code SimIB perfectly.
Modeling the Ignition of Insensitive Propellant by a Nanothermite Igniter
The use of insensitive propellants for propelling Low Vulnerability Ammunitions (LoVA) requires a appropriate ignition system for preserving interior ballistics performances. This paper presents the upgrading of the French Interior Ballistics code Mobidic in order to render the dynamics of ignition and combustion of insensitive propellant ignited with nanothermites. This upgrade consists in a set of numerical models whose parameterizing allows rendering the experimentally observed phenomena.
GUILLAUME ORSAT, BARBARA BASCHUNG, MAXIME CHIROLI, AMAR BOUCHAMA
An Investigation into Enhanced Fire Control Systems for Moving Vehicles
As the agility of military vehicles improves and the need to fire more accurately on the move increases there is a need to consider enhancements to the fire control system. This work examines the possibility of combining together a weapon control simulation with a gun dynamics simulation. The initial conditions for the gun dynamics model are obtained from the weapon control simulation, which includes vehicle motions, at shot start. In this initial investigation it is shown that there is a 1.2 mrad standard deviation from a control case, which has no initial gun motion. The conclusion from this work is that there is a possible benefit of enhancing the fire control system by combining together the gun motions in determining the time to initiate the firing of the gun.
New Generation Ignition Simulator Device
Modern ammunition present complex architectures and may use LOVA propellant, which require high performance igniters. This paper presents the implementation of a new generation ignition simulator, for characterizing, evaluating and validating the performances of the new igniters. This simulator is designed, manufactured, tested by Nexter Munitions and funded by DGA (French MoD).This experimental device allows to study interaction between an ignition composition and a propellant grain, between the igniter and a propellant grain and between the igniter and a full loading (from the 40 mm caliber to the 155 mm caliber). It provides access to extensive data for a better understanding of ignition process. Thanks to these data, the work of development of igniters, including for LOVA propellants, is easier. This allows more complex designs in order to increase the effectiveness of these igniters. We can also optimize new ammunition architecture and improve operating safety.
Gas Generation Rules of 19-Perforation TEGDN Propellants with Different Length/Outside Diameter Ratios and Perforation Diameters
A set of 19-perforation propellants containing triethyleneglycol dinitrate (TEGDN) with different length/outside diameter ratios and perforation diameters was prepared and tested in a closed vessel to investigate their burning progressivity. The influence of length/outside diameter ratios and perforation diameters on the progressive combustion performance is studied through the dynamic vivacity method. With an increasing of the length/outsider diameter, the silvering point occurs earlier and longer and the burning progressivity of surface area can be improved. For propellants with same length/outside diameter ratio, with a decreasing of perforation diameter, the slivering point lags behind and the burning progressivity becomes greater. The silvering point corresponds to the instantaneous burning area which is related to the form function and silvering process. However, the total burning progressivity of propellant is a very comprehensive result of propellant under multiple actions, including the mass fraction of burnt propellant, grain size and burning rate at different pressure regions. The correlation between them can boost a better understanding on the interaction between grain size, silvering burning process and burning progressivity.
Research on Combustion Characteristic Between Plasma Ignition and High-energy Nitramine Gun Propellant
In order to research the combustion characteristic of high-energy nitramine gun propellant with plasma ignition, a series of experiments was conducted. These included ignition ablation experiment, interrupted combustion experiment, closed vessel experiment with different charge voltage and ignition modes of nitramine gun propellant on plasma. A plasma ignition burning law of high-energy nitramine gun propellants was found based on the analyses of experimentation results. The results show that the plasma jet ablated the gun propellant. Many tiny holes formed on the surface of the gun propellant after the impact of plasma. There is almost no delay time of ignition under the 7.89kV of charge. The pressure in chamber rises to 10MPa quickly. Also the gun propellant burns completely. On the pressure-time curve there is an inflexion near the 10 MPa data point. The gun propellant is ignited by the mixture of plasma and the ablation resultants. The gun propellant can be ignited completely, simultaneously, instantaneously under the impact of high energy plasma.
Burning Mechanism of Foamed Oblate Spherical Gun Propellants
The micro-porous oblate spherical gun propellants prepared by supercritical carbon dioxide (SC-CO2) foaming technique exhibit high burning rate due to their porous structures. The morphologies of foamed oblate spherical propellants are characterized by scanning electron microscope (SEM), the SEM photos show that there exist massive separated micro pores in the foamed propellants. To investigate the combustion process ï¼Œ both the quenched combustion experiments and closed vessel experiments were carried out in this work. The results of closed vessel experiments show that burning time of foamed propellants is less than that of unfoamed samples, which indicates that the burning rate of foamed propellants is higher than that of the unfoamed samples. The results of quenched combustion experiment show that the burning surface area of foamed oblate spherical propellants is very large. Besides, the separated pores get connected during the burning process, and this increases the burning thickness. It is believed that the large burning surface area and increased burning thickness lead to the high burning rate of the foamed propellants.
Some Considerations on the Methods of Analysis of Closed Vessel Test Data
Data obtained from closed vessel tests, performed for nine values of loading density from the range [50,250] kg/m3 with seven tests for the each value of loading density, are analysed to determine the vivacity function. Based on this broad experimental material the following problems are considered: (i) How large is the random scatter of the vivacity function values for nominally the same conditions of the tests? (ii) Can we determine the dependence of the burning rate on pressure making use of the vivacity functions for various values of loading density? (iii) What is the influence of heat losses on the vivacity function? We find that the form of the vivacity function is highly dependent on the loading density.
Protective Structure Design for Electronic Systems within Shells Against High-G Overloading
A protective structure for electronic systems within shells is proposed in this paper to improve the anti-overloading ability of electronic system in projectile by using three-dimensional finite element software. As a consequence, the unitary structure of the electronic system and the cushion with different holes (4,6,8,10 equally distributed) is obtained. Moreover, the response of the projectile after penetration will be monitored. The effects on the shell can reflect the overloading and stress distribution on the electronic system. The numerical results are compared to obtain a better protective structure.
HAIFU YE, DONGJIE LI, HONGZHI ZHU, HE YANG
Investigations of Combustion Process of Pyrotechnic Elements Applied in Military Munitions Using X-ray Real Time Radioscopy
Investigations on combustion processes occurring in the end-burning, low-gas, multi–increment pyrotechnic delay element of the depth charge dropped from the helicopter and in the end-burning, high-gas pyrotechnic tracer with combustible body of the anti-tank guided missile using Real-Time X-ray Radioscopy (RTR), are presented. RTR detection, operating at 30 frames per second, registered the shape and movement of burning zone respectively in the delay element and in the tracer. The burning zone separated unburnt (unreacted) and burnt part (combustion products) of tested pyrotechnic item. The burning zone propagating along the delay element was much more difficult to be registered by RTR because of much lower differences between densities of its unburnt and burnt parts in comparison with analogical parts of the tracer.
MARCIN NITA, MACIEJ MISZCZAK, JACEK BORKOWSKI
Consistency Research on Interior Ballistic of Small Caliber Electrothermal-Chemical Launching
A method for expression of interior ballistic consistency was presented to describe the consistency of a small caliber electrothermal-chemical (ETC) launching tests. For a group of N tests with the same ETC launching conditions, if x was a test parameter, each test value could be written as xi. We could calculate and obtain both the arithmetic mean value and standard deviation estimate. Hence, the consistency factor k of this test parameter can be defined as the arithmetic mean value divided by the standard deviation estimate. And the smaller the value k shows the better consistency of the data. This consistency factor could be employed to describe the consistency of both different parameters and same parameter in a group tests. The firing tests of the small caliber ETC launching were conducted. And the consistency of ETC launching tests was researched. Influences of parameters on the ballistic consistency were discussed through the consistency factor.
YONG JIN, YANJIE NI, GANG WAN, HAIYUAN LI, BAOMING LI
Study on the Display of Gun Firing Process Based on Test Data
Traditionally, the vibration test results during a gun firing in the range are expressed by means of curves, tables and words. Although these means can satisfy the needs of the model research of a howitzer, it is difficult to express some important detail. Thus, the video display of the test results is urgently required for the model research of a gun. In order to enrich the output forms, extend the function and meaning of the test results, and play a guiding role more efficiently for the test results, the technology of motion display of the gun firing process based on test data was proposed. The principle and realization technology of the video display of the test data have been described, and the engineering application has also been completed.
JUN LIU, XIAOJUN SHAO, PENGKE LIU, FAMING ZHOU, GANG HENG
Analysis and Optimization Design of the Whole Trajectory as a Primary Exploration
In this paper, the effects of the whole trajectory process on the gunshot, power and the gun structure are studied based on the theory of the terminal ballistics, exterior ballistics and the interior ballistics. The relationship among the terminal ballistics, external ballistics and the interior ballistics is also discussed. Then taking a large-caliber high explosive projectile as a calculation example, the whole ballistic optimal design model is built and the optimizing results are obtained using a genetic algorithm.
MING-AN ZHANG, YAOFENG XU, CLIVE RUSSELL WOODLEY
Detecting of the Development of the Gun Interior Ballistic Design Technology
This paper addresses the Research status of the interior ballistic design. The development trends of the interior ballistic are also detected by combining the development of the propellant, the new charge structure and the ammunition.
JIA-WEI DI, CHANGJUN ZHOU, YUHENG FAN, NA ZHAO, WEI-WEI ZHANG, BING LI
Combustion Experiment of the High Bore Pressure Propellant Under High Pressure and Optimization Model of Burning Rate
To study the combustion characteristics of propellant under high pressure conditions in the bore, a closed bomb system was used to carry out high-pressure combustion experiments. An exponential burning rate law in the range 30MPa ~ 350MPa was obtained. A combined optimal method with a multi-island genetic algorithm (MIGA) and sequential quadratic programming (SQP) was applied to search for the best-fitting burning rate law with the experimental pressure. Results show that the pressure obtained by the optimization method agrees with the experimental one better than the conventional method and the high-pressure burning rate characteristic can be represented more precisely.
YONGJIE CAO, WEI DAI, KUI NIE, WEIWEI ZHANG, XIAOHONG HU
Bullet Abrasion from Small Arms Ammunition
When at bullet moves along a rifled barrel, the engraving of the jacket or the driving band will cause some degree of abrasion which is emitted as metallic dust. This effect is especially prominent in small caliber guns. For small arms bullets, the jacket surface is exclusively made of tombac for which the emitted dust will consist of copper and some zinc. Inhalation of these metals may cause severe health problems among the users. Although the illness is temporary, the soldiers may be unfit to maintain his task for several hours after exposure. This paper documents a series of measurements for which the amount of emitted dust has been measured. Steel-cored projectiles may have more than 100% more dust emission than lead-cored ones. However, the amount does not depend solely on the ammunition, but the shape of the barrel is also a significant factor.
Heat Transfer Analysis in 35 mm Anti-Aircraft Gun Barrel
It is essential by the development of shooting cycle during endurance tests that the gun barrel temperature does not exceed the value set by the manufacturer. Therefore a series of shooting should be carried out which comprises both the stages of shooting, and set intervals between shooting. The methods for calculating heat transfer, proposed in literature, are often too time-consuming, to be used for cycle of several hundred shots. The paper presents results of numerical simulations of heat transfer in the gun barrel of anti-aircraft cannon caliber 35 mm (total length 3150 mm). The gun barrel was divided into 6 zones with the assumed boundary conditions. The initial-boundary value problem, i.e. the Fourier equation of transient heat conduction with the initial and boundary conditions was solved numerically. The paper presents the results of calculations for a single shot and a sequence of seven shots followed by a pause. The calculations are performed relatively fast on PC, and the proposed mathematical model of heat transfer can be easily tuned to the experimental data.
ZBIGNIEW LECIEJEWSKI, MAREK PREISKORN, ZBIGNIEW SURMA, JANUSZ ZMYWACZYK
Theoretical and Experimental Investigations on rocket Propulsion of Counterprojectile of Active Protection System
The paper presents selected results of a research project the aim of which is to perform the technology demonstrator of an active protection system. One of the elements of this system is a smart counterprojectile. The counterprojectile head includes electronic components sensitive to high overload. To avoid such overload effects, a solid propellant rocket engine was used as a propulsion system. The design concept of a propulsion system of a counterprojectile is described. Due to short operation time, it is assumed that the propellant system will have the features of a rocket booster. A propellant charge will consist of seven rocket propellant grains with low-combustible layer thickness and a large area of burning, ensuring high-power engine thrust. Based on the Polish new homogeneous solid rocket propellant, and adopted dimensions of the propellant charge and nozzle block, calculations of ballistic characteristics of the propulsion system were carried out. In order to verify the results of a theoretical analysis, experimental studies were carried out.
ZBIGNIEW LECIEJEWSKI, ZBIGNIEW SURMA, MIROSLAW ZAHOR
Experimental Study on the Effect of Propellant Fracture on the Combustion Properties Under Low Temperature
Three kinds of propellant fracturing experiment are conducted at two different impacting velocity and low temperature (-40) in order to study the effect of the damaged propellant on the combustion performances. The smashed samples are put in order and analyzed. The static combustion test of the smashed propellant is conducted under the low temperature in the closed bomb. The results indicate that, the larger the ratio of the broken propellant, the bigger the gas generation speed in the low pressure range less than 100MPa, and the faster the pressure rising. The results can provide guidance for the design and study of a new high energy propellant.
MINGAN ZHANG, SHOURUI NIU, BING LI, YUAN LI, WEIWEI ZHANG
Innovative Boron Nitride-doped Propellants
RICHARD FIELD, KENNETH KLINGAMAN, MICHAEL FAIR, JOHN BOLOGNINI, ROBIN CROWNOVER, CARLTON P
On-line Auto Measurement of Residual Solvent Weight and Its Influence on Mechanical Properties of Propellant
An on-line auto mass measurement approach was applied to study the volatilization of the residual solvents during the drying process of the single-based propellant, double-based propellant containing triethyleneglycol dinitrate (TEGDN propellant, denoted as TEGDN-1) and TEGDN propellant containing RDX (denoted as TEGDN-2). Their drying rate curves were obtained by the on-line auto mass measurement approach. The mechanical properties of the three kinds of propellants were influenced by different residual solvent contents. The propellant strands are sufficiently plastic and elastic to be cut without being deformed when they are dried to a certain residual solvent contents.
ZHENGGANG XIAO, YUANBO ZHANG, CHAOYANG DONG
Molecularly Imprinted Polymers-based Electrochemical Sensor for Detection of Nitrocellulose
Nitrocellulose, a kind of explosive substances, is widely used in the commercial and military field. It is harmful to public safe and environment. In order to protect personnel from explosion of nitrocellulose, it must be unambiguously detected in real time. At present, the explosive substances are mainly detected and analyzed by the analytical instruments. However, the most of these methods are very expensive and time-consuming, which restricts its widespread use. Compared to the spectral methods, electrochemical analysis presents advantages such as simplicity, high sensitivity and low cost. Combining with the molecular imprinting methodology with electrochemical sensor technology has been used in the filed of nitro explosives detection. But there is no report on the detection of NC by MIP sensor at moment. So the purpose of paper is a preparation of MIP sensor for detection nitrocellulose.
Enrichment of Fluorinated Nano-TiO2 Composite on the Surface of Propellants
It is well known that fluoropolymers as surface modifying agents are well suitable for the preparation of low surface energy materials. This behaviour is related to the migration of the fluorinated chains at the air/solid interface, thus, leading to the surface enrichment in fluorinated groups. In this paper, fluorinated nanocomposite particles containing fluoropolymers in the shell and TiO2 nanoparticles in the core were used as an additive to tailor the surface properties of propellant to meet the requirements of progressive burning and anti-erosion performance of propellant for high loading density tank guns. The surface migration and enrichment effects of fluorinated TiO2 nanocomposite additives with low surface energy toward the air/solid interface of propellants were investigated. This study can boost the research of smart construction of slowing burning and anti-wear layer in the propellants.
Numerical Simulation of Back Blast Flow Field of a Recoilless Gun Launching in Confined Space
A recoilless gun is a kind of weapon equipment for individual soldier and its back blast flow has certain influence on the shooter during the launch process. In order to study the launch safety of a recoilless gun firing in a confined space of 2.5×2.5×2m, numerical simulation of the back blast flow field was carried out based on the three-dimensional unsteady viscous compressible N-S equations. The result shows that a complex reflected shock wave is formed due to the reflection of the wall behind the nozzle. The reflected shock wave represents reciprocating motion in the confined space and its intensity is much higher than that of the initial shock wave. Critical damage will be imposed on the shooter if no safeguard procedure is adopted. The high temperature gas flow may ignite the inflammable gases in the confined space and cause secondary damage. The research results are significant for understanding the characteristics of the back blast flow of the recoilless gun launching in the confined space, predicting and taking effective action to reduce the damage on the shooter.
XIANGMING ZHANG, WENLONG YUE, ZHIFEI LI, JING HU
Study on Perormance and Application of Blends of GAPE and NC
The energetic materials based on nitrocellulose (NC) become brittle at low temperature because of the semi-stiff chains it contains. GAP-based energetic thermoplastic elastomers (GAPE) is a kind of copolymer with flexible block, which can be used to toughen NC. A series of blends of NC and GAPE formula and NC/GAPE based propellant with RDX specimens were prepared. The density and the mechanical properties of mixture binders films were examined. The burning characteristics of NC/GAPE based propellant with RDX were investigated by closed bomb test. The results show that the NC/GAPE blends exhibit good miscibility and outperform pure NC at low temperature. The density and the tensile strength gradually decrease with the mass fraction of GAPE increasing. The NC/GAPE blends exhibit two transition temperatures, the difference between which reduces to minimum at the GAPE/NC ratio of 40:60.Furthermore, the results of closed bomb test suggest that the NC/GAPE/RDX propellants burn normally.
LE-QIN XIAO, WEI-LIANG ZHOU, XIAO-XIA JIAN
Numerical Investigation on the Muzzle Blast of Aircraft Gun
When the aircraft gun is fired in flight, some complicated physical phenomena may occur. Base on the three dimensional Euler equations and multi-block structured grids, the muzzle flowfield of aircraft embedded guns in four different shooting conditions were simulated numerically by using Ansys Fluent software. These conditions include the shooting in the static environment and the inflow with different velocity. The expanding, reflecting and diffracting process of muzzle blast were discussed in detail. In addition, the numerical results revealed the generation and propagation of the separating shock which was induced by the intense interaction between muzzle jet flow and supersonic inflow. Furthermore, the characteristics of structural change of the muzzle blast were also discussed in these different shooting conditions as well as its blast intensity on the aircraft surface.
Mass Asymmetry and Tricyclic Wobble Motion Assessment Using Automated Launch Video Analysis
This paper describes an approach to identify epicyclic and tricyclic motion during projectile flight caused by mass asymmetries in spin-stabilized projectiles. Flight video was captured following projectile launch of several M110A2E1 155mm artillery projectiles. These videos were then analyzed using the Automated Flight Video Analysis method to attain their initial position and orientation histories. Examination of the pitch and yaw histories clearly indicates that in addition to epicyclic motion’s nutation and precession oscillations, an even faster wobble amplitude is present during each spin revolution, even though some of the amplitudes of the oscillation are smaller than 0.02 degrees. The results are compared to a sequence of shots where little appreciable mass asymmetries were present, and only nutation and precession frequencies are predominantly apparent in the motion history results. Magnitudes of the wobble motion are estimated and compared to product of inertia measurements of the asymmetric projectiles.
JOSEPH DONINI, WILLIAM GARDNER, JOBIN JOHN, WALTER KOENIG
Measurement of In-Bore Side Loads and Comparison to First Maximum Yaw
In-bore yaw of a projectile in a gun tube has been shown to result in range loss if the yaw is significant. An attempt was made to determine if relationships between in-bore yaw and projectile First Maximum Yaw (FMY) were observable. Experiments were conducted in which pressure transducers were mounted near the muzzle of a 155mm cannon in three sets of four. Each set formed a cruciform pattern to obtain a differential pressure across the projectile. These data were then integrated to form a picture of what the overall pressure distribution was along the side of the projectile. The pressure distribution was used to determine a magnitude and direction of the overturning moment acting on the projectile. This moment and its resulting angular acceleration were then compared to the actual first maximum yaw observed in the test. The degree of correlation was examined using various statistical techniques. Overall uncertainty in the projectile dynamics was between 20% and 40% of the mean values of FMY.
Prediction of Pressure Phenomena in Dual-Chamber High-Low Pressure Guns and Its Application to Structural Analysis
It is well known that zero-dimensional internal ballistics codes have serious limitations for the prediction of the phenomena that occur in dual-chamber high-low pressure guns. In this paper, pressure-time calculations within the stabilizer of a 120 mm mortar bomb are performed by using an analytical model based on conservation laws. These theoretical results are compared with experimentally obtained pressure-time curves and applied to structural analysis carried out by using ANSYS software in order to evaluate the influence of pressure in dual-chamber high-low pressure guns. Under firing conditions, the material undergoes big pressure rises in very short time periods. The dynamic stress sustained by the material is simulated. As a result, it is found that the material has a very different behavior to that shown by the action of static strains.
BARTOMEU GARRIGA I TRULLOL, GUILLERMO JENARO GARRIDO, SERGIO OLIVA OLIVA, RAMON A. OTON-MA
Agglomeration of Micro- and Nano-RDX and Its Influence on Properties of NG/TEGDN/NC Propellants
In this paper, agglomeration of micro- and nano- RDX and its influence on properties of NG/TEGDN/NC propellants were studied. Particle sizes of loaded RDX were 0.34μm, 0.97μm, 3.70μm and 7.6μm. The propellants were prepared with RDX directly mixed or dispersed uniformly in advance, and with ethyl acetate and the mixture of acetone and alcohol, at 35 ℃ , respectively. Combustion characteristics and mechanical properties were investigated by using standard closed vessel and universal material testing machine at 20 ℃ . The fracture surface was characterized using scanning electron microscope. Results obtained indicate that both 0.34μm and 0.97μm RDX were agglomerated or had a crystal size growth in the propellants manufactured with all the three solvents, while worse with ethyl acetate. The burning rate pressure exponent and tensile strength decreased with the decreasing RDX particle size, while the impact strength on the contrary, except that the impact strength of propellants with 0.34μm and 0.97μm RDX was worse than that with 3.70μm and 7.6μm RDX due to the influence of agglomeration and that with 0.34μm dropped down obviously.
BINBIN WANG, XIN LIAO, ZESHAN WANG, YOU FU
The Impact of Materials on the Launch Dynamics of Small Caliber Projectiles
Traditional small caliber projectiles employ a copper based jacket and a lead alloy slug. These materials are low cost, readily available, adaptable to a variety of manufacturing techniques, and result in a low cost to the consumer. The manufacturing usage and postconsumer disposal of lead and lead-based products is a growing environmental concern worldwide. As a result it is extremely possible that future small caliber projectiles will utilize environmentally friendly materials. In this research the impact of materials on the launch dynamics of small caliber projectiles will be examined. Computational mechanical modeling will be conducted to determine the impact that material properties have on the launch dynamics and predicted dispersion. The modeling will examine typical commercial two-piece projectiles in two calibers 5.56mm and 7.62mm. The results of the study will discuss the in-bore balloting behavior and predicted dispersion for the lead and green projectiles of differing material properties.
Coupling Vibration Model of In-Bore Balloting
A concise computer code for in-bore balloting of APFSDS is formulated. The basics of the model is that long rod was taken as a Bernoulli-Euler beam with freefree ends. Forces are distributed in accordance with the natural mode of vibration. This allow us to neglect ambiguous contact between sabot and rod. Tube is simulated as a cantilever of Bernoulli-Euler beam having gravity droop, regional warp of the centerline. Vibrations of gun tube are excited by Recoil Load, "Bourdon" pressure, Projectile collision, and Bearing support. This analytical model is formulated and operated on a personal computer. Time to calculate one shot is about 10 to 20 minutes and it is useful to evaluate system constituents.
Modelling of Cook-off Experiment for Small Arms Propellant in a Cooling Barrel Using Finite Element Analysis
Finite element (FE) analysis is a powerful engineering tool which can be used to solve a heat transfer problem in a complex geometry and assembly. In this paper FE modelling of a cook-off experiment apparatus is presented. The experiment apparatus is used to represents a cook off analysis for a propellant charge inside an unconfined 7.62 mm brass cartridge case surrounded by a hot barrel which is naturally cooled by convection. A 2D axisymmetric FE analysis based on a 3D CAD model of the actual experiment apparatus assembly is carried out. The kinetic parameters of the propellant are applied into the analysis in the form of tabular data as the heat generation input. It is shown that by using proper input parameters for the apparatus and decent curve fitting of kinetic parameters for the propellant inside the cartridge case, a good agreement with the time to cook-off data from experimental results can be achieved. The time to cook off in a hot barrel is important and critical for operational success.
AMER HAMEED, BIDUR KHANAL, PHILIP PITCHER
Continuous Solvent-free Extrusion of Propellant for 35 mm Calibre Ammunition
In the frame of the evaluation of new 35 mm calibre projectiles, a propellant was manufactured by using a solvent-free continuous twin screw extrusion process. This was developed for the manufacturing of JA-2 equivalent gun propellant for large calibre ammunition [1]. In order to obtain the required combustion rate, a significantly smaller web size, and hence smaller grain size, of the 19-perf propellant grain is required than for the JA-2 equivalent propellant. For this purpose a new die technology was developed and applied. The firing test results showed excellent reproducibility, which is attributed to the homogeneity of the propellant composition and smooth and reproducible flame spreading over the propellant bed. These results demonstrate the applicability of a solvent-free and continuous manufacturing process for propellants used in medium calibre ammunition.
Simulation of Asymmetric Shot Start in Small Caliber Ammunition
Recent short-barrel experiments have indicated that primer ignition of small caliber ammunition is sufficient to begin projectile motion and engraving. High-speed video of these experiments also reveal that the early projectile motion is not symmetric with the nominal gun bore centerline. This early motion can lead to asymmetric engraving and has the potential to produce a mass asymmetry in the projectile leading to decreased accuracy due to increased dispersion. In this work the early motion of the projectile is simulated in order to determine the magnitude of any mass asymmetry resulting from the asymmetric shot start. The simulations indicate that the asymmetric shot start results in a modest engraving asymmetry and therefore a small mass asymmetry.
Research on Pressure Calculating of Propellant Gas with Simple Extended Corresponding State Principle
Focused on the limitation of the virial equation, which is caused by calculation of the virial coefficients, a simple extended corresponding state principle (SE-CSP) was introduced in this work. Based on a corresponding state equation including three characteristic parameters, another extended parameter was introduced to describe the second virial coefficient expressions of the main products of propellant gas. Comparisons predictions of this work and the closed bomb tests show that the extrapolated revised SE-CSP virial expressions are appropriate for the maximum pressure calculation of propellant gas in high temperature and pressure in constant volume. This method provides a convenient and efficient method in practical virial coefficient calculation without complicated molecular model design and integral calculations.
Numerical Study of the Effect of MHD Accelerator Technology on the Thrust Augmentation in Pulse Detonation Engine
The gas-liquid two-phase detonation model with magneto-hydro-dynamic (MHD)accelerator was established to study how the MHD accelerator technology affects the augmentation in Pulse Detonation Engine. The ignition, detonation initiation, detonation propagation and blow-down of Pulse Detonation Engine with MHD accelerator were calculated using the CE/SE method. Four Runge-Kutta was used to deal with the source term involved in chemical reactions. The mechanism of thrust augmentation of MHD accelerator was revealed. The effect of MHD accelerator on pulse detonation engine’s propulsion performance under different factors was analyzed. Results show that the deduced CE/SE method can be efficient to calculate the Pulse Detonation Engine with MHD accelerator. The MHD accelerator technology can be applied to the thrust augmentation of Pulse Detonation Engine. Potential performance gains with the plug-convergence-diverging MHD accelerator device. The calculation results have guidance function for the performance optimization design and the experiment of Pulse Detonation Engine.
High Velocity Gun Launch Fragment Impact Studies and How Events Can Go Very Wrong
High velocity fragment impact studies have become an important factor in the testing of insensitive munitions (IM) to ensure compliance and to demonstrate the safe use of munitions, in an operational requirement. A 40mm calibre, high velocity long gun system has been developed by QinetiQ, to meet the NATO STANAG 4496 standard high velocity fragment impact test requirement. However, it uses an internal ballistic (IB) solution which is optimised for the higher velocity as defined in the STANAG document. A 30mm calibre gun system is used to meet the lower velocity fragment impact test requirement. Whilst the fragment’s impact velocity when using the 30mm gun system can be pushed to achieve impact velocities of ~2000m/s, there is a distinct gap in the ability to achieve terminal velocities between 2000m/s and 2530m/s using these two gun systems. To understand a munition’s reaction phenomena by fragment impact between these two figures would be a very desirable option and would be beneficial to the munition designer from the IM perspective. This paper will report and discuss some of the experimental results and the problems encountered during high velocity fragment impact studies with powder gun systems.
A Novel Technique to Measure Small Caliber Projectile Balloting Effective Burning-rate Inhibitors in AP/Al/HTPB Composite
The US Army Research Laboratory (ARL) has a continuing program to investigate interior ballistic parameters (i.e. propellant charge, barrel leade, primer composition and output) which may contribute to overall performance (e.g. muzzle velocity and dispersion) and variability. In the area of in-bore projectile balloting there have been analytical studies that link balloting to ‘jump’, but small caliber data for current projectiles is lacking. Studies in large and medium caliber have employed techniques that are difficult to transfer to small caliber. The primary objective of the research to be presented here is to explore and exploit a novel quantitative technique to measure the degree of projectile balloting as it travels down bore. The basis of the technique is to soft catch projectiles and measure engraving marks.
Two kinds of new effective burning-rate inhibitors, the energetic inhibitors and chemical-modified quaternary ammonium salt, for AP/Al/HTPB composite solid propellant have been developed. There are energetic groups and inhibitor groups in the molecules of the energetic inhibitors. The burning rates of the propellant with only 0.5 percent of the chemical-modified quaternary ammonium salt can be decreased remarkably. Meanwhile, the alkalescence of the quaternary ammonium salts was chemically modified to meet the requirement of compatibility in the propellant. These two kinds of inhibitors can not only decrease the burning rates but also restrain from explosion heat loss of the propellant effectively.
TONG BAO, XING ZHOU, ZHI-BING SONG, FAN HU
Parameter Analyses of Two Dimensional Heat Transfer of Gun Barrel
This paper simulates the 2D heat transfer of gun barrel by using FVM. An interior ballistics code was implemented to FLUENT to provide the convection boundary condition of the inner wall. Temperature, heat flux and heat transfer responses of inner wall at different locations and 2D temperature distributions were given. Effect of some interior ballistics parameters (charge weight, web thickness and force capacity) were discussed. Force capacity of the propellant shows the biggest effect on the heat transfer. When these factors increases by 5%, the increment of the maximum temperature near the origin of the rifling will increases by 2.5%, -2% and 8%, respectively. The exterior water cooling method was also analyzed to show its effect on the temperature responses, temperature distributions and heat transfer. During the 30 rounds, the cooling water took away heat of 2.26MJ/m2, about 21.67% of the total heat transfer of the gun barrel received from the propellant gas during the interior ballistics period.
Influence of Gun Bore Structure on the Performance of Interior Ballistic Process
In order to find out the influence of gun bore structure on the performance of interior ballistic processes, a modified interior ballistic model is established. In the model, the energy conversion of an interior ballistic process is analyzed in detail, and many components of energy are absorbed into an item that is expressed in the form of work output from propellant gas system. With the combination of computational solid mechanics and fluid mechanics, the modified interior ballistic model can be solved without the use of a coefficient of energy losses. The relationship between the shot-base pressure and the mean pressure is derived under the hypothesis of Lagrange. And the projectile is directly pushed by the shot-base pressure and resisted by forces that source from the contact between a projectile and its barrel. In this paper, the classical interior ballistic model is modified firstly. Then the twist angle of the rifling and the forcing cone angle are selected as characteristic parameters of the gun bore structure, and their influences on the performance of interior ballistic processes is studied. In order to characterize the influences, a coefficient of energy losses is directly defined. Based on the simulated results, the coefficient is calculated and the influences are analyzed.
Study of Stick-propellant Gun Interior Ballistic Considering Internal Perforation Erosive Burning
Compared with the conventional randomly packed grain charge, a stick propellant charge system has advantages in higher loading density, better flame-spreading and lower pressure waves. To analyze the unslotted single-perforation stick propellant combustion, a new interior ballistic model considering the interior perforation erosive burning and the external gas region is established in this work. This model considers three regions, including the two-dimensional axisymmetric internal perforation gas region, the solid propellant region and the external behind the projectile base gas lumped parameter region. According to the numerical simulations, the model shows the ability to describe the stick propellant combustion process, as well as to reveal the internal perforation field. Erosive burning has a significant influence on the ballistics process, and it mainly occurs in the initial period of the ballistic cycle.
Numerical Simulation of Launch Process of Stacked Projectile Weapon Considering Muzzle Flow Field
One of the key problems of numerical simulation of serial launch process of stacked projectile weapon is accurately simulating the coupling effect between the propellant gas and later projectiles. However, the interior ballistic numerical simulation can only obtain the motion law of the later projectiles accurately, before the projectile head reaches the muzzle. And the velocity increments, caused by muzzle flow field, also can be not obtained. In order to study the motion law after the projectile head flies out of muzzle, the launch process of two serial launched projectiles, considering muzzle flow field, is numerical simulated by FLUENT, coupled with interior ballistic simulated code. The numerical simulation results show that the formation process of the bottle shock of the second projectile is different, comparing with the first projectile. The variation law of projectile head resistance of the second projectile is consistent with the one calculated by one-dimensional two-phase reaction flow interior ballistic model, before the projectile head reaches the muzzle. After the projectile head flies out of the muzzle, the projectile head resistance decreases rapidly, but then it is not always equal to zero. After the projectiles leave the muzzle, the velocity increments are mainly determined by muzzle pressure.
A Novel Mid Wall Cooling Channel Design for Large Calibre Guns
It is widely observed that extremely high thermal loads are experienced in large calibre guns with high rate of firing. These extreme thermal load results in rapid barrel heating, which in turn limits the duration of firing that can be sustained without reaching the cook-off temperature for the propellant. After reaching the cook-off temperature, the gun barrels require long duration to cool down before commencement of next firing cycle, which is unacceptable in a combat situation. The investigation proposes integral mid-wall cooling channels in the gun tube to achieve a high rate of fire. A FEA model was developed to simulate a high rate of fire scenario, which demonstrated that the proposed mid-wall cooling system can yield 10 rounds per minute without reaching cook of in a large calibre system like 155/52mm Artillery Gun systems.
RAJEEV MOHAN BHATNAGAR, BIDUR KHANAL, AMER HAMEED
Factors Affecting Bore Resistance in the Structural Analysis of Interior Ballistics
During analysis of new or existing ammunition the bore resistance profile is of particular importance as it gives the engineer valuable insight into tuning propellant parameters and charge loads. Finite Element Analysis can be a useful tool in estimating bore resistance profiles of conceptual ammunition before the rounds are prototyped and tested. However, many assumptions go into launch models that can affect the bore resistance profile obtained. This presentation covers many of the assumptions made during launch modeling and features within Finite Element Analysis and compares their influence on the obtained bore resistance curve. Factors such as rigid vs. Lagrangian elements, surface smoothing, mesh densities, helical meshing techniques, and results across multiple software packages will be evaluated.
Influence of Chamber Misalignment on Cased Telescoped (CT) Ammunition Accuracy
As part of a research program, it was desired to better understand the impact of the rotating chamber alignment with the barrel throat on the precision and accuracy of a novel Cased Telescoped (CT) ammunition firing rifle. In order to perform the study, a baseline CT ammunition chamber which was concentric with a Mann barrel bore was manufactured. Additionally, six chambers were manufactured with an offset relative to the barrel bore. These chambers were used to simulate a misaligned chamber relative to the bore axis. Precision and accuracy tests were then performed at 200 m in an indoor range under controlled conditions. For this project, 5.56mm CT ammunition was used. As the chamber axis offset relative to the gun bore was increased, the mean point of impact was displaced away from the target center. The shift in the impact location is explained by the presence of in-bore yaw which results in lateral throw-off and aerodynamic jump components. The linear theory of ballistics is used to establish a relationship between the chamber misalignment and the resulting projectile mean point of impact for a rifle developed to fire CT ammunition. This relationship allows for the prediction of the mean point of impact given a chamber misalignment.
45 mm Ignition Study with a CAB-LOVA Gun Propellant
The Electro-thermal Ignition (ETI) of gun propellants has several advantages compared to the conventional methods using e. g. black powder. One aspect is the capability to control the energy input into the propellant bed. Further on a more efficient ignition of insensitive and difficult to ignite propellants is expected. This paper describes a study with the CABLOVA gun propellant NL008 where ETI and Black Powder were used for propellant ignition in a 45 mm laboratory gun. The ignition behavior at two loading densities and different energies was studied in order to compare both ignition methods.
DENNY ÅBERG, DOMINIK RAKUS, RUDI HEISER
Pressurized Air Catch System (PACS) for Gun-Fired Projectiles
CYNTHIA HOLLAND, W. DAVID HOUCHINS, DAVID HUBBLE, WAYNE CHEPREN, JAMES FETSKO, MARC BASSET
Investigation into the Coating and Desensitization Effect on HMX of F2604-2 and DOS Composite System
This paper explores HMX coating and desensitization coated by of F2604-2 binder and DOS plasticizer. The compatibility issue was firstly investigated by VST, which was often neglected in literatures. The structure and mechanical sensitivity of raw and coated HMX samples were investigated by SEM and impact and friction sensitivity test, respectively. VST result proves that all materials used in question are compatible with each other. Compared with that of raw HMX, both impact and friction sensitivity of HMX coated with 1.0 wt.% F2604-2 and 1.0 wt.% DOS decrease significantly, where the drop height (H50) is increased from 18.0 to 50.6cm, and the friction probability is reduced from 100 to 36%.
XIN-YING ZHAO, QIU-HAN LIN, TONG XU, BO-LIANG WANG
Towards a Better Assessment of Acoustic Vector Sensors
In combat situations it is important to locate the positions of enemy marksmen. In principle, it is possible to determine these using microphone arrays. An interesting alternative is using acoustic vector sensors (AVS) instead of conventional microphones. AVS, such as the Microflown, measure the flow of air particles to determine the direction of the sound source. To allow for comparison with these AVS, experiments were performed, in which the direction of the sound source is determined using two measurement condenser microphones. The direction of arrival estimation was accurate to ±1.8 degrees. This is less accurate than the advertised value for the Microflown acoustic vector sensor, viz. less than 1.5 degrees. These measurements can serve as a baseline for accuracy tests with AVS. Similar independent research should be performed with acoustic vector sensors, in order to be able to assess the manufacturer’s claims.
Preliminary Findings: Will Breast Implants Rupture if Body Armour is Struck?
During a non-perforating ballistic impact on to body armour stress waves are generated and propagate through the armour and underlying tissues. Prophylactic mastectomy is a procedure in which breast tissue is excised to reduce the chance of malignant change in females who have an increased risk of developing breast cancer. This paper presents preliminary findings on whether breast implants might rupture if a female police officer with implants was wearing armour and suffered a non-perforating ballistic impact on the breast region of the armour. No previous work in this area has been identified. Post-failure examination of the implants revealed that five out of seven implants tested ruptured; typically at a location towards the outer edge of the implant where the maximum radial strain developed. This preliminary work has initiated a more comprehensive study.
C. MALBON, J. BREEZE, S. HEPPELL, E. A. LEWIS
A Comparison of Fragment Simulating Projectiles and Real Fragments with Respect to Soft Body Armour Performance
Modern body armour is tested using fragment simulating projectiles (FSPs) not real fragments. In the UK, chisel nosed FSPs (CN FSPs) are used as part of a quality assurance regimen as they provide repeatability, consistency, standardisation and also allow comparisons to be made among armours. In this work a typical military (soft) body armour was tested using i) real fragments collected from Mortar Bomb 81mm HE L41 and ii) CN FSPs. Statistical analysis showed there was no linear correlation between real fragments and CN FSPs. CN FSPs behaved in a predictable manner and were not accurate representations of real fragments which behaved unpredictably due to the different shapes, sizes and masses. This observation provides insight into research exploring the use of CN FSPs to test the ballistic performance of typical body armour.
A. ASHMORE, J. DRAY, D. J. L. MCKAY, C. SAUNDERS, E. A. LEWIS, D. MILLER, M. TEAGLE, D. J.
Determination of the Efficiency of a Spaced Thin Layer Steel Target Against Small Caliber Ammunition
Ships have great internal volume with steel structure walls having a low thickness. On another side, in the unstable international field, vessels are able to be shot by kinetic projectile threat. We tried to estimate the protection capacity of steel structure plates with a low thickness against small caliber projectiles. From experimental results, we elaborated a simple analytical model to determinate the ballistic limit velocity. We can show that the energy associated to the bending phenomenon at the end of the perforation decreases when the yield strength of the target material increases. This model has been used also for inclined plates. It is then able to take account of different targets made of spaced thin layer steel plate according to the configuration met inside ships.
Phase Transformations in Glass Associated with Hyper-Velocity Impact and Implications in Constitutitve Modeling
Collateral Concerns in Conjunction with Weapon Effects
NATO requires the assessment of weapon effects including collateral damage in advance of weapon engagements. In Germany BAAINBw K1.2 is responsible for providing the respective methodologies and data. On behalf of BAAINBw K1.2 IABG develops UniVeMo (Universelles Verwundbarkeitsmodell) the accredited German standard vulnerability/lethality evaluation tool. This paper provides an overview of the status of current German standard methodologies that address the subject collateral damage comprising the areas • Fragment risk to persons in the open and in vehicles • Crater ejecta risk to persons in the open • Risk to persons in a building
, REAS DOERR, DANIEL ROSSBERG, ALBRECHT BONGARTZ
The Use of Composites for Blast and Fragmentation Protection of Selected Infrastructure
Infrastructure application such as Refineries and Petrochemical Plants, Power Plant, or off shore Vessels, often require blast and fire resistance protection, and in some cases fragmentation protection as well. Contemporary threats to be taken into account involve fire or gas explosion which may accidently happened as well as attacks by blast and fragmentation warheads integrated in several types of rockets, mortars and fragmentation generated by artillery HE blast shells. Ballistic protection add–on or predesigned blast and fire resistant existing solutions are needed vastly for crew survivability. The main limitation for such solutions is their weight, especially when such solutions are supported by existing base structure. In this paper the authors will show the use of fiber composite add-on protective curtains, as well as alternative hybrid metal composite light weight wall construction with comparison to conventional steel wall , designed to certain ballistic protection requirements, including numerical simulation and live field tests evaluation tools, then derived some practical conclusions.
NIMI SHAPIRA, ZVI ASAF, TAMIR BLASS, BARRY L. BINGHAM, RAYMOND H. BENNETT
Artillery shrapnel is a kind of large area ammunition. The essay began from the analysis of the firing errors when shrapnel is used. The composition error of transmitting gun shrapnel is one more than ordinary shell. There are three parts of the firing error. The essay put one mother projectile throwing N bullets into one ordinary shell. We can calculate the damage area of shrapnel as the ordinary shells.
An Experimental Study Investigating the Response of Bolts to Ballistic Events
Bolts are a common method of integrating vehicle applique armor on ground vehicle platforms. During ballistic events, bolts closest to the impact location have the potential to stretch and fracture as a result of the large forces imparted to the armor panels. Fractured bolts no longer constrain the armor as required for ballistic protection and may cause vehicle vulnerabilities. Tank-Automotive Research, Development, and Engineering Center (TARDEC) initiated a study to quantify the forces in the bolts during a ballistic event and explore the factors that influence the forces. This was successfully achieved using instrumented bolts. Multiple configurations were tested to identify trends in the bolt response. The approach was successful in measuring the transmitted forces and identifying variables that influence the magnitude of response. This paper summarizes the testing that occurred and the results of the effort.
Investigation into Ballistic Performance of Environmentally Conditioned Ultra High Molecular Weight Polyethylene (UHMWPE) Composite Armour
In this work, the long term ballistic stability of UHMWPE composites were investigated by the accelerated ageing of samples in an oven, to replicate the hot conditions that can occur in military vehicles when used in hot climates. The aged specimens were periodically removed from an oven at 60oC and subjected to ballistic impact from 5.56 x 45 SS109 projectiles, in both the hot and cooled condition, in order to determine the specimens V50 ballistic impact velocity and thus identify any change in ballistic performance against exposure time. The ballistic results for aged glass fibre composites in a thermosetting resin were also determined allowing conclusions on a multi-layer armour system to be made. The completed work demonstrated that, for the systems investigated, ageing did not reduce the resistance of the fibre reinforced composite materials to ballistic penetration for assessed projectiles.
Design of Measuring Multi-physics Integrative Parameters Diagnostic Test System for Electromagnetic Launch
An experimental system of electromagnetic launcher (EML) always consists of a large-scale pulse power supply (PPS) and a railgun launch device. And it is a complex system, involving multi-physical fields, for example electric field, magnetic field, electromagnetism field, temperature field, stress field etc. The multi-physical measuring parameters are also needed to consider and obtain synchronously. A high accuracy measuring system for testing various physical parameter signals has been designed and developed to serve for the EML tests. A complete range of measurement methods about pulse current, pulse voltage, muzzle velocity, instant multi-spectral temperature measurement, fiber Bragg grating strain transient test, and imaging diagnostics, etc. has been studied and applied. It provides the effective experimental methods for mechanism researching and EML performance detecting.
YONG JIN, LONG LI, GANG WAN, ZHENXIAO LI, JINLIANG GU, YAN XIA, BAOMING LI
Research of Lethality Enhancement of a Kinetic Kill Vehicle Technology of Air Defense and Anti-missile Missile
The lethality enhancement of a kinetic kill vehicle is a cutting-edge technology of any air defense and anti-missile weapon system. Relying on the Xi'an Modern Chemistry Research Institute’s leading technology research platform of propellants, explosives, air defense and anti-missile missile, it was proposed to enhance the lethality of a kinetic kill vehicle scheme by linear explosive charge. The lethality enhancement of the kinetic kill vehicle technical parameters and damage effect index was calculated in detail. It was proposed to apply reactive materials fragments in order to improve the ability to impact and damage the target. The key technology and test results have been achieved and are summarized.
Multifunctional Concealed Bulletproof Vest—Development and Testing
The article presents the problem of designing and testing of multifunctional concealed bulletproof vest in which both soft and hard ballistic inserts are elastic and adjustable to the body of the user. The main challenge in the development process, was to create a hard ceramic-based armour system which meets the camuflage, flexibility and protection requirements. The vest must be as lightweigt as possible while maintaining the expected protective area and ballistic performance against various threats. Vest inserts construction is described and material selection proceedure is justified. The results of firing and stab resistance tests based on polish and foreign standards are presented. Soft fiber-based ballistic inserts were fired with the use of 7.62x25 mm TT and 0.44 Magnum SJHP pistol ammunition as well as fragment simulating projectiles (FSP). Flexible ceramic-based panels were tested with 5.7x28 mm SS190 pistol ammunition with increased penetration capability. Special attention was paid to the problem of ballistic resistance of the flexible inserts at the points of inflection. Additionally selected zones of the vest were tested for stab-resistance.
WIESLAW HABAJ, MIKOLAJ BOGAJCZYK, PAWEL PODGORZAK
The V50 Approach Revisited: Application of the Brownian Motion Theory
A common method to assess the ballistic resistance of an armor material or system is the V50 approach. Although the V50 value is in itself a useful and acceptable indicator of ballistic resistance, it is shown in this research that the usage of V50 and s50 to describe the perforation probability as a function of impact velocity is fundamentally flawed. This possibly leads to large errors when these two parameters are used to evaluate very low or very high perforation probabilities, as is done for the former in the case of Critical Perforation Analysis. Two alternative paths are presented here, a first path based on ab initio Monte Carlo modeling to illustrate the inherent limits to the current V50 methodology, and a second path based on the Brownian motion approach which might be a path for the future to better assess very low or very high perforation probabilities.
AXEL LENOM, BEN LAUWENS, BEYA TAHENTI, MARC MALDAGUE, MARC PIRLOT
Engineering Tool for the Evaluation of Global IED Effects
The detonation of an IED near a military vehicle induces different damage effects on the vehicle and its occupants. The following work presents an approach for a fast analysis of global IED effects on vehicles. The physical modelling is based on analytical formula and empirical data that describe the momentum transfer of a detonation on a nearby structure. The software itself has a modern GUI that allows the generation of the vehicle structure and the threat scenario together with an interactive analysis of the simulation results. The engineering tool is validated with small size generic vehicle tests where jump height and the vehicle motion are compared.
V. DENEFELD, A. STEINBRENNER, A. HOLZWARTH
Modeling the Influence of Soil Characteristics on the Blast Intensity of Buried Explosive Charges
Geotechnical soil parameters and soil moisture content in particular, were found to have a significant effect on the total impulse inflicted on a structure by a buried explosive charge [1, 2, 3]. Previous research conducted by Plasan [6] quantified the blast intensity of a buried explosive charge in graded gravel by two measuring routines: steel plate deformation and flying plate. In the study, which was presented in previous IBS conference [7] an additional soil types and soil parameters where examined while utilizing improved measuring apparatus. The experimental study was conducted on three different soils: sand, clayey sand and graded gravel with silt. The blast intensity was measured by mine impulse pendulum (MIP). Results obtained indicate that saturation ratio is the most dominant factor influencing buried- charge blast impulse magnitude. Sequential to experiments, a numerical investigation was performed in order to characterize the blast and to relate its characteristics to soil type and properties. Finite element (FE) explicit simulation was conducted using Ls-Dyna. In the numeric model, impulse load was inflicted to the MIP by implementing both software embedded blast subroutines, i.e. *LOAD_BLAST_ENHANCED and *INITIAL_IMPULSE_MINE, by Arbitrary Lagrangian Eulerian (ALE) formulation and DES with Particle Blast method. In order to accurately simulate buried charge impulse load, it is required to use either ALE formulation Particle Blast or to scale reflected pressure pulse duration. The correlation of the different blast modeling methods to the test results for the different soil types and saturation degree will be presented and discussed.
ODED DRORI, GUY GOLAN, ITZHAK KUCHUK KATALAN, MOSHE RAVID, NIMI SHAPIRA
Experimental Investigations on Dynamic Back Face Deflection Caused by Ballistic Impact on Combat Helmets and the Effect to the Human Skull
Nowadays ballistic protective helmets are made of synthetic composites like paraaramide fibers and advanced laminate materials (UHMWPE). The absorption of impact energy occurs through plastic and elastic deformation. The so-called Â´dynamic back face deflections´ caused by the kinetic energy of the projectile during the ballistic impact can generate serious, irreversible traumatic head injuries. That leads to the question: Which cranio-cerebral injuries are to be expected due to a bullet impact without penetration and which clinical implications for the wearer of the helmet can arise? This paper presents a first prototype of a head-shaped measurement setup for ballistic impact tests of combat helmets. Shooting tests were conducted and force-time sequences caused by the helmet-head contacts during the impact were obtained. The force values of additional trials are planned to be loaded onto a 3D human head finite element model. The objective of the work is the biomechanical interpretation of the simulations. They shall allow conclusions on possible cranio-cerebral injuries and clinical implications.
Physical Mechanisms for Near-Field Blast Mitigation with Fluid Containers: Effect of Container Geometry
The use of external fluid containers for reducing the deformation of flat steel targets subjected to near-field explosive blast loading was investigated through experimental testing and numerical simulation. Water-filled containers of varying height and width were assessed. The best performing container provided a 65% reduction in the peak dynamic deformation of the steel target, a significantly greater reduction than that provided by a steel applique panel of equivalent areal density. The container geometry was found to have a significant impact on the result, with differences in deformation of 100% observed for containers with varying dimensions but the same total volume. Numerical simulations performed in ANSYS® AUTODYN® highlighted that the timescale of the loading was too short for container breakup. Hence momentum extraction and evaporation are not considered relevant mitigation mechanisms. The major mitigation mechanisms were found to be shadowing and rarefaction waves.
A First Order Method for Estimating Lethal Areas for Fragmenting Munitions
There is no specific definition for “lethal areaâ€ in the NATO glossary of terms and definitions, so one is proposed and developed. Further, this paper outlines a methodology that is based on a number of simplifying assumptions, that allows a fairly straightforward approach to predicting lethal areas for fragmenting munitions, ranging from large calibre high explosive (HE) shells to hand grenades and automatic cannon rounds. The advantage of this methodology is that it can be used to compare either similar munitions, e.g., bursting shells, or more disparate munitions, such as shells with anti-personnel grenades or anti-personnel mines. The paper also provides two worked examples: the 105 mm M1 HE round, for which a calculated lethal radius of 10.6 m compared favourably with a quoted value of 9.6 m and for the M26 hand grenade the corresponding values were 6 m and “greater than 5 mâ€.
Characterisation of Armour Properties for the Prediction of Rupture in Localised Blast Loading
Material characterisation and numerical blast testing of four steels was performed to identify the key mechanical properties dictating their rupture threshold under localised blast loading. Tensile testing of cylindrical and notched samples was performed and the Johnson-Cook (J-C) strength and fracture parameters were calculated. Accounting for the change in stress triaxiality during the testing provided greater accuracy in replicating the tensile test results. A numerical modelling evaluation of each material under localised blast loading showed that the highest strength, lowest ductility steel provided the highest resistance to both deformation and rupture. The energy absorption to fracture in a notched tensile test was shown to correlate with the blast threshold of the steels. The material blast rupture threshold was also found to correlate well with the flow stress at fracture calculated directly from the J-C material model.
The Overmatching of Military Soft Body Armour: Preliminary Results
Modern military soft body armour provides protection from fragmenting munitions, which are the major cause of injury in warfare. Protection from high-velocity (rifle) ammunition is usually provided by ceramic faced / composite backed plates. There is a growing interest in what happens when body armour is overmatched i.e. it is perforated by a threat that it is not designed to protect the user from. In this work, a military soft body armour was overmatched with 7.62x39 ammunition (steel core, lead nose; produced in 1983; Sellier and Bellot, Zbrojovka Vlà sim, Czechoslovakia). The target was a combination of swine tissue (skin, underlying tissue, ribs) - gelatine (10 % by mass) - swine tissue (ribs, underlying tissue, ribs). The impact velocity varied between 524 m/s and 547 m/s (equivalent to an engagement distance of ~180-200 m). This paper considers whether the body armour affected damage caused to the target during an overmatching event.
D. J. CARR, M. TEAGLE, D. MILLER, A. MABBOTT, E. A. LEWIS
The Effect of an Air-gap Under Soft Body Armour on the Behind Face Signature
Modern police body armour typically provides protection from sharp weapons and low-velocity (handgun) bullets. It is recommended that the armour is worn against the body i.e. no air-gaps are present between the wearer and the armour. In the case of formed or shaped armours it may be that airgaps exist (e.g. female specific armours in the breast region). Additionally some manufacturers are incorporating stand-off in their armour designs with the claim that these decrease thermophysiological loading on the user by increasing micro-climate cooling. In this paper the effect of stand-off (10 mm) on the measured back face signature (BFS) will be assessed. HG1/A+KR1 armour panels (400 mm x 400 mm) were mounted on calibrated #1 Roma Plastilina and impacted with 9x19mm FMJ (Dynamit Nobel DM11A1B2) ammunition (365 m/s ± 10 m/s). The resulting BFS was measured and compared to impacts on the same type of armour panels with no air-gaps.
Complex Bullet Interactions: An Experimental Study of Upper Leg Inuries to Demonstrate Ballistic Modelling in Multipart Limb Structures
Significant work has been undertaken characterising gelatine as a tissue simulant for ballistic testing, the human body however also includes skin and bone within the system. This paper investigated the effect of including bone and skin simulants to represent the thigh on bullet trajectory and temporary cavity. Entry and exit wounds were also compared. 9x19 mm FMJ pistol and 7.62x51 mm NATO rifle ammunition is used to complete firings at a series of targets including gelatine block and bone-gelatine models with a number of skin simulants. Shots are fired with trajectories that pass through the bone and close to the bone for comparison. All firings were recorded with high speed video allowing analysis of the temporary cavity. The results from the firings are presented and discussed. Distinct temporary cavities caused by the presence of bone and skin simulant are described for both through and passed bone cases compared to 10% gelatine only blocks.
D. J. CARR, C. O’KEEFFE, A. E. HELLIKER, D. MILLER
Fuel Tank Vulnerability to Shaped Charge Jet
The response of a fuel tank for armored vehicles attacked by a PG-7V was experimentally investigated. Free field tests as well as tests with the tank mounted to a pressure vessel were conducted. In the free field tests the reaction of the tank was examined by high speed and normal speed video. In the pressure vessel tests additionally pressure and temperature were measured at different locations inside the vessel. It was found that combustion of the fuel occurs independent from fuel type and impact point, but the intensity of the combustion seems to be higher if the shaped charge jet strikes the ullage. Further, the temperature of the fuel as well as of the surrounding surfaces was identified as a crucial factor for the occurrence of sustained fires.
ERNST ROTTENKOLBER, WERNER ARNOLD, OE MAHN MOON
The Study of a Human Head Simulant’s Dynamic Response to a Blast Wave
The prevalence of body armour and helmets in military forces combined with the availability of combat medical support and timely evacuation of injured soldiers has increased the survivability rates of those who have been exposed to blast. Despite this, the incidents of traumatic brain injury (TBI), as a result of primary blast, have been described as the ‘signature injury’ of modern warfare. The physical interaction between a blast wave and a human head is not well understood and there is some conjecture as to whether helmets are attenuating or amplifying the blast effects on the human head. The aim of this study was to improve the understanding of the interaction of primary blasts on the human head with different attachments such as a helmet and face shield.
Pre-stressed Plates as a Mechanism to Provide Additional Under Belly Blast Protection
The use of curved pre-stressed plates is investigated as this provides a possible additional mechanism to resist both initial folding and later structural collapse. Numerical modelling in Autodyn® and empirical calculations based on the Westine model were used to determine starting conditions for the explosive trials. Trials were conducted in which plates were pre-stressed by the imposition of a large bending moment from two parallel sides resulting in a tensile stress on the outer surface facing the blast. Tests were conducted at approximately one third linear scale using target plates of 500mm x 500mm and a charge of between 100g and 250g buried in dried sand was used to load them. Unstressed but curved plates were tested and then compared to similar shaped curved plates with an imposed bending stress equal to the yield stress or ultimate tensile stress of the plate material.
ASHLEY MANNING, JOE CAINE, JAMES BEADLE, ALAN PEARE, IAN HORSFALL
Rheological and Energy Absorption Properties of Backing Materials for Measurement of Behind Armour Blunt Trauma
Behind Armour Blunt Trauma (BABT) is the impact experienced by the body wearing armour, when subjected to a non-penetrating projectile. BABT is measured by the indentation of armour (Back Face Signature or BFS) on a backing material made of soft clay. The clay is considered to be tissue simulant which provides a correlation between BFS and BABT. The correlation depends critically on the choice of backing material, loading conditions, and its history. The applicability of clay as a tissue simulant to measure BABT is not straightforward as the viscoelastic response of human tissue and clay are different. Different materials can give different responses based on their viscoelastic properties. This paper describes the thermo-rheological and energy absorption studies conducted at Terminal Ballistics Research Laboratory, Chandigarh on two different backing materials. The study was conducted to find the differences in viscoelastic behavior and the subsequent differences in BABT.
AJAY KUMAR, IPSITA BISWAS, SANJEEV VERMA, EHTESHAMUL ISLAM
Parameters Optimization for Numerical Effectiveness Determination of Fragmentation Warheads Aginst Land Vehicles
Lethality and vulnerability analysis is especially used to assess the destructive effects that weapons have on targets. Depending on the studied part of the technical field, the calculations to be performed are not the same. As regards the effectiveness determination of fragmentation warheads against land vehicles, it requires a large number of random calculations. We focus on optimizing the calculations parameters in order to reduce the computing time that can be very long in some cases. The priority parameters studied are the number of times the detonation of the warhead is simulate in each cell of the lethal area matrix, the size of the cells and the minimum mass fragments considered.
Fast Moving Tungsten Rods Encountering Blast Waves
Results are presented concerning the fragmentation of fast moving tungsten rods under blast loading. The rods were the penetrator part of 30 mm caliber APFSDS rounds. The blast was produced by the detonation of a static spherical explosive charge ranging from 50 g to 500 g TNT. Trajec- tory, yaw angle, velocity and damage of the rods were determined with usual instrumentation for dynamic tests (cardboards, radar, X-ray flash photography and high-speed images). The observed effects depends on the mass of explosive, the lateral distance from charge to trajectory and the location of the first impact of the blast along the projectile. The analysis of the experimental data shows that damage threshold is given by a scaled lateral distance. These results give some insight in the vulnerability of APFSDS.
JAN KELLER, RÉ KOCH, FRANÇOIS UBERTINI
Injury Characterization Due to Penetrating Projectiles
Simulation tools using fast-running model forms for armor ballistic performance and penetrating injury response, coupled to Monte-Carlo based probabilistic methods to account for the inherently statistical nature of threat engagement with a PPE armor solution and penetrating injury dynamics are being developed. A critical element to the evolving predictive capability is development of improved model forms that account for the complex interactions between the threat, armor, and human body. These improved models require validation data from appropriate experiments to insure accurate and representative simulation results, as well as the insights gained through analysis of experimental data. Thus to support the development of improved behind armor injury models, an experimental methodology was developed and executed in which the extent of injuries resulting from residual velocities of ballistic projectiles were directly measured; specifically dynamic pressure and strain during the wound cavity formation, collapse, and final depth of projectile penetration.
MATTHEW V. GRIMM, RORY P. BIGGER, JAMES F. MACKIEWICZ
Numerical Simulation for Traumatic Brain Injury Assessment
Traumatic Blast Injury (TBI) associated with the human head is caused by exposure to a blast loading, resulting in decreased level of consciousness, skull fracture, lesions or death. This paper presents the blast loading of a human head form from a free field blast with the end goal of providing insight into how TBI develops in the human head. The developed head model contains all the major components of the human head, the skull, brain: including the tentorium, flax and grey and white matter. A nonlinear finite element analysis was employed to perform the simulation using the Arbitray-Lagrangian-Eulerian (ALE) finite element method. The simulation captures the propagation of the blast wave through the air, its interaction with the skull and its transition into the brain matter. The model quantifies the pressure histories of the blast wave from the explosive source, to the overpressure on the skull and the intra-cranial pressure. This paper discusses the technical approach used to model the head and outcome from the analysis and the implication on brain injury.
AMAL BOUAMOUL, SIMON OUELLET, MANOUCHEHR NEJAD ENSAN
Bullet Impact and Slow Cook-Off Enhancement for a Small Thermobaric Warhead
Enhancements to a small thermobaric warhead were incorporated to improve the Insensitive Munition (IM) response to Bullet Impact (BI) and Slow Cook-Off (SCO). The munition currently does not receive a passing reaction for BI, SCO, or Fragment Impact (FI). The original plan was to address BI and SCO, the two worst ratings, however cost savings were realized and FI was also tested. IM technology integration included replacement of the baseline thermobaric material with a shock mitigating reactive lining system and the integration of a modified aft closure and aft closure vent cover. The warhead with the IM technology integration resulted in passing reactions in all three tests, BI, SCO, and FI. In addition to improving the IM response, it was important to maintain or potentially improve the thermobaric component of this system. The thermobaric performance was testing through the static detonation of the warheads in an instrumented two-room structure. While the predicted Blast Overpressure (BOP) lethality of the baseline verses the IM enhanced warhead were similar, the IM enhanced warhead exhibited a reduction in thermobaric performance.
The 81mm mortar fires a projectile that can reach Unmanned Arial Vehicles (UAVs also known as drones) and can thus provide a method for shooting them down. The suggestion is that the projectile can be launched on a ballistic trajectory until it reaches its highest point and can then engage a guidance system to steer itself onto the UAV. It is found that for the difficult case of fast UAVs flying at 100m/s the mortar is in range for over 100s. If the UAV is identified ahead of this contact then there is time to set up and lay the mortar prior to firing. The UAV can be attacked with fragments at distances of about 3 to 8m. This distance allows the specification for a guidance system. Optimization of fragments could reduce the burden on the guidance system.
Numerical Investigation and Optimization of Composite Armor Structures
In the security sector the partly insufficient safety of people and equipment due to failure of industrial components are ongoing problems that cause great concern. Since computers and software have spread into all fields of industry, extensive efforts are currently made in order to improve the safety by applying certain numerical solutions. This work presents a set of numerical simulations of ballistic tests which analyze the effects of composite armor plates. The goal is to improve ultra-high molecular weight polyethylene structures in order to be able to cope with current challenges. Of course, the maximization of security is the primary goal, but keeping down the costs is becoming increasingly important. This is why numerical simulations are more frequently applied than experimental tests which are thus being replaced gradually.
Investigation on Melting and Composition Gradient of W-Cu Shaped Charge Jet During Jet Formation and Penetration
Explosive experiments of W-Cu shaped charge liner were conducted, and the composition gradient of W-Cu shaped charge jet during jet formation and penetration were systematically investigated. Results show that during the jet formation process, the W-Cu jet maintains a good compositional homogeneity and has no compositional gradient, and neither Cu phase nor W particles of W-Cu jet melts. However, during the jet penetration process, there is a large adiabatic temperature rise in the impact area of W-Cu jet under the ultra-high pressure, which causes the melting of part of the Cu phase and part of the W particles. When the W-Cu jet impacts the target, the Cu phase melts first under high temperature. The melted Cu then flows around and forms a Cu-rich layer between the jet and target. This helps to reduce the diameter of the penetration hole. Solid W particles with high energy make a major contribution to penetration depth.
LIU JINXU, LI SHUKUI, CHENG XINGWANG, JIN HAIBO
Gurney theory calculates the explosive energy imparted to metal casings during detonation and fragmentation. This paper assesses relationships between Gurney theories and Hydrodynamic Work energy. Several relations found theoretically are compared with trials data. Aluminised explosives are included as part of this data set. This paper builds on the author’s work in establishing theoretical relationships between Gurney velocity, Gurney energy and Hydrodynamic Work energy for Gurney theories. An improved generalisation of both Cooper’s and Koch’s Gurney theories is derived, which is simple to apply and gives improved predictions. This transforms Cooper’s and Koch’s simpler theories into the more accurate Kamlet and Finger Gurney theory, by use of an explosive coefficient (fX), which is a function of the unreacted explosive density. The ratio of Gurney energy to Hydrodynamic Work energy using this methodology is shown as identical to that previously determined for Kamlet & Finger’s Gurney theory and typically is 62%.
Evaluation of the Effect of an Explosive Charge Closed to a Steel Structure Plate
The effect of an explosive charge closed to a structure plate is a strong loading for a ship. To be able to quantify the damage bred on a structure, we made any tests with a charge closed to a metallic plate. From experimental results, we elaborated an analytical model supposing a constant velocity for plastic hinge movement. From the Gurney’s relation which we modified, we are able to determinate the initial velocity transmitted to the structure plate and to estimate the gas mass flowing to the downward step after the charge detonation.
An Analysis of Double Layer Shaped Charges
Shaped charges have long been in civil and military use. Double layer shaped charges (DLSC) are a special type of cylindrical shaped charges in which the outer layer of the charge consists of high detonation velocity explosive while inner layer consists of lower detonation velocity explosive. DLSC’s have recently attracted the attention of some researchers. It has been previously claimed that the performance of a typical DLSC is superior to that of a similar ordinary shaped charge (OSC). However fresh experiments carried out for comparison of the ballistic performance of DLSC with the OSC reveal the opposite. The numerical simulation results presented in this paper also support the experimental findings that the use of concentric layers of the charges as main charge is not as efficient method to improve the performance of shaped charges, as has been supposed.
Experimental Study of Magnetic Field Inhibiting Rotation of Shaped Charge Jet Particles
A shaped charge jet (SCJ) will break up into many particles after it undergoes elongation in free flight. However, if breakup of a SCJ occurs, the particles cannot remain aligned with the SCJ axis, but start rotating because of the effect of asymmetric force and perturbation [1; 2]. The effective length of SCJ will be decreased because of its tumbling, and its ability of penetration could be decreased. The external magnetic field delaying the breakup of SCJ has been researched, but so far, few people focus on the magnetic field inhibiting tumbling of SCJ particles. This work provides the experimental study for further research on the inhibition of tumbling of SCJ. Because the slug is easy to observe, this work takes it as a research object to analyze.
ZHENGXIANG HUANG, XUDONG ZU, QIANGQIANG XIAO, XIN JIA
Application of an Electromagnetic Diagnostic Technique for In-Flight Shaped Charge Jet and Hypervelocity Particle Characterization
An electromagnetic measurement technique is used to augment the characterization and understanding of hypervelocity projectiles before impact. The paper includes a short description of the method, while focusing on its recent utilization for jet particles and gunlaunched hypervelocity projectiles. Data from the applied electromagnetic diffusion technique allowed both size and velocity characterization of particles from 0.5 mm up to 5 mm in diameter with velocities ranging from (but not limited to) 1000 m/s to 4000 m/s. This includes a series of experimental tests for method validation and calibration using light gas gun propelled laboratory projectiles as well as characterization of particles from a RISI Teledyne model RP-4SC small commercially available shaped charge. Techniques for narrowing the detection signal such as electromagnetic shielding and differential sensing enable measurements of multiple particles with separations on the order of 20 mm. Thus, we show that the presented method has potential to enhance ballistic studies by providing an additional technique to expand current hypervelocity projectile diagnostics, increasing capabilities in the area of in-flight characterization of projectiles before and during impact for dynamic material and validation studies. Part of the presentation given in the present paper is taken from a recent publication by the same authors [J. Appl. Phys. 118, 184901 (2015)].
Hollow cylindrical charges of PE4 were detonated. The charges had masses of 0.16 to 0.49 kg and a length to diameter ratio of 1/1 to 1/6. The circular hollows were of diameter 0, 0.01, 0.02 and 0.04 m. The charges were detonated from one end. The results showed that provided the correct ratio of charge mass, charge length to diameter ratio and distance are maintained the peak overpressure and impulse remain constant. This means that it is not necessary to know the size of the hole to predict the peak overpressure and impulse in the radial direction. For PE4 the peak pressure, P, is given by P = -251 (M(L/D)1/3R-3)2 +1677 M(L/D)1/3R-3 and the impulse, I, by I = 150 M2/3 R-1. M is the charge mass, L the charge length, D the charge diameter and R the distance from the charge.
Design and Commissioning of a Semi-Confined Blast Chamber
This extended abstract presents the design, test and analysis of the closure of a scaled cylindrical blast chamber. The blast chamber is a one-fifth dimensional size replica of the full-scale blast chamber (Emily). The blast chamber is semi-confined as one end is open. The scaled blast chamber is used to test concepts for closing the open end and allows the gas to vent at the same time. ANSYS AUTODYN calculated the pressure time histories for different closure scenarios. Comparing the results suggested a viable scenario, namely a structure consisting of a cylindrical disc and a frame positioned at the open end of the blast chamber. The structure and cylindrical blast chamber were subjected to scaled blast tests and the pressure results are presented and discussed.
Research on Driving Characteristic for Dual Charge of DNTF-Based Aluminized Explosive
By choosing two types of DNTF-based explosives with aluminum content of 5% and 20%, two kinds of the test samples with typical inner/outer dual charge structures were prepared. Detonation velocity and expansion process of the cylinder wall were measured by 50mm cylinder test. Energy release characteristics of different dual charge structures were analyzed and compared with that of single explosive charge. The results show that when inner layer of dual charge is high detonation velocity explosive, its detonation velocity is about the average of two kinds of single explosive charge, and the driving ability is enhanced significantly at the latter stage of expansion, so that it's Gurney coefficient is only 2.86mm/μs; when outer layer of dual charge is high detonation velocity explosive, its detonation velocity is slightly lower than single charge with high detonation velocity, and the detonation wave has obvious cohesion characteristics, so energy release rate of the inner layer is improved and the driving ability is enhanced sostenuto, which Gurney coefficient upgrade to 2.93 mm/μs.
Finite-Element Analysis Modeling and Simulation of an Aimed Cluster Warhead Based on Truegrid Software
An aimed cluster warhead is designed to have six surfaces on the radial direction. Each facet consists of many preformed tungsten balls aligned in rows and columns. The warhead is most frequently used on Surface to Air Missiles (SAM’s) and other point defence systems such as those dedicated to Counter-Rocket, Artillery and Mortar (C-RAM) use. Utilizing Finite-Element Analysis(FEA) TrueGrid software a model of the aimed cluster warhead was created.. It shows that TrueGrid software can build models such as an aimed cluster warhead with a lot of preformed fragmentations quickly, effectively and expediently. Using LS-DYNA FEA[Acronym exposition] software, fragment formation, flight characteristics and the penetration potential of the aimed cluster warhead were simulated based on four different detonation modes. The numerical simulation results show that the designed aimed cluster warhead can form fragments with a velocity of some 2,200 meters per second(m/s). These fragments showed a capability to penetrate a Duralumin target that was 30 millimeters (mm) thick at a distance of 50 metres (m) The modeling and simulation method of this paper will provide references for the design of aimed cluster warheads for use in SAMs and C-RAM platforms.
JIAN-WEI LI, RONG-XIN FANG, PEI-JUN ZHANG, ZENG-QUAN XUE, TAO YU, FEI TONG
Case Study—Reliability of Detonation Train with Shaped Charge Donor
Common methods for analyzing the detonation transfer probability of an explosive train by introduction of a gap penalty include Bruceton, Probit, and similar fire/no-fire methods. The introduction of a plastic gap leads to shock wave reduction, thus making it possible to test a small sample under severe conditions, rather than testing a large sample at nominal working conditions. The main assumption in most cases, is that detonation transfer is based on shock wave propagation. However, when the donor explosive resembles a shaped charge, this assumption may be reconsidered since more than one initiation process takes place. The penalty imposed by a plastic gap on shock wave propagation may differ from its influence on the initiation process by a shaped charge. In the presented work, a case-study has been examined both theoretically and empirically. Theoretical and numerical models were considered, followed by a Bruceton-analysis field test. The explosive train examined consisted of a standard detonator with a shaped charge at its base and a CH6 booster. A test was performed based on the Bruceton method. The distribution of the initiation probability predicted by numerical models is compared to Bruceton test results. The model's prediction and the test results are in good correlation. The experimental results suggest that Bruceton analysis may be applicable when a donor explosive with shaped charge output is used. Further work should be performed to verify applicability of the Bruceton method for a wider range of similar engineering configurations.
Study of Detonation Wave Contours in EFP Warhead
An analytical model for calculating the time of shock wave propagating in the wave shaper is presented in this study. The calculation results show that three typical detonation wave contours can be formed in the main charge by changing the thickness of the wave shaper, such as the conical detonation wave, the spherical detonation wave, and the plane detonation wave. The conical detonation wave can greatly increase the explosively formed projectiles (EFP) length–diameter ratio, but the Mach wave may break the nose of the EFP. The spherical detonation wave prevents an increase in the EFP length–diameter ratio. The plane detonation wave can increase the EFP length–diameter ratio and keep the nose of the EFP integrated. The thickness of the wave shaper should be less than and approximately equal to the critical thickness to ensure that the detonation wave can increase the length– diameter ratio of the EFP.
ZHENGXIANG HUANGA, CHUANSHENG ZHU, QIANGQIANG XIAO
Effects of Strain Rate on Fragmentation Performance of Dynamic Fracture and Fragmentation of Notched Cylinders
Notched cylinders were explosively driven to dynamic fracture and fragmentation to determine the effects of explosive charges (loading strain rate) on fragmentation performance (fragment shape, average fragment mass, and fragment mass distribution). Fragments of the cylinders were carefully recovered and sorted according to fragment shape and fracture mechanisms. The experimental results revealed that shear fracture was more pronounced in the fragmentation of notched cylinders with higher strain rate. The average fragment mass of controlled fragmentation was discussed in connection to Mott wave theory; this value decreased with increasing loading strain rate. Additionally, the fragment mass distribution of controlled fragmentation was analyzed, which appeared more dispersed with the increasing strain rate. The normalized cumulative fragment number of controlled fragmentation approached a statistical distribution with increasing loading strain rate.
Influence of Groove Depth on the Breakup of a Controlled Fragmentation Shell
FOI is presently performing a basic study on a generic controlled fragmentation charge where the influence of groove depth on the casing breakup and acceleration of the fragments are studied by both experimental and numerical means. In this study we have used casings with internal grooves in a 60 degree diamond pattern. The groove depth was varied from 8 to 67 % of the case thickness. Charges were detonated in a sawdust pit, fragments were soft recovered and the fracture surfaces were analysed. In all cases the casings broke up in the desired shape, though the thickness of the fragments and the fracture surface showed considerable differences. Complementing experiments using flash X-ray flashes were conducted in order to determine the fragment velocity. Material test data for fracture strain as function of triaxiality and Lode parameter were used in numerical simulations using LSDYNA to analyse the breakup process. Good agreement between the numerical simulations and final shape of the fragments are obtained.
Very Long Standoff Dispersion and Penetration of Shaped-Charge Jets
Two series of experiments were conducted by RUAG, testing Swiss 50mm/50º charges at very long standoffs. The main goal of these experiments was to examine the behavior of the jet and the particles that are created during the particulation process. Examining the radial and rotational movements of the particles we found that the main cause for the decrease of the penetration and spread of the depth results with increasing standoff emanates from two mechanisms: the side radial movement of the fast and the rear parts of the jet. The longer the standoff the larger these parts are, up to the moment where all the jet is dispersed. According to this analysis, the drift model that takes into account only the radial movement of the whole jet and therefore calculates a cutoff velocity is an oversimplified engineering model that misses the real physical basis.
The Effect of Initiation and Liner Thickness on the Jet and Penetration Characteristics
Six experiments were conducted using a constant volume 90% RDX explosive in order to study effects of three liner thicknesses and initiation at point and peripheral locations. The experiments were modeled using SCAN and BRIGS analytical software as well as numerical modeling using AUTODYN. The results appear to validate previous work on effects of liner thickness on jet and penetration characteristics. One of the main findings is that the particles in the front part of the jet, created by peripherally initiated charges comprise of several small and fast particles. Predicting the exact shape and velocity of these particles is very difficult.
Y. ME-BAR, L. MISIUK, J. E. BACKOFEN, E. HIRSCH
On the Prediction of Fragment Distribution of Naturally Fragmenting Warheads: a Machine Learning Approach
The prediction of fragment data for naturally fragmenting warheads, that are representative of the actual warheads, is of vital importance to lethality and vulnerability modelling, and also to warhead design per se. Fragment speeds can be predicted by means of Gurney (or modified) equations and the fragment trajectory direction by means of an adapted Taylor approximation. Considerable research has been conducted on the prediction of the fragment mass distribution, which includes the models of Mott, Weibull and Held. Specifically non-cylindrical warheads, with varying casing thickness, require additional segmentation and the empirical parameters for the fragment mass distribution are then adjusted manually such that the overall calculated mass distribution corresponds as close as possible to test data. In this study, to acquire a more accurate estimate of the fragment mass distribution for noncylindrical warheads, a machine learning regression algorithm is proposed. As the amount of test data increases, a function model is optimized to best represent the data. The function model is then used to provide a distribution of the test data for simulating new parameters for further analyses.
Towards a Unified Dislocation-Based Model for Shaped Charge Jet Break-Up
An old model for the ductility of shaped charge jets from metallic liners based on the behaviour of moving dislocations is reviewed in the light of new knowledge of dislocation dynamics in metals when subjected to high strain rates and large strains. A phenomenological description of jet ductility is given based on postulates regarding the generation and motion of dislocations during the shaped charge jet collapse process, as well as the depletion of the mobile dislocation population during the stretching phase of the jet. The model explicitly includes the effect of grain size in the liner on the ductility of the jet. Most of the features of jet break-up can be deduced and realistic jet break-up times are predicted for homologous designs.
Characterization of Shaped Charge Jet Erosion in Drilling Mud
A test was configured to characterize the erosion of a shaped charge jet when penetrating drilling mud used in the oil and gas industry. Three Viper shaped charges were fired simultaneously to penetrate several different thicknesses of drilling mud. A stripper plate was used to reduce the velocity of the jets to approximate that of charges of interest in deep-sea drilling operations. Flash radiographs of the jets taken prior to entering the mud verified the simultaneity of the three jets, while a second radiograph taken after exiting the various thicknesses of mud clearly displayed the jet erosion as a function of thickness of mud penetrated. Observed jet erosion is compared with simulations of jet erosion to validate modeling of the phenomena. The conclusion is that jet erosion when penetrating drilling mud can be described simply based on the density of the drilling mud.
GREG SCHEBLER, DOUG DOBIE, DOUG FAUX, ROBERT KUKLO
Power Calculation of a Tank Gun at Different Altitudes
The change of altitude, that is, the change of the atmospheric parameters, directly affects the characteristics of an explosive detonation. The change of the surrounding medium and the parameters of the detonation should have an effect on the parameters of the shock wave, however, there are few Chinese or foreign reports, especially the dynamic pressure impulse change. Based on the experimental data of a tank gun, the fitting relationship obtained by numerical simulation is used to quantitatively analyze the changes of the parameters of air shock wave at different altitudes. Research results show that the elevation of altitude caused the attenuation of the peak overpressure and the positive pressure impulse; furthermore the degree of attenuation is different, but the dynamic pressure impulse and the time of the positive pressure of the shock wave increased. This shows that the change of the dynamic pressure impulse should be paid attention.
Numerical Analysis of the Effect of the Geometric Parameters of CEFP Warhead
Cluster explosively formed penetratorô€¯­ CEFPô€¯­ warhead was a new EFP warhead which assemble a plurality of liners on the outer surface of spherically shaped explosive and projected high velocity explos ively formed penetrators uniformly and radially in 3D s pace . Based on the increased specific surface area of the charge which used to assemble the liners, CEFP had significantly more lethality and higher destructive effects than conventional Warheads . In order to further investigate characteris tics , the nonlinear dynamics code was applied to explore the EFP forming of different liner shapes (basically hemispherical shape).By a series of simulation, we studied the effect of the liner’s configuration parameters, namely the thickness of the liner, diameter and the radius angle on the formation parameters, such as the velocity and length/diameter ratio of penetrators.
LI GANG, HUI WANG, FEI SHEN, XINLIAN REN
Shaped Precursor-Charge for a Multi-Effects Warhead System
A tandem Multi-Effect Warhead (MEW) was developed. The warhead comprised a Shaped Precursor-Charge (SPC) having two tasks: perforating structural wall targets for a follow through penetrator and clearing explosive reactive armor (ERA) targets. Two concepts for this SPC were pursued: a classical Cu-liner shaped charge (MILAN) and a nonconventional Al/Mg-liner shaped charge (STABO). The investigations for these two SCs covered both the initiation behavior of an ERA and its SC jet performance degradation effects. Two generic ERA targets were used in this study one with faster and one with slower flying plates. The inclination angle was varied between 0° and 70°. Also the effects of inert ERAs were considered.
OE MAHN MOON, E. ROTTENKOLBER, T. HARTMANN
A Methodology to Derive Shaped Charge Jet Characteristics Which Will Not Initiate Thin Explosive Interlayers
Perforating add-on explosive reactive armour modules without initiation thereof, has been a long standing objective of warhead designers due to the expected minimal disturbance of the follow through main charge jet. In this study ERA initiation and perforation thresholds were explored with copper liner based shaped charges. Analyses and experiments taking into account of the IT-threshold in combination with the observed interaction of shaped charge jets with ERA targets resulted in the need for a new warhead design. This concept design entails a jet with tailored kinetic energy characteristics, i.e. a jet with a v2D below the IT but with still enough energy to perforate four armoured plates, at different angles, without initiating the energetic material of a double ERA target.
On Detonation-Like Burning, or IM Test Evaluation
A test was conducted to determine the reaction of composite propellant in a rocket motor to detonation of an adjacent warhead. The reaction was much more violent than expected. The front-most portion reacted so heavily that it was detonation-like, and there was clear evidence that the neighboring portion exploded. These responses are thought to be related to jetting from the star-shaped axial void along the axis. IM (Insensitive Munition) evaluation of the event is tackled somewhat tediously, a major aim being to demonstrate our approach. It is suggested that the IM community revise some aspects of protocols.
Initiation of High Explosive Charges by Fragment Impact
This paper describes a study on the sensitivity of high explosive charges to fragment impact. Two different projectiles, an 18.6 g steel cylinder according to STANAG 4496 and a 250 g steel sphere (French Heavy Fragment), were launched against cylindrical Composition B charges with velocities up to 2500 m/s. These charges were covered with a 10 mm steel plate or uncovered. At first, the interaction of both projectiles with the steel cover plate at different impact velocities was investigated. Important measures were the projectile shape and velocity after penetration as well as the dimensions of the perforations in the cover plate. Afterwards both projectiles were launched against the high explosive targets. Strongly different values of the critical impact velocity and the width of the transition zone were observed. The experiments were analyzed following the v2d law.
Comparison between a Classic and a New Soil Model to Simulate the Effects of Buried Mines
On the battlefield, buried mine blasts are among the most violent and destructive threats military vehicles could face. The prediction of armored vehicle behavior subjected to such a blast is of the utmost importance for its dimensioning. A modular test rig has been designed and developed to measure simultaneously the deformation of a metallic plate and the impulse transmitted by the buried explosion in several configurations. These experiments have been reproduced in simulations using two soil models. The first one is a well-known soil and foam material model available in LS-Dyna [1]. This model is defined with elastic moduli, a yield surface and an equation of state as parameters. However, all these parameters are constant, so that any change in soil composition (density, humidity, etc.) needs a new set of parameters, which could be a limitation. The second one is a viscoplastic cap model written as a user routine in LSDyna, and takes into account the degree of water saturation of the soil. This new model has been developed through DGA (French MoD) study [2], and provides a better correlation with experimental results.
Study on Numerical Simulation of Initiation Effect of Kinetic Energy Block to Covered Explosive
The shock initiation of kinetic energy block with large mass to different covered explosives was described. Using Ansys AutoDyn-3D simulation software, three typical explosive (Comp.b, PBX-9404 and OCT) are chose. Through calculating the kinetic energy block impacting covered explosive with 10# steel cover plate of 10mm to 40mm at angles of 0 to 80, critical velocity for ignition which can initiation explosive has been gained, and functions of velocity-impact angle at different cover thickness are also obtained. The results show that initiation velocity increases nonlinearly with the impact angle; initiation mechanism of explosives is different because of different sizes of impact angles; PBX explosive is more liable than the other two explosives. The results provide data support to warhead design of air defense and damage assessment.
Development of a Novel Lightweight Recoilless EOD Disruptor
The development of a novel lightweight recoilless disruptor, based on the Davis gun principle, for neutralising improvised explosive devices (IED) is described. The principal design drivers were for a system which used ammunition already qualified for UK military service to reduce the acquisition risk; to deliver performance equivalent to current 40mm calibre disruptors and to be capable of integration with small remote control vehicles (RCVs) for bomb disposal. These small RCVs have a much reduced load carrying capacity and their lightweight arms are intolerant of mechanical shock. The design process and the results from the disruptor performance assessment are presented. The disruptor weighs less than 3 kg; it is completely recoilless and has been successfully integrated with a one-man portable RCV. Over 60 firings have been conducted from RCVs and their subsystems without any noticeable adverse impact on the platform.
D. NEWELL, R. POTTER, K. PHAN, M. SLATER
Study on the Natural Fragmentation Formed by Metal Cylinder Explosion
This paper presents numerical simulation and experimental results of the natural fragmentation formed by metal cylinder explosion. To simulate fragmentation behavior using the commercial code Autodyn-3D, the reliable two parameters for Mott’s stochastic failure model must be determined in advance. To determine these parameters, we designed SCM440 cylinder filled with TNT to experiment fragmentation behavior because warheads for natural fragmentation are generally designed similarly to cylindrical shape. Using the fragmentation shapes and mass distribution of experiment results, we determined the parameters for Mott’s model. We expect that these results can be used to estimate fragmentation behavior and to design fragmentation warhead.
Influence of Initiation Modes on Lethality Capability Enhancement of Asymmetric Initiation Warheads
Several Asymmetric Initiation(AI) warheads using different initiation modes are proposed to increase lethality capabilities of conventional antiaircraft missile warheads. In the aimed direction of minus 45 degrees to plus 45 degrees around warhead axis enhancements of fragment quantity and velocity are extensively studied on the basis of numerical simulations and field experiments, where warheads using four different initiation modes including central axially single-point initiation, 6-point adjacent asymmetric initiation with a spacing angle of 45 degrees, 6-point interval asymmetric initiation with a spacing angle of 90 degrees and 9-point continuous asymmetric initiation with a spacing angle of 90 degrees. The field experiments results show one AI warhead using 9-point continuous asymmetric initiation with a spacing angle of 90 degrees, having fragment quantity and velocity gains of 15.69%, 25.62% respectively, is more excellent than AI warheads using the other initiation modes, which dramatically increases letahlity effects in the aimed direction around AI warhead axis towards intended threats.
GANG DING, BAOHUI YUAN, QINGBO JING, JUN PENG, WANJUN GENG, GUANGJIA LI
Influence of Explosive and Liner Cone Angle on the Performance of Standardized Shaped Charge Jet
Standard shaped charge of 50mm diameter, widely used in evaluation of explosive/munitions vulnerability against metal jet, is extensively studied with the help of LS-DYNA software and field tests. Four different shaped liners with cone angles including 46 degrees, 48 degrees, 50 degrees, and 60 degrees respectively, configured with RDX-based and HMX-based PBXs, are simulated to find optimum jet velocity and width. Simulation results show that shaped charge jets of liner cone angles of 46 degrees and 48 degrees configured with HMX-based explosive, are more excellent than the other configuration of liner cone angles and RDX-based explosive. In field tests velocity and width of metal jet tip are elaborately measured by the help of X-ray radiograph, whose Vj2d value is a very important parameter detemining penetration capability of metal jet. Field test results show that shaped charge jet of liner cone angles of 46 degrees configured with HMX-based explosive, having a desirable Vj2d value no less than 360mm3/μs2 and penetraion against larger than 127mm thick steel plate.
Innovative Lagrangian Numerical Approach for Natural Fragmentation Modeling
Numerical modeling of fragmentation from dynamic loading has traditionally been modeled by legacy finite element solvers that rely on element erosion to model material failure. However it results in too much material removal which is not realistic as retaining the structure mass is critical to modeling the event correctly. We propose a new approach implemented in the IMPETUS AFEA SOLVER® based on: New High Order Finite Elements (very well suited for large deformations); stochastic distribution of initial damage (non-homogeneous distribution of fragments); a Node Splitting Algorithm (material fracture without element erosion) and a new particle method for High Explosive modeling. The approach is evaluated for various scenarios: beam and thin cylinder bending, ring compression and warhead natural fragmentation. The results obtained from the simulations are representative of the failure mechanisms experimentally observed. The main benefits of this approach are good energy conservation and numerical robustness even in complex situations.
JÉRÔME LIMIDO, JEAN-LUC LACOME, FRÉDÉRIC PAINTENDRE
Magneto-Hydrodynamic Calculation of Magnetic Flux Compression Using Imploding Cylindrical Liners
Based on the one-dimensional elastic-plastic reactive hydrodynamic code SSS, the onedimensional magneto-hydrodynamics code SSS/MHD is developed successfully, and calculation is carried for cylindrical magneto cumulative generators (MC-1 device). The magnetic field diffusion into liner and sample tuber is analyzed, and the result shows that the maximum value of magnetic induction to cavity 0.2 mm in liner is only sixteen Tesla, while the one in sample tuber is several hundred Tesla, which is caused by balancing of electromagnetism force and imploding one for the different velocity of liner and sample tuber. The curves of magnetic induction on axes of cavity and the velocity history on the wall of sample tuber are calculated, which accord with the experiment results. The works in this paper account for that code SSS/MHD can be applied in experiment configures of detonation, shock and electromagnetism load and improve of parameters successfully. The experiment data can be estimated, analyzed and checked validly, and the physics course of correlative device can be understood deeply, according to SSS/MHD.
Simulating Geometrically Complex Blast Scenarios1
This extended abstract describes the development of an adaptive mesh refinement Eulerian hydrocode called EAGLE built around finite-volume solvers to ensure conservation of the evolved quantities and ability to handle discontinuous solutions. The application of a derivative of EAGLE, called EAGLE-Blast, to the solution of a number of simple and complex blast problems is described. This includes work to validate and verify EAGLEBlast against a range of problems of increasing complexity. These include analytically tractable 1D problems, 2D free field blast problems and more complex 3D problems. In the latter class of problems the paper describes the ability of EAGLE-Blast to reproduce two experimental studies. The paper concludes with a discussion of the use of EAGLE-Blast as the lower tier of a hierarchical modelling capability with Fast Running Engineering Models sitting in the top of the hierarchy. The full paper will be published in Defence Technology Volume 12 Issue 2.
PETER FRANKL, PAUL BENNETT, NIKOS NIKIFORAKIS, PHILIP BLAKELY, PAUL GREENWOOD
Expansion and Fracture of Fragmenting Warhead Shells of Various Materials under a Cl-20 Explosive Charge
To study the effect of the warhead material characteristics upon warhead expansion and fracture and upon the formation of fragments under a high-power explosive charge, four different warhead materials; 30CrMnSiNi2A steel, 40CrMnSiB steel, 50SiMnVB steel and 82 steel; are examined. This paper builds a analytical modeling to theoretically analyze the expansion and fracture processes for the different material warheads. In addition, the AUTODYN-3D finite element software is used to numerically simulate the expansion and fracture processes of the four materials, and high-speed photography technology and a tinfoil target velocity test system are used to verify the simulation results. It is found that, for the “ φ 62mmâ€ aperture warhead under the explosive CL-20 charge, the expansion and fracture processes of the four materials all require ~60 μs, and the shell expansion velocity in the whole process can be divided into three stages called libration, acceleration and stabilized. The initial velocities of the fragments along the warhead axis for the different warhead materials are consistent with each other, though the expansion velocity and the maximum initial velocity of the fragments are largest for the 30CrMnSiNi2A steel warhead. It is found that the warhead expansion velocity and the initial velocity of the fragments decrease gradually as the ultimate tensile strength of the warhead material decreases and as its dynamic fracture toughness increases. This study introduces the coefficient of radial warhead expansion and acquires the function for the distance of the radial warhead expansion over time, which is influenced by the warhead material characteristics. The results of this study will provide a reference for fragmenting warhead shell material selection and design.
WEN-BIN LI, XIAO-MING WANG, CHUN CHEN, JIAN-JUN ZHU
Study on the Expansion and Fracture of a Cylindrical 50SIMNVB Steel Shell under Different Tempering Temperatures
To study the effects of different tempering temperatures on the expansion and fracturing of a warhead and the subsequent formation of fragments, this paper has selected 50SiMnVB steel which was tempered separately at 450 ℃ and 650 ℃ as the objects for study. Images of the expansion and fracture processes of the cylindrical shell were captured by using high speed photographic technology. In addition, this paper used the AUTODYN-3D finite element software to numerically simulate the expansion and fracture processes of 50SiMnVB steel. The formation of fragments was studied through the use of Scanning Electronic Microscopy and Metallographic Analysis. It was found that, with the increasing of the tempering temperature, the structure, composition and shape of 50SiMnVB steel’s microstructure changed constantly. Observations made include; an increase in strength and toughness together with an increase in plastic deformation and a further change in fracture mode from tensile-shear factor to that of shear factor. With the increasing of the tempering temperature, the time needed for fracture generation and detonation product leakage on the outer surface of the 50SiMnVB shell was delayed under detonation loading. The expansion distance of the 50SiMnVB shell under the tempering temperature, 650 ℃ is increased by 23.95% when compared with the other test cylinder under the tempering temperature of 450 ℃ , and the expansion velocity is increased by 11.0%.
Small Scale Structure for a Simulated Blast Event Below Add On Armor
Full scale explosion tests are very expensive and involve the use of special measurement devices. In order to overcome these difficulties and reduce the overall expense, a unique small scale jig was developed and manufactured. The uniqueness of this reduced scale jig lies in the fact that we are able to emulate the exact acceleration levels on the crew chair wall supports which occur during explosion events beneath the underbelly of a full scale heavy vehicle platform. The complete research and development program was accompanied by an advanced full system FEM simulation performed via LS-DYNA 3D software. The study presents a comparison between the numerical and experimental results for the specific experimental explosion event. The simulation results showed that the acceleration level magnitudes measured at different points on the experimental jig structure as well as on the Hybrid dummy III parts resemble the experimentally measured values
DAVID TOUATI, ILAN AZULAY, SHIMON HAYOUN
Numerical Simulation of Spherical Charge Dynamic Blasting and Overpressure Field Calculation Model
To investigate the dynamic blast overpressure field, the dynamic blast process of spherical charge was simulated in SPEED software. The contours of overpressure and peak pressure (P) at typical azimuth () and scaled distance (Z) were obtained. The results show that the overpressure field of dynamic blast presents entirely different characteristics in comparison to the static one. Based on numerical results and the classical overpressure theory, a new calculation model is established by introducing a correction factor containing charge moving velocity (V), and Z to Baker formula. The corrected formula is proven to be accurate and universal in predicting dynamic blast overpressure for different charge mass .
Fragment Spatial Distribution of Continuous and Discontinuous Multi-Contoured Warheads
Pre-formed fragmentation warheads with narrow fragment beam are deployed in guided missiles to neutralize a variety of aerial targets. However, when these missiles are used against ground targets like radar installations, a wide forward beam may be demanded. By shaping fragmenting surface, wide forward fragment beam can be achieved. In single continuous contour design, the fragmenting surface length works out to be small, which results in low warhead mass and fragment hit density. To achieve high mass and hit density, the authors proposed multiple discontinuous contoured fragmenting surfaces. A case study is carried out to generate wide forward fragment beam of 80° using single continuous and double discontinuous contours. The discontinuous contour warhead has improvement in mass by 37% and the observed hit density is 18% higher than continuous contour warhead.
Understanding Experimental and Computational Gurney Energies
It is now common to experimentally reduce Gurney energies associated with detonation products expansions using experimental cylinder expansion tests and the traditional Gurney formula for cylinders. However, this methodology results in Gurney energy values that are inherently geometrically dependent and do not provide quantitative measurements of explosive work output per mass. It is well known that the outside surface of an explosively expanding metal cylinder has a somewhat lower radial velocity than the cylinder inside due to wall thinning. It is also well known that the cylinder wall bends during acceleration resulting in a material motion Lagrangian velocity that is neither perpendicular to the original wall surface nor to the instantaneous wall surface. In addition, the high explosive detonation products have axial flow that is not accounted for using the cylinder Gurney formula. A number of researchers have identified these issues and have used various different methods to address them. One increasingly common methodology is to calculate Gurney energies using an analytic cylinder model along with thermochemical equation of state calculations. This methodology has proven to provide excellent agreement with experimental Gurney energies for a wide variety of high explosives.
Modifying Preformed Fragment Dispersion by Form Factor
Preformed fragment warheads have been utilized in many instances as it allows the warhead designer to optimize the fragment size for the specific targets it will be used against. These preformed fragment warheads also have some negative aspects associated with them, including reduced fragment velocity due to less gas checking, as well as potential fragment mass loss due to the thin warhead cases the fragments are typically wrapped around. You can overcome some of the reduced fragment velocity by increasing the diameter of the explosive column (when comparing warheads with a fixed upper mass limit), but bringing the length to diameter ratio closer to one reduces the dispersion of these fragments into the spatial area around the warhead at detonation. This can reduce the probability of hitting your intended target. This effort was undertaken to determine if it was possible to increase the ejection angle of these preformed fragment warheads by modifying the shape of the fragments placed around the warhead case.
The novel concept of the RADIUS technology, an acronym for Range Adaptable Device Incorporating Unique Scaling, is unique in the way performed by TDW. The control of warhead output can be achieved within a compact fuzing system incorporating two pyrotechnical outputs: one output is used for initiating a classical detonation and the other one for initiating a distinctive subdetonative mechanism. Such an enhanced weapon with a discrete number of output modes allows scaling of blast / fragmentation effects and respective lethal and collateral damages footprints against surface targets. RADIUS technology prototypes based on a 500 lb (MK-82 / BLU-111) precisionguided bomb recently demonstrated their minimum and maximum output modes against a comprehensive target set consisting of various witness panels and SUV cars. These tests were conducted jointly with BAE Systems, Munitions. The different outputs and their resulting level of damages can be clearly observed. High-speed video sequences of the subdetonative reactions leading to regular fractures of the bomb casing suggest a highly controlled and repeatable underlying process. This was also modeled utilizing Lee-Tarver’s extended Ignition and Growth model with a single robust parameter set reproducing well different charge dimensions. Vulnerability / lethality assessments for various output modes of a 500 lb precisionguided bomb were conducted to demonstrate these new operational capabilities in joint fire support simulations and in a realistic urban environment. Implementing this technology into a variety of bombs or missile warheads for surface attacks will allow cost-effective solutions through the life cycle, since the mix of weapon types can be reduced and so does the integration effort into weapon systems / platforms as well as logistical constraints.
Armor Panel Deformation Due to Simulated Land Mine Blast Testing and Simulation
There are two important steps in modeling vehicle and occupant survivability due to blasts: the blast loading on the vehicle and the subsequent motion and deformation of the vehicle and occupants due to the load. At the last symposium, we presented our blast loading approach that was refined and extended during the Defense Advanced Research Projects Agency (DARPA)’s Adaptive Vehicle Make (AVM) portfolio of programs. In this paper, we discuss the subsequent deformation of panels with and without stiffeners. To better understand blast and to validate the computational pipelines, SwRI performed blast tests on various panels made of rolled homogenous armor (RHA), aluminum, and magnesium. Quantities measured included imparted impulse to the fixture, maximum dynamic deformation, and maximum static deformation of the panels. The deformation data is presented here and includes comparisons to computations performed within the AVM computational framework.
DONALD J. GROSCH, SIDNEY CHOCRON, CARL WEISS, REW BARNES, ALEXANDER J. CARPENTER, JAMES T.
Linear Exponential Fragmentation Statistics and Scaling for Cylinders with Thermobaric Explosives
Although historically the Mott equation has been used for describing the fragmentation statistics of naturally fragmenting warheads, there are arguments for using different statistical distributions. This work compares two and three term linear combinations of exponential distributions to describe the experimental fragment distributions from mild steel cylinders exploded with C4 or two thermobaric explosives. While scaling relations for the Mott distribution have been developed, none could be found for multi-term exponential distributions. Relationships are proposed, tested, and findings presented for scaling experimental fragmentation distributions. The initial analysis suggests that there is a characteristic limiting fragment size common across all distributions and that the Chapman Jouget pressure influences the dependence of fragment mass on strain rate and influences the proportion of fine fragments. The question still remains if this approach yields significantly better results over the Mott distribution.
Development of Tuneable Effects Warheads
The tuneable effects warhead concept is based on QinetiQ patented [1] technology, previously explored using bare explosive charges [2]. This work showed significant differences in peak blast pressures between two detonation modes (35%), while maintaining quasi-static pressure. The study reported here looked at developing a metal cased variant with the aim to demonstrate a tuneable fragmentation output, whilst maintaining the demonstrated blast performance.
Investigation on the Use of PETN Based Sheet Explosive in Hardening and Welding
In explosive hardening and welding processes, one of the essential requirements is the preservation of the surface integrity of participant materials, for this the velocity of detonation (VoD) is kept low. For explosive hardening process, standard sheet explosives are used and for explosive welding process various types of powder explosives are widely used. Nevertheless, these types of powder explosives have limitations viz., difficulties in mixing and handling; cannot maintain uniform thickness along the large surface, large critical thickness, variation in VoD with thickness of explosives. To overcome the problems of conventional sheet explosive and powder explosives, a novel PETN based slurry casted explosives is developed which consists of PETN explosive mixed with inert additives, plastic binder and plasticizer. This slurry casted explosive has uniform density and thickness and easy to prepare and handle. The VoD can be maintained as desired in the range of 2000 m/s to 6000 m/s by varying the ratio. This chemical mixture was used for surface hardening of mild steel, and high manganese steel plates. Post hardening, it is observed that the plates were not damaged and their dimensional and material integrity remained unchanged. In explosive welding process slurry casted PETN based sheet explosive with low VoD was developed by mixing it with inert additives and used for explosive bonding of Aluminum to Stainless Steel, Copper to Stainless Steel. The VoD of the explosive was measured, and it detonated successfully during the trials. Since PETN has very small critical diameter, sheets can be made as small as 2 mm thickness with reliable and stable detonation. It is concluded that most of the problems of powder explosives can be surmounted by using high explosive based slurry casted sheet explosive. With these preliminary investigations, future work will be carried out to fully optimize and establish this new process for explosive hardening and welding.
SHALLU GUPTA, BIR BAHADUR, SANDEEP KUMAR, ARUN AGARWAL
Experimental and Numerical Investigations of New Prototypes for Low Collateral Damages Ammunitions
In collaboration with MBDA France and EURENCO, Le Bouchet Research Centre of Herakles has characterized three different designs of low collateral damages prototypes containing a radially or an axially arrangement of explosive and inert charges, in comparison with a reference charge. A preliminary analysis with AUTODYN® has been conducted to predict the velocity and the fragments size. Prototypes were manufactured and experimentally characterized (fragments recovery systems, witness plates, X-Rays, high speed and ultra-high speed visualizations). Finally, numerical simulations have been conducted with OURANOS® code taking into account high explosives reaction kinetics.
FRANCOIS VERMEERSCH, LUC CHAFFOIS, CHRISTELLE COLLET, JULIEN MORICEAU
Muzzle-Center based Scaling Law for the Peak Overpressure of a Cannon Blast
For large caliber cannons, blast overpressure can have a detrimental effect on the crew in the near field (i.e., within a distance of 50 tube diameters or calibers from the muzzle center) as well as on the support personnel and equipment in the far field (i.e., at a distance greater than 50 calibers). Therefore, an efficient method to determine the peak overpressure due to a cannon blast is highly desired. In this study, we investigate a muzzle-center based scaling law for the peak overpressure due to the primary blast of a large caliber cannon.
Using ALE to Model Fluid Solid Interactions (FSI): High Velocity Penetration of a Projectile into Water
In order to solve the problems in numerical calculation of fluid-solid interaction (FSI) caused by fluid deformation when projectile penetrates into water, a finite element model was developed through experimentation by using ANSYS/ LS-DYNA software. The process in which a rod projectile penetrates water was simulated at a high velocity by applying an Arbitrary Lagrange-Euler (ALE) algorithm. The results show that the model is effectively solved several numerical problems. A higher penetration velocity leads to greater deformation and wear of projectile head and subsequently an increased rate of deceleration, due to hydrodynamic drag.
Ballistic Evaluation of an Australian Ultra-High Hardness Steel
The ballistic performance of an ultra-high hardness armour steel manufactured by Bisalloy Steels Pty Ltd, BIS UHH, has been evaluated for a range of thicknesses and obliquities against armour piercing (AP) and fragment simulating projectiles (FSPs). The performance of the material against AP projectiles was assessed against MIL-DTL-32332 and found to meet the Class 2 requirement for 7.62 mm APM2 projectiles and the Class 1 requirement for 12.7 mm APM2 projectiles. MIL-DTL-32332 specifies no performance requirement for FSPs.
HUIJUN LI, MARK EDGERTON, DENVER GALLARDY, STEPHEN CIMPOERU
The Influence of Adjacent Impact on the Perforation of Fragments
Experiments have been conducted to examine the influence of an adjacent crater or craters on the perforation performance of a diameter D=20mm fragment simulating projectile (FSP). Five FSPs were fired sequentially at impact velocities of approximately 1000m/s into a 15mm thick mild steel plate. An increase in residual velocity of 13% compared to a single impact was observed when two sequential impacts were 29mm (1.4D) apart. An impact next to two craters with the same 1.4D spacing increased the residual velocity (compared to a single impact) by 57%. An energy balance equation was used as the basis for a generalised model. It was found that the influence of the adjacent crater could be predicted from a calculation of the reduction in sheared circumference and the reduction in target plug mass. From the model it was found that the minimum spacing to avoid the influence of an adjacent crater was 1.55D at 1300m/s. The model was extended to include the effect of more than one adjacent crater, and gave reasonably good agreement with the experimental results.
The Influence of Yaw on the Perforation of Fragments
It is generally assumed that the penetration capability of fragments such as fragment simulating projectiles (FSPs) and cubes is greatest when the impact attitude is un-yawed, i.e. face-on. On this basis it is the usual aim in experiments to reduce impact yaw to a minimum. There is therefore very little published data available to confirm the assumption. This paper reports perforation experiments (V50) of two fragments impacting steel plates with orientations other than face-on. The fragments were a 20mm diameter steel FSP and a 6mm tungsten alloy cube. The FSP was found to give reduced perforation at 45° and 90° orientations compared to face-on (0°). The cube results indicate that corner-on impacts could be more penetrative than face-on orientation.
Numerical Simulations on Spherical Fragments Penetrating LY12 Aluminum Alloy Target
To investigate the characteristics of spherical fragments penetrating LY12 aluminum alloy target, the penetration process of the spherical fragments with different diameters into LY12 aluminum alloy target was simulated by LS-DYNA software. Through numerical simulation, the failure modes of the target and the penetration ability of fragments were analyzed, and also the ballistic limiting velocities were obtained. The results show that the chief failure modes of the target impacted by spherical fragments are petal type failure and plugged failure. The penetration capacity of fragments increase when one has a bigger diameter, and the ballistic limiting velocities are in good agreement with test results.
Study on the Penetration of Semi-Infinite Thickness Metal Target by Heterogeneous Long Rods with Incident Velocity 1800-3000 M/S
A kind of heterogeneous long rod with gradient change material strength and density along the axis of the projectile was proposed. The penetration performance of the heterogeneous long rod on the semi-infinite thickness 6061-T651 aluminum target with incident velocity at 1800-3000 m/s was studied theoretically and numerically. A constitutive relation includes the effect of strain hardening and strain-rate sensitivity was used to describe the character of the target and the penetration process was numerically simulated by LS-DYNA finite element code. The penetration performance of the heterogeneous long rod with incident velocity 1800-3000 m/s was analyzed. The results show that: the theoretical predications are well accord with the numerical simulation results; the heterogeneous rod shows a better penetration performance than the homogenous rod with small strength in incident velocity field 1800-3000 m/s, but just in incident velocity field above 2850 m/s for homogenous rod with high strength.
Protection Capacity of a Marine Steel against Fragments
In the field to evaluate the efficiency of the threat, we establish the protection capacity of a structure steel. For this, we realized any ballistic tests on structural metallic plate against normalized cylindrical fragments. In the goal to evaluate the deformation level induced in the target and in the projectile at the impact and during the penetration, we measured the hardness curve profile closed to the crater boundary and along the projectile axis. Thereafter, we tried to determinate different energy levels induced in the projectile and in the target (projectile impact deformation, projectile shear and target craterisation) and we compared them with the initial kinetic energy. We made also any numerical simulation works and the calculation results are in agreement with the experimental results.
Ballistic Resistance of Semi-Infinite and Finite-Thickness Adobe Targets
The authors of the present paper have published results for the semi-infinite penetration of metallic spheres of different diameters into adobe over a range of impact velocities that also show the scalability of such experiments [Int. J. Impact Engineering 75 (2015) 27-29]. In the present contribution, we review our earlier results for semi-infinite targets and complement them with so far unpublished data concerning the perforation of finitethickness adobe targets by spherical projectiles of the same type. Different theoretical approaches to the obtained penetration data are possible. As will be discussed in some detail, the penetration results in the rigid-body regime could be interpreted with the help of force-law approaches as well as by shock wave theory.
Penetration and Ignition Performance of Reactive Fragments
There is an international interest in the use of reactive components to enhance or supplement the performance and reduce the collateral damage of warhead systems. This paper describes a programme of work investigating the use of reactive fragments. Considerable work has been conducted on the use of aluminium and titanium based materials as reactive fragments or constituents of reactive cases. The objectives were the further development of reactive fragments, based on either conventional pyrotechnic materials or hafnium, and their processing techniques to enhance their launch survivability, penetration capability and thermal output. During the task the penetration performance of a series of fragments was assessed experimentally to identify the ballistic limits for these fragments to achieve penetration and initiate a reaction of the material on impact with a target material.
JOHN STUBBERFIELD, DAVE JOBSON, DOUG KIRKPATRICK, STEVE MCLEAN
Impact in Sand, Simulations and Experiments
Medium caliber ammunition impacting sand has through the last years come up as an important task to study. We have studied the phenomenon by firing experiments and by numerical modelling. In this study we have evaluated the numerical modelling technique using the explicit code IMPETUS Afea. The starting point has been high speed cameras of medium caliber inert projectiles impacting sand in various oblique angles. The IMPETUS Afea code is relatively new Swedish/Norwegian code. It uses some quite new techniques as discrete particle method for modelling of sand, soil and detonating high explosives. It also uses a lagrangian node splitting technique to better handle brake-up and failure of structures. Particularly in this study, sand as discrete particles has been the focus. The discrete particle technique was initially developed for mine blast simulations, but was further developed to model sand/soil. Detonation products are modelled with a technique based on the kinetic molecular theory. Sand/soil is modelled as discrete particles that interact through penalty-based contact with damping and friction. In the firing test the projectiles were fired against a sand pool placed in a defined angle relative to the projectile line of fire direction. The sand was defined in respect of humidity and grain size distribution. To capture the impact and rebound occurrence of the projectile, high speed cameras were used. By using the IMPETUS Afea explicit numerical code, with the discrete particle method we were successfully able model the sand impact experiments with a high degree of conformity.
An Experimental Evaluation of Composite Enclosures for Explosive Reactive Armor
Explosive reactive armor requires a rugged, energy absorbing enclosure for effective integration onto a vehicle. The enclosure both protects the armor materials from environmental exposure and reduces the collateral damage during a ballistic event by controlling the effects of the ensuing blast. The current baseline design of a reactive armor enclosure on a combat vehicle is constructed from stainless steel and is excessively heavy, adding significant integration weight to a combat class vehicle. U.S. Army Tank- Automotive Research, Development, and Engineering Center (TARDEC) performed extensive testing on fiber composite enclosures in an effort to reduce weight. The method used for evaluating the enclosures required statically detonating a representative blast load in an enclosure and evaluating the structural integrity of the neighboring enclosures. Enclosures constructed of two-dimensional fiber laminates and three-dimensional woven preforms were tested. The results have shown that very significant weight reduction is attainable using composites.
Effective Depth-of-Penetration Range Due to Hardness Variation for Different Lots of Nominally Identical Target Material
The effect of small variations of target hardness on the depth of penetration for long rod projectiles (L/D = 15) penetrating into semi-infinite armor steel targets (nominally 280 BHN–330 BHN) was investigated. The work consisted of hardness testing, 17 ballistic experiments (1250 m/s–1780 m/s) and data analysis. A linear regression analysis shows that a target hardness increase within the given range may result in a reduction of penetration depth of about 5.8 mm at constant velocity (-12 % at an impact velocity of 1250 m/s). A multiple linear regression analysis including yaw angle and impact velocity shows that small variations of those provide a smaller variation of the penetration depths than a typical variation of target hardness. The overwhelming part of the variation is to be attributed to hardness effects. For nominally identical target material, the target hardness influences the ballistic results more severely than the typical scatter in impact conditions.
, REAS HEINE, KARL ERNST WEBER, MATTHIAS WICKERT
Trajectory Prediction of Pre-Damaged Targets Impact by Rigid Projectiles with Stress Equivalent FEM Subroutine
The terminal lethality of a tandem warhead is determined by the subsequent projectile. Curved trajectories are most likely occurring in the penetration process of the subsequent projectile into a pre-damaged target due to the detonation field of the precursory HE charge on attitude of projectile. FEM simulation using the ABAQUS/Explicit code with a target response equivalent subroutine was performed to investigate the trajectories. Utilizing combined analysis, the results acquired from FEM simulation agree well with experimental data. The effects of initial impact conditions as well as corresponding trajectories have been obtained from numerical results. The results identified that obliquity and yaw angle or non-axis aligned impact offsets would change considerably the trajectory and penetration depth. The approximate pre-damaged hole in the target has a significant oriented effect for penetration of subsequent projectile, and the ricochet has occurred only in extreme conditions of high oblique or yawed angles and large offsets.
The Effect of Inter-Tile Gap on Alumina-Aluminum Plates Impacted by a Steel Projectile
The ballistic performance of the joint between two adjacent ceramic tiles is investigated. It is well known that the performance as such locations is worse due to lack of confinement. However, it is desirable to know the drop in performance as a function of the joint width. Experiments are presented in which aluminum oxide tiles backed by aluminum are impacted with hardened steel cylinders. Residual velocities and the state of perforating projectile were monitored with high speed camera. It was concluded that the performance drop was proportional to the increase in width of the seam. As the seam width increased the armor was less likely to fracture the projectile and the area of aluminum backing that is loaded by fractured ceramic was reduced.
The Interaction of High-Velocity Projectiles with Groups of Rods and Plates
The study of the problem of protecting the elements of constructions from impact loadings is very important due to the need of constant perfection of the means of shock-wave impact on the objects of modern technology. The problem of creating reliable protective systems dictates necessity of studying different ways to counteract to high-velocity elongated projectiles. The interaction of projectiles with plates and rods which are thrown towards projectile by HE is investigated. The problem is solved in 3-D statement in view of natural heterogeneity of real materials structure affecting distribution of physical-mechanical characteristics along the volume of construction elements and being one of the factors, defining destruction character of the latter. The necessity to account the given factor for equations of deformable solid mechanics dictates the application of probabilistic laws of physical-mechanical characteristics distribution along the volume of the construction under consideration. To calculate elastoplastic flows used technique implemented on tetrahedral cells and based on the combined use of the Wilkins method for calculation of internal body points and Johnson method for calculating contact interactions.
Numerical Modeling of High-Speed Interaction Processes between Fluoropolymer Projectiles and Light Alloy-Based Targets
The paper presents a method for calculating the kinematic characteristics penetration of PTFE projectile into the aluminum target considering the chemical reaction between PTFE and aluminum. Accounting of kinematic characteristics was conducted by the method of large particles. Accounting of the chemical reaction was carried out by the method of Counterflow Diffusion Flame. The results of the calculations are given. Qualitative and quantitative agreement results of the calculation fit with the experimental data.
E.A. KHMELNIKOV, A.V. STYROV, K.V. SMAGIN, S.O. BOCHKAREV
The Failure Mechanism of Frangible Nose Cap upon Water Impact
The damage process and dominant factors influencing the damage pattern of the nose cap during water impact are analyzed in order to study the fracture mechanism and theoretical design method of the nose cap. The numerical simulation and water entry experiment are carried out for the nose cap with given boundary conditions. The research shows that the mode of “wedging-in damageâ€ is the effective damage pattern of nose cap during water entry. The strength matching design between the top portion and the weak-links is a necessary condition for the nose cap to implement this damage mode. The concept of feasible region of nose cap is advanced as the theoretical boundary of structural design of the nose cap.
LIU FEI, QU MING, HU YANHUI, ZHAO JIANBO
Behavior of Multi-Layered Metal Plates under Ballistic Impact
In the effort invested in finding an optimization design for metal structures, the protection performance of double and multi-layered metal shields against projectile impacts was studied experimentally and numerically. Although the idea of using layered plates instead of monolithic ones in order to increase the ballistic perforation resistance is not new [1]-[2]. Results obtained by various authors are contradictory and thus detailed experimental and numerical work is still required [3]-[4]. In the present study, we examined the ballistic performance of different target combinations impacted by a 7.62 mm ogival head armor piercing projectile in the velocity range of 920-950 m/s. The residual velocity was measured through the use of high-speed camera for tracking the projectile before and after perforation. Numerical models were developed using the explicit finite element code LS-DYNA. Good agreement was obtained between the numerical simulation and the experimental results. It was found that the overall protection level may be significantly decreased by layering the target. However, when spacing the layered target, the projectile was severely damaged. This effect decreases the penetration capability of the projectile.
Penetration Performance of a Calibre 5.56 mm Tungsten-Rhenium AP-Projectile into Steel and Ceramic Targets
The AP3 (US M995) calibre 5.56 mm projectile contains a core made of cemented carbide. The high hardness of this material facilitates rigid body penetration in most types of metal targets. On the other hand, in a ceramic target, the ceramic has a hardness equalling or exceeding that of the cemented carbide and the core will deform and shatter instead of stay rigid. Since the performance of a deforming projectile core depends on both inertia and the strength, a hypothesis is that a higher density may be able to compensate for lower strength or even be more favourable when defeating this type of targets. In order to study this, projectiles with cores made of tungsten-26% rhenium with a density of 19.7 g/cm3 have been tested. The geometry of the W26Re was made identical to the cemented carbide core in the Nammo AP3 projectile. The penetration performance of the W26Re projectile and the original projectile was tested against two different target types: a simplified ceramic armour structure and a single steel armour plate. The performance was evaluated by establishing the ballistic limit velocity for each target and projectile combination.
Soil Penetration with Gas-Gun Experiment
In this paper, we have obtained S-number, which proposed by C. W. Young, of soil target using the high velocity impact test. S-number is commonly used throughout the weapons community as a descriptive term for resistance to penetration. We used wrap-around type gas-gun equipment to perform the penetration test of soil target. The impact and residual velocity of projectile was measured with the high-speed camera. The experimental result shows that the S-number decreases with the increase of soil density. The accuracy of Young's equation for the penetrability (S-number) of soil was verified with the in-house gasgun test.
Modelling Bullet Richochet from Wooden Targets
Recently, in the Netherlands impact experiments were performed using flat wooden targets with different physical properties. Materials studied include Obeche, Meranti, Beech, Spruce, Pine, and Ipé. In these ricochet experiments 7.65 mm Browning (.32 Auto) and 9 mm Luger projectiles were used. In this paper the critical impact angle ac for bullet ricochet is studied using analytical models. For the modelling work physical properties of wood and the projectile relevant to ricochet will be discussed. In a first approximation, deformations and grain structure of the wood will be neglected. The bullet ricochets will be evaluated using the analytical ricochet models of Tate and Rosenberg et al. developed for impacting rods. However, the ricochet model of Wijk predicts the critical impact angle ac best. Possible reasons for differences between the model and experimental results are given.
Analytical Model of Spherical Projectile Penetration into Ballistic Gels
Biolistic drug delivery is a novel method for the intradermal needle-free injection of a wide array of drugs and vaccines. These devices project microparticles, containing a drug or vaccine, onto the skin at speed up to 500 m/s. To achieve the optimal therapeutic or prophylactic effect, the particles need to be delivered to specific skin layers. In order to evaluate the critical parameters and understand their influence on the penetration depth, an analytical model has been developed. The model is based on the real time tracking of the position of a ball shot into ballistic gelatin and Perma-Gel using a high-speed camera. This macro-scale model is then analyzed in a micro-scale perspective and compared to the results observed with the biolistic needle-free injector. Finally, based on the model, a method to characterize the viscosity and the ultimate strength of gels at intermediate strain rate impact is proposed.
Influence of Confining Prestress on the Transition from Interface Defeat to Penetration in Ceramic Targets
A set of impact experiments has been performed in which the transition velocity for four different levels of prestress has been determined. The velocities are compared to an analytical model for the influence of prestress on the formation and extension of a cone crack close to the impact zone (the crack is assumed to control the transition). The main conclusions can be summarized as follows: (i) the model shows a strong influence of prestress on the transition velocity; the projectile pressure at transition increases linearly with the level of prestress. (ii) The impact experiments show that prestress has an even stronger influence than predicted; the maximum contact pressure at transition is more than doubled if prestress is increased from zero to around 100 MPa. (iii) Further increase of prestress did not show the same strong influence and a transition velocity of 1500 m/s was found unaffected in spite of increased prestress.
Development and Validation of High Strain Rate Model for Water Ice
There is significant interest within the European Space Agency (ESA) in Space Penetrator technology as an additional option for inter-planetary exploration. The concept seeks to embed a penetrator into the planetary surface and then to perform in situ scientific measurements, such as mass spectrometry and physical properties characterisation, which are communicated back to an orbiting spacecraft. The main ballistic challenge is to design the penetrator system so that the penetrator and payload survive the high deceleration gee loading. A key challenge is to understand the high strain rate response of the planetary surface water ice. This paper describes efforts to conduct Split Hopkinson Pressure Bar (SHPB) Tests on ice samples without cracks or bubbles at -10â°C and -80â°C and small scale ballistic tests. Simulations are used to predict the results to provide a better understanding of the penetration process in ice.
IAN LEWTAS, PETER GOULD, CHRIS BRAITHWAITE, Y JARDINE
The Break-Up Tendency of Long Rod Projectiles
A model for the tendency of fragmentation of a long rod projectile subjected to flyer plates in add-on armours such as reactive armour and active protection systems is presented. The assumption behind the model is that the sliding force, with velocity νslide between the projectile and a moving plate, give rise to a transverse velocity νtrans of the projectile segment it passes, which will deflect the projectile segment. This deflection is assumed to be a major reason for the fractures that can emerge along the projectile and can be described by the dimensionless parameter δ = νtrans/νslide. The paper describes how this parameter can be expressed in terms of velocity, geometry and material of the projectile and the plate. Experiments and simulations has verified that the identified δ- parameter predicts an increased amount of fragmentation of the projectile with increasing value of this parameter.
Research on the Attitude Change of Projectile with Nose-Cone When Penetrating Multi-Layer-Interval Steel Targets at Big Impact Angles
In order to analyze the attitude change process of projectile with nose-cone while penetrating the multi-layer-interval steel targets at big impact angles, the attitude change process of projectiles was analyzed when the projectile with nose-cone penetrated the double-layer-interval steel targets(DLIST) at 60° impact angle and four-layer-interval steel targets(FLIST) at 30° impact angle by using LS-Dyna, and verification test was also done by using 156mm gun. The simulation results show that the axis of projectiles and ballistic lines both deflect to normal direction of targets in the process of penetrating the DLIST and FLIST, but the deflection angles are not very big. The deflection angle of projectile axis reached up to 11.5° approximately after penetrating the second-layer steel target in the test of penetrating DLIST, and it reached up to 8.3° and 9.3° approximately after penetrating the third-layer and fourth-layer steel targets in the test of penetrating FLIST.
JUN-CHENG LI, CHUN-XIANG YU, HUI-MIN LI, YONG-GANG LU, LI-XIN QIAN
Behavior of the Pistol Ammunition Projectiles in Ballistic Gellatine
Following paper describes behaviour of different calibres and types of pistol ammunition bullets in ballistic gelatine, as a form of imitating their influence on human body. Tests includes comparison of widely available pistol ammunition in calibres 7,62x25 mm (FMJ steel jacket and PS – mild steel core), 9x19 mm (ACTION 4, FMJ, AP – brass monoblock) and newer small calibre pistol ammunition 4,6x30 mm (ACTION, FMJ DM-21) and 5,7x28 mm (SS195LF, SS197SR, SS190 duty round). During tests ballistic gelatine was protected by ballistic vest (protection level K2 according to Polish standard PN-V- 87000:2011) and different sets of aramide composite. Behaviour of bullet in ballistic gel was captured with use of Phantom v7.3 high speed camera. Bullet penetration depth and temporal cavity size were assessed with use of TEMA Motion software.
Experimental Research on HEL and Failure Properties of Alumina under Impact Loading
Research of Nose Shape Influence on the Projectile Attitude under the Oblique Penetration Condition
Take a series of scaled projectiles with the same quality, diameter, and different nose shape as the research objects, combined with numerical simulation and test of artillery, studied the influence of nose shapes to the projectile’s attitude changes in the process of oblique penetrating through a steel plate. In the process of research and analysis, the projectile’s axis rotation angle was the primary focus, the influence law of two main nose shape parameters: radius of curvature and truncated diameter were analyzed. The results show that, nose shape significantly affects the stress changes in the process of penetrating, causing obvious body attitude changes in direction and velocity; after penetrated target, the attack angle was increased with the curvature diameter ratio and decreases with the truncated diameter. Compared with sharp ogival nose projectile, truncated-ogival-nose projectile can reduce the axis rotation velocity, to ensure a well consistency body attitude fore-and-aft the penetration.
CHUN-XIANG YU, GONG-JIE NIU, SHOU-QIAN WANG, HUI-MIN LI
The Effect of Transparent Ceramic Tiles Weak-Spots on the Ballistic Resistance of Transparent Armor
A comparative test was conducted on full-scale ballistic samples in order to evaluate changes in the ballistic resistance of ceramic-based transparent armor solutions in relation to structural features of their mosaic pattern. This study was done in cooperation with CeramTec-ETEC which supplied PERLUCOR® transparent spinel, and OSG which produced and tested the complete armor solutions. Transparent ceramic tiles were arranged in a seam mosaic-pattern and in a junction mosaic-pattern, and their results were compared with center of tile impacts performed under similar conditions. A total of 42 ballistic samples were tested according to the multi-hit requirements of ATPD-2352T Protection Class 3a. The general outcome of this study is that ceramic tiles’ weak-spots reduce overall ballistic performance, and that the mosaic pattern as well as the tile size should be designed according to the multi-hit shot-spacing to minimize these effects.
ELI SAFRAI, ELDAD SHEMER, LARS SCHENTTER, REAS HECHT, ZVIKA BAR
Anti-Trauma Pads based on Non-Newtonian Materials for Flexible Bulletproof Inserts
The aim of research was to develop a new kind of flexible anti-trauma pads (including non- Newtonian materials) for the lightweight bulletproof vests which could decrease the behind armour blunt trauma (BABT) more effectively than present solutions. In the study shear thickening fluid (STF) based on silica nanoparticles dispersed in liquid polypropylene glycol and silicone elastomer based on homogeneous methyl-phenyl-borosiloxane polymer composition were tested for their energy dissipation capability. Different variants of the anti- trauma pads with non-Newtonian materials were designed and investigated: high performance polyurethane foams filled with STF and foams produced with addition of STF. The anti-trauma pads in samples were placed between the aramid or ultra-high molecular weight polyethylene layers. For comparison there were also investigated analogical samples with the commercial anti-trauma pads. The scope of research included ballistic tests (the .44 Magnum SJHP bullet) of armour samples fixed to a box with a clay backing material.
The Use of Light Metal Alloys for Ultralight Multi-Layer Structures of Passive Armours
The paper contains information on light metal alloys of titanium, aluminium and magnesium selected for use in multilayer structures intended for the construction of passive armours. The selected alloys reach the following levels of the tensile strength: Ti alloys: 500÷1050MPa, Al alloys: 300÷600MPa, Mg alloys: 280÷340MPa. For these alloys, the parameter equally important as high strength is adequate ductility. Using the above mentioned light metal alloys, multilayer test materials were made. These materials also included special ceramics such as Al2O3, SiC, B4C polyethylene, laminates reinforced with glass fibres or aramid fabric. The results have proved an effective stopping of armour piercing projectiles of the 7.62mm and 14,5mm calibre assigned to resistance levels 2÷4 according to STANAG 4569 standard. For various levels of resistance, the weight of 1m2 of the multi-layer test material based on the examined light metals was up to 20kg for level 2, up to 65kg for level 3, and ~95kg for level 4..
Two-Channel Projectile Deceleration History Registration During Their High-Speed Motion with Erosion in Target
The study is a continuation of the works that have been presented at the Symposia since 25th ISB. This paper presents the results of application of the piezometric technologies in the area of multi-channel measurements for high-speed interaction of projectile with target. Results of simultaneous registration of projectile deceleration history in the axial and lateral direction are presented for the first time. Registration is carried out in the process of curvilinear motion of the projectile in the cavity to a complete stop after inclined impact at the target. Also for the first time presents the results of dual registration history acceleration of composite elements of the projectile. The registration was done during the movement of the projectile with erosion in the target following the impact with moving target at velocities up to 1.5 km/s. The range of detected values of accelerations (decelerations of the projectile during direct interaction with the target) shows its record high value in the number of published studies of the processes of terminal ballistics using the piezometry.
Numerical Study of the Trajectory Stability of Lateral-Abnormal Projectiles Penetrating Soil at Small Angles of Attack
Lateral-abnormal projectiles with different geometrical nose pin on the front of the penetrator are designed as soil penetrator. A comparative analysis of the twodimensional motion of the non-normal penetration of different lateral-abnormal projectiles into soil at small angles of attack (AOA) is carried out with Modified Integrated Force Law (MIFL) methods in which the stress algorithms are numerically integrated over the top and bottom surfaces of the projectile to determine the force and moment acting on the projectile based on the spherical cavity expansion theory. Critical conditions for the occurrences of the instability and the reverse of the lateralabnormal projectile trajectory are discussed. The proposed model in which the wake separation and reattachment between projectile body and target are taken into account is capable of predicting J-hook trajectory of the lateral-abnormal projectiles into soil at various small AOA and shows good agreement with the field test data.
The Influence of Armour PVD Coating on the Projectiles Ricochet Capability during the Inclined Impact
In the article the possibility to increase capability of the ricochet of armour-piercing projectiles by application of a thin layer on the frontal surface of the armour with the Physical Vapour Deposition (PVD) method was carried out. The armours were made of the ARMOX 500T steel plates and were placed at various angles of inclination in relation to the initial flight path of the impacting projectile. The aim was to find the angle of inclination of the armour at which the penetration process changes from perforation to ricochet. Seven types of surface layers made of high-strength materials such as Ti, TiN, Al2O3, CrN were analysed. Results showed that the ricochet capability of the plates with and without the PVD coating is similar but the mechanisms of projectile-armour interaction are different.
An Experimental and Numerical Study of Ballistic Performance of SFRC Structures
This contribution is concerned with the experimental and numerical study of ballistic performance of steel fiber reinforced concrete structures. For this purpose, three different types of panels, made of steel fiber reinforced concrete (SFRC), slurry-infiltrated concrete (SIFCON), and ceramic composite (CC), have been tested under high velocity impact of a rigid projectile. Explicit Finite Element analyses aiming at capturing the experimental residual velocities for the SFRC and SIFCON panels have also been conducted. It was found that the use of ceramic in a layered structure of SFRC and SIFCON mixtures improves the ballistic performance of SFRC structures.
MEHRAN GHASABEH, KAAN TOKSOY, GÃ–KÇE DARA, SERDAR GÃ–KTEPE, ÃSMAIL ÖZGÜR YAMAN
Comparative Analysis of X-Ray Experiment and Numerical Simulation of Soil Ballistic
The projectile in the process of penetrating into the soil is easy to generate ballistic instability phenomenon, which has considerable influence on the projectile penetration and damage. Therefore, it is necessary to analyze and study the motion law and ballistic characteristics of the projectile penetrating into soil. In this paper, the experiment method to obtain the ballistic information of the projectile penetrating into soil by the X-ray camera was established. The experiments obtained the images of the ballistic trajectory of the projectile penetrating soil and the images were analyzed. At the same time, the ballistic trajectory of the projectile with different departure angle was calculated by LS-DYNA. And the numerical simulation provided the posture and movement characteristics of the projectile penetrating into soil. The attitude and ballistic trajectory characteristics of the projectile obtained by the numerical simulation were in agreement with the experimental images and had high reliability.
LI-NA XU, HUA-LIANG CHEN, CHUN-QIAO PANG, GANG TAO
On Stability Loss of Rod Projectiles during Penetration
Experimental data on loss of dynamic stability or longitudinal bending of rod projectiles during penetration in targets is presented together with results of theoretical investigation. Experiments were carried out using methods of direct and reverse ballistic setup for the range of velocities 400…2000 m/s. Direct ballistic setup was used for rods with elongation up to 50, and reverse - up to 100. It was shown that loss of stability happens after a certain time following the impact. For example, in an experiment with impact velocity of 700 m/s, bending was seen 70 μs from the start of the impact. The region of stable penetration was defined by the criterion of maximal elongation, for which the rods are stable during the penetration. Critical elongation for which rods penetrated without stability loss was expressed as a function of impact velocity. The suggested model for rod projectile stability during penetration yields results consistent with experimental data.
V. S. KOZLOV, I. E. KHOREV, V. F. TOLKACHEV, V. B. SHUTALEV
The Effect of Triconic Nose Profiles on Kinetic Energy Penetration Into Concrete Targets
The efficiency of kinetic energy penetrators into concrete structures and targets is becoming an ever increasing area of interest as weapons are required to penetrate deeper into targets for similar impact conditions and masses. Nose shape and profile are two of the areas that can be changed to increase performance without affecting mass. Many papers have been published regarding nose shape but most have focused on ogival profiles. This paper looks at a triconic nose shape and the effect of the location of the conic intersections of the profile on penetration performance. This paper describes the penetration performance of projectiles with a normal impact velocity of 300m.s-1 using empirical formulae, analytical modelling and ballistic gas-gun experiments performed at the University of Cambridge.
Flash X-Ray Cinematography Analysis of Dwell and Penetration of Small Calibre Projectiles with Three Types of SiC Ceramics
In order to improve the performance of ceramic composite armor it is essential to know the mechanisms during each phase of the projectile/target interaction and their influence on the penetration resistance. Since the view on the crater zone and the tip of a projectile penetrating a ceramic is rapidly getting obscured by damaged material, a flash X-ray technique has to be applied in order to visualize projectile penetration. At EMI a flash X-ray imaging method has been developed, which provides up to eight flash radiographs in one experiment. A multi-anode 450 kV flash X-ray tube is utilized with this method. The radiation transmitted through the target is then detected on a fluorescent screen. The fluorescent screen converts the radiograph into an image in the visible wavelength range, which is photographed by means of a high-speed camera. This technique has been applied to visualize and analyze the penetration of 7.62 mm AP projectiles into three different types of SiC ceramics. Two commercial SiC grades and MICASIC (Metal Infiltrated Carbon derived SiC), a C-SiSiC ceramic developed by DLR, have been studied. The influences, not only of the ceramic but also the backing material, on dwell time and projectile erosion have been studied. Penetration curves have been determined and their relevance to the ballistic resistance is being discussed.
STEFFEN BAUER, STEFFEN WEBER, HEINER GEDON
The Ballistic of Fragment Penetration into Clay Soil
Trajectory of projectile penetrating the soil had many research. But because of the complexity and diversity of soil, the projectile will tumble and form a cavity. This will cause the instability of trajectory and other issues, which make it difficult to quantitatively analyze the mechanical properties of soil. In this paper, the theoretical calculation and analysis have been performed using the trajectory which is formed by the high-speed fragments penetrating clay. The results indicated that there is a critical velocity, which is close to the sound velocity of soil in this place. The ballistic is divided into two parts-the funnel pit and the normal perforation. These show that the penetration is divided into the high-speed section and low-speed section. And there are two different drag coefficients. Cavity effect exists in the high speed penetration section, and the cavity resistance has a nonlinear relationship with the size of cavity.
LINA XU, HAULIANG CHEN, BAOXIANG REN, GANG TAO
Relation between Material Property and Dwell-to-Penetration Transition Velocity for SiC Ceramics
For SiC ceramic armours impacted by long rod projectiles, increasing the dwell-topenetration transition velocity of the ceramics can significantly improve its ballistic performance. An analytical model is derived to investigate how the transition velocity together with the transition stress are affected by the ceramic property, prestress, and the presence of a buffer. The transition stress is determined from initiation of SiC failure beneath the impact surface meanwhile SiC failure analysis is based on Hertz contact theory and pressure-dependent SiC strength. The relationship between the transition velocity and the transition stress for two types of contact stress distribution, i.e. uniform pressure and Hertz pressure, is derived from the Tate analysis. The predicted analytical model when compared against the experimental data from literature predicts transition velocities and stresses which are consistent. It is applied to analyse how the dwell-to-penetration transition velocity is increased by applying of radial prestress to the ceramic or placing of a buffer on the impact surface of the ceramic.
A Numerical Investigation on the Response of Thick Ultra-High Molecular Weight Polyethylene Composite to Ballistic Impact
A previously validated numerical model is used to computationally investigate the penetration of thick ultra-high molecular weight polyethylene (UHMW-PE) panels by fragment simulating projectiles. Penetration of such panels has been previously determined to occur in two stages: an initial localised penetration phase followed by a bulging phase during which failure occurs through membrane tension. In the bulging stage, UHMW-PE composite is able to exhibit large bulge deformation because mode II delamination occurs as a result of the transit of an initial pressure wave ahead of the projectile. The bulging stage is found to provide a significantly higher ballistic efficiency than the initial localised penetration stage. The transition between these two stages was found to occur where the release wave reflected from the panel rear surface interacts with the projectile.
Fragment-Simulating Impacts into Aluminum Plates
40 mm-thick AA7020-T651 (AlZn4.5Mg1, 3.4335) plates are tested during impacts with fragment-simulating projectiles accelerated to the impact velocity close to 1100 m/s. The penetrator/target interaction is verified based on impacts of not only standardized 20 mm fragment-simulating projectiles (FSPs) but also blunt, quasi-conical and hemi-spherical projectiles, since the projectile’s nose shape influences its perforation capacity. Depending on the nose shape, different failure modes are observed in the aluminum plates. Analysis of material deformations and changes in its microstructure is presented aiming to obtain better understating of ballistic properties of plates considered as thick (regarding the ratio of projectile diameter/plate thickness) under impact of artillery shell fragments.
Shaped Charge Jet Penetration of Concrete Walls Using Charges of Different Sizes
The influence of the size of shaped charges on the penetration and perforation behavior of low-density brittle walls is investigated in this work. An incremental computation procedure for wall penetration was proposed earlier in combination with the Fireman-Pugh technique to provide a rapid answer for the use in fast running engineering tools. Shaped charges with three different diameters have been studied experimentally and compared with the computed results. Size-independent penetration and perforation of targets can be determined, provided that the charges are dimensionally proportional and the materials used have identical properties. However the three charges which are considered in this investigation show some differences, in particular concerning the liner geometry and the presence of a wave shaper. Therefore additional parameters are needed to describe the jet characteristics. The jet tip velocity, the velocity difference between the jet elements after breakup and a specific breakup criterion provide a good description of the stretching jet to perform modeling of charges with different sizes and different designs. If wall perforation and residual penetration performance are investigated, a separate RHA- penetration-depth curve needs to be established experimentally for each charge type.
Combined Approach For Characterization of Shaped Charge Jet Penetration 2
This paper presents a combined approach for characterization of shaped charge jet penetration, that incorporates both hydrocode simulation and experimentally fitted analytical models. The implementation of the proposed approach is demonstrated based on a representative 45mm caliber shaped charge. The AUTODYN Eulerian solver, with a special simulation setup, is used to accurately derive the jet mass-velocity distribution, along with other relevant jet parameters. It is shown that based on this jet data, and using the "breakup distance" approximation, the jet particulation mechanism can be properly fitted. This calibrated jet data is then used for calculating the penetration cratering characteristics, i.e. the time-resolved penetration process and the final crater profiles. The calculated results are compared to experimental ones showing very good agreement.
Strength Matters: Which Strength of Dyneema® Fiber Composites to Use in Hydrocode Models?—A Discussion
Ballistic protective performance of fiber composites correlates highly with fiber tensile strength. The mechanical tensile properties of fibrous UHMWPE cross-ply armor like Dyneema® are a challenge to assess. The reason is the high stiffness and strength combined with low interlaminar shear strength and low friction coefficient. When evaluating the strength of a hard-pressed composite plate using the standard ISO or ASTM dogbone shapes and pneumatic grips an inverse relation of apparent strength to sample thickness is found. This is an artefact of the test not being able to load the whole cross section cooperatively. High quality fiber, yarn and flexible ply tests are possible exploiting the capstan principle. We report typical measurements and discuss which strength to use in hydrocode models.
The Effect of Projectile Nose Geometry on the Critical Velocity and Failure Mode of Yarns Subjected to Transverse Impact
The effect of projectile nose geometry on the resulting critical velocity and failure mechanism of high-performance yarn is explored during single yarn transverse impact. Kevlar® KM2 yarns have been shot with three different projectile nose geometries, namely 0.30-cal round, 0.30-cal fragment simulation projectiles (FSP), and razor blades, at velocities surrounding the critical velocity required to initiate immediate yarn failure. In efforts to negate effects of wave interaction, strains developed at the experimental critical velocities are compared to quasi-static experiments designed to promote similar geometric loading conditions to those created during transverse impact. Additionally, above said critical velocities, strikes with 18-mm flat disc projectiles have been performed in efforts to ascertain the location of yarn failure at the initial stages of impact using high-speed imaging.
Experimental Study about the Influence of Adhesive Stiffness to the Bonding Strengths of Adhesives for Ceramic/Metal Targets
Modern lightweight armor systems consist of different classes of materials. The use of adhesives is a common technique to combine the armor components. The knowledge of the adhesive influence on the behavior of the armor compound is important for armor design. To study this influence four different adhesives (high-strength till high-flexible) were studied. Two types of ballistic experiments were utilized to generate different loading conditions. With 7.62 mm armor piercing projectiles with an impact velocity of 940 m/s complete penetration of adhesively bonded 12 mm thick alumina aluminum targets occurred. In contrast targets consisting of alumina and steel showed no penetration of 7.62 round ball at 840 m/s. The elongation of the adhesive layer and the deformation of metallic backing and ceramic tiles were observed by means of a highspeed camera during the projectile/target interaction.
ELMAR STRASSBURGER, SABINE GREFEN, STEPHAN SCHAARE
Modified Alekseevskii-Tate Model for Rod Penetration of Porous Targets
The Alekseevskii-Tate (AT) model of long rod penetration is modified to treat compressibility in porous targets. Crushing of pores is modeled with a simple compaction model, as previously applied to steady-state jet penetration. The only difference from the AT equations is an added porosity term in the usual Bernoulli equation. The model is exercised for relatively soft targets, for which it is applicable to the hydrodynamic stage of penetration (at sufficient velocities), after which the slowed and eroded residual penetrator may continue to penetrate in a non-eroding mode (not treated here).
Caliber50 Baseline Study Terminal Ballistic Performance
Various evaluations were performed to baseline the terminal performance of .50 Cal Ammunition fielded by the US Military. These evaluations resulted in three distinct categories of performance; High performance Armor Piercing, General Armor Piercing, and General Ball. The sole member of the first category was the M903 Saboted Light Armor Penetrator (SLAP) cartridge due its superiority, when compared to all other cartridges, in penetrating hard targets at range. The General Armor Piercing category included the Mk211 Multi-Purpose Round, M8 Armor Piercing Incendiary (API), and Mk263 Armor Piercing cartridges. The final category, General Ball, consists of the M33 which was far less capable than other rounds. The study results provide an abundance of performance data that can serve as a basis to develop requirements for an improved family of caliber .50 ammunition as well as provide rational for reducing capability overlaps, bridging capability gaps, and eliminating or improving inferior performing products.
Back Face Deformation (BFD) Response Comparison between Km2 and Hb80 Flat Panels
A series of back face deformation (BFD) tests were conducted to characterize the ballistic response for both Ultra-High-Molecular-Weight Polyethylene (UHMWPE) and Kevlar flat panels impacted by steel spheres. Digital image correlation (DIC) was used to measure the dynamic back face deformation. Post-experiment computed tomography (CT) scans were conducted to characterize the failure of the composite panels. Similar BFD profiles and failure modes were observed for both UHMWPE and Kevlar panels. Numerical models were developed in LS-DYNA to study the ballistic response in both UHMWPE and Kevlar panels. Tied-contact with failure option was used between adjacent composite layers to simulate delamination failure. The time histories of BFD, delamination failure and depth of penetration are compared with the experimental data.
SIKHANDA S. SATAPATHY, LIONEL R. VARGAS-GONZALEZ
Grain Refinement and Phase Transformation in a Middle-Carbon Steel after Jet Penetration
The “blackâ€ layer near the crater surface of a middle-carbon steel target penetrated by a high speed copper jet was observed by SEM. Micro-hardness test showed that the “blackâ€ layer near the crater surface was much harder than the matrix. It almost reached to the untempered martensite phase microhardness. The microstructure features divided the penetrated middle-carbon steel into four layers from the crater surface to the matrix: needle-like martensite layer, austenite and ultra-fine grained(UFG) ferrite layer, plastic deformation layer and normal matrix. The phase transformation was caused by the high pressure introduced by the hypervelocity impact and plastic deformation. And the microstructure distribution has something relationship to the different pressure condition and deformation strain and strain-rate because the shock wave decays as it spreads to the deep. XRD patterns confirmed that there were new phases like austenite in the middle-carbon steel after jet penetration.
Consistent Constitutive Modeling of Metallic Target Penetration using Empirical, Analytical, and Numerical Penetration Models
Using the fit for L/D = 10 projectiles penetrating steel targets, an effective flow stress (EFS) for the target can be computed for any matched pair of experimental velocity and penetration data. The so-derived empirical EFS has previously been shown to have value in analytical analysis. For numerical analysis the EFS is taken to be the stress threshold in an elastic/perfectly plastic (Von Mises) strength model. The Johnson-Cook (JC) constitutive (strength) model, also used in numerical modeling, was taken as a baseline. The numerical analyses of L/D = 10 tungsten projectiles penetrating HzB,A steel targets using JC and Von Mises/EFS strength models matched Hohler-Stilp experimental data closely in the velocity range 1,000 to 2,000 m/s. Using the EFS in empirical, analytical, and numerical calculations yields consistent modeling of metallic target penetration.
Effects of Thickness and Thickness Ratio in Alumina-Aluminum Layered Structure on Ballistic Performance against Steel Core Projectile
The effects of the thickness and thickness ratio of a ceramic-metal composite on the ballistic performance against a small caliber round was investigated. Sets of alumina (AD85)- aluminum (AL5083) layered structures having different thicknesses and thickness ratios were designed. Ballistic tests using steel core projectiles were performed to obtain the V50 ballistic limit for each set. In addition, ballistic limits were estimated using Woodward’s analytical model and were compared with the test results. The test results show that the ballistic efficiency increased with increasing thickness of the alumina tile at constant aluminum plate thickness, while efficiency decreased with increasing thickness of the aluminum plate at constant alumina tile thickness. At constant areal density, the highest ballistic efficiency was obtained when the thickness ratio of the alumina tile/aluminum plate was 1.7, which was 15% higher than the lowest value. The computational analysis results exhibited good agreement with the test results.
A Comparison of Meshless-Particle Methods for High-Velocity Impact Computations
This article presents a comparison of three meshless-particles algorithms for high-velocity impact computations. Included are the Generalized Particle Algorithm (GPA), the Combined Particle-Element Method (CPEM), and the Nodal EFG (Element-Free Galerkin) method. Results are also presented for the automatic conversion of distorted elements into meshless particles. The conversion approaches allow for more accuracy and efficiency for the lower-strained elements, and the particles provide the capability to represent the highly distorted material. The various approaches are evaluated by comparing results to those of a finite-element cylinder impact run (which can be assumed to be an accurate baseline), and a complex projectile-target interaction example that includes contact, material failure and fragmentation (where an accurate baseline result is not known). There is generally agreement between the results of the different approaches, but there are also some noticeable differences.
Simulations of a Gold Rod into Borosilicate Glass Using Experimentally Determined Constitutive Constants
Simulations of reverse ballistic experiments of a gold rod into borosilicate glass [1] were never revisited using constitutive constants from independent, laboratory characterization experiments. Prior to comparing simulation results against the experimental results, the experimental data were re-analyzed under different assumptions. This provides some sense of the uncertainty in the experimental results. It is also demonstrated that the assumed equation of state for borosilicate glass can have a significant effect on the computational results. Finally, it is demonstrated that the simulations, where it is assumed that the gold rod penetrates failed material, reproduces the experimental results within the uncertainties of the experiments, except at low impact velocities where the details of glass failure, that is, the transition of intact to failed material, are important.
On the Ballistic Response of Rapidly-Prototyped Alumina
Production of ceramic armour solutions on-demand / in-theatre would have significant logistical and military advantages. However, such near net-shape manufacturing technology is relatively immature compared to conventional sintering of ceramics. Here, compressed gas-guns allowed investigation of the ballistic performance of a series of rapidly-prototyped (RP) alumina tiles of 97.2% of the density of Sintox FATM. Both forward- and reverseballistic experiments were undertaken. These experiments employed the depth-ofpenetration technique and flash X-ray as primary diagnostics respectively. Overall, the RP alumina was found to exhibit useful ballistic properties, successfully defeating steel-cored (AP) 7.62 × 39 mm BXN rounds at velocities of up-to c.a.850 m/s, while exhibiting comparable failure modes to conventionally sintered armour-grade Sintox FATM. The results from both sets of experiments were complimentary and clearly indicated the potential of such RP materials to play an active role in provision of real-world body armour solutions.
AMER HAMEED, DAVID WOOD, JULIE ROWLEY, KEVIN JAANSALU
Dynamic Jacket Removal and the ‘Bullets Journey’
On impact soft cored bullets are designed to deform. The interaction between core and jacket during the penetration process is of particular importance if bullet performance is to be optimised. A bullets jacket serves several core purposes: (1) engagement with rifling; (2) inertial confinement, and; (3) cushioning on impact. In the latter two cases the jacket is primarily acting to control the nature of the stress / shock loading within the round both on and post-impact. In order to further inform armour design, via both dynamic (flash X-ray) and post-mortem (microstructural and X-ray computer tomography) analysis of impact / penetration events and recovered targets, an attempt has been made to provide additional insight into the bullet penetration process and the influence of the jacket on the same.
G.J. APPLEBY-THOMAS, D.C. WOOD, A. HAMEED, I.G. CROUCH
Terminal Ballistics of 7.62 mm Armour Piercing Projectiles Against Spaced, Oblique RHA Plates
Spacing and obliquity, when used together, are known to provide one of the most weight efficient solutions for armor protection. Although this configuration has been widely used over almost 100 years there is little quantitative or design data for such systems. In the present study a series of tests were performed using a steel-cored 7.62mm bullet (DAG 7.62x51) against RHA plates of varying thicknesses, spacing and obliquity of the front plate. This work showed that front plate should be substantially thinner than the rear, a ratio of 0.48:1 gave the best results. The highest mass efficiency (2.00) was for a large spacing (400mm) but this could be reduced to 50mm with only a 17% reduction in ballistic efficiency if a slightly more oblique front plate was used.
Transverse Impact on S-2 Glass Yarns: Analysis of Crimp and Other Effects on the Critical and Transverse Wave Velocities
S-2 glass yarns were tested under transverse ballistic impact. A comparison of the glassfiber properties with other typical ballistic fibers (like Kevlar®, Dyneema®, and PBO) is very interesting. On one side they have “similarâ€ properties, i.e. glass fibers have high modulus and high strength. But glass-fibers are isotropic and, apparently, more brittle than polymer fibers: glass-fibers fail in bending at much lower angles. It is shown in this paper that state of the art yarn impact theories like the ones by Smith et al. and Walker and Chocron, which predict very accurately the transverse wave velocity on polymeric yarns, are missing two important components of the impact physics: first, both underestimate the velocity for glass yarns, and second, both overestimate greatly the critical velocity. In an effort to find the missing physics yarn crimp was incorporated to Walker’s theory and finite element simulations were performed. It is shown that the bending stiffness that comes with the isotropy of the glass-fibers is central in properly describing the transverse wave propagation. It is also shown that failure is still not completely understood but a mechanism is speculated in the paper.
JAMES D. WALKER, RORY P. BIGGER, CHARLES E., ERSON
Material Science behind the Development of a New, Shapeable, Boron Carbide, Armour Material
Over the past five years, a novel variant of boron carbide has been developed, and commercialised, for use in lightweight armours, especially in Hard Armour Plates (HAPs) for body armour systems, and up-armouring kits for helmets. Both six-shot and three-shot HAPs have been developed for protection against a comprehensive suite of high velocity rifle rounds. Extensive ballistic testing has demonstrated that this new variant performs as well as conventionally processed, more-costly, hot-pressed grades. The new boron carbide variant utilises a combination of Viscous Plastic Processing (VPP) and Pressureless Sintering (PS) and is capable of producing complex, 3D shapes in thin sections down to ~2.5mm in thickness. This paper describes some of the processing technologies and material science that have been used to develop this unique material. Importantly, the effects of bulk density, thickness variations, and HAP construction, on the ballistic performance of the finished product, are detailed.
JAMES SANDLIN, STUART THOMAS, AARON SEEBER
Evaluation of Held’s Criteria (V2D) vs. Penetration for a Small Shaped Charge Warhead
Rocket propelled and gun-launched grenades are a particular concern on the battlefield because of the severe reaction that occurs when a munition is impacted by a shaped charge jets. High-precision surrogates representing two groups of warheads were developed to provide repeatable results during Insensitive Munitions (IM) Shaped Charge Jet (SCJ) testing. The final results for the 81mm RPG surrogate, and the preliminary results for the 40mm gun-launched surrogate were previously reported at IBS. This paper describes the development and testing of a surrogate 40mm SC warhead and compares it to Held’s initiation criteria commonly called V2D. A combination of analytical and continuum hydrocode modeling was used to characterize the jets of the surrogate warheads, which were subsequently fired through aluminum stripper plates to erode jet mass and velocity to mimic the V2D of the actual threat.. Flash radiography was used to capture and evaluate the jets. Various thickness aluminum stripper plates were tested to determine the variation of V2D as a function of stripper plate thickness.
S. DEFISHER, G. STUNZENAS, E.L. BAKER, N. AL-SHEHAB
Impact Behavior of Carbon and Hybrid Carbon-Glass Laminates at Low Temperatures
Carbon fibre laminates and hybrid carbon/glass fibre laminates are used mainly in aerospace engineering and space vehicles. The structures made of this material may be subjected to different impacts when in service. The working conditions is far from being at room temperature, airplanes operates mainly at low exterior temperatures as -60ºC and space vehicles are exposed at even lower ones. This research project deals with the impact performance of different laminates. A hybrid glass/carbon-epoxy composite similar to those used by the most modern planes in the border of attack of the wings has been studied from room temperature to -60ºC. Additionally a carbon-epoxy composite has been studied in the same range of temperatures and even tested at -196ºC using liquid nitrogen as coolant. The laminates have been tested from room temperature to low ones under impact conditions using a gas gun, with 5.5 mm diameter steel spherical projectiles. After completion of tests, the extent of damage was measured by means of ultrasonic C-scan inspection. The ballistic curves and the drop velocity curves obtained from those tests show a marked influence of the temperature on the results. To study the possible damage introduced on the laminates due to its exposition at low temperatures, also a temperature cycle was applied to different laminates and tested afterwards at room temperature, showing that the temperature cycle does not damage the laminates. This result confirms that the impact results at low temperature shows the impact performance at different temperature, as the exposition at different temperatures does not affect the results. A Lambert-Jonas fit curve for the different laminates is presented. The ballistic limit at different temperatures has also been obtained, and its variation is formulated for the carbon laminates.
On the Selection of Tissue Simulants for Ballistic Testing
Tissue analogues employed for ballistic purposes are often monolithic in nature, e.g. ballistic gelatin and soap, etc. However, such constructs are not representative of real-world biological systems. Further, ethical considerations limit the ability to test with real-world tissues. This means that availability and understanding of accurate tissue simulants is of key importance. Here, the shock response of a wide range of ballistic simulants (ranging from dermal through to skeletal simulant materials) determined via plate-impact experiments are discussed, with a particular focus on the classification of the behaviour of differing simulants into groups that exhibit a similar response under high strain-rate loading. Resultant Hugoniot equation-of-state data (Us-up; P-v) provides appropriate feedstock materials data for future hydrocode simulation of ballistic impact events.
AMER HAMEED, BRIANNA FITZMAURICE, JONATHAN PAINTER, DAVID WOOD
Structural Integrity of a Medium Caliber Ogive Shaped Projectile During Concrete Penetration
Projectiles experience severe stress conditions during impact and subsequent penetration in concrete due to target resistance. Structural integrity of projectile needs to be maintained during penetration for ensuring the operation of fuzing/initiating mechanism as well as preventing any unintended initiation of explosive during impact or penetration. This paper presents a methodology to use Forrestal formulations to arrive at initial design of an ogive nosed penetrator. Forrestal formulae necessitate experiments to obtain total penetration. A methodology is presented in which total penetration obtained from Conventional Weapon formula has been used in Forrestal formulations to estimate the resistive force offered by the concrete target. This resistive force is used to estimate the axial stress condition of penetrating projectile. These formulations have been used to design a 14 kg ogive nosed penetrator impacting with 500 m/s velocity against concrete target having compressive strength of 35 MPa.
S. HARIKRISHNAN, K.K. KULHARE, K.P.S. MURTHY
Trajectory Instability of Deep Penetration of Projectile into Soil Targets
This paper studies the characteristics of the curvilinear motion and trajectory instability of a rigid projectile in deep penetration. In order to identify the influences of non-axisymmetrical disturbance, impact velocity and mass centre location on penetration trajectory, the curvilinear motion and instability of rigid projectiles with different mass centre locations are analysed. It is shown that both sudden (instable) and gradual (curvilinear) changes of the projectile trajectory may happen under certain conditions of projectile geometry, impact velocity and other attacking parameters. A criterion is introduced to determine the occurrence of trajectory instability. Two characteristic velocities are identified, i.e. (a) the critical impact velocity, beyond which trajectory instability happens, and (b) the characteristic convergent velocity, at which the projectile trajectory turns to straight line from the curvilinear motion. The two characteristic velocities are linearly dependent on the relative mass centre location and independent of disturbance and impact velocity.
Effect of Add-On Explosive Reactive Armor on EFP Penetration
Explosive reactive armor (ERA) can significantly disturb penetration ability of shaped charge, yet the effect on EFP is unclear. In this paper, EFP and ERA interaction model was built in AUTODYN-3D by Lagrange-Euler coupled solver; deformation of EFP and depth of penetration (DOP) to steel target were obtained. Effects of ERA layer thickness, Oblique angle α and HE of ERA detonation condition were investigated under various EFP hitting velocity v. The results show that deformation of EFP is more severe and DOP to target declines result from increase of ERA layer thickness and oblique angle respectively; relative DOP was only 35% when α=60° However, low hitting velocity with large oblique angle ) may lead to no interaction between EFP and rear plate of ERA, causing less severe deformation of EFP and, therefore, obscure decline of DOP. The results also show that DOP declines as well when HE is not detonated, but less than HE detonated condition. Experiments were performed to verify this investigation, and simulation results are in agreement with experiment results.
JIAN-WEI JIANG, JIA-YU MENG, JIAN-BIN MEN
On the Shock Response of an Ultra-High-Molecular-Weight Polyethylene Composite
The shock and release behaviour of Dyneema® HB50 has been investigated, using a single stage light gas gun with manganin pressure gauges The Dyneema® composite was investigated in the US-up and P-up regime for two different orientations (fibres parallel and perpendicular to the impact axis respectively) and compared to data in the literature. It was found that for Dyneema® HB50 orientation makes no difference to any of the investigated shock properties. It was noted that the pressure observed in the Dyneema® HB50 was elevated, in comparison to the Hugoniot, but agreed with the Hugoniot obtained previously for polyethylene. This shock pressure differed to that seen in the literature, leading to the conclusion that pressure is dependent on the composite used but not orientation.
GARETH APPLEBY-THOMAS, AMER HAMEED, COLIN ROBERSON
Phase Transformations in Glass Associated with Hyper-Velocity Impact and Implications in Constitutive Modeling
Impact Response of Advanced Transparent Materials
The demand for improved visibility in hostile environments requires materials with high transparency and superior impact resistance. Numerous materials satisfy the above requirements including transparent polymers (PMMA), polycrystalline glass ceramics (e.g., AlON, spinels, transparent Al2O3), single crystals sapphire, hardened glass, etc. In this study, an investigation into fracture behavior and fragmentation characteristics of three different classes of transparent materials, namely, single crystal sapphire, polycrystalline magnesium aluminate spinel, and amorphous strengthened glass with high residual surface compressive stress exceeding 1 GPa. The materials were examined to better understand the operative damage mechanisms during quasistatic and dynamic loading. Due to their inherently different structural features, the mechanisms of deformation under static and dynamic loads are vastly different. While high hardness has been considered as a dominant property that contributes to superior performance of any armor material, it is now recognized that it is not the only property that determines the resistance against an incoming projectile. A range of mechanisms including the tendency for mixed mode fracture, grain boundary shielding, and pulverization characteristics etc., act in favor of spinel, whereas propensity for fracture along preferred crystallographic planes contributes to inferior performance of sapphire. In the case of strengthened glass, large residual compressive stresses (up to 1 GPa) enable increased impact resistance. Finally, the energy dissipated in each of these failure modes is quantified to gain further insight into the mechanics of failure in these materials.
A Computational Parametric Study on Cookie-Cutter Projectiles
Reported are the results of a computational parametric study on cookie-cutter Explosively Formed Projectiles (EFP) as a low environmental impact Explosive Ordnance Disposal (EOD) method. Considering an anti-tank mine, the cookie-cutter has to generate a low order reaction of the explosive to minimize the collateral damage. Moreover it has to cut the casing body with a sufficient diameter for a boosted evacuation of the reaction products. Pointed out is the potential of a short and thin walled copper tubular projectile to fulfill the required terminal performance while hugely limiting the pressure into the explosive. The impact velocity should range between 1100 m/s and 1500 m/s. The inner diameter of the cookie-cutter should be large enough to limit overpressure by recombination of the shock waves. The performances achieved with cookie-cutter projectiles are compared, at constant mass, with classical EFP shapes, i.e. thimble shaped projectiles and hemispheric end cylinders.
A Scaling Technique to Predict Ballistic Limits
Robust scaling techniques can be effective tools in the design of armour systems. Existing scaling models have traditionally involved fits to broad datasets that can be used to map out significant parametric variations, such as projectile geometry, mass, and yaw. In the present study, a semi-analytical model is developed to scale residual velocity data for a given projectile penetrating Kevlar fabrics. The premise of the approach is to scale the energy absorbed by the target material according to a deviation from an inertial model of penetration. A scaling parameter, independent of the number of Kevlar layers, is defined as a function of incident velocity. Using this scaling parameter, data for a 16 grain fragment penetrating an 8-ply, 1,000-denier Kevlar 29 is used to predict the residual velocity curves for 16-, 18-, and 22-ply Kevlar. Predictions of the ballistic limit are found to lie within 10% of the experimentally-determined ballistic limit.
Steel-Confined SiC Armour against Oblique Penetration The Effect of Out-of-Plane Fiber Waviness on the Ballistic Performance of Ultra High Molecular Weight Polyethylene
A combined experimental and computational study was carried out to investigate bilayer buffer designs to enhance ballistic performance of steel-confined SiC ceramic armour modules under oblique impact. Tungsten alloy long rods were experimentally impacted against the armour modules with the bilayer buffers at a nominal velocity of 1.23 km/s and NATO 60 degrees obliquity. The bilayer buffers comprised a 2mm thick Ti alloy outer layer together with a weak inner layer made of different materials. It was found that using soft materials like graphite and PE-like polymer for the weak layer produced the best ballistic performance of the armour modules. Simulations were carried out using the AUTODYN hydrocode to illustrate the interactions between the armour modules and long rods. The hydrocode simulations, showed the bilayer buffers cushioned the dynamic load applied to the ceramics of the armour modules on rod impact, reducing the initial ceramic damage compared to a non-buffered armour module. In addition, the buffers with the weak layer made of soft material were further able to delay the onset of damage to the ceramics in the armours, maximizing the armour module’s efficiency.
The Effect of Out-of-Plane Fiber Waviness on the Ballistic Performance of Ultra High Molecular Weight Polyethylene(UHMWPE) Laminates
In this study, the effect of out-of-plane fiber waviness on ballistic performance of thin compliant laminates was investigated. Waviness varying from 2.46% to 32.27% was artificially induced into thin DSM Dyneema® HB50 laminates. Analogous to crimp in woven textiles, waviness is defined as the fraction of total arc length divided by the wavelength of the crimping. Several amplitudes and wavelengths of undulations were investigated. The ballistic limit of each sample against a 17 grain Fragment Simulating Projectile (FSP) was determined and high speed videography was used to track the longitudinal and transverse wave positions as a function of time. It was found that outof- plane fiber waviness had a significant deleterious effect on both the transverse wave velocity and the maximum energy absorption of the laminates before failure. It was found that small, high frequency undulations were more deleterious than large, low frequency undulations due to the increased number of wave reflections.
JONATHAN E. CYGANIK, TONY J. KAYHART, DAMIAN KUBIAK, ROBERT C. SYKES
Effect of 7.62mm Round Mass and Composite Armor Areal Density on Clay Backface Deformation and Clay Internal Pressure
A series of tests were conducted to measure the backface deformation (BFD) and associated peak pressures in clay due to non-perforating 7.62mm projectile impacts on composite body armor test panels. The range of rounds tested had no significant effect on the clay BFD. However, the different rounds had a statistically significant effect on the peak pressures measured. In contrast, for the range of armor areal densities measured, the areal density had a statistically significant effect on the clay BFD but did not have a statistically significant effect on the peak pressure measured. This difference between clay BFD and internal pressure response suggests that the clay BFD and peak pressure measure different characteristics of the impact event.
QUANG T. LUONG, VIRGINIA A. HALLS, JAMES Q. ZHENG
Polymorphic Activity Generated in Soda-Lime Glass at Hyper-Velocity Impact
Polymorphic transformations are key in assessing the unusual response of glassy materials to hyper-velocity particle impacts. Examination of soda-lime glass impacted under hyper-velocity conditions indicates formation of Stishovite, a high-density polymorph and formation of other more common crystalline silica phases, a-quartz and b-crystobalite. These findings along with molecular dynamic computer analysis support further understanding of these interactions for compounding new glass chemistries and predicting performance against a wider variety of impactors. These findings can also help elucidate interpretations of meteoric minerals that may have been vitrified in reaching the earth or evaluation of other recovered space materials in the future.
PHILIP J. DUDT, SYED QADRI, WILLIAM FERRANDO
Calculations of Impacts into Concrete Targets Using the Holmquist-Johnson-Cook Model
The Holmquist-Johnson-Cook (HJC) concrete model has been implemented in the EDEN hydrocode and applied in studies investigating the normal impacts of simple projectiles against finite thickness concrete barriers. The results of these calculations have been used to investigate how the loading on the projectile and the residual velocity varies as a function of the projectile speed and barrier thickness. Results from the simulations are compared against predictions from cavityexpansion theory based engineering models for projectile penetration, such as those due to Li and Chen, and Forrestal. Special attention is paid to the roles that release waves from the barrier’s back surface play in the process and further comparisons are made to investigate how well the extended model of Sjol and Teland is able to account for these effects. An empirically-derived release model is derived and applied to predict penetration data.
Numerical Simulation of High-Velocity Projectile Penetrating Into Concrete Target using FEM-GPH Adaptive Coupling Algorithm
The generalized smoothed particle hydrodynamics (GPH) method, an upgrade of smoothed particle hydrodynamics (SPH) method, can reflect the real state of failure materials more accurately by changing their volumes and shapes, not just by changing particle volume like SPH method. This paper briefly introduced the GPH method and the Impa3D program, and presented a numerical study on the simulation of high velocity projectile penetrating into concrete using FEM-GPH adaptive coupling algorithm. The simulation results indicate that the FEM-GPH adaptive coupling algorithm transform failure FEM elements into GPH particles which can continue to participate in the computation. Thus, it is a better way in showing the mass erosion and deformation of projectile nose as well as the generation and extension of target crack compared to FEM with erosion algorithm, although it doesn’t compute efficiently.
HAI-JUN WU, AI-GUO PI, WEN CHEN, FENG-LEI HUANG
Comparison of Penetrator Alloys for Armor-Piercing Ammunition
Armor-piercing (AP) ammunition, which is designed to penetrate armor, generally carries a hard penetrator within a copper jacket, similar to the jacket which surrounds lead in a conventional projectile. Upon impact on a hard target, the copper case is destroyed, but the penetrator continues its motion and penetrates the target. The most efficient AP ammunition are built with penetrators made from tungsten (very expensive) or depleted uranium (very polluting), and although we know that, in impact dynamanics, the kinetic energy of the projectile plays a fundamental role, we are trying to examine the possibility of using cheaper and cleaner materials.